Cost-Comparison Methodology for Selecting Appropriate Asphalt Concrete Mixes

Abstract

The Virginia Department of Transportation's (VDOT's) Road and Bridge Specifications combine with various special provisions to cover more than 13 asphalt concrete surface mix designations. Although the specifications offer recommendations about the types of mixes that should be programmed for a given set of facility characteristics, local conditions and experiences heavily influence the predominantly selected mix. As material prices continue to climb without budgets doing the same, local circumstances are more often going to contribute to the selection of the less expensive mixes, especially as long as managers lack a defensible rationale for specifying a more expensive option. This paper describes an economic analysis procedure designed to help engineers and managers select the most cost-effective mix. This procedure includes a methodology for estimating the expected service life for each mix, which is developed by using the systemwide condition ratings for all of Virginia's Interstate and state primary roads. Through the use of examples with typical project families, the research demonstrates that premium prices for stone matrix asphalt can generally be justified by better performance. In one illustration that uses actual condition and awarded price data, a life cycle cost analysis revealed that the use of stone matrix asphalt in lieu of dense-graded mixtures on Interstates might save VDOT more than $7,500 per lane mile in net-present-value costs.