Investigation and Improvement of Bond Performance of Synthetic Macro-Fibres in Concrete.

Mantas Garnevičius,Pui-Lam Ng,Viktor Gribniak,Shaohua Chu,Linas Plioplys

doi:10.3390/ma13245688

Abstract

Strength and stiffness are the key parameters characterising the bond performance of fibres in concrete. However, a straightforward procedure for estimating the bond parameters of a synthetic macro-fibre does not exist. This study employs pull-out tests to investigate the bond behaviour of synthetic macro-fibres. Two types of macro-fibres available in the market were investigated. A gripping system was developed to protect the fibres from local damage. The experimental campaign consisted of two stages. At the first stage, 32 concrete specimens were manufactured for performing 96 pull-out tests (three fibre samples were embedded in each cube perpendicular to the top surface and two sides). Two types of macro-fibres with either 10 or 20 mm embedment length were tested. The obtained load–displacement diagrams from pull-out tests demonstrate that the bond performance (characterised by the strength and deformation modulus) of the “top” fibres is almost 20% weaker than fibres positioned to the side surfaces. At the second stage, one type of macro-fibre was chosen for further experimentation of the feasibility of improving the bond performance through the use of colloidal silica or steel micro-fibres. This investigation stage employed an additional 36 concrete specimens. The use of steel micro-fibres was found to be an efficient alternative. The success of this solution requires a suitable proportioning of the concrete.

Highlights

In contrast to bar reinforcement, fibres offer good potential to serve as dispersed reinforcement in concrete construction in the commonplace
There were two solutions attempted for improving the bond performance of the chosen synthetic macro-fibres
The maximum pull-out force Pmax required to pull out the synthetic fibre increased upon addition of steel micro-fibres

Summary

Introduction

In contrast to bar reinforcement, fibres offer good potential to serve as dispersed reinforcement in concrete construction in the commonplace. Compared to conventional reinforced concrete, fibre-reinforced concrete (FRC) can be superior in terms of crack resistance, ductility, and residual stiffness of the cracked elements [2,3]. The fibres prevent crack proliferation by transferring tensile stresses across the crack to tension along the fibres, as well as to the bond with surrounding concrete [4,5]. This crack bridging mechanism can increase the energy absorption in the post-crack regime and improve the ductility of FRC [6]. The RILEM recommendation [7] considers FRC as a homogeneous substance with modified material properties

Results

Discussion

Conclusion