Investigation on the hydration and strength properties of belite cement mortar containing industrial waste

This work assessed the properties of the hydration processes and the strength development of synthesised belite cement samples. The belite clinker was synthesized in the high-temperature furnace by calcining the mixture of industrial waste (similar to 18%) (granite cutting waste and silica-gel waste from AlF3 production) and natural raw materials (similar to 82%) at 1150 degrees C temperature for 2 h. It was obtained that the produced binder was composed mainly of larnite, mayenite, srebrodolskite, ye'elimite, and gehlenite. Furthermore, the synthesized clinker was blended with gypsum (5-20%) to determine the required amount of gypsum additive for the hydration process. The results of microcalorimetry analysis showed that the amount of gypsum plays an important role in the hydration process because, in the samples with 5% or 7.5% of additive, two exothermic reactions were identified, while in the samples with a higher amount of additive 3-4 exothermic reactions were identified. The mechanical properties of prepared concrete were determined by curing the standard prisms (according to the standard of EN 196-1, cement/sand =1:3, w/c = 0.67) in an aqueous (25 degrees C, for 3-90 days) or hydrothermal (90 degrees C, 125 degrees C, or 175 degrees C, for 24 h) environment. The results of a compressive test demonstrated that the curing method significantly affects the compressive strength development of produced belite concrete, and the highest value (> 18 MPa) was obtained after hydrothermal curing at 175 degrees C. The mineralogical composition of formed hydrates was determined by X-ray diffraction analysis and simultaneous thermal analysis.