Effect of crack opening and recovery on chloride penetration into reinforced concrete hollow piles

This study explores the chloride penetration characteristics of reinforced concrete (RC) hollow piles. Special splitting tests were designed to produce different crack widths in the inner and outer surfaces of RC hollow piles. The cracked specimens were then immersed in 5 % NaCl solution for 180 days. The chloride concentration profiles in the cracked zones were obtained by potentiometric titration. This study indicates that the rate of chloride accumulation in the inner pile surface is faster than that in the outer surface for the same exposure time. This may be attributed to differences in the material compositions of the inner and outer surfaces, which are caused by centrifugal processing during specimen preparation. The critical value for V-shaped cracks on the outer surface of RC hollow piles was found to be around 70 µm; however, a critical value was absent for cracks on the inner surface because these present parallel-wall characteristic. In addition, the characteristics of crack development and recovery in the inner and outer pile surfaces were evaluated. The analysis indicates that the depth at which chloride affects the concrete significantly increases with the crack-recovery rate for the apparent crack widths around 130 µm on the outer surface of the concrete layer.