Elevated temperature performance of high-density alkali-activated slag composites incorporating recycled ceramic waste under sodium, potassium, and rice husk ash-derived silicate activation

High-density concrete finds its application in offshore and marine structures, submerged pipeline ballasting, counterweights and anchors, and significantly in nuclear shielding where fire resistance is also required. Alkali activated binder (AAB) system has shown potential for enhanced thermal resistance. Additionally, there is pressing demand to utilise ceramic waste, rice husk ash (RHA) in construction sector to reduce land fill and promote waste valorisation. Limited research exists that examines slag-based high-density AAB systems incorporating Recycled Ceramic Waste Powder (RCWP) at both ambient and elevated temperatures with varied activator chemistries (sodium/potassium) and alternative RHA-derived silicate solution. Therefore, this study develops high-density AAB with RCWP replacing ground granulated blast furnace slag (GGBS) at 0–20% and evaluates its performance under three different activator systems: NaOH + Na2SiO3, KOH + K2SiO3, and NaOH + RHA. The compressive strength of each system was assessed at ambient conditions and after exposure to 200–800 °C and investigated with XRD, SEM-EDX, and TGA. Results showed enhancement of compressive strength of 4–14% for all systems exposed to 200 °C following progressive degradation at higher temperatures. However, incorporating RCWP reduced the strength of all systems. Potassium-activated systems observed highest strength than sodium silicate or RHA-based activators at 28 days.