TRANSPORTING, PLACING, COMPACTION AND CURING OF CONCRETE-AS PER IS-456-2000

 

TRANSPORTING, PLACING, COMPACTION AND CURING OF CONCRETE-AS PER IS-456-2000

*Transporting and Handling

1.     After mixing, concrete shall be transported to the formwork as rapidly as possible by methods which will prevent the segregation or loss of any of the ingredients or ingress of foreign matter or water and maintaining the required workability.

*Placing of Concrete-

1.     The concrete shall he placed and compacted before initial setting of concrete commences and should not be subsequently disturbed.

2.      Methods of placing should be such as to preclude segregation.

3.      Care should be taken to avoid displacement of reinforcement or movement of formwork.

4.      As a general guidance, the maximum permissible free fall of concrete may be taken as 1.5 m.

*Compaction of Concrete-

1.     Concrete should he thoroughly compacted and fully worked around the reinforcement, around embedded fixtures and into corners of the formwork.

2.     Concrete shall be compacted using mechanical vibrators complying with IS 2505, IS 2506. IS 2514 and IS 4656.

3.     Over vibration and under vibration of concrete are harmful and should be avoided. Vibration of very wet mixes should also he avoided.

*Curing of Concrete-

1.     Curing is the process of preventing the loss of moisture from the concrete whilst maintaining a satisfactory temperature regime.

2.     Super sulphated cement concrete is seriously affected by inadequate curing and the surface has to be kept moist for at least seven days.

3.     Moist Curing-Exposed surfaces of concrete shall be kept continuously in a damp of wet condition by ponding or by covering with a layer of sacking, canvas, hessian or similar materials and kept constantly wet for at least seven days from the date of placing concrete in case of ordinary Portland Cement and at least 10 days or may be extended to 14 days where mineral admixtures or blended cements are used.

4.     The period of curing shall not be less than 10 days for concrete exposed to dry and hot weather conditions.







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