Low-emission wollastonite clinker and its effect on the properties of cementitious binders

The aim of the investigation was to synthesise clinker based on wollastonite and carbonate it afterwards to be used as a potential new supplementary cementitious material. The clinker was burned in a semi-industrial rotary kiln with a capacity of approx. 50 kg/h at 1240 °C using secondary raw materials. The synthesised clinker was composed mainly of rankinite and pseudowollastonite, which are carbonatable. The burned clinker was treated by direct carbonation in a wet process. The carbonation products included calcium carbonate in various polymorphic forms, as well as an amorphous phase, mainly amorphous silica. The latter can react as a pozzolan in blends with Portland cements. The use of the carbonated clinker as supplementary cementitious material can lead to lower CO2 emissions compared to plain Portland cement, due to the lower consumption of carbonate-containing raw material, the lower synthesis temperature and the possibility of CO2 sequestration.