The effect of fibre chemical treatment on the steel fibre/cementitious matrix interface

This paper aims to study the interfacial bonding between steel fibres and cement-based matrix. The fibres were treated chemically using a zinc phosphate conversion to achieve enhanced bonding with the mortar matrix. In order to gain a better perspective on the effect of chemical treatment different fibre parameters were considered in this research, such as the fibres shape, length and diameter. In this respect, single-sided fibre pullout tests were conducted on treated as well as on as received (untreated) fibres of hooked-end, straight and undulated shape. The analysis of the experimental results revealed that the fibre shape is of great importance since it contributes to mechanical interlocking that prevail during the pullout of the fibres. Chemical treatment was also shown to play an important role on the fibre–matrix interface especially when mechanical interlocking is absent. Treated fibres exhibited a modified surface with a rough topology caused by precipitation of ZnPh crystals on the fibre. Optimum fibre configuration for maximum pullout performance can be chosen based on the fibre surface contact area, since the pullout load and pullout energy is directly related to this property.

► Enhanced bonding was achieved via treatment of steel fibres with ZnPh conversion.
► ZnPh crystals precipitation resulted into a rough surface of the steel fibres.
► ZnPh treatment led to significant increase in pullout energy.
► ZnPh treatment has a prominent effect, when mechanical interlocking is negligible.
► Optimum fibre configuration can be chosen based on the fibre surface contact area.