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What consideration should be given to water that may be lost from concrete between the time it leaves the mixer and its final consolidation in the form?

Q. In calculating the water-cementitious material ratio, what consideration should be given to water that may be lost or deliberately extracted from concrete between the time it leaves the mixer and its final consolidation in the form?

 

A. Full consideration can be given to such reduction in water content as long as the concrete is finally consolidated and finished as a plastic mass and the space formerly occupied by the lost water is closed. It is the ratio of the w/cm in the paste after consolidation is complete and when setting begins that determines the potential properties of the hardened concrete. The extraction of water by absorptive form liners and by vacuum suction are practical illustrations of this principle, but they are often not used.

 

References: SP-1(02)

Topics in Concrete: Concrete Fundamentals; Formwork; Mixture Proportioning; Placing