24 hours should elapse bctwecn the completion of

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Unformatted text preview: ickilcss except to expedite the placing of embcddcd materials. The intcl-vx!’ 19 IS:457-1957 between two lifts shall also be maintained as constant as possible, and the difference of elevation between any two adjacent blocks shall not be more than 900 cm ( or 30 ft ) and not less than 150 cm ( or 5 rr 1. A period of 5 days for 150 cm ( or 5 ft ) of concrete laid shall be allowed before the next pour unless heat dissipation methods warrant otherwisti. 4.10.8 Placing ‘Plums ’ in be used, they shall be washed before being embedded in the 30 cm ( or 12 in ) to an exposed an adjacent stone. The stones stone shall be laid and carefully forms or adjacent masonry and ness of unnecessary seams occur Concrete - Where plums are permitted to and all dripping surface water removed concrete. No stone shall be closer than surface nor nearer than 15 cm ( or 6 in ) to shall not be dropped in place, but each embedded so as.to avoid any injury to the in such a manner that no planes of weakin the structure. 4.10.9 Satye Blocks-In placing concrete in large blocks, the work shall in general proceed from the low side to the high side so that the working face is never excessively steep nor long. However, for construction joints in dams, the work shall proceed from the high side to the low side so as to maintain an upward slope in the downstream direction, unless construction joints are otherwise shown on the drawings. Under no condition shall the slope be so steep as to cause the concrete to flow without The concrete shall be deposited as working, or to cause any segregation. nearly ‘as practicable in final position and shall not be piled up in large masses at any point and then pushed, shovelled, or vibrated into space for kJtlg distances. It shall be brought up evenly around all large openings, conduits, or embedded metal so as to minimize unequal pressure and avoid dispiacement. For large blocks of concrete in dams and other massive structures, the sequence and rate of casting successive lifts and adjacent blocks shall be such as to faciiitate the dissipation of the heat of hydration. 4.10.10 Iirjcctd Coxcyete - A!1 concrete of rejected and removed from ti.c Gt.t: of operations, fresh concrctt:; where concrete has rllready been it shall be dug out and removed from the forms. proper placement or in a such condition that it pacted, shall be removed. 4.11 inferior quality shall be if possible, before placing placed, if found inferior, Any batch, too stiff for cannot be properly com- Compacting 4.11.1 .~fethnrl - Concrete shall 1~. thoroughly compacted by means of suitable tools during and imrncrliately after depositing. The concrete sIrall 1,~ worked around a11 I-cinforctrment, embedded fixtures, and into the* corI?c’rs of the forms. Every precaution shall’be taken to keep the reinforcctmetlt and embedded metal in proper position and to prevent distortion. IS : 457 - 1957 4.11.1.1 Compacting shall include rodding, spading, tamping, vibrating, treading, and such other operation...
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This document was uploaded on 10/01/2013.

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