Optimizing wollastonite treatment to enhance sustainability and reduce carbon emissions in cement-based materials

Abstract

The sustainable use of natural minerals in construction materials is vital for minimizing the cement industry's environmental impact. Wollastonite, a calcium silicate mineral, offers significant potential as a supplementary cementitious material to reduce carbon emissions and enhance performance. However, the optimal treatment method for maximizing its effectiveness and sustainability remains uncertain. This study evaluates untreated, carbonated, and acid-leached wollastonite through comprehensive analyses of hydration behavior, microstructure, mechanical properties, and life cycle assessment (LCA). The results show that acid-leached wollastonite, with its high pozzolanic activity arising from amorphous silica gel formation, provides the strongest mechanical enhancement and densifies the matrix. However, after explicitly accounting for HCl production and treatment of the Ca-rich acidic wastewater, the carbonated-wollastonite route exhibits the lowest strength-normalized life-cycle carbon footprint. The 10,000-run Monte Carlo analysis confirms that CWS has a lower carbon footprint than both WS and LWS at all three replacement levels with a probability of 100%, whereas LWS20 provides the best environmental performance within the acid-leached route. These results demonstrate that the preferred treatment depends on the balance between treatment-related burdens and mechanical-performance gains rather than on reactivity alone.