Bond Behavior of Deformed Bars in Self-Compacting Lightweight Aggregate Concrete at Early Ages

Self-compacting lightweight aggregate concrete (SCLC) has attracted growing attention because of its self-compacting performance and good workability, thus the mechanical properties of SCLC and the structural performances of RC components made of SCLC have been widely studied. However, the bond behavior of deformed bars in SCLC at early ages has not been reported, which has hindered the application of this high-potential concrete. Therefore, in this study, a comprehensive experiment was conducted to investigate the bond behavior of deformed bars in SCLC at early ages, which involved a total of 135 pull-out specimens with different concrete strengths, bar diameters, and curing ages. Based on the experimental results, a criterion is proposed for determining whether the bond failure mode is the pull-out failure or the splitting failure. That is, for a given curing age, when the value of the ratio of the compressive-to-tensile strength is less than or equal to its critical value, which is related to the relative concrete protection thickness and the 28-day compressive strength of SCLC, the pull-out failure occurs, otherwise, the splitting failure occurs. On this basis, the calculation models for the bond parameters including the ultimate and residual bond strength and the slip at the ultimate bond stress, as well as a bond stress-slip constitutive relationship are proposed, which are in reasonable agreement with the experimental results. According to the results of this study, the bond characteristics of deformed bars in SCLC at early ages can be predicted well with only a measurement of the compressive strength of SCLC at 28 days, which are useful in assessing the early load bearing capacity and deformation capacity of the reinforced concrete structures constructed with SCLC.