Recycling of industrial and agricultural wastes as alternative coarse aggregates: A step towards cleaner production of concrete

• Reuse of industrial and agro wastes as alternative coarse aggregates is reviewed. • Influencing factors of sintering and cold-bonding production processes are compared. • Cleaner production of artificial coarse aggregates from waste materials is reported. • Effect of alternative coarse aggregates on properties of concrete is presented. • Future research studies for acceptance of alternative coarse aggregates are stated. Aggregates are mined on a larger scale leading to the depletion of mountains and ecosystem. Cleaner production of artificial stone aggregates from industrial waste is an alternative to natural stone aggregates. Although earlier studies have reported the use of artificial aggregates, a comprehensive review of the performance of alternative aggregates in concrete is highly limited. Therefore, the present review focuses on reusing waste materials from the agricultural and industrial sectors to produce alternative coarse aggregates. The effect of coarse aggregate replacement with agricultural and industrial wastes like furnace slag, oil palm shell, coconut shell, waste ceramic tiles, glass, expanded polystyrene, lightweight expanded clay aggregate, and recycled concrete aggregate on fresh, hardened and durability properties of concrete is reported. Moreover, a critical evaluation of sintered and cold bonded artificial aggregate production processes and their influence on concrete properties is also presented. Recycled concrete aggregates, oil palm shell, and expanded polystyrene resulted in the increased workability whereas, the addition of ceramic waste and steel slag as coarse aggregates reduced the workability of concrete. The workability of concrete depends mainly on the water absorption of alternative aggregates used. Characteristics of artificial coarse aggregates depend on binder type and binder dosage adopted in the production process. The properties of sintered aggregates are governed by sintering temperature. Lower crushing strength of alternative coarse aggregates resulted in a subsequent reduction in the compressive strength with an increase in the replacement level. Reduction in the density of concrete is witnessed in sintered and cold bonded aggregates used concrete.