Technical Questions

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What correction should be made for absorbed water and surface water carried by the aggregates?

Q. What correction should be made for absorbed water and surface water carried by the aggregates?

 

A. With batch quantities determined by mass on saturated surface-dry aggregates, it is necessary to find the quantities of aggregate as delivered that will give the equivalent saturated surface-dry (SSD) materials. If the aggregates are drier than SSD, additional water needs to be added to the batch to fill the permeable pores in the aggregate. If they are wetter than SSD, the surface water is counted as part of the mixing water and reduced from the amount of water added to the batch. These corrections are essential to keep the w/cm constant. Changes in w/cm affect the properties of concrete.

 

References: SP-1(02); ACI 211.1-91; ACI 211.4R-08

Topics in Concrete: Aggregate; Concrete Fundamentals; Mixture Proportioning

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