Hot Mix Asphalt Mixtures For Nevadas Intersections

The state of Nevada is experiencing permanent deformation problems with hot mix asphalt pavements at or near intersections. The Nevada Department of Transportation (NDOT) is currently using a Type 2C dense graded mixture in most of its construction. The NDOT Type 2C mixture showed excellent rutting resistance under normal highway traffic, while its resistance to rutting and shoving at intersections in the hot environment of Las Vegas is questionable.The overall objective of this research was to identify a hot mix asphalt (HMA) mixture with good resistance to rutting and shoving at intersections. To this end, two laboratory evaluations were conducted: I. Postmortem evaluation of in-service intersections and II. Laboratory evaluation of different aggregate gradations. Based on past performance and data generated from this research, five different aggregate gradations were selected for laboratory evaluation. Aggregates were sampled from the Sloan quarry located south of Las Vegas, Nevada, along Interstate 15. All five gradations were mixed with a polymer-modified PG76-22NV asphalt binder which is the current specified asphalt grade for southern Nevada. A Hveem mix design was conducted for each of the five mixtures. This part of the research re-evaluated the APA and RSCH as potential candidates for a mix design test for intersection mixtures. In addition, the triaxial compression strength test and the repeated load triaxial test (RLT) were also evaluated. All tests ranked the permanent deformation resistance of the five mixtures in the same order. Additionally, dynamic mechanistic analyses were performed as an attempt to determine the pavement responses under a heavy loaded truck at and away from the intersection. The findings of the mechanistic analyses were used to predict permanent deformation potential in the HMA layer. To this end, permanent deformation models for NDOT Type 2C mixture were developed in the laboratory using the repeated load triaxial (RLT) and the repeated shear at constant height (RSCH) testing. he actual specifications used by NDOT for the various permanent deformation tests were reviewed and adjusted for the HMA mixtures that are going to be used at intersections and stopping areas. (Abstract shortened by UMI.)