Experimental and numerical study on bond strength between conventional concrete and Ultra High-Performance Concrete (UHPC)

Abstract

Ultra High-Performance Concrete (UHPC) has made progress in the bridge and building industry owing to its high strength, ductility, and durability. UHPC is a relatively expensive material and is mostly used in conjunction with conventional concrete. Such composite structures should be designed considering the interaction of different concrete layers. Generally, the simplest interaction model to simulate the complex behavior at the interface is ‘tie’ model, but simulation results may lead to an overestimation of load capacity.This study investigates a more realistic numerical approach comparing to tie interaction model, and its capability to predict the load capacity of structures where substrate concrete is joined to or repaired with an overlay concrete. This modeling technique uses an interface plane between the concrete layers. By calibrating the interface properties, designers can make a reliable prediction about the behavior of the composite structures. The numerical concept is evaluated when UHPC is employed as an overlay and normal strength concrete as substrate section. First, an experimental test program is performed on a series of composite specimens to characterize the bond performance between conventional concrete layers as well as regular concrete and UHPC. To validate the model, third-point loading beam, direct shear, and slant shear tests were performed. The numerical model is then used to evaluate the mechanism of force transfer at the interface between two materials. The results indicate that employing this modeling approach has the capability to provide a better estimation of the failure loads when compared to the tied model.