Modelling the degradation of mechanical properties of cementitious materials under leaching

Abstract

The calcium leaching of hydrated cement system when in contact with external solution has long been recognised as a critical problem for cementitious materials, and it can result in degradations on mechanical properties. In this research, an integrated numerical scheme is developed to simulate the degradation of Young's modulus of cementitious materials under leaching. Firstly, a cement hydration module is proposed and employed to predict the characteristics of the hydrated cement including pore structures, contents of hydrates and concentrations of initial interstitial solution. Then the hydration data obtained are incorporated into a coupled reactive diffusion procedure to evaluate the change of hydrate contents under the prescribed boundary conditions. Finally, a micromechanical approach, Mori-Tanaka method, is employed to evaluate the degradation of Young's modulus of the cementitious material. The accelerated leaching tests in 6M (6 mol L ⁄ ) of ammonium nitrate solution, which became popular recently in view of the extremely slow degradation kinetics of leaching in deionized water, are studied numerically in this study. The developed numerical scheme is employed to model two experiments, and the good agreements between the numerical results and the experimental measurements in terms of hydration outputs, leaching profiles and Young's moduli, demonstrate the applicability and accuracy of the proposed numerical scheme.