MgO Doping on the Sintering and Carbonation Properties of Ternesite

Abstract

Ternesite has been proven to have significant competitiveness as an ultralow lime CO₂ sequestration binder. It is worthy of industrial production for CO₂ emission reduction in the cement industry. MgO is inevitable in natural limestone, which may change ternesite’s sintering and carbonation properties. This study aims to simulate the effect of MgO content on the sintering and carbonation behavior of ternesite. The results show that less than 4% Mg²⁺ is dissolved in the crystal structure of ternesite by replacing Ca²⁺ and induces a reduction of cell size. More than 4% MgO will be sintered to form bredigite and merwinite, restraining ternesite content in clinkers. The compressive strength of ternesite clinker compacts is negatively correlated with the MgO doping content. The increase in MgO doping from 0 to 20% resulted in a 68.2% decrease in compressive strength. MgO doping less than or equal to 3% improves the CO₂ sequestration capacity of ternesite clinkers by 4.1%; however, more than or equal to 5% will reduce the CO₂ sequestration capacity. The analysis of carbonation products showed that MgO reduced the content of aragonite and vaterite and induced the formation of magnesian calcite and monohydrocalcite. The difference in ternesite content, crystal morphology, and carbonation products is the reason for the change in carbonation properties of MgO-doped clinkers.