Effects of seawater wet-dry cycles on performance and chloride content of RC columns with different initial cracks

The coastal chloride environment and service working condition of reinforced concrete structures was simulated in laboratory. The reinforced concrete (RC) columns under eccentric compressive load with initial crack widths of 0 mm, 0.07 mm, 0.10 mm and 0.14 mm respectively were subjected to 100 cycles of wet-dry alternative actions of seawater immersion and atmosphere exposure to investigate the development of initial cracks. After 100 cycles, the RC columns underwent eccentric compressive loading test and then chloride content in tensile concrete was measured. The experimental results show that as the initial crack width increases, the yield load, ultimate load and ductility of the column specimens reduce. Compared with the experimental results of ultimate bearing capacity, when the crack width is less than 0.10 mm, the relative error of the calculated ultimate load according to Chinese Code is less than 5%. And when the crack width is equal to or larger than 0.10 mm, the relative error of the calculated ultimate load is larger than 16%. On the surface of tensile concrete (depth 0-10 mm), the average chloride content increases as the crack width increases. When the crack width is less than 0.10 mm, the average chloride content in the inner tensile concrete cover (depth 10-30 mm) changes little. And when the crack width is equal to or larger than 0.10 mm, the average chloride content in the inner tensile concrete cover (depth 10-30 mm) increases by nearly times.