ABSTRACT
Rehabilitation of damaged roads by incorporating a paving fabric as a crack retarder and water barrier into the new overlay or chipseal has been well established over the past 15 years. Suc cessful use of such systems depends on the quality of the fabric laydown and the compatibility of the individual components. In this context the quality of the paving fabric with respect to the asphalt is essential. During installation the fabric has to meet extreme demands of which the temperature of the asphalt is most critical. Once the paver has passed over the fabric, it can experience temperatures of more than 130°C within a short period before cooling occurs. This is especially true in situations requiring extra hot asphalt [winter, special transportation conditions]. There are clear changes in the fabric’s dimensions when exposed to high tempera ture. These changes are a direct result of shrinkage and the tension created by shrinkage, re ferred to as shrinkage force. Shrinkage values and the development of shrinkage forces are primarily dependent upon the paving fabric’s raw material. Laboratory test have been devel oped to quantify these changes. Testing has been performed on a representative collection of commercially available nonwoven paving fabrics. Irrespective of the raw material, thermally induced changes occurred to all of the tested nonwovens. In contrast to polyester [PES] fab rics, the shrinkage force of polypropylene [PP] fabrics increases dramatically beyond 100°C. Dramatic deformation occurs to PP fabrics at temperatures in the range of 150°C and 160°C, creating distinct shrinkage forces within the fabrics. The unusual shrinkage forces built up in some paving fabrics under certain conditions are considered to be one reason of irregular cracking of fabric rehabilitated road surfaces.
