Download additional sections published on 28-5-2014

KERALA PUBLIC WORKS DEPARTMENT Quality Manual for Building, Road and Bridge Works

Sub: PWD Manual Revision Preparation of Quality Manual Circulating

additional 10 sections draft prepared by the Working Group reg. Ref: 1. G.O (P) No.13/2012/PWD dated 1.2.2012.

2. G.O (Rt) No. 1784/2012/PWD dated 20-10-2012.

A draft Quality Manual for PWD is under preparation by the

Working Group constituted by the Chief Engineer (Design & Administration) on

02-07-2013 for this purpose. The draft manual is being prepared in three parts

viz., Part A Buildings (14 sections), Part B Roads (10 sections) and Part C

Bridges & Culverts (14 sections). Eight (8) draft sections from Part A, six (6)

draft sections from Part B and Eight (8) from Part C has already published in

the web site in two stages, inviting suggestions/modifications/additions from

the field.

Another 10 draft sections Four (4) from Part A and Six (6) from

Part C are herewith published for review and suggestions from the field officers.

Suggestions for the improvement of the additional draft sections may please be

forwarded to Sri. T. Santhosh Kumar, Director (I&QC), Office of the Chief

Engineer (Design), Thiruvananthapuram 695 033 by post or by e-mail to

[email protected], to reach by not later than 10th June 2014.

The whole-hearted support and co-operation of all concerned is requested. For and on behalf of Chief Engineer, Buildings & Convener, Technical committee (Manual revision)

T. Santhosh Kumar Director (I&QC) Attachments: Part A Draft sections 600, 1100, 1200 & 1300. Part B Draft sections 4500, 5000, 5100, 5200, 5300 & 5400.

600 CONCRETE CONSTRUCTION

601 GENERAL

a) This Section consists of quality control aspects of concrete work including the materials required such as cement, fine and coarse aggregates, water, admixtures reinforcing steel and form work.

b) The quality requirements for cement, fine aggregate and water used for masonry and other cement related works shall also comply with the requirements listed in

this section.

602 CEMENT

The quality of various cements is to be determined on the basis of its conformity to the

performance characteristics given in the respective BIS Specification for that cement.

Any trade-mark or any trade name indicating any special features not covered in the

standard or any qualification or other special performance characteristics sometimes

claimed/indicated on the bags or containers or in advertisements alongside the

Statutory Quality Marking or otherwise have no relation whatsoever with the

characteristics guaranteed by the Quality Marking as relevant to that cement.

602.1 Cement Identification

Prior to carrying out a concrete mix design, cement identification should be recorded.

Cement Identification chart shall be prepared with the following identification

markings on the cement bag.

i) Name of cement company ii) Place of the factory iii) Type of cement (OPC, PPC etc.)

iv) Grade of cement (28 day compressive strength) with the relevant BIS code number v) Date of manufacture 602.2. Requirements

a) The various types of cement shall comply with the respective BIS code as specified below:

i) Ordinary Portland cement 33 grade - IS: 269 ii) Ordinary Portland cement 43 grade - IS: 8112 iii) Ordinary Portland cement 53 grade - IS: 12269 iv) Rapid hardening Portland cement - IS: 8041 v) Portland pozzolana cement - IS: 1489 (Part-1) vi) Portland blast furnace slag cement - IS: 455 vii) Sulphate resistant Portland cement - IS: 12330

b) Cement shall be delivered to the Site in sealed and branded bags, or in the manufacturers containers, bearing the manufacturers name, cement type and date of manufacture, in batches not exceeding 100 tons.

c) Cement shall be stored at the site in such a manner, as to prevent its deterioration, intrusion of moisture and foreign matter. It must be kept dry at all times. Immediately upon arrival at the Site, the Contractor shall store the cement in: i. Bins or silos designed for the purpose. It shall be tight and provide for free

movement to discharge opening, or ii. Dry, weather tight and properly ventilated structures with floors raised a

minimum of 450 mm above the ground with adequate provision to prevent absorption of moisture.

d) All storage facilities shall be subject to the approval of the Engineer, and shall be such as to permit easy access for inspection and identification. Prolonged storage of cement at site is to be avoided. An indicative rate of such deterioration is given in table 600-1.

Table 600-1: Rate of deterioration of cement against storage period

Period of storage of cement Minimum expected reduction in

strength at 28 days (%)

Fresh 0

3 months 20

6 months 30

1 year 40

2 years 50

e) Cement used in the Works shall be free flowing and free from lumps. f) In no case shall bagged cement be stored in stacks more than eight bags high. g) A free passage of at least 1 m shall be left between the cement and the side walls of

the structure. h) Different types of cement shall be kept in clearly marked separate storage facilities. i) Cement delivered to Site in drums or bags by the supplier or manufacturer shall be

stored in the drums or bags until used in the Works. j) Any cement in drums or bags which have been opened shall be used immediately. k) It is good practice to move cement out of the storage shed using the firstin-first-

out scheme. l) Cement that has partially or fully caked in storage will not be permitted in work

and shall be immediately removed from the storage area. Any bag or package or sample of cement which has been damaged, or rebagged or in any way has deteriorated shall be rejected either as an individual bag or package or as the whole consignment in which such bag, package or sample is contained, as advised by the Engineer.

m) Where site limitations preclude the storage of cement in site, cement shall be stored at a central location and shall be delivered daily as required to specific job

sites. n) The Contractor shall provide weighing machines which shall be kept permanently

in each shed for checking the weight of the bags or barrels of cement. The weighing machines shall be calibrated by an independent agency. The Engineer shall have access at all times to the cement storage sheds.

o) During transport and storage, the cement shall be fully protected from all weather elements.

p) Any consignment of cement not used within two months from the date of manufacture and cement which in the opinion of the Engineer is of doubtful quality shall not be used in the works, until it has been retested and test result sheets showing that it complies in all respects with the specification and relevant standards have been delivered to the Engineer.

q) Cement stored for longer than 28 days shall be tested prior to use to check for deterioration, and any cement which fails the test shall not be used in the works.

602.3. Sampling and Testing

a) The Contractor shall produce manufacturers certificate for each supply of cement. b) If the Engineer is in doubt about the quality of cement used by the Contractor, the

cement must be subjected to various tests stipulated in BIS specifications.

c) Samples used for cement testing shall be selected from an intimate mixture of approximately equal portions of cement selected from at least 12 different bags or packages when the cement is not loose, or 12 different positions in a heap or heaps when the cement is loose.

d) The minimum weight of the final sample taken should be 5 kg and shall be stored in an airtight container until testing.

e) Unless specified, the following tests shall be carried out for cement in comply with respective Indian Standards as specified in table 600-2.

Table 600-2: Test for cement

Test Code Permissible value Frequency

Fineness IS: 4031

(Part 1, 2 & 15)

Specific surface not less than 225 m2/kg

1 test for 10 tonnes of cement (Same grade and

brand)

Soundness IS: 4031 (Part 3)

Not to exceed 10mm in Lechatelier mould

- do -

Setting time IS: 4031

(Part 1)

Initial setting time>30 mins.

Final setting time

603. AGGREGATES

This part covers the quality control requirements for aggregates derived from crushed

or uncrushed derived from natural sources, such as river terraces, river beds, rocks,

boulders, gravels, for use in production of mortar or concrete for normal structural

purposes including mass concrete works.

603.1. Requirements

a) Fine aggregate consist of natural clean sand, gravel, manufactured sand produced by crushing rock/gravel or a combination of the above, conforming to the requirements of physical and chemical properties stipulated in BIS codes and subject to Engineer's acceptance.

b) Coarse and fine aggregates shall consist of tough, hard, durable and uncoated particles containing no harmful material in quantities sufficient to adversely affect the concrete or reinforcing steel, and shall contain no materials likely to cause staining or otherwise disfigure the concrete surface.

c) Coarse and fine aggregates which shall be obtained from a source approved by the Engineer, shall comply with the requirements of BIS codes and subject to Engineers acceptance. If required by the Engineer, the aggregates shall be washed with water.

d) The nominal maximum size of coarse aggregate shall be as large as possible within the limits specified but in no case greater than of the minimum thickness of the member or the minimum clear spacing between individual reinforcing bars or wires.

e) The gradation of fine aggregate for concrete and mortar shall be in accordance with the gradation designations in IS: 383 and subject to Engineers acceptance.

f) Each batch of aggregate delivered to the site shall be kept separate from previous batches, and shall be stored to allow for inspection and tests to be carried out.

g) The storage area for the clean washed sand shall be shaded from the direct rays of the sun and shall be screened for protection from dust. The area in the neighbourhood of stockpile/mixing plant shall be watered as necessary, to reduce the rising of dust.

h) The aggregates shall be properly stocked and labelled without intermingling as classified at any storage area.

i) No aggregate deliveries shall be made to the site until the Engineer has approved the samples as complying with the specification.

j) The Contractor shall provide a means of storing aggregate at each point where concrete is made such that: i) Each nominal size of coarse aggregate and the fine aggregate shall be kept

separated at all times. ii) Building stockpiles are to prevent harmful segregation and breakage. iii) Stockpiles shall be on hard and clean surfaces with not more than 5% slope. iv) Contamination of the aggregates by the ground or other foreign matter shall be

effectively prevented at all times. v) Each heap of aggregate shall be capable of draining freely. vi) Stockpiles shall be protected from direct sunlight. vii) Intermingling of aggregates shall not be approved. viii) Unloading aggregate are to prevent harmful segregation and breakage.

k) The preparation, location and size of any stockpiles and the methods of segregation shall be approved by the Engineer.

l) Wet aggregates in stockpiles shall be taken frequently to determine the moisture content and the amount of water to be added to the mix.

603.2. Sampling and Testing

a) The Contractor shall provide samples of both fine and coarse aggregate to the Engineer, in accordance with the requirements of IS: 2430 for testing at least two weeks before delivering to the site.

b) All samples shall be taken in the presence of the Engineer. c) Samples of aggregates shall be tested in accordance with the requirements of

IS: 2386 as specified in Tables 600-3 and 600-4. Table 600-3: Test for coarse aggregates

Test Code Frequency

Gradation IS: 2386 (Part 1) 3 samples for each quarry source

Flakiness index IS: 2386 (Part 1) - do -

Deleterious constituents

IS: 2386 (Part 2) If in doubt, one test

Water absorption

IS: 2386 (Part 3) Once for each source of supply

Aggregate impact value

IS: 2386 (Part 4) One test per source of supply

Soundness IS: 2386 (Part 5) - do -

Table 600-4: Test for fine aggregates

Property Code Frequency

Gradation IS: 2386 (Part 1) 3 samples for each quarry source

Deleterious constituents

IS: 2386 (Part 2) If in doubt, one test

603.3. References:

Specifications:

IS: 383 Specification for coarse and fine aggregates from natural sources

for concrete

Sampling and Testing:

IS: 2430 Methods for Sampling of Aggregates

IS: 2386 Methods of Tests for Aggregate for Concrete

Part I Particle size and shape

Part II Estimation of deleterious materials and organic impurities

Part III Specific gravity, density, void, absorption and bulking

Part IV Mechanical properties

Part V Soundness

Part VI Measuring mortar making properties of fine aggregate Part VII Alkali aggregate reactants

Part VIII Petrographic examinations

604. WATER

Water used for concrete mixes, washing of aggregates and equipment, wetting of

surfaces or ponding during curing or for wetting formwork and washing reinforcement

shall conform to the following.

604.1 Requirements

a) Water used for mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete or steel.

b) The potable water is suitable for use in concrete, while other water origin such as underground water, natural surface water shall be tested to prove that its quality shall conform to water quality requirements of BIS and chemical limitations listed in Table 1 of IS: 456.

c) In case of doubt regarding development of strength, the suitability of water for producing concrete shall be ascertained by the compressive strength and initial setting time tests.

d) The pH of water used in concrete works shall be as shown in Table 4.2 of IS: 456. e) Temperature of water for concrete shall not be less than 5C and not more than

40C f) Water may be cooled to not less than 5C by the gradual addition of chilled water or

ice as follows: (i) no ice particles shall be present in the mix (ii) alternatively, flaked ice may be used

g) Every effort should be made to protect water pipes and tanks from the sun; e.g., burying, shading, insulation or painting white.

h) Mixing or curing of concrete with sea water is not recommended because of presence of harmful salts in sea water.

604.2 Supply and Storage

a) The Contractor shall make his own arrangements and obtain the approval of the Engineer for the supply of water.

b) Storage of water should be such that contamination is prevented from occurring. Any measures taken to avoid contamination of the water shall be to the approval of the Engineer.

604.3 Sampling and Testing

a) Whenever required to do so by the Engineer, the Contractor shall take samples of the water being used, or which it is proposed to use, for mixing concrete and test

them for quality. b) The sample of water taken for testing shall represent the water proposed to be used

for concreting, due account being paid to seasonal variation. The sample shall not receive any treatment before testing other than that envisaged in the regular supply of water proposed for use in concrete. The sample shall be stored in a clean container previously rinsed out with similar water.

c) Average 28 days compressive strength of at least three 150 mm concrete cubes prepared with water proposed to be used shall not be less than 90 percent of the

average of strength of three similar concrete cubes prepared with distilled water. The cubes shall be prepared, cured and tested in accordance with the requirements of IS: 516.

d) The initial setting time of test block made with the appropriate cement and the water proposed to be used shall not be less than 30 min and shall not differ by 30min from the initial setting time of control test block prepared with the same cement and distilled water. The test blocks shall be prepared and tested in accordance with the requirements of IS: 403 1 (Part 5).

e) The pH value of water shall not be less than 6.

f) No source of water shall be approved until the required tests have demonstrated its suitability for use in concrete.

g) The use of water from a municipal or government supply does not preclude the requirement for testing.

h) If the quality of water is in doubt, it shall be tested as indicated in table 600-5. Table 600-5: Quality control tests for water for use in concrete

Sl.

No. Test Code

Permissible value Minimum Frequency of

sampling

1 Suspended

matter

IS: 3025

(Part 17) 2000 mg/litre

Water from each source

before commencement of

work and thereafter every

three months till completion

of work

2 Organic

contents

IS: 3025

(Part 16) 200 mg/litre - do -

3 Inorganic

contents

IS: 3025


4 Sulphates

(as SO2)

IS: 3025


5 Chlorides

(as Cl)

IS: 3025

(Part 32)

2000 mg/litre (PCC)

500 mg/litre (RCC) - do -

604.4 References

IS: 3025 Methods of sampling and test (physical and chemical) for water and

waste water

605 ADMIXTURES

605.1 General

a) Admixtures are materials added to the concrete during mixing for the purpose of altering the properties of the concrete mix.

b) Chemical and air-entraining admixtures including superplasticizers, solid or liquid or emulsion may be added to cement concrete at the time of mixing so as to achieve the desired property in concrete, in the plastic or hardened state.

c) Approval of admixtures shall be subject to extensive trials to demonstrate the suitability, adequacy of dosing arrangements and performance.

d) The manufacturer or supplier shall furnish a series of at least ten trial mixes which clearly indicate that the use of the admixture has consistently manifested the required properties of concrete including absorption, permeability and poring values.

605.2 Type of Admixtures

a) Mineral Admixtures: A material other than water, aggregates, cement and additives like pozzolana or slag used as an ingredient of concrete and added to the batch immediately before or during its mixing to modify one or more of the properties of concrete in the plastic or hardened state.

b) Fibre Reinforcement Admixtures: Fibres shall serve as secondary reinforcement for concrete, and to protect concrete from stresses which cause cracking initially after placement.

c) Accelerating Admixture or Accelerator: An admixture when added to concrete, mortar or grout, increases the rate of hydration of cement, shortens the time of set, or increases the rate of hardening or strength development.

d) Retarding Admixture or Retarder: An admixture which delays the setting of cement paste, and hence of mixtures, such as mortar or concrete containing cement.

e) Water Reducing Admixture or Workability Aid: An admixture which either increases workability of freshly mixed mortar or concrete without increasing water content or maintains workability with a reduced amount of water.

f) Air-Entraining Admixtures: An admixture for concrete or mortar which causes air to be incorporated in the form of minute bubbles in the concrete or mortar

during mixing, usually to increase workability. g) Superplasticizing Admixtures: An admixture for mortar or concrete which

imparts very high workability or allows a large decrease in water content for a given workability.

h) Retarding Superplasticizing Admixture: Superplasticizing admixture that imparts prolonged workability retention and retards setting.

605.3 Requirements

a) Admixtures shall comply with the requirements of IS: 9103. In addition to the standard requirements for the approval of materials, approval of admixtures shall be subject to extensive trials to demonstrate the suitability, adequacy of dosing arrangements and performance, when a proven history of performance can be provided to the satisfaction of the Engineer.

b) Concrete made with admixtures when compared with identical concrete made

without the admixture shall conform to the requirements appropriate to the type of admixture given in Table 1A and Table 1B of IS: 9103.

c) The methods of use and the quantities of admixture used shall be in accordance with the manufacturers instruction and subject to the Engineers approval after evaluation in trial mixes and shall in no way limit the Contractors obligations under the Contract to produce concrete with the specified strength, workability and durability.

d) Admixtures should not impair durability of concrete nor combine with the

constituent to form harmful compounds nor increase the risk of corrosion of reinforcement.

e) The relative density of liquid admixtures shall be checked for each drum containing admixtures and compared with the specified value before acceptance.

f) If two or more admixtures are used simultaneously in the same concrete mix, data should be obtained to assess their interaction and to ensure their compatibility.

g) A report of the effects of accidental overdose of the admixture and the remedial measures to be taken if an overdose occurs shall be provided by the Contractor to the Engineer.

h) No admixtures containing chlorides shall be used. In particular, the use of acceleration admixtures containing calcium chloride shall not be used.

i) The use of the admixtures shall be controlled; i.e., strict quality control to ensure correct dosages as prescribed by the manufacturer and justified by trial mixes to be used. A calibrated dispenser or flow meter shall be used to for the addition of the admixture.


a) Liquid admixture shall be agitated thoroughly prior to sampling. Grab (individual) samples taken for testing shall represent not more than 9 000 litres of admixture and shall have a volume of at least one litre.

b) A minimum of four grab samples shall be taken. Composite samples shall be prepared by thoroughly mixing the grab samples selected and the resultant mixture sampled to provide at least 4 litres for quality tests.

c) Grab samples taken for tests shall represent not more than 2 tonnes of admixture and shall weigh at least 1 kg. A minimum of 4 grab samples shall be taken and composite sample shall be prepared by thoroughly mixing the four grab samples. The resultant mixture sampled shall provide at least 2.5 kg from the composite sample. Grab samples shall be taken from different locations well distributed throughout the quantity to be represented.

d) Samples of packed admixtures shall be obtained in the same manner as described in IS: 3535.

e) Samples shall be packed in moisture proof, airtight containers. f) The test for admixtures shall be done as per the procedure described in IS:

9103. g) The chloride content of admixtures shall be independently tested for each batch

before acceptance. 605.5 References:

IS: 9103 Concrete Admixtures - Specifications IS: 6925 Methods of test for determination of water soluble

chlorides in concrete admixtures

606. REINFORCING STEEL

606.1 General

This part includes the quality aspects of tension, compression, and temperature

reinforcing steel, including welded wire fabric. The work includes furnishing,

fabrication, and placement of reinforcement for cast-in-place concrete, including bars,

welded wire fabric, ties, and supports.

606.2 Requirements

a) All reinforcement shall be free from loose mill scales, loose rust and coats of paints, oil, mud or any other substances which may destroy or reduce bond. Sand blasting or other treatment is recommended to clean the reinforcement.

b) Special precautions like coating of reinforcement may be required for reinforced concrete elements in exceptional cases and for rehabilitation of structures.

c) The Contractor shall submit the manufacturers records of chemical and physical properties of each batch of billet steel bars and a certificate that the respective material furnished meets the requirements for the steel reinforcement specified. The manufacturers records shall include certificates of chemical analysis, tensile and bend tests of the reinforcement.

606.2.1 Reinforcing Bars

a) Reinforcing steel shall consist of Mild Steel (MS), Cold Twisted Deformed (CTD) or Thermo Mechanically Treated (TMT), of various grades and definitive properties as adopted by the relevant BIS as given in table 600-6.

Table 600-6: Grades of reinforcing steel

Type Code Grade

designation

MS IS: 432 Fe250

CTD, TMT IS: 1786 Fe415, Fe500,

Fe550

b) The typical cross sections of the bars shall be as shown below:

Fig. 606-1: Typical cross sections of MS, CTD and TMT bars.

c) If the steel has excessive surface rust, dust or other deleterious material then it shall be sand blasted. Sand for blasting shall not contain materials deleterious to the durability of the reinforcement or concrete.

d) All reinforcement shall be pressure washed with fresh water after erection and immediately before placing concrete.

606.2.2 Welded Steel Wire Fabric

a) Steel fabric reinforcement shall comply with the requirements of IS: 1566 and shall be delivered to site in flat mats.

b) Welded intersections shall not be spaced more than: i) 300 for plain round bars ii) 400 mm apart for deformed high yield bars in direction of calculated stress

except when used as stirrups. 606.2.3 Tie Wire

a) Tie wire shall conform to the requirements of IS: 280. b) Tie wires shall be black annealed mild steel having diameter not less than 1mm.

606.3 Storage and Handling

a) On delivery, bars in each lot shall be legibly tagged by the manufacturer. b) Storage of reinforcement shall be on suitable structures a minimum of 450 mm

above the ground surface to prevent damage and accumulation of dirt, rust and other deleterious matter.

c) Storage facilities shall be such as to permit easy access for inspection and identification.

d) Reinforcement bundles shall be clearly tagged with bar schedule and bar mark reference.

e) The reinforcement shall not be roughly handled, dropped from a height, or subjected to shock loading or mechanical damage.

f) Steel reinforcing bars shall be kept clean and shall be free from pitting, loose rust, mill scale, oil, grease, earth, paint, or any other material which may impair the bond between the concrete and the reinforcement.

g) The reinforcement shall be covered to ensure protection from condensation and other deleterious materials.

606.4 Inspection, Sampling and Testing

a) Inspection of reinforcing steel and the installation thereof will be conducted by the Engineer.

b) The Engineer may instruct the Contractor to break out and remove completely all sections of the work already constructed under any of the following circumstances:

i) Reinforcing steel sample under test fails to meet the specification requirements at any time

ii) The Engineer considers that samples which were presented to him for test were not truly representative

iii) It becomes apparent that reinforcing steel which has not been approved has been used on the Works.

c) Representative samples of all reinforcing steel that the Contractor proposes to use in the works must be submitted, before work is commenced, to the Engineer for his written approval.

d) Manufacturer's certificates shall clearly state for each sample: i) The place of manufacture. ii) Expected date and quantity being delivered. iii) All relevant details of composition, manufacture, strengths and other

qualities of the steel. e) The Engineer reserves the right to sample and inspect all reinforcement steel

upon its arrival at the work site. f) Contractor shall provide a certificate confirming that samples taken from the

bars delivered to the site pass the required tests. g) Frequency of sampling and the method of quality control shall be in accordance

with IS: 10790 (Part 2). h) Where epoxy coated steel is used, 0.3 kg samples of the coating, material from

each batch be supplied in an airtight container and identified by the batch number.

i) Allow 14 days for review and approval of samples by the Engineer. j) Tests shall be carried out in accordance with BIS when directed by the

Engineer. k) Tensile tests providing information on following will be required from each

delivery of reinforcement: i) Elastic limit ii) Ultimate strength iii) Stress/strain curve iv) Cross-sectional area v) Deformation/bond characteristics of deformed bars.

l) The Contractor shall carry out tests for dimensions, weight, tensile, bend and/or rebend, at his own cost, for each size of bar to be used in the concrete construction.

m) Manufacturers certificate shall be sufficient for chemical analysis. The Contractor shall arrange for chemical analysis of the steel supplied, at his own cost, if the manufacturers certificate is not available.

n) Test results for each bar size shall be submitted to the Engineer three weeks

before commencement of concrete works.

o) Full testing shall be required if the source of supply of reinforcement changes, in which case the cost of such extra testing will be borne by the Contractor.

p) When any test results do not conform to the relevant standard, the reinforcement steel shall be removed from the site at the Contractors own cost.

606.5 Placing of Reinforcement

a) Rough handling, shock loading (prior to embedment) and the dropping of reinforcement from a height shall be avoided. Reinforcement shall be secured against displacement outside the specified limits.

b) Spacers, chairs and other supports detailed on drawings, together with such other supports as may be necessary, should be used to maintain the specified nominal cover to the steel reinforcement.

c) Spacers or chairs should be placed at a maximum spacing of l.0 m and closer spacing may sometimes be necessary. Spacers, cover blocks should be of concrete of same strength or PVC.

606.6 Welded Joints or Mechanical Connections:

a) Welded joints or mechanical connections (See fig. 600-2) in reinforcement may be used. But in all cases of important connections, tests shall be made to prove that the joints are of the full strength of bars connected.

b) Welding of reinforcements shall be done in accordance with the recommendations of IS: 2751 and IS: 9417.

Figure 600-2-Coupler for reinforcing bars (20 to 28)

606.7 Tolerances:

a) Unless otherwise specified in the drawing, the reinforcement shall be placed within the following tolerances:

i) for effective depth equal to 200 mm or less - +/-10 mm ii) for effective depth more than 200 mm - +/-15 mm

b) Unless specified otherwise, actual concrete cover shall not be deviated from the required nominal cover +10 mm.


Reinforcing steel shall be carried out for the tests as specified in table 600-7.

Table 600-7: Test for reinforcing steel.

Test Code Frequency

Percentage elongation and ultimate tensile strength

IS: 432 & IS: 1786) 3 samples from each supplier

(Same grade)

606.9 References:

IS: 228 Methods for chemical analysis of steels

(Parts 1 to 24)

IS: 280 Mild steel wire for general engineering purposes

IS: 432 Specification for mild steel and medium tensile steel bars and

hard-drawn steel wire for concrete reinforcement

(Part 1) Mild steel and medium tensile steel bars

IS: 1786 Specification for high strength deformed steel bars and wires for concrete reinforcement.

IS: 1566 Specification for hard-drawn steel wire fabric for concrete reinforcement

IS: 13620 Fusion bonded epoxy coated reinforcing bars specification IS: 10790 Methods of sampling of steel for prestressed and reinforced

concrete (Part 2) Reinforcing steel IS: 1387 General requirements for the supply of metallurgical materials IS: 1599 Method for bend test IS: 1608 Metallic materials - Tensile testing at ambient temperature IS: 2062 Hot rolled low, medium and high tensile structural steel

(Sixth revision) IS: 2770 Methods of testing bond in reinforced concrete

(Part 1) Pull-out test. IS: 9417 Recommendations for welding cold-worked steel bars for

reinforced concrete construction. IS: 11587 Structural weather resistant steels.

607 CONCRETE Quality control of concrete works involves correct procedures of proportioning,

batching, mixing, transporting, placing, compacting and curing.

607.1 Requirements

a) For building works, the concrete shall be in grades designated as per table 2 of

IS: 456 and is classified as i) Ordinary concrete ii) Standard concrete and iii)

High strength concrete.

Table 600-8: Grades of concrete (Table 2 of IS 456:2000)

Group Grade

Designation

Characteristic compressive

strength

In 28 days (MPa)

Ordinary

concrete

M10

M15

M20

10

15

20

Standard

concrete

M25

M30

M35

M40

M45

M50

M55

25

30

35

40

45

50

55

High

strength

concrete

M60

M65

M70

M75

M80

60

65

70

75

80

b) For bridge works, the concrete shall be in grades designated as per table 6.4 of

IRC: 112 and is classified as i) Ordinary concrete ii) Standard concrete and iii)

High performance concrete.

Table 600-9: Grades of concrete (Table 6.4 of IRC: 112)

Types of concrete/Grade Designation Characteristic

compressive

strength

In 28 days (MPa)

Ordinary

concrete

Standard

concrete

High

performance

concrete

M15

M20

M15

M20

M25

M30

M35

M40

M45

M50

-

-

-

M30

M35

M40

M45

M50

M60

M65

M70

M75

M80

M85

M90

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

c) The characteristic strength is defined as the strength of material below which

not more than 5 percent of the test results are expected to fall.

d) Ordinary concrete is made on the basis of nominal mix proportioned by weight

of its main ingredients. Proportion by volume may be allowed with the

permission of the Engineer, only where proportion by weight is not practical.

e) Standard concrete is made on the basis of design mix proportioned by weight of

its ingredients and may contain chemical admixtures to achieve certain target

values of various properties in fresh condition.

f) High strength/performance concrete is similar to standard concrete but

contains additional one or more mineral admixtures providing binding

characteristics and partly acting as inert filler material which increase its

strength, reduce its porosity and modify its other properties in fresh as well as

hardened condition.

607.2 Workmanship

607.2.1 Proportioning

a) The proportions of cement, aggregates and water to attain the required

characteristic strengths shall be made by designing the concrete mix (Design

mix concrete) or by adopting nominal concrete mix (Nominal mix concrete).

b) Design mix concrete is preferred to nominal mix. Design mix shall invariably be

used for grade M25 and higher.

c) The proportions of materials for nominal mix concrete shall be in accordance

with table 9 of IS: 456.

Table 600-10: Nominal mix for 50 kg of cement

(Table 9 of IS 456: 2000)

Grade of

concrete

Total quantity of dry

aggregate (CA+FA)

by mass(kg)

Quantity

of water

(litres)

M5

M7.5

M10

M15

M20

800

625

480

330

200

60

45

34

32

30

Note: Proportion of fine aggregate (FA) to coarse aggregate (CA) is generally 1:2, but

varies from 1:1.5 (Zone-I) to 1:2.5 (Zone-III).

Example, 1:1.5 for Maximum Size of Aggregate (MSA) = 10 mm,

1:2.0 (Zone-II) for MSA = 20mm,

1:2.5 (Zone-III) for MSA = 40 mm for an average grading of FA (zone II of

Table 7.4 of IS: 383).

d) The contractor shall carry out the mix design as per IS: 10262 and the mix so

designed shall be approved by the Engineer.

e) Mix design shall be revised, if there is either change of the source or in the

quality of the materials.

f) The materials and their proportion as established by the mix design shall

invariably be followed.

607.2.2 Volume batching

a) Volume batching may be allowed with the permission of Engineer, only where weigh-batching is not practical.

b) In such cases, accurate bulk densities of materials to be used in concrete shall be determined earlier. Allowance for bulking shall be made in accordance with IS: 2386 (Part 3).

c) The mass volume relationship should be checked as frequently as necessary, the frequency for the given job being determined by engineer to ensure that the specified grading is maintained.

d) Volume batching shall be done by measuring boxes having capacity in

multiples of volumes of one bag of cement. e) It is important to maintain the water-cement ratio constant at its correct value.

For this, determination of moisture contents in both fine and coarse aggregates shall be made as frequently as possible, according to weather conditions.

f) The quantity of water to be added shall be adjusted to compensate for any observed variations in the moisture content determined as per IS: 2386 (Part 3).

607.2.3 Plant batching and mixing

a) Ready-mixed concrete (RMC) supplied by ready-mixed concrete plant shall be preferred. For large and medium project sites the concrete shall be sourced

from ready mixed concrete plants or from on site or off site batching and mixing plants.

b) The quantity of both cement and aggregate shall be determined by mass, solid admixture by mass, liquid admixture measured in volume or mass, water shall be weighed or measured by volume in a calibrated tank (see also IS: 4925).

c) The accuracy of the weigh batcher shall be periodically checked and the needle

should be adjusted to zero when the hopper is empty. d) The mix recipe for the mixes to be produced shall be readily available to the

mixer operator. e) Sequencing and blending of the ingredients during charging of the mixers shall

be carried out in such a way as to obtain uniformity and homogeneity in the concrete.

f) During batching, aggregates shall be measured in a manner to maintain their desired grading, and all materials shall be weighed to the tolerances required to

produce the approved design mix. g) The coarse aggregate shall be controlled to minimize segregation and

undersized material. h) Fine aggregate shall be controlled to minimize variations in gradation, giving

special attention to keeping finer fractions uniform and exercising care to avoid excessive removal of fines during processing.

i) Avoid blending two sizes of fine aggregate by placing alternate amounts in bins or stockpiles or when loading in trucks. Satisfactory results are achieved when different size fractions are blended as they flow into a stream from regulating gates or feeders.

j) Stockpiling of coarse aggregate shall be kept to a minimum because fines tend to settle and accumulate. When stockpiling is necessary, use proper methods to minimize the problems with fines, segregation, aggregate breakage, excessive variation in gradation, and contamination.

k) Stockpiles shall be built up in horizontal or gently sloping layers, not by end-

dumping. Trucks, loaders, and dozers, or other equipment shall not be operated on the stockpiles because, in addition to breaking the aggregate, they frequently track dirt onto the piles.

l) Storage facilities for bulk cement shall include separate compartments for each type of cement used. The interior of a cement silo shall be smooth, with a minimum bottom slope of 50 degrees from the horizontal for a circular silo and 55 to 60 degrees for a rectangular silo.

m) Silos shall be equipped with non-clogging air-diffuser flow pads through which small quantities of dry, oil-free, low-pressure air can be introduced intermittently at approximately 20 to 35 kPa to loosen cement that has settled tightly in the silos. Storage silos shall be drawn down frequently, preferably once per month, to prevent cement caking.

n) Each bin compartment from which cement is batched shall include a separate gate, screw conveyor, air slide, rotary feeder, or other conveyance that effectively allows both constant flow and precise cut off to obtain accurate batching of cement.

o) All bins and silos shall be properly tagged at silos, bins and near charging hose. p) Bags of cement should be stacked on pallets or similar platforms to permit

proper circulation of air. For a storage period of less than 60 days, stack the bags no higher than 14 layers, and for longer periods, no higher than seven layers.

q) The quantity of water actually entering the mixing drum should be checked with the reading of the gauge or valve setting, when starting a job.

r) The water batcher and the water pipes should be leak-free. 607.2.4 Process of plant batching and mixing

a) Manual control batching: Manual plants are acceptable for small jobs having low batching rate requirements.

b) Semi-automatic control batching: In this system, aggregate bin gates for charging batchers are opened by manually operated push buttons or switches. Gates are closed automatically when the designated weight of material has been delivered.

c) Automatic control batching: Automatic batching of all materials is electrically activated by a single starter switch. However, interlocks shall interrupt the batching cycle when the scale has not returned to 0.3% of zero balance or when weighing tolerances are exceeded.

d) Batch plant bins shall be of sufficient size to effectively accommodate the production capacity of the plant. Compartments in bins separate the various concrete materials, and the shape and arrangement of aggregate bins shall prevent aggregate segregation and leakage.

e) Weight batchers shall be charged with easy-operating clam shells or undercut radial-type bin gates.

f) Gates used to charge semi-automatic and fully automatic batchers shall be power operated and equipped with a suitable in flight correction to obtain the desired weighing accuracy. They shall be calibrated by the plant supplier for the types of aggregate used at the standard range of moisture contents.

g) Weigh batchers shall be accessible for obtaining representative samples, and they shall be arranged to obtain the proper sequencing and blending of aggregates during charging of the mixer.

h) The amount of concrete mixed in any one batch shall not exceed the rated capacity of the mixer.

i) All mixing and batching plants shall be maintained free of set concrete or cement and shall be clean before commencing mixing.

j) For each different type of cement at use at the plant a separate silo shall be provided.

k) Each batch shall be so charged into the mixer that some of the water will enter in advance of the cement and aggregates. Controls shall be provided to prevent batched ingredients from entering the mixer before the previous batch has been completely discharged.

l) The first batch of concrete through the mixer shall contain an excess of cement to allow for coating of the inside of the mixing drum without reducing the required mortar content of the mix.

m) All water should be in the drum by end of the first 15 seconds of the specified mixing time. Each batch would be mixed until the concrete is uniform in colour at least for a period of two minutes after all the materials and water are in the drum.

n) Mixing plant that has been out of action for more than 30 minutes shall be thoroughly cleaned before any fresh concrete is mixed in it.

o) When a change of mix is made to one using a different type/grade of cement, the mixing plant shall be thoroughly cleaned of all traces of the previously used cement, whatever is the time interval between successive mixes.

607.2.4 Tolerances in batching

a) The accuracy of the measuring equipment shall be within +2% of the quantity of cement being measured and within +3% of the quantity of aggregate, admixtures and water being measured. Standard test weights shall be available to permit the checking of scale accuracy.

b) Testing of the weighers shall be at three month intervals. If water is dispensed by flow meter the frequency of testing shall be at three-month intervals. Such testing shall be undertaken by a calibration agency approved by the department.

c) Test certificates shall be displayed in the plant in prominent positions. d) Cement supplied in bags shall be placed directly from the bag into the intake of

the mixing plant and each batch must contain one or more complete bags of cement. No mixer having a rated capacity of less than a one-bag batch shall be used and the mixer shall not be charged in excess of its rated capacity.

607.2.5 Hand mixing

a) Hand mixing shall be avoided as far as possible. b) Engineer may permit hand mixing for small jobs when mixing by mixer is not

possible due to practical reasons. c) It shall be done on a smooth water tight platform large enough to allow efficient

turning over of the ingredients of concrete before and after adding water. d) Mixing platform shall be so arranged that neither foreign material shall get

mixed with concrete nor the water for mixing shall flow out. e) Cement bags of required number shall be placed in a uniform layer on top of

the measured quantity of fine aggregate, which shall also be spread in a layer of uniform thickness on mixing platform.

f) Dry sand and cement shall then be mixed thoroughly by turning over to get a mixture of uniform colour.

g) Water required for the mix shall then be added gradually and the mass turned over till the mixture obtained is of uniform colour and required consistency.

h) Measured quantity of aggregate shall then be placed on the mixing platform and mixed till the mortar and mixture obtained is of uniform colour and required consistency.

i) In hand mixing, quantity of cement shall be increased by 10% more than the quantity actually required by the mix design or nominal mix.

607.2.6 Transportation

a) The Contractor shall submit for the approval of the Engineer, the details of the equipment and operating techniques for the transportation and placing of concrete.

b) A method statement shall be submitted for approval for major concrete

placements, which shall address: i) The planned rate of placing ii) Number of batching plants iii) Number of trucks iv) Number and positioning of pumps v) Number of labours engaged vi) Pour sequence vii) Quality control measures

viii) Standby equipment ix) Any other factors that might affect the placing of concrete.

c) The method statement should be submitted at least three days in advance of the planned pour. If required by the Engineer a pre-pour planning meeting may be arranged with representatives from the ready-mix supplier, Contractor and Engineer.

d) The Engineer must satisfy himself that the arrangement for transportation of concrete will ensure a nearly continuous flow of concrete during placing.

e) Sufficient lighting arrangements shall be made if concreting is allowed in the night.

f) Concrete shall be conveyed from the mixer to the location of work as rapidly as possible by methods which will prevent segregation or drying out and ensure that the concrete is of the required workability at the point and time of placing.

g) If segregation is noticed in the concrete, the materials shall be remixed to the satisfaction of the Engineer or discarded. The cause of the segregation shall be determined and further occurrences prevented.

h) The Contractor shall ensure that the time between placing of different lifts or layers of concrete is short enough to prevent the formation of cold joints.

i) The Contractor shall ensure that there is a back up plant that can be used in the event of a breakdown, and that adequate provision has been made for the number of delivery trucks.

j) The concrete shall be transported to the site in an approved type of truck mixer or agitator truck The discharge chute and other dirty areas shall be washed down after delivery to prevent spillage on the roads.

k) If a truck mixer or a truck body with an agitator is used for central-mixed concrete, limit the volume of concrete charged into the truck to 80% of the drum or truck volume. If shrink mixing is approved by the Engineer, limit the volume of concrete charged into the truck to 63% of the drum volume.

l) All trucks shall be rotated 30 revolutions at mixing speed before discharging concrete to assure uniformity.

m) The insides of concrete mix trucks shall be inspected periodically, and any build up of concrete removed that may impair the efficiency of the mixing action.

607.2.7 Pumped Concrete

a) Access for the pump shall be checked prior to the pour. If access cannot be assured, the Contractor shall not continue with concreting operations.

b) If approval is obtained for pumped concrete, the Contractor shall ensure that shock is not transferred from the pipeline to the formwork and previously laid concrete.

c) During placing of concrete by pumping, the end hose must never reach into the concrete. All measures shall be taken to avoid blockage of the delivery hose system.

d) Grout shall be pumped through the concrete pump to provide initial lubrication. The initial discharge of any pumped concrete shall not be incorporated in the permanent works.

e) Where concrete is conveyed by chuting or pumping the plant shall be of a size and design to ensure continuous flow in the chute or pipe.

f) The slope of the chute or the pressure of the pump shall allow the concrete to flow without the use of any water additional to that approved by the Engineer to produce the required consistency and without segregation of the ingredients.

g) The delivery end of the chute or pipe shall be thoroughly flushed with water before and after each working period and kept clean. The water used for this purpose shall be discharged outside and away from any permanent works.

607.2.8 Preparation before placing

a) No concrete shall be placed until the Engineer has inspected and approved in writing the surfaces upon which the concrete is to be placed, the formwork, and reinforcing steel.

b) The Contractor shall give the Engineer at least 24 hours notice to enable this inspection to be carried out. If concrete is not placed within 24 hours of approval being given, approval shall be obtained again before concreting. An inspection shall be made immediately prior to concreting to check the cleanliness of the forms.

c) Wood forms, unless lined, shall be oiled or wetted with water in advance of placing concrete so that joints will tighten and prevent seepage of cement grout from the mix.

d) Reinforcement shall be secured in position, inspected, and accepted by the Engineer before placing the concrete. A small quantity of water shall be sprayed on the reinforcement prior to starting the pour.

e) All inserts, anchor bolts, sleeves and other embedded items shall be accurately located, using templates where appropriate, and held securely to prevent displacement during the placing of the concrete. Aluminium items shall be completely covered and protected when embedded in the concrete.

f) Except where shown on the drawings, no fixtures shall be attached to the concrete by shot fixing or drilling without acceptance by the Engineer.

g) Water shall be removed from excavations before concrete is deposited. Any flow of water shall be diverted through proper side drains and shall be removed without washing over freshly deposited concrete.

h) Hardened concrete, debris, and foreign materials shall be removed from interior of forms and from inner surfaces of mixing and conveying equipment.

i) Before depositing new concrete on or against concrete that has set, existing surfaces shall be thoroughly roughened and cleaned of laitance, foreign matter and loose particles.

j) Forms shall be re-tightened and existing surfaces slushed with a grout coat of mortar consisting of cement and fine aggregate in the same proportion in the mix, but not leaner than 1:2, after the existing surface has been moistened.

k) New concrete shall be placed before the grout has attained initial set. l) Horizontal construction joints shall be given a brush coat of grout consisting of

cement and fine aggregate in the same proportion as concrete to be placed, followed by approximately 75mm of concrete of regular mix, except that the proportion of coarse aggregate shall be reduced 50%.

607.2.9 Placing

a) Concrete shall be placed in its final position before initial set has commenced and shall not be subsequently disturbed. All concrete shall be placed within 15 minutes of mixing unless carried in purpose made agitators.

b) Concrete shall be carefully placed in horizontal layers which shall be kept at an even height throughout the work. The depth of layers and time between placement of layers shall be such that each layer can be properly merged into the preceding layer before initial set takes place, the depth of layer shall be determined from the type of plant the Contractor proposes to use.

c) Concrete shall be allowed to slide or flow down sloping surfaces like chute or pipe or shovelled into position.

d) Concrete placed in horizontal slabs from barrows or other tipping vehicles shall be tipped into the face of the previously placed concrete.

e) Concrete dropped into place shall be dropped vertically. It shall not strike the formwork between the point of its discharge and its final place in the work, and

except by approval of the Engineer it shall not be dropped freely through a height greater than 1.5 m.

f) Chutes and conveyor belts shall be so designed that there is no segregation or loss of mortar and shall be provided with a vertical tapered down pipe, or other device, to ensure that concrete is discharged vertically into place.

g) Concrete shall not be placed in standing water in the formwork. h) Concrete that has attained its initial set or has contained its water content for

more than 1.5 hours or 300 drum revolutions, whichever comes first, shall not be deposited in the work.

i) During wet weather, the concrete shall be adequately protected as soon as it is in position.

j) No concreting shall be carried out during periods of continuous heavy rain unless it is completely covered during mixing, transporting and placing.

k) Underwater placing of concrete is allowed only for unreinforced components, the placing being effected exclusively with stationary tremies or with a bottom-opening watertight boxes and shall be in accordance with the requirements of design or equivalent as accepted.

l) Underwater concrete is to be placed continuously without interruption. For water depths up to 1m the concrete may be placed without tremie. In the case of water depths exceeding 1m the concrete is to be placed in such a way that it does not fall freely through the water.

m) The tremies must at all times dip sufficiently far into the freshly placed concrete to ensure that the concrete emerging from the tremie does not come into contact with the water.

n) All works connected with the placing of concrete under water shall be designed, directed and inspected with due regard to local circumstances and purposes.

o) Stops in concrete, at the end of a period of work, shall be made only at construction joint locations shown on the drawings and/or positions accepted.

p) Where the positions of construction joints are not indicated on the drawings, these may be assumed, for estimating purposes, to occur at 5 metre intervals in foundations and retaining walls and at one-third to one-quarter of span in slabs and beams subject to a maximum spacing of approximately 9 metres.

q) At construction joint location, the surface of the completed concrete shall be prepared by wire brushing or chipping so that it is free from all laitance, scum and loose material and shows a slightly roughened texture and tips of the coarse aggregate exposed. Before continuing concreting the exposed concrete face shall be thoroughly wetted and grouted with rich mix.

r) Engineers acceptance shall be obtained by the Contractor, prior to start of work, on the casting sequence and the layout of joints.

s) Waterstops shall be carefully maintained in position prior to concreting on accurately profiled stop boards to create rigid conditions.

t) The type of waterstops to be used shall suit the joint and purpose according to water bar manufacturers recommendations.

607.2.6 Compaction

a) Concrete shall be thoroughly compacted by vibration during the operation of placing and thoroughly worked around the reinforcement, around embedded fixtures and into corners or the formwork to form a solid mass free from voids.

b) When vibrators are used to compact the concrete, vibration shall be applied continuously during the placing of each batch of concrete until the expulsion of air has practically ceased and in a manner that does not promote segregation of the constituents of the concrete.

c) Mechanical vinrators used shall comply with IS:2502, IS:2506, IS:2514 and IS:4656.

d) A sufficient number of vibrators in serviceable condition shall be on site to ensure that spare equipment is always available in the event of breakdown.

e) Immersion type vibrators shall be inserted into the uncompacted concrete vertically and at regular intervals. Where the uncompacted concrete is in a layer above freshly compacted concrete the vibrator shall penetrate vertically for about 100 mm into the previous layer. Vibrators shall not come into contact with the reinforcement or the formwork. They shall be drawn back slowly from the mass concrete so as to leave no voids. Internal type vibrators shall not be placed in the concrete in a random or haphazard manner nor shall concrete be moved from one part of the work to another by means of the vibrators.

f) Operators shall be trained in the use of vibrators. Foremen shall have a minimum of five years of experience in the supervision of placing concrete.

g) Vibration of the concrete shall not be applied by way of the reinforcement. h) Compaction shall commence as soon as there is sufficient concrete to immerse

the vibrator and continue during the placing operations so that at no time shall there be a large volume of uncompacted concrete in the formwork.

i) The duration of vibration shall be limited to that required to produce satisfactory compaction without causing segregation. Vibration shall on no account be continued after water or excess grout has appeared on the surface.

j) During the placing of all reinforced concrete, a competent steel fixer and a competent carpenter shall be in attendance on each concreting gang. They shall ensure the reinforcement embedded fittings and forms are kept in position as work proceeds.

607.2.7 Curing

a) The Contractor shall submit to the Engineer the proposed method of curing for approval.

b) The Contractor shall ensure that curing is provided for 24 hours per day including holidays and that all related necessary plant and labour resources are also available.

c) Special attention shall be given to the curing of vertical and overhanging surfaces to ensure satisfactory curing.

d) Immediately following form removal, the surfaces shall be kept continuously wet by a water spray or water-saturated fabric or until the membrane-forming curing compound is applied.

e) The Contractor shall adopt curing measures that preclude the possibility of thermal shock to the concrete during curing. This may be achieved by ensuring that the temperature of the water used for curing does not differ from that of the concrete by more than 15 C.

f) Curing shall continue for at least 7 days and until it attains an in-place compressive strength of the concrete of at least 70% of the specified compressive or flexural strength, whichever period is longer. Curing shall not stop unless otherwise approved by the Engineer.

g) When low W/C is used, the concrete shall be preferably cured by water. h) Freshly placed concrete shall be protected from sun, wind, exposure and

excessive drying out. i) All fresh concrete shall be cured by liquid membrane curing compound or

equivalent as soon as possible, provided that the surface water has evaporated. The liquid membrane curing shall not be applied if bleed water is forming or is present on the concrete surface.

j) If the concrete is cured by liquid membrane, the applied film should be protected from rain for at least 3 hours and care should be taken to ensure that the film is not broken.

k) All concrete shall be cured for a period of time required to obtain the full specified strength, but not less than seven consecutive days. The method of curing shall be by water for the first seven days and by water or membrane until the concrete has reached the full specified strength.

l) For mixtures with a low to zero bleeding rate, or in the case of aggressively evaporative environments, or both, the curing shall start at early anytime between placement and final finishing of the concrete. The curing shall be by reducing the moisture loss from surface using fogging systems and the use of evaporation reducers such as monomolecular water curing compound.

m) Exposed surfaces shall be protected from air blown contamination until 28 d after the concrete is placed.

n) The method of curing shall ensure that sufficient moisture is present to complete the hydration of the cement, and shall be to the approval of the Engineer. The method of curing shall not:

i. Disfigure permanently exposed surfaces ii. Affect bonding of subsequent coatings iii. Increase the temperature of the concrete. iv. During the curing period, exposed concrete surface shall be protected

from the direct rays of the sun. Curing of Formed Surfaces:

a) Formed surfaces, including the underside of beams, girders, supported slabs and the like, by moist curing with the forms in place for the full curing period, or until the forms are removed.

b) In case of formed concrete if liquid membrane curing is used, it should be applied immediately after de-shuttering (removal of the form). In such a case the concrete surface must be dampened with clean water prior the application.

Moisture Curing:

a) Moisture curing shall be performed by : i) Covering the surface of the concrete with water

and keeping it continuously wet. ii) Continuous use of fine fog water sprays iii) Covering the surface with a saturated absorptive cover and keeping it

continuously wet. iv) Jute mats, cotton mats, and other absorbent materials can be used to

hold water on horizontal or vertical surfaces.

v) Wet straw or hay can be used for wet-curing small areas, but there is the danger that wind might displace it unless it is held down with screen wire, burlap, or other means

b) Where method (i) is employed, the bunds used shall not be made from fill from excavations or any other areas where there is the possibility of chloride contamination.

Moisture Retaining Cover Curing:

a) The concrete surface shall be covered with a suitable absorptive covering. b) The absorptive covering shall be overlaid with a 1000 gauge polythene sheet. c) The cover shall be in the widest practical widths and shall have 200 mm side

and end laps. d) The laps shall be sealed with adhesive tape. e) Any penetrations or tear in the covering shall be shall be repaired with the

same material and waterproof tape. Liquid Membrane Curing:

a) Membrane forming curing compounds shall be applied in accordance with the manufacturer's recommendations immediately after any water sheen which may develop after finishing has disappeared from the surface and within 2 h of stripping formwork on formed surfaces.

b) Membrane forming curing compounds shall not be used on surfaces against which additional concrete or other material is to be bonded unless:

i. It is proven that the curing compound will not prevent bond, or ii. Positive measures are taken to remove it completely from those areas

which are to receive bonded applications on fair faced concrete surfaces.

Steam Curing

a) An enclosure shall be formed around the concrete using tarpaulin or other suitable meas.

b) Application of steam shall not be commenced until at least 2 h after final placement of concrete.

c) Steam shall be applied at a temperature between 65C and 80C.

d) Excessive rates of heating and cooling shall be prevented during steam curing and temperatures in the enclosure shall not be allowed to increase or decrease by more than 22C per hour.

e) The maximum steam temperature shall be maintained in the enclosure until concrete has reached its specified strength.

607.2.8 Mass concrete

a) Mass concrete is often cured with water for the additional cooling benefit in warm weather; however, this can be counterproductive when the temperature gradient between the warmer interior and the cooler surface generates stress in the concrete.

b) Horizontal or sloping unformed surfaces of mass concrete can be maintained

continuously wet by water spraying, wet sand, or water saturated fabrics. c) For vertical and other formed surfaces, after the concrete has hardened and the

forms are still in place, the form ties may be loosened and water supplied to run down the inside of the form to keep the concrete wet

d) Care shall be taken to prevent thermal shock and cracks when using water that is significantly cooler than the concrete surface. Curing water should not be

more than about 11C cooler than the concrete.

e) Curing shall start as soon as the concrete has hardened sufficiently to prevent surface damage.

f) For unreinforced massive sections not containing ground granulated blast-furnace slag or pozzolan, curing shall be continued for not less than 2 weeks. Where ground granulated blast-furnace slag or pozzolan is included in the concrete, the minimum time for curing shall be not less than 3 weeks.

g) For reinforced mass concrete, curing shall be continuous for a minimum of 7 days or until 70% of the specified compressive strength is obtained, if strength is the key concrete performance criterion. For construction joints, curing shall be continued until resumption of concrete placement or until the required curing period is completed.

h) Curing shall not stop until favourable differential temperature is attained and at the approval of the Engineer.

607.3 SAMPLING AND TESTING

a) Unless the Engineer directs otherwise, the Contractor shall include at least the tests on fresh concrete as specified in table 600-11.

Table 600-11: Tests for concrete

Sl.

No. Test Code

Min. Quantity of

material/work for

carrying out test

Minimum

Frequency of

sampling

1 Slump test - 1 in a day

2 Cube test 20 m3 in slab,

beam and

connected column

Every 20 m3

of a days

concrete

5 m3 in columns Every 5 m3

3 Hammer

test

IS: 13311

(Part 2)

Once in every three months or as

directed by the Engineer

Note: For all other small items and where RCC done in a day is less than 5 m3, test may be carried out as required by Engineer.

b) Samples from fresh concrete shall be taken as per IS: 1199 and cubes shall be made, cured and tested at 28 days in accordance with IS: 516.

c) In order to get a relatively quicker idea of the quality of concrete, optional tests on beams for modulus of rupture at 72+2 h or at 7 days, or compressive strength tests at 7 days may be carried out in addition to 28 days compressive strength test.

d) For this purpose the values should be arrived at based on actual testing. In all cases, the 28 days compressive strength as specified shall alone be the criterion for acceptance or rejection of the concrete.

e) A random sampling procedure shall be adopted to ensure that each concrete

batch shall have a reasonable chance of being tested, that is, the sampling should be spread over the entire period of concreting and cover all mixing units.

f) The minimum frequency of sampling of concrete of each grade shall be in accordance with table 600-11.

g) Three test specimens shall be made for each sample for testing at 28 days. Additional samples may be required for various purposes such as to determine the strength of concrete at 7 days or at the time of striking the formwork, or to determine the duration of curing, or to check the testing error. Additional

samples may also be required for testing samples cured by accelerated methods as described in IS: 9103.

h) The specimen shall be tested as described in IS: 516. i) The test results of the sample shall be the average of the strength of three

specimens. The individual variation should not be more than 15 percent of the average. If more, the test results of the sample are invalid.

j) The concrete shall be deemed to comply with the strength requirements when both the following condition are met: i) The mean strength determined from any group of four consecutive test

results compiles with the appropriate limits in table 600-12. ii) Any individual test result complies with the appropriate limits in table 600-

12. k) Concrete of each grade shall be assessed separately. l) To ensure that the construction complies with the design an inspection

procedure should be set up covering materials, records, workmanship and construction.

m) 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 measures to the satisfaction of the Engineer.

Table 600.7: Characteristic compressive strength compliance requirements

Specified grade

Mean of the Group of 4 Non-overlapping consecutive test results (MPa)

Individual test results (MPa)

M15 fck +0.825 x established standard deviation (rounded off to nearest 0.5 MPa) or fck +3 MPa, whichever is greater.

fck-3MPa

M20 or above

fck +0.825 x established standard deviation (rounded off to nearest 0.5 MPa)

or fck +4 MPa, whichever is greater.

fck-4MPa

Note: In the absence of established value of standard deviation, given in table 8 of IS: 456-2000 may be assumed and attempt should be made to obtain result of 30 samples as early as possible to establish the value of standard deviation.

607.4. REFERENCES

IS: 226 Structural steel IS: 442 Specification for mild and medium tensile steel bars and hard drawn steel wire for concrete reinforcement (Part-1) Mild steel and medium tensile steel bars (Part-2) Hard drawn steel wire IS: 456 Code of practise for plain and reinforced concrete IS: 516 Method of test for strength of concrete IS: 716 Specification for Pentachlorophenol IS: 1199 Method of sampling and analysis of concrete IS: 1566 Specification for hard-drawn steel wire fabric for concrete

IS: 1599 Method for bend test IS: 1608 Method for tensile testing of steel products IS: 1786 Specification for high strength deformed steel and wires for concrete reinforcement IS: 1791 Specification for batch type concrete mixes IS: 2502 Code of practice for bending and fixing bars for concrete

reinforcement IS: 2751 Recommended practice for welding of mild steel, plain and deformed bars for reinforced construction IS: 4925 Specification for concrete batching and mixing plant IS: 6523 Specification for precast reinforced concrete door and window frames IS: 10262 Recommended guidelines for concrete mix design IS: 13311 Non-destructive testing of concrete (Part-1) Method of test for ultrasonic pulse velocity (Part-2) Method of testing by rebound hammer

608 FORMWORK

This part includes formwork and false-work for structural cast-in-place concrete.

608.1 Requirements/Workmanship a) The Contractor shall submit samples of all proposed formwork materials and

samples of ties proposed for use in general situations above the water table and for fair faced concrete.

b) Formwork and associated false-work for buildings shall be designed to comply with the requirements of IS: 14687.

c) Forms shall be of wood, metal or other material acceptable to the Engineer. d) The design of formwork shall be the responsibility of the Contractor. e) Form oil and form sealer shall be of approved quality. f) The erection of formwork and associated false-work shall be executed and

supervised by fully skilled and qualified personnel having a minimum of three years experience.

g) The Contractor shall obtain approval to load any particular section of the works from the Engineer.

h) The erected formwork shall be watertight from the ingress of external liquids and the egress of internal liquids. Adjustable steel supports and shores shall allow form-boards and framework to be accurately adjusted to line and level.

i) The Contractor shall ensure that adequate ground support for false-work is available, and if not, shall take measures to make them suitable.

j) Formwork shall be designed to be sufficiently rigid to maintain the correct position, shape and profile so that the final concrete structure is within the dimensional tolerances specified below.

k) Formwork shall be designed to be demountable without causing shock, disturbance or damage to the concrete.

l) Care shall be taken to ensure that the finish to the exposed concrete on the external and internal surfaces are of the highest quality to produce a smooth concrete surface of uniform texture and appearance without visible imprint of grains, steppings or ridges.

m) The resulting concreting shall be free from honeycombing, stains, fins, lipping, nail and screw marks, raised grain marks or any other imperfections and shall

be of a uniform surface texture and colour. Only very minor surface blemishes caused by entrapped air or water will be accepted provided that they do not exceed 0.5% by area of each square metre considered separately and in addition they shall not be concentrated in a manner such that they are noticeable.

n) All exposed concrete corners and edges shall have 20 mm by 20 mm chamfers. Fillet and chamfer strips shall be PVC or timber to the approval of the Engineer.

o) Formwork in contact with the concrete shall be treated with a suitable release agent to prevent adherence of the concrete.

p) Forms for exposed surfaces shall be coated with oil before reinforcement is placed. Forms for unexposed surfaces may be thoroughly wetted with water in lieu of oiling, immediately before placing of concrete.

q) Excessive oiling of the forms shall not be permitted in order to prevent discoloration of the cement plaster. Where concrete surface is to be painted, the form-oil must not affect the bond between concrete and paint.

r) Care shall be taken to prevent the oil from coming in contact with reinforcement or with concrete at construction joints. Any oil on reinforcing steel shall be removed.

s) Tapes to be used to seal joints of formwork panels for smooth finish concrete shall be plastic faced adhesive tape approved by the Engineer.

t) Where formwork to external faces will be permanently exposed, all horizontal and vertical formwork joints shall be so arranged that joint lines will form a uniform pattern on the face of the concrete.

u) Where the Contractor proposes to make up the formwork from standard sized manufactured formwork panels, the size of such panels shall be approved by the Engineer before they are used in the construction of the Works.

v) The finished appearance of the entire elevation of the structure and adjoining structures shall be considered when planning the pattern of joint lines caused by the formwork and by the construction joints to ensure continuity of horizontal and vertical lines.

w) Faces of formwork in contact with concrete shall be free from adhering foreign matter, projecting nails and the like, splits or other defects, and all formwork shall be clean and free from standing water, dirt, shavings, chippings or other deleterious matter.

x) The Contractor shall verify lines, levels and measurement before proceeding with formwork erection.

y) Formwork shall be provided for the top surfaces of sloping work where the slope exceeds 15 from the horizontal (except where any such top surface is specified as a spaded finish).

z) The formwork shall be anchored to enable the concrete to be properly compacted and to prevent flotation.

608.1.1 Conduits a) Conduits or pipes shall be located so as not to reduce the strength of the

construction. b) In no case shall pipes other than conduits be placed in a slab 125 mm or less in

thickness. c) Conduits embedded in a concrete slab shall not have an outside diameter

greater than one-third the thickness of the slab nor be placed below the bottom reinforcing steel or over the top reinforcing steel.

d) Pipes and conduits where embedded shall be placed as nearly as possible to the centre line of the concrete section.

608.1.2 Stripping of Formwork a) Forms shall not be released until the concrete has achieved strength of at least

twice the stress to which the concrete may be subjected at the time of removal of formwork.

b) The period of time elapsing between the placing of the concrete and the striking of the formwork shall be approved by the Engineer after consideration of the loads likely to be imposed on the concrete and shall in any case be not less than the periods as shown in Table 600-12 (Cl. 11.3.1 of IS 456).

Table 600-12: Stripping time of formwork (When OPC is used)

No. Type of formwork

Minimum period

before striking

formwork

1. Vertical formwork to columns, walls, beams

16-24 h

2. Soffit formwork to slabs (Props to be refixed immediately after removal of formwork)

3 days

3. Soffit formwork to beams (Props to be refixed immediately after removal of formwork)

7 days

4. Props to slabs: i) Spanning up to 4.5 m ii) Spanning over 4.5 m

7 days

14 days

5. Props to beams and arches: i) Spanning up to 6 m ii) Spanning over 6 m

14 days

21 days

Note: For other cements and lower temperature, the stripping time recommended above may be suitably modified.

c) The number of props left under, their sizes and disposition shall be such as to be able to safely carry the full dead load of the slab, beam or arch as the case may be together with any live load likely to occur during curing or further construction.

d) Where the shape of the element is such that the formwork has re-entrant

angles, the formwork shall be removed as soon as possible after the concrete has set to avoid shrinkage cracking occurring due to the restraint imposed.

e) Stripping of the formwork within the time limits listed above does not relieve the Contractor from successfully crushing test cubes and achieving the compressive strength as specified.

f) Notwithstanding the foregoing, the Contractor shall be held responsible for any damage arising from removal of formwork before the structure is capable of carrying its own weight and any incidental loading.

608.2 Tolerances

a) Deviations of specified dimensions of cross sections of beams and columns shall be +12 or -6 mm.

b) Deviations of specified plan dimensions of footings shall be +50 or -12 mm. c) Deviations of specified thickness of footings shall be +/- 0.05 times specified

thickness.

608.3 References

IS: 14687 False-work for Concrete Structures Guidelines.

SECTION 1100: ROOFING AND CEILING

1100. ROOFING

Roof is the upper most part of a building provided to protect the building

from rain, wind, sun, snow etc. Functional requirements of a roof are as

under.

i. It should have adequate strength and stability to carry the

superimposed dead and live loads without excessive deflection. The

roof should be stable against movement due to temperature and

moisture changes.

ii. It should effectively protect the building against rain, sun, wind, snow

etc. It should have efficient drainage and be capable of taking good

waterproofing treatment.

iii. The roof and roof covering should be fire resistant.

1100.1 TERMINOLOGY

a) Accessories - Purpose made fittings, such as apron flashing pieces, barge boards, bottom glazing flashing, corner piece (corner flashing), eaves filler

pieces, expansion joints, hip capping, hip tile or cap, ridge capping, ridge

finials, roof lights, ventilators, with which the roof is furnished.

b) Eaves - The lower edge of the inclined roof.

c) Finial - A decorative fitting used at the Junction of ridges and hips to form a water proof covering and at the top of conical, pyramidal, or dome roofs.

d) Flashing - A strip of impervious material, usually metal used to exclude water from the junction between a roof covering and another part of the

structure. e) Gable - Part of wall above the general eaves level at tie end of ridged or partially hipped roof.

f) Gutter - Any form of roof water channel.

g) Hip - The outer angle (more than 180 degree) formed by the inclined ridge

between two intersecting roof slopes.

h) Pitch - The angle of inclination with the horizontal of the rafters or substructure surface on which the roof coverings are laid.

In patent glazing, the angle at which the plane of a stretch of glazing is

inclined to the horizontal.

i) Pitched Roof - A roof, the pitch of which is greater than 10 degree to the horizontal.

j) Ridge - The horizontal inter-section at the apex of the two rising roof

surfaces inclined in opposite directions.

k) Valley- The re-entrant angle formed by the inter-section of two inclined roof surfaces.

l) Verge- Free edge of a roof surface ending at a gable.

1100.2 GALVANISED STEEL SHEET ROOFING

1100.2.1 Materials

a) Galvanised plain steel sheets are supplied in any combination of the

following lengths, widths and thickness.

i. Length : 2500 and 3000 mm

ii. Width : 900 and 1000 mm

iii. Thickness : 0.50, 0.63, 0.80, 1.00 mm

b) In case of sheets supplied in coil, the internal diameter of coil shall be

450, 510 and 610 mm and the mass of each coil shall not exceed 12

tonne.

c) Corrugated galvanised sheets shall have a length of 2500 or 3000 mm

d) The thickness shall be as specified in the description of the item

e) The roofing sheets shall conform to IS: 277.

f) The sheets shall be of 275 grade of coating unless otherwise specified

in the description of item.

g) The sheets shall be free from cracks, split edges, twists, surface flaws

etc.

h) They shall be clean, bright and smooth.

i) The galvanising shall be non-injurious and in perfect condition.

j) The sheets shall not show signs of rust or white powdry deposits on

the surface.

k) The corrugations shall be uniform in depth and pitch and parallel

with the side.

l) Purlins shall be of the specified material or M.S. rolled sections of

requisite size.

m) The bolts for fixing the roof shall be sufficiently long so that after

fixing they project above the top of the nuts by not less than 10 mm.

n) The grip of J or L hook bolt on the side of the purlin shall not be less

than 25 mm.

o) The galvanised coating on J or L hooks, and bolts shall be continuous

and free from defects such as blisters, flux stains, drops, excessive

projections or other imperfections which would impair serviceability.

1100.2.2 Requirements

a) Roof shall not be pitched at a flatter slope than 1 vertical to 5

horizontal.

b) The normal pitch adopted shall usually be 1 vertical to 3 horizontal

c) The purlins shall not be spaced at more than the following distances.

Table 1100-1: Maximum spacing of purlins

Thickness of C.G.S.

sheet(mm)

Maximum spacing

of purlins(m)

1.00

2.00

0.80

1.8

0.63

1.6

d) The top surfaces of the purlins shall be uniform and plane. They shall

be painted before fixing on top.

e) Embedded portions of wooden purlins shall be provided with anti

termite treatment.

f) The galvanised coating on J and L hooks should conform to IS: 1367 -

Part XIII. The mass of coating per square meter of the surface shall be

as in table below

Table 1100-2: Mass and equivalent thickness of coating

Minimum Mass

(g/m2)

Average Thickness

(m)

Individual

Thickness (m)

375

54

_

300 _

43

1100.2.3 Laying and Fixing

a) The sheets shall be laid on the purlins to a true plane, with the lines

of corrugations parallel or normal to the sides of the area to be

covered unless otherwise required as in spe

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