INTERFACIAL BOND STRENGTH BEHAVIOUR OF STEEL FIBRE REINFORCED CONCRETE AND PLAIN CONCRETE SUBSTRATE

Abstract

The quality of the bonded concrete overlay depends on the bonding at the layer’s interface, which is affected by parameters such as fibre inclusion and content in new concrete, moisture condition and surface roughness of old concrete surface. This research presents an experimental study carried-out to assess the interfacial bond strength behaviour of Steel Fibre Reinforced Concrete (SFRC) and Plain Concrete (PC) substrate. The objective of this study is to quantify the interface shear bond strength affected by fibre inclusion and content in new concrete, moisture condition and surface roughness of old concrete surface. Steel wire fibre was incorporated as reinforcing agent in the FRC to determine its effect on bonding strength. To better understand the bonding mechanism at the interface, overlaid square prism specimens were fabricated with three moisture conditions (air dry, SSD, and wet). Five different fibre volume fraction of 0%, 0.5%, 1.0%, 1.5%, and 2.0% were prepared and used as the overlay concrete on three different surface texture (As Cast surface, Grooved surface, and Wire brush surface). It was observed that the bond strength of the FRC samples at all moisture condition (SSD, W and AD) is higher than that of the control specimens in the presence of the three surface texture. The bond strength of FRC with 1% fibre volume was observed to have consequently improved. This improvement is influenced through grooved surface texture at SSD moisture condition of the old concrete surface. Steel fibre of 1.0% produced sample with the highest interfacial bond strength of 15.19N/mm2 . It was observed that, the bond strength of FRC was more than the control specimen. Based on ACI Concrete Repair Guideline, all the roughened surface textures used in this study were able to meet the minimum bond strength it specified. Considering all inferences and appraisals from this research, 1% steel FRC, grooved surface treatment type and SSD surface condition are recommended in the production of retrofitting/repair concretes with the sole aim of achieving an enhanced interfacial shear bond strength.