Waste derived cementitious eco bricks for non structural use linking compressive strength water uptake and microstructural evidence

This study presents a comparative benchmark of waste-derived cementitious eco-bricks produced with locally available residues in southern Brazil, including rice husk ash (RHA), red ceramic waste (RCW), agate stone waste (ASW), and pecan shell waste (PSW), as well as selected binary blends. All formulations were evaluated under a standardized mix-design rationale in order to compare compressive strength, water absorption, and microstructural evidence on a common experimental basis. The results revealed clear trade-offs among residue types, with RCW- and ASW-based systems showing the best relative mechanical performance, while RHA- and PSW-containing systems exhibited more pronounced limitations. XRD, SEM, and XPS analyses provided qualitative supportive evidence to interpret these trends in terms of packing, porosity, and residue–matrix interaction. However, water absorption remained the main technical limitation across all formulations, indicating that the present results should be interpreted as a comparative screening study rather than as final validation of field-ready products. The main contribution of this work is a standardized composition–performance–limitation map that supports preliminary residue selection and helps define priorities for future optimization of non-structural cementitious components.