Does the method of molding test specimens affect the test results?

Q. Does the method of molding test specimens affect the test results?

A. Yes. Unless specimens are carefully molded, erratic test results will be obtained. The concrete should be placed in the mold in layers; then, each layer should be rodded or vibrated if the slump is 25 mm (1 in.) or greater, and vibrated if the slump is less than 25 mm (1 in.). The mold should be held firmly in a vertical position during filling and stood on a base plate that is a true horizontal plane. Leakage of water from the molded concrete should be avoided. See ASTM C31 and ASTM C192 for guidance on making and curing test specimens in the field and in the laboratory, respectively.

References: SP-1(02); ASTM C31; ASTM C192

Topics in Concrete: Testing of Concrete