What Are Differences Between Shear Slump and Collapse Slump in Slump Test?
What Are Differences Between Shear Slump and Collapse Slump in Slump Test?
During slump test when half of the cone slides down in an inclined plane, it is called a shear slump. Shear slump is an indication of the lack of cohesion in the mixture. The slump test must be repeated in order to avoid shear slump.
Shear slump indicates that the concrete is not compacted. It may undergo bleeding and segregation so shear slump is undesirable for the durability of the concrete.
If we get a shear slump, concrete is not acceptable due to lack of cohesion. We have to repeat the slump test and also check the design mix, aggregate size, and shape, water-cement ratio, etc.
During slump test the fall of the mixture indicates that the concrete is too wet due to the high water content of the cement, it is called collapse slump. It causes bleeding and separation. It is therefore not acceptable so we have to reduce the amount of water-cement ratio and repeat the test.
Collapse slump indicates that the concrete mix is very wet and the mixture is considered harsh and lean.
In case of collapse slump, the fresh concrete collapse completely. If the mixture is too wet or high workability mix, slump testing is not suitable for such a mix.