Aggregate Characteristics Governing Performance of Seal Coat Highway Overlays

Abstract

A study was undertaken to identify the engineering properties of aggregates that explain the variability in the frictional performance of seal coat highway overlays. The frictional performance data of 72 test sections and section replicates collected over a period of 8 years were used in the formulation of statistical models that incorporate the significant variables. The effects of traffic, construction, and environmental variables were also considered. Formulated models were of two types: general and individual. The former type attempts to describe frictional performance using the observations collected on all aggregate materials used. The latter describes the performance of individual aggregate groups. Laboratory properties found to be significant included the polish value, impact and abrasion, and soundness properties. The coating of aggregate particles, gradation, and construction placing rates of aggregate and asphalt were also shown to be significant in explaining performance variability. The influence of traffic and region was found to be interactive with the type and properties of aggregates. The formulated models can be used as a tool for predicting the frictional performance of seal coat aggregates, thus providing a better means for the proper selection of aggregates and for the planning of future seal coat construction projects.