Recycling pulverized concrete as cementitious precursor in alkaline one-part cements, with a waste glass-based sodium silicate

This study investigates the recycling of pulverized hardened concrete (PHC) as a cementitious precursor in onepart alkali-activated cements. Two sodium silicate activators were compared: a commercially available option and an alternative derived from waste glass. Pastes with varying PHC:activator ratios (70:30 to 90:10) were cured for 24h at 20, 60 and 80 degrees C, then completed 28-days at 20 degrees C in air and underwater. Higher initial curing temperatures promoted early strength, but all pastes exhibited continued hydration and strength gains at 20 degrees C. All pastes displayed hydraulic characteristics. The PHC with the waste glass-based activator achieved 28-day compressive strengths up to 20 MPa for 70-80% PHC. These cements showed significantly lower CO2 emissions, embodied energy, and cost compared to those prepared with the commercial activator and a Portland cement. This research lays the groundwork for further investigations on sustainable precursors and activators in alkali-activated cements, aiming to optimize binder properties for broader applications.