Investigating ornamental stone waste as a green supplementary cementitious material in Portland cement mortars

The wet beneficiation process of ornamental stone generates 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 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 wt.%) of Portland cement (PC) by ornamental stone waste (OSW) were analyzed as supplementary cementitious material (SCM). The analysis included compressive strength tests, ultrasonic pulse velocity (UPV) at 7- and 28-day curing, X-ray diffraction, and a simplified carbon dioxide (CO2) emissions analysis. The results indicated that the partial replacement of PC by OSW up to 20% resulted in compressive strengths at 28 days statistically equal to the control sample, which can be attributed to 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.