Effect of Recycled Aggregates on Physical and Mechanical Performance of Green Concrete Mix

Performance of normally produced concrete is extensively examined both in terms of mechanical and durability point of view using natural aggregates, but due to excessive use of natural resources it is important to use recycled aggregate to reduce not only cost but natural aggregate and environmental pollution. This research study investigates the usage of coarse aggregates from destroyed concrete in new construction and develops strength correction factors for non-standard specimens. Materials used in this study consist of OPC type I, fine aggregate passing from sieve #16 and coarse aggregate of maximum size 25 mm which was obtained from demolished concrete. Performance of recycled aggregate as well as green concrete was examined in terms of compressive, split tensile and flexural strength at 50% replacement of natural aggregate with recycled aggregates. After detailed experimental analysis it is revealed that water absorption capacity increases while decrease in specific gravity was observed compared to conventional coarse aggregates. Recyclable aggregates are used in 50% dosage to prepare green concrete, which has a lower unit weight and density. It was found from test results that recycled aggregates have higher water absorption and lower specific gravity compared to natural coarse aggregates. The unit weight of recycled aggregates concrete (RAC) is 1957 Kg/m³, 11% less than that of concrete with all-natural coarse aggregates (NAC). Tensile strength reductions are more common for RAC cylinders, but the average tensile strength remains within the theoretical range. The study also compares reinforced concrete beams made with natural coarse aggregates and recorded load, deflection, cracks, and cracking patterns at a 5kN load interval until failure.