IS 456 : 2000                           Indian Standard            PLAIN AND REINFORCED CONCRETE -                    CODE...
IS456: 2000                                          Indian Standard             PLAINAND REINFORCEDCONCRETE-             ...
IS 456 : 2000  m) The clause on ‘Construction Joints’ has been modified.  n) The clause on ‘Inspection’ has been modified ...
IS 456 : 2000      DIN 1045 July 1988 Structural use of concrete, design and construction, Deutsches Institut fur Normung ...
As in the Original Standard, this Page is Intentionally Left Blank
IS456:2000                                                          CONTENTS                                              ...
IS 456 : 2000                                                                     PAGE    13.4 Construction Joints and Col...
IS456:2000                                                                                       PAGE      22.4     Struct...
IS 456 : 2000                                                                                        PAGE       30.5    Si...
PAGE38 LIMITSTATE COLLAPSE :FLEXURE            OF                                                               69     38....
IS 456 : 2ooo    B-4     MYERS SUBJECTED                         TOCOMBINED                                 Axw. LOAD BEND...
IS456:2000                                             SECTION 1      GENERAL1 SCOPE                                      ...
IS 456 : 2000      Yc,   -   Calculated maximum bearing pressure            xl     -   Partial safety factor for material ...
IS456:2000                              SECTION 2 MATERIALS, WORKMANSHIP,                                    INSPECTION AN...
IS 456 : 2000Portland cements provided uniform blending with                  free from injurious amounts of oils, acids, ...
lS456:2000                                     ‘lhble 1 Permissible Limit for !Wids                                       ...
IS 456 : 2000             Table 2 Grades cif Concrete           (Clau.re6.1,9.2.2,   15.1.1 and36.1)                      ...
IS 456 : 20007 WORKABILITY OF CONCRETE7.1 The concrete mix proportions chosen should be                   be compacted wit...
IS 456 : 20008.2 Requirements          for Durability                                8.2.2.2 Abrasive8.2.1 Shape and Size ...
IS 456 : 20008.2.4.2 Maximum cement content                                                     been given in design to th...
IS 456 : 20008.2.5 Mix Constituents                                                    expansion and disruption of concret...
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Is code 456 2000

  1. 1. IS 456 : 2000 Indian Standard PLAIN AND REINFORCED CONCRETE - CODE OF PRACTICE ( Fourth Revision ) ICS 91.100.30 0 BIS 2000 BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002July 2000 Price Rs 260.00
  2. 2. IS456: 2000 Indian Standard PLAINAND REINFORCEDCONCRETE- CODEOFPRACTICE ( Fourth Revision )FOREWORDThis Indian Standard (Fourth Revision) was adopted by the Bureau of Indian Standards, after the draft finalixedby the Cement and Concrete Sectional Committee had been approved by the Civil Engineering Division Council.This standard was first published in 1953 under the title ‘Code of practice for plain and reinforced concrete forgeneral building construction’ and subsequently revised in 1957. The code was further revised in 1964 andpublished under modified title ‘Code of practice for plain and reinforced concrete’, thus enlarging the scope ofuse of this code to structures other than general building construction also. The third revision was published in1978, and it included limit state approach to design. This is the fourth revision of the standard. This revisionwas taken up with a view to keeping abreast with the rapid development in the field of concrete technology andto bring in further modifications/improvements in the light of experience gained while using the earlier versionof the standard.This revision incorporates a number of important changes. The major thrust in the revision is on the followinglines: a) In recent years, durability of concrete structures have become the cause of concern to all concrete technologists. This has led to the need to codify the durability requirements world over. In this revision of the code, in order to introduce in-built protection from factors affecting a structure, earlier clause on durability has been elaborated and a detailed clause covering different aspects of design of durable structure has been incorporated. b) Sampling and acceptance criteria for concrete have been revised. With tbis revision acceptance criteria has been simplified in line with the provisions given in BS 5328 (Part 4):1990 ‘Concrete: Part 4 Specification for the procedures to be used in sampling, testing and assessing compliance of concrete’.Some of the significant changes incorporated in Section 2 are as follows: a) All the three grades of ordinary Portland cement, namely 33 grade, 43 grade and 53 grade and sulphate resisting Portland cement have been included in the list of types of cement used (in addition to other types of cement). b) The permissible limits for solids in water have been modified keeping in view the durability requirements. cl The clause on admixtures has been modified in view of the availability of new types of admixtures including superplasticixers. d) In Table 2 ‘Grades of Concrete’, grades higher than M 40 have been included. e) It has been recommended that minimum grade of concrete shall be not less than M 20 in reinforced concrete work (see also 6.1.3). 0 The formula for estimation of modulus of elasticity of concrete has been revised. 8) In the absenceof proper correlation between compacting factor, vee-bee time and slump, workability has now been specified only in terms of slump in line with the provisions in BS 5328 (Parts 1 to 4). h) Durability clause has been enlarged to include detailed guidance concerning the factors affecting durability. The table on ‘Environmental Exposure Conditions’ has been modified to include ‘very severe’ and ‘extreme’ exposure conditions. This clause also covers requirements for shape and size of member, depth of concrete cover, concrete quality, requirement against exposure to aggressive chemical and sulphate attack, minimum cement requirement and maximum water cement ratio, limits of chloride content, alkali silica reaction, and importance of compaction, finishing and curing. j) A clause on ‘Quality Assurance Measures’ has been incorporated to give due emphasis to good practices of concreting. k) Proper limits have been introduced on the accuracy of measuring equipments to ensure accurate batching of concrete. 1
  3. 3. IS 456 : 2000 m) The clause on ‘Construction Joints’ has been modified. n) The clause on ‘Inspection’ has been modified to give more emphasis on quality assurance.The significant changes incorporated in Section 3 are as follows: a) Requirements for ‘Fire Resistance’ have been further detailed. b) The figure for estimation of modification factor for tension reinforcement used in calculation of basic values of span to effective depth to control the deflection of flexural member has been modified. cl Recommendations regarding effective length of cantilever have been added. 4 Recommendations regarding deflection due to lateral loads have been added. e) Recommendations for adjustments of support moments in restrained slabs have been included. 0 In the detemination of effective length of compression members, stability index has been introduced to determine sway or no sway conditions. g) Recommendations have been made for lap length of hooks for bars in direct tension and flexural tension. h) Recommendations regarding strength of welds have been modified. j) Recommendations regarding cover to reinforcement have been modified. Cover has been specified based~on durability requirements for different exposure conditions. The term ‘nominal cover’ has been introduced. The cover has now been specified based on durability requirement as well as for fite requirements.The significant change incorporated in Section 4 is the modification-of the clause on Walls. The modified clauseincludes design of walls against horizontal shear.In Section 5 on limit state method a new clause has been added for calculation of enhanced shear strength ofsections close to supports. Some modifications have also been made in the clause on Torsion. Formula forcalculation of crack width has been-added (separately given in Annex P).Working stress method has now been given in Annex B so as to give greater emphasis to limit state design. Inthis Annex, modifications regarding torsion and enhanced shear strength on the same lines as in Section 5 havebeen made.Whilst the common methods of design and construction have been covered in this code, special systems ofdesign and construction of any plain or reinforced concrete structure not covered by this code may be permittedon production of satisfactory evidence regarding their adequacy and safety by analysis or test or both(see 19).In this code it has been assumed that the design of plain and reinforced cement concrete work is entrusted to aqualified engineer and that the execution of cement concrete work is carried out under the direction of a qualifiedand experienced supervisor.In the formulation of this standard, assistance has been derived from the following publications: BS 5328-z Part 1 : 1991 Concrete : Part 1 Guide to specifying concrete, British Standards Institution BS 5328 : Part 2 : 1991 Concrete : Part 2 Methods for specifying concrete mixes, British Standards Institution BS 5328 : Part 3 : 1990 Concrete : Part 3 Specification for the procedures to be used in producing and transporting concrete, British Standards Institution BS 5328 : Part 4 : 1990 Concrete : Part 4 Specification for the procedures to be used in sampling, testing and assessing compliance of concrete, British Standards Institution BS 8110 : Part 1 : 1985 Structural use of concrete : Part 1 Code of practice for design and construction, British Standards Institution BS 8110 : Part 2 : 1985 Structural use of concrete : Part 2 Code of practice for special circumstances, British Standards Institution AC1 3 19 : 1989 Building code requirements for reinforced concrete, American Concrete Institute AS 3600 : 1988 Concrete structures, Standards Association of Australia 2
  4. 4. IS 456 : 2000 DIN 1045 July 1988 Structural use of concrete, design and construction, Deutsches Institut fur Normung E.V. CEB-FIP Model code 1990, Comite Euro - International Du BelonThe composition of the technical committee responsible for the formulation of this standard is given inAnnex H.For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,observed or calculated, expressing the result of a test or analysis shall be rounded off in accordance withIS 2 : 1960 ‘Rules for rounding off numerical values (revised)‘. The number of significant places retained in therounded off value should be the same as that of~the specified value in this standard.
  5. 5. As in the Original Standard, this Page is Intentionally Left Blank
  6. 6. IS456:2000 CONTENTS PAGE SECTION 1 GENERAL 111 SCOPE 112 REFERENCES 113 TERMINOLOGY 114 SYMBOLS SECTION 2 -MATERIALS, WORKMANSHIP, INSPECTION AND TESTING 135 MATERIALS 13 5.1 Cement -13 5.2 Mineral Admixtures 14 5.3 Aggregates 14 5.4 Water 15 55 Admixtures 15 5.6 Reinforcement 15 5.7 Storage of Materials 156 CONCRETE 15 6.1 Grades 15 6.2 Properties of Concrete 17 7 WORKABILITY CONCRETE OF 17 8 DURABILITY CONCRETE OF 17 8.1 General 18 8.2 Requirements for Durability 22 9 CONCRETE Mrx PROPORTIONING 22 9.1 Mix Proportion 22 9.2 Design Mix Concrete 23 9.3 Nominal Mix Concrete 23 10 PRODUCTION CONCRETE OF 23 10.1 Quality Assurance Measures 24 10.2 Batching 24 10.3 Mixing 25 11 FORMWORK 25 11.1 General 25 11.2 Cleaning and Treatment of Formwork 25 1I .3 Stripping Time 25 12 ASSEMBLY REINFORCEMENT OF 26 13 TRANSPORTING, PLACING, COMPACTION CURING AND 26 13.1 Transporting and Handling 26 13.2 Placing 26 13.3 Compaction
  7. 7. IS 456 : 2000 PAGE 13.4 Construction Joints and Cold Joints 27 13.5 Curing 27 13.6 Supervision 2714 CONCRERNG UNDER SPECIAL CONDITIONS 27 14.1 Work in Extreme Weather Conditions 27 14.2 Under-Water Concreting 27 15 SAMPLING STRENGTH DESIGNED AND OF CONCRETE Mrx 29 15.1 General 29 15.2 Frequency of Sampling 29 15.3 Test Specimen 29 15.4 Test Results of Sample 29 16 ACCEPTANCE CRITERIA 29 17 INSPECI-ION TEFXJNG STRWTURE AND OF 30 SECTION 3 GENERAL DESIGN CONSIDERATION 18 BASESFORDEIGN 32 18.1 Aim of Design 32 18.2 Methods of Design 32 18.3 Durability, Workmanship and Materials 32 18.4 Design Process 32 I 9 LOADS FORCES AND 32 19.1’ General 32 19.2 Dead Loads 32 19.3 Imposed Loads, Wind Loads and Snow Loads 32 19;4 Earthquake Forces 32 19.5 Shrinkage, Creep and Temperature Effects 32 19.6 Other Forces and Effects 33 19.7 Combination of Loads 33 19.8 Dead Load Counteracting Other Loads and Forces 33 19.9 Design Load 33 20 STABILITY THESTRUCTURE OF 33 20.1 Overturning 33 20.2 Sliding 33 20.3 Probable Variation in Dead Load 33 20.4 Moment Connection 33 20.5 Lateral Sway 33 2 1 FIRERESISTANCE 33 22 ANALYSIS 34 22.1 General 34 - 22.2 Effective Span 34 22.3 Stiffness 35 6
  8. 8. IS456:2000 PAGE 22.4 Structural Frames 35 22.5 Moment and Shear Coefficients for Continuous Beams 35 22.6 Critical Sections for Moment and Shear 36 22.7 Redistribution of Moments 36 .23 BEAMS 36 23.0 Effective Depth 36 23.1 T-Beams and L-Beams 36 23.2 Control of Deflection 37 23.3 Slenderness Limits for Beams to Ensure Lateral Stability 3924 SOLIDSLABS 39 24.1 General 39 24.2 Slabs Continuous Over Supports 39 24.3 Slabs Monolithic with Supports 39 24.4 Slabs Spanning in Two Directions~at Right Angles 41 24.5 Loads on Supporting Beams 4125 COMPRESSION MEZMBERS 41 25.1 Definitions 41 25.2 Effective Length of Compression Members 42 25.3 Slenderness Limits for Columns 42 25.4 Minimum Eccentricity 4226 REQUIREMENTS GOVERNING AND REINFORCEMENT DETAILING 42 26.1 General 42 26.2 Development of Stress in Reinforcement 42 26.3 Spacing of Reinforcement 45 26.4 Nominal Cover to Reinforcement 46 26.5 Requirements of Reinforcement for Structural Members 46 27 EXPANSION JOMTS 50 SECTION 4 SPECIAL DESIGN REQUIREMENTS FOR STRUCTURAL MEMBERS AND SYSTEMS 28 CONCRETE CORBELS 51 28.1 General 51 28.2 Design 51 29 DEEP BEAMS 51 29.1 General 51 29.2 Lever Arm 51 29.3 Reinforcement 51 30 RIBBED, HOLLOWBLOCKORVOIDEDSLAB 52 30.1 General 52 30.2 Analysis of Structure 52 30.3 Shear 52 30.4 Deflection 52
  9. 9. IS 456 : 2000 PAGE 30.5 Size and Position of Ribs 52 30.6 Hollow Blocks and Formers 52 30.7 Arrangement of Reinforcement 53 30.8 Precast Joists and Hollow Filler Blocks 5331 FLAT SLABS 53 3 1.1 General 53 3 1.2 Proportioning 53 3 1.3 Determination of Bending Moment 53 3 1.4 Direct Design Method 54 3 1.5 Equivalent Frame Method 56 3 1.6 Shear in Flat Slab 57 3 1.7 Slab Reinforcement 59 3 1.8 Openings in Flat Slabs 6132 WALLS 61 32.1 General 61 32.2 Empirical Design Method for Walls Subjected to Inplane Vertical Loads 61 32.3 Walls Subjected to Combined Horizontal and Vertical Forces 62 32.4 Design for Horizontal Shear 62 32.5 Minimum Requirements for Reinforcement in Walls 62 33 STAIRS 63 33.1 Effective Span of Stairs 63 33.2 Distribution of Loading on Stairs 63 33.3 Depth of Section 63 34 Foort~~s 63 34.1 General 63 34.2 Moments and Forces 64 34.3 Tensile Reinforcement 65 34.4 Transfer of Load at the Base of Column 65 34.5 Nominal Reinforcement 66 SECTION 5 STRUCTURAL DESIGN (LIMIT STATE METHOD) 35 SAFETY AND SERVKEABlLITY kKNIREMl?N’l’s 67 35.1 General 67 35.2 Limit State of Collapse 67 35.3 Limit States of Serviceability 67 35.4 Other Limit States 67 36 CHARACTERISTIC AND DESIGN VALUES PARTUL AND FACTORS SAFEI”Y 67 36.1 Characteristic Strength of Materials 67 36.2 Characteristic Loads 67 36.3 Design Values 68 36.4 Partial Safety Factors 68 37 ANALYSIS -68 37.1 Analysis of Structure 68 8
  10. 10. PAGE38 LIMITSTATE COLLAPSE :FLEXURE OF 69 38.1 Assumptions 6939 LIMITSTATE COLLAPSE: OF COMPRESSION 70 39.1 Assumptions 70 39.2 Minimum Eccentricity 71 39.3 Short Axially Loaded Members in Compression 71 39.4 Compression Members with Helical Reinforcement 71 39.5 Members Subjected to Combined Axial Load and Uniaxial Bending 71 39.6 Members Subjected to Combined Axial Load and Biaxial Bending 71 39.7 Slender Compression Members 7140 LLWTSTATE OF-COLLAPSE : SW 72 40.1 Nominal Shear Stress 72 40.2 Design Shear Strength of Concrete 72 40.3 Minimum Shear Reinforcement 72 40.4 Design of Shear Reinforcement 72 40.5 Enhanced Shear Strength of Sections Close to Supports 7441 LJMITSTATE COLLAPSE OF : TORSION 74 41.1 General 74 4 1.2 Critical Section 75 4 1.3 Shear and Torsion 75 4 1.4 Reinforcement in Members Subjected to Torsion 7542 LIMITSTATKOF SERVICEABILITY: DEKIZC~ION 75 42.1 Flexural Members 7543 LIMITSTATE SERVICEABILITY: OF CRACKING 76 43.1 Flexural Members 76 43.2 Compression Members 76 4NNEXA LIST OF REFERRED INDIAN STANDARDS 77 ANNEXB STRUCTURAL DESIGN (WORKING STRESS METHOD) 80 B-l GENERAL 80 B-l.1 General Design Requirements 80 B- 1.2 Redistribution of Moments 80 B-l.3 Assumptions for Design of Members 80 B-2 PEaMIsstBLE STrtEssEs 80 B-2.1 Permissible Stresses in Concrete 80 B-2.2 Permissible Stresses in Steel Reinforcement 80 B-2.3 Increase in Permissible Stresses 80 B-3 I’iuu@ssm~~ Lam INCOMPRESSION MEMBEW 81 B-3.1 Pedestals and Short Columns with Lateral ‘Des 81 B-3.2 Short Columns with Helical Reinforcement 81 B-3.3 Long Columns 81 B-3.4 Composite Columns 81 9
  11. 11. IS 456 : 2ooo B-4 MYERS SUBJECTED TOCOMBINED Axw. LOAD BENDING AND 83 B-4.1 Design Based on Untracked Section 83 B-4.2 Design Based on Cracked Section 83 B-43 Members Subjected to Combined Direct Load and Flexure 83 B-5 SHEAR 83 B-5.1 Nominal Shear Stress 83 B-5.2 Design Shear Strength of Concrete 84 B-5.3 Minimum Shear Reinforcement 85 B-5.4 Design of Shear Reinforcement 85 B-5.5 Enhanced Shear Strength of Sections Close to Supports 85 B -6 TORSION 86 B-6.1 General 86 B-6.2 Critical Section 86 B-6.3 Shear and Torsion 86 B-6.4 Reinforcement in Members Subjected to Torsion 86ANNEX C CALCULATION OF DEFLECTION 88 C-l TOTAL DEFLECTION 88 C-2 SHORT-TERM DEFLECTION 88 C-3 DEFLECI-ION TOSHRINKAGE DUE 88 C-4 DE-ON DUETOCREEP 89ANNEX D SLABS SPANNING IN TWO DIRECTIONS 90 D-l RESTRAINED SLAIIS 90 D-2 SIMPLY SIJIWRTEDSLABS 90 ANNEX E EFFECTIVE LENGTH OF COLUMNS 92 ANNEX F CALCULATION OF CRACK WIDTH 95 ANNEX G MOMENTS OF RESISTANCE FOR RECTANGULAR AND T-SECTIONS 96 G- 1 RECTANGULAR SECIIONS 96 G- 1.1 Sections without Compression Reinforcement % G- 1.2 Sections with Compression Reinforcement 96 G-2 FLANGED SECTION 96 ANNEX H COMMITTEE COMPOSITION 98 10
  12. 12. IS456:2000 SECTION 1 GENERAL1 SCOPE EL - Earthquake loadk-1 This standard deals with the general structural use Es - Modulus of elasticity of steelof plain and reinforced concrete. Eccentricity1.1.1For the purpose of this standard, plain concrete J& - characteristic cube compressivestructures are those where reinforcement, if provided strength of concreteis ignored for~determinationof strength of the structure. xx - Modulus of rupture of concrete (flexural tensile strength)1.2 Special requirements of structures, such as shells,folded plates, arches, bridges, chimneys, blast resistant fa - Splitting tensile strength of concretestructures, hydraulic structures, liquid retaining fd - Design strengthstructures and earthquake resistant structures, covered fY - Characteristic strength of steelin respective standards have not been covered in thisstandard; these standards shall be used in conjunction 4 - Unsupported height of wallwith this standard. Hive- Effective height of wall L - Effective moment of inertia2 REFERENCES zc - Moment of inertia of the gross section excluding reinforcementThe Indian Standards listed in Annex A containprovisions which through reference in this text, 4 - Moment of intertia of cracked sectionconstitute provisions of this standard. At the time of K - Stiffness of memberpublication, the editions indicated were valid. All k - Constant or coefficient or factorstandards are subject to revision and parties to Ld - Development lengthagreements abased on this standard are encouraged to LL- Live load or imposed loadinvestigate the possibility of applying the most recenteditions of the standards indicated in Annex A. Lw - Horizontal distance between centres of lateral restraint3 TERMINOLOGY 1 - Length of a column or beam between adequate lateral restraints or theFor the purpose of this standard, the definitions given unsupported length of a columnin IS 4845 and IS 6461 (Parts 1 to 12) shall generallyapply. Effective span of beam or slab or effective length of column4 SYMBOLS Effective length about x-x axisFor the purpose of this standard, the following letter Effective length about y-y axissymbols shall have the meaning indicated against each, Clear span, face-to-face of supportswhere other symbols are used, they are explained at I’,,for shorter of the two spans at rightthe appropriate place: angles A - Area 4 - Length of shorter side of slab b - Breadth of beam, or shorter dimension Length of longer side of slab of a rectangular column lY - 4 - Distance between points of zero b ef - Effective width of slab moments in a beam bf - Effective width of flange Span in the direction in which 4 - k - Breadth of web or rib moments are determined, centre to D - Overall depth of beam or slab or centre of supports diameter of column; dimension of a Span transverse to I,, centre to centre 12 - rectangular column in the direction of supports under consideration 1’ - 1z for the shorter of the continuous Thickness of flange 2 Df - spans DL - Dead load M - Bending moment d - Effective depth of beam or slab m - Modular ratio d’ - Depth of compression reinforcement n - Number of samples from the highly compressed face P - Axial load on a compression member EC - ModuIus of elasticity of concrete Calculated maximum bearing pressure 4,) - 11
  13. 13. IS 456 : 2000 Yc, - Calculated maximum bearing pressure xl - Partial safety factor for material of soil - Percentage reduction in moment snl r - Radius E UC - Creep strain of concrete s - Spacing of stirrups or standard (T - chc Permissible stress in concrete in deviation bending compression T - Torsional moment OLX - Permissible stress in concrete in direct compression t - Wall thickness <T mc - Permissible stress in metal in direct V - Shear force compression W - Total load 0% - Permissible stress in steel in WL - Wind load compression W - Distributed load per unit area % - Permissible stress in steel in tension Wd - Distributed dead load per unit area 0,” - Permissible tensile stress in shear reinforcement WI - Distributed imposed load per unit area Design bond stress X - Depth of neutral axis Shear stress in concrete z - Modulus of section Maximum shear stress in concrete Z - Lever arm with shear reinforcement OZ, - B Angle or ratio Nominal shear stress r, - Partial safety factor for load Diameter of bar 12
  14. 14. IS456:2000 SECTION 2 MATERIALS, WORKMANSHIP, INSPECTION AND TESTING5 MATERIALS have no relation whatsoever with the characteristics guaranteed by the Quality Marking as relevant to that5.1 Cement cement. Consumers are, therefore, advised to go byThe cement used shall be any of the following and the the characteristics as given in the correspondingtype selected should be appropriate for the intended Indian Standard Specification or seek specialistuse: advise to avoid any problem in concrete making and a) 33 Grade ordinary Portland cement construction. conforming to IS 269 5.2 Mineral Admiitures b) 43 Grade ordinary Portland cement conforming to IS 8 112 5.2.1 Poz.zolanas 53 Grade ordinary Portland cement Pozzolanic materials conforming to relevant Indian c) conforming to IS 12269 Standards may be used with the permission of the engineer-in-charge, provided uniform blending with d) Rapid hardening Portland cement conforming cement is ensured. to IS 8~041 Portland slag cement conforming to IS 455 5.2.1.1 Fly ash (pulverizedfuel ash) e) Portland pozzolana cement (fly ash based) FIy ash conforming to Grade 1 of IS 3812 may be f) conforming to IS 1489 (Part 1) use?, as part replacement of ordinary Portland cement provided uniform blending with cement is ensured. g) Portland pozzolana cement (calcined clay based) conforming to IS 1489 (Part 2) 5.2.1.2 Silicafume h) Hydrophobic cement conforming to IS 8043 Silica fume conforming to a standard approved by the j) Low heat Portland cement conforming to deciding authority may be used as part replacement of IS 12600 cement provided uniform blending with the cement is ensured. k) Sulphate resisting Portland cement NOTE-The silica fume (very fine non-crystalline silicon conforming to IS 12330 dioxide)is a by-product the manufactmeof silicon, kmxilicon ofOther combinations of Portland cement with mineral or the like, from quartzand carbon in electric arc furnace. It is usually usedinpropoltion of 5’m lOpercentofthecementconbcntadmixtures (see 5.2) of quality conforming with of a mix.relevant Indian Standards laid down may also be usedin the manufacture of concrete provided that there are 5.2.1.3 Rice husk ashsatisfactory data on their suitability, such as Rice husk ash giving required performance andperformance test on concrete containing them. uniformity characteristics -may be used with the5.1.1 Low heat Portland cement conforming to approval of the deciding authority.IS 12600 shall be used with adequate precautions with NOTE--Rice husk ash is produced by burning rice husk andregard to removal of formwork, etc. contain large propotion of silica. To achieve amorphousstate,5.1.2 High alumina cement conforming to IS 6452 or rice husk may be burntat controlledtemperatum.It is necessary to evaluatethe productfrom a ptuticularsource for performnncesupersulphated cement conforming to IS 6909 may be and uniformitysince it can range from being as dekterious asused only under special circumstances with the prior silt when incorporatedin concmte. Waterdemnnd and dryingapproval of the engineer-in-charge. Specialist literature &i&age should be studied before using ria husk.may be consulted for guidance regarding the use of 5.2.u iuetakaolinethese types of cements. Metakaoline having fineness between 700 to 5.1.3 The attention of the engineers-in-charge and 900 m?/kg may be used as ~pozzolanic material in users of cement is drawn to the fact that quality of concrete. various cements mentioned in 5.1 is to be determined NOTE-Metaknoline is obtained by calcination of pun or on the basis of its conformity to the performance r&ledkaolinticclnyatatempexatumbetweea6soVand8xPc characteristics given in the respective Indian Standard followed by grind& to achieve a A of 700 to 900 n?/kg. Specification for thatcement. Any trade-mark or any The resultingmaterialhas high pozzolanicity. trade name indicating any special features not covered in the standard or any qualification or other special 5.2.2 Ground Granulated Blast Furnace Slag performance characteristics sometimes claimed/ Ground granulated blast furnace slag obtained by indicated on the bags or containers or in advertisements grinding granulated blast furnace slag conforming to alongside the ‘Statutory Quality Marking’ or otherwise IS 12089 may be used as part replacement of ordinary 13
  15. 15. IS 456 : 2000Portland cements provided uniform blending with free from injurious amounts of oils, acids, alkalis, salts,cement is ensured. sugar, organic materials or other substances that may be deleterious to concrete or steel.5.3 Aggregates Potable water is generally considered satisfactoryAggregates shall comply with the requirements of for mixing concrete. As a guide the followingIS 383. As far as possible preference shall be given to concentrations represent the maximum permissiblenatural aggregates. values:5.3.1 Other types of aggregates such as slag and a) To neutralize 100 ml sample of water, usingcrushed overbumt brick or tile, which may be found phenolphthalein as an indicator, it should notsuitable with regard to strength, durability of concrete require more than 5 ml of 0.02 normal NaOH.and freedom from harmful effects may be used for plain The details of test are given in 8.1 of ISconcrete members, but such aggregates should not 3025 (Part 22).contain more than 0.5 percent of sulphates as SO, and b) To neutralize 100 ml sample of water, usingshould not absorb more than 10 percent of their own mixed indicator, it should not require moremass of water. than 25 ml of 0.02 normal H$O,. The details of ‘test shall be as given in 8 of IS 30255.3.2 Heavy weight aggregates or light weight (Part 23).aggregates such as bloated clay aggregates and sinteredfly ash aggregates may also be used provided the cl Permissible limits for solids shall be as givenengineer-in-charge is satisfied with the data on the in Table 1.properties of concrete made with them. 5.4.1 In case of doubt regarding development of NOTE-Some of the provisions of the code would require strength, the suitability of water for making concrete moditicationwhen these aggnzgates used;specialistlitemtute are shall be ascertained by the compressive strength and may be consulted for guidance. initial setting time tests specified in 5.4.1.2 and 5.4.1.3.5.3.3 Size of Aggregate 5.4.1.1 The sample of water taken for testing shall represent the water proposed to be used for concreting,The nominal maximum size of coarse aggregate should due account being paid to seasonal variation. Thebe as large as possible within the limits specified but sample shall not receive any treatment before testingin no case greater than one-fourth of the minimum other than that envisaged in the regular supply of waterthickness of the member, provided that the concrete proposed for use in concrete. The sample shall be storedcan be placed without difficulty so as to surround all in a clean container previously rinsed out with similarreinforcement thoroughly and fill the comers of the water.form. For most work, 20 mm aggregate is suitable. S.4.1.2 Average 28 days compressive strength of atWhere there is no restriction to the flow of concrete least three 150 mm concrete cubes prepared with waterinto sections, 40 mm or larger size may be permitted. proposed to be used shall not be less than 90 percentIn concrete elements with thin sections, closely spaced of the average of strength of three similar concretereinforcement or small cover, consideration should be cubes prepared with distilled water. The cubes shallgiven to the use of 10 mm nominal maximum size. be prepared, curedand tested in accordance with thePlums above 160 mm and up to any reasonable size requirements of IS 5 16.may be used in plain concrete work up to a maximum 5.4.1.3 The initial setting time of test block made withlimit of 20 percent by volume of concrete when theappropriate cement and the water proposed to bespecifically permitted by the engineer-in-charge. The used shall not be less than 30 min and shall not differplums shall be distributed evenly and shall be not closer by& 30min from the initial setting time of controlthan 150 mm from the surface. test block prepared with the same cement and distilled5.3.3.1 For heavily reinforced concrete members as water. The test blocks shall be preparedand tested inin the case of ribs of main beams, the nominal accordance with the requirements off S 403 1 (Part 5).maximum size of the aggregate should usually be 5.4.2 The pH value of water shall be not less than 6.restricted to 5 mm less than the minimum clear distancebetween the main bars or 5 mm less than the minimum 5.4.3 Sea Watercover to the reinforcement whichever is smaller. Mixing or curing of concrete with sea water is not 5.3.4 Coarse and fine aggregate shall be batched recommended because of presence of harmful salts in separately. All-in-aggregate may be used only where sea water. Under unavoidable circumstances sea water specifically permitted by the engineer-in-charge. may be used for mixing or curing in plain concrete with no embedded steel after having given due consideration 5.4 Water to possible disadvantages and precautions including use Water used for mixing and curing shall be clean and of appropriate cement system. 14
  16. 16. lS456:2000 ‘lhble 1 Permissible Limit for !Wids (claust? 5.4)SI -apu Permb?dbleLImlt,No. Maxi) organic IS 3a25 (Pal-l18) 2(Jomgllii) Inorganic IS 3025 (yalt 18) 3ooomo/Liii) Sulphaki (us SOJ IS302s(Part24) amo/liv) Chlorides (as Cl) IS 3025 (part 32) 2ooompll for fxmaetc not Containing embcd~sti mdsoomg/l for leInfolced collcntc worlrv) Suspfmdedmatter IS 3025 (Palt 17) 2(xJom%l5.4.4 Water found satisfactory for mixing is also 5.6.1 All reinforcement shall be free from loose millsuitable for curing concrete. However, water used for scales, loose rust and coats of paints, oil, mud or anycuring should not produce any objectionable stain or other substances which may destroy or reduce bond.unsightly deposit on the concrete surface. The presence Sand blasting or other treatment is recommended toof tannic acid or iron compounds is objectionable. clean reinforcement. 5.6.2 Special precautions like coating of reinforcement5.5 Admixtures may be required for reinforced concrete elements in5.5.1 Admixture, if used shall comply with IS 9103. exceptional cases and for~rehabilitation of structutes.Previous experience with and data on such materials Specialist literature may be referred to in such cases.should be considered in relation to the likely standa& of 5.6.3 The modulus of elasticity of steel shall be takensupervisionand workmanshipto the work being specified, as 200 kN/mm*. The characteristic yield strength of55.2 Admixtures should not impair durability of different steel shall be assumed as the minimum yieldconcrete nor combine with the constituent to form stress/O.2percent proof stress specified in the relevantharmful compounds nor increase the risk of corrosion Indian Standard.of reinforcement. 5.7 Storage of Materials55.3 The workability, compressive strength and theslump loss of concrete with and without the use of Storage of materials shall be as described in IS 4082.admixtures shall be established during the trial mixes 6 CONCRETEbefore use of admixtures.5.5.4 The relative density of liquid admixtures shall 6.1 Gradesbe checked for each drum containing admixtures and The concrete shall be in grades designated as percompared with the specified value before acceptance. Table 2.5.5.5 The chloride content of admixtures shall 6.1.1 The characteristic strength is defined as thebe independently tested for each batch before strength of material below which not more thanacceptance. 5 percent of the test results are expectedto fall.5.5.6 If two or more admixtures are used 6.1.2 The minimum grade of concrete for plain andsimultaneously in the same concrete mix, data should reinforced concrete shall be as per Table 5.be obtained to assess their interaction and to ensure 61.3 Concrete of grades lower than those given intheir compatibility. Table-5 may be used for plain concrete constructions, 5.6 -Reinforcement lean concrete, simple foundations, foundation for masonry walls and other simple or temporary The reinforcement shall be any of the following: reinforced concrete construction. 4 Mild steel and medium tensile steel bars conforming to IS 432 (Part 1). 6.2 Properties of Concrete b) High strength deformed steel barsconforming 63.1 Increase of Strength with Age to IS 1786. There is normally a gain of strength beyond 28 days. cl Hard-drawn steel wire fabric conforming to The quantum of increase depends upon the grade and IS 1566. type of cement, curing and environmental conditions, 4 Structural steel conforming to Grade A of etc. The design should be based on 28 days charac- IS 2062. teristic strength of concrete unless there is a evidence to 15
  17. 17. IS 456 : 2000 Table 2 Grades cif Concrete (Clau.re6.1,9.2.2, 15.1.1 and36.1) whereGroup Grade Designation SpecifiedCharacte~tk E, is the short term static modulus of elasticity in Compressive Streng$b of 150 mm Cube at 28 Days in N/mm*. N/mmz Actual measured values may differ by f 20 percent (1) (2) (3) from the values dbtained from the above expression.Ordinary M 10 10Concrete M 15 6.2.4 Shrinkage 15 M 20 20 The total shrinkage of concrete depends upon theStandard M 25 25 constituents of concrete, size of the member andConcrete M 30 30 environmental conditions. For a given humidity and M 35 35 temperature, the total shrinkage of concrete is most M40 40 M 45 45 influenced by the total amount of water present in the M JO 50 concrete at the time of mixing and, to a lesser extent, M 55 55 by the cement content.High M60 60 6.2.4.1 In the absence of test data, the approximateStrength M65 65Concrete M70 70 value of the total shrinkage strain for design may be M75 75 taken as 0.000 3 (for more information, see-IS 1343). M 80 80 NOTES 6.2.5 Cmep of Concrete 1 In the designationof concrete mix M mfm to the mix and the number to the specified compressive strengthof 150 mm size Creep of concrete depends,in addition to the factors cube at 28 days, expressed in N/mn?. listed in 6.2.4, on the stress in the concrete, age at 2 For concreteof compressivestrength greata thanM 55, design loading and the duration of loading. As long as the parametersgiven in the stand& may not be applicable and the stress in concrete does not exceed one-third of its values may be obtoined from specialized literatures and characteristic compressive strength, creep may be experimentalresults. assumed to be proportional to the stress.justify a higher strength for a particular structure due to 6.25.11n the absence of experimental data and detailedage. information on the effect of the variables, the ultimate6.2.1.1 For concrete of grade M 30 and above, the creep strain may be estimated from the followingrateof increase of compressive strength with age shall values of creep coefficient (that is, ultimate creep strain/be based on actual investigations. elastic strain at the age of loading); for long span structure, it is advisable to determine actual creep6.2.1.2 Where members are subjected to lower direct strain, likely to take place:load during construction, they should be checked forstresses resulting from combination of direct load and Age at Loading Creep Coeficientbending during construction. 7 days 2.26.2.2 Tensile Strength of Concrete 28 days 1.6The flexural and splitting tensile strengths shall be 1 year 1.1obtained as described in IS 516 and IS 5816 NOTE-The ultimatecreepstrain,estimatedas described aboverespectively. When the designer wishes to use an does not include the elastic strain.estimate of the tensile strength from the compressivestrength, the following formula may be used: 6.2.6 Thermal Expansion Flexural strength, f, = 0.7.& N/mm2 The coefficient df thermal expansion depends on nature of cement, the aggregate, the cement content, thewheref& is the characteristic cube compressive strength relative humidity and the size of sections-The valueof concrete in N/mmz. of coefficient of thermal expansion for concrete with6.2.3 Elastic Deformation different aggregates may be taken as below:The modulus of elasticity is primarily influenced by npe of Aggregate Coeficient of Thermalthe elastic properties of the aggregate and to a lesser Expansion for CommtePCextent by the conditions of curing qd age of the Quartzite 1.2 to 1.3 x 10-Sconcrete, the mix proportions and the type of cement.The modulus of elasticity is normally related to the Sandstone 0.9 to 1.2 x 1cPcompressive strength of concrete. Granite 0.7 to 0.95 x 10-J Basalt O.% 0.95 x lo5 to6.2.3.1 The modulus of elasticity of concrete can be Limestone 0.6 t@.9 x 10sassumed as follows: 16
  18. 18. IS 456 : 20007 WORKABILITY OF CONCRETE7.1 The concrete mix proportions chosen should be be compacted with the means available. Suggestedsuch that the concrete is of adequate workability for ranges of workability of concrete measured inthe placing conditions of the concrete and can properly accordance with IS 1199 are given below: Placing Conditions Degree of Slump Workability (mm) (1) (2) (3)Blinding concrete; Very low See 7.1.1Shallow sections;Pavements using pavers IMass concrete; Low 25-75Lightly reinforcedsections in slabs,beams, walls, columns;Floors;Hand placed pavements;Canal lining;Strip footingsHeavily reinforced Medium 50-100sections in slabs,beams, walls, columns; 75-100Slipform work;Pumped concrete 1Trench fill; High 100-150In-situ pilingTremie concrete I Very high See 7.1.2 NOTE-For most of the placing conditions, internal vibrators (needle vibrators) are suitable. The diameter of tbe needle shall be determined based on the density and spacing of reinforcement bars and thickness of sections. For tremie concrete, vibrators am not rewired to be used (see &SO 13.3).7.1.1 In the ‘very low’ category of workability where a suitably low permeability is achieved by having anstrict control is necessary, for example pavement adequate cement content, sufficiently low free water/quality concrete, measurement of workability by cement~ratio,~byensuring complete compaction of thedetermination of compacting factor will be more concrete, and by adequate curing.appropriate than slump (see IS 1199) and a value of The factors influencing durability include:compacting factor of 0.75 to 0.80 is suggested. 7.1.2 In the ‘very high’ category of workability, 4 the environment;measurement of workability by determination of flow b) the cover to embedded steel;will be appropriate (see IS 9103). cl the typeand_quality of constituent materials;8 DURABILITY OF CONCRETE 4 the cement content and water/cement ratio of8.1 General the concrete;A durable concrete is one that performs satisfactorily d workmanship, to obtain full compaction andin the working environment during its anticipated efficient curing; andexposure conditions during service. The materials andmix proportions specified and used should be such as f) the shape and size of the member.to maintain its integrity and, if applicable, to protect The degree of exposure anticipated for the concreteembedded metal from corrosion. during its service life together with other relevant8.1.1 One of the main characteristics influencing the factors relating to mix composition, workmanship,durability of concrete is its permeability to the ingress design and detailing should be considered. The of water, oxygen, carbon dioxide, chloride, sulphate and concrete mix to provide adequate durability under these other potentially deleterious substances. Impermeability conditions should be chosen taking account of the is governed by the constituents and workmanship used accuracy of current testing regimes for control andin making the concrete. with normal-weight aggregates compliance as described in this standard. 17
  19. 19. IS 456 : 20008.2 Requirements for Durability 8.2.2.2 Abrasive8.2.1 Shape and Size of Member Specialist literatures may be referred to for durabilityThe shape or design details of exposed structures requirementsof concrete surfaces exposed to abrasiveshould be such as to promote good drainage of water action,for example, in case of machinery and metal tyres.and to avoid standing pools and rundown of water. 8.2.2.3 Freezing and thawingCare should also be taken to minimize any cracks thatmay collect or transmit water. Adequate curing is Where freezing and thawing actions under wetessential to avoid the harmful effects of early loss of conditions exist, enhanced durability can be obtainedmoisture (see 13S).Member profiles and their by the use of suitable air entraining admixtures. Whenintersections with other members shall be designed and concrete lower than grade M 50 is used under thesedetailed in a way to ensure easy flow of concrete and conditions, the mean total air content by volume ofproper compaction during concreting. the fresh concrete at the time df delivery into the construction should be:Concrete is more vulnerable to deterioration due tochemical or climatic attack when it is in thin sections, Nominal Maximum Size Entrained Airin sections under hydrostatic pressure from one side Aggregate Percentageonly, in partially immersed sections and at corners andedges of elements. The life of the strycture can be WWlengthened by providing extra cover to steel, by 20 5flchamfering the corners or by using circular cross- 40 4flsections or by using surface coatings which prevent orreduce the ingress of water, carbon dioxide or Since air entrainment reduces the strength, suitableaggressive chemicals. adjustments may be made in the mix design for8.2.2 Exposure Conditions achieving required strength.8.2.2.1 General environment 8.2.2.4 Exposure to sulphate attackThe general environment tc, which the concrete will Table 4 gives recommendations for the type of cement,be exposed during its working life is classified into maximum free water/cement ratio and minimumfive levels of severity, that is, mild, moderate, severe, cement content, which are required at different sulphatevery severe and extreme as described in Table 3. concentrations in near-neutral ground water having Table 3 Environmental Exposure Conditions pHof6to9. (Chwes 8.2.2.1 and 35.3.2) For the very high sulphate concentrations in Class 5 conditions, some form of lining such as polyethyleneSl No. Environment Exposure Conditions or polychloroprene sheet; or surface coating based on(1) (2) (3) asphalt, chlorinated rubber, epoxy; or polyurethanei) Mild Concrete surfaces protected against materials should also be used to prevent access by the weatheror aggressiveconditions,except those situatedin coastal area. sulphate solution.ii) Moderate Concretesurfaces shelteredfrom severe 8.2.3 Requirement of Concrete Cover rain or freezing whilst wet Concrete exposedto condensation rain and 8.2.3.1 The protection of the steel in concrete against Concretecontinuously underwater corrosion depends upon an adequate thickness of good Concretein contact or buriedundernon- quality concrete. aggressive soil/groundwater Concrete surfaces sheltered from 8.2.3.2 The nominal cover to the reinforcement shall saturatedsalt air in coastal area be provided as per 26.4. iii) Severe Concrete surfaces exposed to severe rain, alternate wetting and drying or 0.2.4 Concrete Mix Proportions occasional freezing whilst wet or severe condensation. 8.2.4.1 General Concletecompletelyimmrsedinseawnter The free water-cement ratio is an important factor in Concreteexposed to coastalenvironment governing the durability of concrete and should always iv) Very severe Concrete surfaces exposed to sea water spray,corrosivefumes or severe freezing be the lowest value. Appropriate values for minimum conditions whilst wet cement content and the maximum free water-cement Concrete in contact with or buried ratio are given in Table 5 for different exposure underaggressive sub-soil/groundwater conditions. The minimum cement content and -4 Extreme Surfaceof membersin tidal zone maximum water-cement ratio apply to 20 mm nominal Members in direct contact with liquid/ maximum size aggregate. For other sizes of aggregate solid aggressive chemicals they should be changed as given in Table 6. 18
  20. 20. IS 456 : 20008.2.4.2 Maximum cement content been given in design to the increased risk of crackingCement content not including fly ash and ground due to drying shrinkage in.thin sections, or to earlygranulated blast furnace slag in excess of 450 kg/x$ thermal cracking and to the increased risk of damageshould not be used unless special consideration has due to alkali silica reactions. Table 4 Requirements for Concrete Exposed to Sulphate Attack (Clauses 8.2.2.4 and 9.1.2)SI ChSS Concentration of Sulphates, Type ofCement Dense, Fully Compacted concrete.No. Expressed a~ SO, Made with 20 mm Nominal r . Maximum Size Aggregates In Soil Complying with IS 383 Total SO, SO,in In Ground r . 2:l water: Water Soil Extract Minimum Maximum Cement Face Water- Content Cement ~kg/m’ Ratio &d @ (1) (2) (3) (4) (5) (6) (7) (8) 0 1 TraCeS Less than LesSthan Ordinary Portland 280 0.55 (< 0.2) 1.0 0.3 cement or Portland slag cement or Portland pozzolana cement ’ ii) 2 0.2 to 1.oto 0.3 to Ordinary Portland 330 0.50 0.5 1.9 1.2 cement or Portland slag cement or Portland pozzolana cement Supersulphated 310 0.50 cement or sulphate resisting Portland cement iii) 3 0.5 to 1.9 to 1.2 to Supersulphated 330 0.50 1.0 3.1 2.5 cement or sulphate resisting Portland cement Portland pozzolana 350 0.45 cement or Podand slag cement iv) 4 1.0to 3.1 to 2.5 to Supersulphated 370 0.45 2.0 5.0 5.0 or sulphate resisting Portland cement v) 5 More than More than More than Sulphate resisting 400 0.40 2.0 5.0 5.0 Portland cement or superrulphated cement with protective coatingsNOTES 1 Cement content given in this table is irrespective of grades of cement.2 Use of supersulphated cement is generally restricted where the prevailing temperature is above 40 “c.3 Supersulphated cement gives~an acceptable life provided that the concrete is dense and prepared with a water-cement mtio of 0.4 or less, in mineral acids, down to pH 3.5. 4 The cement contents given in co1 6 of this table are the minimum recommended. For SO, contents near tbe upper limit of any class, cement contents above these minimum are advised. 5 For severe conditions, such as thin sections under hydrostatic pressure on one side only and sections partly immersed, considerations should be given to a further reduction of water-cement ratio. 6 Portland slag cement conforming to IS 455 with slag content more than 50 percent exhibits better sulphate resisting properties. 7 Where chloride is encountered along with sulphates in soil or ground water, ordinary Portland cement with C,A content from 5 to 8 percent shall be desirable to be used in concrete, instead of sulphate resisting cement. Alternatively, Portland slag cement conforming to IS 455 having more than 50 percent slag or a blend of ordinary Portland cement and slag may be used provided sufficient information is available on performance of such blended cements in these conditions. 19
  21. 21. IS 456 : 20008.2.5 Mix Constituents expansion and disruption of concrete. To prevent this, the total water-soluble sulphate content of the concrete8.2.5.1 General mix, expressed as SO,, should not exceed 4 percent byFor concrete to be durable, careful selection of the mix mass of the cement in the mix. The sulphate contentand materials is necessary, so that deleterious should be calculated as the total from the variousconstituents do not exceed the limits. constituents of the mix. The 4 percent limit does not apply to concrete made8.2.5.2 Chlorides in concrete with supersulphated cement complying with IS 6909.Whenever there is chloride in concrete there is an 8.2.5.4 Alkali-aggregate reactionincreased risk of corrosion of embedded metal. Thehigher the chloride content, or if subsequently exposed Some aggregates containing particular varieties ofto warm moist conditions, the greater the risk of silica may be susceptible to attack by alkalis (N%Ocorrosion. All constituents may contain chlorides and and %O) originating from cement or other sources,concrete may be contaminated by chlorides from the producing an expansive reaction which can causeexternal environment. To minimize the chances of cracking and disruption of concrete. Damage todeterioration of concrete from harmful chemical salts, concrete from this reaction will normally only occurthe levels of such harmful salts in concrete coming when .a11 following are present together: thefrom concrete materials, that is, cement, aggregates a) A high moisture level, within the concrete;water and admixtures, as well as by diffusion from the b) A cement with high alkali content, or anotherenvironment should be limited. The total amount of source of alkali;chloride content (as Cl) in the concrete at the time ofplacing shall be as given in Table 7. c) Aggregate containing an alkali reactive constituent.The total acid soluble chloride content should becalculated from the mix proportions and the measured Where the service records of particular cement/chloride contents of each of the constituents. Wherever aggregate combination are well established, and do not -possible, the total chloride content of the concrete include any instances of cracking due to alkali-should be determined. aggregate reaction, no further precautions should be necessary. When the materials are unfamiliar,8.2.5.3 Sulphates in concrete precautions should take one or more of the followingSulphates are present in most cements and in some forms:aggregates; excessive amounts of water-solublesulphate from these or other mix constituents can cause a) Use of non-reactive aggregate from alternate sources. Table 5 Minimum CementContent, Maximum Water-Cement Ratio and Minimum Grade of Concrete for Different Exposures with Normal Weight Aggregates of 20 mm Nominal Maximum Size (Clauses 6.1.2, 8.2.4.1 and9.1.2)SI Exposure Plain Concrete Reinforced ConcreteNo. / - * - Minimum Maximum Minimum Minimum Maximum Minimum Cement Free Water- Grade of Cement Free Water- Grade of Content Cement Ratio Concrete’ Content Cement Ratio Concrete kg/m’ kg/m’ 1) (2) (3) (4) (5) (6) (7) 0-9 0 Mild 220 0.60 300 0.55 M 20 iii) Moderate 240 0.60 M 15 300 0.50 M 25 iii) Severe 250 0.50 M 20 ~320 0.45 M 30 iv) Very severe 260 0.45 M 20 340 0.45) M 35 v) Extreme 280 0.40 M25 360 0.40 M40 NOTES 1 Cement content prescribed in this table is irrespective of the grades of cement and it is inclusive of ad&ons mentioned in 5.2. The additions such as fly ash or ground granulated blast furnace slag may be taken into account in the concrete composition with respect to Ihe cement content and water-cement ratio if the suitability is established and as long as the maximum amounts taken into account do not exceed the limit of pozzolona and slag specified in IS 1489 (Part I) and IS 455 respectively. 2 Minimum gradefor plain concrete under mild exposure condition is not specified. 20

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