Semi-wet CO2 mineralized modified wollastonite: Application in high-early strength cement and comparative analysis with common supplementary cementitious materials

Mineral carbonation technology is widely recognized as an effective approach for mitigating global warming. This study proposes a semi-wet CO₂ mineralization method to modify wollastonite (WS) and successfully synthesizes a reactive cementitious material—carbonated wollastonite (CWS)—that is rich in carbonate and amorphous SiO₂. This innovative method not only imparts significant pozzolanic activity to the CWS but also enables efficient CO₂ sequestration. This study systematically outlines the CWS preparation process and investigates its influence on the hydration characteristics, microstructural evolution, and performance development of a high-early strength cement (HEC) system. Additionally, a comparative analysis with slag and fly ash is conducted. The results of this study revealed that CWS exhibited a slight hydration inhibition effect in the early stage, which gradually diminished over time. After 28 days, the strength of the CWS system surpassed that of pure HEC, and its resistivity increased by 79.3 %, significantly exceeding the 24.1 % improvement observed in the slag system. CWS not only exhibits pozzolanic activity but also interacts synergistically with the aluminum phase. Its ability to consume calcium hydroxide and generate hydration products surpasses that of slag and fly ash, effectively reducing the total pore volume to a level comparable to that of the pure HEC system. In addition, the unique preparation process of CWS shows an excellent CO₂ sequestration potential of 285.5 g CO₂/kg. This method not only offers an effective solution to mitigate the current shortage of SCMs but also provides a sustainable approach for the construction industry, combining high performance with low carbon emissions.