Mechanical Properties of Sprayed FRCC Reinforced RC Beams With/Without Precast Cracks and DIC-Based Crack Identification

Based on the tensile strain hardening characteristics of fiber-reinforced cementitious composites (FRCC), this study experimentally investigated the mechanical properties of reinforced concrete (RC) beams reinforced with FRCC, both with and without precast cracks. The spraying process was applied, and different thicknesses of FRCC reinforcement layers were considered. Additionally, crack identification based on Digital Image Correlation (DIC) technology was employed in the study. The results indicated that as the ratio of the thickness of the FRCC reinforcement layer to the beam height increased, the initial cracking load, yield load, and ultimate load of the RC beams after reinforcement also increased. Moreover, the FRCC layer effectively controlled the development of cracks. When considering the damage to existing RC beams, the application of sprayed FRCC reinforcement improved the ultimate flexural capacity of the beams with precast cracks by over 20%. Specifically, a 30 mm FRCC reinforcement layer restored the flexural capacity of damaged RC beams to more than 85% of their uncracked state. Additionally, the use of DIC technology improved the identification of cracks in images and verified the process of damage and cracking in RC beams. Hence, the utilization of sprayed FRCC as formwork-free reinforcement presents significant value in terms of enhancing durability and mechanical properties.