A comparative review of concrete properties using waste materials as natural coarse aggregate substitutes

Natural aggregate is being extracted faster than it is replaced, while mineral and industrial waste continues to accumulate. This review synthesizes the published evidence on fourteen waste materials used as partial or full replacements for natural coarse aggregate in concrete: recycled concrete, crushed brick, ceramic, waste glass, plastic, tyre rubber, sintered fly-ash lightweight aggregate, coconut shell, oil-palm shell, steel slag, waste marble, granite waste, coal bottom ash and e-waste. Of 538 records identified, 154 studies met the eligibility criteria. Only investigations that replaced coarse aggregate and reported a natural-aggregate control contributed to the comparative synthesis; fine-aggregate and binder-replacement studies were retained solely to explain mechanisms. A three-family classification is proposed on the basis of density, porosity and surface chemistry: dense and low-porosity streams (steel slag, marble, granite, glass, vitrified ceramic), porous and water-absorbing streams (recycled concrete, brick, sintered fly-ash aggregate, bottom ash, bio-based shells), and polymeric and hydrophobic streams (plastic, rubber, e-waste). Dense, low-porosity streams maintained or increased strength and reduced the transport of water and ions. Porous streams reduced hardened density by approximately 25–30% and increased absorption, with most investigations limiting replacement to 20–30% for structural applications. Polymeric streams reduced strength substantially while increasing ductility and, for rubber, frost resistance. Three qualifications apply: steel slag is chemically reactive and potentially expansive, marble is soluble in acid, and e-waste is compositionally variable. Durability evidence remains sparse and heterogeneous in exposure conditions, so it is reported as descriptive evidence with the number of contributing studies stated. Substituting coarse aggregate alone alters cradle-to-gate CO₂ by approximately − 6% to + 6%, and for recycled coarse aggregate a small increase of 0.3–3.4% has been reported. Reductions of approximately 17% derive from partial clinker substitution rather than from aggregate replacement.