Recovery of Fine Hydrated Cement from the Cementitious Waste for Circular Cement Production by Selective Grinding

The construction industry is one of the largest contributors to global waste generation, ranking among the top producers of solid waste worldwide. Within the context of construction and demolition waste (CDW), the cementitious fraction stands out as the only component capable of capturing atmospheric carbon dioxide (CO2) and as a viable source of supplementary cementitious material (SCM), thereby mitigating the environmental impacts associated with the anthropogenic CO2 emissions of cement production. This study aims to evaluate the potential of low-energy grinding to enrich the cement paste content in cementitious waste fines. Various grinding conditions were investigated, including different energy levels, ball loads and ball diameters, while maintaining a constant mill filling. The chemical composition in the size fractions, both before and after selective grinding, was determined using X-ray fluorescence. The results indicated that autogenous grinding was not effective because it produced only a small mass fraction of fines (<0.15 mm). The combination of 40 mm and 6.3 mm steel balls yielded the best performance in the conditions tested herein, promoting the migration of cement paste from the coarse fraction to the sand and fine fractions (<4.8 mm); however, the enrichment of cement in the finest fraction (<0.15 mm) remained limited.