Lecturenotecivilengineeringmaterial2022 Chapter1-2
Lecturenotecivilengineeringmaterial2022 Chapter1-2
Lecturenotecivilengineeringmaterial2022 Chapter1-2
CEMENT
LEARNING OUTCOMES
At the end of the course, students are able to use their knowledge and skill
learned to:
CONTENTS
1.0 Introduction
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• Mortar
The mortar is a mixture of cement, fine aggregates or sand and water
to form a paste.
• Concrete
The concrete ia a mixture of cement, sand, coarse aggregates and
water under certain ratio.
Cement is manufactured with two basic raw ingredients called calcareous and
an argillaceous material. The cement in making of concrete has the property
of setting and hardening under water by virtue of chemical reaction with it
and this type of cement is called hydraulic cement.
• Calcareous
The calcareous material is a calcium oxide, such as limestone, chalk,
or oyster shells.
• Argillaceous
Argillaceous is a combination of silica and alumina that can be found
from clay, shale, and blast furnace slag.
• Setting Time
Setting refers to the stiffening of the cement paste or the change from
a plastic state to a solid state. The setting time refers to changes of the
cement paste from fluid to rigid. Setting is usually described in two levels
namely, initial setting and final setting.
• Initial Setting
Initial setting is defined as the beginning of the noticeable stiffening in
the cement paste andit’s corresponding to the rapid rise temperature.
This normally takes about 45 – 175 minutes.
• Final Setting Time
This refers to completion of setting which correspond to the peak
temperature in the cement paste. The stiffening of cement paste
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increase as the volume of the gel increases and the stage at which this
is completed, the final hardening process begins. It normally takes
between 3 to 10 hours for this to happen.
• Hardening
This is referred to the gained of the strength of the cement paste.
Actually, during the setting time, the cement gained very little strength.
The water causes the hardening of cement through a process called
hydration. Hydration is a chemical reaction in which the major
compounds in cement form chemical bonds with water molecules and
become hydrates or hydration products.
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Dicalcium Silicate, Tricalcium Aluminate and TetracalciumAluminoferitteto fit
the applications.
Cements can be classified into two categories namely hydraulic cement and
high alumina cement.
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compositions are made, to suit the varying demands of different kinds of
structural application.
d) Cement Hydration
Hydration is chemical reaction between cement particles and water. The
features of this reaction are the change in matter, the change in energy
level, and the rate of reaction. Example: Tricalcium silicate + Water →
Calcium silicate hydrates (C-S-H) + Calcium hydroxide.
d) Type of cement based on usage
The type of cement used based on usage bellow;
i) Ordinary Portland Cement – OPC (BS 12: 1971)
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OPC has a medium rate of hardening and is suitable for most type of
work. It is the one most commonly used for structural purposes when
the special properties specified for other four types of cement are not
required.
ii) Rapid Hardening Portland Cement– RHPC (BS 12: 1971)
RHPC hardens rather more rapidly than OPC. It is similar in chemical
composition to OPC but the proportions of the various compounds may
be slightly different, and it is finely ground. Due to its finer grinding, it
will increase the rate of hydration at early ages, and this leads to the
increased rate of early hardening as implied by the name.
This early strength is achieved by increasing C2S and C3A content of
the cement and finer grinding. Since it has high heat evaluation, RHPC
should not be used in large masses. With 15% of C3A, it has lower
sulfate resistance. The may be limited to obtain moderate sulfate
resistance or to 5% when high sulfate resistance is required.
Rapid-hardening Portland cement should not be regarded as quick-
setting cement. The setting time specified in BS 12:1971 for RHPC is
similar as specified for OPC
iii) White and Coloured Portland Cement (BS 12: 1971)
Generally used for decorative work. It is made by using China clay in
place of ordinary clay to exclude impurities, especially iron oxide and
limestone. Coloured cements are made by mixing pigments with
Portland cement.
iv) Low Heat Portland Cement – LHPC (BS 1370: 1974)
LHPC hardens and evolves heat more slowly than OPC. It has slightly
different chemical composition. It is obtained by increasing the
proportion of C2S and reducing C3S and C3A. It thus hydrates more
slowly and evolves heat less rapidly than OPC. The strength of LHPC
is slow developed but the ultimate strength is same. However, the initial
setting time is greater than OPC.
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Table 1.3: Trace Setting Time for OPC, RHPC and LHPC
Setting Time
Initial Setting Final Setting
Cement
Time, minutes Time, minutes
Type
(min) (max)
OPC 30 600
RHPC 30 600
LHPC 60 600
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that of OPC. At higher water cement ratios, the HSPC has about 80%
higher strength and at lower cement ratio 40% higher strength than
OPC.
viii) Masonry Cement (BS 5224: 1976)
For hand work such as rendering and bricklaying, mortar composed
only of Portland cement and sand are not ideal. Such mortars harden
too quickly, are too strong, and lack the plasticity and water retention
desirable in a masonry mortar. It has been customary to overcome this
difficulty by mixing lime with the cement mixtures. Masonry cement,
under various brand names consists of Portland cement with a fine inert
admixture and plasticizing agent.
High alumina cement is quite different both in composition and properties from
Portland cement. It is comparatively slow-setting but rapid hardening, thus,
produces very high early strength. As a considerable amount of heat is
generated during the setting and hardening process, it should not be used in
rich mixes or large masses. It is essential that the concrete be kept
continuously wet for at least 24 hours from the time it begins to harden. About
80%of the ultimate strength is developed at the age of 24 hours. High alumina
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cement has an initial setting time about 4 hours and final setting time about 5
hours. The heat that generated during the hardening period has one
advantage, as it enables the concrete to be placed at lower temperatures than
OPC.
For the same water cement ratio, the alumina cement is more workable than
Portland cement. If high alumina cement concrete is used in place where
moisture and a high temperature present simultaneously, there will be a loss
strength whether these conditions occur early of late in the life of the concrete.
High alumina cement concrete is more resistant than OPC to the action of
sulfates, therefore suitable under sea water applications. The chemical oxide
composition for high alumina cement is as shown in Table 1.5.
The raw materials are limestone or chalk and bauxite which are crushed into
lumps not exceeding 100mm. The materials are heated to the fusion point at
about 1600oC. The solidified material is fragmented and then ground to a
fineness of 2500-3200 cm2/g. The product of very dark grey powder is passed
through magnetic separators to remove metallic iron. The alumina cement is
considerably more expensive.
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Table 1.6: Chemical composition limit of Portland cement
Name of Raw Material Chemical Composition Percentage Limit
Lime
CaO 60 – 67
Silica
SiO2 17 – 25
Alumina
Al2O3 3–8
Iron Oxide
Fe2O3 0.5 – 6
Magnesium
MgO 0.1 – 4
Alkalis (Soda and or/
Na2O,K2O 0.2 – 1.3
potash)
SO3 1-3
Sulphur Trioxide
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1.3 Testing of Cement
Setting time can be determined with the Vicat apparatus. The Vicat test
requires sample of cement using the amount of water required for normal
consistency according to a specified procedure.
a) Procedure
The 1 mm (0.04in) diameter needle is allowed to penetrate the paste
for 30 seconds and the amount of penetration is measured. The
penetration process is repeated every 15 minutes until a penetration of
25 mm (1in) or less is obtained. By interpolation, the time when a
penetration of 25 mm occurs is determined and recorded as the initial
set time. The final set time is when the needle does not penetrate visibly
into the paste.
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Exercise 1:
Given the data from a vicat test as in Table 1.8. Estimate the cement initial
set time.
Table 1.8: Time (min) vs penetration (mm)
Time (minutes) 15 30 45 60 75
Penetration (mm) 44 36 28 20 12
Step 2: Find the initial time (the time when penetration 25 mm occur).
Therefore, the initial set time is about 50 min after batching of the cement
paste
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1.3.2 Gilmore Set Time Apparatus
The Gilmore requires a normal consistency cement paste sample. A pat with
a flat top is molded and the initial Gilmore needle is applied lightly to its surface.
The application surface is repeated until the pat bears the force of the needle
without appreciable indentation, and the elapsed time is recorded as the initial
time. This process is then repeated with the final Gilmore needle and the final
set time is recorded.
1.3.3 Soundness
Soundness of the cement paste refers to its ability to retain its volume after
setting. Expansion after setting, caused by delayed or slow hydration or
reactions, could result if the cement is unsound. The autoclave expansion test
is used to check the soundness of the cement paste. In this test, cement paste
bars are subjected to heat and high pressure, and the amount of expansion is
measured. ASTM C150 limits autoclave expansion to 0.8%.
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Figure 1.3: Cement autoclave expansion
Production of Portland cement deals with two basic raw ingredients namely
calcareous and argillaceous. These materials are crushed and stored in the
silos. The raw materials, in the desired proportions, are passed through
grinding mill, using either wet or dry process. The ground material is stored
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until it can be sent to the kiln. Modern dry process cement plants use a heat
recovery cycle to preheat the ground material, or feed stock, with the exhaust
gas from the kiln. Some plants use a flash furnace to further heat and feed
stock. Both the preheater and flash furnace improves the energy efficiency of
cement productions. In the kiln, the raw materials are melted at temperatures
1400oC to 1650oC, changing the materials into cement clinker. The clinker is
cooled and stored. The small amount of gypsum is added to regulate the
setting time of the cement in the concrete. The finished product may be stored
and transported in either bulk or sacks. The cement can be stored for long
periods of time, provided it is kept dry.
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1.5 Cement for High Performance Concrete
High strength concrete will normally contain not only Portland cement,
aggregate and water, but also super plasticizers and supplementary
cementing materials. It is possible to achieve compressive strengths of up to
98 Mpa using fly ash or ground granulated blast furnace slag as the
supplementary cementing materials. However, to achieve the strengths of 100
Mpa, the use of silica fume has been found to be essential.
Is a waste by-product of the production of silicon and silicon alloys, and thus
not a very well-defined material. Consequently, important to characterize any
new source of silica fume by determining the specific surface area by nitrogen
adsorption, silica, alkali and carbon contents as well as minimize the crystalline
material. Available in bulk form, its unit weight of 200-250kg/m3, but also more
preferred in the densified form of 400-450 kg/m3. Available in market already
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blended with Portland cement at 6.7 to 9.3%, by weight of the total mass of
cementitious material.
Most fly ashes result in strengths of not more than 70 MPa, but sometimes in
conjunction with silica fume can reach to the strength of 98MPa. Generally, for
producing high strength concrete, fly ash uses at 15% of the cement content.
Slag used well in ordinary concrete is suitable in high strength concrete. The
dosages rates are between 15 – 30% of cement content. For the design of
more than 98MPa, slag are to be mixed with silica fume.
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Activities
3. Schedule the maximum and minimum setting time of the following, OPC
(Ordinary Portland Cement) and LHPC (Low Heat Portland Cement)
Setting Time
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4. Given the data from Vicat Test as in Table below. Estimate the cement
initial setting time.
Time (minutes) 15 30 45 60 75
Penetration (mm) 52 40 29 20 11
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REFERENCES
1. P. Kumar Mehta, P. J. M. Monteiro. Concrete: Microstructure,
Properties, and Materials, 4th Edition. McGraw-Hill Education. 2014.
(ISBN: 9780071797870)
2. T. W. Marotta, “Basic Construction Materials”. Seventh Edition, Prentice
Hall, 2005. (TA403 .M37 2005)
3. S. Somayaji, “Civil Engineering Materials” Third Edition. Prentice Halll,
2005. (TA403 .S66 2001 N1)
4. Hegger [et al.],”Construction Materials Manual”, Basel: Birkhauser,
2006. (TA402.5.G3 .C66 2006)
5. K. W. Day, “Concrete mix design, quality control and specification” Third
Edition, London: Taylor & Francis, 2006. (TA439 .D39 2006)
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CHAPTER 2
AGGREGATE
LEARNING OUTCOMES
CONTENT
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(a) Railroad Construction (b) Road Construction
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(a) Rock Block (b) Crushed Machine
(c) Stockpile
Figure 2.2: Rock quarried
Processed Aggregate
- Heat-treated, expanded material with lightweight aggregate
characteristics.
- Example: Perlite, burnt clay, shale, processed fly-ash
Coloured-Aggregate
- Glass, ceramic, manufactured marble for decorative and architectural
purpose.
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Classification by Particle Size
Coarse Aggregate (Gravel)
- Coarse aggregate includes the particle that retain on 4.75 mm sieve.
Silt
- Particle with size from 0.002 mm to 0.075 mm.
Clay
- Particle size smaller than 0.002 mm.
Aggregate
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2.2 Type of Aggregates
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2.2.2 Light Weight Aggregate (LWA)
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Retain on 5 mm (3/16 inch) BS 410 test sieve
a) Uncrushed Gravel or Uncrushed Stone
Coarse aggregate resulting from natural
disintegration of rock
b) Crushed Stone or Crushed Gravel
i. Coarse Aggregate
Coarse aggregate produced by crushing
hard stone and gravel respectively
c) Partially Crushed Gravel or Stone
A product of blending of uncrushed and
crushed gravel or blending stone
Specific gravity (SG) is a special case of relative density defined as the ratio
of the density of a given substance, to the density of water. Substances with a
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specific gravity greater than 1 are heavier than water, and those with a specific
gravity of less than 1 are lighter than water. Light Weight Aggregates will be
explained more in 2.6.
Example:
Determine the specific gravity of high-density aggregate which the unit weight
is 2900 kg/m3. (ρwater = 1000 kg/m3).
3 3
Specific Gravity = ρa / ρwater = 2900 kg/m / 1000 kg/m = 2.9
2.3.1 Strength
Aggregate cannot transmit tensile force from one particle to another, but very
well in resisting compressive forces. In real practice the application of
aggregate such as concrete, foundation and etc. in terms of random
arrangement of particles contribute to spreading of concentrated loading
effectively. However, the aggregate should be compacted for significant
contact between particles in distributing of loading and reducing settlement.
P kN
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The advantage of angular particles and rough aggregates can create better
interlocking system and tendency to resist forces from developed friction
compare to rounded particles with smooth surface contributes to less frictions
resistance and easy to slide. High compressive strength of aggregate is useful
to enhance the capability in resisting compressive force especially for
composite materials such as concrete, asphalt concrete and etc. In normal
practice, the weight of aggregate is stronger than the composite materials.
Example:
Concrete Strength Aggregate Strength
20 N/mm2 to 50 N/mm2 70 N/mm2 to 350 N/mm2
The crushing strength of aggregate cannot be tested with any direct test. There
are some indirect tests to inform us about the crushing strength of aggregate.
This test is conducted by placing the blended aggregates in a large drum with
standard sized of steel balls. About 500 revolutions of drum rotation are carried
out, and the aggregates will pass through the sieve.
Satisfactory aggregate < 30% value of abrasion
(use for wearing surface)
< 50% value of abrasion
(use for non wearing surface)
2.3.3 Durability
2.3.4 Toughness
2.3.5 Porosity
Porosity is defined as the ratio of the volume of pores in particle to its total
volume (solid volume plus the volume of pores)
All aggregates are porous; some are more porous and some are less
depending on types of aggregate. Most of granite and limestone have very low
porosity whereas a large majority of sandstone rocks have high porosity as
high as 13% and 30%.
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Table 2.5: Rocks and Porosity (%)
Type of Rock Porosity (%)
Granite 1
Shale 3
Clay 50
Sandstone (fractured) 15
Sand 30
Gravel 25
Limestone (cavernous) 5
Chalk 20
Porosity = 100xWxGs .
(W + 100) percent
Where:
W : water absorption in percent
Gs : specific gravity on saturated surface-dry basis
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Example:
Calculate the porosity of the coarse aggregates if the water absorption is 5.5%
and the specific gravity of the aggregates is 2.73.
Porosity =
100 W Gs
%=
(100 5.5 2.73) = 14.23%
(100 + W ) (100 + 5.5)
Exercise.
Calculate the percentage of water absorption if the porosity is 10 % and the
specific gravity of the aggregates is 2.5.
Example:
Calculate the void content if given the value of aggregates specific gravity is
2.75, density of water is 1000kg/m3 and the bulk density of aggregates taken
as 1745 kg/m3.
ሺ𝑆𝐺 𝑥 𝑊ሻ−𝐵 ሺ2.75 𝑥 1000ሻ−1745
𝑉𝑜𝑖𝑑 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 = 𝑥 100 = 𝑥 100 = 𝟑𝟔. 𝟓𝟓%
𝑆𝐺 𝑥 𝑊 2.75 𝑥 1000
2.3.5 Absorption
Aggregate can capture fluid (water, moisture, asphalt binder and etc) in
surface voids. Voids represent the amount of air space between the aggregate
particles. The amount of void normally expressed as void content and can be
determined by using equation below:
Where:
SG : specific gravity
W : density of water
B : bulk density
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to 40% of void content while coarse aggregate is about 30 to 50% (depending
on size). The amount of absorption is important to be evaluated for appropriate
amount of fluid to be mixed into composite materials. Highly absorptive
aggregates require greater amount of fluid and making less economical. The
definition of absorption capacity or water absorption or absorbed moisture can
be defined as the moisture content in the saturated surface dry condition.
Further explanation of voids and moisture absorption of aggregate is illustrated
by using following figure.
a) Bone dry
The aggregate contains no moisture; this requires drying the aggregate
in an oven to a constant mass.
b) Air dry
The aggregate may have some moisture but the saturation state is not
quantified.
c) SSD (semi-saturated dry)
The aggregate’s voids are filled with moisture but the main surface area
of the aggregate particles is dry.
d) Moist
The aggregate have moisture content in excess of the SSD condition
e) Free moisture
The difference between the actual moisture content of the
aggregate and the moisture content in the SSD condition.
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Determination of moisture content (MC) can be calculated by using following
equation:
The water added to the concrete mix must be adjusted to take account on
water absorption of aggregates when making concrete, to obtain constant and
required workability and strength of concrete. The determination of MC of an
aggregate is necessary to determine the net water cement ratio for a batch of
concrete. High moisture content will increase the effective water-cement ratio
to appreciable extent and make the concrete weak unless a suitable allowance
is made. BS 812: Part 109: 1990 and MS 50 described method of
determination of moisture content and absorption of aggregate. They are:
a) Displacement method
It gives the moisture content as a percentage by mass of saturated
surface dry sample
Concrete mix proportion are normally based on the weight of aggregate in their
saturated and surface dried condition and any change in moisture content
must be reflected in the adjustment to the weight of aggregate and the mix.
Example:
Determine the moisture content of the sample of fine aggregates if their weight
in moist condition found to be 4.52 kg (with tray) and the dry weight after 24
hours in oven was 4.23 kg (with tray). The weight of the tray is 0.2 kg.
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Exercise
Calculate the moisture content of the sample of coarse aggregates if their
weight in moist condition found to be 8.65 kg (with tray) and the dry weight
after 24 hours in oven was 7.16 kg (with tray). The weight of the tray is 0.5 kg.
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Table 2.6: Sieve Designation
The grading curve can be drawn from this analysis and the curve showing
cumulative percentages of the material passing the sieves. The grading curve
indicates whether the grading of a given sample conforms to that specified, or
is too coarse or too fine or too deficient in particular size. The reading of the
grading curve will indicates the followings:
a) If the actual grading curve is lower than specified grading curve, the
aggregate is coarser and segregation of mix might take place.
b) If the actual grading curve lies well above the specified curve, the
aggregate is finer and more water will be required, thus increasing the
quantity of cement also for a constant water cement ratio. Therefore, this
is uneconomical.
c) If the actual grading is steeper than specified, it indicates an excess of
middle-size particles and leads to harsh mix.
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d) If the actual grading curve is flatter than specified grading curve, the
aggregate will be deficient in middle size particles.
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Sieve # % Passing
1 in 100
3/4 in 94
1/2 in 69
3/8 in 33
No. 1 7.5
No. 8 2.5
No. 16 1
Table 2.7: Grading Limit for Course Aggregates (Derived from BS 882)
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Table 2.6: Grading Limits for Fine Aggregate (Derived from BS 882)
Figure 2.10: Typical Grading Curves for A Zone 2 Fine Aggregate and A
Graded 20 mm Coarse Aggregate
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Aggregate Graded
- Gap grading is a grading in which one or more intermediate size
fractions are omitted (limited sizes, good interlock, low permeability)
- Well graded/Combined gradation means sizes within the entire range
are in approximately equal amounts (friction at many points, excellent
interlocking, very few voids or low permeability & economical)
- Uniform gradation means a large percentage of the particles are of
approximately the same size (poor interlocking, high percentage of
voids, friction at few points of contact)
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Fineness Modulus (FM)
- The Fineness Modulus (FM) used to determine the aggregate
distribution.
- The lower the Fineness Modulus the smaller the average particle size
and the larger the fineness modulus the larger the average particle size.
- Fineness modulus is the sum of the cumulative percentage retained on
the sieves of the standard test sieves. Fineness modulus (FM) = (Cum.
percent retained / 100)
Aggregate has three dimensional of masses namely shape, size and surface
texture. Shape and surface texture are considered as external characteristic.
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The shape and surface texture of fine aggregate govern its void content and
thus affect the water requirement of mix significantly. Crushing rock produces
angular particles with sharp corners. The corners of aggregates break down
due to weathering effect and creating sub-angular particles. When the
aggregate being transported in water, the corners become completely
rounded.
Aggregate particles which have sharp edges or rough surface such as crushed
stone used more water than smooth and rounded particles to produce
concrete of same workability. About 5 – 10% of water content can be reduced
by using rounded aggregate. However, the angular aggregates will be more
difficult for them to slide across each other.Besides, the interlocking between
aggregates particle, and stronger mortar bond, for crushed aggregate is higher
than smooth or rounded aggregate in concrete with same water cement ratio.
This increase in strength may be up to 38% for concrete having-cement ratio
below 0.4. Rough texture generally improves the bonding, inter-particle friction
but more difficult to compact into a dense configuration.
a) Rounded
Full water-worn or completely shaped by attrition
or abrasion. E.g. river or sea shore gravel
b) Irregular
Naturally irregular or partly shaped by attrition and
having rounded edges. E.g. Other gravel land or dug
flint
c) Angular
Processing well defined edges formed at the
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Intersection or roughly planes faces. E.g. Crushed
rocks of all types
d) Flaky
A material of which the thickness is small relative
to other two dimensions. E.g. Laminated rock
e) Elongated
The aggregate is usually angular, is shape, and the
length is considerably larger than the other two
dimensions.
f) Flaky and Elongated
Material having the length which is considerably
larger than the width, and the width is considerably
larger than the thickness
The surface pores help in the development of good bond on account of suction
of paste into these pores. Aggregate with polished surface do not produce
such strong concrete compared to those with rough surface, The more angular
the aggregate, the more surface area it will produce, thus, result in greater
bonding.
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Activities
46
4. Sieve analysis results for aggregate sample is as follows:
Sieve size
Retained mass (kg)
(mm)
25 0
19 350.6
12.5 1370.5
9.5 2162.4
4.75 1546.7
2.36 368.8
1.18 120.5
pan 80.5
Total 6000
Plot the grain size distribution curve and classify the aggregate.
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REFERENCES
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