Steel fiber-matrix bond characteristics of cement based composites

The fiber-matrix bond characteristic is one of the most important factors which affect the mechanical properties of various steel fiber reinforced concretes (SFRC). Forasmuch as SFRC resists tensile forces as a composite material by its fiber and matrix phases, the fiber-matrix bond affects force transmission between them. The aim of this research is to investigate some of the factors which affect the steel fiber-matrix bond characteristics by means of pull-out test. Ordinary mortar (OM) and reactive powder concrete (RPC) was used as main matrices. The effect of parameters such as end condition of fiber (smooth or hooked-end), embedment length, water/binder ratio, paste phase of RPC, steel-micro fiber, and curing conditions on fiber-matrix pull-out behavior were determined. The mechanical properties of the mixture were also analyzed. In the second stage, the effect of some chemical admixtures on fiber-matrix bond characteristic of OM and RPC mixtures were investigated. Four polymer based, a corrosion inhibitor, and a waterproofing admixture were used in this stage of study. Additionally, fresh states, mechanical properties, chloride ion patentability, and physical properties of the mixtures were determined. Microstructural analysis was also performed to evaluate the microstructure of fiber-matrix interface of mixtures. Corrosion of steel fiber was also monitored by polarization technique which is widely utilized in the metallurgy and corrosion engineering. Keywords: Pull-out test, bond characteristics, reactive powder concrete, steel fiber