After checking the delivered Concrete Mix Design against Approved Drawings and Specifications. A concrete slump test is conducted and is an empirical test that measures workability of fresh concrete. The test measures consistency of concrete in that specific batch. It is performed to check consistency of freshly made concrete. Consistency refers to the ease with the test conducted and is popular due to the simplicity of apparatus used and simple procedure.
The test is carried out using a metal mold in the shape of a conical frustum known as a slump cone or Abrams cone. The Cone is open at both ends and has attached handles. The cone is placed on a dampened hard non-absorbent surface. This cone is filled with fresh concrete in three stages. Each time, each layer is tamped 25 times with long bull-nosed metal rod measuring 5/8” in diameter.
At the end of the third stage, the concrete is struck off flush with the top of the mold. The mold is carefully lifted vertically upwards, so as not to disturb the concrete cone.
The concrete then slumps (subsides). The slump of the concrete is measured by measuring the distance from the top of the slumped concrete to the level of the top of the slump cone.
The measurement is know and the “Slump” of the Concrete, each concrete mix design will have a slump identified number in Inches and this measurement must be Plus or Minus 1” (including tolerances) to comply to ASTM C143.
At the discretion of the concrete contractor, Water may be added at the Job-site to the concrete depending upon the Slump Measured and Allowable indicated on the delivery ticket.