Predicting tensile properties of strain-hardening concretes containing hybrid fibers from single fiber pullout resistance

Abstract

Tensile properties of strain-hardening fiber-reinforced concrete are the key engineering parameters in determining bending resistance of the material. In this paper, an analytical model to predict tensile properties of ultra-high-performance fiber-reinforced concrete (UHPFRC), a type of strain-hardening fiber-reinforced concretes, was performed based on single fiber pullout test. The studied UHPFRCs contained hybrid fiber system, including macro steel fiber combined with micro steel fiber. Three types of macro steel fibers were used, including long smooth fiber (LS), hooked A fiber (HA), and hooked B fiber (HB); they had different lengths and geometries but same volume content (1.0 %). The only short smooth fiber (SS), one type of micro steel fiber,was employed with various volume content (0.5 %, 1.0 %, 1.5 %). The experimental data from the fiber pullout tests in the available references were used to predict the first crack/post crack strength and cracking parameters of UHPFRCs with hybrid fibers. The predictive equations for strengths and crack resistance of UHPFRC containing hybrid fibers were proposed with modified coefficients.