Dissolution Characteristics of Cement Paste Using Quick Setting Admixture for shotcrete

Abstract

For the purpose of clarifying the dissolution characteristics of shotcrete used for tunnel lining of radioactive waste repositories, the cement was mixed with a quick setting admixture, and immersion tests were conducted. The quick setting paste was ground after hardening and contacted with pure water in a few months of testing. As a result, it was confirmed that more ettringite was produced in the cement paste with the quick setting admixture, which consisted mainly of calcium sulfoaluminate, than in the cement paste without the quick setting admixture. Immersion of the cement paste in water was also confirmed to result in the dissolution of Ca(OH)₂ and monosulfate and further formation of ettringite. Furthermore, it was clarified that Calcium ions, Sulfate ions, and Aluminium ions are being consumed for the production of ettringite, and these ions do not readily leach to surrounding water. Based on these test results, a dissolution equilibrium model for shotcrete was developed in order to evaluate the durability of the barrier system or pH plume for the underground repositories.