Theoretically Identified Strong Coupling of Carbonation Rate and Thermodynamic Moisture States in Micropores of Concrete

Abstract

In order to predict the chemo-physical process of carbonation, a finite element based computational method is implemented based upon multi-phase/scale governing equations of moisture and flux of both heat and carbon dioxide. Influencing parameters of carbonation involving reaction rate, CO₂ diffusivity and the reduction of porosity are discussed. It is found that such modeling can accurately show high nonlinearity among carbonation reaction, pore structure development and moisture distribution in micropore structures. By using the proposed assumptions, the reliability of the predictive method of the carbonation mechanism in cementitious materials under arbitrary environmental and curing conditions is examined by comparing available experimental results with theoretical ones. Through sensitivity analyses that focus on the nonlinearity of the moisture profile and local carbonation, it is clarified that different moisture distribution may bring the opposite trend of the carbonation depth under low and high CO₂ concentrations.