MEASURING CONCRETE WORKABILITY

Updated: Oct 27, 2020

It´s easy! Just grab the cone, fill it with concrete and lift it up....hurry up we have more important things to do! Just another ordinary day at the building site during a casting.



We have already discussed about the importance of the correct workability of concrete (see post “Workability of concrete”), but how to measure it? The most famous way is the Abrams cone test or slump test. Easy? Well, my first boss used to say: “There are no easy or difficult things, only things you know how or things you don´t know how to do”. So let´s start from what you need:

A full Abrams cone is made of a cone (really?!) a plate, a pestle, a meter preferably a funnel and a bailer.



10 steps procedure:


1. Wash the equipment so to have it slippery.

2. Place the plate onto a horizontal flat clean surface at the operator´s feet level.

3. Place the cone onto the plate. The cone comes with two feet where the operator must step onto.

4. Start filling the cone while keeping it in place with the feet, it must be filled up with three similar layers.

5. Compact each layer of concrete with the pestle hitting 25 times with circular patterns carefully avoiding to compact the lower layer again.

6. Ensure the cone is totally filled up right to its limit, not more, not less.

7. While keeping the cone with the feet so as to keep it well fixed on the plate, grab the cone´s handles and push the cone as to keep everything right in place.

8. Remove your feet (the cone is still “fixed” on the plate) and gently lift up the cone straight without vibrations in 5 to 10 seconds.

9. Place the cone beside the dropped mass of concrete and by the help of the pestle and the meter measure the highest point (tolerance ± 1 cm.).

10. Wash carefully all the equipment.


10 common mistakes:


1. Not washing the equipment before using. The internal surface in contact with the concrete will be too dry compromising the concrete´s rheology and invalidating the test.

2. Choosing a dirty, rough, uneven surface where to set the plate. This will allow movements that will nullify the test.

3. Not pushing enough with your feet onto the cone´s feet. Concrete will come out from below nullify the test.

4. Filling the cone in more or lesser than three layer. Irregular method, the test is not valid.

5. Not compacting the layers in the way over described. Irregular method, the test is not valid.