Lean concrete is a mix where the amount of cement is lower than the amount of liquid present in the strata.
The higher the Aggregate/cement ratio, the leaner the concrete. In lean concrete, less quantity of paste is available for providing lubrication, per unit surface of aggregate and hence the mobility of aggregate is restricted.
Lean Concrete is ‘not Rich’, in other words the ratio of cement to water and of course to aggregate would be low.
Main Purpose of Lean Concrete
Main function of the lean concrete is to provide the uniform surface to the foundation concrete and to prevent the direct contact of foundation concrete from the soil.
Lean concrete is used under the foundations.
It is good for providing a flat bottom in uneven or dirt terrain.
Lean concrete has a lower level of cement in it, which is why it’s mostly used for fillings or under the foundations, to keep it protected from the soil.
Lean concrete is used to provide a level surface, where main foundation (raft, isolated or any other type) can be placed.
Another purpose is protection of main foundation from soil below, as moisture or other chemicals in soil like sulphates may attack concrete and can weaken it.