Influence of Matrix Strength on the Pullout Behavior of High Strength Steel Fibers

Abstract

This study investigates the effects of matrix strength on the pullout behavior of steel fibers by performing single pullout test. Two types of high strength steel fibers, smooth and twisted fiber, were embedded in three different concrete matrices with compressive strengths of 28 MPa (normal concrete), 84 MPa (high-strength concrete), and 180 MPa (ultra-high-strength concrete). The results showed that twisted fibers embedded in both normal concrete and high-strength concrete produced slip hardening behavior while smooth fiber in all concrete matrices generated slip softening behavior. As the matrix strength increased, the pullout resistance of fibers increased if they could maintain pullout mode. However, the pullout resistance of twisted fiber in ultra-high-strength concrete deteriorated immediately after the fiber was broken. Twisted fibers produced higher pullout resistance in normal and high-strength concrete but lower pullout resistance in ultra-high-strength concrete than smooth fibers. Twisted fiber showed the best performance in high-strength concrete whereas smooth fiber did in ultra-high-strength concrete.