RELATIONSHIP OF SUPERPAVE GYRATORY COMPACTION PROPERTIES TO HMA RUTTING BEHAVIOR
This report presents the findings of a research project to examine whether there is a relationship between any property of hot mix asphalt (HMA) measurable with the Superpave gyratory compactor and the rutting behavior of HMA pavements in service. Its main finding is that the parameter N-SRmax, the number of gyrations at maximum stress ratio, may be used within certain limits to identify mix designs likely to show gross instability under the shear stresses produced by traffic in HMA pavements. The report will be of particular interest to materials engineers in state highway agencies, as well as to materials suppliers and paving contractor personnel responsible for HMA design and quality control.
Evaluation of Materials From Northeast Texas Using Superpave Mix Design Technology
During 1994 and 1995, asphalt overlay performance problems in the form of disintegration, rutting, and raveling were experienced in the Atlanta District of the Texas Department of Transportation (TxDOT). An investigation of the damage by TxDOT engineers in Atlanta identified the cause as extreme moisture susceptibility of asphalt mixtures containing locally available crushed gravel. A task force was assembled to identify tests and specifications to allow use of local gravel aggregates while, at the same time, precluding future moisture damage problems. The resources of the South Central Superpave Center were mobilized to assess whether Superpave mix design tests and criteria would have identified the mixtures as troublesome in ways other than moisture sensitivity. Because TxDOT already uses a moisture damage test very similar to the Superpave moisture sensitivity evaluation, no Superpave moisture damage tests were conducted. The Superpave mix design evaluation indicated that one or more Superpave aggregate tests, gradation requirements, and volumetric and compaction properties would have precluded use of the materials.
Cooperative Collection Development
The author discusses cooperative collection development from an historical perspective and examines some of the projects conceived and implemented during the past forty years. In many cases the projects failed even after years of concentrated effort. However, more important than these failures are new efforts that are being made. The major focus of this article is on both current regional projects and the more broadly based ARL-sponsored North American Collections Inventory Project. The author discusses these efforts and offers some specific judgments regarding the possibility that these projects will lead to a truly successful coordinated collection development project on a national basis.