Role of casting position on bond strength of confined tension lap splices in silica fume concrete

Research reported in the literature on the effect of silica fume on bond-slip characteristics of deformed bars in high performance concrete, indicates that the presence of silica fume as a replacement of part of the cement reduces the bond strength and induces a brittle mode of failure. Recently, Hamad investigated the effect of transverse reinforcement on the bond-slip behavior of tension lap splices in silica fume concrete. He recommended transverse reinforcement in order to increase the bond strength and improve the ductility of the mode of failure. The main objective of the research program presented here was to check whether the earlier recommendation was applicable regardless of casting position, top or bottom. Twelve top cast beam specimens were tested. The beams were designed in a way that the bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. The variables used were the percentage replacement by mass of cement by silica fume and the amount of confinement over the splice region. The trends of the test results were very similar to the trends of bottom cast specimens, identical except for the casting position, which were tested and analyzed earlier.