This paper describes the plans for development of performance-based specifications for asphalt binders and asphalt-aggregate mixes, which is the principal goal of the SHRP asphalt research programme. These specifications will allow the engineer to select an asphalt binder and asphalt-aggregate mixture on the basis of the performance level required of the pavement under the present and predicted traffic and evironmental conditions. The performance-based specification for asphalt-aggregate mixes will require methods or protocols for the following: 1) mixing and compaction of laboratory specimens that realistically simulate the effects of plant mixing and field compactions; 2) selection and proportioning of materials to obtain a job mix formula that provides the required pavement performance level in view of the expected environmental conditions and traffic volume; and 3) evaluation of modifiers or modification techniques if it is determined that unmodified mixes cannot meet the performance demands. The preceding represents an asphalt-aggregate mix analysis system (AAMAS) that, when used in conjunction with the performance-based specifications and accelerated test methods, allow a rational selection of materials for mix compatible over a wide range of temperatures which is resistant to permanent deformation, fatigue and thermal cracking, aging and moisture damage. Initially, SHRP will use some of the AAMAS concepts identified NCHRP Report No. 338 and build upon these as SHRP research findings support inclusion of more profound technical advancements related to materials selection; specimen size, configuration, compaction and conditioning; and supportive tests. In its current format the AAMAS logically proceeds with consideration of the following asphalt selection: asphalt-aggregate compatibility; initial proportioning and trial mix design; specimen fabrication, volumetric analysis; evaluation of fundamental engineering properties; and comparison to structural design requirements.
Abstract