Experimental and numerical investigation on bond between steel rebar and high-strength Strain-Hardening Cementitious Composite (SHCC) under direct tension

Abstract

Sufficient bonding between Strain-Hardening Cementitious Composites (SHCC) and steel rebars is required to guarantee the stress transfer in structural applications. Although the bond between medium-strength SHCC and rebars has been extensively studied, the present understanding of this property for high-strength SHCC is very limited. Moreover, the previous pullout or bending test methods have some limitations. This study investigates the bond between deformed steel rebars and high-strength SHCC with a new direct tension approach, which is able to determine the fundamental interfacial stress versus displacement relation under pure tension. The effects of concrete block material and cover thickness, rebar diameter and embedment length, as well as confinement condition on the bond behavior were experimentally evaluated. The test results showed that high-strength SHCC can bond much better with deformed steel rebars than ordinary concrete and high-strength SHCC matrix (without fibers) due to the well-controlled splitting cracks, and that the geometry has certain influences on the bond strength. A simple but reasonably accurate finite element model for engineering applications was also proposed to analyze the bond behavior in structural components. In this model, all the non-linear behaviors were integrated into rebar/SHCC interfacial elements, so that the complicated steel surface geometry and/or the local splitting of concrete do not need to be explicitly modelled. Through a coupled experimental-numerical approach, the bond stress-displacement relationship was extracted from a small number of test results. The derived relationship was then employed for the prediction of additional test results, with good agreement achieved. With its general applicability demonstrated, the proposed numerical approach can facilitate the design of reinforced SHCC elements and structures.