Development of statistical wet weather model to evaluate frictional properties at the pavement-tire interface on hot mix asphalt concrete

Abstract

Skid resistance on wet pavements is influenced by friction at the tire-pavement interface as well as overall hot mix asphalt (HMA) performance. It is important to control aggregate, asphalt, and mix properties to achieve desirable frictional properties on HMA during its service life. Aggregate consensus and source properties influence frictional properties at the surface as well as aggregate matrix properties that affect overall skid performance. Thus, it is important to identify and control these properties through an effective testing and monitoring program. Research studies have indicated that current testing protocol for pre-qualification of aggregates being used by DOT's is tenuous and needs definitive evaluation. The validity of some tests currently being used for pre-qualification of aggregates is being questioned due to poor field correlation. Thus, there is a need for upgrading current testing criteria and aggregate classification system in view of new techniques that can be used either as replacements and/or supplements to current tests. This study, a part of the Texas Department of Transportation (TxDOT) current research program to evaluate inadequacies of current tests to skid performance, focuses on tests evaluating aggregate shape and distribution parameters. In this study, a wet weather test selection criteria was developed to evaluate the effectiveness of current and new testing techniques to monitor aggregate shape, texture, and distribution characteristics. Extensive tests were conducted on forty aggregates selected from TxDOT Quality Material Catalogue covering various parts of U.S.A. Fine aggregates tests including the Uncompacted Void Content, the Compacted Aggregate Resistance, the Methylene Blue, and the Particle Size Analysis were performed to evaluate angularity, texture, and distribution characteristics within fine aggregates. Flat and elongated tests on coarse aggregates were also performed using both conventional and automated techniques to analyze shape and size distribution characteristics. A statistical analysis was performed to select tests that would enable monitoring of aggregate shape and distribution properties enhancing skid performance. The evaluation criteria were based upon a sensitivity and correlation analysis to evaluate consistency, reproducibility, and ability of tests to effectively discern aggregates with good and marginal performance.