Use of ornamental rock sludge and calcium carbonate sludge in the production of limestone calcined clay cement

Abstract This study aimed to evaluate the use of sludge from the processing of ornamental rocks and calcium carbonate sludge as filler, replacing limestone up to 15%, in limestone calcined clay cement (LC 3 ), to minimize the extraction of non-renewable natural resources and the environmental impacts caused by the incorrect disposal of these industrial solid wastes. For this purpose, isothermal calorimetry, thermogravimetry, X-ray diffraction, rotational rheometry, compressive strength, and environmental analyses were performed on cement pastes. The results showed that the waste did not affect the hydration process, behaving similarly to limestone with a filler effect. There is greater formation of monocarboaluminate after 1 day in formulations with CCS, due to the greater availability of carbonates resulting from their higher purity. The yield stress and viscosity of the pastes decreased progressively with increasing substitution levels up to 10%. Regarding the microstructure, all pastes presented similar compact matrices and porosity. Compressive strength was altered due to the physical characteristics of the filler materials. The reductions in ECO 2eq. and embodied energy was substantial, indicating greater material potential than OPC. Therefore, the feasibility of reusing the above waste materials is satisfactory, contributing to the production of more sustainable binders.