Traditional techniques for preparation of asphalt concrete specimens for the purposes of mixture design, quality control, and research activities in the United States have, for the most part, utilized the Marshall hammer or the California kneading compactor. Recent research has shown that these techniques, particularly the Marshall method, do not simulate field compaction as well as either gyratory shear or rolling wheel compaction techniques. Because gyratory shear and rolling wheel compaction better simulate the field, researchers at Oregon State University (OSU) considered these two alternatives for the preparation of specimens to be used in the water sensitivity work as part of a Strategic Highway Research Program contract conducted at OSU and the University of California at Berkeley. Because of the necessity of fabricating large prismatic (" beam") specimens, the gyratory shear compactor was eliminated from consideration (this compactor can produce only cylindrical specimens). The procedure developed at OSU to produce asphalt concrete specimens utilizing rolling wheel compaction is described. The following were significant findings:(a) rolling wheel compaction is practical for the production of asphalt concrete test specimens in a research laboratory;(b) large numbers of specimens of various geometries can be produced on a daily basis;(c) slab width, length, and thickness are easily varied; and (d) the equipment and procedure can easily accommodate the fabrication of pavement layers such as overlays (eg, open-graded mixture over a dense-graded mixture).

In the United States the laboratory methods most commonly used to prepare asphalt concrete specimens include the Marshall hammer and the Hveem kneading compactor. Developments from NCHRP (J) and the Strategic Highway Research Program (SHRP)(2) have indicated that the laboratory compaction methods that best duplicate the field include the gyratory and the rolling wheel compactor. As a result, SHRP will be recommending that the gyratory or rolling wheel compactor be utilized for mix design for heavy-duty highways. The rolling wheel would be used if beam fatigue tests were to be included in th~ mix design process. This paper describes the rolling wheel compaction process used at Oregon State University (OSU) in conjunction with SHRP Project A-003A entitled" Performance Related Testing and Measuring of Asphalt-Aggregate Interactions and Mixtures." In particular, it presents an overview of the facility and describes the mixing, compaction, and cutting or coring process. Finally, it outlines the costs of the equipment, time and personnel requirements, and perceived advantages and disadvantages of the method.