Hydration kinetics and mechanical performance of cement pastes with copper slag as supplementary cementitious material
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Date
2025
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Abstract
The growing global demand for concrete infrastructure and cement highlights the need to mitigate the environmental impact of cement production. Incorporating alternative supplementary cementitious materials (SCMs) has emerged as a promising strategy. This research investigates the effect of copper slag (CS), a significant global mining-sector waste, as SCM in cement pastes, focusing on hydration and mechanical performance in both the short and long term. CS was used as SCM at dosages of 0 %, 10 %, 20 %, 30 %, and 50 % by volume. The hydration evolution of cement paste mixtures was evaluated using isothermal calorimetry, compressive strength tests, X-ray diffraction (XRD), differential thermogravimetry (DTG), and field emission scanning electron microscopy. Results indicate that up to 20 % CS replacement did not negatively affect compressive strength in the long term, while dosages above 20 % led to a monotonic reduction. XRD and DTG analyses validated the pozzolanic effect of CS, evidenced by the formation of new Fe-siliceous hydrogarnet phases and a reduction in CH content at later ages. Additionally, a predictive model combining random forest and polynomial regression techniques was developed to accurately forecast compressive strength as a function of CS dosage and curing time. This study concludes that incorporating up to 20 % CS as SCM can reduce CO2 emissions associated with the clinker factor without significantly compromising long-term mechanical performance, and offers a viable alternative for greener cement production.
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Keywords
Copper slag, Cement paste, Compressive strength modelling, Filler effect, Pozzolanic activity, Hydration