Feasibility study on developing alkali-activated cementitious materials via calcination-induced structural...

To promote the high-value utilization of industrial solid-waste carbide slag (CS) and low-reactivity illite, this study employed CS-assisted co-calcination to reconstruct the illite structure and improve its reactivity as a cementitious material. The modification process was systematically evaluated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The results indicate that CS addition during calcination disrupts the illite crystal structure and promotes the formation of a more disordered calcium-bearing aluminosilicate precursor. Alkali-activated cementitious materials (AACs) were then prepared from the modified samples, and the effects of CS dosage, curing temperature, calcination temperature, and grinding time on mechanical performance and reaction products were investigated. Within the investigated range, specimens incorporating 10 % CS showed an approximately 280 % increase in compressive strength compared with the CS-free counterpart, while 20 % CS provided a favorable balance between calcium supply and residual Ca-bearing phases. Prolonged grinding time promotes the alkali activation reactions. A 20 % CS dosage provides sufficient Ca²⁺ to optimize the Ca/Si ratio, thereby promoting the formation of hydrate gels. This work demonstrates the feasibility of transforming carbide slag and low-grade clays into value-added cementitious materials, providing a promising route for industrial solid-waste valorization and expanding the raw-material resources for alkali-activated binders.