Performance Comparisons of Structural Fibers and Development of a Specification for using Structural Fibers in Thin Concrete Overlays

Project summary:

The application of structural fibers in thin concrete overlays is continuously surging, and a large variety of structural fibers have entered into the market as a result. These fibers improve the structural integrity of concrete by: 1) keeping cracks tight (post-crack performance) and, most importantly, 2) by transferring the wheel load between 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 diameter). 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 corrosion. 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 still unclear whether the structural fibers either in the MnDOT thin concrete overlays or other projects in the country have really contributed. No fiber selection criteria are available to the MnDOT as a result. The prime objective of this proposed project is to conduct a laboratory study comparing the performances of different structural fibers in terms of their contributions in post-crack and load transfer performances. The findings from the laboratory study would then be used for developing a specification/guideline for the selection and application of structural fibers in thin concrete overlays.