A comparative study on the bond performance between rebar and structural lightweight pumice concrete with/without admixture

Abstract

In this study, the bond strength between concrete and steel reinforcement of structural concrete produced by lightweight pumice aggregate (SLWAC) and normal-weight aggregate (NWAC) is investigated. To achieve this objective, 12 different types of concrete mixtures were produced. In producing the NWAC and SLWAC mixtures, a mineral additive, silica fume (SF), was used to replace the Portland cement in the ratios of 0, 5 and 10% by weight. The remaining six types of mixtures were obtained by adding super plasticizers (SP) to the earlier mentioned mixtures in the ratio of 2% by weight. In conclusion, unit weight of SLWAC was 23% lower than that of NWAC. When compared with NWAC, compressive strength reductions in SLWAC were observed to change between 48 and 65%. Use of SF and SP together, increased the bonding between concrete and the steel reinforcement in both SLWAC and NWAC. The bond strength of deformed bars in SLWAC was lower when compared with those of NWAC. Normalized bond strength of L-5-2 and L-10-2 coded specimens were found to be 1.01 and 1.10 times (with respectively) higher when compared with N-0-0. Other all SLWAC specimens were less than N-0-0 (ranges between 0.92 and 0.96 times). Besides, it was also observed that the slip at peak load for pullout failure of ribbed bar did not vary too much for both NWAC and SLWAC specimens (ranges between 0.7 and 2.5 mm).   Key words: Bond strength, pullout tests, structural lightweight concrete, pumice aggregate, silica fume, superplasticizer.