Experimental study on bond performance at UHPC-UHPC cold joints

Abstract

There has been a rapid increase in the use of ultra-high-performance concrete (UHPC) as a construction or repair material worldwide due to its superior mechanical and durability characteristics. However, the bond strength of UHPC cast at different times is inadequately understood. This study examined the bond performance at UHPC-UHPC interfaces using five different surface preparations with mean texture depths (MTDs) ranging from 0.43 mm to 6.38 mm. The effect of fiber exposure techniques such as pressure washing, sandblasting, and needle scaler treatment on the bond performance at UHPC-UHPC cold joints was considered. The study also included the effect of grooved and smooth surface preparations on bond strength. The bond strength was investigated under tensile, shear and compression-shear stress conditions. The influence of inclination angle of the interface with different shear to compression ratios was studied. The results indicate that the presence of steel fibers at the interface plays a significant role in bond capacity by enhancing the bond strength and providing more interlock that results in ductility. The majority of the failure modes were at the bond interface due to the superior mechanical properties of UHPC. The cohesion and friction coefficients were determined from the experimental data and compared with values from design codes. It was discovered that pressure washed and grooved surface preparations exhibited superior bond performance compared to the other surface preparations under the stress conditions considered in this study.