Many highway agencies in the United States have recently adopted statistically-based, end-result specifications. The acceptance criteria for these specifications are generally based on traditional materials and construction variables such as asphalt content, air voids, and pavement thickness. The acceptance levels (based on deviations from the mean or percent within limit) for most end-result specifications are selected from historical records to penalise those contractors with high levels of variability or large departures from the target value. Because such penalties are not necessarily related to the loss in pavement performance, current end-result specifications may not ensure that the assumed design life is attained. A conceptual framework for performance-related specifications was developed and demonstrated in this study. With a performance-related specification, any loss in payment resulting from contractor nonconformance is directly related to the anticipated loss in pavement life and increase in life-cycle cost. The framework that was developed is based upon a series of algorithms that predict pavement life and life-cycle cost from the appropriate materials and construction variables. Elements of the conceptual framework are discussed and the data needs are described. The use of sensitivity analyses and laboratory studies in the development of a conceptual framework is demonstrated. A computer program, PERSPEC, was developed and demonstrated for an acceptance plan using hypothetical data. An analysis of the results indicated that the framework is implementable and the resulting pay factors are reasonable. Thus, it was concluded that performance-related specifications for hot-mix asphalt are reasonable and can be implemented. Although some of the required elements are not fully developed, current and planned research by the Strategic Highway Research Program, the National Co-operative Highway Research Program, and the Federal Highway Administration should provide the elements needed to fully develop the framework developed in this study. (A)
Abstract