Enhanced reactivity and CO2 mineralization of low-lime calcium silicate cement by incorporating nitric acid as an initial calcium leaching agent

Abstract

This study proposed mixing HNO3 solution with low-lime calcium silicate cement (CSC) to enhance the CO2 capture and mechanical properties after CO2-curing by increasing Ca2+ leaching at the initial stage. To clarify the influences of HNO3 and the reaction mechanisms, various molar concentrations of HNO3 (0, 0.01, 0.05, 0.1, 0.2, 0.5, and 1.0 M) were homogenized with CSC using a liquid-to-solid ratio (L/S) of 0.4 and CO2-cured in a pressurized chamber for 24 h. The impact of HNO3 on the initial reaction kinetics, Ca2+ leaching, phase composition after curing, CO2 fixation capability, and mechanical performance were investigated. The findings revealed that the incorporation of HNO3 had a pronounced influence on the degree of reaction, CO2 fixation, and mechanical performance of CSC pastes. Nevertheless, the excessive incorporation of HNO3 had a notable adverse impact on the reaction.

Keywords

• Low-lime calcium silicate cement (CSC)
• CO2 curing
• Calcium carbonate
• Nitric acid
• CO2 sequestration