Performance simulation and quantitative analysis of cement-based materials subjected to leaching

Abstract

A 3D numerical modelling platform (MuMoCC) developed in a previous work by the authors is applied in this paper to investigate the effect of leaching of some solid phases of cement paste (portlandite and hydrated aluminates or sulfoaluminate phases) on the mechanical and diffusivity performances of cement paste and mortar. The platform is based on a multi-scale approach and uses two numerical tools. First, NIST’s CEMHYD3D code is used to simulate 3D Representative Volume Elements of cement paste and mortar. Then mechanical and diffusivity behaviour of the numerical materials are simulated using ABAQUS software. The proposed three-dimensional heterogonous model presents at least two advantages. Firstly, it is able to capture the complexity of the random microstructure of cement-based materials. Secondly, only a few parameters have to be fitted compared to the other existing models, which indicates the relevance of the model. The numerical simulations of leached cement paste and mortar performance highlight and quantify the significant effect of portlandite and hydrated aluminate and sulfoaluminate phases’ dissolution on the decrease of elastic modulus and compressive strength and on the increase of ductility and diffusivity. The numerical results show that the leaching of portlandite decreases the compressive strength of a w/ c = 0.4 cement paste by a factor of 1.33. The dissolution of portlandite and hydrated aluminates or sulfoaluminate phases involves a decrease by a more important factor (1.86). The leaching of portlandite phase involves an important increase, by a factor of 31, of the effective diffusion coefficient. Using the developed multi-scale modelling and knowing the leaching kinetics values, the mechanical and diffusion performances of cement-based materials can be estimated correctly according to leaching duration.