Effect of sand grain size and sand-to-cement ratio on the interfacial bond strength of steel fibers embedded in mortars

This research investigated the effects of sand grain size and sand-to-cement ratio on the properties of the interfacial transition zone (ITZ) between mortars and high-strength deformed steel fibers. Three grades of sands and two matrix compositions were used, and single fiber tests were performed to study the interfacial bond strengths. Scanning electron microscope back-scattered electron analysis and nano-indentation tests were also used to investigate the microstructure and hardness of the ITZ of the samples. It was found that finer sands and a higher sand-to-cement ratio produced stronger interfacial bonds, although the strength also varied with the type of fiber.