Viabilidade técnica e ambiental da lama do beneficiamento de rochas ornamentais como material cimentício suplementar em argamassas de cimento Portland

Abstract

The wet beneficiation process of ornamental stone generates a waste in the form of sludge that, after drying, becomes a non-biodegradable fine powder. Its improper disposal can lead to various negative environmental impacts. Therefore, new destinations for the waste should be evaluated in search of innovation and sustainability. In Brazil, this issue is of particular interest since the country stands out globally as one of the largest producers of ornamental stone, generating significant quantities of waste annually. Thus, mortars with replacement percentages (5%, 10%, 15%, and 20%) of Portland cement (PC) by ornamental stone beneficiation sludge (LBRO) were analyzed as supplementary cementitious material (SCM) at curing ages of 7 and 28 days. The analysis included compressive strength tests, ultrasonic pulse velocity (UPV), X-ray diffraction, as well as a simplified analysis of carbon dioxide (CO2) emissions. The results indicated that the partial replacement of PC by LBRO up to 20% resulted in compressive strengths at 28 days statistically equal to the reference, which can be attributed to the synergistic effect between the waste and the limestone filler present in PC, resulting in the formation of AFm phases. When analyzing the CO2 emissions of the samples, higher substitution percentages were associated with lower reported emissions, reaching a reduction of 61.4% when comparing the 20% replacement with the reference.