Preparation of Surface before Placing Concrete:

It is very essential to prepare a proper base or place before placing the concrete mix in order to develop proper bond between the base and fresh concrete. Before placing concrete, the different types of bases should be prepared as below.

In the Case of Hardened Concrete Base

The coarse aggregates should be exposed by making the base rough. It is made rough by striking sand under high pressure (i.e. hand blasting). After this the surface should be washed with water under pressure in order to remove the dust particles from it. After a surface is cleaned, the thin coat of cement paste is applied before placing concrete over the hard surface.

In the Case of Specially Prepared Sub-bases

In case of brick soling and water bound macadam; base should be made rough with the help of steel brush. Dust and loose particles should be removed from the sub-base before placing the concrete over it. Before placing concrete the water should be sprinkled over the surface.

In the Case of Natural Soil

Before placing some layer of concrete over natural soil, the soil should be compacted uniformly and its moisture deficiency should be removed initially in order to prevent it from absorbing moisture from beneath the concrete layer.

In the Case of Rocky Base

In the case of rocky base the sides should be cut in vertical direction and not in sloping direction. All the loose particles shall be erased off the rocky base. Before placing concrete the water should be sprinkled over the surface.