The Next Step Toward End-Result Specifications for Hot-Mix Asphalt Materials and Construction

In 2000, the Virginia Department of Transportation’s (VDOT) Chief Engineer asked the Virginia Transportation Research Council to develop a vision of how and when VDOT would have a working end-result specification for hot-mix asphalt. The response to that question was that it would take several years and many steps to achieve. This report discusses the next step in that ongoing effort, which includes the development and simulated application of two statistical quality assurance (SQA) special provisions, one for asphalt concrete material and the other for asphalt concrete pavement. The criteria for these prototype SQA provisions included the application of standard national terminology and approach, a firm basis in existing VDOT specifications, and quality characteristics that represent the best practical performance measures. This report describes the outcome of a “shadow” application of the proposed SQA specifications to a subset of Virginia’s annual maintenance-resurfacing projects. Although the involved production and placement activities were not subject to the requirements of the SQA specifications, the sampling and testing were designed to represent what would have been required had the special provisions been in effect. The study further determined the likely acceptance outcome for each shadow project and explored future modifications to specification limits and pay adjustment criteria. The most desirable benefit from effective end-result specifications stems from the ability to rededicate available inspection to those key production and placement processes (e.g., joint tacking and surface preparation) that cannot be measured upon delivery to the owner/agency. A less desirable, but more tangible, financial benefit results when these specifications permit a reduction in the overall inspection force. One conservative estimate suggests that VDOT could save more than $2 million per year in inspector salaries through an end-result specification for acceptance of hot-mix asphalt pavements.