Bituminous mixtures utilizing aggregates falling outside current gradation specifications were used as wearing courses on several low volume county roads in three counties in Minnesota. Evaluation consisted of visual observations, including photographic records, and frictional resistance testing. After five years of service, it appears that the use of finer gradation aggregates will result in satisfactory bituminous wearing courses on low-volume roads.
The new turbulent-mass process for mixing asphaltic concrete paving mixtures has been under study since its recent introduction in 1970. It is increasing in popularity with contractors because of two reasons: the mixing plant requires less equipment; and the process itself appears to result in a significant reduction in polluting emissions. All of this should reduce the cost of production.
Field and laboratory tests and observations indicate that a satisfactory product can be produced by this process, one that is at least equal to conventional plant-mix
Transverse joints were sawed in a deep-strength (12") flexible pavement, which is over a granular subgrade, prior to the opening of the roadway to traffic. This research project was located on the two southbound lanes of Interstate 35 near Stacy. Each of the three test sections is approximately 500 feet long. Joints were sawed at 40, 60 and 100-foot intervals for a total of 30 joints. Two 700-foot control sections, where no joints were sawed, were left between the sawed sections for comparison purposes. After 4-1/2 years or 5 winters of service almost complete crack arresting was accomplished in the test sections where joints were sawed at 40 and 60-foot intervals. A few cracks had formed in the test section where joints were sawed at 100-foot intervals. In contrast, numerous cracks had developed in the control sections.
