The objective of this research is to establish the technical engineering and cost analysis concepts that will enable WisDOT management to objectively evaluate the feasibility of switching construction specification philosophies for aggregate base. In order to accomplish this goal, field and laboratory testing programs were conducted on existing HMA pavements and on base layers under construction as well as comprehensive survey was conducted on highway agencies practices pertaining to base layer construction in the U.S. and Canada. This research proposed construction specifications for aggregate base course layers.

Approximately 10 to 11 million tons of aggregates are utilized in transportation infrastructure projects in Wisconsin annually. The quality of aggregates has a tremendous influence on the performance and durability of roadways and bridges. In this Phase II research study, detailed statistical analyses were performed on over 1,000 sets of historical aggregate test results and the experimental results from the Phase I study. Test results from other states were analyzed as well. Aggregate tests were performed on 12 known marginal or poor Wisconsin aggregates to specifically address test performance of such aggregates. Selected aggregates were scanned using X-ray computed tomography to assess the effects of freeze-thaw and sodium sulfate exposure on the internal void system. The results of multi-parameter logistic regression analyses show that the pass/fail outcomes of the Micro-Deval test can be predicted when LA abrasion, absorption, and sodium sulfate soundness test results are known. The unconfined freeze-thaw test outcomes cannot be predicted from results of other tests (not correlated). Therefore, the unconfined freeze-thaw test should be part of any test protocol as it measures an aggregate characteristic that cannot be obtained from other tests. The percentiles associated with any proposed acceptance threshold limits for various aggregate tests should be determined using the statistical data provided.

The purpose of this manual is to provide clear and helpful information for maintaining gravel roads. Very little technical help is available to small agencies that are responsible for managing these roads. Gravel road maintenance has traditionally been "more of an art than a science" and very few formal standards exist. This manual contains guidelines to help answer the questions that arise concerning gravel road maintenance such as: What is enough surface crown? What is too much? What causes corrugation? The information is as nontechnical as possible without sacrificing clear guidelines and instructions on how to do the job right.