ABSTRACT
This chapter presents the experimental results and analytical models available for the bond behavior of deformed bars and prestressing tendons embedded in HPFRCC matrices. The primary variables are: compressive strength of concrete, fiber volume content, fiber type, size of reinforcing bars, type of loading, and presence of confinement. The compressive strength of matrices vary from 4,000 to 12,000 psi (28 to 80 Mpa). The fiber volume content ranges from about 0.3 percent to more than 10 percent for Slurry Infiltrated Fiber Concrete (SIFCON) specimens. In addition, very low fiber volumes of about 0.1 percent were also evaluated for polymeric fibers. Fiber types investigated include: straight and deformed steel fibers and polymeric fibers. The bar sizes varied from 9 to 30 mm (ASTM #3 to #10). The loading consisted of either monotonic or cyclic loading. The results indicate that the presence of fibers improves the ductility to a considerable extent. The fibers were found to provide pseudo confining effects and to be quite important for cyclic loading where large energy absorption capacity is needed to avoid catastrophic failures. At high fiber volume (SIFCON), fibers also increase the bond strength. As far as bond modelling is concerned, both evolutive F.E.-based models and limitanalysis models are recalled, but attention is focused mostly on the latter, which show clearly how the pseudoplastic behavior induced by fibers can improve bond strength, by limiting crack penetration and width in the concrete close to the bar.
