Bond to reinforcement of polymeric lightweight flowable concrete for structural applications

Limited studies investigated the effect of styrene-butadiene rubber (SBR) latexes on bond properties of structural lightweight self-consolidating concrete (LWSCC). The mixtures tested in this investigation were prepared using expanded kaolinic clay lightweight aggregate (LWA), while the water-to-binder ratio was adjusted to secure compressive strength of 40 ± 3.5 MPa. Testing was realized using the beam-end specimen method, and the parameters under evaluation included the LWA content (up to 40% of coarse aggregate volume), SBR dosage (up to 15% of binder mass), and bar diameter. Test results have shown that the initial stiffness of load vs. slip curves and ultimate bond strength of LWSCC considerably improved with SBR inclusion. This was related to the coupled effect of the SBR polymers that help relaxing stresses during loading and presence of LWA that reduces bleeding and promotes creation of hydration compounds at the steel-concrete transition zone. The experimental data are compared with the design bond strengths determined by CEB-FIP Model Code 2010, ACI 318-14, and European Code EC-2.