Comparison of Performances of Structural Fibers and Development of a Specification for using Structural Fibers in Thin Concrete Overlays

The application of structural fibers in thin concrete overlays is continuously surging, and a large variety of structural fibers have entered in to the market as a result. These fibers improve the structural integrity of concrete by (i) keeping cracks/joints tight and (ii) most importantly by transferring the wheel load across the concrete slabs when used in undowelled thin concrete overlays. Structural fibers are presently available in different material compositions, stiffnesses, shapes and aspect ratios (length over effective dia.). Among the various types of fibers, synthetic structural fibers have become predominant in the last two decades due to their ease of handling, better dispersion characteristics and resistance to rust damage. The Minnesota Department of Transportation (MnDOT) has also been using structural synthetic fibers in concrete overlays. However, since no significant research studies were conducted previously to understand the actual contribution of structural fibers, specific to the performance in thin concrete overlays, it is unclear whether the structural fibers either in the MnDOT thin concrete overlays or other projects in the country had really contributed. Strong conclusions are also not possible on the most suitable fiber types and optimum dosages. The prime objective of this proposed project is to conduct a laboratory study comparing the performances of different structural fibers and ranking them in the order of their superiority. The findings from the laboratory study would then be used for developing a specification/guideline for selection and application of structural fibers in thin concrete overlays.