Numerical simulation on the crystallization-induced mechanical response in hardened cement paste under external sulfate attack

Durability degradation caused by external sulfate attack (ESA) is one of major reasons for early failure of concrete structures served in coastal and marine environments. This paper proposes a simplified chemo-mechanical model to analyze the behavior of ESA on hardened cement paste (HCP), namely the diffusion-reaction and expansion-mechanical process. In this work, the crystallization pressure from the supersaturated pore solution is the driving force of local expansion of HCP, and the filling process of ettringite crystal in porous system is explained in detail. Then, the equivalent expansive eigenstrain of local HCP is calculated by crystallization pressure, and used to quantitatively characterize the ESA-induced chemical damage. Finally, the global mechanical response in HCP specimen is analyzed by introducing the expansive eigenstrain, which is considered to be the direct cause of mechanical response. The simulational results of sulfate concentration, crystallization pressure and expansion deformation show consistency with experimental data. Additionally, despite the lack of experimental data on mechanical response, the simulational result of expansive stress satisfies the force equilibrium.