Effect of exposure to fire on the behavior of recycled aggregate concrete beam with or without reused steel reinforcement

Abstract

To examine the effects of elevated temperature on recycled aggregate concrete as well as recycled aggregate concrete beams made using new and reused steel reinforcement, four concrete mixes with different recycled aggregate replacement ratios (0%, 25%, 50%, 75%) and two types of steel reinforcement (new steel and reused steel reinforcement) were used to cast the beams. Twenty- four cubes and twenty-four beams were tested using a compressive strength test and four-point load test, half of them made with new steel reinforcement and the other half using reused-steel steel reinforcement. Twenty-two beams were subjected to an elevated temperature of (400) °C for (3) hours, while two beams were kept as control beams. While half of the cubes were subjected to an elevated temperature of (400) °C for (3) hours and the others were tested at normal room temperature. It was observed that replacing natural aggregate with recycled aggregate by (25%, 50% &75%) decreased the compressive strength by (8.04%, 16.39%, and 27.9%) respectively without being subjected to elevated temperature and by (4.07%, 20.36%, and 33.31%) respectively after been subjected to elevated temperature. New steel reinforcement beams made of (25%, 50%, and 75%) recycled aggregate had lower ultimate strength by (3.75%, 10.12%, and 27.08%) respectively compared to fully natural aggregate new steel reinforcing beams all subjected to elevated temperature. On the other hand, reused-steel reinforcement beams had lower ultimate strength by (14.25%, 34.76%, and 40.89%) respectively compared to natural aggregate reused-steel reinforcing beams all subjected to elevated temperature