Effect of Calcium on Geopolymerization of Aluminosilicate Wastes

The effect of calcium hydroxide on the mechanical and microstructural characteristics of geopolymer produced from alkaline activation of aluminosilicate wastes produced from demolition works were investigated. Demolition wastes are coarse aggregates, including waste concrete and demolished walls with cementing binder, both passing a sieve of 90 µm. A trial was carried out by making a mix containing demolished walls/waste concrete in the ratio of 60/40 % by weight and other mixes having a hydrated lime content of 0–25% of the dry weight as a partial replacement for demolished walls. Half of the waste concrete was substituted with metakaolin, produced by firing kaolin at 800°C for 3 h. The alkaline activators used were sodium hydroxide and sodium silicate in the ratio of 3∶3  % by weight of the dry weight. Curing of the geopolymer mixes was performed at ambient temperature (23°C) in tap water and under a mild temperature of 40°C [100% relative humidity (RH)]. Drying treatment at 80°C for 24 h was carried ou...

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