Axial compressive behaviour of seawater sea sand concrete composite columns with dual-functional C-FRCM

The seawater sea sand concrete (SSC) composite columns with dual-functional carbon-fabric reinforced cementitious matrix (C-FRCM) were proposed to alleviate the shortage of building materials and enhance the durability of concrete structures. Such novel structure utilizes C-FRCM as both structural strengthening material and as auxiliary anode material for impressed current cathodic protection (ICCP), thereby improving mechanical properties and durability. This paper outlines the manufacturing process of such composite column. Subsequently, seven specimens (two reference SSC columns and five composite columns) were tested to investigate the axial compressive behaviour of composite columns and the impact of ICCP parameters (i.e. current density, duration and charge quantity). The load-bearing capacity, stiffness and ductility of different specimens were compared and analyzed. The results revealed that composite columns exhibited superior load-bearing capacity, stiffness and deformation capacity compared to the reference columns. Increasing the charge quantity led to a more pronounced deterioration in the bonding performance of the C-FRCM interface, and hence a reduced deformation at ultimate load and the corresponding ductility. However, such degradation did not significantly affect the load-bearing capacity. Consistent mechanical properties were observed among composite columns with the same charge quantity, indicating that the degradation of the C-FRCM interface was consistent under the same charge quantity. Finally, based on the design rules given in NACE TM0294, the theoretical service life of the composite columns was estimated. Remarkably, the mechanical performance of the composite columns remained comparable to that of the reference columns even after 52.5 years of long-term operation.