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Settlement test procedure in normalized concrete

Moisten the mold and place on a rigid, flat, moist and non-absorbent horizontal surface. Fasten the mold firmly with the feet and fill with a sample of concrete in three layers.

Each layer about one third of the mold volume approximately.

Each layer should be compacted with 25 strokes of the rod, distributed evenly over its cross section.

For the bottom layer it is necessary to slightly tilt the rod giving approximately half of the blows near the perimeter and advancing with vertical blows in a spiral towards the center.

The bottom layer should be compacted throughout its thickness; each of the intermediate and upper layers must be compacted throughout their respective thickness, so that the rod penetrates slightly into the immediately lower layer.

When filling the top layer, concrete must be stacked on the mold before compacting.

If in doing so it sits below the top edge, concrete should be added so that in all moment there is an additional amount on the mold.

After compaction, the last layer should be smoothed flush with the surface of the concrete using the compactor rod.

Inmmediately remove the mold, lifting it carefully in a vertical direction.

Lift the mold at a distance of 300 mm for 5 s ± 2 s, by a uniform upward movement without producing lateral or torsional movement to the concrete.

The complete operation, from the moment the mold is filled until it is removed, must be carried out without interruption for a maximum time of 2 min, 30 s.

Immediately the settlement is measured, determining the vertical difference between the upper part of the mold and the displaced center of the upper surface of the sample.

If a pronounced collapse or a detachment of the concrete towards one side of the sample occurs, the test should be rejected and the determination made on another portion of the sample.

If two consecutive tests on a concrete sample show failure or shearing of a concrete portion, it probably lacks the plasticity and cohesion necessary for the settlement test to be applicable.

NTC 396

ALEJANDRA TORRES

CÓDIGO 7304030