Confinement effects on bond strength of deformed reinforcement in early-age concrete

Abstract

The stress state in concrete around deformed reinforcements has a significant influence on the coordinated performance between the deformed reinforcement and concrete. Although the bond strength of deformed reinforcements embedded in mature concrete has been well studied, there is still a lack of research on the bond strength of deformed reinforcement in early-age concrete under lateral pressures. In this paper, 180 pullout specimens were designed to reveal the effect of age and lateral pressure on bond strength, and a theoretical analysis model for predicting bond strength was also presented. Test results showed that the bond failure modes were closely related to the lateral pressures, relative cover thickness of concrete, and early-age concrete strength. The bond strength increased following the curing age but was negatively (positively) influenced by the unilateral (bilateral) pressures. Based on the test results, a regression model for predicting the bond strength of the deformed reinforcement in early-age concrete under lateral pressures was proposed. Furthermore, an analysis model based on the partly cracked theory was extended for predicting the bond strength of the deformed reinforcement in early-age concrete considering the lateral pressures and fitted the experimental results quite well.