Optimized cementitious matrices with activated CDW fines: A sustainable path to low carbon cement

By combining the construction industry's commitment to promoting a circular economy with the need to mitigate the environmental impacts caused by the cement industry, this study aims to use three different mechanically (concrete) and thermally (mixed and ceramic) activated construction and demolition waste (CDW) fines as partial replacements for Portland cement in cementitious matrices optimization. The superplasticizer additives contents and the water/fines ratio were controlled for each CDW and cement powder to obtain the lowest intergranular void content and matrix fluidity. The materials were characterized by X-ray diffraction (XRD), thermogravimetry (TGA), X-ray fluorescence (XRF), laser granulometry, Blaine fineness, BET surface area, water absorption, and specific mass. Analyzing the additives’ water/fines ratio and saturation level provided essential parameters for optimizing the mixtures. These parameters, combined with the fines’ reactivity evaluation technique, highlighted the potential of using CDW fines in cementitious matrices. The results demonstrated that the mixtures optimization, combined with the wastes’ reactive potential, controlled the matrix dissolution that was resulted from the replacement of Portland cement, providing compressive strength of up to 49 MPa at 91 days for mixtures with 25 % CDW fines, surpassing the reference matrix and demonstrating the potential of the technique to optimize mixtures with CDW fines for a more sustainable cement.