Strength optimization of geopolymer pastes synthesized from high calcium bottom ash and red clay: A study of composition and activation parameters

This study aims to synthesize and enhance the strength of geopolymer pastes using high-calcium bottom ash (BA) and red clay (RC), both abundant and sustainable resources. The physical and chemical properties of the synthesized geopolymer pastes were evaluated by investigating key synthesis parameters, including the BA/RC weight ratio, the SiO2/Al2O3 mole ratio, the Na2O/Al2O3 mole ratio, and the concentration of sodium hydroxide. Various ratios of BA and RC were combined with alkaline activators of sodium hydroxide and sodium silicate to prepare the geopolymer pastes. The optimal conditions for achieving the highest compressive strength were identified as a BA/RC weight ratio of 90/10, a SiO2/ Al2O3 mole ratio of 6, a Na2O/Al2O3 mole ratio of 2, and activation with 10 M sodium hydroxide. Compressive strength increased with a higher SiO2/Al2O3 mole ratio, while an elevated Na2O/Al2O3 mole ratio initially reduced strength. Additionally, the dissolution of silica and alumina from the BA and RC precursors significantly improved with increased sodium hydroxide concentration. This research supports environmental sustainability by reducing industrial waste, minimizing reliance on Portland cement, and promoting circular economy principles through the development of high-strength, eco-friendly construction materials.

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Opracowanie rekordu ze środków MNiSW, umowa nr POPUL/SP/0154/2024/02 w ramach programu "Społeczna odpowiedzialność nauki II" - moduł: Popularyzacja nauki (2025).