Effect of steel fiber addition and aspect ratio on bond strength of cold-bonded fly ash lightweight aggregate concretes

In this study, the adherence between reinforcing steel bar and the cold bonded fly ash lightweight aggregate concretes (LWAC) with and without steel fiber were evaluated by means of bond strength test. The concretes dealt with this study were produced by two different cold bonding fly ash lightweight coarse aggregate contents. The LWAC with constant water-to-cement ratio of 0.4 and 400 kg/m3 cement content were designed. Three types of hooked-end steel fibers with the aspect ratios of 55, 65, and 80 were utilized with four different volume fractions of 0.35%, 0.70%, 1.00%, and 1.50% of concrete volume. The effectiveness of aspect ratio, steel fiber volume fraction, and lightweight aggregate content on the bond strength were investigated at the end of 28-days of water curing. Analyses of variance on the experimental data were performed and the levels of the significance of the lightweight aggregate content, steel fiber aspect ratio and volume fraction on the bond strength of the concretes were evaluated through general linear model analysis of variance (GLM-ANOVA). Furthermore, a mathematical model was proposed for predicting the bond strength of the concretes dealt with the current study. The results revealed that utilization of steel fiber enhanced the bond strength and the ductility of pull-out failure. Moreover, the bond strength was significantly affected by the artificial fly ash lightweight aggregate content.