Laboratory Fatigue and Toughness Evaluation of Fiber-Reinforced Concrete

Abstract

Concrete pavement design is currently centered on steel reinforcement: whether in the form of dowel bars, as in jointed plain concrete pavement, or in the form of continuous rebar reinforcement, as in continuously reinforced concrete pavement. The use of steel in concrete pavements presents durability problems because of the corrodibility of steel. This study evaluated the use of polypropylene fibrillated fibers, polypropylene macrofibers, and carbon fibers as primary reinforcement in concrete pavements for the Louisiana Department of Transportation and Development. Results showed that fiber reinforcement can be used to improve both the fatigue and toughness performance of concrete. When post-cracked strength or toughness was the concern, concrete containing more fibers and fibers with a high tensile strength was desirable. Carbon fibers maintained greater load-carrying capacity at lower deflections than did the steel fibers, which produced the greatest ductility. However, toughness and fatigue performance did not correlate for small deflections; this result suggests that polypropylene macrofibers may be adequate for repeated, low-stress loading. This study also found that when repeated low deflections were a concern, such as with pavements, there had to be sufficient fibers across a crack to maintain a tight crack. Conversely, too many fibers prevented adequate consolidation and aggregate interlock and negatively influenced performance. The resultant pavement design, continuously fiber-reinforced concrete pavement, will provide an alternative to jointed plain concrete pavement and continuously reinforced concrete pavement in highway pavement design that is not susceptible to durability problems associated with corrosion of reinforcement.