Concrete Slump Cone Test: Procedure, Apparatus, & Slump Cone Size

The slump cone test is a standard field method used to assess the workability of fresh concrete before placement. Construction teams use this test because it's fast and tells you right away if your concrete mix is good to go.

What is a Slump Cone?

A slump cone is a metal cone that's open on both ends. You fill it with concrete to test how the mix behaves. As per IS: 1199 (Part 2) : 2018 the slump cone is 300 mm in height, with a top diameter of 100 mm and a bottom diameter of 200 mm.

What is the Purpose of the Slump Test?

The slump test measures workability of the concrete.

Workability means how well you can mix, move, place, and finish the concrete without it falling apart. If concrete has too much water, it gets weak. If it's too dry, you can't place it properly and end up with gaps or holes in your structure.

The slump cone test lets you check if your water-cement ratio is right while you're still on the job site.

The Slump Cone Apparatus

The primary piece of equipment is the slump cone itself. It's a cone-shaped mould, open at both ends.

The standard slump cone size as per Indian Standards (IS: 1199) (Part 2) : 2018 is:

• Top Diameter: 10 cm

• Bottom Diameter: 20 cm

• Height: 30 cm

The complete slump cone apparatus also includes a tamping rod (a 16 mm diameter steel rod) and a non-absorbent base plate.

Slump Cone Test Procedure

The slump cone test procedure is straightforward:

1. Place the slump cone mould on a clean, level, and non-absorbent surface.

2. Dampen the mould & base plate with a moist cloth and wipe any excessive water from the surface using absorbent cloth

3. Fill the cone (mould) with fresh concrete in four (three) equal layers.

4. Tamp each layer 25 times with the 16 mm dia tamping rod, distributing the strokes evenly over the cross-section.

5. Tamp the second layer and top layer each throughout its depth, so that the strokes just penetrate in to the underlying layer.

6. In filling and tamping the top layer, heap the concrete above the mould before the tamping is started.

7. After the top layer is tamped, strike off the excess concrete to make the surface level with the top of the cone.

8. Carefully lift the cone vertically upwards, allowing the concrete to subside or 'slump. '

9. Measure the difference in height between the top of the slumped concrete and the original height of the cone. This difference, in millimetres, is the slump value.

10. The Slump is measured to the nearest 5 mm.

11. There are three types of Slump.

a. True Slump

b. Shear Slump

c. Collapse Slump

What is the Slump Range?

The acceptable slump value depends on the type of construction.

• What is the slump cone test value for slab?

Slabs and beams typically work well with 50-100 mm slump. But if you have lots of rebar or are doing foundation work, you might need 75-125 mm so the concrete flows around all the steel bars.

• What is a good slump for slab?

Most concrete slabs work best with 50-100 mm slump. This gives you concrete that's easy to place and finish but isn't so wet that it loses strength or separates.

• What should be the slump value for pumped concrete ?

The Degree of workability should be high for pumped concrete and slump value should be preferable above 150 mm.

The slump cone test is a vital quality control measure. It ensures the concrete you use has the correct consistency for a strong and durable structure. In the “very high” category of workability, measurement of workability by determination of flow will be appropriate.