Fight fire with fire: Mechanistic study of alumina increasing of high-temperature liquid-phase viscosity to suppress the deteriorative effect of potassium on Portland cement clinker

With the widespread use of low-grade high-potassium limestone and solid waste in cement clinker production, the potassium content in Portland cement clinker has significantly increased, leading to a noticeable reduction in the 28-day compressive strength. K + ions, through solid solution, promote the transformation of C 2 S from β-type to α’ L -type, inhibit the formation of C 3 S, and erode C 3 S crystals, resulting in microstructural degradation. Current methods of adding gypsum are limited in effectiveness and often lead to operational and environmental issues. Based on the mechanism where K + ions reduce the viscosity of the high-temperature liquid phase, thereby accelerating their diffusion and migration in the liquid phase, leading to significant solid solution formation in the silicate mineral phases and corrosion of C 3 S, this study proposes a "fight-fire-with-fire" approach. Specifically, it involves increasing the alumina content to create a high-viscosity liquid phase environment that is unfavorable to clinker calcination, thereby hindering the diffusion and migration rate of K⁺ ions. This study systematically investigates the effects of high-temperature liquid-phase viscosity on clinker mineral composition, solid solution, microstructure, and hydration behavior by preparing high-potassium cement clinkers with varying Al 2 O 3 content. The results show that increasing the Al 2 O 3 content significantly increases the liquid-phase viscosity, effectively hindering K + ions diffusion, reducing its solid solution in C 2 S, promoting the formation of C 3 S, and improving crystal morphology, making it shift from irregular to regular hexagonal plate-like shapes. At the same time, the increase in Al 2 O 3 content also leads to a rise in C 3 A content, weakening the stabilizing effect of gypsum on AFt. This, combined with the increase in C 3 S content, ultimately results in the 28-day strength of the clinker showing an initial increase followed by a decrease. It provides a theoretical basis and process direction for the efficient utilization of high-potassium raw materials and performance enhancement. • Proposes a novel method for co-processing high-alkali raw materials and hazardous solid wastes. • Elevated liquid-phase viscosity inhibits K + solid solution in silicates, thereby improving C 3 S morphology. • Clinker achieves optimal 28-day strength when liquid-phase viscosity is between 1.45 and 1.52 dPa·s.