Technical Questions

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Requirements for storing and handling aggregate

Q. What are the important requirements in storing and handling aggregate to obtain uniformity in the concrete from batch to batch?

 

A. Faulty or excessive handling and improper storage of processed aggregate may result in one or all three principal problems that may affect the properties of concrete mixtures. The first is segregation, which destroys the grading uniformity. The second is contamination, or inadvertent inclusion of deleterious material. A third problem is the maintenance of uniform and stable moisture content in the aggregates as batched (ACI 304R, ACI 221R). A practical method of reducing segregation to a minimum in coarse aggregate is to separate the material into several size fractions and batch these fractions separately. As the range of sizes in each fraction is decreased and the number of size separations is increased, segregation is further reduced. Coarse aggregate is produced in a number of nominal maximum sizes as outlined in ASTM C33. Fine aggregate is also covered in ASTM C33. Fine aggregate is generally damp, and therefore rarely segregates in handling and batching.

 

References: SP-1(02); E-1(16); ACI 221R-96; ACI 213R-14; ACI 304R-00; ASTM C33

Topics in Concrete: Aggregate; Concrete Fundamentals; Materials; Placing

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