Activation mechanism and performance of full solid-waste cementitious materials using modified concrete waste slurry as an activator

Utilization of industrial solid waste is one of the key pathways to promote the low-carbon transformation of the building materials industry. This study proposes the use of modified commercial concrete waste slurry (CWS) as both alkaline and functional activating components to enhance the hydration and performance of full solid-waste cementitious materials including ground granulated blast-furnace slag (GGBS) and desulfurization gypsum (DG) system. Modified CWS was prepared via wet milling, and its physicochemical properties and activation efficiency were systematically evaluated through laser particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry–differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), mercury intrusion porosimetry (MIP), and compressive strength testing. These methods comprehensively characterized particle refinement, phase evolution, micromorphology, thermal stability, pore structure, and macroscopic mechanical properties, elucidating the activation mechanism by the fact that wet milling enhances particle reactivity and multi-component synergy regulates the hydration process. Results showed that wet-milled modified CWS significantly refined the particle size, with the median diameter (d₅₀) of the optimal blend (CWS+GGBS5%+DG5%) decreasing by 66.6% compared to the blank group. The combined effect of wet milling and component blending facilitated the rehydration of unhydrated particles in CWS and the depolymerization of [AlO₄] and [SiO₄] structures in GGBS, accelerating ion dissolution and hydration product formation. The cementitious materials activated by the composite system achieved compressive strengths of 25.76 MPa at 7 days and 42.93 MPa at 28 days, representing an increase by 62.3% and 14.0% compared to the blank group, respectively. This improvement was attributed to the massive formation and interwoven distribution of AFt and C–S–H gel induced by modified CWS, which significantly optimized the pore microstructure and enhanced the reactivity of the system. This study provides a theoretical basis and technical support for the resource utilization of commercial concrete waste slurry and the development of full solid-waste cementitious materials. • Utilized wet-milled CWS as a composite activator to enable synergistic hydration of GGBS-DG. • Achieved 7d and 28d compressive strengths of 25.76 MPa and 42.93 MPa, representing increases of 62.3% and 14.0%, respectively. • Established a novel pathway for high-performance full-solid-waste cementitious materials.