Comparative Study on Natural and Recycled Concrete Aggregate in Sustainable Concrete: A Review

Utilization of recycled concrete aggregates (RCA) as a replacement for natural aggregates in innovative concrete has gained fame around the world as a way to decrease natural aggregate use. The building sector produces a huge amount of concrete waste as a result of the quick rise of population and urbanization over the last 20 years, which not only depletes natural resources but also poses a severe environmental issue. In this framework, recycled concrete aggregates (RCA) made from construction and demolition (C&D) wastes could be a good option because they not only give an alternative to natural aggregates (both fine and coarse), but they also help to reduce landfill space and dispose of C&D wastes. Several investigations have been done to explore how the proportions of the mixture design affect the hardened qualities of concrete made with RCA, but still, some systematic review is required to enhance the performance of RCA. This manuscript presents a comparative study of fresh mechanical and durability properties between normal and recycled concrete by replacing both fine and coarse natural aggregate with recycled concrete aggregates. The analysis has been done by incorporating coarse RCA, fine RCA and both in various proportions to the concrete mix and compared its properties (like workability, compressive strength, tensile strength, flexural strength, and modulus of elasticity) with conventional concrete and the viability of its application in construction industry toward sustainable development. The study shows that the workability of RCA mix was increased from 1.4 to 40% as compared to the normal concrete with 50% replacement. Similarly, replacement level up to 50% fine RCA, the compressive strength was 2.1% more than that of normal mix as compared to the coarse RCA or incorporation of both coarse and fine RCA. But with the increasing of replacement level of RCA, strength gradually decreases. This is credited to higher water absorption of RCA due to attached mortar. However, by addition of suitable chemical and mineral admixtures, the strength of RCA can be enhanced to 20% than the normal concrete.