Bond Performance of Hook-End Steel Fiber to the Mortars Cured for 360 Days

Abstract

The reliable bond of steel fibers to concrete matrix is fundamental to ensure they work together under internal and external actions throughout their service life. Due to the lack of research on the long-term bond property, this paper conducted an experimental study on the bond of hook-end steel fiber in the manufactured sand mortars with different water to binder ratios cured for different ages from 7 days to 360 days. The characteristic pull-out load-slip curves are measured, and bond performance indexes at different curing ages are analyzed by using the multi-index synthetical evaluation method. The results show that the bond strengths, the fiber strength use efficiency, the debonding work and the pull-out work increased with the increase in curing age up to to 90 days, which became stable with little variation with the follow-up curing age. The variations are closely associated with the development of mortar strength. Steel fibers embedded in high-strength mortar presented a higher debonding ductility and a lower slipping ductility. In addition, the prediction formulas of long-term debonding strength, bond strength and residual bond strength are proposed.