IS 456: 2000 Plain and Reinforced Concrete - Code of Practice Amendments PDF

AMENDMENT NO. 4 – MAY 2013 TO IS 456: 2000 PLAIN AND REINFORCE CONCRETE - CODE OF PRACTICE Sl. No. Clause Before Amendment After Amendment...

AMENDMENT NO. 4 – MAY 2013 TO IS 456: 2000 PLAIN AND REINFORCE CONCRETE - CODE OF PRACTICE Sl. No. Clause Before Amendment After Amendment Aggregates shall comply with the requirements of IS 383. As 5.3 1. far as possible preference shall be given to natural Aggregates shall comply with the requirements of IS 383. Aggregates aggregates. Coarse and fine aggregate shall be batched separately. All- 2. 5.3.4 in-aggregate may be used only where specifically permitted Coarse and fine aggregate shall be batched separately. by the engineer-in-charge. Water used for mixing and curing shall be clean and free Water, natural or treated, used for mixing and curing shall be 5.4 from injurious amounts of oils, acids, alkalis, salts, sugar, clean and free from injurious amounts of oils, acids, alkalis, salts, 3. Water organic materials or other substances that may be sugar, organic materials or other substances that may be deleterious to concrete or steel. deleterious to concrete or steel. Mixing or curing of concrete with sea water is not Sea water shall not be used for mixing or curing of concrete recommended because of presence of harmful salts in sea because of presence of harmful salts. Under unavoidable water. Under unavoidable circumstances sea water may be 5.4.3 circumstances sea water may be used for mixing or curing in plain 4. used for mixing or curing in plain concrete with no Sea Water concrete with no embedded steel after having given due embedded steel after having given due consideration to consideration to possible disadvantages and precautions possible disadvantages and precautions including use of including use of appropriate cement system. appropriate cement system. The amount of admixture added to a mix shall be recorded in the production record. Redosing of admixtures is not normally permitted. In special circumstances, if necessary, additional dose of admixture may be added at a project site and mixed 5.5.7 – 5. - adequately in mixer itself to regain the workability of concrete New clause added with the mutual agreement between the producer/supplier and the purchaser/user of concrete. However the producer/supplier shall assure the ultimate quality of concrete supplied by him and maintain record of quantity and time of addition.  In this amendment, Classification of Concrete has been changed. M60Gr. has been shifted Table 2 – to Standard concrete and 6. Grades of Concrete from Grades M85 to M100 are added to High strength concretes. In note to M55 is replaced with M60. A durable concrete is one that performs satisfactorily in the A durable concrete is one that performs satisfactorily in the working environment during its anticipated exposure working environment during its anticipated exposure conditions 8.1 conditions during service. The materials and mix 7. during service life. The materials and mix proportions specified General proportions specified and used should be such as to and used should be such as to maintain its integrity and, if maintain its integrity and, if applicable, to protect applicable, to protect embedded metal from corrosion. embedded metal from corrosion. NOTES to Table 5 Minimum Cement Cement content prescribed in this table is irrespective of the Cement content prescribed in this table is irrespective of grades Content, Maximum grades of cement and it is inclusive of additions mentioned and types of cement and is inclusive of mineral admixtures Water-Cement Ratio in 5.2. The additions such as fly ash or ground granulated mentioned in 5.2. The mineral admixtures such as fly ash or and Minimum Grade blast furnace slag may be taken into account in the concrete ground granulated blast furnace slag shall be taken into account 8. of Concrete for composition with respect to the cement content and water- in the concrete composition with respect to the cement content Different Exposures cement ratio if the suitability is established and as long as and water-cement ratio not exceeding the limit of fly ash and slag with Normal Weight the maximum amounts taken into account do not exceed specified in IS 1489(Part I) and IS 455 respectively, beyond which Aggregates of 20 the limit of pozzolona and slag specified in IS 1489 (Part I) these additions though permitted, shall not be considered for mm Nominal and IS 455 respectively. these purposes. Maximum Size 3. The minimum cement content, maximum free water-cement NOTES to Table 5 – 9. Only 2 note items mentioned. ratio and minimum grade of concrete are individually related to Note 3 added exposure.  b) Use of low alkali ordinary Portland cement having total alkali content not more than 0.6 percent (as Na2O b) Use of low alkali ordinary Portland cement having total alkali equivalent). content not more than 0.6 percent (as Na2O equivalent). Further advantage can be obtained by use of fly ash (Grade Further advantage can be obtained by use of flyash conforming to 8.2.5.4 1) conforming to IS 3812 or granulated blast furnace slag IS 3812 (Part I) or ground granulated blast furnace slag 10. Alkali-aggregate conforming to IS 12089 as part replacement of ordinary conforming to IS 12089 as part replacement of ordinary Portland reaction Portland cement (having total alkali content as Na2O cement (having total alkali content as Na2O equivalent not more equivalent not more than 0.6 percent), provided fly ash than 0.6 percent), provided fly ash content is at least 25percent content is at least 20 percent or slag content is at least 50 or slag content is at least 50 percent. percent. At sites where alkali concentrations are high or may become very high, the ground water should be lowered by drainage At sites where alkali concentrations are high or may become very so that it will not come into direct contact with the high, the ground water should be lowered by drainage so that it 8.2.6.2 concrete. 11. will not come into direct contact with the concrete. Drainage Additional protection may be obtained by the use of Additional protection may be obtained by the use of suitable chemically resistant stone facing or a layer of plaster of Paris impermeable barriers. covered with suitable fabric, such as jute thoroughly impregnated with bituminous material. As the guarantor of quality of concrete used in the construction, the constructor shall carry out the mix design and the mix so designed (not the method of design) shall be approved by the As the guarantor of quality of concrete used in the employer within the limitations of parameters and other construction, the constructor shall carry out the mix design 9.2 stipulations laid down by this standard. If so desired, the and the mix so designed (not the method of design) shall be 12. Design Mix Concrete employer shall be provided with supporting data including graphs approved by the employer within the limitations of 9.2.1 showing strength versus water cement ratio for range of parameters and other stipulations laid down by this proportions, complete trial mix proportioning details to standard. substantiate the choice of cement content, fine and coarse aggregate content, water, mineral admixtures, chemical admixtures etc., The mix shall be designed to produce the grade of concrete The mix shall be designed to produce the grade of concrete having the required workability and a characteristic strength not having the required workability and a characteristic strength less than appropriate values given in Table 2. Proportion/grading not less than appropriate values given in Table 2. The target 13. 9.2.2 of aggregates shall be made by trial in such a way as to make mean strength of concrete mix should be equal to the densest possible concrete. The target mean strength of concrete characteristic strength plus 1.65 times the standard mix should be equal to the characteristic strength plus 1.65 times deviation. the standard deviation.  In this amendment, M55 Table 8 and M60 has been added 14. Assumed Standard in the amended version to Deviation the Grade of Concrete. Also note 2 is added. To avoid confusion and error in batching, consideration should be To avoid confusion and error in batching, consideration given to using the smallest practical number of different concrete should be given to using the smallest practical number of mixes on any site or in any one plant. In batching concrete, the different concrete mixes on any site or in any one plant. In quantity of both cement and aggregate shall be determined by batching concrete, the quantity of both cement and mass; admixture, if solid, by mass; liquid admixture may however aggregate shall be determined by mass; admixture, if solid, be measured in volume or mass; water shall be weighed or 10.2 by mass; liquid admixture may however be measured in measured by volume in a calibrated tank (see also IS 4925). 15. Batching volume or mass; water shall be weighed or measured by For large and medium project sites, the concrete shall be sourced volume in a calibrated tank (see also IS 4925). Ready-mixed from Ready mixed concrete plants or from captive on site or off concrete supplied by ready-mixed concrete plant shall be site automatic batching and mixing plants. The concrete preferred. For large and medium project sites the concrete produced and supplied by ready-mixed concrete plants shall be in shall be sourced from ready mixed concrete plants or from accordance with IS 4926. In case of concrete from captive on site on site or off site batching and mixing plants (see IS 4926). or off site automatic batching and mixing plants, similar quality control shall be followed. Except where it can be shown to the satisfaction of the engineer-in-charge that supply of properly graded aggregate The grading of aggregate shall be controlled by obtaining the of uniform quality can be maintained over a period of work, coarse aggregate in different sizes and blending them in right the grading of aggregate should be controlled by obtaining proportions, the different sizes being stocked in separate stock the coarse aggregate in different sizes and blending them in piles. The material should be stock-piled for several hours 16. 10.2.1 the right proportions when required, the different sizes preferably a day before use. The grading of coarse and fine being stocked in separate stock-piles. The material should aggregate should be checked as frequently as possible, the be stock-piled for several hours preferably a day before use. frequency for a given job being determined by the engineer-in The grading of coarse and fine aggregate should be checked charge to ensure that the specified grading is maintained. as frequently as possible, the frequency for a given job being determined by the engineer-in charge to ensure that  the specified grading is maintained. The accuracy of measuring equipment shall be within ±2 percent of the quantity of cement and mineral admixtures being measured and within ±3percent of the quantity of aggregate, chemical admixtures and water being measured. In a batching The accuracy of the measuring equipment shall be within + plant, the concrete production equipment shall be calibrated 2 percent of the quantity of cement being measured and 17. 10.2.2 initially at the time of installation or reconditioning of the within + 3 percent of the quantity of aggregate, admixtures equipment and subsequently at the following intervals: and water being measured. a)Mechanical/knife edge systems : At least once every two months b)Electrical / load cell systems : At least once every three months Proportion/Type and grading of aggregates shall be made by All ingredients of concrete shall be used by mass except water 18. 10.2.3 trial in such a way so as to obtain densest possible concrete. and chemical admixtures which may be by volume. All ingredients of the concrete should be used by mass only. It is important to maintain the water-cement ratio constant at its It is important to maintain the water-cement ratio constant correct value. To this end, determination of moisture contents in at its correct value. To this end, determination of moisture both fine and coarse aggregates shall be made as frequently as contents in both fine and coarse aggregates shall be made possible, the frequency for a given job being determined by the as frequently as possible, the frequency for a given job engineer-in-charge according to weather conditions. The amount- being determined by the engineer-in-charge according to of the added water shall be adjusted to compensate for any weather conditions. The amount-of the added water shall observed variations in the moisture contents. For the be adjusted to compensate for any observed variations in determination of moisture content in the aggregates, IS 2386 19. 10.2.5 the moisture contents. For the determination of moisture (Part 3) may be referred to. Where batching plants are used, it is content in the aggregates, IS 2386 (Part 3) may be referred recommended to determine moisture content by moisture to. To allow for the variation in mass of aggregate due to probes fitted to the batching plants. To allow for the variation in variation in their moisture content, suitable adjustments in mass of aggregate due to variation in their moisture content, the masses of aggregates shall also be made. In the absence suitable adjustments in the masses of aggregates shall also be of -exact data, only in the case of nominal mixes, the made. In the absence of -exact data, only in the case of nominal amount of surface water may be estimated from the values mixes, the amount of surface water may be estimated from the given in Table 10. values given in Table 10.  Concrete shall be mixed in mechanical mixer (see also IS 1791 and Concrete shall be mixed in a mechanical mixer. The mixer IS 12119). It shall be ensured that stationary or central mixers and should comply with IS 1791 and IS 12119. The mixers shall truck mixers shall comply with the performance criteria of mixing be fitted with water measuring (metering) devices. The efficiency as per IS 4634. Mixing efficiency test shall be performed 10.3 20. mixing shall be continued until there is a uniform at least once in a year. The mixers shall be fitted with water Mixing distribution of the materials and the mass is uniform in measuring (metering) devices. The mixing shall be continued until colour and consistency. If there is segregation after there is a uniform distribution of the materials and the mass is unloading from the mixer, the concrete should be remixed. uniform in colour and consistency. If there is segregation after unloading from the mixer, the concrete should be remixed. As a guidance, the mixing time shall be at least 2min for For guidance, the mixing time shall be at least 2 min. For conventional free fall (drum) batch type concrete mixers. For other types of more efficient mixers, manufacturers’ 21. 10.3.1 other types of more efficient mixers, manufacturers’ recommendations shall be followed; for hydrophobic recommendations shall be followed. cement it may be decided by the engineer-in-charge. Dosages of retarders, plasticisers and superplasticisers shall be Dosages of retarders, plasticisers and superplasticisers shall restricted to 0.5, 1.0 and 2.0 percent respectively by mass of be restricted to 0.5, 1.0 and 2.0 percent respectively by cementitious materials; however, the dosages of polycarboxylate 22. 10.3.3 weight of cementations’ materials and unless a higher value based admixtures shall not exceed 1.0percent. A higher value of is agreed upon between the manufacturer and the above admixtures may be used, if agreed upon between the constructor based on performance test. manufacturer and the constructor based on performance test relating to workability, setting time and early age strength. In this amendment, The 11.1 23. tolerances on shapes, lines General and dimensions are revised.  Joints are a common source of weakness and, therefore, it is Joints are a common source of weakness and, therefore, it is desirable to avoid them. If this is not possible, their number 13.4 desirable to avoid them. If this is not possible, their number shall shall be minimized. Concreting shall be carried out 24. Construction Joints be minimized. Concreting shall be carried out continuously up to continuously up to construction joints, the position and and Cold Joints construction joints, the position and arrangement of which shall arrangement of which shall be indicated by the designer. be indicated by the designer. Construction joints should comply with IS 11817. In this amendment, The characteristic compressive strength compliance 25. Table 11 requirements are revised. In the revision it is same for M15 and above grades. Note 2 is added. In some cases the support moments calculated from Table 26 for 24.4.1 In some cases the support moments calculated from Table adjacent panels may differ significantly. The following procedure 26 for adjacent panels may differ significantly. The following Restrained Slab with may be adopted to adjust them. 26. procedure may be adopted to adjust them. Unequal Conditions a) Calculate the sum of the midspan moments and the a) Calculate the sum of moments at midspan and at Adjacent Panels average of the support moments (neglecting signs) for supports (neglecting signs). each panel. 26.2.1 3) For plain cement concrete of M15grade with nominal Development Length 27. Only 2 Note items mentioned. reinforcement, the design bond stress may be taken as 1.0 of Bars - NOTES – N/mm2. Note 3 added 26.2.1.1 For deformed bars conforming to IS 1786 these values shall be Design bond stress For deformed bars conforming to IS 1786 these values shall increased by 60 percent. For bars in compression, the values of in limit state method be increased by 60 percent. For bars in compression, the bond stress for bars in tension shall be increased-by 25 percent. 28. for plain bars in values of bond stress for bars in tension shall be increased- For fusion bonded epoxy coated deformed bars, design bond tension shall be as by 25 percent. stress values shall be taken as 80 percent of the values given in below: the above table.  The surface width of the cracks should not, in general, The surface width of the cracks should not, in general, exceed 0.3 exceed 0.3 mm in members where cracking is not harmful mm in members where cracking is not harmful and does not have and does not have any serious adverse effects upon the any serious adverse effects upon the preservation of reinforcing preservation of reinforcing steel nor upon the durability of steel nor upon the durability of the structures. In members where the structures. In members where cracking in the tensile cracking in the tensile zone is harmful either because they are 35.3.2 zone is harmful either because they are exposed to the 29. exposed to the effects of the weather or continuously exposed to Cracking – 3rd para effects of the weather or continuously exposed to moisture moisture or in contact soil or ground water, an upper limit of 0.2 or in contact soil or ground water, an upper limit of 0.2 mm mm is suggested for the maximum width of cracks. For is suggested for the maximum width of cracks. For particularly aggressive environment, such as ‘very severe’ and particularly aggressive environment, such as the ‘severe’ ‘extreme’ categories given in Table 3, the assessed surface width category in Table 3, the assessed surface width of cracks of cracks should not in general, exceed 0.1 mm. should not in general, exceed 0.1 mm. 40.5.2 If shear reinforcement is required, the total area of this is If shear reinforcement is required, the total area of this is given Shear Reinforcement 30. given by: by: for Sections Close to As = a b(Ԏ -2dԎ /a )/0.87f ≥0.4 a b/0.87f ΣASV = avb(Ԏv-2dԎc/aV)/0.87fy ≥0.4 avb/0.87fy v v c V y v y supports B-2.1.1 For M50, Tensile stress – 5.2 31. For M50 and above, Tensile stress – 5.2 Direct Tension For M55, Tensile stress – 5.6 In this amendment, The change to the table is a)Substituting the entries 32. Table 21 against M55 b)Insertion of a new row for M60  E-l : In the absence of more exact analysis, the effective E-l : In the absence of more exact analysis, the effective length of length of columns in framed structures may be obtained ANNEX E (Clause columns in framed structures may be obtained from the ratio of from the ratio of effective length to unsupported length lef/l effective length to unsupported length lef/l given in Fig. 26 when 25.2) EFFECTIVE given in Fig. 26 when relative displacement of the ends of 33. relative displacement of the ends of the column is prevented and LENGTH OF the column is prevented and in Fig. 26 when relative lateral in Fig. 27 when relative lateral displacement of the -ends is not COLUMNS displacement of the -ends is not prevented. In the latter prevented. In the latter case, it is recommended that the case, it is recommended that the effective length ratio Ief /l effective length ratio Ief /l may not be taken to be less than 1.2. may not be taken to be less than 1.2.