Predicting the calcium leaching behavior of cement pastes in aggressive environments

Researches have shown the decrease of mechanical properties of cementitious materials with the growth of leaching duration. But the relationship between mechanical properties and leaching duration was not quantified yet in the published literature. The purpose of this paper is to predict calcium leaching behavior of cement pastes immersed in aggressive solutions. Since nature leaching is a slow process, the accelerated experiment has been performed by using a 6 mol/l ammonium chloride solution. To quantify the leaching development, the leaching depths of cement pastes specimens were measured after leaching for particular durations. Compression test and Vickers hardness test were also performed. Based on experimental data, the relationship between average Vickers hardness and leaching duration was constructed by a simplified model. The influence of water to cement ratios on the prediction was also considered. Then the relationship between average of Vickers hardness and compressive strength was obtained. Finally, the long-term forecast of compressive strength was made, and the predicted values were compared with the available experimental data obtained from the specimens leached for 385 days, indicating a good reliability of these simplified models.

▸ Ammonium chloride solution was used as the leaching medium in the accelerated leaching procedure. ▸ A technique for long-term prediction of average Vickers hardness of the leached pastes was established. ▸ The relationship between average Vickers hardness and compressive strength was proposed. ▸ The long-term forecast technique of compressive strength of degraded pastes was constructed.