Capillary absorption of unsaturated concrete subjected to sustained compressive loading

Abstract

Water penetration into concrete is one of the main factors to cause the deterioration of structures and chloride-induced reinforcing steel corrosion. External sustained mechanical loadings can substantially change the internal pore-structure of concrete and then lead to microcracks, which play a critical role in the durability of concrete because of the provision of additional pathways for aggressive agents (such as chloride ions, sulfate, oxygen, carbon dioxide etc.) to ingress into concrete. This paper presents an experimental investigation into capillary absorption of unsaturated concrete subjected to sustained compressive loading. In order to realize the couple of loading and water absorption process, the hollow cylinder specimens were loaded to different compressive loading levels, and simultaneously tested by an improved device for cumulative absorbed water measurement to conduct a series of water absorption experiments. The focus of this paper is to analyze the experimental results and quantify the influence of external loading and load-induced microcracks on the water absorption of concrete. According to unsaturated flow theory of concrete, the functional relationship with the stress level and sorptivity, which can characterize the tendency of concrete to absorb and transmit water by the capillary mechanism, is reasonably proposed for analyzing the effect of different compressive loading levels on water transport properties. The experimental results indicated that with the increase of applied compressive stress, the rate of capillary absorption of load-damaged concrete initially decreases, and with a further increase in stress level, one markedly increases.