Title:
Polymer and Steel Fiber-Reinforced Cementitious Composites under Impact Loading—Part 2: Flexural Toughness
Author(s):
V. Bindiganavile and N. Banthia
Publication:
Materials Journal
Volume:
98
Issue:
1
Appears on pages(s):
17-24
Keywords:
crack; fiber-reinforced concrete; fracture; polymer; test
DOI:
10.14359/10156
Date:
1/1/2001
Abstract:
In Part 1 of this paper, single-fiber pullout tests were described, and the bond-slip responses under impact loading were reported. Four different fiber types, including one straight polyolefin fiber, two lengths of a sinusoidally deformed polypropylene fiber, and a steel fiber with flattened ends, were investigated. It was found that the performance of a fiber depended largely on its failure mode, and in some instances under impact, a change in the fiber pullout mode from a complete pullout to a brittle fiber fracture occurred. If a pullout mode of fiber failure could be maintained for a deformed polymeric fiber, however, its energy dissipation capacity under impact loading could, in fact, approach that of steel fibers. In Part 2 of the paper, results from flexural tests on fiber-reinforced concrete beams carrying the same four types of fibers are reported. Both static and impact flexural tests were conducted. It was observed that regardless of the loading rate, most fibers pulled out across a matrix crack. Among the three polymeric fibers tested, the longer of the two deformed polypropylene fibers was the most promising under both rates of loading. While beams incorporating polymer fibers exhibited an increase in the energy absorption capacity (or toughness) at higher rates of loading, steel fiber-reinforced beams demonstrated a drop in toughness under impact loading. Consequently, although in quantitative terms the steel fiber-reinforced concrete beams absorbed more energy than beams reinforced with polymer fibers at both loading rates, the differences diminished at higher loading rates. This was in agreement with the results of the bond-slip tests reported in Part 1 of this paper, where it was shown that the pronounced visco-elastic nature of polypropylene fibers makes them particularly suitable for impact-type load applications.