Quality Control Manual On Concrete and Steel Bridge Structures

Improvement of Quality Management for Highway
and Bridge Construction and Maintenance
QUALITY CONTROL MANUAL ON

CONCRETE AND STEEL BRIDGE STRUCTURES
CHAPTER 1 CONCRETE STRUCTURES
1.1 GENERAL INFORMATION
Concrete comes from the word ‘concretus’ which means ‘growing together’, which is a concise
description of the binding of loose particles into a single mass. Concrete is the finished product of
mixing aggregates with cement and water together with the necessary manipulations of placing same
and observing curing requirements. The quality of concrete is largely dependent upon the quality of
the paste which is water and cement which binds the aggregate particles into a solid mass. For
successful results then, a proper proportion of the water to cement is essential.
Ordinarily, the absolute volume of cement constitutes between 7 to 14 percent that of water from
about 15 to 20 percent. Thus, something like 66 to 78 percent of the concrete is made up of the
aggregates. Since these aggregates constitutes such a large part of the concrete, utmost care in their
selection concerning qualities such as a good grading, strength, durability and freedom from injurious
materials is important.
The proper methods of handling and placing the fresh concrete contribute to the production of quality
concrete. Segregation of the coarse aggregate and improper tamping in placing the concrete into final
position are factors contributing to weak concrete.
Equally important to be considered in the production of quality concrete is proper curing. Neglect on
the part of concrete inspectors in the matter of proper curing especially within the first 72 hours after
concrete is placed, will impair the increase in strength, and the loss of strength suffered within this
period can in no way be recovered.
1.1.1 How Concrete is Made
Good quality concrete is made by mixing a carefully selected blend of hard aggregates with the right
quantity of cement and just enough water to permit a high level of compaction and hydration of the
cement. The water reacts with cement and the mass sets to dense and make it a strong materials.
1.1.2 Bridge
1.1.2.1 Bridge Definition
A bridge as defined in the DPWH BMS Manual is a structure carrying a load over a road, waterway or
other feature, with a clear span along the centerline between the inside faces of supports over 6.0
meters. A bridge may have an independent deck supported on separate piers and abutments, or may
have a deck constructed integral with the supports. A bridge is composed of span, pier and/or
abutment elements as shown in Figure 1-1. Each element has a standard set of defined attributes
that cover all the features of the element in general terms. The defined attributes of a bridge are
shown in Table 1-1.
Quality Control Manual on Concrete and Steel Bridge Structures -1-

Figure 1-1
Bridge Elements
SPAN
WINGWALL
OVERALL LENGTH (BACK TO BACK OF BACKWALL) LENGTH
SPAN LENGTH
NUMBER OF SPANS = 3
PIER ABUTMENT
Table 1-1 Bridge Elements and Attributes
Element Attribute Description
Span Deck The deck is the surface on which vehicle traffic and/or pedestrian move
Main members The structure supporting the span between the supports. The main members
are the girders in a girder bridge
Secondary The secondary members are any structural members transferring the loads to
members the deck to the main members. In a girder bridge where the deck is supported
(including other directly on the girders, there are no secondary structural members.
members)
Pier Main structure This is the visible structure of the pier that supports the superstructure.
Foundation The foundation is the structure that transfers the load of the bridge to the
underlying ground. In most cases the foundation may not be visible and can only
be assessed based on its performance. The foundation is assumed to be in a
good condition if there are no signs that the foundation is moving or other
distress.
Abutment Main structure This is the visible structure of the abutment that supports the superstructure and
approach road.
Foundation The foundation is the structure that transfers the load of the bridge and the
approach road to the underlying ground. In most cases the foundation may not
be visible and can only be assessed based on its performance. The foundation
is assumed to be in a good condition if there are no signs that the foundation is
moving or other distress.
Left wing wall Any additional wall on the left side of the bridge abutment to support the
approach road adjacent to the abutment. Some bridge may not have any wing
walls.
Right wing wall Any additional wall on the right side of the bridge abutment to support the
approach road adjacent to the abutment. Some bridge may not have any wing
walls.
(Source DPWH BMS)

1.1.2.2 Concrete Bridge
Concrete bridge is a bridge having elements and attributes mostly made of concrete. The following
figures show typical drawings of concrete bridges.
Figure 1-1a Span Types
Girder
Cantilever Girder
Slab

Figure 1-1b Pier Types
Wall Type
2-Column
Figure 1-1c Abutment Types
Elevation Section
Wall
Elevation Section
Pile Bent

1.1.3 Types of Concrete used for Bridge Structures
1.1.3.1 Plain Concrete
Plain Concrete is concrete without reinforcement or reinforced only for shrinkage or temperature
changes. Plain concrete is used in members in which stresses are almost entirely compressive such
as certain types of footings.
1.1.3.2 Reinforced Concrete
Reinforced Concrete as defined in the DPWH Design Guidelines Criteria and Standards is a
composite material which utilizes the concrete in resisting compression forces and some other
materials, usually steel bars or wires, to resist the tension forces.
1.1.3.3 Pre-stressed Concrete
Pre-stressed Concrete as defined in the DPWH Design Guidelines Criteria and Standards is concrete
in which effective internal stresses are induced deliberately by forces caused by the tensioned steel or
other means.
1.1.4 Some Concrete Applications Based on DPWH Items of Work
1. Item 311 - Portland Cement Concrete Pavement

2. Item 405 - Structural Concrete
3. Item 406 - Pre-stressed Concrete Structures
4. Item 407 - Concrete Structures
5. Item 505 - Riprap and Grouted Riprap
6. Item 506 - Stone Masonry
7. Item 507- Rubble Concrete
8. Item 510 - Concrete Slope Protection
1.1.5 Concrete Quality Control Parameters
1. Selection of Materials
2. Design of Concrete Mixtures
3. Sampling of Concrete
4. Testing of Concrete samples
5. Control in Placing Concrete
6. Curing of Concrete Samples
7. Protection of Concrete
1.2 MATERIALS REQUIREMENT
1.2.1 Portland Cement Type I (ASTM C 150/AASHTO M 85)
1.2.1.1 Portland Cement
Type I – Portland Cement Type IP – Portland Pozzolan Cement
Cement is a by-product of lime, silica, alumina and iron. The main component of cement is lime which
is around 60-65%

Composition of Portland Cement:
Clinker + Gypsum = Portland Cement
It shall conform to the applicable requirements of Item 700, Hydraulic Cement. Only Type I Portland
Cement shall be used unless otherwise provided for in the Special Provisions. Different brands or the
same brands from different mills shall not be mixed nor be mixed nor shall they be used alternately
unless the mix is approved by the Engineer. However, the use of Portland Pozzolan Cement Type IP
meeting the requirements of AASHTO M 240/ASTM C 695, Specifications for Blended Hydraulic
Cement shall be allowed, provided that trial mixes shall be done and that the mixes meet the concrete
strength requirements, the AASHTO/ASTM provisions pertinent to the use of Portland Pozzolan Type
IP shall be adopted.
1.2.1.2 Blended Hydraulic Cement Type 1P (ASTM C 595)
Blended Hydraulic Cement – a hydraulic cement consisting of two or more inorganic constituents
(at least one of which is not Portland cement or cement clinker) which separately or in combination
contribute to strength gaining properties of the cement, (made with or without other constituents,
processing addition or functional additions, by inter-grinding or blending).
The most common materials used in blended cements are blast-furnace slag and fly ash. Natural
pozzolans and microsilica (silica fume) are other constituents in blended cements.
Pozzolan is a material that has little or no hydraulic activity of its own, but it acts as hydraulic cement
when mixed with water and CaO. In blended cement Portland cement is the source of CaO for
pozzolanic reactions (Ca(OH)2, it is produced when Portland cement hydrates. Pozzolans are high in
SiO2 and may contain significant amount of Al2O3.
Composition of Pozzolan
Welded tuff Fly Ash

Natural Pozzolan Artificial Pozzolan
1.2.1.3 Quality Control Tests on Cement
The following table lists the quality control tests on cement and their significance

Table 1-2
Quality Control Tests on Cement
Type of Test Significance
1. Density of Hydraulic Cement (AASHTO The value of specific gravity of cement is used in the design
T 133-86, ASTM C 188-84) and control of concrete mixtures
2. Fineness of Hydraulic Cement by the No. 200 This method is intended for the determination of the fineness
(0.075-mm) Sieves (ASTM C 117-80(1981) of Portland Cement, in terms of percentage passing No. 200
sieve.
3. Fineness of Hydraulic Cement (Type I And This method is intended for the determination of the fineness
Type IP) By Air Permeability Apparatus of Portland cement, in terms of the specific surface
(AASHTO T 153-86, ASTM C 204-84) expressed as total surface area in square centimeters per
gram, or square meters per kilogram of cement.
4. Normal Consistency of Hydraulic Cement This test determines the amount of water required to prepare
(AASHTO T 129-85, ASTM C 187-83) hydraulic cement pastes for testing.
5. Time of Setting of Hydraulic Cement by The purpose of this test method is to establish whether
Gillmore Needle (AASHTO T 154-82(1986), cement complies with a specification limit on setting time.
ASTM C 266-77) The time of setting is affected not only by the percentage and
the temperature of the water used, and the amount of
kneading the paste received, but also by the temperature and
humidity of the air.
6. Time Setting of Hydraulic Cement by Vicat This test determines the time of setting and normal
Needle (ASTM C 191-08) consistency of hydraulic cement
7. Soundness of Hydraulic Cement by Autoclave The autoclave expansion test provides an index of potential
Expansion (AASHTO T 107-86, ASTM C 151- delayed expansion caused by hydration of calcium oxide
84) (CaO) or Magnesium Oxide (MgO) or both.
8. Air Content of Hydraulic Cement The purpose of the test is to determine whether the hydraulic
(ASTM C 185-02) cement under test meets the air-entraining or non-air-
entraining requirements of the applicable hydraulic cement
specification for which the test is being made.
9. Compressive Strength of Hydraulic Cement The purpose of the test is to determine whether the hydraulic
Mortars (Using 50mm Cube Specimens) cement under test meets the air-entraining or non-air-
(AASHTO T 106-86, ASTM C 109-84) entraining requirements of the applicable hydraulic cement
specification for which the test is being made.
10. Loss on Ignition (Hydraulic Cement) The loss is assumed to represent the total moisture and CO2
(ASTM C 114) in the cement
11. Insoluble Residue (Hydraulic Cement) The test determines the amount of insoluble residue of inert
(ASTM C 114-03) materials in hydraulic cement
12. Sulfur Trioxide Content The purpose of this test method is to estimate the SO3
(Hydraulic Cement) (ASTM C 563-07) content of hydraulic cement that gives maximum 24 hour
compressive strength.
13. Magnesium Oxide Content (Hydraulic The test estimates the MgO content of hydraulic cement and
Cement) (AASHTO T 105, ASTM C 114) test the time of setting of hydraulic cement

1.2.2 Concrete Aggregates
Characteristics of Concrete Aggregates
 Resistant to abrasion and degradation

 Resistant to disintegration by sulfates
 Particle shape and surface texture
 Grading
 Unit weight
 Specific Gravity
 Absorption and surface moisture
 Resistant to Alkali reactivity and volume change
1.2.2.1 Fine Aggregates
It shall consist of natural sand, stone screenings or other inert materials with similar characteristics, or
combinations thereof, having hard, strong and durable particles.
It shall not contain more than three (3) mass percent of material passing the 0.075 mm (no. 200 sieve)
by washing nor more than one (1) mass percent each of clay lumps or shale.
If the fine aggregate is subjected to five (5) cycles of the sodium sulfate soundness test, the weighted
loss shall not exceed 10 mass percent.
The fine aggregate shall be free from injurious amounts of organic impurities. If subjected to the
colorimatic test for organic impurities and a color darker than the standard is produced, it shall be
rejected. However, when tested for the effect of organic impurities of strength of mortar by AASHTO T
71, the fine aggregate may be used if the relative strength at 7 and 28 days is not less then 95 mass
percent.
The fine aggregate shall be well-graded from coarse to fine and shall conform to the table below.
Table 1-3
Grading Requirements for Fine Aggregates
Sieve Mass Percent Passing
9.5 mm (3/8 in) 100

4.75 mm (No.4) 95-100
2.36 mm (No.8) -
1.18 mm (No.16) 45-80
0.600 mm (No.30) -
0.300 mm (No.50) 5-30
0.150 mm (No.100) 0-10
0.075 mm (No. 200) 3 maximum
Sampling shall be done in accordance with AASHTO T 2 Standard Methods of sampling, stone, slag,
gravel, sand and stone block for the use as highway materials. Fine and coarse aggregates must be
laboratory tested and approved as to size and quality before use. Samples should be submitted to the
Regional/District Laboratories or private laboratories accredited by DPWH for quality tests,
accompanied by the sample card filled in detail. See Appendices I-2 & I-3. Size of samples shall be
referred to Memorandum Circular No. 28 Series of 1985 (Guidelines on Submission of Samples).

Laboratory trial mixes should be made on aggregates which are proposed to be used for the first time.
In such cases, samples of fine aggregates should weigh about 50 kg (Surface Dry) and about 70 kg
(Surface Dry) of coarse aggregate for one class of concrete. Each shipment for trial mix shall be
accompanied by the sample card filled out in detail. Frequent sieve analysis of the concrete
aggregates should be made in the field using AASHTO T 11 Standard Method of Test for amount of
materials finer than 0.075 mm sieve in aggregate and AASHTO T 27 Standard Method of Test for
sieve analysis of fine and coarse aggregates. At least one sieve analysis shall be made for each 75
m³ of aggregate, which shall be reported in standard form.
1.2.2.2 Coarse Aggregates
It shall consist of crushed stone, gravel, blast furnace slag, or other approved inert materials of similar
characteristics, or combinations thereof having hard, strong, durable pieces and free from any
adherent coatings.
*It shall contain not more than one (1) mass percent of material passing the 0.075 mm (No.200) sieve,
not more than 0.25 mass percent of clay lumps, nor more than 3.5 mass percent of soft fragments.
If the coarse aggregate is subjected to five (5) cycles of the sodium sulfate soundness test, the
weighted loss shall not exceed 12 mass percent.
It shall have a mass percent of wear not exceeding 40 when tested by AASHTO T 96.
3
If the slag is used, its density shall not be less than 1120 kg/m (70 lb/ft³). The gradation of the coarse
aggregate shall conform to the Grading Requirement for Coarse Aggregate illustrated below.
Only one grading specification shall be used from any one source.
Table 1-4
Grading Requirements for Coarse Aggregates
Standard Alternate Class Class Class Class Class

Mm U.S. A B C P Seal
Standard
63 2-1/2" 100
50 2" 100 95-100
37.5 1-1/2" 95-100 - 100
25 1" - 35-70 100 95-100
19 3/4" 35-70 - 100 - -
12.5 1/2" - 10-30 90-100 - 25-60
9.5 3/8" 10-30 - 40-70 20-55 -
4.75 No.4 0-5 0-5 0-15* 0-10* 0-10*
*0.075 No.200 0-1 0-1 0-1 0-1 0-1
It will also be necessary to make frequent determinations of free water in the aggregates in order that
adjustments can be made on design weights which are on a saturated surface dry basis, to get the
batch weight, and to insure that the maximum net water content is not exceeded. The percent of free
water may be determined by subtracting percent absorption from percent moisture content. See
AASHTO T 84 Standard Method of Test for Specific Gravity and Absorption of the Aggregates and
AASHTO T 85 Standard Method of Test for Specific Gravity and Absorption of Coarse Aggregates.
Particle size and maximum size of aggregates are important because of their effect on relative
proportions, workability, economy, porosity and shrinkage. Use of very fine sands is uneconomical
and use of very coarse sands results in coarse, unworkable mixes. The desirable range in fineness
modulus of the fine aggregate should be 2.50 to 3.00 and for uniform concrete, maintain established

fineness modulus to +0.10 variation. The maximum size of the aggregate that can be used will
depend on the size and shape of concrete members and the amount and distribution of reinforcing
steel. Aggregates should be clean and free of objectionable fines.
Figure 1-2
Examples of Concrete Aggregates
Sample of a well-graded coarse aggregate. Note

how the smaller pieces fit in among the larger
ones in the mixed aggregate
Sample of a well-graded sand. Particles vary

from fine to those just passing 4.75 mm sieve
Sample of sand which lacks larger particles.

More cement is required when sand is fine. This
is not a good sand
If the aggregate from one source does not meet grading specifications, blending with other
aggregates may be tried. Aggregates should be handled and stored to produce minimum segregation
of sizes in order to produce practically uniform concrete. The stockpile should be built up in layers of
uniform thickness, whether handled by truck, clamshell or conveyor, and not built up in high cone
shape piles which results in the segregation of the sizes. Also, in removing the aggregates from the
stockpile it should be done in approximately horizontal layers to minimize segregation.

1.2.2.3 Quality Control Tests on Concrete Aggregates
Table 1-5
Quality Control Tests on Concrete Aggregates
1. Sampling Aggregates Sampling is equally as important as the testing, and the sampler shall
(AASHTO T 2-84, ASTM D 75- use every precaution to obtain samples that will show the nature and
82) condition of the materials that they represent
2. Reducing Field Samples of Specifications for aggregates require sampling portions of the
Aggregates To Testing Size material for testing. Other factors being equal, larger samples will
(AASHTO T 248-83, ASTM C tend to be more representative of the total supply. These methods
702-80) provide for reducing the large sample obtained in the field to a
convenient size for conducting a number of tests to describe the
material and measure its quality in a manner that the smaller portion
is most likely to be a representation of the field sample, and thus of
the total supply.
3. Total Moisture Content of This test method determines moisture content of aggregates which is
Aggregate by Drying (AASHTO important in adjusting batch weights of concrete
T 255-83, ASTM C 566-78)
4. Moisture Content in Fine Convenient procedure or field or plant determination of moisture

Aggregate content of fine aggregate
(AASHTO T 142-81 (1986),
ASTM C 70-79)
5. Sieve Analysis of Fine and Grain size distribution is widely used in the classification and
Coarse Aggregates (DPWH identification of soils. It is an important criterion in the classification
Standard Spec’s 1988 Vol. II and identification of soils.
Highway, Bridges & Airports)
6. Unit Weight/Mass of Values of unit weight/mass are used in volumetric/ gravimetric

Aggregates [AASHTO T 19-80 calculations. In volumetric batching of concrete aggregates, the unit
(1986), ASTM C 29-78] weight/mass should be known to convert weight/mass into loose
volume.
7. Organic Impurities In Sands For The test determines the presence of injurious organic compounds in
Concrete [AASHTO T 21- natural sands which are to be used in cement mortar or concrete.
81(1986), ASTM C 40-79] The purpose of the test is to furnish a warning that further tests of the
sand are necessary before they are approved for use.
8. Effect Of Organic Impurities In a) This test method is of significance in making a final determination
Fine Aggregate on Strength of of the acceptability of fine aggregates with respect to the
Mortar [AASHTO T 71- requirements of AASHTO M 6 (Standard Specification for Fine
80(1986), ASTM C 87-69 Aggregate for Portland Cement Concrete) concerning organic
(19750] impurities
9. Soundness Test by the Use of The test determines the resistance of aggregates to disintegration by
Sodium or Magnesium Sulfate saturated solutions of sodium sulfate or magnesium sulfate. It also
(AASHTO T 104-86, ASTM C furnishes information helpful in evaluating soundness of aggregates
88-76) subject to weathering action. Exceptions may be made if aggregates
have exhibited satisfactory service in existing structures.

10. Mortar Strength Test This test method provides a means of determining the compressive
(ASTM C 780) strength of hydraulic cement and other mortars and results may be
used to determine compliance with specifications. Further, this test
method is referenced by numerous other specifications and test
methods. Caution must be exercised in using the results of this test
method to predict the strength of concrete.
11. Specific Gravity and Absorption a) Bulk specific gravity is the characteristic generally used in
of Fine and Coarse Aggregates calculation of the volume occupied by the aggregate in various
(AASHTO T 84-86, ASTM mixtures containing aggregate including Portland cement concrete,
C 128-79) (AASHTO T 85-85, bituminous concrete and other mixtures that are proportioned or
ASTM C 127-81) analyzed on an absolute volume basis.
b) Absorption values are used to calculate the change in the weight

of an aggregate due to water absorbed in the pore spaces within the
constituent particles, compacted to the dry condition, when it is
deemed that the aggregate has been in contact with water long
enough to satisfy most of the absorption potential.
12. Abrasion Test (AASHTO T 96- This test evaluates the structural strength of coarse aggregate. It
83, ASTM C 131-81) gives an indication of quality as determined by resistance to impact
and wear. The results do not automatically permit valid comparisons
to be made between sources distinctly different in origin, composition
or structure.
1.2.3. Water
1.2.3.1 Properties
If water to be used in concrete work is of unquestionable quality, a certificate or statement should be

submitted showing a source and suitability. If the water to be used is not clear and not suitable for
domestic use or there is indication of alkali or deleterious substance, a one-quart sample shall be
submitted in a clean container to the Regional Laboratory or to any accredited testing laboratory for
testing and approval before use.
If it contains quantities or substances that discolor it or make it smell or taste unusual or

objectionable, or cause suspicion, it shall not be used unless service records of concrete made with it
(or other information) indicated that it is not injurious to the quality, shall be subject to the acceptance
criteria as shown in Table 1-6 and Table 1-7 as designated by the purchaser.

Table 1-6
Acceptance Criteria for Questionable Water Supplies
___________________________________________________________
Limits
___________________________________________________________
Compressive strength, min.
Control at 7 days 90
Time of Setting Deviation from 1:00 earlier

from Control to 1:30 later
Time of Setting (Gillmore Test)

Initial No marked change
Final Set No more marked change
Appearance Clear
Color Colorless
Odor Odorless
Total Solids 500 parts/ million max
pH value 4.5 to 8.5
Table 1-7
Chemical Limitation for Wash Water
_______________________________________________________________
Limits
_______________________________________________________________
Chemical Requirements, Minimum

Concentration
Chloride as C1(-1) expressed
as a mass percent of cement
(-1)
when added to the C1
in the other components of the
concrete mixtures shall not
exceed the following levels:
1. Prestressed Concrete 0.06 percent

2. Conveniently reinforced concrete
in a moist environment and exposed
to chloride 0.10 percent
3.Conventionally reinforced concrete
in a moist environment but not
exposed to chloride 0.15 percent
4.Above ground building construction
where the concrete will stay dry No limit for corrosion
Sulfate as SO4, ppm A 3000

Alkalies as (Na2O + 0.658 K2O), ppm 600
Total Solids, ppm 50000
_____________________________________________________________________
A Wash water reused as mixing water in concrete may exceed the listed concentrations of sulfate if it can be shown
that the concentration calculated in the total mixing water, including mixing water on the aggregate and other
sources, does not exceed specified limits.

1.2.3.2 Quality Control Tests on Water
Water will be tested in accordance with, and shall meet the suggested requirements of AASHTO T 26.
Water known to be of potable quality may be used without test.
1.2.4 Admixtures
Admixtures - a material, other than water, aggregates and hydraulic cement (included blended
cement) that is used as an ingredient of concrete and is added to the batch in controlled amounts
immediately before or during mixing to produce some desired modification to the properties of the
concrete.
Air-entraining admixture shall conform to the requirements of AASHTO M 154.
Chemical admixtures, if specified or permitted, shall conform to the requirements of AASHTO M 194.
Fly Ash, if specified or permitted as a mineral admixture and as 20 % partial replacement of Portland
Cement in concrete mix shall conform to the requirements of ASTM C 618.
Admixtures should be added only to the concrete mix to produce some desired modifications to the
properties of concrete when necessary, but not as partial replacement of cement.
Chemical admixtures and Mineral admixtures used for concrete shall be of confirmed quality.
1.2.4.1 Types of Chemical Admixtures
Concrete chemical admixtures shall be classified as follows and shall conform the requirements of
AASHTO M 194.
a. Type A – Accelerating Admixtures
An admixture that accelerates the time of setting and early strength development of concrete.
b. Type B – Retarding Admixtures
Admixtures that delays the time of setting of concrete.
c. Type C – Water- Reducing Admixtures
An admixture that reduces the quantity of mixing water required to produce concrete of a given
consistency.
d. Type D – Water –Reducing High Range, Admixtures
An admixture that decreases the quantity of mixing water required to produce concrete of a
given consistency by 12 percent or greater.
e. Type E – Water – Reducing and Accelerating Admixtures
given consistency and hastens the time of setting and early strength development of concrete.
f. Type F – Water – Reducing and Retarding Admixtures
given consistency and delays the time of setting of concrete.

g. Type G – Water- Reducing, High Range, and Retarding Admixtures
given consistency of 12 percent or greater and delays the time of setting of concrete.
Table I-8
Physical Properties of Chemical Admixtures for Concrete
Physical Property Type Type B Type C Type D Type Type Type

B B
A E F G
Water Content percent of

control, maximum 95 - - 95 95 88 88
Time of setting,
allowable deviation from
control, hour
Initial: minimum - 1.0 1.0 1.0 1.0 - 1.0

later earlier later earlier later
Maximum 1.0 3.5 3.5 3.5 3.5 1.0 3.5 later

earlier later earlier later earlier earlier
nor 1.5 nor 1.5
later later
-
Final: Minimum - - 1.0 - 1.0 -
earlier earlier
3.5 later
Maximum 1.0 3.5 - 3.5 - 1.0
earlier later later earlier
nor 1.5 nor 1.5
later later
Compressive Strength,
percent of control
C
minimum: 125
125
1 day - - - - - 140 115
3 days 110 90 125 110 125 125 110
7days 110 90 100 110 110 115 100
28days 110 90 100 110 110 110 100
6 months 100 90 90 100 100 100
1 year 100 90 90 100 100 100
Flexural Strength,
percent of control, 110
C
minimum: 100
3 days 100 90 110 100 110 110 100
7 days 100 90 100 100 100 100
28 days 100 90 90 100 100 100
Length Change,
maximum shrinkage
(Alternative 135
D
Requirements) 0.010
Percent of control 135 135 135 135 135 135
Increase over Control 0.010 0.010 0.010 0.010 0.010 0.010 80
Relative durability factor
minimum 80 80 80 80 80 80
A
The values in the table include allowance for normal variation in test results. The object of the 90% compressive
strength for Type B admixture is to require a level of performance comparable to that of the reference concrete.

B
It is recommended that whenever practicable, tests may be made using cement, pozzolan, aggregates, air-entraining
admixture, and the mix proportions and batching sequence when used in non-air-entraining and air-entrained concrete
because the specific effects produced by chemical admixtures may vary with the properties and proportion of the
other ingredients in the concrete. For instance, types “F” and “G” admixtures may exhibit such higher water reduction
3
in concrete mixtures having higher cement factors than 307 ± 3 kg/m . Mixtures having a high range admixtures are
used to impart increased workability (15 cm to 20 cm slump), the effect may be of limited duration, reverting to the
original slump in 30 to may be of limited duration, reverting to the original slump in 30 to 60 min depending on factors
normally affecting rate of slump loss.
C
The compressive and flexural strength of the concrete containing the admixture under test shall not decrease with age.
The objective of this limit is to require that the compressive or flexural strength of the concrete containing the
admixture under test shall not decrease with age.
D
The percent of control limit applies when length change of control is 0.030% or greater; increase over control limit
applies when length change of control is less than 0.030%.
E
The requirement is applicable only when the admixture is to be used in air-entrained concrete.
1.2.4.2 Types of Mineral Admixtures
Mineral Admixtures should comply with the required specifications of AASHTO/ASTM and equivalent
JSCE standards after a thorough confirmation on the quality by testing with the following conditions
should be satisfied:
a. Fly ash, Silica fume , volcanic ash, Siliceous white clay , Diatomite- admixtures which pozzolanic activity
can be expected.
b. Ground granulated blast-furnace slag- admixtures which latent hydraulicity can be expected .
c. Expansive admixtures - those which causes expansion in hardening process .
d. Siliceous fine powder – admixtures which contribute in gaining high strength during autoclave curing .
e. Pigments admixtures – for coloring
f. Limestone powder admixtures – decreases material segregation and/or bleeding of concrete with high
flowability.
g. Miscellaneous Admixtures – admixtures for high strength , polymers, fillers and etc.
1.2.5 Reinforcing Steel
Among the materials of construction, steel is one of those most widely used. It combines such
characteristics as strength, fabricability, and cheapness. For concrete reinforcement, a number of
grades which may vary in behavior are used. The Department of Public Works and Highways
Standard Specification require the use of only the structural and intermediate grades, although
recent studies abroad tend to show that hard grade steel such as rail steels give satisfactory service
performance. Steel reinforcing is used primarily to control cracking of a concrete structure and to
maintain the structural integrity of the slab between transverse joints. Cracking of the slab will occur
even though steel is present, but the steel reinforcement prevents the progressive opening of these
cracks by holding the edges of the crack close together. The DPWH Standard Specifications call for
the use of billet steel bars. The steel for concrete reinforcement should have suitable chemical
composition and tensile and bending properties. The amount of phosphorous in steel is a critical
quantity since, while a small amount of small percentage (0.05 to 0.10%) the phosphorous causes
“cold shortness” a term applied to that characteristic of steel, which makes it brittle when cold.
Reinforcing steel shall conform to the requirements of the following specifications:
 Deformed Billet-Steel Bars for Concrete Reinforcement AASHTO M 31 (ASTM A 615)

 Deformed Steel Wire for Concrete Reinforcement AASHTO M 225 (ASTM A 496)
 Welded Steel Wire Fabric for Concrete Reinforcement AASHTO M 55 (ASTM A 185)
 Cold-Drawn Steel Wire for Concrete Reinforcement AASHTO M 32 (ASTM A 82)
 Fabricated Steel Bar or Rod Mats for Concrete Reinforcement AASHTO M 54 (ASTM A 184)
 Welded deformed Steel Wire Fabric for Concrete Reinforcement AASHTO M 221 (ASTM A 497)
 Plastic Coated Dowel Bars AASHTO M 254 Type A
 Low Alloy Steel Deformed Bars for Concrete Reinforcement ASTM A 206

Dowels and tie bars shall conform to the requirements of AASHTO M 31 or M 42, except that rail steel
shall not be used for tie bars that are to be bent and re-straightened during construction . Tie bars
shall be deformed bars. Dowels shall be plain round bars. Before delivery to the site of work, one-half
of the length of each dowel shall be painted with one coat of approved lead or tar paint.
The sleeves for dowel bars shall be metal of approved design to cover 50 mm (2 inches), plus or
minus 5 mm (1/4 inch) of the dowel, with a closed end, and with a suitable stop to hold the end of the
sleeve at least 25 mm (1inch) from the end of the dowel. Sleeves shall be of such design that they do
not collapse during construction.
Plastic coated dowel bar conforming to AASHTO M 254 may be used.
1.2.5.1 Reinforcing Steel Bars
1) Properties
Reinforcing steel bars shall conform to the requirements of Item 404, Reinforcing Steel. Reinforcing
steel bars for concrete structures, except No. 2 bars shall be deformed in accordance with AASHTO
M 42, M 31, and M 53 for Nos. 3 through 11.
ASTM 615M is the standard specification for Deformed and Plain Billet –Steel Bars for concrete
reinforcement in cut lengths and coils. The standard sizes and dimensions of deformed bars and their
number designations are given in Table1-9. Bars are of three minimum yield levels such as Grade 40,
Grade 60 and Grade 75 are in Table 1-10.
Table 1-9 - Deformed Reinforcing Steel Bars
Bar Nominal Nominal Dimension Deformation Requirements (mm)

Designation Mass
Diameter Cross-
No.
(Kg/m) (mm) Sectional Perimeter Maximum Minimum Maximum
Area (mm2) (mm) Average Average Gap
Spacing Height
10 0.560 9.50 71 29.90 6.70 0.38 3.60
13 0.994 12.70 129 29.90 8.90 0.51 4.90
16 1.552 15.90 199 49.90 11.10 0.71 6.10
19 2.235 19.10 284 59.80 13.30 0.97 7.30
22 3.042 22.20 387 69.80 15.50 1.12 8.50
25 3.973 25.40 510 79.80 17.80 1.27 9.70
29 5.060 28.70 645 90.00 20.10 1.32 10.90
32 6.404 32.30 819 101.30 22.60 1.63 12.40
36 7.907 35.80 1006 112.50 25.10 1.88 13.70
43 11.380 43.00 1452 135.10 30.10 2.46 16.50
57 20.240 57.30 2581 180.10 40.10 2.59 21.90

Table 1-10 - Tensile Requirements

Grade 40 (280) Grade 60 (420) Grade 75 (520)
Tensile strength, min. Mpa 420 620 690

Yield strength, min. Mpa 280 420 520
Elongation in 203.2 mm, min. %
Bar Designation No
10 11 9 ....
13, 16 12 9 ....
19 12 9 7
22, 25 .... 8 7
29, 32, 36 .... 7 6
43, 57 .... 7
Table 1-11
Bend Test Requirements
Pin Diameter for Bend Tests A

Bar Designation No. Grade 40 Grade 60 Grade 75
(280) A (420) (520) B
10, 13, 16 3 1/2d B 3 1/2d B ....
19 5d 5d 5d
22, 25 5d 5d
29, 32, 36 7d 7d
43, 57 9d 9d
A Test bends 180 0 unless noted otherwise
B d = nominal diameter of specimen
2) Quality Control Tests on Reinforcing Steel Bars
The following tests shall be conducted to determine whether reinforcing steel bars meet the
specifications.
Table 1-12
Quality Control Tests on Reinforcing Steel Bars
1. Tensile Properties of The test determines the yield and tensile strength of steel bar as well
Reinforcing Steel Bars (ASTM as its elongation in order to classify the bars into grade.
A 709/A 709M-07)
2. Bending Properties of The test determines the ductile properties of the steel bar
Reinforcing Steel Bars (ASTM
A 709/A 709M-07)
3. Phosphorous in Steel Bar The test determines the phosphorous content of steel bar
(ASTM A 709/ A 709M-07)

1.2.5.2 Prestressing Reinforcing Steel
Prestressing is the process of subjecting steel or concrete to heavy internal stress in making or
casting to help withstand subsequent external loads or stresses. Concrete and structural steel are
prestressed by embedding steel wires or rods that are under tension.
The term Prestressing Reinforcing Steel shall conform to the requirements of the following
Specifications:
 High-tensile wire AASHTO M 204 (ASTM A 421)

 High-tensile wire strand or rope AASHTO M 203 (ASTM A 416)
High-tensile alloy bars are as follows :
High –tensile –strength alloy bars shall be cold stretched to a minimum of 895.7 MPa (30,000psi). The
resultant physical properties shall be as follows:
Minimum ultimate tensile 1000 MPa (145,000psi)

Strength followed by stress relieving
Minimum yield strength, 895.7 MPa (130,000 psi)

measured by the 0.7 percent
extension under load method
shall not be less than
Minimum Modulus of Elasticity 25,000,000
Minimum elongation in 20 bar 4 percent

Diameters after rupture
Diameters tolerance +0.762 mm -0.254mm

(+0.03”-0.01”)
1.2.5.2a Anchorages and Couplers
Structure and strength of anchorages and couplers shall be such that breakage and excessive
deformation is avoided before the applied tensile load reaches the values as may be specified for
anchoring or coupling prestressing steel.
1.2.5.2b Sheaths
Sheaths used shall be such that they are not deformed during handling and casting of concrete, and
also be capable of preventing any leaking-in paste through laps or joints.
The shape and size of sheaths shall be determined considering the procedures to insert the
prestressing steel, consistency of grout, the requirement of sufficient bond strength and its friction
against prestressing steels.
In cases when high levels of durability particularly against chloride induced corrosion is required, high
density polyethylene sheath should be used.
1.2.5.2c Protecting Duct
Protecting ducts for external cable structures shall be selected considering their ability to protect
tendons, and function as a duct for grouting anti-corrosive materials, specified strength/ durability, and
their erosion resistance performance.
1.2.5.2d Wire Rope or Wire Cable
The wire rope or wire cable made of twisted strands of wire shall conform to the requirements of
AASHTO M 30 for the specified diameter and strength class.

1.2.5.2e Grouting
Grouting machine should be positioned at one end of the girder. Ducts should be pumped with water
to remove dirt and other foreign materials . Ducts should be air blown afterwards to remove water.
Grout mix as determined from the trial mixes should be used. Water content should be kept in
minimum not exceeding 45% of the cement content to result in a flowing mixture.
Locations of anchorages at the end of each girder should be covered with mortar or concrete mix
before the grout is pumped. Flexible hose of 19mm diameter is provided for grout entry and exit.
Grouting should be carried out by inserting the hose at the grout entry of the girder, grout should be
continuously pumped until it comes out the designated exits, one at the other end and at the entry.
Grout should be free from air bubbles, consistent and uniform in texture. Composition of the grouting
material is as follows:
a. Cement : 3.0 kgs
b. Admixture (Intraplast Z) : 60.0 g
c. Water : 1.35 liter
d. Water-cement ratio : 45%
The following tests should be conducted prior to any grouting works:

2
a. Compressive Strength Test ……………..for every girder ≥20 N/mm
b. Consistency Test………………………….for every girder 6~12 sec
c. Breathing Test……………………………..for every girder ≤ 3%
d. Expansion Test…………………………....for every girder ≤ 10%
Using admixtures the grout used for prestressed concrete is required to maintain the required levels of
flowability and filling ability during grouting and to develop sufficient bond strength between the
tendons and sheath after hardening so as to achieve water tightness and protect the tendons.
Table 1-12a
Quality Control Tests on Prestressing Reinforcement
1. Determination of Tensile The test determines the yield and tensile strength of high tensile wire
Properties of Uncoated strand
Seven-wire Stress-relieved
Strand for Prestressed
Concrete (AASHTO M 203)
1.3 DESIGN OF CONCRETE MIXTURE
1.3.1 General
The design of a concrete mixture is the determination of the relative proportions of cement, fine
aggregates, coarse aggregate and water. The concrete mixture shall be designed to give the most
economical and practical combination of the materials that will produce the desired workability,
strength and durability. There are two methods that can be used in preparing the concrete mix,
design, namely: Standard Concrete Mix Design method and the ACI Concrete Mix Design method
1.3.2 Determination of Mass or Weight Proportions
Under the present DPWH Standard Specifications, concrete design is based on the fixed cement
content, using duly approved aggregates, water and maybe admixtures. The maximum net water
content and minimum strength requirements are specified.

It will be necessary for the Quality Control Engineer to determine prior to construction, by means of
trial mixes, the exact proportions by weight by each class of concrete. If the trial mix or batch is made
in the regional laboratory or any testing laboratory accredited by DPWH, representative samples of
the concrete materials which will be used in the work should be furnished. However, in some respects
it is preferable to run the trial batches right on the job, using the intended batch size during actual
construction, and the contractor’s regular batching and mixing equipment. By this procedure, there is
a better basis in judging workability because a laboratory batch is usually much smaller, hence, not
truly representative of working conditions. Samples are obtained from the trial batches to be tested for
strength in the Regional Laboratory or any private testing laboratory accredited by DPWH.
The first trial mix is selected on the basis of established relationships such as those given in Table 1-
13. This table, which have been developed from experience and data from several research agencies,
indicates the amount of water required per cubic meter of concrete and percent of sand (of total
aggregate by absolute volume) required for workability. The values in Table 1-13 are based on a mix
having a water-cement ratio of 0.57 by weight, 76.2 mm slump and natural sand having a fineness
modulus of 2.75. For other conditions it will be necessary to make certain changes in Table 1-13 in
accordance with the corrections or adjustments given below.
Based on mix having a water cement ratio of 0.57 by weight of 22.13 kg. per bag of cement, 75 mm
slump and natural sand having a fineness modulus of 2.75
For mixes having either proportions, see adjustment below :
Table 1-13
Approximate Sand and Water Contents for Concrete
Rounded Coarse Aggregate Angular Coarse Aggregate

Maximum
Size of Sand % of Total Net Water Content Sand % of Total Net Water Content
Aggregate, Aggregate by per m³ Aggregate by per m³
mm Absolute Volume, Absolute Volume,
Kg. Liters Kg. Liters
m³ m³
12.5 51 199 199 56 214 214
19 46 184 184 51 199 199
25 41 178 178 46 192 192
37.5 37 166 166 42 181 181
50 34 157 157 39 172 172
75 31 148 148 36 163 163
150 26 131 131 31 146 146
Table 1-13a
Table of Adjustments for Other Conditions
Effect in Values in Table 1-13

Changes in conditions stipulated in Table 1-13 Percent Sand Net Water Content
Each 0.05 increase or decrease on water cement ratio ±1 0
Each 0.1 increase or decrease in fineness modulus of sand ±1/2 0
Each 25 mm increase or decrease in slump 0 ±3%
Manufactured sand +3 +8..9 kg
For less workable concrete as pavement -3 -4.7 kg

Illustrative Example:
The following examples illustrate the necessary steps and calculations to determine the weight
proportions, using materials from a river located in Tarlac Province, for Class “A” Concrete. See Table
1-14 for completed work sheet on design of concrete. Calculations are shown after the table.
Table 1-14 Worksheet on Design of Concrete Mix
3
r
3
3
3
3 3
From Specifications:
Cement Factor……………………………………………… 9.00 bags/m3

Slump………………………………………………………...76.2 mm
Maximum size of Aggregates…………………………… 37.5 mm
Maximum Net Water Content …………………………… 21.20 L/bag
Minimum Compressive Strength ………………………….20.70 MPa at 28 days
From Preliminary Tests:
Bulk Specific Gravity of Fine Aggregates ……………… .2.65 (SSD)

Fineness Modulus ………………………………………….2.50
Bulk Specific Gravity of Coarse Aggregates ……………2.65 (SSD)

Maximum Size of Aggregates ……………………………..37.5 mm
Rounded Aggregate ……………………………………. Visual Inspection
Specific Gravity Type I Cement ……………………………3.15
Design Mix (Per Bag of Cement)
Absolute volume of concrete = 1 / (Cement Factor)
= 1/9
Absolute volume of Water

and cement = Water content Wt. of Cement
------------------------ + ---------------------
C.F. x 1000 S.G. x 1000
= 166 / (9 x 1000) + 40 / (3.15 x 1000)
= 0.0184 + 0.0127
3
= 0.0311 m
Absolute volume of
Total aggregate = 0.11 - 0.0311
= 0.0789 m3
Percent of fine aggregates = 37.00 (From Table 1-13)
Correction on Percent of Fine Aggregates
1. For water-cement ratio:
Water Cement = 166 (9 x 1000) = 0.46
Difference from standard = 0.57 - 0.46 = - 0.11
Correction = (-0.11 x 1%) / 0.05 = - 2.2%
2. For Fineness modulus of Sand:
Difference from standard = 2.75 - 2.50 = - 0.25%
Correction = (-0.25 x 0.5 %) / 0.1 = -1.25%

(From Table of Adjustment)
3. For Slump – None
Total Corrections = -2.2 - 1.25 = -3.45%
Corrected % of Fine Aggregates = 37 - 3.45 = 33.55
Absolute Volume of Fine Aggregate = Corrected % of FA x Absolute Volume of Aggregate
= 0.3355 x 0.0789 = 0.0265 m3

Absolute volume of Coarse Aggregate = Absolute Volume of Total Aggregate

- Absolute Volume of Fine Aggregate
= 0.0789 - 0.0265 = 0.0524 m3

Batch Weights:
Weight of FA = Absolute Volume x S.G. x 1000

= 0.0265 x 2.65 x 1000
= 70.23 kg
Weight of CA = Absolute Volume x S.G. x 1000

= 0.0265 x 2.65 x 1000
= 70.23 kg
Weight of Cement = Absolute Volume x S.G. x 1000

= 0.0127 x 3.15 x 1000
= 40 kg
Weight of Water = Absolute Volume x S.G. x 1000
= 0.0184 x 1.0 x 1000
= 18.4 kg
Note: Above weights are on saturated surface-dry (SSD) basis. Say the free water immediately prior
to mixing is 3% in the fine aggregate and -1% in the coarse aggregate. Therefore,
Corrected weight = Saturated Surface x (1 + Free Water)

of Fine Aggregate Dry Weight 100
= 70.23 x (1 + 0.03)
= 72.34 kg
Corrected Weight = 18.4 - [(72.34 – 70.23) + (137.47 – 138.86)]
of Water = 18.4 – 2.11 + 1.31
= 17.68kg
The starting trial mix is 72.34 kg fine aggregate, 137.47 kg coarse aggregate, and 17.68 kg of water
per bag of cement using the field condition of the aggregates.
Using the above weight, a trial batch is run, and it is found out that 20.45 kg of water must be added
to produce the required 75mm slump. The total weight of all materials used in the batch is then:
Cement (1 bag) ………………………………………….40 kg

Fine Aggregate……………………..……………… 72.34 kg
Coarse Aggregate ………………………………….137.47 kg
Water ……………………………………… …………20.45 kg
---------------
270.26 kg
By observation, this mix appears workable. It contains the optimum percentage of fine aggregate for
proper placing under the stipulated job conditions. The total free water on the batch is then calculated
as follows:
Free water in the fine aggregate………………………….. 2.11 kg

Water added………………………..…………………….. .20.45 kg
------------
22.56 kg
Water required for the absorption in CA……..… -1.39 kg

------------------
21.17kg or
21.17 L

The mix, therefore conforms to the requirements of the requirements of the Standard Specifications,
the maximum net water content allowed being 21.20 L per bag of cement.
The next operation will be to check the yield. The procedure is described in AASHTO Designation T-
121, calculation is as follows:
3
The measured weight per m of the concrete is found to be 2406 kg. Then,
Volume of Concrete Produced Total batch Weight

= --------------------------------------
Per bag of cement Unit Weight
= 270.26 / 2406
3
= 0.11 m
Cement Content = 1 / 0.11
= 9.09 bags/ m3
The starting trial mix has been checked in three ways; the workability is good, indicating that the FA-
CA ratio is about right; the net water content is within the allowable; and the allowable variation of 2
%. The mix can therefore, be used as the official mix of the project, subject only to necessary
adjustments during construction.
Adjustment of Trial Batch
Adjustments in the trial batch will sometimes have to be made due to the following:
1. Over or undersanded mix

2. Water content exceeds the maximum allowable
3. The cement content as determined by the yield test differs by 2.0 percent or more the
specified value.
Adjustment for Variation in Workability
If the first trial mix is either over or undersanded, it is obvious that the fine-coarse aggregate ratio is to
be adjusted until the optimum sand content consistent with the placing condition is obtained. Under
the Standard Specifications, where the cement factor is held constant, the uses of the lowest
percentage of sand consistent with workability will result in the highest quality concrete; this is due to
the fact that a reduction in fine-coarse aggregate ratio will result in reducing the water-cement ratio,
thereby increasing the strength.
As a rule, the yield is not appreciably affected by adjustment of the fine-coarse aggregate ratio,
provided the total weight of the aggregate is held constant. Two or three additional trials would be
sufficient, each varying the sand content by increments of one percent in the desired direction and
including a corresponding change in the coarse aggregate such that the total aggregate weight is
maintain. In case of adjustments necessitating additional sand, the water content should be checked
in order to be sure that the maximum allowable water has not been exceeded.
Adjustment for the Variations in Yield
If the yield test indicates that there is variation in the cement content by more than 2 %, adjustment in
the batch weight maybe made by decreasing or increasing the absolute volume of total aggregate by
an amount equal to the difference between volumes produced and calculated volume. Thus in, the
3 3
previous example suppose the measured unit weight is 2,326 kg/m instead of 2,406 kg/m , then
Volume per Bag = 270.26 /2326 = 0.1162 m3

3
Cement Content = 1 / 0.1162 = 8.61 bags/m
Variation in Cement Factor = 9.0 - 8.61 = 0.39
Volume per bag (9.0 bags/ m3) = 1/9 = 0.1111 m3

3
Therefore, the excess in volume is = 0.1162 - 0.1111 = 0.0051 m per bag of cement. The adjustment
is made by decreasing the absolute volume of the total aggregate by the same amount. The change
in total batch weight in kilogram of aggregate per bag of cement maybe approximately by multiplying
3
the volume difference in m3 by 2,650, which is the unit weight of rock in kg/m . Thus, in the previous
example, the approximate adjustment is made by decreasing the total weight of aggregate per bag of
cement by (2, 650 x 0.0051) kg or 13.51 kg. This adjustment is only approximate; however it is
sufficiently accurate to serve as a basis for the initial correction of batch weights to be checked further
by the yield test.
Adjustment for Excess Water Content
Under the present specifications, the maximum net water content of 5.6 gal per bag of cement will
rarely, if at all, be exceeded due to specified aggregate gradation. Excess water for proper workability
will be required if the aggregate are poorly graded, have poor particle shape or have an excess of flat
or such aggregates.
In case the maximum net water content is exceeded, adjustment can be made in the following
manner:
In the proceeding example, assume that 23.64 kg of water was added, instead of 20.45 kg to produce
the desired slump. The free water in the mix will be 23.64 + 2.11 - 1.40 = 24.35 kg or 24.35 L per
bag of cement, this exceeds the maximum net water content of 21.20 L/bag.
Total Batch Weights are as follows:
Cement = 40 kg
FA = 72.34 kg
Ca = 137.47 kg
Water = 23.64 kg
273.45 kg
Supposing the measured/ actual unit weight of the mix is 2,358/m, and then the volume of concrete
produced per bag will be:
3
Volume per bag batch = 273.45 / 2358 = 0.1160 m
Cement Content per m3 = 1 / 0.1160 = 8.6 bag/m3

3
Total Water Content per m = 8.6 x 6.44 = 55.38 gal
It is a fact that for a given combination of materials and for a given consistency, the total amount of
3
water required per m of concrete will be approximately the same, regardless of the cement content,
see Figure 1-3. The cement which will be required to produce concrete containing 21.20 L water per
bag of cement (maximum allowable) is determined by this proportion:
Required cement factor = 55.38 / 5.6 = 9.9 bags/m3
The batch weights in the adjusted mix are then determined by the redesigning the mix as previously
3
described, using the required cement factor of 9.9 instead of 9.0 bags/m .

Figure 1-3
Relation of Water to Number of Bag of Cement Per Cubic Meter
1.3.3 Design of Concrete Mixture by ACI Method
This section describes the procedures in the design of concrete mixture using the Standard Practice
for Selecting Proportions for Normal, Heavyweight, and Mass Concrete (ACI 211.1-81)
Selection of concrete proportion should be based on test data and experience with the materials
actually to be used. Where such background is limited or not available estimates given in this
recommended practice may be employed.
The following information on available materials will be useful:
 Sieve analysis of fine and coarse aggregates

 Unit weight of course aggregate
 Bulk specific gravities and absorption of aggregates
 Mixing water requirement of concrete developed from experience with available aggregates
 Relationships between strength and water cement ratio, or ratio of water to cement plus
pozzolan, for available combinations of cements, pozzolans if considered, and aggregates.
 Specific gravities of Portland cement and mineral admixtures, if used
 Optimum combination of coarse aggregate to meet the maximum density grading for mass
concrete .
Procedures:
 The procedures for selection of mix proportions given in this section is applicable to normal weight
concrete. Although the same basic data and procedures can be used in proportioning heavy
weight and mass concrete.

 Estimating the required batch weight for the concrete involves a sequence of logical,
straightforward steps which, in effect, fit the characteristics of the available materials into a
mixture suitable for the work. The question of suitability is frequently not left to the individuals
selecting the proportions. The job specifications may dictate some or all of the following:
- Maximum water-cement ratio

- Minimum cement content
- Air content
- Slump
- Maximum size aggregate
- Strength
- Other requirement relating to such things as strength over design, admixtures, and special
types of cement or aggregate.
 Regardless of whether the concrete characteristics are prescribed by the specifications or are left
to the individual selecting the proportions, establishment of batch weights per cubic yard of
concrete can be best accomplished in the following sequence:
Step 1 - Choice of Slump.
If slump is not specified ,a value appropriate for the work can be selected from Table 1-15. The
slump ranges shown apply when vibration is used to consolidate the concrete. Mixes of the stiffest
consistency that can be placed efficiently should be used.
Table 1-15
Recommended Slumps for Various Types of Concrete Construction
Slump, cm
Types of Construction Maximum Minimum
Reinforced foundation walls and footings 8 2

Plain footings, caissons, and substructure wall 8 2
Beams and reinforced walls 10 2
Building columns 10 2
Pavements and slabs 8 2
Mass concrete 8 2
Step 2 - Choice of Maximum Size of Aggregate.
Large maximum sizes of well graded aggregates have fewer voids than smaller sizes. Hence,
concrete with the larger sized aggregate require less mortar per unit volume of concrete. Generally,
the maximum size of aggregate should be the largest that is economically available and consistent
with dimensions of the structure. In no event should the maximum size exceed one-fifth of the
narrowest dimension between sides of forms, one-third the depth of slabs. Nor three-fourths of the
minimum clear spacing between individual reinforcing bars, bundles of bars, or pre-tensioning
strands. These limitations are sometimes waived if workability and methods of consolidation are such
that the concrete can be placed with out honeycomb or void. When high strength concrete is desired,
best results may be obtained with reduced maximum sizes of aggregate since these produce higher
strengths at a given water-cement ratio.

Step 3 - Estimation of Mixing Water and Air Content.
The quantity of water per unit volume of concrete required to produce a given slump is dependent on
the maximum size, particle shape and grading of the aggregates, and on the amount of entrained air.
It is not greatly affected by the quantity of cement. Table 1-16 provides estimates of required mixing
water for concretes made with various maximum sizes of aggregate, with and without entrainment.
Depending on aggregate texture and shape, mixing water and requirements may be somewhat above
or below the tabulated values, but they are sufficiently accurate for the first estimate. Such differences
in water demand are not necessarily reflected in strength since other compensating factors may be
involved. For example, a rounded and an angular course aggregate both well and similarly graded
and of good quality, can be expected to produce concrete of about the same compressive strength for
the same cement factor in spite of differences in water-cement ratio resulting from the different mixing
water requirements. Particle shape per se is not an indicator that an aggregate will be either above or
below average in its strength-producing capacity.
Table 1-16
Approximate Mixing Water and Air Content Requirements
for Different Slumps and Nominal Maximum Sizes of Aggregates
Water per kg/m³ of Concrete for Indicated

Nominal Maximum Sizes of Aggregate
Slump, cm 10* 12.5* 20* 25* 40* 50†* 70†‡ 150†‡
NON AIR- ENTRAINED CONCRETE
3 to 5 205 200 185 180 160 155 145 125
8 to 10 225 215 200 195 175 170 160 140
15 to 18 240 230 210 205 185 180 170 -
Approximate
amount of 3 2.5 2 1.5 1 0.5 0.3 0.2
entrapped air in
non-entrained
concrete, percent
AIR ENTRAINED CONCRETE
3 to 5 180 175 165 160 145 140 135 120
8 to 10 200 190 180 175 160 155 150 135
15 to 18 215 205 190 185 170 165 160 -
Recommended
average total air
content
Mild exposure 4.5 4.0 3.5 3.0 2.5 2.0 1.5**†† 1.0**††
Moderate 6.0 5.5 5.0 4.5 4.5 4.0 3.5**†† 3.0**††
exposure
Extreme 7.5 7.0 6.0 6.0 5.5 5.0 4.5**†† 4.0**††
exposure‡‡
* These quantities of mixing water are for use in computing cement factors for trial batches. They are maxima for
reasonably well-shaped angular coarse aggregates graded within limits of accepted specifications.
† The slump values for concrete containing aggregate larger than 40 cm are based on the slump test made after
removal of particles larger than 40 cm by wet screening.

These quantities of mixing water are for use in computing cement factors for trial batches when 70 cm to 150 cm
nominal maximum size aggregate is used. It is average for reasonably well-shaped coarse aggregates, well-
graded from coarse to fine.
‡ Additional recommendations for air content and necessary tolerances on air content for control in the field are
given in a number of ACI documents, including ACI 201, 345, 318, 301, and 302. ASTM 94 for ready mixed
concrete also gives air content limits. The requirem ents in other documents may not always agree exactly so in
proportioning concrete, consideration must be given in selecting an air content that will meet the needs of the job
and also meet the applicable specifications.
** For concrete containing large aggregates which will be wet screened over the 40 cm sieve prior to testing for air
content, the percentage of air expected in the 40 cm minus material should be as tabulated in the 40 cm column.
However, initial proportioning calculations should include the air content as a percent of the whole.
†† When using large aggregate in low cement factor concrete, air entrainment need not be detrimental to the
strength. In most cases mixing water requirem ent is reduced sufficiently to improve the water-cem ent ratio and
thus compensate for the strength reducing effect of entrained air concrete. Generally, therefore, for these large
maximum sizes of aggregates, air contents recommended for extrem e exposure should be considered even
though there may be little or no exposure to moisture and freezing.
‡‡ These values are based on the criteria that 9% is needed in the mortar phase of the concrete. If the mortar
volume will be substantially different from the determined in this recommended practice, it may be desirable to
calculate the needed air content by taking 9% of the actual mortar volume.
Source : Standard Practice for Selecting proportions for Normal, Heavyweight, and Mass Concrete (ACI 211.1-81)
Table 1-16 indicates the approximate amount of entrapped air to be expected in non-air-entrained
concrete in the upper part of the table and shows the recommended average air content for air-
entrained concrete in the lower part of the table. If air entrainment is needed or desired, three levels of
air content are given for each aggregate size depending on the purpose of the entrained air and the
severity of exposure if entrained air is needed for durability:
3a. Mild Exposure – When air entrainment is desired for a beneficial effect other than durability, such
as to improve workability or cohesion or in low cement factor concrete to improve strength, air
contents lower than those needed for durability can be used. These exposure includes indoor or
outdoor service in a climate where concrete will not be exposed to freezing or deicing agents.
3b. Moderate Exposure – Service in a climate where freezing is expected but where the concrete will
not be continually exposed to moisture or free water for long periods prior to freezing and will not be
exposed to deicing agents or other aggressive chemicals. Examples include: exterior beams,
columns, walls, girders, or slabs which are not in contact with wet soil and are so located that they will
not receive direct applications of deicing salts.
3c. Severe Exposure – Concrete which is exposed to aggressive agents or where the concrete may
become highly saturated by continual contact with moisture or free water prior to freezing. Examples
include: pavements, bridge decks, curbs, gutters, sidewalks, canal linings, or exterior water tanks or
sumps.
The use of normal amounts of air entrainment in concrete with a specified strength near or about
5000 psi (37.70MN/m2 ) may not be possible due to the fact that each added percent of air lowers the
maximum strength obtainable with a given combination of materials. In these cases the exposure to
water, deicing salts, and freezing temperatures should be carefully be evaluated. If a member is not
continually wet and will not be exposed to deicing salts, lower air content values such as those given
in Table 1-16 for moderate exposure are appropriate even though the concrete is exposed to freezing
and thawing temperatures. However, for an exposure condition where the member maybe saturated
prior to freezing, the use of air entrainment should not be sacrificed for strength.

When trial batches are used to establish strength relationships or verify strength – producing
capability of a mixture, the least favorable combination of mixing water and air content should be
used. This is, the air content should be the maximum permitted or likely to occur, and the concrete
should be gauged to the highest permissible slump. This will avoid developing an over-optimistic
estimate of strength on the assumption that average rather than extreme conditions will prevail in the
field. For information on air content recommendations, see ACI 201, 301, and 302.
Step 4 - Selection of Water Cement Ratio
The required water cement ratio is determined not only by strength requirements but also by factors
such as durability and finishing properties. Since different aggregates and cements generally produce
different strengths at the same water cement ratio, it is highly desirable to have or develop the
relationship between strength and water cement ratio for the materials actually to be used. In the
absence of such data, approximate and relatively conservative values for concrete containing Type I
Portland Cement can be taken from Table 1-17. With typical materials, the tabulated water cement
ratios should produce the strengths shown, based on 28-day test of specimens cured under standard
laboratory conditions. The average strength selected must, of course, exceed the specified strength
by a sufficient margin to keep the number of low tests within specified limits.*
Table 1-17
Relationship Between Water-Cement Ratio and Compressive Strength of Concrete
Water-Cement Ratio by Weight

Compressive Strength at
2
28 Days Kg f/cm * Non-Air-entrained Concrete Air-entrained Concrete
450 (44.13 MPa) 0.38 -

400 (39.23 MPa) 0.43 -
350 (34.32 MPa) 0.48 0.40
300 (29.42 MPa) 0.55 0.46
250 (24.52 MPa) 0.62 0.53
200 (19.61 MPa) 0.70 0.61
150 (14.71 MPa) 0.80 0.71
* Values are estimated average strengths for containing not more than the percentage of air shown in Table I-15. For water-
cement ratio, the strength of concrete is reduced as the air content is increased.
Strength is based on 15 x 30 cm cylinders moist-cured 28 days at 23± 1.7C in accordance with section 9(b) of ASTM C31 for
Making and Curing Concrete Compression and Flexure Test Specimens in the Field. Cube strengths will be higher by
approximately 20 percent.
Relationship assumes maximum size of aggregate about 20 to 30 mm; for a given source, strength produced by a given water-
cement ratio will increase maximum size decreases.
For severe conditions of exposure, the water cement ratio should be kept low even though strength
requirements may be met with a higher value. Table1- 18 gives limiting values.

Table 1-18
Maximum Permissible Water-Cement Ratios for Concrete in Severe Exposures (Metric)
Structure Wet
Continuously or Structure Exposed to
Type of Structure Frequently Seawater and Sulfates
and Exposed to
Freezing and
+
Thawing
Thin sections (railings, curbs, sills,
ledges, ornamental work) and 0.45 0.40
sections with less than3 cm cover steel
++
All other structures 0.50 0.45
* Based on the report of ACI Committee 201. "Durability of Concrete in Service", previously cited
+
If concrete should also be air-entrained
++
If sulfate-resisting Cement (Type II or Type V of ASTM C 150) is used, Permissible water-cem ent
ratio may be increased by 0.05.
When pozzolanic materials are used in concrete, a water to cement plus pozzolan ratio by weight
must be considered in place of the traditional water- cement ratio by weight. There are two
approaches normally used in determining the W/( C + P ) ratio which will be considered equivalent to
the W/C of a mixture containing only Portland cement: (1) equivalent weight of cementitious material,
or (2) equivalent absolute volume of cementitious material in the mixture. For the first approach, the
weight equivalency, the total weight of cementitious material remains the same ( that is W/( C + P ) =
W /C directly); but the total absolute volume of cement plus pozzolan will normally be slightly greater.
With the second approach, using the equation ( step 4.2), W / ( C + P ) ratio by weight is calculated
which maintains the same absolute volume relationship but which will reduce the total weight of
cementitious material since the specific gravity of pozzolans are normally less than that of cement.
The equations for converting a target water cement ratio W/C to a weight ratio of water to cement plus
pozzolan W/ ( C + P ) by (1) weight equivalency or (2) volume equivalency are as follows :
Eq. (Step 4.1) Weight Equivalency
____W_____
C+P weight ratio, weight equivalency = W/C
Where :
____W_______
C+P = Weight of water divided by weight of cement + pozzolan
W/C = target water cement ratio by weight
When the weight equivalency approach is used, the percentage of fraction of pozzolan used in the
cementitious material is usually expressed by weight. That is Fw, the pozzolan percentage by weight
of total cement plus pozzolan, expressed as a decimal factor is :
Fw = P/ (C + P )
Where :

Fw = pozzolan percentage by weight, expressed as a decimal factor
P = weight of pozzolanic material
C = weight of cement
( Note: if only the desired pozzolan percentage factor by absolute volume Fv, is known it can be
converted to Fw as follows )
Fw = 1 / [ 1 + (3.15 / Gp )((1/Fy ) – 1)]
Where :
Fv = pozzolan percentage by absolute volume of the total absolute volume of cement plus
pozzolan, expressed as a decimal factor
Gp = specific gravity of the pozzolan
3.15 = specific gravity of Portland cement (use actual value if known to be different)
Eq. ( Step 4.2 ) – Absolute Volume Equivalency
W/(C+P) weight ratio, absolute volume equivalency = (3.15) (W/C) / (3.15)(1-Fv) + (Gp)(Fv)
Where :
W/(C+P) = weight of water divided by weight of cement plus pozzolan
W/C = target water cement ratio by weight
3.15 = specific gravity of Portland cement (use actual value if known to be different)
Fv = pozzolan percentage by absolute volume of the total absolute volume of

cement plus pozzolan, expressed as a decimal factor.
Note: if only the desired pozzolan percentage by weight (Fw) is known, it can be converted to Fv as
follows :
Fv = [ 1 / ( 1+ (Gp/3.15)((1/Fw)-1)] , where these symbols are the same as defined above
Step 5 - Calculation of Cement Content
The amount of cement per unit volume of concrete is fixed by the determinations made in Step 3 and
4 above. The required cement is equal to the estimated mixing water content (Step 3) divided by the
water cement ratio ( step 4 ) . if however the specification includes a separate minimum limit on
cement in addition to requirements for strength and durability, the mixture must be based on
whichever criterion leads to the largest amount of cement.
The use of pozzolanic or chemical admixtures will affect properties of both the fresh and hardened
concrete.
Step 6 - Estimation of Coarse Aggregate Content
Aggregates of essentially the same maximum size and grading will produce concrete of satisfactory
workability when given volume of coarse aggregate, on a dry rodded basis, used per unit volume of
concrete. Appropriate values for the aggregate volume are given in Table 1-19, it can be seen that, for

equal workability, the volume of coarse aggregate in a unit volume of concrete is dependent only on
its maximum size and fineness modulus of the fine aggregate, differences in the amount of mortar
required for workability with different aggregates, due to differences in particle shape and grading, it is
compensated by the automatic differences in dry-rodded void content.
The volume of aggregate, in cubic feet, on a dry-rodded basis, for a cubic yard of concrete is equal to
the value on Table 1-19 multiplied by 27, this volume is converted to dry weight of coarse aggregate
required in a cubic yard of concrete by multiplying it by the dry-rodded weight per cubic foot on the
coarse aggregate.
Table 1-19
Volume of Coarse Aggregate Per Unit Volume of Concrete (Metric)
Volume of Dry-Rodded Coarse Aggregate * per Unit Volume of

Maximum Size Concrete
+
of Aggregate, for Different Fineness Moduli of Sand
mm 2.4 2.6 2.8 3.0
10 0.50 0.48 0.46 0.44
12.5 0.59 0.57 0.55 0.53
20 0.66 0.64 0.62 0.60
25 0.71 0.69 0.67 0.65
40 0.76 0.74 0.72 0.70
50 0.78 0.76 0.74 0.72
70 0.81 0.79 0.77 0.75
150 0.87 0.85 0.83 0.81
* Volumes are based on aggregates in dry-rodded condition as described in ASTM C 29 for Unit Weight of Aggregate
These volumes are selected from empirical relationships to produce concrete with a degree of workability suitable for
usual reinforced construction. For less workable concrete such as required for concrete pavement construction, they may be
increased about 10 percent. For more workable concrete such as may be increased about 10 percent. For more workable
concrete, such as may be required when placement is to be by pumping, they may be reduced up to 10 percent.
+ Fineness modulus of sand = sum of the ratios / 100 (cumulative) retained on sieve with square openings of 0.150, 0.300,
0.600, 1.18, 2.36, and 4.75 mm.
6.1 For more workable concrete, which is sometimes required when placement is by pump or
concrete must be worked around congested reinforcing steel, it may be desirable to reduce the
estimated coarse aggregate content determined using Table 1- 19 by up to 10 %. However caution
must be exercised to assure that the resulting slump, water cement ratio and strength properties of
the concrete are consistent with the recommendations in Sections 2B and meet the applicable project
specification requirements.
Step 7 - Estimation of Fine Aggregate Content
Completion of step 6, all ingredients of the concrete has been estimated except the fine aggregate,
it’s quantity is determined by the difference either of the two procedures that may be employed ; 7.1.
The “Weight Method”
7.1 If the weight of the concrete per unit volume is assumed or can be estimated from experience, the
required weight of fine aggregate is simply the difference between the weight of fresh concrete and
the total weight of the other ingredients. Often the unit weight of concretes is known with reasonable
accuracy from previous experience with the materials. In the absence of such information, Table 1-20
can be used to make a first estimate. Even the estimate of concrete weight per cubic meter is rough,
mixture proportions will be sufficiently accurate to permit easy adjustment on the basis of trial batches

as will be shown in the examples. If a theoretically fresh concrete weight per cubic meter is desired,
the following formula can be used.
U = 16.85 G (100-A) + C (1-G, /G,)-W (G,-1)
Where
U = weight of fresh concrete per cubic meter ,kg.
G = weighted average specific gravity of combined fine and course

Aggregate Bulk SSD*.
G = Specific gravity of cement (generally 3.15)
A = Air content, Percent
W = Mixing water requirement, kg per cu meter.
C = Cement requirement, kg per cu meter.
Table 1-20
First Estimate of Weight of Fresh Concrete
Maximum Size of Aggregate, First Estimate of Weight of Fresh Concrete (kg/m3)

mm Non-Air-entrained Concrete Air-entrained Concrete
10 2285 2190
12.5 2315 2235
20 2355 2280
25 2375 2315
40 2420 2355
50 2445 2375
70 2465 2400
150 2505 2435
3
Values calculated by Eq. (1) for concrete of medium richness 330 kg of cement per m and medium slump with
aggregate specific gravity of 2.7. Water requirem ents based on values for 8 to 10 cm slump in Table 1-16. If desired,
estimate of weight may be refined as follows if necessary information is available: for each 5 kg difference in mixing
water from Table 1-16 values for 8 to 10 cm slump, correct the weight per m3 kg in the opposite direction; for each 0.1
by which aggregate specific gravity deviates from 2.7, correct the concrete weight 70 kg in the same direction.
Step 8 - Adjustment for Aggregate Moisture
The aggregate quantities actually to be weighted out for the Concrete must allow for moisture in the
aggregates. Generally, the aggregate will be moist and their dry weights should be increased by the
percentage of water they contain, both absorbed and surface. The mixing water added to the batch
must be reduced by an amount equal to the free moisture contributed by the aggregate i.e., total
moisture minus absorption.
Step 9 - Trial Batch Adjustments
The calculated mixture proportions should be checked b y means of trial batches prepared and tested
in accordance with ASTM C 192,’ Making and Curing Concrete Compression and flexure test
Specimen in the laboratory,’ or full-sized field batches. Only sufficient water should be used to

produce the required slump regardless of the amount assumed in selecting the trial proportions. The
concrete should be checked for unit weight and yield (ASTM C 138) and for air content (ASTM C 138,
or C 231). It should also be4 carefully observed for proper workability, freedom from segregation, and
finishing properties. Appropriate adjustments should be made in the proportions for subsequence
batches in accordance with following procedure.
9.1 Re-estimate the required mixing water per cubic yard of concrete by multiplying the net mixing
water content of the trial batch by 27 and dividing the product by the yield of the trial batch in cubic
feet. If the slump of the trial batch was not correct, increase or decrease the re-estimated amount of
water by 10 lb for each required increase or decrease 1 in (25mm) slump.
9.2 If the desired air content (for air-entrained concrete) was not achieved, re-estimate the admixture
content required for proper air content and reduce or increase the mixing water content of paragraph
9.1 by 2.3 kg for each 1 percent by which the air content is to be increased or decreased from that of
the previous trial batch.
9.3. If estimated weight per cubic m of fresh concrete is the basis for proportioning, re-estimate that
weight by multiplying the unit weight in kg per cubic meter of the trial batch by 27 and reducing or
increasing the result by the anticipated percentage increase or decrease air content of the adjusted
batch from the first trial batch.
9.4 Calculate new batch weights starting with step 4, modifying the volume of course aggregate from
Table 1- 19 if necessary to provide proper workability.
Sample Computations:
The following conditions are assumed for the following Example:
1 Type I air - entraining cement will be used and its specific gravity is assumed to be 3.15
2 Coarse and fine aggregates in each case are of satisfactory quality and are graded within limits of
generally accepted specifications.
3 The coarse aggregate has a bulk specific gravity of 2.68 and absorption of 0.5 percent.
4 The fine aggregate has a bulk specific gravity of 2.64; absorption of 0.70 percent and fineness
modulus of 2.8
Example:
Concrete is required for a portion of a structure which will be below ground level in a location where it
will be not exposed to severe weathering or sulfate attack. Required average strength will be 250
2
kgf/cm with slump of 8 to 10 cm. the coarse aggregate has a maximum size of 40 mm and dry-
rodded weight of 1600 kg/m3.
Other properties of the ingredients are: 1) Cement – Type I non-air-entraining cement will be used
with specific gravity of 3.15; 2) Coarse and fine aggregates in each case are of satisfactory quality
and are graded within limits of generally accepted specifications; 3) Coarse Aggregates – bulk
specific gravity 2.68 and absorption 0.5 percent; 4) Fine Aggregates – bulk specific gravity 2.64,
absorption 0.7 percent, and fineness modulus 2.8.
All steps of Section 3 should be followed in sequence to avoid confusion, even though they
sometimes merely restate information already given.
Step 1. The slump required to be 8 to 10 cm.
Step 2. The aggregate to be used has a maximum size of 40mm.

Step 3. The concrete will be non-air-entrained since the structure is not exposed to severe
weathering. From Table 1-17, the estimated mixing water for a slump of 8 to 10 cm is not air entrained
concrete made 40 mm aggregate is found to be 175 kg/m3.
2
Step 4. The water-cement ratio for non-air-entrained concrete with a strength of 250 kgf/cm is
found from table 1-16 to be 0.62.
Step 5. From the information developed in Steps 3 and 4, the required cement content is found to
3
be 175/0.62 = 282 kg/m .
Step 6. The quantity of coarse aggregate is estimated from Table 1-19. For the fine aggregate
having a fineness modulus of 2.8 and 40 mm maximum size of coarse aggregate, the table indicates
3
that 0.72 m of coarse aggregate, on dry-rodded basis, may be used in each cubic meter of concrete.
The required dry weight is, therefore 0.72 x 1600 =1152kg.
Step 7. With the quantities of water, cement and coarse aggregate established, the remaining
material comprising the cubic meter of concrete must consist of sand and whatever air will be
entrapped. The required sand may be determined on the basis of either weight or absolute volume as
shown below:
7.1 Weight Basis. From Table1-20, the weight of a cubic meter of non-air-entrained concrete made
with aggregate having a maximum size of 40 mm is estimated to be 2420 kg. (For the first trial batch,
exact adjustments of this value for usual differences in slump, cement factor, and aggregate specific
gravity are not critical.) Weights already known are:
Water (net mixing) 175kg

Cement 282kg
Coarse aggregate 1152kg
Total 1609kg
The weight of sand, therefore, is estimated to be
2420 – 11609 = 8111 kg
7.2 Absolute Volume Basis. With the quantities of cement, water, and coarse aggregate established,
and the approximate entrapped air content (as opposed to purposely entrained air) of 1 percent
determined from Table 1-16, the sand content can be calculated as follows:
Volume of water = 175 / 1000 = 0.175 m3
Solid volume of = 282 = 0.090 m3

cement 3.15 x 1000
Solid volume of' = 1152 = 0.430 m3

coarse aggregate 2.68 x 1000
Volume of = 0.01 x 1.000 = 0.010 m3

entrapped air

Total solid volume 0.705 m3

of ingredients except
sand
Solid volume of = 1-0.075 = 0.295 m3

sand required
Required weight of = 0.295 x 2.64 x 1000 = 779 kg

dry sand
7.3 Batch weights per cubic meter of concrete calculated on the two bases are compared below:
Based on estimated Based on absolute

concrete weight, kg volume of ingredients
Water (net mixing) 175 175
Cement 282 282
Coarse aggregate (dry) 1152 1152
Sand (dry) 811 779
Step 8. Tests indicate total moisture of 2 percent in the coarse aggregate and 6 percent in the fine
aggregate. If the trial batch proportions based on assumed concrete weight are used, the adjusted
aggregate weights become
Coarse aggregate (wet) = 1152 (1.02) = 1175 kg
Fine aggregates (wet) = 811 (1.06) = 860 kg
Absorbed water does not become part of the mixing water and must be excluded from the adjustment
in added water. Thus, surface water contributed by the coarse aggregate amounts to 2.0 – 0.5 = 1.5
percent; by the fine aggregate 6.0 – 0.7 = 5.3 percent. The estimated requirement for added water,
therefore, becomes
175 – 1152 (0.015) – 811 (0.053) = 115 kg
The estimated batch weights for a meter of concrete are:
Water (to be added) 115 kg

Cement 282 kg
Coarse aggregate (wet) 1175 kg
Fine aggregate (wet) 860 kg
Total 2432 kg
Step 9. For the laboratory trial batch, it is found convenient to scale the weights down to produce 0.02
m3 of concrete. Although the calculated quantity of water to be added the desired 8 to 10 cm slump is
2.70 kg. The batch as mixed, therefore, consists of
Water (added) 2.70 kg

Cement 5.64 kg
Coarse aggregate (wet) 23.50 kg
Fine aggregate (wet) 17.20 kg
Total 49.04 kg

The concrete has a measured slump of 5 cm and unit weight of 2390 kg/m3. It is judged to be
satisfactory from the standpoint of workability and finishing properties. To provide proper yield and
other characteristics for future batches, the following adjustments are made:
9.1 Since the yield of the trial batch was

3
49.04/2390 = 0.0205 m
and the mixing water content was 2.70 (added) + 0.34 (on coarse aggregate) + 0.86 (on fine
aggregate) = 3.90 kg, the mixing water required for a cubic meter of concrete with the same slump as
the trial batch should be
3.90/0.0205 = 190 kg
As indicated in 9.1, this amount must be increased another 8 kg to raise the slump from the measured
5 cm to the desired 8 to 10 cm range, bringing the total mixing water to 198 kg.
9.2 With the increased mixing water, additional cement will be required to provide the water-cement
ratio of 0.62. The new cement content becomes
198/0.62 = 319 kg
9.3 Since workability was found to be satisfactory, the quantity of coarse aggregate per unit volume of
concrete will be maintained the same as in the trial batch. The amount of coarse aggregate per cubic
meter becomes
23.50/0.0205 = 1,146 kg wet

which is
1146/1.02 = 1,124 kg dry
and
1124 x 1.005 = 1,130 kg SSD*
*Saturated Surface Dry
9.4 The new estimate for the weight of a cubic meter of concrete is the measured unit weight of 2,390
3
kg/m .
2390 - (198 + 319 + 1130) = 743 kg SSD
or 743/1.007 = 738 kg dry
The adjusted basic batch weights per cubic meter of concrete are
Water (net mixing) 198 kg

Cement 319 kg
Coarse aggregate (dry) 1124 kg
Fine aggregate (dry) 738 kg
Step 10. Adjustments of proportions determined on an absolute volume basis follow a procedure
similar to that just outlined. The steps will be given without detailed explanation.

3
10.1 Quantities used in the nominal 0.02 m batch are
Water (net mixing) 2.70 kg

Cement 5.64 kg
Coarse aggregate (dry) 23.50 kg
Fine aggregate (dry) 16.51 kg
Total 48.35 kg
Measured slump 5 cm; unit weight 2390 kg/m3; yield 48.35/2390 = 0.0202 m3; and correct workability.
10.2 Re-estimated water for same slump as trial batch:
(2.70 + 0.34 + 0.83)/0.0202 = 192 kg
Mixing water required for slump of 8 to 10 cm:
192 + 8 =200kg
10.3 Adjusted cement content for increased water:
200/0.62 = 232 kg
10.4 Adjusted coarse aggregate requirement:
23.50/0.0202 = 1163 kg wet or
1163/1.02 = 1140 kg dry
10.5 The volume of ingredients other than air in the original trial batch was:
3
Water 3.87/1000 = 0.0039 m
3
Cement 5.64 / 3.15 x 1000) = 0.0018 m
3
Coarse aggregate 23.04 / (2.68 x 1000) = 0.0086 m
3
Fine aggregate 15.28 / (2.64 x 1000) = 0.0059 m
3
Total 0.0200 m
3
Since the yield was also 0.0202 m , there was no air in the concrete detectable within the precision of
the unit weight test and significant figures of the calculations. With the proportions of all components
except fine aggregate established, the determination of adjusted cubic yard batch quantities can be
completed as follows:
3
Volume of water = 200/1000 = 0.200 m
3
Volume of cement = 323/(3.15 x 1000) = 0.103 m
Allowance for volume of air = 0.000 m3
3
Volume of coarse aggregate = 1140/(2.68 x 1000) = 0.425 m
3
Total volume exclusive of fine aggregate = 0.728 m
Volume of fine aggregate required = 1.000 – 0.728 = 0.272 m3
Weight of fine aggregate (dry basis) = 0.272 x 2.64 x 1000 = 718 kg
The adjusted basic batch weights per cubic meter of concrete then, are:
Water (net mixing) 200 kg

Cement 323 kg
Coarse aggregate 1140 kg
Fine aggregate 718 kg

These differ only slightly from those given in Paragraph 9.4 for the method of assumed concrete
weight. Further trials or experience might indicate small additional adjustments for either method.
1.4 PROPERTIES OF CONCRETE
1.4.1 Strength
1.4.1.1 General
Concrete, in order to be a useful construction product, must fulfill or meet a minimum strength
requirement for compression, flexure, shear and bond on the basis of intended use. Strength of
concrete is principally dependent on the water-cement ratio; see Figure I -3 and Figure I-4. In general,
factors that affect compressive strength also affect flexural strength, shear strength and bond.
However, flexural strength is influenced by the type of aggregate than compressive strength. For
several lean mixes, the strength of the mortar determines the flexural strength of the concrete, and for
rich mixes, the strength of the aggregate is the controlling factor. The compressive strength of the
concrete as well as it’s tensile, flexural and bond strengths, increases with age as long as the
moisture and temperature conditions are favorable for continued hydration of the cement see Figure I-
5. Rate of increase in strength is higher at high temperature than in low temperature. Concrete
continues to increase in strength as long as it is protected from drying.
This chart is for monitoring and general reference use only
Figure 1-4
Compressive Breaking Strength of Concrete at Various Ages
in Percent of 28-Day Compressive Breaking Strength
1.4.1.2 Classes and Uses of Concrete
Concrete can be made with wide variations in quality. Our standard specification includes several
classes of concrete which are selected on the basis of intended use. See Table I-21.

CLASS A: All superstructures and heavily reinforced substructures. For slabs, beams, girders,
arch ribs, box culvert, reinforced footings, precast piles and cribbing.
CLASS B: Footings, pedestals, massive pier shafts, pipe bedding, and gravity walls,
unreinforced or with only a small amount of reinforcement.
CLASS C: Thin reinforced sections, railings, and for filler in steel grid floors.
CLASS P: Pre-stressed concrete structures and members.
Seal: Concrete deposited in water
Table I-21
Composition and Strength of Concrete for Use in Structures
Designated Minimum
Size of Compressive
Minimum Maximum Consistency
Coarse Strength of 150
Cement Water - Range in
Class Aggregates, mm X 300 mm
Content Per Cement Ratio Slump mm
Square Concrete Cylinder
m3 Kg (bag*) Kg/Kg (inch)
Opening, Std. Specimen at 28
mm days MN/m 2(PSI)
A 360 (9.1) 0.53 50-100 37.5-4.75 20.7
(2-4) (1 1/2”-No.4) (3,000)
B 320(8.0) 0.58 50-100 50 ( 4.75) 16.5
(2-4) (2”-No.4) (2,400)
C 380 (9.5) 0.55 50-100 12.5-4.75 20.7
(2-4) (1/2”-No.4) (3,000)
P 440(11) 0.49 100max. 19-4.75 37.7
(4)max (3/4”-No.4) (5,000)
Seal 380 (9.5) 0.58 100-200 25 - 4.75 20.7
(4-8) (1”-No.4) (3,000)
*The measured cement content shall be within plus or minus 2 mass percent of the design cement content.
** Based on 40 kg/bag
Source: 2004 DPWH Standard Specifications
1.4.2 Workability
Workability is defined as the ease with which a uniform mass of freshly mixed concrete can be moved
without segregation into final position in which it is allowed to harden. The degree of workability
required is dependent on the type of construction and the methods of handling and placing to its final
position. The minimum degree of workability that will permit satisfactory placing of the concrete under
job conditions should be maintained at all times. Excess workability is undesirable from the stand
point of both strength and economy. Oversanded mixtures are very workable but require additional
mixing water, thus resulting in loss of strength. On the other hand, if the water-cement ratio is to be
maintained, additional cement is necessary which increases the cost.
A uniform concrete product must be the result produced by maintaining the minimum degree of
workability of the concrete in place. If an excessive amount of mixing water is used in the concrete,
the coarse aggregates and the larger sand grains settle down upon being rotted and the fine

aggregate particles and water rise to the top of the layer, resulting in a non-uniform, weak product
upon hardening.
Oversanded mixtures require more water in order to be workable, but making it so will only result in a
sacrifice in strength, good surface texture and water tightness.
Grading and maximum size of aggregate also affects workability. Fine or very coarse sands are
objectionable. The grading of coarse aggregate of a given maximum size may varies over a wide
range without appreciable effect on the cement requirement if the proportion of the aggregate is such
as to give good workability.
There is no accurate method or instrument to measure workability. The method commonly used is a
slump test. A new method is by the use of the ball penetration apparatus. These new tests are readily
made in the field and are good measures of consistency. However, they give a little indication of the
field conditions, the operator or inspector has to judge visually if the concrete is of the proper
workability for placing.
1.4.3 Durability
Durability of the concrete is important in order to be able to withstand deterioration due to exposure to
weathering action. Durability within the limitations of workability is a function of the water-cement ratio
(see Figure I-5). Most specifications for concrete exposed to weathering require that water-cement
ratio be 0.53 by weight. Design by weight should be used.
Another factor that adversely affects durability is that certain aggregates may contain reactive
materials, such as opal silica which react with the alkali in the cement and cause excessive expansion
of the concrete and such expansion cause cracks in the structure.
STRENGTH
W A TER-CEM ENT RATIO
Figure 1-5
Relationship of Water-Cement Ratio and Durability

1.4.4 Impermeability
Imperviousness is an essential requirement of concrete exposed to the weather. Concrete that does
not leak is made by causing a small amount of water and curing it well for a long period. With less
water used in the mixing, the concrete product can be made dense to contribute to water tightness.
The properties generally desired in concrete are workability while it is still fresh, and strength and
durability of the hardened concrete while in service.
1.4.5 Quality Control Tests on Concrete
To maintain desired properties of concrete, the following quality control tests shall be conducted:
Table 1-22
Quality Control Tests on Concrete
1. Slump of Concrete Mix The test determines the consistency and workability of freshly-mixed
(AASHTO T 119-82, ASTM concrete
C 143-78)
2. Air Content of Freshly Mixed This test method covers the determination of the air content of freshly
Concrete by Pressure Method mixed concrete. The test determines the air content of freshly mixed
(AASHTO T 152-86, ASTM exclusive of any air that may be inside voids with aggregate particles.
For this reason, it is applicable to concrete made with relatively dense
C 231-82)
aggregate particles and requires determination of the aggregate
correction factor.
This test method and Test Method C138 and C173 provide pressure,
gravimetric, and volumetric procedures, respectively, for determining
the air content of freshly mixed concrete. The pressure procedure of
this test method gives substantially the same air contents as the
other two test methods for concretes made with dense aggregate.
3. Air Content of Freshly Mixed This test covers the determination of the air content of freshly mixed
Concrete by Volumetric Method concrete. It measures the air contained in the mortar fraction of the
(AASHTO T 196-80 (1986), concrete, but is not affected by air that may be present inside porous
ASTM C 173-78) aggregate particles. Therefore, this is the appropriate test to
determine the air content of concretes containing lightweight
aggregates, air-cooled slag, and highly porous or vesicular natural
aggregates.
4. Weight Per Cubic Meter Yield The test determines the amount of air/voids entrained in concrete
and Air Content (Gravimetric) of
Concrete Mix (AASHTO T 121-
86, ASTM C 138-81)
5. Sampling and Curing of This method provides standard requirements for making, curing,
Concrete Test Specimens In protecting and transporting concrete test specimens under field
The Field (AASHTO T 23-86, conditions.
ASTM C 31-84)
6. Compressive Strength of The results of this test may be used as basis for quality control of
Cylindrical Concrete concrete proportioning, mixing and placing operations; determination
Specimens (AASHTO T 22-86, of compliance with specification; control of evaluating effectiveness of
ASTM C 39-83B, Rev.) admixtures and similar uses.

1.5 QUALITY CONTROL SUPERVISION ON CONCRETE STRUCTURES
1.5.1 General
Making good concrete requires the application of improved practices and techniques. It is recognized
that in addition to proper ingredients, a modern formula for successful concrete production would
include common sense, good judgment and vigilance. By sticking to the above rules, it is positive that
the resulting concrete shall not fail to give the service that can be expected.
It is the responsibility of those in charge of construction work to make sure that concrete is of uniform
good quality. The extra effort and care required to achieve this objective are small in relation to the
benefits. All that is required to achieve the best is an understanding of the basic principles of making
good concrete and close attention to the already proved practices during construction.
1.5.2 Control in Measurement of Materials
In order that uniform batches of concrete of proper proportion and consistency are to be produced, it
is essential that the weighing of all ingredients be carefully controlled.
Cement is placed in bags of the usual 40 kg net weight for convenience. If fractional bags of cement
are used they should be weighed for each batch. In using full bags, it will always be good to run a
weight check test every now and then to be sure that tampered bags are not used.
Dependable and accurate means for measuring the mixing water are essential. The equipment should
be tested and calibrated for accuracy every now and then for best results. The inspector should
develop a keen eye to readily distinguish the required consistency from the unsatisfactory, which
should be immediately remedied once it occurs. Volumetric measurement of aggregates, especially
sand, is not dependable. A small amount of moisture, which is nearly always present, causes the
aggregates to bulk.
The amount of bulking depends upon the moisture content and grading. The general practice is to
weigh the aggregates. The varying amounts of free moisture present in the aggregates particularly in
natural sand must be determined and corresponding corrections should be made on the batch
weights. Dependable and accurate weighing machines of capacities commensurate to the size of
the hob are necessary for best results. The inspector should every now and then test the accuracy of
the machine in order to place the same amount of aggregates in every batch of concrete.

Table I-23
Requirement of Materials
for Concrete Bridges & Road Projects
Reference
Material Test Item Specifications
Standard
Autoclave Expansion Not more than 0.8 AASHTO M-24
7-days compressive strength More than 19.0 MPa M-24
Cement Initial Setting Not less than 45 min and M-24
not more than 375 min
Sieve Analysis
AASHTO T-27
Clay Lumps Not more than 0.25%
T-112
Soft Fragments Not more than 3.5%
Coarse T-12
Abrasion Not more than 40%
Aggregate T-96
Passing 0.075 mm sieve Not more than 1.0%
T-27
Soundness test (sodium Not more than 12%
T-104
sulfate)
Sieve Analysis AASHTO T-27
Clay Lumps Not more than 1% T-112
Passing 0.075 mm sieve Not more than 3% T-27
Fine
Soundness test (Sodium Not darker than the T-104
Aggregate
Sulfate) standard T-71
Colormatic test for organic T-26
Impurities
Water Potable Water pH Value 4.5 to 8.0 AASHTO T-26
Yield & tensile strength 6% maximum under

Reinforcing
Bending, dimension & nominal mass AASHTO M-31
Steel
phosphorous content
1.5.3 Storage of Cement and Aggregates
All cement shall be stored, immediately upon delivery at the Site, in weatherproof building which will
protect the cement from dampness. The floor shall be raised from the ground. The buildings shall be
placed in locations approved by the Engineer. Provisions for storage shall be ample, and the
shipments of cement as received shall be separately stored in such a manner as to allow the earliest
deliveries to be used first and to provide easy access for identification and inspection of each
shipment. Storage building shall have capacity for storage of a sufficient quantity of cement to allow
sampling at least twelve (12) days before the cement is to be used.
Bulk cement, if used, shall be transferred to elevated air tight and weatherproof bins. Stored cement
shall meet the test requirement at any time after storage when retest is ordered by the Engineer. At
the time of use, all cement shall be free-flowing and free of lumps.
The handling and storing of concrete aggregates shall be such as to prevent segregation or the
inclusion of foreign materials The Engineer may require that aggregates be stored on separate
platforms at satisfactory locations.
In order to secure greater uniformity of concrete mix, the Engineer may require that the coarse
aggregates be separated into two or more sizes. Different sizes of aggregates shall be stored in
separate bins or in separate stockpiles sufficiently removed from each other to prevent the material at
the edges of the piles from becoming intermixed.

Figure 1-6
Storage of Cement and Aggregates
1.5.4 Mixing and Strength of Structural Concrete
The concrete materials shall be proportioned in accordance with the requirements for each class of
concrete as specified in Table 1-21, using the methods as outlined in the American Concrete Institute
(ACI) Standard 211.1.8 “Standard Practice for Selecting Proportions for Normal, Heavyweight and
Mass Concrete”. Other methods of proportioning may be employed in the mix design with prior
approval by the Engineer. The mix shall either be designed or approved by the Engineer. A change in
the source of materials during the progress of work may necessitate a new mix -design. The strength
requirements for each class of concrete shall be as specified in Table 1-21.
Figure 1-7
Flow Chart of Preparation for Fresh Concrete
Trial mix is conducted to determine the exact proportion by weight of materials in concrete. This is the
basis in judging the consistency of fresh concrete.

1.5.5 Consistency
Concrete shall have a consistency such that it will be workable in the required position. It shall be of
such a consistency that it will flow around reinforcing steel but individual particles of the coarse
aggregate when isolated shall slow a coating of mortar containing its proportionate amount of sand.
The consistency of concrete shall be gauged by the ability of the equipment to properly place it and
not by the difficulty in mixing and transporting. The quantity of mixing water shall be determined by the
Engineer and shall not be varied without his consent. Concrete as dry as it is practical to place with
the equipment specified shall be used.
Figure 1-8
Slump Test on Concrete Mix
1.5.6 Batching
Measuring and batching of materials shall be done at a batching plant.
1.5.6.1 Portland Cement
Either sacked or bulk cement may be used. No fraction of a sack of cement shall be used in a batch
of concrete unless the cement is weighed. All bulk cement shall be weighed on an approved weighing
device. The bulk cement weighing hopper shall be properly sealed and vented to preclude dusting
operation. The discharge chute shall not be suspended from the weighing hopper and shall be so
arranged that cement will neither be lodged in it nor leak from it.
Accuracy of batching shall be within plus (+) or minus (-) 1 mass percent.

1.5.6.2 Water
Water may be measured either by volume or by weight. The accuracy of measuring the water shall be
within a range of error of not more than 1 percent.
1.5.6.3 Aggregates
Stockpiling of aggregates shall be in accordance with the specifications. All aggregates whether
produced or handled by hydraulic methods or washed, shall be stockpiled or binned for draining for at
least 12 hours prior to batching. Rail shipment requiring more than 12 hours will be accepted as
adequate binning only if the car bodies permit free drainage. If the aggregates contain high or non-
uniform moisture content, storage or stockpile period in excess of 12 hours may be required by the
Engineer.
Batching shall be conducted as to result in a 2 mass percent maximum tolerance for the required
materials.
1.5.6.4 Bins and Scales
The batching plant shall include separate bins for bulk cement, fine aggregate and for each size of
coarse aggregate, a weighing hopper, and scales capable of determining accurately the mass of each
component of the batch.
Scales shall be accurate to one-half (0.5) percent throughout the range used.
1.5.7 Hauling
When batches are hauled to the mixer, bulk cement shall be transported either in waterproof
compartments or between the fine and coarse aggregates. When cement is placed in contact with
moist aggregates, batches will be rejected unless mixed within 1-1/2 hours of such contact. Sacked
cement may be transported together with the aggregates.
Batches shall be delivered to the mixer separate and intact. Each batch shall be dumped cleanly into
the mixer without loss, and, when more than one batch is carried on the truck, without spilling of
material from one batch compartment into another.
1.5.8 Admixtures
The Contractor shall follow an approved design mix procedure for adding the specified amount of
admixture to each batch and will be responsible for its uniform operation during the progress of the
work. He shall provide separate scales for the admixtures which are to be proportioned by weight, and
accurate measures for those to be proportioned by volume. Admixtures shall be measured into the
mixer with an accuracy of plus or minus three (3) percent.
The use of Calcium Chloride as an admixture will not be permitted.
1.5.9 Mixing and Delivery
Concrete may be mixed at the site of construction, at a central point or by a combination of central
point and truck mixing or by a combination of central point mixing and truck agitating. Mixing and
delivery of concrete shall be in accordance with the appropriate requirements of AASHTO M 157
except as modified in the following paragraphs of this section, for truck mixing or a combination of
central point and truck mixing or truck agitating. Delivery of concrete shall be regulated so that placing
is at a continuous rate unless delayed by the placing operations. The intervals between delivery of
batches shall not be so great as to allow the concrete in place to harden partially, and in no case shall
such an interval exceed 30 minutes.

In exceptional cases and when volumetric measurements are authorized, for small project requiring
less 75 cu.m. per day of pouring, the weight proportions shall be converted to equivalent volumetric
proportions. In such cases, suitable allowance shall be made for variations in the moisture condition
of the aggregates, including the bulking effect in the fine aggregates. Batching and mixing shall be in
accordance with ASTM C 685, Section 6 through 9.
Concrete mixing, by chute is allowed provided that a weighing scales for determining the batch weight
will be used.
For batch mixing at the site of construction or at a central point, a batch mixer of an approved type
shall be used. Mixer having rated capacity of less than a one-bag batch shall not be used. The
volume of concrete mixed per batch shall not exceed the mixer’s nominal capacity as shown on the
manufacturer’s standard rating plate on the mixer except that an overload up to 10 percent above the
mixer’s nominal capacity may be permitted, provided concrete test data for strength, segregation, and
uniform consistency are satisfactory and provided no spillage of concrete takes place. The batch shall
be so charge into the drum that a portion of the water shall enter in advance of the cement and
aggregates. The flow of water shall be uniform and all water shall be in the drum by the end of the first
15 seconds of the mixing period. Mixing time shall be measured from the time all materials, except
water, are in the drum. Mixing time shall not be less than 60 seconds for mixers having a capacity of
3 3
1.5m or less. For mixers having a capacity greater than 1.5m , the mixing time shall not be less than
90 seconds. If timing starts, the instant the skip reaches its maximum raised position, 4 seconds shall
be added to the specified mixing time. Mixing time ends when the discharge chute opens.
The mixer shall be operated at the drum speed as shown on the manufacturer’s name plate on the
mixer. Any concrete mixed less than the specified time shall be discarded and disposed off by the
Contractor at his own expense.
The timing device on stationary mixers shall be equipped with a bell or other suitable warning device
adjusted to give a clearly audible signal each time the lock is released. In case of failure of the timing
device, the Contractor will be permitted to continue operations while it is being repaired, provided he
furnishes an approved timepiece equipped with minute and second hands. If the timing device is not
placed in good working order within 24 hours, further use of the mixer will be prohibited until repairs
are made.
Re-tempering concrete will not be permitted. Admixtures for increasing the workability, for retarding
the set, or for accelerating the set or improving the pumping characteristics of the concrete will be
permitted only when specifically provided for in the Contract, or authorized in writing by the Engineer.
1.5.10 Mixing Concrete-General
Concrete shall be thoroughly mixed in a mixer of an approved size and type that will insure a uniform
distribution of the materials throughout the mass.
All concrete shall be mixed in mechanically operated mixers. Mixing plant and equipment for
transporting and placing concrete shall be arranged with an ample auxiliary installation to provide a
minimum supply of concrete in case of breakdown of machinery or in case the normal supply of
concrete is disrupted. The auxiliary supply of concrete shall be sufficient to complete the casting of a
section up to a construction joint that will meet the approval of the Engineer.
Equipment having components made of aluminum or magnesium alloys, which would have contact
with plastic concrete during mixing, transporting or pumping of Portland Cement concrete, shall not be
used.
Concrete mixers shall be equipped with adequate water storage and a device of accurately measuring
and automatically controlling the amount of water used.
Materials shall be measured by weighing. The apparatus provided for weighing the aggregates and
cement shall be suitably designed and constructed for this purpose. The accuracy of all weighing

devices except that for water shall be such that successive quantities can be measured to within one
percent of the desired amounts. The water measuring device shall be accurate to plus or minus 0.5
mass percent. All measuring devices shall be subject to the approval of the Engineer. Scales and
measuring devices shall be tested at the expense of the Contractor as frequently as the Engineer may
deem necessary to insure their accuracy.
Weighing equipment shall be insulated against vibration or movement of other operating equipment in
the plant. When the entire plant is running, the scale reading at cut-off shall not vary from the weight
designated by the Engineer more than of aggregate, or one mass percent for cement, 1-1/2 mass
percent for any size of aggregate, or one (1) mass percent for the total aggregate in any batch.
1.5.11 Limitation of Mixing
No concrete shall be mixed, placed or finished when natural light is insufficient, unless and adequate
and approved artificial lighting system is operated.
During hot weather, the Engineer shall require that steps be taken to prevent the temperature of
0 0
mixed concrete from exceeding a maximum temperature of 90 F (32 C).
Concrete not in place within ninety (90) minutes from the time the ingredients were charged into the
mixing drum or that has developed initial set shall not be used. Re-tempering of concrete or mortar
which has partially hardened, that is remixing with or without additional cement, aggregate, or water
shall not be permitted.
In order that the concrete may be properly protected against the effects of rain before the concrete is
sufficiently hardened, the contractor will be required to have available at all times materials for the
protection of the edges and surface of unhardened concrete.
1.5.12 Mixing Concrete at Site
Concrete mixers may be of the revolving drum or the revolving blade type and the mixing drum or
blades shall be operated uniformly at the mixing speed recommended by the manufacturer. The pick-
up and throw-over blades of mixers shall be restored or replaced when any part or section is worn 20
mm or more below the original height of the manufacturer’s design. Mixers and agitators which have
an accumulation of hard concrete or mortar shall not be used.
3
When bulk cement is used and volume of the batch is 0.5m or more, the scale and weigh hopper for
Portland Cement shall be separate and distinct from the aggregate hopper or hoppers. The discharge
mechanism of the bulk cement weigh hopper shall be interlocked against opening before the full
amount of cement is in the hopper. The discharging mechanism shall also be interlocked against
opening when the amount of cement in the hopper is underweight by more than one (1) mass percent
or overweight by more than 3 mass percent of the amount specified.
When the aggregate contains more water than the quantity necessary to produce a saturated surface
dry condition, representative samples shall be taken and the moisture content determined for each
kind of aggregate.
The batch shall be so changed into the mixer that some water will enter in advance of cement and
aggregate. All water shall be in the drum by the end of the first quarter of the specified mixing time.
Cement shall be batched and charged into the mixer so that it will not result in loss of cement due to
the effect of wind, or in accumulation of cement on surface of conveyors of hoppers, or in other
conditions which reduce or vary the required quantity of cement in the concrete mixture.
The entire content of a batch mixer shall be removed from the drum before materials for a succeeding
batch are placed therein. The materials composing a batch except water shall be deposited
simultaneously into the mixer.

All concrete shall be mixed for a period of not less than 1-1/2 minutes after all materials, including
water, are in the mixer. During the period of mixing, the mixer shall operate at the speed for which it
has been designed.
Mixers shall be operated with an automatic timing device that can be locked by the Engineer. The
time device and discharge mechanics shall be so interlocked that during normal operation no part of
the batch will be charged until specified mixing time has elapsed.
The first batch of concrete materials placed in the mixer shall contain a sufficient excess of cement,
sand, and water o coat inside of the drum without reducing the required mortar content of the mix.
When mixing is to cease for a period of one hour or more, the mixer shall be thoroughly cleaned
1.5.13 Mixing Concrete at Central Batching Plant
The central plant is equipped with a measuring device for proper proportioning of concrete mix. All
aggregates, cement and water are accurately measured per batch. This type is also equipped with a
mixing pan for cement mixing. Mixture unloaded from the plant is ready for pouring.
Figure 1-9 Computerized Central Batching Plant
1.5.14 Mixing Concrete at Conventional Batching Plant
Sometimes called the dry type batching plant, this one has the capacity to measure the proportion of
concrete but does not mix the concrete. Measured quantities of aggregates and cement are unloaded,
through aggregate bins; to truck mixers and from there, water is added for the actual mixing of the
concrete.

Figure 1-10 Calibration (Weighing Scale)

Whether the concrete is mixed at the site, at the central plant or by transit mixers, the following control
measures should be strictly observed:
1. Batching plant should be calibrated and checked periodically.

2. If conventional batching plant is used, measuring scales must be calibrated and always
available at site.
3. The moisture content of aggregates should be determined constantly for adjustment of
mix proportions.
4. Measurement of aggregates, water and cement should be by weigh scale.
All aggregates and cement must be properly stored and covered at the batching plant.
Truck mixers, unless otherwise authorized by the Engineer, shall be of the revolving drum type, water-
tight, and so constructed that the concrete can be mixed to insure a uniform distribution of materials
throughout the mass. All solid materials for the concrete shall be accurately measured and charged
into the drum at the proportioning plant. Except as subsequently provided, the truck mixer shall be
equipped with a device by which the quantity of water added can be readily verified. The mixing water
may be added directly to the batch, in which case a tank is not required. Truck mixers may be
required to be provided with a means of which the mixing time can be readily verified by the Engineer.
The maximum size of batch in truck mixers shall not exceed the minimum rated capacity of the mixer
as stated by the manufacturer and stamped in metal on the mixer. Truck mixing, shall, unless other-
wise directed be continued for not less than 100 revolutions after all ingredients, including water, are
in the drum. The mixing speed shall not be less than 4 rpm, nor more than 6 rpm.
Mixing shall begin within 30 minutes after the cement has been added either to the water or
aggregate, but when cement is charged into a mixer drum containing water or surface wet aggregate
and when the temperature is above 320C, this limit shall be reduced to 15 minutes. The limitation in
time between the introduction of the cement to the aggregate and the beginning of the mixing may be
waived when, the judgment of the Engineer, the aggregate is sufficiently free from moisture, so that
there will be no harmful effects on the cement.
When a truck mixer is used for transportation, the mixing time specified at a stationary mixer may be
reduced to 30 seconds and the mixing completed in a truck mixer. The mixing time in the truck mixer
shall be as specified for truck mixing.
Uniformity of Mixing
The uniformity of mixing should be tested to:
a. Confirm whether, the concrete mix by transit mixed is uniform

b. Determine the variance in unit weight of mortar in concrete
c. Determine the variance in unit weight of coarse aggregate in concrete


(liter)
(liter)
(kg/liter)

1.5.15 Transporting Mixed Concrete
Mixed concrete may only be transported to the delivery point in truck agitators or truck mixers
operating at the speed designated by the manufacturers of the equipment as agitating speed, or in
non-agitating hauling equipment, provided the consistency and workability of the mixed concrete upon
discharge at the delivery point is suitable for adequate placement and consolidation in place.
Truck agitators shall be loaded not to exceed the manufacturer’s guaranteed capacity. They shall
maintain the mixed concrete in a thoroughly mixed and uniform mass during hauling.
No additional mixing water shall be incorporated into the concrete during hauling or after arrival at the
delivery point.
The rate of discharge of mixed concrete from truck mixers or agitators shall be controlled by the
speed of rotation of the drum in the discharge direction with the discharge gate fully open.
When a truck mixer or agitator is used for transporting concrete to the delivery point, discharge shall
be completed within one hour, or before 250 revolutions of the drum blades, whichever comes first
after the introduction of the cement to the aggregates. Under conditions contributing to quick stiffening
of the concrete or when the temperature of the concrete is 32 0C, or above, a time less than one hour
will be required.
1.5.16 Delivery of Mixed Concrete
The Contractor shall have sufficient plant capacity and transportation apparatus to insure continuous
delivery at the rate required. The rate of delivery of concrete during concreting operations shall be
such as to provide for the proper handling, placing and finishing of the concrete. The rate shall be
such that the interval between batches shall not exceed 20 minutes. The methods of delivering and
handling the concrete shall be such that it will facilitate placing with minimum handling.
1.5.17 Control on Handling and Placing of Mixed Concrete
A competent concrete inspector is one who is thoroughly conscious of the importance and scope of
his work and is fully informed with regard to the design and specifications. Armed with judgment
gained through experience, he will not only detect faulty construction but will also be in a position to
forestall it by preventing improper procedures. Concrete shall not be placed until forms and reinforcing
steel bars have been checked and approved by the Engineer.
If lean concrete is required in the plan or as directed by the Engineer prior to placing of reinforcing
steel bars, the lean concrete should have a minimum compressive strength of 13.8 MPa (2,000 psi)
In preparation for the placing of concrete all sawdust, chips and other construction debris and
extraneous matter shall be removed from inside the formwork, struts, stays and braces, serving
temporarily to hold the forms in correct shapes and alignment, pending the placing of concrete at their
locations, shall be removed when the concrete placing has reached an elevation rendering their
service unnecessary. These temporary members shall be entirely removed from the forms and not
buried in the concrete.
No concrete shall be used which does not reach its final position in the forms within the time
stipulated under “ Time of hauling and Placing Mixed concrete”
Concrete shall be placed so as to avoid segregation of the materials and the displacement of the
reinforcement. The use of long troughs, chutes, and pipes for conveying concrete to the forms shall
be permitted only on written authorization of the Engineer. The Engineer shall reject the use of the
equipment for concrete transportation that will allow segregation, loss of fine materials, or in any other
way will have a deteriorating effect on the concrete quality.

Open troughs and chutes shall be of metal lined; where step slopes are required, the chutes shall be
equipped with baffles or be in short lengths that reverse the direction of movement to avoid
segregation.
All chutes, troughs and pipes shall be kept clean and free from coatings of hardened concrete by
thoroughly flushing with water after each run. Water used for flushing shall be discharged clear of the
structure.
When placing operations would involve dropping the concrete more than 1.5 m. concrete shall be
conveyed through sheet metal or approved pipes. As far as practicable, the pipes shall be kept full of
concrete during placing and their lower end shall be kept burled in the newly placed concrete. After
initial set of the concrete, the forms shall not be jarred and no strain shall be placed on the ends of
projecting reinforcement bars.
The concrete shall be placed as nearly as possible to its final position and the use of vibrators for
moving of the mass of fresh concrete shall not be permitted.
1.5.18 Placing of Concrete by Pneumatic Means
Pneumatic placing of concrete will be permitted only if specified in the Special Provisions or
authorized by the Engineer. The equipment shall be arranged so that vibration will not damage
freshly placed concrete.
Where concrete is conveyed and placed by pneumatic means, the equipment shall be suitable in kind
and adequate in capacity for the work. The machine shall be located as close as practicable to the
work. The discharge lines shall be horizontal or inclined upwards from the machine. The discharge
end of the line shall not be more than 3 m from the point of deposit.
At the conclusion of placing the concrete, the entire equipment shall be thoroughly cleaned.
1.5.19 Placing of Concrete by Pumping
The placing of concrete by pumping will be permitted only if specified or if authorized by the Engineer.
The equipment shall be arranged so that vibration will not damage freshly placed concrete.
Where concrete is conveyed and placed by mechanically applied pressure the equipment shall be
suitable in kind and adequate in capacity for the work. The operation of the pump shall be such that a
continuous stream of concrete without air pockets is produced. When pumping is completed, the
concrete remaining in the pipeline, if it is to be used, shall be ejected in such a manner that there will
be no contamination of the concrete or separation of the ingredients. After this operation, the entire
equipment shall be thoroughly cleaned.

Figure 1-11
Control in Placing Concrete
1.5.20 Compaction of Concrete
Concrete during and immediately after placing shall be thoroughly compacted. The concrete in walls,
beams, columns, deck slab, piers and the like shall be placed in horizontal layers not more than 30
cm. thick except as hereinafter provided. When less than a complete layer is placed in one operation,
it shall be terminated in a vertical bulkhead. Each layer shall be placed and compacted before the
preceding layer has taken initial set to prevent injury to the green concrete and avoid surfaces of
separation between the layers. Each layer shall be compacted so as to avoid the formation of a
construction joint with the preceding layer.
The compaction shall be done by mechanical vibration. The concrete shall be vibrated internally
unless special authorization of other methods is given by the Engineer or is provided herein. Vibrators
shall be of a type, design and frequency approved by the Engineer. The intensity of vibration shall be
such as to visibly affect a mass of concrete with a 3 cm slump over a radius of at least 50 cm. A
sufficient number of vibrator shall be provided to properly compact each batch immediately after it is
placed in the forms. Vibrators shall be manipulated so as to thoroughly work the concrete around the
reinforcement and embedded fixtures and into the corners and angles of the forms and shall be
applied at the point of placing and in the area of freshly placed concrete. The vibrators shall be
inserted into and withdrawn from the concrete slowly. The vibration shall be of sufficient duration and
intensity to compact the concrete thoroughly but shall not be continued so as to cause segregation
and at any one point to the extent that localized areas of grout to formed. Application of vibrators shall
be at points uniformly spaced, and not farther apart than twice the radius over which the vibration is
visibly effective. Vibration shall not be applied directly or thru the reinforcement to sections or layers of
concrete that have hardened to the degree that the concrete ceases to be plastic under vibration. It
shall not be used to make concrete flow in the forms over distances so great as to cause segregation,
and vibrators shall not be used to transport concrete in the forms.

Figure 1-12 Proper Way of Vibrating Fresh Concrete
Concrete should be vibrated since such method permits the satisfactory placing of denser and
stronger mixes than is possible by hand tamping. Vibration is considered sufficient when decrease in
volume is no longer apparent. The systematic way of vibrating each new lift is illustrated in Figure 1-
12. If for any strong reason vibrators cannot be made available, as for instance, a breakdown, then
hand tamping will be resorted to.
But in so doing the inspector should see to it that there is sufficient compaction but without
segregation. Concrete if not properly placed in the forms, will not reflect the care exercised during the
design and other control phases. Check points in placing concrete in the forms are as follows:
a. Concrete shall not be dropped more than 1.5 m.

b. Concrete shall be placed as near as possible to its final position to prevent segregation.
c. Excess water that may accumulate on the top layer of a deep pour should be removed carefully.
d. Vibration shall be of sufficient duration to provide thorough compaction, but not prolonged as to
cause segregation.
e. Concrete shall be thoroughly consolidated by means of vibrations inserted in the concrete vertical
position.
f. Vibrators shall not be operated longer than 15 seconds in any one location.
1.5.21 Concrete Surface Finishing
Surface finishing shall be classified as follows:
 Class 1, Ordinary Finish

 Class 2, Rubbed Finish
 Class 3, Floated Finish
All concrete shall be given Class 1, Ordinary Finish and additionally any further finish as specified.
Unless otherwise specified, the following surfaces shall be given a class 2, Rubbed finish.
1. The exposed faces of piers, abutments, wingwalls, and retaining walls

2. The outside faces of girders, T-beams, slabs, columns, brackets, curbs, headwalls, railings, arch
rings, spandrel walls and parapets.
Excluded, however, are the tops and bottoms of floor slabs and sidewalks, bottoms of beams and
girders, sides of interior beams and girders, backwalls above bridge seats or the underside of
copings. The surface finish on piers and abutments shall include all exposed surface below the bridge
seats to 20 cm below low water elevation or 50 cm below finished ground level when such ground
level is above the water surface. Wingwalls shall be finished from the top to 50 cm below and for a
depth of 20 cm below the top on the back sides.
Unless otherwise specified, the surface of the traveled way shall be Class 3, Floated Finished.

1.5.21.1 Class 1 Concrete Ordinary Finish
Immediately following the removal of forms, all fins and irregular protection shall be removed from all
surface except from those which are not to be exposed or not to be waterproofed. On all surfaces the
cavities produced by form ties and all other holes, honeycomb spots, broken corners or edges and
other defects shall be thoroughly cleaned, and after having been kept saturated with water for a
period of not less than three hours shall be carefully pointed and made true with a mortar of cement
and fine aggregate mixed in the proportions used in the grade of the concrete being finished. Mortar
used in pointing shall not be more than one hour old. The mortar patches shall be cured as specified
under Subsection 407.3.8 of the DPWH Standard Technical specifications. All construction and
expansion joints in the completed work shall be left carefully tooled and free of all mortar and
concrete. The joint filler shall be left exposed for its full length with a clean and true edges.
The resulting surface shall be true and uniform. All repaired surfaces, the appearance of which is not
satisfactory to the Engineer, shall be “rubbed” as specified below.
1.5.21.2 Class 2 Concrete Rubbed Finish
After removal of forms, the rubbing of concrete shall be started as soon as its condition will permit.
Immediately before starting this work, the concrete shall be kept thoroughly saturated with water for a
minimum period of three hours. Sufficient time shall have elapsed before the wetting down to allow
the mortar used in the pointing of road holes ad defects to thoroughly set. Surfaces to be finished
shall be rubbed with a minimum coarse carborundum stone using a small amount of mortar on each
face. The mortar shall be composed of cement ad fine sand mixed in proportions used in the concrete
being finished. Rubbing shall be continued until all form marks, protections and irregularities have
been removed, all voids have been filled, and a uniform surface has been obtained. The face
produced by this rubbing shall be left in place at this time.
After all concrete above the surface being created has been cast, the final finish shall be obtained by
rubbing with a fine carborundum stone and water. This rubbing shall be continued until the entire
surface is of smooth texture and uniform color.
After the final rubbing is completed and the surface has dried, it should be rubbed with burlap to
remove loose powder and shall be left free from all unsound patches, paste, powder and
objectionable marks.
1.5.21.3 Class 3 Concrete Floated Finish
After the concrete is compacted as specified in the DPWH standard specification, Compaction of
Concrete, the surface shall be carefully struck off with a strike board to conform to the cross-section
and grade shown on the Plans. Proper allowance shall be made for camber if required. The strike
board may be operated longitudinally or transversely and shall be moved forward with the combined
longitudinal and transverse motion, the manipulation being such that neither is raised from the side
forms during the process. A slight excess of concrete shall be kept in front of the cutting edge at all
times.
After striking off and consolidating as specified above, the surface shall be made uniform by
longitudinal or transverse floating or both. Longitudinal floating will be required except in places where
this method is not feasible.
The longitudinal float, operated from foot bridges, shall be worked with a sawing motion while held in
a floating position parallel to the road centerline and passing gradually from one side of the pavement
to the other. The float shall then be moved forward one-half of each length and the above operation
repeated. Machine floating which produces an equivalent result may be substituted for the above
manual method.
The transverse float shall be operated across the pavement by starting at the edge and slowly
moving to the center and back again to the edge. The float shall then be moved forward one-half
of each length and the above operation repeated. Care shall be taken to preserve the crown and
cross- section of the pavement.

After the longitudinal floating has been completed and the excess water removed, but while the
concrete is still plastic, the slab surface shall be tested for trueness with a straight edge. For the
purpose, the Contractor shall furnish and use an accurate 3 m straight-edge with handles 1 m longer
than one-half the width of the slab.
The straight-edge shall be held in successive positions parallel to the road centerline and in contact
with the surface and the whole area gone over from one side of the slab to the other as necessary
advancement along the deck shall be in successive stages of not more than one-half the length of the
straight-edge. Any depression found shall be immediately filled with freshly mixed concrete, struck off,
consolidated and refinished. The straight-edge testing and refloating shall continue until the entire
surface is found to be free from observable departure from the straight-edge and the slabs has the
required grade and contour, until there are no deviations of more than 3 mm under the 3 m straight-
edge.
When the concrete has hardened sufficiently, the surface shall be given a broom finish. The broom
shall be an approved type. The strokes shall be square across the slabs from edge to edge, with
adjacent strokes slightly overlapped, and shall be made by drawing the broom without tearing the
concrete, but so as to produce regular corrugations not over 3 mm in depth. The surface as thus
finished shall be free from porous spots, irregularities, depressions and small pockets or rough spots
such as may be caused by accidental disturbing, during the final brooming of particles of coarse
aggregate embedded near the surface.
1.5.22 Concrete Surface Finish for Sidewalk
After the concrete has been deposited in place, it shall be compacted and the surface shall be struck
off by means of strike board and floated with a wooden or cork float. An edging tool shall be used on
all edges and at all expansion joints. The surface shall not vary more than 3 mm under a 3 m straight-
edge. The surface shall have a granular or matted texture which will not slick when wet.
1.5.23 Curing Concrete
All newly placed concrete shall be cured in accordance with this Specification, unless otherwise
directed by the Engineer. The curing method shall be one or more of the following:
1.5.23.1 Water Method
The concrete shall be kept continuously wet by the application of water for a minimum period of 7
days after the concrete has been placed.
The entire surface of the concrete shall be kept damp by applying water with an atomizing nozzle.
Cotton mats, rugs, carpets, or earth or sand blankets may be used to retain the moisture. At the
expiration of the curing period the concrete surface shall be cleared of the curing medium.
1.5.23.2 Curing Compound
Surfaces exposed to the air may be cured by the application of an impervious membrane if approved
by the Engineer.
The membrane forming compound used shall be practically colorless liquid. The use of any
membrane-forming compound that will alter the natural color of the concrete or impart a slippery
surface to any wearing surface shall be prohibited. The compound shall be applied with a pressure
spray in such a manner as to cover the entire concrete surface with a uniform film and shall be of
such character that it will harden within 30 minutes after application. The amount of compound
applied shall be ample to seal the surface of the concrete thoroughly. Power-operated spraying
equipment shall be equipped with an operational pressure gauge and means of controlling the
pressure.
The curing compound shall be applied to the concrete following the surface finishing operation
immediately after the moisture sheen begins to disappear from the surface, but before any drying

shrinkage or craze cracks begin to appear. In the event of any delay, in the application of the curing
compound, which results in any drying or cracking of the surface, application of water with an
atomizing nozzle as specified under “Water Method”, shall be started immediately and shall be
continued until the application of the compound is resumed or started, however, the compound shall
not be applied over any resulting free standing water. Should the film of compound be damaged from
any cause before the expiration of 7 days after the concrete is placed in the case of structures, the
damaged portion shall be repaired immediately with additional compound.
Figure 1-13 Curing of Deck Slab
1.5.23.3 Waterproof Membrane Method
The exposed finished surfaces of concrete shall be sprayed with water, using a nozzle that so
atomizes the flow that a mist and not a spray is formed until the concrete has set, after which a curing
membrane of waterproof paper or plastic sheeting shall be placed. The curing membrane shall
remain in place for a period of not less than 72 hours.
Waterproof paper and plastic sheeting shall conform to the specification of AASHTO M 171.
The waterproof paper or plastic sheeting shall be formed into sheets of such width as to cover
completely the entire concrete surface.
All joints in the sheets shall be securely cemented together in such a manner as to provide a
waterproof joint. The joint seams shall have a minimum lap of 100 mm.
The sheets shall be securely weighed down by placing a bank of earth on the edges of the sheets or
by other means satisfactory to the Engineer.
Should any portion of the sheets be broken or damaged within 72 hours after being placed, the
broken or damaged portions shall be immediately repaired with new sheets properly cemented into
place.

Sections of membrane which have lost their waterproof qualities or have been damaged to such an
extent as to render them unfit for curing, the concrete shall not be used.
1.5.23.4 Forms-in Place Method
Formed surfaces of concrete may be cured by retaining the form-in-place. The forms shall remain in
place for a minimum period of 7 days after the concrete has been placed, except that for members
over 50 cm in least dimensions, the forms shall remain in place for a minimum period of 5 days.
Wooden forms shall be kept wet by watering during the curing period.
1.5.23.5 Curing Cast-in-Situ Concrete
All newly placed concrete for cast-in-situ structures, other than highway bridge deck, shall be cured by
the water method, or as permitted herein, by the curing compound method, all in accordance with the
requirements of Subsection, 407.3.8 Curing Concrete.
The curing compound method may be used on concrete surfaces which are to be buried under
ground and surfaces where only Ordinary Surface Finish is to be applied and on which a uniform color
is not required and which will not be visible from public view.
The top surface of highway bridge decks shall be cured by either the curing compound method or
water method. The curing compound shall be applied progressively during the deck finishing
operations. The water cure shall be applied not later than 4 hours after completion of the deck
finishing.
When deemed necessary by the Engineer during periods of hot weather, water shall be applied to
concrete surface being cured by the curing compound method.
1.5.23.6 Curing Pre-Cast Concrete Piles
All newly placed concrete for pre-cast concrete piles, conventionally reinforced or prestressed shall be
cured by the “Water Method” as described in Section 1.5.23.1 of this manual (Subsection 407.3.8 (1)
of the DPWH Standard Specifications) except that the concrete shall be kept under moisture for at
least 14 days. At the option of the Contractor, steam curing may be used in which the steam curing
provisions in section 1.6.4.6a of this manual (Subsection 407.3.8 (6) of the DPWH standard
specifications) shall apply except that the concrete shall be kept wet for at least 7 days including the
holding and steaming period
1.5.24 Falsework and Formwork
1.5.24.1 Falsework Design and Drawings
Detailed working drawings and supporting calculations of the falsework shall be furnished by the
Contractor to the Engineer. No falsework construction shall start until the Engineer has reviewed and
approved the design. The Contractor shall provide sufficient time for the Engineer to complete this
review. Such time shall be proportionate to the complexity of the falsework design and in no case be
less than two weeks.
The Contractor may review the falsework drawings at anytime provided sufficient time is allowed for
the Engineer’s review before construction is started on the revised portion.
Assumptions used in the design of the falsework shall include but not be limited to the following:
1. The entire superstructure cross-section, except for the railing, shall be considered to be placed
at one time, except when in the opinion of the Engineer, a portion of the load is carried by
members previously cast and having attained a specified strength

2. The loading used on timber piles shall not exceed the bearing value for the pile and shall in no
case exceed 20 tons per pile.
3. Soil bearing values and soil condition (wet and dry) shall be designated by the Contractor on
the falsework drawings. Falsework footings shall be designed to carry the loads imposed upon
them without exceeding estimated soil bearing values or allowable settlements.
4. The maximum loadings and deflections used on jacks, brackets, columns and other
manufactured devices shall not exceed the manufacturer’s recommendations. If requested by
the Engineer, the Contractor shall furnish catalogue or other data verifying these
recommendations.
5. If the concrete is to be prestressed, the falsework shall be designed to support any increased
or readjusted loads caused by the prestressing forces.
6. Joints supporting slabs and overhangs shall be considered as falsework and designed as such.
For the construction of falsework over and adjacent to roadways where falsework openings are
required for maintaining traffic, the Contractor shall provide any additional features for the work
needed to ensure that the falsework will be stable if subjected to impact by vehicles.
The falsework design at the locations where said openings are required shall include but not be
limited to the following minimum provisions:
a. Each exterior stringer in a span shall be securely anchored to the following cap or framing.
b. Adequate bracing shall be used during all stages of falsework construction and removal over or
adjacent to public traffic.
c. Falsework members shall be at least 300 mm clear of temporary protective railing members.
The falsework drawings shall include a superstructure placing diagram showing proposed concrete
placing sequence and construction joint locations, except where a schedule for placing concrete is
shown on the Contract Plans, no deviation will be permitted there from unless approved in writing by
the Engineer.
The falsework drawings shall show pedestrian openings which are required through the falsework.
Anticipated total settlements of falsework and forms shall be indicated by the Contractor on the
falsework drawings. These should include falsework footing settlements over 20 mm which will not be
allowed unless otherwise permitted by the Engineer. Deck slab forms between girders shall be
constructed with no allowance for settlement relative to the girders.
Detailed calculations by the Contractor showing the stresses, deflections, and camber necessary to
compensate for said deflections in all load supporting members shall be supplied.
After approving the Contractor’s falsework deflection camber, the Engineer will furnish to the
Contractor the amounts of camber necessary to compensate for vertical alignment or anticipated
structure deflection, if these are not shown on the drawings. The total camber used in constructing
falsework shall be the sum of the aforementioned cambers.
1.5.24.2 Falsework Construction
The falsework shall be constructed to conform to the falsework drawings. The materials used in the
falsework construction shall be of the quantity and quality necessary to withstand the stresses
imposed. The workmanship used in the falsework shall be of such quality that the falsework will

support the loads imposed on it without excessive settlement or take-up beyond that shown on the
falsework drawings.
When falsework is supported on piles, the piles shall be driven to a bearing value equal to the total
calculated pile loading as shown on the falsework drawings.
Suitable jacks or wedges shall be used in connection with falsework to set the forms to their required
grade and to take up any excessive settlement in the falsework either before or during the placing of
concrete.
The Contractor shall provide tell-tales attached to the soffit forms easily readable and in enough
systematically-placed locations to determine the total settlement of the entire portion of the structure
where concrete is being place.
Should unanticipated events occur, including settlements that deviate more than ± 20 mm from those
indicated on the falsework drawings, which in the opinion of the Engineer would prevent obtaining a
structure conforming to the requirement of the Specification, the placing of concrete shall be
discontinued until corrective measures satisfactory to the Engineer are provided. In the event
satisfactory measures are not provided prior to initial set of the concrete in the affected area, the
placing of concrete shall be discontinued at a location determined by the Engineer. All unacceptable
concrete shall be removed.
1.5.24.3 Removing Falsework
Unless otherwise shown on the drawings, or permitted by the Engineer, falsework supporting any
span of a supported bridge shall not be released before 14 days after the last concrete, excluding
concrete above the bridge deck, has been placed. Falsework supporting any span of a continuous or
rigid frame bridge shall not be released before 14 days after the last concrete, excluding concrete
above the bridge deck, has been placed in that span and in the adjacent portions of each adjoining
span for a length equal to at least half the length of the span where the falsework is to be released.
Falsework supporting deck overhangs and deck slabs between girders shall not be released until 7
days after the deck has been placed.
In addition to the above requirements, no falsework for bridges shall be released until the supported
concrete has attained a compressive strength of at least 80% of the required 28-day strength.
Falsework for cast-in-place prestressed portion of the structure shall not be released until after the
prestressing steel has been tensioned.
All falsework materials shall be completely removed. Falsework piling shall be removed at least 50
cm below the surface of the original ground or stream bed. When falsework piling is driven within the
limits of ditch or channel excavation areas, the falsework piling within such areas shall be removed to
at least 50 cm below the bottom and side slopes of said excavated areas.
All debris and refuse resulting from work shall be removed and the site left in a neat and presentable
condition.
1.5.24.4 Formwork Design and Drawings
The Contractor shall prepare drawings and materials data for the formwork and shutters to be
submitted to the Engineer for approval unless otherwise directed.
The requirements for design of formwork are the same as described in Section 1.5.24.1- Falsework
Design and Drawings of this Manual (Section 407.3.9 of DPWH Standard Specifications for Highways,
bridges and Airport Volume II).
1.5.24.5 Formwork Construction
Concrete forms shall be mortar-tight, true to the dimensions, lines and grades of the structure and
with the sufficient strength, rigidity, shape and surface smoothness as to leave the finished works true

to the dimensions shown on the Plans or required by the Engineer and with the surface finish as
specified.
Formwork and shutters are to be constructed in accordance with the approved Plans.
Figure 1-14 Formworks and Falsework
The inside surfaces of forms shall be cleaned of all dirt, mortar and foreign material. Forms which will
later be removed shall be thoroughly coated with form oil prior to use. The form oil shall be of
commercial quality form oil or other approved coating which will permit the ready release of the forms
and will not discolor the concrete.
Concrete shall not be deposited in the forms until all work in connection with constructing the forms
has been completed, all materials required for the unit to be poured, and the Engineer has inspected
and approved said forms and materials. Such work shall include the removal of all dirt, chips,
sawdust and other foreign materials from the forms.
The rate of depositing concrete in forms shall be such to prevent bulging of the forms or form panels
in excess of the deflections permitted by the Specification.
Forms for all concrete surfaces which will not be completely enclosed or hidden below the permanent
ground surface shall conform to the requirements herein for forms for exposed surfaces. Interior
surfaces of underground drainage structures shall be completely enclosed surfaces.
Formwork for concrete placed under water shall be watertight. When lumber is used, this shall be
planed, tongued and grooved.
Forms for exposed concrete surface shall be designed and constructed so that the formed surface of
the concrete does not undulate excessively in any direction between studs, joists, form stiffeners, form

fasteners, or wales. Undulations exceeding either 2 mm or 1/270 of the center to center distance
between studs, joists, form stiffeners, or wales will be considered to be excessive. Should any form of
forming system, even though previously approved for use, produce a concrete surface with excessive
undulations, its use shall be discontinued until modifications satisfactory to the Engineer have been
made. Portions of concrete structures with surface undulations in excess of the limits herein specified
may be rejected by the Engineer.
All exposed surfaces of similar portions of a concrete structure shall be formed with the same forming
material or with materials which produce similar concrete surface textures, color and appearance.
Forms for exposed surfaces shall be made of form materials of even thickness and width and with
uniform texture. The materials shall have sharp edges and be mortar-tight.
Forms for exposed surfaces shall be constructed with triangular fillets at least 20 mm wide attached
so as to prevent mortar runs and to produce smooth straight chamfers at all sharp edges of the
concrete.
For fasteners consisting of form bolts, clamps or other devices shall be used as necessary to prevent
spreading of the forms during concrete placement. The use of ties consisting of twisted wire loops to
hold forms in position will not be permitted.
Anchor devices may be cast into the concrete for later use in supporting forms or for lifting precast
members. The use of driven types of anchorage for fastening forms of form supports to concrete will
not be permitted.
1.5.24.6 Removal of Forms and Falsework
Forms and falsework shall not be removed without the consent of the Engineer. The Engineer’s
consent shall not relieve the Contractor of responsibility for the safety of the work. Blocks and
bracing shall be removed at the time the forms are removed and in no case shall any portion of the
wood forms be left in the concrete.
Falsework removal for continuous or cantilevered structures shall be as directed by the Engineer or
shall be such that the structure is gradually subjected to its working stress.
When concrete strength tests are used for removal of forms and supports, such removal should not
begin until the concrete has attained the percentage of the specified design strength shown in the
table below.
Minimum Percentage of
Location Minimum Time
Design Strength
Centering under girders, beams frames or arches 14 days 80%
Floor slabs 14 days 70%
Walls 1 day 70%
Columns 2 days 70%
Sides of beams and all other vertical surfaces 1 day 70%

Source: 2004 DPWH Standard Specifications
In continuous structures, falsework shall be released in any span until the first and second
adjoining spans on each side have reached the strength specified herein, or in the Special
Specifications. When cast-in-place post tensioned bridges are constructed, falsework shall remain in
place until all post tensioning has been accomplished.
Falsework under all spans of continuous structures shall be completely released before concrete is
placed in railings and parapets. In order to determine the condition of column concrete, forms shall be
removed from columns before releasing supports from beneath beams and girders.

Form and falsework shall not be released from under concrete without first determining if the concrete
has gained adequate strength without regard to the time element. In the absence of strength
determination, the forms and falsework are to remain in place until removal is permitted by the
Engineer.
The forms for footings constructed within cofferdams or cribs may be left in place when, in the opinion
of the Engineer, their removal would endanger the safety of the cofferdam or crib, and when the forms
so left intact will not be exposed to view in the finished structure. All other forms shall be removed
whether above or below the ground line or water level.
All forms shall be removed from the cells of the concrete box girders in which utilities are present and
all formwork except that necessary to support the deck slab shall be removed from the remaining cells
of the box girder.
To facilitate finishing, forms used on ornamental work, railing, parapets and exposed vertical surfaces
shall be removed in not less than 12 nor more than 48 hours, depending upon weather conditions. In
order to determine the condition of concrete in columns, forms shall always be removed from them
before the removal of shoring from beneath beams and girders.
Falsework and centering for spandrel-filled arches not be struck until filling at the back of abutments
has been placed up to the spring line. Falsework supporting the deck of rigid frame structure shall not
be removed until fills have been placed back to the vertical legs.
1.5.25 Reinforcing Steel
1.5.25.1 Storage and Protection Against Corrosion
Steel reinforcement shall be stored above the surface of the ground upon platforms, skids, or other
supports and shall be protected as far as practicable from mechanical injury and surface deterioration
caused by exposure to conditions producing rust. When placed in the work, reinforcement shall be
free from dirt, detrimental rust, loose scale, paint, grease, oil, or other foreign materials.
Reinforcement shall be free from injurious defects such as cracks and laminations. Rust, surface
seams, surface irregularities or mill scale will not be cause for rejection, provided the minimum
dimensions, cross sectional area and tensile properties of a hand wire brushed specimen meets the
physical requirements for the size and grade of steel specified.
Figure 1-15 Storage and Protection of Steel Bars
1.5.25.2 Placing and Fastening
All steel reinforcement shall be accurately placed in the position shown on the Plans or required by
the Engineer and firmly held there during the placing and setting of the concrete. Bars shall be tied at
all intersections except where spacing is less than 300mm in each directions, in which case, alternate
intersections shall be tied. Ties shall be fastened on the inside.

Distance from the forms shall be maintained by means of stays, blocks, ties, hangers, or other
approved supports, so that it does not vary from the position indicated on the Plans by more than
6mm. Blocks for holding reinforcement from contact with the forms shall be precast mortar blocks of
approved shapes and dimensions. Layers of bars shall be separated by precast mortar blocks or by
other equally suitable devices. The use of pebbles, pieces of broken stone or brick, metal pipe and
wooden blocks shall not be permitted otherwise shown on the Plans or required by the Engineer, the
minimum distance between bars shall be 40 mm. Reinforcement in any member shall be placed and
then inspected and approved by the Engineer before the placing of concrete begins. Concrete placed
in violation of this provision may be rejected and removal may be required. If fabric reinforcement is
shipped in rolls, it shall be straightened before being placed. Bundled bars shall be tied together at not
more than 1.8m intervals.
Figure 1-16 Placing/Erection/Fastening of Rebars
1.5.25.3 Bending
All reinforcing bars requiring bending shall be cold-bent to the shapes shown on the Plans or required
by the Engineer. Bars shall be bent around a circular pin having the following diameter of the bar (d):
Nominal diameter, d, mm Pin diameter (D)

10 to 20 6d
25 to 28 8d
32 and greater 10d
Bends and hooks in stirrups or ties may be bent to the diameter of the principal bar enclosed therein.
1.5.25.4 Splicing
All reinforcement shall be furnished in the full lengths indicated on the Plans. Splicing of bars, except
where shown on the Plans, will not be permitted without the written approval of the Engineer. Splices
shall be staggered as far as possible and with a minimum separation of not less than 40 bar
diameters. Not more than one-third of the bars may be spliced in the same cross-section, except
where shown on the Plans.
Unless otherwise shown on the Plans, bars shall be lapped a minimum distance of:
Splice Type Grade 40 Grade 60 But not less than

Tension 24 bar dia 36 bar dia 300 mm
Compression 20 bar dia 24 bar dia 300 mm
In lapped splices, the bars shall be placed in contact and wired together. Lapped splices will not be
permitted at locations where the concrete section is insufficient to provide minimum clear distance of
one and one-third the maximum size of coarse aggregate between the splice and the nearest

adjacent bar. Welding of reinforcing steel shall be done only if detailed on the Plans or if authorized by
the Engineer in writing. Spiral reinforcement shall be spliced by lapping at least one and a half turns
or by butt welding unless otherwise shown on the Plans.
1.6 PRESTRESSED CONCRETE STRUCTURES
1.6.1 Packaging, Storing and Shipping
Prestressing steel shall be packaged in containers or other shipping forms for the protection of the
steel against physical damage and corrosion during shipping and storage. A corrosion inhibitor which
prevents rust or other results of corrosion shall be placed in the package or form, or when permitted
by the Engineer, may be applied directly to the steel. The corrosion inhibitor shall have no deleterious
effect on the steel or concrete or bond strength of concrete to steel. Packaging or forms damaged
from any cause shall be immediately replaced or restored to original condition.
This shipping package or form shall be clearly marked with a statement that the package contains
high-strength prestressing steel and the care to be used in handling, and the type, kind and amount of
corrosion inhibitor used, including the date when placed, safety order and instructions for use.
Figure 1-17 Packaging, Storing and Shipping of Prestressing Steel
1.6.2 Sampling and Testing
All wire, strand, anchorage assemblies or bars to be shipped to the site shall be assigned a lot
number and tagged for identification purposes.
All samples submitted shall be representative of the lot to be furnished and in the case of wire or
strand, shall be taken from the same master roll.
All of the materials specified for testing shall be furnished free of cost and shall be delivered in time
for tests to be made well in advance of anticipated time of use.
The Contractor shall furnish for testing the following samples selected from each lot, if ordered by the
Engineer. The selection of samples will be made at the manufacturer’s plant by the Engineer or his
representative.
1. For pre-tensioning work-samples at least 2 m long shall be furnished of each size of wire or
strand proposed.
2. For post-tensioning work-samples of the following lengths shall be furnished of each size of wire
proposed.
a. For wire requiring heading, 2 m

b. For wires not requiring heading, sufficient length to make up one parallel-lay cable of 1.50 m
long of the same number of wires as the cable to be furnished.
c. For strand to be furnished with fittings, 1.50 m between near ends of fittings.
d. For bars to be furnished with thread ends and nuts, 1.5 m between threads at ends.
3. Anchorage assemblies – If anchorage assemblies are not attached to reinforcement samples,

two (2) anchorage assemblies shall be furnished, completed with distribution plates of each size
and type to be used.
When prestressing system has been previously tested and approved for similar projects by an agency
acceptable to the Engineer, complete tendon samples need not be furnished, provided there is no
change whatsoever in the materials, design or details previously approved.
1.6.3 Construction Requirements
Prestressed concrete structural members shall be constructed in accordance with the requirements of
Item 405, Structural Concrete and Reinforcing Steel shall be placed in accordance with the
requirements of Item 404, Reinforcing Steel, subject to the modifications and amendments contained
therein.
1.6.4 Girder Fabrication
1.6.4.1 Casting Bed/Formworks
PC girders should be subjected for higher quality control since the girders used high strength (> 35
MPa) concrete and require prestressing. The casting platforms for fabrication of prestressed concrete
girders should be produced at proper yard and equipment, so as not to cause concrete girders
harmful deformation during concrete pouring and to present natural deformation of concrete girders
when prestressing is introduced.
Forms should be made of wood or metal that corresponds to the shape, lines and dimensions shown
on the drawings. Forms are assembled with proper negative camber which considered the effect of an
expected warp due to prestressing.
The number of casting bed and forms should be prepared considering the construction schedule and
the cycle time of the fabrication.
1.6.4.2 Casting Yard
The precasting of prestressed concrete structural members may be done at a location selected by the
Contractor, subject to the approval of the Engineer.

Figure 1-18 Casting Yard
1.6.4.3 Placing Enclosures
Enclosures for prestressed reinforcement shall be accurately placed at locations on the Plans or
approved by the Engineer.
1.6.4.4 Placing Prestressing Steel
Steel units shall be accurately placed at the position shown on the Plans and firmly held during the
placing and setting of the concrete.
Ducts may be fabricated with either welded or interlocked seams. Galvanizing of the welded steel will
not be required. Ducts shall have sufficient strength to maintain their correct alignment and shape
during placing of concrete. Joints between sections of ducts shall be positive metallic connections
which do not result in angle changes at the joints. Waterproof tape shall be used at the connections.

All ducts or anchorage assemblies shall be provided with pipes or other suitable connections for the
injection of grout after prestressing. Ducts for prestressing steel shall be securely fastened in place to
prevent movement.
After installation in the forms, the end of ducts shall at all times be covered as necessary to prevent
the entry of water of debris.
Figure 1-19 Placing of Prestressing Steel
All ducts for continuous structures shall be vented over each intermediate support, and at additional
locations as shown on the Plans. Vents shall be 12.7 mm (1/2 inch) minimum diameter standard
pipe. Connections to ducts shall be made with metallic structural fasteners. The vents shall be mortar
tight, taped as necessary, and shall provide means for injection of grout through the vents and for
sealing the vents. Ends of vents shall be removed 25.4 mm (1 inch) below the roadway surface after
grouting has been completed.
Distances from the forms shall be maintained by stays, blocks, ties, hangers or other approved
supports. Blocks for holding units from contact with the forms shall be precast mortar blocks of
approved shape and dimensions. Layers of units shall be separated by mortar blocks or other equally
suitable devices. Wooden blocks shall not be left in the concrete.
When acceptable prestressing steel for post-tensioning is installed in ducts after completion of
concrete curing, and if stressing and grouting are completed within ten (10) calendar days after the
installation of the prestressing steel, rust which may form during said ten (10) days will not be a cause
for rejection of the steel.
Prestressing steel, installed, tensioned and grouted in this manner, all within ten (10) calendar days,
shall be subject to all the requirements in this Item pertaining to corrosion protection and rejection
because of rust.
No welds or grounds for welding equipment shall be made on the forms or on the steel in the manner
after the prestressing steel has been installed.
Wires, wire groups, parallel-lay cables and any other prestressing elements shall be straightened to
insure proper positioning in the enclosures.
Suitable horizontal and vertical spacers shall be provided, if required, to hold the wires in place in true
position in the enclosures.
1.6.4.5 Placing of concrete
Concrete shall not be deposited in the forms until the Engineer has inspected the placing of the
reinforcement, enclosures, anchorages and prestressing steel and given his approval thereof. The
concrete shall be vibrated with care and in such a manner as to avoid displacement of reinforcement,
conduits, or wires.

Prior to placing of concrete. The contractor shall demonstrate to the Engineer that all ducts are
unobstructed.
1.6.4.6 Curing Pre-Cast Concrete (Except Piles)
Pre-cast concrete members shall be cured for not less than 7 days by the water method or by steam
curing. Steam curing for pre-cast members shall conform to the following provisions:
a. After placement of the concrete, members shall be held for a minimum 4-hour pre-steaming
period.
b. To prevent moisture loss on exposed surfaces during the pre-steaming period, members shall be
covered immediately after casting or the exposed surface shall be kept wet by fog spray or wet
blankets.
c. Enclosures for steam curing shall allow free circulation of steam about the member and shall be
constructed to contain the live steam with a minimum moisture loss. The use of tarpaulins or
similar flexible covers will be permitted, provided they are kept in good condition and secured in
such a manner to prevent the loss of steam and moisture.
d. Steam at jets shall be low pressure and in a saturated condition. Steam jets shall not impinge
directly on the concrete, test cylinders, or forms. During application of the steam, the temperature
rise within the enclosure shall not exceed 20 C per hour. The curing temperature throughout the
enclosure shall not exceed 65 C and shall be maintained at a constant level for a sufficient time
necessary to develop the required compressive strength. Control cylinders shall be covered to
prevent moisture loss and shall be placed in a location where temperature of the enclosure will be
the same as that of the concrete.
e. Temperature recording devices that will provide an accurate continuous permanent record of the
curing temperature shall be provided. A minimum of one temperature recording device per 50 m
of continuous bed length will be required for checking temperature.
f. Curing of pre-cast concrete will be considered completed after the termination of the steam curing
cycle.
Steam curing process may be used as an alternative to water curing. The casting bed for any unit
cured with steam shall be completely enclosed by a suitable type of housing, tightly constructed so
as to prevent the escape of steam and simultaneously exclude outside atmosphere. Two to four
hours after placing concrete and after the concrete has undergone initial set, the first application of
steam or radiant heat shall be made unless retarders are used, in which case the waiting period
before application of the steam or radiant heat shall be increased from four to six hours.
Figure 1-20 Steam Curing Equipment

0
During the waiting period, the temperature within the curing chamber shall not be less than 10.0 C
0
(50 F) and live steam or radiant heat may be used to maintain the curing chamber at the proper
minimum temperature. The steam shall be at 100 percent relative humidity to prevent loss of moisture
and to provide moisture for proper hydration of the cement.
Application of the steam shall not be directly on the concrete. During application of the steam, or of
0
radiant heat, the ambient air temperature shall increase at a rate not to exceed 4.41 C per hour until
the curing temperature is reached.
0
The maximum curing temperature within the enclosure shall not exceed 71.1 C. The maximum
temperature shall be held until the concrete has reached the desired strength. De-tensioning shall
be accomplished immediately after the steam curing or the heat curing has been
discontinued and additional curing is not required after de-tensioning.
1. Curing with Low Pressure Steam
Application of live steam shall not be directed on the concrete forms as to cause localized high
temperatures.
2. Curing with Radiant Heat
Radiant heat may be applied by means of pipes circulating steam, hot oil or hot water, or by electric
heating elements. Radiant heat curing shall be done under a suitable enclosure to contain the heat
and moisture loss shall be minimized by covering all exposed concrete surfaces with plastic sheeting
or by applying an approved liquid membrane curing compound to all exposed concrete surfaces. Top
surface of concrete members to be used in composite construction shall be clear of residue of the
membrane curing compound so as not to reduce bond below design limits.
If the Contractor proposes to cure by any other special method, the method and its details shall be
subject to the approval of the Engineer.
1.6.5 Prestressing Method
The method of prestressing to be used shall be optional with the Contractor subject to all
requirements hereinafter specified.
The Contractor, prior to casting any members to be prestressed, shall submit to the Engineer for
approval complete details of the methods, materials and equipment he proposes to use in the
prestressing operations. Such details shall outline the method and sequence of stressing, complete
specifications and details of the prestressing, steel and anchoring devices proposed for use,
anchoring stresses, type of enclosures and all other data pertaining to the prestressing operations,
including the proposed arrangement of the prestressing units in the members, pressure grouting
materials and equipment.
1.6.5.1 Prestressing Equipment
Hydraulic jacks used to stress tendons shall be equipped with either a pressure gauge or a load cell
for determining the jacking stress. The pressure gauge, if used, shall have an accurate reading dial at
least 154 mm (6 inches) in diameter and each jack and its gauge shall be calibrated as a unit with the
cylinder extension in the approximate position that it will be at final jacking force, and shall be
accompanied by a certified calibration chart. The load cell, if used, shall be calibrated and shall be
provided with an indicator by means of which the prestressing force in the tendon may be determined.
The range of the load cell shall be such that the lower ten (10) percent of the manufacturer’s rated
capacity will not be used in determining the jacking stress.
Safety measures shall be taken by the Contractor to prevent accidents due to possible breaking of the
prestressing steel or the slipping of the grips during the prestressing process.

Figure 1-21 Pre-Stressing Equipment
1.6.5.2 Pre-Tensioning
The prestressing elements shall be accurately held in position and stressed by jacks. A record shall
be kept of the jacking force and the elongations produced thereby. Several units may be cast in one
continuous line and stressed at one time. Sufficient space shall be left between ends of units to permit
access for cutting after the concrete has attained the required strength. No bond stress shall be
transferred to the concrete, nor end anchorages released until the concrete has attained a
compressive strength, as shown by cylinder tests, of at least 28 MPa unless otherwise specified. The
elements shall be cut or released in such an order that lateral eccentricity or prestress will be a
minimum.
1.6.5.3 Initial Tensioning
Initial tensioning of the prestressing reinforcement will commence after the test on the cylinders
manufactured of the same concrete and particular member to be prestressed has attained a
compressive strength of 28 MPa. An initial load equivalent to 50% of the required jacking force should
be applied to all tendons at one end. Approximately 10% should be applied first to the tendon to
remove slack and to serve as starting point for elongation measurements.
Initial Final
Figure 1-22 Sequence of Tensioning

TEST PROCEDURE (Jack Loss and Mechanical Device Loss)
(a) Setting of stressing jack and mechanical device is illustrated below :
(b) Jack (A and B) of 50mm stroke.
(c) Jack (A and B) Fix.
(d) Apply the jacking Force at every 400psi or 200psi on Jack-A.

*Take the reading on Jack-A, Jack-B stressing pressure (gauge) and stroke.
*Every 50psi visual observation.
(e) Continue step (d) until the theoretical jacking force would reach, then plot the result on the
Control chart.
(f) After step (e) released the stressing jacks.
Jack Loss and Mechanical Device Loss : γ

γ = (P/P’)1/2 – 1 0.03 ≤ γ ≤ 0.04
P : Reading of Jack-A
P’ : Reading of Jack-B
TEST PROCEDURE (Test tension for PC-GIRDER)
(a) Setting of jack at both ends of the Girder without grips and put marking on High Tension
Steel at 100mm as below.
MARKING 100 MARKING

mm mm
PC-GIRDER 100
JAC
KA KB
JAC
MECHANICAL DIVICE MECHANICAL DIVICE
NO-GRIPS NO-GRIPS
(b) Fix the jack-B (50mm stroke).
(c) Apply the jacking Force at every 500psi on Jack-A.

*Take the reading on Jack-A,Jack-B stressing pressure (gauge) and stroke.
*Every 50psi visual observation.

(d) Continue step (c) until the theoretical jacking force will be reached, then
plot the result on the Control chart.
(e) After step (d) released the stressing jacks.
(f) Apply the jacking Force of every 500psi at Jack-B, same procedure of step b) –
(e).
Reading Point Fix Point

MA R K IN G M A RK IN G
PC-G IR DE R
a1 a2
L1 L8 (=L1)
L2 L7 (=L2)
L3 L6 (L=3)
L4 L5 (=L4)
Bo thsid e w ith out G rip s
Curvature friction coefficient : µ

2
µ = 1/(2x(α+(λ/μ)xL))xlog((P/P’)x(1/(1+γ) ))
α : Angular Deviation (rad) 1/2Σαi (rad)

λ/μ : 0.0133
L : Length of Cable(1/2 from fix point to reading point) L=1/2ΣLi(m)
2
P : Reading of active jack (N/mm )
2
P’ : Reading of fixed jack (N/mm )
γ : Jack loss
Modulus of Elasticity : Ep
Ep = (L/L)x(PxP’)1/2x(Am/Ap)
2
Ap : Area of Strand / Cable (mm )
2
Am : Area of Jack (mm )
L : Reading on Jack-A stroke - Jack-B Draw in (mm)
L : ΣLi (mm)
1.6.5.4 Post-Tensioning
Tensioning of the prestressing reinforcement shall not be commenced until tests on concrete
cylinders, manufactured of the same concrete and cured under the same conditions, indicated that
the concrete of the particular member to be prestressed has attained compressive strength of at least
28 MPa unless otherwise specified.
Final Tensioning
Final stressing should be conducted only after the concrete has gained the required compressive
strength of 35 MPa. Final jacking force should be applied on the other end of the girder, opposite
where the initial 50% jacking force was applied.
The sequence of tensioning the tendons shall be as follows:

a) Anchor head is installed by pushing it through the strand. Furthermore, wedge is installed
according to the total number of strand.
b) Stressing jack are installed and tightened up in such a way that the position of casting and
anchor heads has no gaps.
c) Initial stressing of 50% of the full load should be applied to the tendon, once concrete
compressive strength of more than 28MPa is attained.
d) Final load should be applied on the other end, opposite where the initial load was applied with
the same rate of application, once concrete compressive strength of more than 35Mpa is
attained.
e) During stressing, manometer reading and elongation are recorded on stressing form (Pre-
stressing Control Chart).
f) The stressing pressure and elongation measured should be within the theoretical values of ±5%
or within the pre-stressing control graph.
g) The extension strand outside of anchor head is cut and covered with concrete in preparation of
grouting works.
h) Sequence of prestressing should start from the topmost cable  and should progress going
down to cable  and cable  respectively. (see illustration below)
This will lessen the tensile stress on the PC girder.
This sequencing will also increase work efficiency.

CL
①
In general, it should be noted that there will be reduction of prestressing force due to the previously
stressed strands once the succeeding strands are stressed.
This reduction in stress should be calculated and applied to the PC strands to be adjusted.

After all concrete has attained the required strength, the prestressing reinforcement shall be stressed
by means of jacks to the desired tension and the stress transferred to the end anchorage.
Figure 1-23 Final Tensioning of

Prestressed Girder
Cast-in-place concrete shall not be post-tensioned until at least ten (10) days after the last concrete
has been placed in the member to be the post-tensioned and until the compressive strength of said
placed concrete has reached the strength specified for the concrete at the time of stressing.
The falsework under the bottom slab supporting the superstructure shall not be released until a
minimum of 48 hours have elapsed after grouting of the post-tension tendons nor until all other
conditions of the Specifications have been met.
The supporting falsework shall be constructed in such a manner that the superstructure will be free to
lift of the falsework and shorten during post-tensioning. Formwork left inside box girders to support
the roadway slab shall be detailed in such a manner so as to offer minimum resistance to girder
shortening due to shrinkage and post-tensioning.
The tensioning process shall be so conducted that the tension being applied and the elongation of the
prestressing elements may be measured at all times. The friction loss in the element, i.e., the
difference between the tension of the jack and the minimum tension, shall be determined in
accordance with Article 1.6.7 of AASHTO Standard Specifications for Highway Bridges.
Suitable shims or other approved devices shall be used to insure that the specified anchor set loss is
attained.
Prestressing tendons in continuous post-tensioned members shall be tensioned by jacking at each

end of the tendon. Such jacking of both ends need not be done simultaneously.
A record shall be kept of gage pressure and elongation at all times and submitted to the Engineer for
his approval.
1.6.5.5 Bonding / Grouting
Prestressing tendons shall be bonded to the concrete by filling the void spaced between the duct and
the tendon with grout.

Grout shall consist of Portland Cement, water and an expansive admixture approved by the Engineer.
Water shall be potable.
No admixture containing chlorides or nitrates shall be used.
Water shall first be added to the mixer followed by cement and admixture.
The grout shall be mixed in mechanical mixing equipment of a type that will produce uniform and
thoroughly mixed grout. The water content shall be not more than 19 liters (5 gallons) per sack of
cement. Re-tempering of grout will not be permitted. Grout shall be continuously agitated until it is
pumped.
Grouting equipment shall be capable of grouting at a pressure of at least 0.6894 MPa (100 psi).
Grouting equipment shall be furnished with a pressure gauge having a full-scale reading of not more
than 2.07 MPa (300 psi)
Standby flushing equipment capable of developing a pumping pressure of 1.72 MPa (250 psi) and of
sufficient capacity to flush out any partially grouted ducts shall be provided.
All ducts shall be clean and free of deleterious materials that would impair bonding of the grout or
interfere with grouting procedures. All grout shall pass through a screen with a 2 mm (0.0787 inch),
maximum clear openings prior to being introduced into the grout pump.
Grout injection pipes shall be fitted with positive mechanical shutoff valves. Vents and ejection pipes
shall be fitted with valves, caps or other devices capable of withstanding the pumping pressures.
Valves and caps shall not be removed or opened until the grout has set.
Figure 1-24 Grouting Equipment
Grout Hose
 Grout hose shall be fixed tightly

 The grout hose for ventilation shall be installed at the highest of the sheath.

1.6.5.6 Hauling
a) Preparation prior to delivery
 Trucks that would be used for hauling should be checked for any defects and damage.
 The road from the PC factory (fabrication plant) leading to the delivery site should be
inspected, the presence of any obstruction, traffic situation, and public places such as
school should be noted.
b) Delivery
 Appropriate speed limit (or 40 km/hr) should be maintained while traveling.
 On populated areas such as school vicinity, speed should be slowed down. Truck driver
should be extra cautious of the presence of pedestrian on the road.
 During night time delivery, lights should be installed in front and backside of the truck to
be more visible on the road.
 As often as necessary, the truck driver (hauler) should give information while on travel to
their office. This information should include location of the hauler, traffic condition, and
estimated time of arrival at site. The hauler should relay the information to the
Contractor’s office, and the later should then inform the site.
 Delivered PC girder should be unloaded directly from the trailer and erected using crane.
c) Safety
 During unloading and erection of the girder, signalman should be assigned to give
directions. Loading/unloading of girders shall be done by using 2 cranes
 The PC girder should be fixed to the trailer using two (2) chains tied at both ends.
 During unloading, the girder should be supported by a crane when the chain will be
removed.
 Truck driver should be instructed to maintain the required speed limit, and be cautious of
the pedestrian on the road.
 Lights should be installed on the truck during night time delivery.
 Hauler driver/operator should be well-trained and experienced.
Figure 1-25 Hauling of PC Girder

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Improvement of Quality Management for Highway

and Bridge Construction and Maintenance

QUALITY CONTROL MANUAL ON

CHAPTER 1 CONCRETE STRUCTURES

1.1 GENERAL INFORMATION

1.1.1 How Concrete is Made

1.1.2.1 Bridge Definition

Quality Control Manual on Concrete and Steel Bridge Structures -1-

Table 1-1 Bridge Elements and Attributes

Element Attribute Description

(Source DPWH BMS)

Quality Control Manual on Concrete and Steel Bridge Structures -2-

1.1.2.2 Concrete Bridge

Figure 1-1a Span Types

Quality Control Manual on Concrete and Steel Bridge Structures -3-

Figure 1-1b Pier Types

Figure 1-1c Abutment Types

Quality Control Manual on Concrete and Steel Bridge Structures -4-

1.1.3 Types of Concrete used for Bridge Structures

1.1.3.1 Plain Concrete

1.1.3.2 Reinforced Concrete

1.1.3.3 Pre-stressed Concrete

1.1.4 Some Concrete Applications Based on DPWH Items of Work

1. Item 311 - Portland Cement Concrete Pavement

1.1.5 Concrete Quality Control Parameters

1.2 MATERIALS REQUIREMENT

1.2.1 Portland Cement Type I (ASTM C 150/AASHTO M 85)

1.2.1.1 Portland Cement

Type I – Portland Cement Type IP – Portland Pozzolan Cement

Quality Control Manual on Concrete and Steel Bridge Structures -5-

Composition of Portland Cement:

Clinker + Gypsum = Portland Cement

1.2.1.2 Blended Hydraulic Cement Type 1P (ASTM C 595)

Welded tuff Fly Ash

1.2.1.3 Quality Control Tests on Cement

Quality Control Manual on Concrete and Steel Bridge Structures -6-

Type of Test Significance

Quality Control Manual on Concrete and Steel Bridge Structures -7-

1.2.2 Concrete Aggregates

Characteristics of Concrete Aggregates

 Resistant to abrasion and degradation

1.2.2.1 Fine Aggregates

Sieve Mass Percent Passing

9.5 mm (3/8 in) 100

Quality Control Manual on Concrete and Steel Bridge Structures -8-

1.2.2.2 Coarse Aggregates

Standard Alternate Class Class Class Class Class

Quality Control Manual on Concrete and Steel Bridge Structures -9-

Examples of Concrete Aggregates

Sample of a well-graded coarse aggregate. Note

Sample of a well-graded sand. Particles vary

Sample of sand which lacks larger particles.

Quality Control Manual on Concrete and Steel Bridge Structures -10-

1.2.2.3 Quality Control Tests on Concrete Aggregates

Type of Test Significance

4. Moisture Content in Fine Convenient procedure or field or plant determination of moisture

6. Unit Weight/Mass of Values of unit weight/mass are used in volumetric/ gravimetric

Quality Control Manual on Concrete and Steel Bridge Structures -11-