TESTING AND PROCEDURES
The mold should be dampened and placed on a flat, moist, nonabsorbent, firm surface. Fill the mold immediately
with three equal layers of a concrete specimen. As you fill the mold, rotate each scoopful of the concrete around
the top edge of the mold as the concrete slides from it. This ensures a symmetrical concrete distribution within
the mold. Tamp each layer 25 strokes with the tamping rod, distributing the strokes uniformly over the cross
section of the mold and penetrating the underlaying layer. Tamp the bottom layer throughout its depth. After
tamping the top layer, strike off the surface with a trowel so that the concrete fills the mold exactly. Without
delay, carefully lift the mold straight up from the concrete and place it beside the specimen.
The tamping rod should be placed across the top of the mold. Measure the distance between the bottom of the rod
and the displaced original center of the top surface of the specimen. If a decided falling away or shearing off of
concrete from one side or portion of the mass occurs, disregard the test and make a new test on another portion of
NOTE: If two consecutive tests on a sample of concrete show a falling away or shearing off of a portion of the
concrete from the mass of the specimen, the concrete probably lacks necessary plasticity and cohesiveness for the
slump test to be applicable.
Supplementary Test Procedure
After completing the slump measurement, tap the side of the specimen gently with the tamping rod. How the
concrete mix behaves under this treatment is a valuable indication of its cohesiveness, workability, and
placability. A well-proportioned workable mix will gradually slump (fall or flatten out) but still retain its original
consistency, whereas a poor mix will crumble, segregate, and fall apart.