Push-off and Pull-out Bond Behaviour of CRC Composite Slabs – An Experimental Investigation

Longitudinal shear bond governs the load carrying capacity and performance of profiled steel reinforced composite slabs. Despite testing the load carrying capacity of composite slabs in large-scale size, many researchers have attempted to investigate the shear bond characteristics of composite slabs in small-scale experiments with direct shear load due to its cost effectiveness. With partial replacement of fine aggregate by crumb rubber in conventional concrete (CC), crumb rubber concrete (CRC) has the excellent feature of ductility, which increases the compatibility of deformation with the profiled steel deck and hence is expected to improve bond performance. In this paper, the direct shear test was implemented on small-scale composite specimens using both horizontal push-off and pull-out loads to investigate the bond characteristics between 0.75 mm-thick re-entrant profiled steel deck (Bondek) and CRC/CC with targeted compressive strength of 25 MPa. The push-off specimens were tested with and without clamping force, while pull-out specimens were tested against different sides of the deck embossment. The overall performances of CRC specimens in the elemental tests were very close to CC specimens, with only 5% difference in the ultimate bond strength. CRC material showed reduced vertical separation from the steel deck, which mitigated the longitudinal slippage between the concrete-steel interfaces. Compared to the push-off setup, the pull-out test setup showed overestimation of the bond stress which was explained from FEM model that the higher deformation in ribs and soffit of steel deck was produced. Hence, the pull-out setup is not recommended for determining bond characteristic for future study.