Study of Bond Strength of Plain Surface Wave Type Configuration Rebars with Concrete: A Comparative Study

This study investigates the bond strength behaviour of plain surface wave type configuration (PSWC) rebars in comparison to mild steel (MS) and high yield strength deformed (HYSD)  rebars of varied rib configuration as per BIS and ASTM standards. The variables in the rebar include plain surface, curved surface, parallel rib, diamond rib and Nano modified cement polymer anticorrosive coating (CPAC). Total of 30 pull-out specimens and 12 beam-end specimens were put to a pull-out test following BIS and ASTM standard respectively. The load corresponding to 0.025mm free end (FE) slip and 0.25mm loaded end (LE) slip were carefully observed. The load-deflection behaviour, appearance of the first crack in the specimens and ultimate failure load was recorded. The experimental results showed that as compared to MS rebars, HYSD rebars offer an approximately threefold increase in ultimate bond strength and 1.5 times increase in usable bond strength irrespective of varied rib configuration. PSWC rebars with 4mm offset and 80mm pitch offered 2.4 times increase in ultimate strength and 76.2% increase in usable bond strength as compared to MS rebars. The ultimate pull-out load of PSWC rebars was around 25% and the usable bond strength was only 8.6% lesser than HYSD rebars with parallel ribs. The adopted coating enhanced the corrosion resistance and the reduction in bond strength with any surface configuration was less than the permissible maximum reduction of 20% as specified in IS 13620-1993. Hence it can be concluded that PSWC rebars offered promising bond strength results and upon further optimization and study in other aspects,  PSWC rebars can be a way to replace HYSD rebars in future for enhancing concrete durability at zero added cost.