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Reinforced Cement Concrete Lintels
Reinforced cement concrete is the most suitable and commonly used material for lintels. It is resistant to fire, insects, temperature stresses and atmospheric agents. It possesses excellent resistance to tensile stresses with minimum size and is best suited for long spans and heavy loading conditions. They are economical and easy in construction.
RCC lintels have replaced all other materials for lintels. No relieving arches are necessary when RCC lintels are adopted. The usual concrete mix for RCC lintel is 1:2:4 i.e., 1 part of cement, 2 parts of sand and 4 parts of aggregates by volume. Plain concrete lintels can be used up to a span of about 80cm. But some form of reinforcement is necessary in RCC lintels as plain concrete is weak in tension.The amount of reinforcement depends on the span of lintel, width of opening and the total load to be supported by the lintel.
RCC lintels may be pre-cast or cast-in-situ. Pre-cast RCC lintels are convenient for small spans up to 2 meters or so and they are economical as the same mould can be used to prepare a number of lintels. Pre-cast RCC lintels increase the speed of construction and allow sufficient time for curing before fixing. One precaution to be taken in case of pre-cast RCC lintels is that the top of lintel should be properly marked with tar or paint. This will help in placing the lintel correctly. Lintels of bigger size and those which are intended to support sun shades (Lintels on outer walls) should be cast in situ.
For casting lintels in situ, necessary form work is made, reinforcement cage is fixed, and concrete is poured, rammed and cured. The reinforcement generally consists of 3 or more tensile reinforcement bars at bottom, depending upon the load to be supported. When finishing is to be done or where appearance is not of importance, the surface of RCC lintel can be kept exposed. Otherwise, a rebate may be provided in the lintel and the surface can be suitably finished.
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