Cement is a composite material, which is mainly made up of : [ water, aggregate and cement ]. However, reinforced concrete is usually used for the construction of building elements. Reinforced concrete is a composite material, in which the inclusion of a reinforcement such as steel bars which have higher tensile strength, to counteract the concrete's lower tensile strength. However, over the long period of time, the steel reinforcements would begin to rust, and through expansion and flaking, this causes the concrete to crack, destroying the bond between the concrete and the steel bars. Furthermore, the cracks contributes towards the exposure of its material to the surroundings, causing moisture to enter, and lead to further rusting and decay. Over time, the concrete is taken down layer by layer through exposure.