Shear Bond between Ultra-High Performance Fibre Reinforced Concrete Overlays and Normal Strength Concrete Substrates

Sara Javidmehr,Martin Empelmann

doi:10.3390/su13158229

Abstract

Strengthening or retrofitting of existing structures is a more sustainable and resource-efficient solution than replacing them with new constructions. To enhance the performance and effectiveness of strengthening works the use of high-performance materials is a promising method. Using ultra-high performance fibre reinforced concrete (UHPFRC) as supplementary concrete is one of such solutions leading to high structural resistance and better durability. For such UHPFRC overlays the shear bond resistance of the interface between the existing substrate, usually normal strength concrete (NSC), and the UHPFRC is a significant design aspect. This paper presents the results of push-off tests conducted on NSC-UHPFRC specimens, which were produced with different substrate treatment methods. Using different surface measurement techniques including the sand patch method and digital microscopy, the effects of substrate roughness and treatment method on shear bond behaviour and failure mechanisms are investigated, and the results are analysed with design approaches and further calculation models in the technical literature. Based on the results, the significance of considering roughness parameters and failure mode for the design of high-performance overlays is highlighted. Furthermore, the effectiveness of different substrate treatment methods is discussed and an effective treatment method is suggested.

Highlights

With the growing demand for rehabilitation and strengthening works, the necessity for more efficient and sustainable strengthening strategies expands
This paper presented the results of research parameters, study on normal strength concrete (NSC)-ultra-high performance fibre reinforced concrete (UHPFRC)
Within the conducted push-off tests, the shear bond strength betweensafety the approaches are used with mean concrete tensile strength values and without interfaces with different treatment methods and surface roughness have been determined

Summary

Introduction

With the growing demand for rehabilitation and strengthening works, the necessity for more efficient and sustainable strengthening strategies expands. For concrete floors and decks of, e.g., bridges with deficient bending and shear resistance, the application of a thin, and weight-reduced, layer of ultra-high performance fibre reinforced concrete (UHPFRC), instead of ordinary overlays with the same load-bearing capacity, decreases the dead load of the strengthened structure significantly [1,2,3,4,5,6]. Due to the very compact microstructure of ultra-high performance concrete (UHPC), the toppings or overlays made of UHPFRC slow down the diffusion of corrosive substances plus water absorption and enhance the freeze-thawing resistance and abrasion resistance of structures, so that the overall durability of the structure is enhanced significantly [7,8,9].

Methods

Results

Discussion

Conclusion