Ceramic Effluent Treatment Plant Sludge as a Partial Cement Replacement in Sustainable Concrete: A Review of Fresh, Mechanical and Durability Performance

The production of Ordinary Portland Cement is associated with high energy consumption, depletion of natural resources, and carbon-dioxide emissions. Simultaneously, ceramic industries generate quantities of Effluent Treatment Plant (ETP) sludge during washing, cutting, polishing, glazing, and wastewater treatment operations. Disposal of this mineral sludge in landfills creates environmental and land-use problems. This review examines the potential of ceramic ETP sludge and ceramic waste powders as partial cement replacements in sustainable concrete. Published studies were reviewed with emphasis on material characteristics, workability, compressive strength, split tensile strength, flexural behaviour, water absorption, permeability, chloride penetration, acid resistance, and sulphate resistance. The literature indicates that the performance of ceramic-waste concrete depends on replacement level, particle size, chemical and mineralogical composition, water-to-binder ratio, and curing duration. Workability generally decreases because fine ceramic particles increase surface area and water demand. Moderate cement replacement, commonly between 10% and 20%, can improve particle packing, pore refinement, strength, and resistance to aggressive agents. Excessive replacement may reduce strength because of cement dilution and insufficient reactive binder. The review concludes that ceramic ETP sludge has promising potential as a supplementary cementitious material, but standardised characterisation, long-term durability assessment, leaching studies, and field-scale validation are required before widespread structural application.