Objective

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

Equipment Used

  • Slump Cone
  • Tamping Rod
  • Spatula
  • Brush
slump equipment
Image credits: humboldtmfg.com

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 operator is required to hold in a firm position.
  3. Concrete is poured in three layers of almost equal height. All layers are tamped 25 times using tamping rod.
  4. When 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 change in slump.

 

Measurement:

Slump is then measured immediately simply be measuring the difference between original cone height and specimen height.

concrete slump measurement
Image Credits: concrete.org.uk

Slump Characterization:

Slump test does more than only indicating workability. It also shows us other mix 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.

types of slump
Image credits: aboutcivil.org

If collapsed or shear slump is achieved than test is repeated to make sure that results are true. 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 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 cone.

 

9 COMMENTS

  1. highly informative
    especially the fact about high workability mix. some novice don’t know that collapse slump don’t signify poor mix ratio but high water cement ratio.

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