Advancing Green Cement: Reaction Kinetics and Mechanical Performance of Carbonated Wollastonite-Limestone-Gypsum Blended Composites for Sustainable Construction

With the growing global demand for wollastonite, its potential as a supplementary cementitious material has been explored by inducing carbonation.This study investigates the impact of partially replacing cement with varying amounts of carbonated wollastonite (10-50 wt%) while maintaining a constant proportion of limestone (15 wt%) and gypsum (5 wt%).The developed mixes of blended Portland cement (PC) composites were evaluated for mechanical performance in terms of compressive and flexural strength.The results indicate that the mix containing 20 wt% wollastonite, along with 15 wt% limestone and 5 wt% gypsum, exhibited an approximately 30% higher compressive strength compared to conventional mortar, along with a significant increase of about 62% for the flexural strength.X-ray diffraction (XRD) analysis was performed to assess the phase composition, while thermogravimetric analysis (TGA) quantified the portlandite content and chemically bound water.Microstructural analysis further revealed the formation of the main hydration products such as ettringite, portlandite, and anhydrite enhanced structural integrity.The findings highlight the potential of carbonated wollastonite along with limestone and gypsum in enhancing the mechanical and microstructural properties of the cementitious composites.The mixes with 20 wt% wollastonite along with 15 wt% limestone and 5 wt% gypsum exhibited superior performance compared to other the mixes.However, excessive incorporation resulted in a weakened mechanical performance and microstructure.The findings demonstrate the potential for utilizing carbonated wollastonite in the development of eco-friendly binders, contributing to the reduction in the environmental impact caused by the construction industry.