Reinforced concrete beams retrofitted with UHPC or CFRP

This study explores the reinforced concrete beams retrofitted with ultra-high-performance concrete (UHPC) or carbon fiber-reinforced polymer (CFRP). The main test items and methodologies are as follows: (i) Use basic mechanical tests to evaluate the feasibility of UHPC as a strengthening material. (ii) Probe into the retrofit effect of making small-sized reinforced concrete beams and using UHPC or CFRP. The results of the study show that Poisson's ratio of UHPC to ordinary concrete is between 0.19 and 0.21, which is suitable for cement mortar or concrete repair and has good compatibility. Using UHPC or CFRP to retrofit reinforced concrete beam members, the ultimate load increases by 35% and 56.6%, respectively. However, the displacement of CFRP is only increased by 4 mm, while the displacement can be increased by 26.8 mm after UHPC (2% steel fiber) retrofit. The unit price of a reinforced concrete beam strengthened with CFRP is 2–4 times higher than that of a UHPC retrofit. Therefore, UHPC has better toughness, displacement, and fracture energy than CFRP retrofit. The UHPC is suitable for the strengthening and economic benefit of reinforced concrete structures.