Investigation of leaching behaviors of carbonation-cured CSA cements using an electrically accelerated leaching test

Abstract

The present study provides the investigation of leaching behaviors of carbonation-cured calcium sulfoaluminate (CSA) cements with varying initial sulfate contents using an electrically accelerated leaching test. The CSA cement samples were normally or carbonation-cured for 28 days before subjecting them to an electrically accelerated leaching condition for 14 days. The samples were characterized experimentally before and after accelerated leaching. In addition, the leaching behaviors of the CSA cement samples over a wide range of cumulative leached water were thermodynamically modeled to determine their likely performance in repository environments. The results indicate that the reaction of ye'elimite was significantly promoted by accelerated leaching, resulting in the formation of ettringite after leaching, regardless of the curing regime used. Calcium sulfates and C-(A)-S-H formed in the carbonation-cured samples were the first phases to decompose upon accelerated leaching, which is in good agreement with the thermodynamic modeling calculations. For the normally cured samples, the use of higher calcium sulfate in the mixture is preferred, considering the amount of leached ions, yet the opposite holds true for the carbonation-cured samples. In particular, the changes in the calculated volumes of the reaction products upon simulated leaching were smaller for the carbonation-cured samples than for the normally cured samples.