Experimental and Analytical Investigation of Crack Spacing and Width for Overlaid RC Beams at Elevated Temperatures

Cracking in overlay-strengthened RC structures significantly influences their structural performance; however, the effect of elevated temperatures on cracking behavior remains unclear. This work summarizes the experimental and analytical investigations of flexural crack spacing and crack widths of overlaid reinforced concrete (RC) beams at elevated temperatures. Flexural crack spacing was observed experimentally by conducting four-point bending tests on control RC beams and beams overlaid by polymer cement mortar (PCM) together with steel reinforcements at 20, 40, and 60 degrees C during both exposure and loading. The flexural crack width was measured during testing at 20 and 40 degrees C. The flexural crack spacing and crack width increased with increasing temperature for the same reinforcement ratio in the overlay, whereas the flexural crack spacing and crack width decreased with increasing total area of steel reinforcements in the overlay at the same temperature. Based on the existing models for predicting the average crack spacing of overlaid beams, the bond deterioration of concrete/steel and PCM/steel bonds was incorporated to predict the flexural crack spacing of overlaid beams at elevated temperatures. The flexural crack width at an elevated temperature was predicted by incorporating the flexural crack spacing and the tensile stress of tension reinforcements in both the substrate beam and overlay at the cracked section. Close agreement was obtained between the experimental and predicted values of the flexural crack spacing and width. (C) 2017 American Society of Civil Engineers.