Pullout behavior of recycled macro fibers embedded in ultra-high performance seawater sea-sand concrete

Recently, an eco-friendly ultra-high performance seawater sea-sand concrete (UHPSSC) has been developed using the recycled macro fiber (REF) processed from waste wind turbines, which is more suitable in remote islands and can address the corrosion issue of concrete structures with steel reinforcements. The interface bond of the UHPSSC/macro fiber is lack of investigation and a significant factor influencing the tensile characteristics of macro fiber reinforced UHPSSC. In the present study, the pullout test of the single macro fiber was conducted to investigate the bond behavior of such interface. The test variables included the macro fiber width (4, 6, and 8 mm), the embedded length (5, 10, and 15 mm), and the type of matrix. Then, the local bond-slip relationship at the fiber/UHPSSC interface was obtained by finite element analysis (FEA) to provide a more precise display of interface bond mechanisms. The results revealed that the bond of UHPSSC/macro fiber was stronger with increased fiber embedded length and width due to the greater frictional interactions and better overall integrity of fibers. Additionally, the FEA method proposed here to obtain the local bond-slip relationship was reliable and effective. This study could serve as a basis for further research on the tensile properties of UHPSSC reinforced with macro fibers.