Carbonation behavior and mechanism for improving the performance of hardened magnesium silicate hydration paste

This study investigated the phase and microstructural evolution of magnesium silicate hydration systems during carbonation and characterized the reaction kinetics. The results indicate that the carbonation products comprise both crystalline and amorphous hydrated magnesium carbonates (HMCs). With extended reaction durations, the HMCs crystals gradually expand and coexist with the system’s original components. The carbonation reaction demonstrates selective reactivity toward the phases within the system, with Mg(OH)2 as the primary active site. This phase undergoes nearly complete carbonation, leading to the formation of amorphous HMCs that occupy the pores. This process is the principal factor contributing to the observed enhancement in compressive strength. Meanwhile, the structure of M-S-H evolved during carbonation, with its degree of polymerization increasing with carbonation time. After 48 h of carbonation, CO2 sequestration capacity reached 131.5 kg/t, while the compressive strength increased to 35.1 MPa. The excellent performance provides the potential for the future application of this system.