Valorization of kaolin waste via comparative calcination screening for alkali-activated binders in oil-well cementing

Although kaolin waste has been widely explored as an alkali-activated precursor, the relationship between calcination conditions and binder performance remains insufficiently understood. This study investigates the influence of calcination parameters on kaolin waste by varying temperature (550–850 °C) and residence time (2–6 h) to enhance its use in alkali-activated materials (AAMs) for oil-well cementing. Structural characterization (XRD, FTIR, SEM) indicates that calcination at 750 °C for 4 h provides the most suitable balance between kaolinite dehydroxylation and structural disorder. The material calcined under the selected condition was used as the main precursor in hybrid AAM binders with ground granulated blast furnace slag (GGBFS), varying precursor ratios, activator composition, and water content. Mechanical performance was evaluated according to American Petroleum Institute (API) procedures. Despite the presence of inert phases, the selected system enabled effective aluminosilicate gel formation, achieving compressive strengths up to 29.78 MPa at 28 days and exceeding the API screening threshold (~ 3.45 MPa at 24 h). The results demonstrate that performance depends on the combined effect of precursor activation and mix design, rather than maximum amorphization alone. This study highlights the potential of kaolin waste valorization as a viable pathway for low-carbon cementitious materials in energy applications.