The Abrams cone is a metallic instrument that is used in the test carried out on concrete in its fresh state to measure its consistency ("fluidity" or "plasticity" of fresh concrete).

The test consists of filling a truncated conical metal mold of standardized dimensions, in three tamped layers with 25 strokes of a rod - tamper and, after removing the mold, measuring the settlement experienced by the mass of concrete placed inside.[1]​.

This measurement is complemented by the observation of the collapse shape of the concrete cone "Cone (geometry)" by means of lateral blows with the rod - tamper.

Fill

The amount of concrete necessary to carry out this test will not be less than 8 liters.

The lower layer is filled to approximately 1/3 of the total volume and the middle layer to approximately 2/3 of the total volume of the cone. It is important to emphasize that it should not be filled by height, but by volume.[2]​.

Rammed

When tamping the lower layer, the first blows will be given with the tamper rod slightly inclined around the perimeter. When tamping the middle and upper layer, the blows will be given so that the tamper rod reaches the underlying layer. During the tamping of the last layer, an excess of concrete must be permanently maintained on the upper edge of the mold, since the blows of the normalized rod will produce a decrease in volume due to compaction.

Settlement Measurement

Once the mold is lifted, the decrease in height of the molded concrete (seat) with respect to the mold will initially be approximately 5mm. Essay Archived April 22, 2021 at the Wayback Machine. The measurement is made on the central axis of the mold in its original position. Depending on the total seat, it is possible to determine the fluidity. The Spanish concrete regulations (Structural Code) include different consistencies depending on said settlement, which must be taken into account when concreting different construction systems. This regulation qualitatively includes the following consistencies depending on the seat of the cone (in cm), with a tolerance of +/- 1 cm with respect to the following values:.

-From 0 to 2 cm, dry consistency.

-From 3 to 4 cm, plastic consistency.

-From 5 to 9 cm, soft consistency.

-From 10 to 15 cm, fluid consistency.

-From 16 to 21 cm, liquid consistency.

According to the aforementioned regulations, and except in specific applications that are required, the application of dry and plastic consistency should be avoided, as well as liquid consistency, unless it is achieved through superplasticizing additives.