Evaluating the field performance of asphalt mixtures in the lab.

The National Cooperative Highway Research Program (NCHRP) is developing advanced pavement technology that supports the Federal Highway Administration's (FHWA) mission to achieve long-lived asphalt pavements. This article describes the Simple Performance Tester (SPT), which evaluates asphalt mixtures to determine their response to permanent deformation (rutting) and fatigue cracking. The author reports on tests of the SPT in a field laboratory environment. The author introduces a system referred to as Superpave, which stands for Superior Performing Asphalt Pavements. The Superpave method specified how asphalt could be mixed, designed, and analyzed; however, it proved to be too complex and expensive for use in the field. The SPT builds upon the Superpave method, but is more reliable, practical (smaller in size) and cost-effective. The author also describes the FHWA's mobile asphalt laboratory, the rationale for asphalt performance testing, flexibility in design supported by the SPT, the fabrication of test specimens, the dynamic modulus database, and states using or considering the use of the SPT. One sidebar explains the three components of the SPT: the Dynamic Modulus Test, which outputs a stiffness value for the asphalt pavement mixture; the Repeated Load Test, which simulates driving a heavy vehicle repeatedly over a sample of pavement; and the Static Creep Test, which simulates a heavy vehicle standing on a pavement specimen.