What is Concrete

In general, it is a poor conductor of heat and has good fire-retardant properties. The actual degree of fire resistance of this material depends on the nature of the aggregates used and its density. In the case of RCC and prestressed construction, it also depends on the position of the steel in the concrete. It has been found that ordinary concrete, when exposed to fire, dehydrates and results in shrinkage cracks. (This is because heating aggregates in concrete expands while cement shrinks, and these two opposing processes lead to crack development.) Coarse aggregates such as foamed slag, blast furnace slag, crushed brick, crushed lime Stone and concrete are best suited for concrete. From the point of view of fire resistance. Aggregates such as flint, gravel and granite possess poor fire resistance properties. It has been observed that on an average the surface of the concrete in case of fire disintegrates to a depth of about 25 cm as the mortar in the concrete is dehydrated by the fire. Therefore, in the case of reinforced concrete fire-resistant construction, a cover of sufficient thickness must be provided (generally cracks are created by the reinforcement). RCC structures are considered better than steel frame structures because less steel is used and they are also well protected by mass concrete.