Mortar, a mixture of cement and sand, is used for binding bricks, stones and for plastering the walls. When mortal is mixed with gravel and allowed to set, it forms concrete. Concrete is sturdy construction material.
Concrete is poured into moulds that hold it in place until it hardens. After two or three days of setting, the concrete becomes fir. This hardening is due to the formation of crystals. The crystals lock together and make a very hard artificial stone. Concrete can be moulded into desired shapes to make pre-fabricated parts of buildings and electric poles.
Reinforced concrete cement (RCC) is even stronger and long lasting than concrete itself, because in reinforced concrete, steel rods or steel mesh are embedded in wet concrete. Concrete sticks to the steel as it sets. Ceilings of modern multi-storeyed buildings are constructed with reinforced concrete cement. Big bridges and dams are also made up of reinforced concrete cement.