Using Geosynthetics in Overlays to Minimize Reflection Cracking (0-1777-S)

One of the more serious problems associated with the use of thin overlays is reflective cracking. This phenomenon is commonly defined as the propagation of cracks from the movement of the underlying pavement or base course into and through the new overlay as a result of load-induced and/or temperature-induced stresses. Some of the latest techniques for reducing the severity and/or delaying the appearance of reflective cracking include incorporating geosynthetic products into the pavement structure. Geosynthetics are defined herein as grids, fabrics, or composites. This procedure is typically accomplished by attaching the geosynthetic to the existing pavement (flexible or rigid) with an asphalt tack coat and then overlaying with a specified thickness of hot mix asphalt (HMA) pavement. These materials have exhibited varying degrees of success, and their use within a particular agency has been based primarily on local experience or a willingness to try a product that appears to have merit. Several geosynthetic products on the market claim to reduce the severity or delay the appearance of reflective cracking in HMA overlays due to stresses induced by the environment and traffic. The objective of this research was to investigate the state of the art and develop information that will aid in the evaluation of the relative effectiveness of commercially available geosynthetic materials. Specific objectives of this research include: . Review published and unpublished information, and synthesize the findings. . Obtain geosynthetic products representing the different categories of materials marketed for reducing reflection cracking in HMA overlays. . Fabricate HMA beams reinforced with geosynthetic materials, and measure their relative resistance to thermally induced stresses. . Identify and utilize the best available model to analyze the laboratory data, and . determine the material properties that have the greatest effect on overlay performance. . Plan and construct test pavements to evaluate relative resistance to reflective cracking of various geosynthetics. . Determine the relative effectiveness of each category of geosynthetic products in reducing reflective cracking.