Interface shear strength evaluation between different concrete types

Abstract

Composite concrete elements, combining different types of concrete, are widely used in modern infrastructure projects like bridge deck overlays and the reinforcement of existing structures. A critical property for ensuring effective composite action between concrete materials of different ages or types is shear strength, which must be sufficient to prevent excessive slippage or complete separation. This is a fundamental requirement for achieving composite action. This article presents an experimental study on the shear strength at the interface between two different types of concrete, assessed through a push-off test. This investigation stands directly on earlier research focused on the use of high-performance concrete as lost formwork, providing core protection for concrete with recycled aggregates. The study explored the influence of Recycled Aggregate Concrete with aggregates from bricks (RAC) and High-performance Concrete (HPC), with particular attention to the treatment of the concrete interface and the impact of interface roughness and surface treatment. The findings validated the hypothesis that shear strength at smooth, untreated interfaces is considerably lower than that at rough, treated interfaces.