The 4th Asian Concrete Federation Symposium on Emerging Technologies for Structural Longevity (ACF2023- ETSL)

149 / 2022-04-29 14:51:23

Calcium leaching from cement hydrates exposed to aggressive environments

Calcium leaching; Aggressive ions; Equilibrium curve; Concrete durability

Calcium leaching of cement hydrates increases the porosity and reduces the bonding strength of cementitious materials, compromising the durability of concrete elements exposed to aggressive environments. Previous studies have focused on investigating the leaching process in deionized water or ammonium nitrate solutions, neglecting the effects of aggressive ions concentrations, types, and environmental temperatures. In addition, the selection of critical parameters (x₁, x₂, and C_satu) of equilibrium curve in chemo-transport-damage models are empirical, with no specific equations or criteria. Reported here provide insights into the calcium leaching process of cement hydrates exposed to the sodium sulfate and sodium chloride solutions, respectively. This study was conducted experimentally to examine the effects of concentration and temperature of sulfate and chloride ions. The relationship of critical parameters of equilibrium curves with ions concentrations and temperatures was established quantitatively. The results show that, compared to deionized water, both sulfate and chloride ions accelerate the leaching process, but the latter has less impact than the former. Leaching can be accelerated by increasing the concentration of aggressive ions and decreasing the environmental temperature. The results allow to describe the calcium leaching in saline soil and marine environments, and can be used to calibrate a concrete deterioration model under aggressive ions attack.