Transforming construction and demolition waste concrete as a precursor in sustainable cementitious materials: An innovative recycling approach

Construction and demolition wastes amount to 10,000 Mt/year worldwide, a large fraction of these is concrete, along with other potentially useful constituents, like bricks, ceramics, glass, etc. This study investigates the potential of harnessing this environmental passive into cementitious precursors in novel one-part alkaline cements, in which pulverized hardened concrete was blended with 0–80 % of Portland cement and activated with 15 % Type G sodium silicate. Paste specimens underwent curing at 20 or 60 °C for 24 h and then completed 28-days at 20 °C under dry and underwater conditions to test the hydraulicity. The pastes cured at 20 °C having 45 and 25 % recycled concrete reached 45 and 50 MPa, respectively; further characterization suggested the formation of cementitious gels like C-S-H and silica gel. An evaluation of the environmental footprint as CO2 emissions, energy requirements and cost suggest that these novel cements offer a promising and sustainable alternative for the construction industry.