Characterization of carbonated low-lime calcium silicate-based material as potential supplementary cementitious material

Wollastonite (CaSiO 3 ), a low-lime calcium silicate, is not reactive material in an alkaline environment, but after carbonation it can develop binding properties. A material based on wollastonite and other low-lime calcium silicates appears to be a new, innovative supplementary cementitious material, reducing the emissions of cement with its addition. Furthermore, it can capture CO 2 in the process of enforced carbonation. Low-lime calcium silicate-based material was burned in a semi-industrial rotary kiln using secondary raw materials. The obtained material was treated with mineral carbonation. In the following studies, carbonated (CSc) and non-carbonated (CS) low-lime calcium silicate-based material was used as a SCM to replace 30% of clinker (by mass) in Portland cement. The sample with carbonated low-lime calcium silicate-based clinker shows a lower compressive strength compared to the reference sample, but its value oscillates at the level of the strength of the sample with 30%mass fly ash addition. Phase composition analysis (XRD) and thermogravimetric analysis (TG-DTG) were performed on hydrated paste mixtures, after different curing periods. XRD analysis showed the presence of phases typical of the reacting cement. Samples with non-carbonated material show a high content of pseudowollastonite and rankinite even after 180d hydration, which is not observed for samples with carbonated material. TG-DTG analysis showed a decrease in portlandite content during the hydration progression for the sample with carbonated clinker. This indicates the pozzolanic properties of the carbonated material.