An innovative strategy for CO2 conversion and utilization: Semi-wet carbonation pretreatment of wollastonite to prepare carbon-fixing products and produce LC3

Abstract

Limestone calcined clay cement (LC³) is considered the most promising alternative to Portland cement. This research proposes an innovative carbon conversion and utilization strategy that provides greater flexibility in the production of LC³. In this study, a carbon-fixing product with a CO₂ uptake of 29.39% was prepared via semi-wet carbonation pretreatment of wollastonite. This product can be used to replace limestone in LC³ and play an effective synergistic role. This study was conducted to investigate the morphology and phase change of carbonated wollastonite (CWS) before and after preparation. The effects of CWS and natural wollastonite on the hydration kinetics, workability, mechanical properties, and durability were investigated through comprehensive experiments. Furthermore, the composition, porosity, and microstructural changes were characterized and analyzed. The results show that CWS has multiple properties, such as carbonate properties, synergistic effects, and pozzolanic reactions. Using CWS as a carbonate source in LC³ increased the compressive strength and resistivity by 11.1 % and 36 %, respectively. The mortar exhibited increased carbonation durability because of the densification effect on the microstructure of the amorphous silica gel. The superposition of the synergistic effect and pozzolanic reaction reduced the total porosity of the hardened paste from 28.32 % to 21.43 %. The results of this study highlight the potential value of carbon-fixing products in the development of LC³ composites and additional CO₂ utilization opportunities. This study also explored the future development prospects of this strategy, which is expected to provide new ideas and a practical basis for promoting the sustainable development of the construction industry.