Title: Long-Term Behavior of Cracked Steel Fiber-Reinforced Concrete Beams under Sustained Loading

Author(s): Raul L. Zerbino and Bryan E. Barragan

Publication: Materials Journal

Volume: 109

Issue: 2

Appears on pages(s): 215-224

Keywords: cracking; creep; fiber reinforcement; long-term behavior; tensile properties.

DOI: 10.14359/51683708

Date: 3/12/2012

Abstract:
In many cases, fibers are incorporated into concrete to improve the service life of structures by means of the three-dimensional (3-D) crack control capacity of this type of reinforcement. In this sense, the residual (postcracking) capacity and long-term (creep) behavior of fiber-reinforced concrete is of paramount importance. This paper presents an experimental study on the behavior of steel fiber-reinforced concrete (SFRC) beams, cracked and then subjected to long-term loading. Beams measuring 150 x 150 x 600 mm (6 x 6 x 24 in.) were cast with a 45 MPa (6525 psi) compressive strength SFRC with self-consolidating characteristics, having 40 kg/m3 (67 lb/yd3), 0.5% in volume, of hooked-end steel fibers of 50 mm (2 in.) length and 1 mm (0.04 in.) diameter. First, a group of four beams was tested in flexure according to EN 14651 to establish a performance reference. Subsequently, another 18 nominally identical beams were loaded up to crack openings between 0.2 and 3.5 mm (0.008 and 0.14 in.) using the same test configuration to generate different damage levels. The cracked beams were then placed in creep frames and subjected to different levels of load. The crack opening under constant gravity load was electronically measured over a period of approximately 21 months by means of displacement transducers. The concept of the crack-opening rate under long-term loading is introduced, and the conditions for a long-term stable response are discussed.