Study of Bituminous Surface Treatments in Virginia: Phase II, Summer, 1964: Distribution Characteristics of Materials, Effectiveness of One Size Aggregate, Setting Time

About the report:

Distribution Characteristics of Materials: Ten bituminous distributors and ten chip spreading operations were investigated the former by cotton pad, cup, and trough tests; the latter by measuring the distance covered by a truckload and by placing pans in the road to catch the stone. A wide variation was found in the coverage consistency of the distributors and the aggregate distribution was found to vary between types of spreaders used. Effectiveness of One Size Aggregates: Seven one size stone test sections were placed on portions of regularly scheduled surface treatment projects. Modified #8 and #78 stones were placed with three different types of chip spreaders and in different combinations with CAE-2, RC-2, AP-00, and RC-3 asphalts. The quantities of stone and binder were determined through a modification of a design method developed by F. M. Hansen of New Zealand. Insufficient time has passed to permit final evaluation of the test sections. Setting Time, or Traffic Readiness: A centrifuge test fashioned after one used in California was used to evaluate lab and field treatments for aggregate whip off. From the results of this empirical test, which is probably much more severe than traffic at moderate speeds, it is believed that AP-00 asphalt is traffic ready in a much shorter period of time than are cutbacks and emulsions. Proposed Investigations: From the work done to date in the surface treatment study it is proposed to: (1) Bring four state asphalt distributors of different makes to Charlottesville for calibration and a later field check against other distributors. Also, it is proposed to train the crews of these distributors in the maintenance, adjustment and operation of their machines. (2) Place eight to ten one size stone test sections on Virginia's highest trafficked roads in the surface treatment schedules, including the Class B and C schedules. (3) Include AP-00 in several of the one size stone test sections and perform further lab work on aggregate retention.

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