Steel fibre-cement matrix interfacial bond characteristics under flexure

Abstract

This paper presents an experimental investigation into the effect of various parameters, such as fibre embedment length, diameter, spacing and aspect ratio on the interfacial bond between steel fibres and a cement-based mortar matrix. Also, the effect on interfacial bond of the addition of steel fibres or a polymer admixture to the mortar matrix has been investigated. The test method adopted simulates the flexural mode of loading which represents the state of stress most common in practical situations. The results indicate that fibre embedment length and diameter have a very significant influence on both the average interfacial bond stress and the pull-out load per fibre. Generally, the average bond strength increases with increasing fibre embedment length and decreases with increasing fibre diameter. The spacing between fibres has no significant influence on bond strength. Addition of steel fibres or polymer admixtures to the mortar has a significant effect on both the interfacial bond strength and the work done at the interface during debonding. These properties decrease with the addition of steel fibres to the matrix. The introduction of polymer, however, leads to a marginal increase in interfacial bond strength and a more marked improvement in energy absorption during pull-out of fibres.