Concrete Slump Test: What it Is and How to Do it

A concrete slump test is a standard procedure used to measure the consistency and workability of freshly mixed concrete. This test provides a real-time indication of the water content and consistency of the concrete mix to ensure that builders can properly handle, place, and finish the concrete.

Performing a Concrete Slump Test

For a concrete slump test, a conical-shaped metal mold is filled with newly mixed concrete in three layers. Once someone has filled the cone, they remove it carefully and observe the resulting conical-shaped concrete form. Construction professionals can make assessments regarding the quality of the concrete according to its performance when they remove the cone. This information will help them to assess their mixture of concrete and make any needed adjustments to ensure the success of their project.

Performing a Concrete Slump Test

The following are the steps for carrying out a standard concrete slump test.

  1. Prepare the Equipment – Gather the necessary equipment for the on-site test including a metal slump cone, a tamping rod that is 2 feet with a ⅝ inch end, measuring tape, and a smooth flat surface to perform the test.
  2. Clean the Slump Cone – Ensure that the slump cone is clean from debris or any residual concrete from other tests as these can impact the result of the test.
  3. Moisten the Slump Cone – Lightly moisten the inside surface of the metal slump cone so that the concrete does not adhere to the sides.
  4. Position the Slump Cone – Position the slump cone on a stable, clean, and flat surface. The wider end should face downwards.
  5. Fill the Slump Cone – Fill the concrete with concrete in three roughly equal layers. Each layer should be compacted using the tampening rod. Carefully tamp with at least 25 strokes for each layer, making sure to distribute the pressure evenly throughout the layer.
  6. Strike Off the Top – After you have filled and compacted each of the three layers of concrete in the cone, take off the excess concrete coming out of the top of the cone using a trowel or straightedge.
  7. Lift the Slump Cone – Carefully lift the slump cone vertically off the concrete form in a smooth and steady motion without any lateral or twisting movements.
  8. Measure the Slump – Once you remove the cone, you can measure the difference between the top of the slump cone and the highest point of the concrete slump.
  9. Record the Slump – Note the measured slump value in inches or millimeters. This value will help indicate the concrete slump type: true slump, shear slump, or collapse slump. This measurement will help you to make decisions about the workability of the mix and its stability for your project. It will also indicate if you need to make any changes in the concrete mixture to provide the most optimal material for your project.
  10. Clean Your Equipment – Clean all your equipment including the cone and tamping rod to ensure that they are ready for your next test.