Finite element analysis on the diffusion-reaction-damage behavior in concrete subjected to sodium sulfate attack

Abstract

The deterioration of concrete caused by sodium sulfate attack (SSA) is a process of volume expansion and cracking layer by layer, causing the external solution to flow directly into concrete. Taking ettringite type of SSA as an example, this paper studies the SSA-induced deterioration of concrete. Based on Fick’s law and reaction kinetic theory, the diffusion-reaction model of sulfate ion in concrete is proposed. Introducing the crack density coefficient, the chemical damage of concrete is characterized by expansion strain caused by sulfate products, and then the condition of boundary movement is further established. Using the finite element method, the Crank-Nicolson-Galerkin scheme governing equation of diffusion-reaction model is developed. On the basis of model validation, a numerical simulation is performed to analyze the temporal-spatial variation of sulfate ion and damage degree in concrete. The result show that, the SSA-induced cracking of concrete obviously lags behind the ion diffusion and chemical reaction.