Valorization of Ceramic Waste Powder for Compressive Strength and Durability of Fly Ash Geopolymer Cement

Enormous amounts of ceramic and fly ash (FA) wastes are generated annually by ceramic industries/demolition/rejected units and thermal power plants. To preserve virgin natural resources, limit disposal amounts, and limit environmental pollution, these wastes can be applied in the construction field as a binder material after alkali activation. This work aims to get rid ceramic waste powder (CWP) by recycling it as a part of FA geopolymer cement activated with sodium silicate to get improved properties, especially those after exposed to severe conditions. For this purpose, the FA was partially replaced with CWP at levels ranging from 10 to 50% with a stride of 10 wt.%. The effect of CWP on the flowability, compressive strength, up to 240 days, and different durability aspects were investigated. After curing for 28 days, specimens were subjected to three different types of durability: accelerating aging, wetting/drying cycles in sodium sulfate solution, and simulated tidal zone. The identification of the different decomposition phases was accomplished through the utilization of X-ray diffraction (XRD), thermogravimetric analysis (TGA)/its derivative (TGA), and scanning electron microscopy (SEM). The results showed 27.5-55% reduction in the flowability with including 10-50% CWP. The compressive strength increased with including up to 40% CWP. The 28 days compressive strength was enhanced by 20.1-42.97% with including 10-40% CWP. All different types of properties were enhanced with the incorporation of up to 40% CWP. Contrarily, incorporating 50% CWP showed a negative effect on compressive strength and different types of durability. The XRD of the neat FA geopolymer sample before and after exposure to severe conditions showed the crystalline phases of quartz, hematite and mullite, whilst that containing CWP showed the crystalline phases of quartz, mullite, hematite and albite. The TGA analysis showed the formation of aluminosilicate (N-A-S-H) gel as the main hydration product in the samples with/without CWP, the amount of this gel decreased after exposure to severe conditions.