Numerical simulation on transport-crystallization-mechanical behavior in concrete structure under external sulfate attack and wetting–drying cycles

Abstract

External sulfate attack (ESA) coupled with wetting–drying alternation poses a significant threat to the concrete durability, while there are few models to simulate the above ESA behavior. In this paper, a simplified transport-mechanical model is proposed to numerically analyze the deterioration of concrete prism under ESA and dry-wet cycles. Firstly, a transport model of sulfate ion in concrete prism is established by considering the behaviors of ion diffusion, convection and chemical reaction, and numerically solved by the finite difference method. Secondly, the crystallization pressure of sulfate products in porous system is analyzed to calculate the equivalent expansion force. Then, the expansion strain and its-induced damage are calculated, and the criterion of boundary movement is further proposed. On the basis of model validation, a numerical simulation is performed to analyze the transport-mechanical response in concrete prism under ESA and dry-wet cycles. The results show that, there is no clear demarcation between the convection and diffusion zones in the prism. The spatial–temporal evolution of ESA-induced damage is similar to that of ion concentration. The longer the wetting time in one dry-wet cycles, the deeper the spalling of concrete prism caused by ESA.

Keywords

• Unsaturated concrete
• External sulfate attack
• Wetting-drying cycles
• Moisture and ion Transport
• Mechanical response