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Why is the slump test not an absolute measure of consistency or workability?

Q. Why is the slump test not an absolute measure of consistency or workability?

 

A. It does not distinguish between mixtures of different character. For example, a harsh coarse mixture and one with a large proportion of fine aggregate having the same slump cannot be said to have the same consistency. This is even more true in the case of workability. With air-entrained concrete, however, with its inherently greater plasticity and cohesiveness, the slump is a better measure of both consistency and workability.

 

References: SP-1(02); ACI 238.1R-08; ASTM C143

Topics in Concrete: Concrete Fundamentals; Testing of Concrete