OVERLAY TEST TRACK SHARONVILLE, OHIO. REPORT OF CONSTRUCTION (SHARONVILLE NO. I).
OHIO RIVER DIV LABS CINCINNATI
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The U. S. Air Force increased its heavy load criteria to include a loading of 100,000 lbs on twin 56 x 16-in. wheels, with a tire contact area of 267 square in. per wheel. Since the thenexisting criteria for flexible overlay design did not cover the increased loading, it became necessary to extrapolate beyond the limits of the design charts hence the decision was made to build a new test track to validate the extrapolation. A low-bearing-value subgrade was chosen, and a test track 1040 ft long and 50 ft wide was subsequently built. The test track contains 16 different items for traffic testing, 2 maneuver areas, and 15 transition areas. Fourteen items have flexible overlays, 2 items have no overlay. All items have rigid base pavements varying from 6 to 10 inches in thickness. Black base, A. C. asphaltic concrete binder, and A. C. surface course comprise most of the overlays 3 items have waterbound macadam in place of the black base. The construction of this test track produced many complex problems in that it was the first attempt to construct an overlay to exact requirements. The smallness of the project required extreme care in quantities of material to be used. Design procedures were in the process of being developed, and valuable expreience was obtained in completing the project. All values were measured and recored for use in analyzing the results of traffic testing at a future date. Author