Premature rutting of road pavements constructed for hauling coaland logs is common. Although these roads carry low volumes of traffic, they are subjected to heavy and channelized wheel loads. Unfortunately, conventional asphalt mixes containing aggregates less than 1-in. Maximum size in the base or binder course tend to develop premature rutting under these conditions. Many asphalt technologists believe that the use of large-size stone (maximum size of more than 1 in.) Will minimize or eliminate this problem. Large-stone mixes are also economical for low-volume roads because of substantially reduced asphalt contents. However, most agencies use the marshall design procedure (astm d1559), which uses a 4-in.-Diameter compaction mold intended for mixes containing aggregate up to 1-in. Maximum size only.This has inhibited the use of large-stone mixes. A standard method for preparing and testing 6-in.-Diameter specimens has been presented. Mixes containing aggregate up to 2-in. Maximum nominal size can be tested. A typical mix design using 6-in. Specimens for a coal-haulroad in kentucky is given. Construction data and experience gained from field projects in kentucky are also included. The proposed testmethod may be useful in determining the optimum asphalt content of large-stone asphalt mixes that are recommended for use on low-volumeroads subjected to heavy and channelized wheel loads. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 2.
Abstract