Composition-processing-property optimization of multi-waste ceramic wall products based on Ekibastuz TPP ash

The recycling of thermal power plant ash and other industrial wastes in ceramic wall products is a promising strategy for reducing natural clay consumption; however, the interaction between ash dosage, multi-waste composition, pressing time, firing temperature, and ceramic performance remains insufficiently clarified. This study evaluates ceramic wall products based on Ekibastuz thermal power plant ash, red brick waste, metallurgical slag, and glass waste, with emphasis on composition-processing-property relationships and microstructural mechanisms. Ceramic mixtures containing 0-30% thermal power plant ash and selected multi-waste combinations were pressure-molded at 15 MPa, pressed for 60-90 s, dried, and fired at 900-1100 °C. Compressive strength, water absorption, density, and microstructure were assessed to identify the optimal balance between waste incorporation and material performance. The highest performance was achieved by the mixture containing 20% thermal power plant ash, which reached 43.5 MPa compressive strength, 6.1% water absorption, and 2.30 g/cm³ density after firing at 1100 °C and pressing for 90 s. Increasing ash content to 30% reduced strength because of increased residual porosity and microstructural heterogeneity. Multi-waste mixtures containing red brick waste, metallurgical slag, and glass waste produced technically acceptable ceramics but did not exceed the optimized ash-only composition, showing that maximum waste replacement does not automatically provide maximum performance. The main innovation of the study is the identification of a controlled composition-processing-property window in which moderate ash incorporation improves densification and pore refinement, whereas excessive ash or multi-waste loading promotes heterogeneity. The findings demonstrate the engineering significance of optimized waste-derived ceramic systems for sustainable wall-product manufacturing.