WORKABILITY OF CONCRETE - AS PER IS-456-2000

WORKABILITY OF CONCRETE - AS PER IS-456-2000

The concrete mix proportions chosen should be such that the concrete is of adequate workability for the placing conditions of the concrete and can properly be compacted with the means available.

Placing Conditions	Degree of Workability	Slump(mm)
Blinding concrete; Shallow sections & Pavements using pavers	Very low	In the ‘very low’ category of workability where strict control is necessary, for example pavement quality concrete, measurement of workability by determination of compacting factor will be more appropriate than slump (see IS 1199) and a value of compacting factor of 0.75 to 0.80 is suggested.
Mass concrete, Lightly reinforced sections in slabs, beams, walls, columns, Floors; Hand placed pavements; Canal lining; Strip footings	Low	25-75
Heavily reinforced sections in slabs, beams, walls, columns; Slipform work; Pumped concrete	Medium	50-100 75-100
Trench fill; In-situ piling	High	100-150
Tremie concrete	Very high	In the ‘very high’ category of workability, measurement of workability by determination of flow will be appropriate (see IS 9103).

 

NOTE-

*For most of the placing conditions, internal vibrators (needle vibrators) are suitable. The diameter of the needle shall be determined based on the density and spacing of reinforcement bars and thickness of sections.

*For tremie concrete, vibrators am not required to be used.

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

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