Effect of hot weather conditions on the microcracking and corrosion cracking potential of reinforced concrete

This study focuses on the damaging implications of the daily temperature fluctuations in the a~~ressive climatic conditions of hot-arid regions due to strain incompatibility resulting from the widely differing coefficients of thermal expansion of the local crushed limestone aggregate and the hardened cement paste. The data developed strongly indicates that temperature fluctuations cause microcracking in concrete which would increase its permeability and lower its tensile strength and cracking time to a noticeable degree. In this investigation, concrete specimens of water-cement ratios 0.40, 0.50, and 0.65 with a cement content of 550 lb/yd³ (330 kg/m³) were subjected to cyclic heating in programmed ovens which earned out 120 temperature fluctuations, each simulating the temperature regime of a typical summer day in Eastern Saudi Arabia. The thermal regime was characterized by a temperature swing from 27 °C to 60 °C withm a 24 hr period. This included the effect of concrete surface heating by direct solar radiation. Pulse velocity, permeability, and time-to-cracking data were developed in reference and cyclic heat-treated specimens at 20, 40, 60, 80, and 120 heatin~ cycles. It was observed that the cyclic heat treated specimens had a Si~nificantly reduced pulse velocity, a noticeably increased permeability, and, depending on water-cement ratio, a 55 to 70 percent reduction in cracking time due to reinforcing bar corrosion. It is inferred from this data that a significant degree of microcracking is induced in concrete due to the thermal incompatibility of concrete components.Microcracking of concrete increased with the number of heating cycles and there was a systematic improvement in the performance of concrete with a reduction in w-e ratio.