Effect of mineral admixtures on the tobermoritization in monticellite

The formation of tobermorite serves as a critical link between inert solid wastes and high-performance materials. This study systematically investigates the effects of four mineral admixtures-kaolin, fly ash, ground granulated blast-furnace slag, and silica fume-on the tobermoritization process of monticellite, as well as the relationship between the underlying mechanisms and the resulting material properties. The results indicate that the mixture with 20 wt% silica fume achieved the highest compressive strength (35.9 MPa) and the maximum dry density (1888.75 kg/m³), which can be attributed to the highly reactive SiO₂ directly facilitating the formation of fibrous tobermorite. Kaolin, at a 20 wt% dosage, enhanced the strength by 5.38 times through aluminum doping, leading to the formation of a highly cross-linked C-A-S-H gel. The strengthening effect of slag was found to be inferior to that of silica fume and fly ash. Mineral admixtures promote tobermorite formation by regulating the Ca/Si ratio, supplying reactive sources of silicon and aluminum, and optimizing the microstructure. This research provides a theoretical basis for controlling the phase transformation of monticellite.