Investigation on chloride penetration into unsaturated concrete under short-term sustained tensile loading

Abstract

Knowledge of the transport properties of chloride in unsaturated concrete subjected to sustained tensile loading is essential for evaluating the durability and predicting the service life of reinforced concrete structures. The objective of this study is to fill this gap by correlating the change in water/chloride diffusivity and penetration profiles with an increasing tensile stress level on unsaturated concrete. A theoretical framework for predicting the one-dimensional movement of chloride into unsaturated concrete under tensile stress state, which is closely associated with capillary absorption of water, is presented. An improved test apparatus aimed for the coupled effect of sustained loading and chloride penetration was designed to real-timely measure the amount of water solution absorbed by the cylindrical hollow concrete specimen. A series of chloride transport experiments were conducted on the saturated, half-saturated and fully dried concrete (i.e. ST, HST and DT) respectively subjected to several tensile stress levels (i.e. 10, 20, 30, 40 and 50% of peak tensile strength). Quantitative data on the profiles of chloride penetration into concrete were acquired to validate the proposed theoretical model. The experimental results indicated that the water/chloride diffusivity and the chloride content increase with the increase of tensile stress level in the range of 0–50%. The quantitative relationship between the water/chloride diffusivity and tensile stress level was obtained. On the basis of above analysis, the numerical results of chloride profiles obtained by the proposed model were in good agreement with those of experimental measurement under various tensile stress levels.