Evaluation of Fatigue and Toughness of Fiber Reinforced Concrete as a New Highway Pavement Design

Abstract

Concrete pavement design is currently centered on steel reinforcement. Whether that reinforcement be in the form of dowel bars, as is the case in jointed plain concrete pavement (JPCP), or in the form of continuous rebar reinforcement, continuously reinforced concrete pavement (CRCP). The use of steel in concrete pavements presents durability problems due to the corrodibility of steel. This study evaluates the use of polypropylene fibrillated, polypropylene macro, and carbon fiber fibers as primary reinforcement in concrete pavements for the Louisiana DOT. Results showed that fiber reinforcement can be used to improve both the fatigue and toughness performance of concrete. When post-cracked strength or toughness is the concern, concrete containing more fibers and fibers with higher tensile strength are desirable. Carbon fibers maintained greater load-carrying capacity at lower deflections than the steel fibers, which produced the greatest ductility. However, toughness and fatigue performance did not correlate for small deflections, suggesting that polypropylene macro fibers may be adequate for repeated, low stress loading. This study also found that when repeated low deflections are a concern, such as with pavements, there must be sufficient fibers across a crack to maintain a tight crack. Conversely, too many fibers prevent adequate consolidation and aggregate interlock, which negatively influences performance. When considering the pre-cracked fatigue performance of fiber reinforcement, the fibers needed to have sufficient length to reach across the crack and bond with the concrete, and that higher fiber dosages increase the fatigue performance of the concrete. The resulting pavement design, continuously fiber reinforced concrete pavement (CFRCP), will provide an alternative to JPCP and CRCP in highway pavement design that is not susceptible to durability problems associated with corrosion of the reinforcement.