Why is Plain Cement Concrete (PCC) laid before any Reinforced Cement Concrete?

Plain Cement Concrete of M15 grade (thickness of 100mm) are mandatorily  placed on a ground/soil strata, to give a firm,clean base for placing reinforcement cage,as we start building  foundation of a RCC structure.

It is also help in following ways:

1.Required cover to bottom reinforcement is ensured ,as cover blocks rest on a firm PCC .

2.The effective depth of RCC members is achieved as the formworks can be easily,uniformly and sturdily fixed ,resulting in better dimension accuracy of foundation RCC member.

3.Reinforcement steel placed on a PCC, are never in touch with ground soil ,which may be chemically active may lead steel corrossion in immediate future (when in contact with ground soil )

4.Ease placement of steel cage and increase productivity.

5. Concrete don’t bond with ground soil (clay),PCC acts a barrier to soil and bond well to overlayed structural grade concrete.

Note : Ensure good curing of PCC too.