The decrease in the height of freshly prepared concrete after lifting the mould of standard dimension is called slump.
Types of Slump
There are three types of slumps
Up to 125mm
We discard the collapse slump due to the very amount of water present in the concrete mixture.
Up to 150mm
Shear slump occur due to the lack of cohesion in mixture.
The metal mould is placed on a flat non absorb surface with the smaller opening on the top. It is then held vertically in place during filling of concrete by the operator standing on the two foot peer of the mould & filled the mould in three layers. The pouring of the 1st layer in mould is up to the 70mm from the bottom and the 2/3 of volume fills to the depth of 160mm. vibration I must be given on each layer with the help of temping rod. Uniformly distributed over the x-section of each layer. Rod should be on 2nd % 3rd layer throughout its depth. So that stock must penetrate into the under laying layer. Complete the entire test with an elapse time of 2.5 min.
After filing, the concrete is slowly lifted without any lateral and torsion movement, the decrease in the height of concrete is called slump. It is measured to the nearest top surface of concrete. The mix value of slump is equal to 25mm & max 100mm. (not on ASTM)