Sub Head 5.0: Reinforced Cement Concrete Work
Sub Head 5.0: Reinforced Cement Concrete Work
Sub Head 5.0: Reinforced Cement Concrete Work
(b) Reinforcement
5.1 MATERIALS
5.1.1 Water, cement, fine and coarse aggregate shall be as specified under respective clauses of
chapter 03 mortars and chapter 04 concrete work as applicable.
5.1.2 Fly Ash admixed cement concrete (FACC) and fly ash Blended cements in Cement Concrete
(PPCC) in RCC structures.
5.1.2.0 Fly ash Blended Cements conforming to IS 1489 (Part I) may be used in RCC structures as per
guidelines given below :
5.1.2.1 General
(i) IS 456- 2000 Code of Practice for Plain and Reinforced Concrete (as amended up to date) shall
be followed in regard to Concrete Mix Proportion and its production as under :
(a) The concrete mix design shall be done as “Design Mix Concrete” as prescribed in clause-9
of IS 456 mentioned above.
(b) Concrete shall be manufactured in accordance with clause 10 of above mentioned IS
456 covering quality assurance measures both technical and organizational, which shall
also necessarily require a qualified Concrete Technologist to be available during manufacture
of concrete for certification of quality of concrete.
(ii) Minimum M -25 grade of concrete shall be used in all structural elements made with RCC both in
load bearing and framed structure.
(iii) The mechanical properties such as modulus of elasticity, tensile strength, creep and shrinkage of
fly ash mixed concrete or concrete using fly ash blended cements (PPCs) are not likely to
be significantly different and their values are to be taken same as those used for concrete made
with OPC.
(iv) To control higher rate of carbonation in early ages of concrete both in fly ash admixed as well as
PPC based concrete, water/binder ratio shall be kept as low as possible, which shall be closely
monitored during concrete manufacture.
If necessitated due to low water/binder ratio, required workability shall be achieved by use
of chloride free chemical admixtures conforming to IS 9103. The compatibility of
chemical admixtures and super plasticizers with each set OPC, fly ash and /or PPC received from
different sources shall be ensured by trials.
(v) In environment subjected to aggressive chloride or sulphate attach in particular, use of fly ash
admixed or PPC based concrete is recommended. In cases, where structural concrete is
exposed to excessive magnesium sulphate, flyash substitution/content shall be limited to 18% by
weight. Special type of cement with low C3A content may also be alternatively used. Durability
criteria like minimum binder content and maximum water /binder ratio also need to be given due
consideration in such environment.
5.4.1 Consistency
The concrete which will flow sluggishly into the forms and around the reinforcement without
any segregation of coarse aggregate from the mortar shall be used. The consistency shall depend
on whether the concrete is vibrated on or hand tamped, it shall be determined by slump test as
prescribed in sub-head “concrete” under workability – requirement.
5.4.9.0 Regular mandatory tests on the workability of the fresh concrete shall be done to achieve the
specified compressive strength of concrete. These will be of two types
(a) Mandatory Lab, Test
(b) Mandatory Field Test
Results of Mandatory Field Test will prevail over mandatory Lab. Test.
5.4.9.1 Cube Test for Compressive Strength of Concrete - Mandatory Lab Test : Mandatory tests
shall be carried out as prescribed in Appendix A of Chapter 5.
5.4.9.2 Additional Test : Additional test, if required, shall be carried out as prescribed in Appendix B of
Chapter 5.
5.4.9.3 Slump Test : This test shall be carried out as prescribed in sub-head 4 of concrete.
5.4.9.4 Visual Inspection Test : The concrete will be inspected after removal of the form work
as described in para 5.4.7.2 The question of carrying out mandatory test or other tests described
in Appendix A and B (para 5.4.9.1 and 5.4.9.2) will arise only after satisfactory report of visual inspection.
However, the hardened concrete may be accepted after carrying out suitable remedial measures to
the satisfaction of the Engineer-in-Charge at the risk and cost of the contractor.
5.4.10.1 Mandatory Lab. Test : For concrete sampled and tested as prescribed in Appendix A of
Chapter 5, the following requirement shall apply.
5.4.10.2 Out of six sample cubes, three cubes shall be tested at 7 days and remaining three cubes at 28
days.
In case the actual average strength of sample accepted in the above para is lower than the specified
or higher by more than 15% then 28 days’ test shall have to be carried out to determine the compressive
strength of concrete cubes.
(b) If the actual average strength of accepted sample exceeds specified strength by more than 30%
the Engineer-in-Charge, if he so desires, may further investigate the matter. However, if
the strength of any individual cube exceeds more than 30% of specified strength, it will be
restricted to 130% only for computation of strength.
(c) If the actual average strength of accepted sample is equal to or higher than specified strength
upto 30% then strength of the concrete shall be considered in order and the concrete shall be
accepted at full rates.
(d) If the actual average strength of accepted sample is less than specified strength but not less than
70% of the specified strength, the concrete may be accepted at reduced rate at the discretion of
Engineer-in-Charge (see para 5.4.13.2).
(e) If the actual average strength of accepted sample is less than 70% of specified strength,
the Engineer-in-Charge shall reject the defective portion of work represented by sample and
nothing shall be paid for the rejected work. Remedial measures necessary to retain the structure
shall be taken at the risk and cost of contractor. If, however the Engineer-in-Charge so desires,
he may order additional tests (See Appendix B of Chapter 5) to be carried out to ascertain if the
structure can be retained. All the charges in connection with these additional tests shall be
borne by the contractor.
(b) At least 18 standard cubes necessary for formation of one specimen of specified mix, shall be
cast by site staff well in advance. From these 18 cubes any 3 cubes may be selected
at random to be tested for crushing strength of 7 days. The crushing strength obtained
should satisfy the specified strength for the mix as per specification or agreement. If the
strength is satisfactory then the remaining cube will form the standard samples for calibration
of rebound hammer. In case of failure, the site staff should totally reject the samples and
remove them also and then make another set of samples by fresh mixing or
alternatively, out of the remaining 15 cubes, 3 cubes will be tested on 28 days. If the
28 days’ tests are found satisfactory then remaining 12 cubes will form the standard sample
for calibration at 28 days’ strength otherwise all samples shall be rejected and whole
procedure repeated to form a fresh specimen. All the results shall be recorded in a register.
(c) No concreting will be allowed unless the standard specimen cubes are obtained.
The criteria for acceptance and calibration of hammer will be 28 days’ strength. The 7 days’
strength is only to facilitate the work to start.
(e) Frequency: it will be once in each quarter or as per the direction and discretion of Engineer- in-
Charge. Whenever the acceptance criteria is changed or concrete mix or type of cement is
changed or Engineer-in-Charge feels it necessary for recorded reasons with the approval of the
authority according to technical sanction, fresh specimen shall be prepared.
5.8.1.2 Determination of the proportions by weight of cement, aggregates and water shall be based on
design of the mix.
5.8.1.3 As a trial the manufacturer of concrete may prepare a preliminary mix according to provisions of
SP: 23. Reference may also be made to ACI 211.1-77 for guidance.
5.8.1.4 Mix design shall be tried and the mix proportions checked on the basis of tests conducted at a
recognized laboratory approved by the Engineer-in-Charge.
5.8.1.5 All concrete proportions for various grades of concrete shall be designed separately and the mix
proportions established keeping in view the workability for various structural elements, methods of
placing and compacting.
5.8.1.6 Before using an admixture in concrete, its performance shall be evaluated by comparing
the properties of concrete with the admixture and concrete without any admixture. Chloride content
of admixture should be declared by the manufacturer of admixture and shall be within limits stipulated
by IS:9103.
(b) Any individual test result complies with the appropriate limits in col. 3 of Table 5.6.
5.8.3.2 Flexural Strength : When both the following conditions are met, the concrete complies with the
specified flexural strength.
(a) The mean strength determined from any group of four consecutive test results exceeds the
specified characteristic strength by at least 0.3 N/mm2 .
(b) The strength determined from any test result is not less than the specified characteristic strength/
0.3 N/mm2.
5.8.3.3 Quantity of Concrete Represented by Strength Test Results : The quantity of concrete
represented by a group of four consecutive test results shall include the batches from which the first and
last samples were taken together with all intervening batches.
For the individual test result requirements given in col 3 of Table 5.6 or in item (b) of 5.8.3.2. Only the
particular batch from which the sample was taken shall be at risk.
Where the mean rate of sampling is not specified the maximum quantity of concrete that four
consecutive test results represent shall be limited to 60 m3.
5.8.3.4 If the concrete is deemed not to comply pursuant to 5.8.3 the structural adequacy of the parts
affected shall be investigated and any consequential action as needed shall be taken.
5.8.3.6 Concrete is liable to be rejected if it is porous or honey-combed, its placing has been interrupted
without providing a proper construction joint, the reinforcement has been displaced beyond the
tolerances specified, or construction tolerances have not been met. However, the hardened
concrete may be accepted after carrying out suitable remedial measured to the satisfaction of the
Engineer-in- Charge.
5.8.4.2 Actual cement content in each grade of concrete for various conditions of variable shall
be established by design mixes within the limits specified in para 5.8.4.1 above.
5.8.5.2 Due consideration shall be given to the workability of the concrete thus produced. Slump shall be
controlled on the basis of placement in different situations. For normal methods of placing
concrete, maximum slump shall be restricted to 100 mm when measured in accordance with IS 1199.
Specified Grade Mean of the Group of 4 Non- Individual Test Results in N/mm3
Overlapping Consecutive Test Results
in N/mm3
(1) (2) (3)
M15 fck + 0.825 x established standard fck-3 N/mm2
deviation (rounded off to nearest 0.5
N/mm2)
or
fck +3 N/mm2
Whichever is greater
M20 fck + 0.825 x established standard fck-4 N/mm2
or deviation (rounded off to nearest 0.5
above N/mm2)
or
fck +4 N/mm2, Whichever is greater
NOTE – In the absence of established value of standard deviation, the values given in
Table may be assumed, and attempt should be made to obtain results of 30 samples as
early as possible to establish the value of standard deviation.
5.8.6.2 For any change in quality/ quantity in the ingredients of a particular concrete, for which mix has
been designed earlier and approved by the Engineer-in-Charge, the mix has to be redesigned
and approval obtained again.
5.9.1.2 Cement : Cement used for concrete shall be in accordance with the requirements of IS 456.
.
5.9.1.3 Mineral Admixtures : Use of mineral admixtures shall be permitted in accordance with
the provisions of IS 456.
The sampling may be carried out jointly by the purchaser and the supplier with its frequency mutually
agreed upon. However, it will not absolve the supplier of his responsibility from supplying in concrete as
per the requirement given in this standard or otherwise agreed to where so permitted in the standard.
5.9.3.2 Workability : The test for acceptance is to be performed upon the producer’s delivery vehicle
discharge on site or upon discharge into the purchaser’s vehicle. lf discharge from the producers’ vehicle is
delayed on site due to lack of preparedness on behalf of the purchaser then the responsibility passes to
the purchaser after a delay of more than 30 min.
The workability shall be within the following limits on the specified value as appropriate:
Slump ± 25 mm or 1/3 of the specified value, whichever is less.
Compacting factor : ± 0.03, where the specified value is 0.90 or greater,
± 0.04, where the specified value is less than 0.90 but more than 0.80,
± 0.05, where the specified value is 0.80 or less.
Flow table test may be specified for concrete, for very high workability (see IS 9103)
Acceptance criteria for spread (flow) are to be established between the supplier and the purchaser.
(ii) Unless otherwise agreed between the parties involved, the minimum testing frequency to
be applied by the producer in the absence of a recognized ready-mixed concrete industry method
of production control should be one sample for every 50 m3 of production or every 50
batches, whichever is the greater frequency. Three test specimens shall be made up for each
sample for testing at 28 days (see also IS 456).
5.9.7.1 Forward control : Forward control and consequent corrective action are essential aspects of
quality control. Forward control includes the following.
(i) Control of purchased material Quality
(b) Test on specimens made form samples collected at placement location shall be considered
as field test specimens and results therefrom shall be the criterion of concrete strength. Test
in specimens made from samples at the batch plant shall only be taken as guidelines test.
Only in the case of doubtful result, the Engineer-in-Charge may refer to such guideline results
for deciding on the quality of concrete.
(c) For truck mix concrete and shrink mix concrete guideline test specimens shall be made from
samples collected at discharge location from mixing trucks. For this purpose first and
last
15% of the load shall be omitted while collecting samples.
(d) Frequency of sampling shall be as given below in Table 5.8 for each grade of concrete
of different workability’s and for each type of specimens (field test specimens and guideline test
specimens) for conducting 28 days crushing strength tests.
TABLE 5.8
Each sample shall be of adequate quantity so that a minimum of 3 specimen cubes can be
made test of the sample in accordance with IS 516.
(e) All test specimens shall be made compacted cured and tested in compliance with IS 516 and
test result interpreted in accordance with IS 456 for acceptance of concrete strength,
field specimens test results shall not be less than values given in Table 5.6.
(g) For each grade of concrete and for all workability conditions with different water –
cement ratios and compositions of admixtures, preliminary test shall be conducted for
crushing strength on finalization to design mix for each type of concrete. Such test shall be
conducted both at 7 days and 28 days under laboratory conditions. Six test specimens shall be
made for
7 days test and six test specimens shall be made for 28 days test.
Average of the six test results of different periods shall not be less than those specified in
Table 5.5.
(h) Crushing strengths on cubes shall also be conducted during the process of finalization
of concrete design mix. Frequency and number of such tests shall be as per
Mix of requirements of concrete manufacturer.
(i) All test specimens for conducting crushing strength shall be properly labeled for identification
indicating:-
(i) Date of making specimen
(ii) Grade of concrete
(iii) Placement location exact
(iv) Purchasers order number
(j) In addition to crushing strength test on concrete, the Engineer-in-Charge may call for other
tests on hardend concrete. The placement contractor and the manufacturer of concrete shall
comply with all such instructions.
(b) Interpretation of rebound hammer, Windsor Probe and Pulse velocity test results shall rest
with the Engineer-in-Charge.
(c) Core test, if ordered by the Engineer-in-Charge, shall be done in accordance with IS
516. Samples for such test shall be taken from locations to be identified by the Engineer-in-
Charge and such samples shall be collected in compliance with IS:1199.
(d) If felt necessary, the Engineer-in-Charge may instruct load testing for any part of the structure
based on doubtful concrete strengths. Such test shall be carried out as per details to
be provided by the Engineer-in-Charge in consultation with the structural consultants.
(f) All test conducted at the filed laboratory shall be carried out by qualified technicians
employed by the concrete manufacturer/ concrete placement contractor, in presence of
authorized representative of the Engineer-in-Charge. All test reports and observation reports
shall be jointly signed by the Engineer-in-Charge authorized representative and
the technician conducting such test.
(g) Engineer-in-Charge shall alone decide where such tests are to be conducted. He may
instruct tests to be conducted at laboratories other than the field laboratory and such
instructions shall be followed without claiming extra charges on this account.
(h) The Concrete Manufacturer/ Placement contractor shall set up a laboratory at this own
expense which shall have facilities, for conducting all necessary field test on materials and
field and laboratory test on concrete. The laboratory shall be staffed by the concrete
Manufacturer/ Placement Contractor with qualified and experienced scientists and
technicians.
A-0 One sample (consisting of six cubes 15x15x15 cm shall be taken for every 20 cum or part thereof
concrete work ignoring any part less than 5cum or as often as considered necessary by the Engineer-
in-Charge. The test of concrete cubes shall be carried out in accordance with the procedure as
described below. A register of cubes shall be maintained at the site of work in Appendix C. The casting
of cubes, concrete used for cubes and all other incidental charge, such are curing, carriage to the testing
laboratory shall be borne by the contractors. The testing fee for the cubes, if any, shall be borne by the
department.
The moulds for test specimens shall be made of non-absorbent material and shall be
substantially strong enough to hold their form during the moulding of test specimens. They shall not
vary from the standard dimensions by more than one percent. The moulds shall be so constructed
that there is no leakage of water from the test specimen during moulding. All the cube moulds for
particular site should, prior to use, be checked for accuracy in dimensions and geometric form and such
test should at least be made once a year.
Each mould shall be provided with a base plate having a plane surface and made of non-absorbent
material. This plate shall be large enough in diameter to support the moulds properly without leakage.
Glass plates not less than 6.5mm thick or plain metal not less than 12mm thick shall be used for this
purpose. A similar plate shall be provided for covering the top surface of the test specimen when
moulded.
Note: Satisfactory moulds can be made from machine or steel castings, rolled metal plates or
galvanized.
When the job concrete is placed by vibration and the consistency of the concrete is such that the test
specimens cannot be properly moulded by hand rolling as described above, the specimens shall
be vibrated to give a compaction corresponding to that of the job concrete. The fresh concrete
shall be placed in mould in two layers, each approximately half the volume of the mould. In placing each
scoopful of concrete the scoop shall be moved around the top edge of the mould as the concrete
there slides from it, in order to ensure a symmetrical distribution of concrete within the mould.
Either internal or external vibrators may be used. The vibration of each layer shall not be
continued longer than is necessary to secure the required density. Internal vibrators shall only be
used when the concrete is required to be compacted in layers. In compacting the first layer, the
vibrators shall not be allowed to rest on the bottom of the mould. In placing the concrete for top extent
that there will be no mortar loss during vibrations. After vibrating the second layer enough concrete shall
be added to bring level above the top of the mould. The surface of the concrete shall then the struck off
with a trowel and covered with a glass or steel plate as specified above. The whole process of moulding
shall be carried out in such a manner as to preclude the alteration of water-cement ratio of the
concrete by loss of water, either by leakage for the bottom or over flow from the top of the mould.
Note:- It is suggested that the storage box be made of 25 mm dressed tongued and grooved timber,
well braced with battens to avoid warping. The box should be well painted inside and outside
and should be provided with a hinged cover and padlock.
The test specimen shall be removed from the moulds at the end of 24 hours and stored in a moist
condition at a temperature within 24ºC to 30ºC until the time of test. If storage in water is desired,
a saturated lime solution shall be used.
A-1.5 Testing
The specimens shall be tested in accordance with procedure as described below:
(b) Compression tests shall be made immediately upon removal of the concrete test specimen from
the curing room i.e. the test specimen shall be loaded in damp condition. The dimensions of the
test specimens shall be measured in mm accurate to 0.5 mm.
(c) The metal bearing plates of the testing machine shall be placed in contact with the ends of the
test specimens. Cushioning materials shall not be used. In the case of cubes, the test specimen
shall be placed in the machine in such a manner that the load is applied to sides of the
specimens as cast. An adjustable bearing block shall be used to transmit the load to the test
specimen. The size of the bearing block shall be the same or slightly larger than that of
test specimen. The upper or lower section of the bearing block shall be kept in motion as the head
of the testing machine is brought to a bearing on the test specimen.
(d) The load shall be applied axially without shock at the rate of approximately 140 kg. per sq.cm.
per minute. The total load indicated by the testing machine at failure of test specimen shall be
recorded and the unit compressive strength is calculated in kg per sq. cm. using the area
computed from the measured dimension of the test specimen. The type of failure
and Appearance of the concrete shall be noted.
B-0 In case the concrete fails when tested as per the method prescribed in Appendix A, one or more of
the following check tests may be carried out at the discretion of Engineer-in-Charge to satisfy the
strength of the concrete laid. All testing expenditure shall be borne by the contractor, the number
of additional tests to be carried out shall be determined by the Engineer-in-Charge. He shall be the
final authority for interpreting the results of additional test and shall decide upon the acceptance or
otherwise. His decision in this regard shall be final and binding. For the purpose of payment, the
Hammering test results only shall be the criteria. Some of the tests are outlined below:-
The points from which cores shall be taken shall be representative of the whole concrete and at least
three cores shall be obtained and tested. If the average of the strength of all cores cut from the structure
is less than the specified strength, the concrete represented by the cores shall be liable to rejection and
shall be rejected if a static load test (B-5) either cannot be carried out or is not permitted by
the Engineer-in-Charge.
(b) For members spanning between two supports the deflection measured immediately on
application of the test load for deflection is to be not more than 1/500 of the effective span limits
shall be agreed upon before testing cantilevered portions of structure.