01 Jun, 2023

Concrete slump testing is an incredibly important quality control check, especially when working on a large project with several loads of concrete.

The purpose of concrete slump testing is to ensure that multiple batches of concrete being used on the same project have a consistent mix and are suitable for the intended use or concrete application.

What Is a Concrete Slump Test?

BS EN 12350-2 specifies a method for determining the consistence of fresh concrete by the slump test.

To carry out the test the fresh concrete is compacted into a cone. When the cone is withdrawn upwards, the distance the concrete has slumped provides a measure of the consistence of the concrete.

The slump test is sensitive to changes in the consistence of concrete, which correspond to slumps between 10mm and 210mm. Beyond these extremes the measurement of slump can be unsuitable and other methods of determining the consistence should be considered.

Concrete Slump Test: Step-by-Step Process

The sample of concrete shall be obtained in accordance with BS EN 12350-1.

  1. Slump cone and base plate, clean and damp - placed on solid level base, free from vibration.
  2. Use foot plates to stabilize cone.
  3. Fill in three equal depth layers (after compaction).
  4. Rod each layer exactly 25 times. Rod must be of circular cross-section, straight, made of steel, having a diameter of 16 ± 1mm and length of 600 ± 5mm, with rounded ends.
  5. Sawing and rolling motion of rod to strike concrete level with top of cone.
  6. Clean spillage from cone & base plate.
  7. Cone lifted straight up and clear taking 2 to 5 seconds.
  8. Upturned cone placed close to concrete without disturbing sample.
  9. Lay the rod across the upturned cone. Measure the distance between the underside of the rod and the highest point and measure to the nearest 10mm.
  10. Record result, type of slump etc.

How To Interpret The Results

Following the concrete slump test, the sample will take on one of two forms:

  1. True: Concrete subsides – more or less retaining the same form/shape.
  2. Shear: Top shears off and slips sideways.

The test is only valid if it yields a true slump.

If the specimen shears, the test is not valid, and another sample shall be taken, and the procedure repeated.

If two consecutive tests show a portion of the concrete shearing off from the mass of the test specimen, the concrete lacks the necessary plasticity and cohesiveness for the slump test to be suitable.

What Does a Concrete Slump Test Tell You?

The slump test can tell you two things.

  1. It indicates if the water content of the concrete is consistent between batches. So long as the materials and the grading of the aggregates are reasonably uniform, the test will reveal any variation of the water content from batch to batch.
  2. It can check on the constituents in the concrete. If the amount of water used and the moisture content of the aggregate are constant, the test will show whether the grading of the aggregate has changed.

On-Site Concrete Testing Services In The South of England

ACS Testing offer a comprehensive range of professional on-site testing services, all carried out by our fully trained site technicians. We provide our clients with a UKAS Accredited sampling of materials, including concrete slump testing.

We provide our on-site testing and sampling service across the whole of the South of England. Our team of experts are ready and waiting to discuss our range of concrete testing services for any new project, simply get in touch with us to find out more.