Rebar Locator Test

IS: 456-2000

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Rebar Locator Test

IS: 456-2000

FOREWORD ThisIndianStandard (Fourth Revision) wasadopted bytheBureau ofIndian Standards, afterthedraftfinalized . by theCementandConcrete SectionalCommittee hadbeenapproved by theCivilEngineering Division Council. This standardwas firstpublished in 1953 underthe title 'Codeof practice forplainandreinforced concrete for general buildingconstruction' and subsequently revised in 1957. The code was further revised in 1964 and published undermodified title 'Code of practice forplainandreinforced concrete',thusenlarging the scopeof useof thiscodeto structures otherthangeneral building construction also. Thethirdrevision was published in 1978, and it includedlimit state approach to design. This is the fourth revision of the standard. Thisrevision wastakenup witha viewto keeping abreast withtherapiddevelopment in thefieldof concrete technology and to bringin furthermodifications/improvements in thelightofexperience gained whileusingtheearlierversion of the standard. Thisrevision incorporates a number of important changes. Themajorthrustin the revision is on the following lines:
a) In recent years. durability of concrete structures have become the cause of concern to all concrete technologists. This has ledto the needto codify thedurability requirements worldover. In thisrevision of the code. in orderto introduce in-built protection from factors affecting a structure, earlierclauseon durability has been elaborated and a detailed clause covering different aspects of design of durable structure has been incorporated.
b) Sampling and acceptance criteriafor concrete havebeenrevised. With thisrevision acceptance criteria has been simplified in line with the provisions given in BS 5328 (P8l1 4):1990 'Concrete: Part 4 Specification for the procedures to be usedin sampling, testing and assessing compliance of concrete'.
Someof the significant changes incorporated in Section 2 are asfollows: a) All the threegradesof ordinary Portland cement, namely 33 grade, 43 gradeand 53 gradeand sulphate resisting Portland cement have been included in the list of types of cementused (in addition to other types of cement).
b) Thepermissible limits forsolids inwaterhavebeen modified keeping inviewthedurability requirements.
c) The clause on admixtures has been modified in view of the availability of new types of admixtures including superplasticizers.
d) In Table2 'Grades of Concrete', grades higherthanM 40 havebeen included.
e) It has been recommended that minimum grade of concrete shall be not less than M 20 in reinforced concrete work (see also6.1.3).
f) The formula for estimation of modulus of elasticity of concrete has beenrevised.
g) In the absence of proper correlation between compacting factor, vee-bee time and slump,workability has now been specified only in termsofslump in line withthe provisions in BS 5328(Parts 1 to 4).
h) Durability clausehasbeenenlarged toinclude detailed guidance concerning thefactors 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, depthofconcrete cover, concrete quality, requirement against exposure toaggressive chemical andsulphate attack,minimum cementrequirement andmaximum watercementratio,limitsof chloride content. alkali silica reaction, and importance of compaction, finishing andcuring.
j) Aclauseon-'Quality Assurance Measures' hasbeen incorporated to givedue emphasis to goodpractices of concreting.
k) Properlimitshavebeenintroduced ontheaccuracy of measuring equipmentstoensureaccurate batching of concrete.

1 SCOPE

1.1 This standard deals with the generalstructuraluse of plain and reinforced concrete.
1.1.1 For the purpose of this standard, plain concrete structures are those where reinforcement,if provided is ignoredfordetermination of strengthof thestructure.
1.2 Special requirementsof structures,such as shells, folded plates,arches.bridges,chimneys,blastresistant structures, hydraulic structures, liquid retaining structuresand earthquakeresistantstructures,covered in respective standards have not been covered in this standard; these standards shall be used in.conjunction with this standard

2 REFERENCES

The Indian Standards listed in Annex A contain provisions which through reference in this text, constitute provisions of thil standard. At the time of publication, the edition. indicated were valid. All standards are subject to revision and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated in AnnexA.

3 TERMINOLOGY

For the purpose of this standard, the definitions Biven in IS 4845 and IS 6461 (Parts 1 to 12) shall generally apply

5 MATERIALS

s.t Cement The cement used shall he any of the following and the type selected should be appropriate for the intended use:
a) 33 Grade ordinary Portland cement conforming to IS 269
b) 43 Grade ordinary Portland cement conforming to IS 8112
c) S3 Grade ordinary Portland cement conforming to IS 12269
d) Rapid hardening Portlandcement conforming to IS 8041
e) Portland slag cement conforming to IS 4;5
f) Portland pozzolana cement (fly ash based) conforming to IS 1489 (Part 1)
g) Portland pozzolana cement (calcined clay based) conforming to IS 1489 (Part 2)
h) Hydrophobic cement conforming to IS 8043
j) Low heat Portland cement conforming to IS 12600
k) Sulphate resisting Portland cement conforming to IS 12330 Other combinations of Portland cement with mineral admixtures (see $.2) of quality conforming with relevant Indian Standards laid down may also be used in the manufacture of concrete provided that there are satisfactory dati on their suitability, such as performance test concrete containing them.
5.1.1 Low heat Portland cement conforming to IS 12600 shall be usedwith adequateprecautionswith regard to removal of formwork, etc.
5.1.Z Hiah alumina cement conforming to IS 6452 or supersulphated cement conforming to IS 6909may be used only under special circumstances with the prior approval of the engineer-in-charge. Specialistliterature Inay be consuIted for guidance regarding the use of these types of cements.
5.1.3 The attention of the engineers-in-charge and users of cement is drawn to the fact that quality of various cements mentioned in 5.1 is to be determined on the basis of its conformity to the performance characteristics given in the respective Indian Standard Specification forthatcement. Any trade-mark or any trade nameindicating any special features not covered in. the standard or any qualification or other special performance characteristics sometimes claimedl indicatedon the bass or containersor in advertisements alongside the 'Statutory QualityMarking' or otherwise

6 CONCRETE

6.1 Grades The concrete shall be in grades designated as per Tanlc 2
6.1.1 The characteristic strength is defined as the strength of material below which not more than 5 percent of the test results arc expected to fall.
6.1.2 Tile minimum grade of concrete for plain and reinforced concrete shall be as per Table 5.
6.1.3 Concrete of grades lower than those given in Table 5 may he used for plain concrete constructions. lean concrete, SImple foundations, foundation for masonry walls and other simple or tcmporury reinforced concrete construction.
6.2 Properties of Concrete 6.2.1 IIIClI'(/.I'(, ofStrength with Agi'
There is normally a gain of strength beyond 2S days. The quantum of increase depends upon the )!radc and type of cement, curing and cnvuoruucnral conditions, etc. The design should 1)(' h:1S,xl on 2x dav-, charactcristic strength "fcom.r. " 'lIlkss there is a evidence III justifya higherstrength fora particularstructure dueto age.
6.2.1.1 For concrete of grade M 30 and above. the rateofincrease of compressive strength withageshall be basedon actualinvestigations. 6.2.1.2 Where members are subjected to lowerdirect loadduringconstruction, they should be checkedfor stresses resulting from combination of directloadand bending duringconstruction.
6.2.2 Tensile Strength of Concrete
The flexural and splitting tensile strengthsshall be obtained as described in IS 516 and IS 5816 respectively. When the designer wishes to use an estimateof the tensilestrength fromthe compressive strength, the following formula may be used:

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