Slump test for concrete – procedure of slump test

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Objective

The slump test is used to measure the consistency of the concrete mix. Indirectly it is used to check whether the workability of the concrete mix is up to the desired level or not.

Equipment Used

  • Slump Cone
  • Tamping Rod
  • Spatula
  • Brush

Procedure

  1. Cone is cleaned using a brush or maybe some water. It should nor wet or neither completely dry otherwise;, it will alter mix water content.
  2. The cone is placed on a rigid surface, and an operator is required to hold in a firm position.
  3. Concrete is poured into three layers of almost equal height. All layers are tamped 25 times using a tamping rod.
  4. When the cone is full, excessive concrete is struck off using a spatula.
  5. Cone is then lifted in vertical position gently. Care should be taken in lifting as tilting can cause changes in slump.

Measurement:

Slump is then measured immediately merely by measuring the difference between original cone height and specimen height.

Slump Characterization:

The slump test does more than only indicating workability. It also shows us other mixed properties such as segregation resistance, cohesiveness.

Slump can take different shapes, and depending on shapes, slump can be true slump, shear slump, or collapsed slump.

If a collapsed or shear slump is achieved, then the test is repeated to make sure that results are accurate. The collapsed slump means that mix is too wet, or it is high workability mix as in case of self-compacting concrete. In such cases, this test is of no use, and we have to resort to other tests such as flow test, V-funnel test, or J-ring test, which are designed for high workability mix.

Precautions

  • Equipment should be cleaned so that it does not alter test results.
  • Slump cone should be lifted with care in vertical direction. There should be no movement in the horizontal direction.
  • Measurement should be done immediately after removing the cone.

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