Effect of dosage and type of mineral admixtures on bond of reinforcing bars in self-compacting concrete

The primary aim of this study was to investigate the effect of dosage and type of mineral admixtures on bond of reinforcing bars in self-compacting concrete (SCC). In this study, twenty seven beams, which were produced from normal concrete and SCC and had 200×300×2000 dimensions were tested. Each beam was designed to include two bars in tension, spliced at the center of the span. The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. During experiments, the class of mineral admixtures (fly ash (FA), silica fume (SF) and dosage (25, 30, 35, 40 %FA and 5, 10, 15, 20 %SF) were the variables as dimensions of beam, diameter of bar and ratio of water to cement and the ratio of water to cement and mineral admixtures (powder) were constant. Three beams for each dosage of mineral admixtures in SCC and control concrete were subjected to positive bending with the splice in a constant moment region. As results, beam specimens with SCC generally showed higher bond strength than beam specimens with control concrete. However, the experimental results showed that the bond strengths of beam specimens with SCC having SF were higher than that of beam specimens with SCC haing FA and beam specimens with control concrete. Key Words: Self-compacting concrete, beams, bond of reinforcing bar-concrete, deformed bar, positive bending, splice length.