About the research
The two main objectives of the Phase IV research project can be summarized as follows:
- Extensively instrument and monitor four granular-surfaced roadway sites around Iowa to obtain soil moisture, temperature, matric potential, frost-depth, and thawing period data for a range of Iowa soil types, moisture conditions, and climate conditions.
- Begin developing computational and theoretical models for predicting the depths and durations of freezing and thawing in soils beneath granular-surfaced roadways, and evaluate their forecasting accuracy using NWS data for eventual statewide use without the need for subgrade soil sensors.
The objectives of the proposed Phase III project, which will be completed during the same time frame, are to construct and monitor several more test sections around Iowa using additional stabilization methods employing different types of virgin and recycled materials. The economic and initial versus life-cycle maintenance costs for the different methods will be studied as was done in the Phase II project. It is proposed that four to five additional demonstration sections be constructed in Hamilton County, including one control section.
Similar demonstration sections will then be built in three additional counties distributed around Iowa (a total of 16 to 20 test sections over four counties), to cover a range of different aggregate sources, subgrade soil types, and weather conditions. All demonstration sections will then be tested and monitored through two winter freeze-thaw cycles, and the construction and maintenance costs will be tracked and analyzed as was done in the Phase II project.
The most effective and economical stabilization methods will be identified, and a “How-To” guide will be written for county and district engineers to implement the stabilization methods. Additionally, tests will be performed at several existing macadam-based granular roadways around Iowa, to try to identify the surface-course material properties and subgrade conditions that lead to good long-term performance of non-bitumen macadam bases under granular-surfaced roads.