Interfacial Bond Behavior between Conventional Concrete and Ultra-High Performance Concrete for Structural Strengthening

Abstract

Reinforced concrete structures are currently widely utilized across many countries, with variations in their application depending on specific functional requirements. Strengthening reinforced concrete structures is an effective strategy to extend the service life of buildings. Structural strengthening not only serves to repair deteriorated structures but also enhances the overall performance of both new and existing structures, particularly for load-bearing elements under actual service conditions. Among various strengthening methods, the use of Ultra-high Performance Concrete (UHPC) has emerged as a promising solution. 

This study investigates the bond performance between reinforced concrete beams strengthened with UHPC. Two surface preparation techniques are compared: Concrete Chipping and Epoxy Bonding. Flexural strength tests were conducted according to ASTM C293 on beams measuring 10 cm in width, 50 cm in length, and 10 cm in height under centerpoint loading. Splitting tensile strength tests were performed following ASTM C496, and pull-off strength tests were carried out to evaluate the bond strength between the UHPC overlay and the substrate concrete, using UHPC layers with thicknesses of 2 cm and 5 cm. The results were compared to those of control specimens without UHPC strengthening. The findings indicate that strengthening with UHPC can enhance the flexural performance of reinforced concrete beams by up to 22%.