Influence of interfacial microstructure on pullout behavior and failure mechanism of steel fibers embedded in cement-based materials

Abstract

In this study, the failure mechanism of the fiber–matrix interface during pullout and the effective improvement of the pullout resistance were investigated. The interfacial bond properties of fibers from cement-based materials were systematically analyzed and compared using various modification methods, and the corresponding fiber–matrix interfacial microstructure was examined through quantitative characterization. Fiber pullout tests were performed to determine the bond properties, and backscattered electron (BSE) image analysis and microhardness tests were conducted for quantitative microstructure characterization. The surface morphology of the fibers after pulling out was assessed by scanning electron microscopy. The results showed that the different modification methods had different improvement effects on different microzones and pullout curve sections. The failure surface moved and tended to the weakest zone in the fiber–matrix interfacial microstructure. The modification methods should be applied carefully to ensure that the improvements to different microzones match, instead of simply increasing the degree of a modification method. A functional relationship between the porosity determined using BSE image analysis (BSE-IA) and the interfacial bond properties was established to correlate the fiber–matrix interfacial microstructure and fiber pullout behavior.