Hydration products, microstructure, and mechanisms of titanium-extracted slag oilwell cement composite binders

Conventional admixtures for oil well cement are associated with high costs and inadequate utilization of industrial solid wastes. This study addresses these challenges by introducing modified Titanium-extracted slag (TES) as a sustainable alternative. It was observed that the hydration of TES leads to the formation of layered double hydroxides (LDHs) within the cementitious matrix. To enhance its reactivity, TES was modified through ball milling, washing, and calcination. The washing process effectively reduced the chloride ion (Cl−) content, while calcination shortens the average chain length of silicate glass and promotes the release of Al3+, thereby increasing its amorphous activity. The hydration behavior and microstructural evolution of TES-blended cementitious composites were systematically investigated using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Furthermore, the hydration mechanism was elucidated by applying the Krstulovic–Dabic (K–D) kinetic model. Results indicate that both washed and calcined TES promote the formation of calcium aluminosilicate hydrate (C–(A)–S–H) gels and LDHs. These phases enhance the density of the cement stone by improving the connectivity of the C–(A)–S–H network and filling pores with LDHs. In summary, this study demonstrates that the tailored incorporation of modified TES enables simultaneous waste valorization and enhancement of cement stone properties, offering an eco-friendly and cost-effective solution for high-temperature well cementing applications.