Design of all-solid-waste cementitious materials as cement substitutes: Performance comparison, mechanism correlation and system screening

To evaluate the suitability of all-solid-waste cementitious materials (ACMs) as alternatives to ordinary Portland cement (OPC) in engineering applications, this study designed a multi-solid-waste composite activation system based on calcium carbide slag (CS), sodium-based desulfurization ash (SDA), and desulfurization gypsum (DG). The performance of the developed systems was systematically assessed in terms of workability, fresh mortar rheology, and early-stage hydration kinetics. Results revealed significant performance variations among the activation systems. The S series (SDA-CS) exhibited high early hydration activity but posed a risk of expansion and instability due to its high sodium content. The C series (CS alone), with low alkalinity, showed sluggish hydration and inferior strength compared to the D and S series. In contrast, the D series (DG-CS) demonstrated the best overall performance, meeting and even exceeding OPC requirements in both strength and stability. Isothermal calorimetry was employed to analyze the hydration behavior of ACMs. By integrating the Knudsen extrapolation method with the K-D hydration kinetics model, the hydration pathways and rate-controlling mechanisms of each system were elucidated. The study verified a correlation between compressive strength at different ages and cumulative heat release. Additionally, using the M-B rheological model, a negative correlation was identified between plastic viscosity and mortar fluidity. These analyses systematically revealed the intrinsic relationships between macroscopic properties and early-age hydration and rheological behavior. Bridging performance screening with mechanistic insight, this study provides a theoretical foundation for the rational design and safe application of ACMs in engineering contexts.