Pull-off bond strength of novel wide rounded ends fiber and impact of fiber stretching on fiber/matrix frictional-slip bond strength

Abstract

This paper presents a study about fiber slippage behavior under direct pull-out and assessment of fiber/matrix pull-off bond strength. This study was prepared through theoretical calculations validated by experimental tests. Theoretically, the study shows a general solution for the fiber-slip mechanism in a general matrix using a new frictional-shear-lag model and an analytical model for pull-off bond strength. Experimentally, pull-out tests were conducted for selected types of single fiber in micro-level (glass, carbon, and short-steel fiber); and macro-level (straight steel fiber). The results showed significant improvements in the pull-off bond strength using novel shape of fiber with wide rounded ends-WESF. The pull-off bond strength in normal-weight concrete was found lower than in lightweight concrete, and the matrix with higher compressive strength improves the pull-off bond strength. Also, the steel fiber showed higher pull-off bond strength compared to glass and carbon fiber; whereas the efficiency of short-steel fiber was higher than the long one. All types of fiber showed that the higher aspect ratio reduces the pull-off bond strength. Using the novel-WESF, the performance of fiber-slip improved 52.65% in normal-weight concrete. Moreover, the fiber-slip performance improved 61.79% in sand-lightweight concrete, and 70.20% in all other types of light-weight concrete.