Shear behaviour of CFRCM-jacketed seawater sea sand concrete beams under an integrated ICCP-SS system

This study investigates the shear behaviour of beam specimens comprising reinforced seawater sea sand concrete (SSC) cores cast with prefabricated U-shaped carbon fabric reinforced cementitious matrix (CFRCM) jackets under integrated impressed current cathodic protection-structural strengthening (ICCP-SS) systems. Six full-scale beams with a shear span ratio of 2.44 were tested under four-point bending, including a reinforced SSC control specimen, an ICCP-only reinforced SSC specimen, an unenergised CFRCM-jacketed specimen, and three energised CFRCM-jacketed specimens subjected to current density of 25, 75, and 125 mA/m2 for 90 days under accelerated corrosion. Digital image correlation (DIC) was employed to monitor the evolution of surface strain fields and crack development. The results indicate that the unenergised CFRCM-jacketed specimen achieved an 11.7% increase in shear strength compared with the control specimen, confirming the intrinsic shear strengthening capability of CFRCM despite partial sectional substitution of the concrete. In contrast, all energised specimens exhibited shear strengths within 2–6% of the control specimen, with only limited variation observed among different current densities. The reduction in shear performance compared with the unenergised specimen is mainly attributed to electrochemically induced interface degradation. A current density of 75 mA/m2 provided effective reinforcement protection while maintaining interface integrity, whereas 125 mA/m2 led to localised CFRCM-concrete delamination despite offering enhanced corrosion control. Finally, existing design codes were further employed to assess the shear strengths of reinforced SSC beams. The results show that current design provisions are generally conservative, with conservatism arising from both the modelling of CFRCM shear contribution and the evaluation of concrete and stirrup shear resistance.