ABSTRACT
Concrete structures or structural elements are designed to take up external mechanical loading. In modern design codes based on ultimate limit state design, it is considered that concrete in tension will crack, leaving only the reinforcement to carrying the tensile loading. This does not mean that concrete structural elements under service load will always show cracks. Crack widths will depend on several parameters such as the bond between concrete and steel reinforcement, cover thickness, distance between reinforcing bars, and diameter of the reinforcing bars. In structures which are statically indeterminate, differential settlements can lead to cracking. Based on the expansive ice formation when water is freezing, representing a 9% volume increase, Powers proposed the hydraulic pressure theory to explain internal frost damage. It is important to know that in fine pores the freezing point is reduced because the ice crystals have a high surface-to-volume ratio.
