Minnesota Taconite as a Microwave-Absorbing Road Aggregate Material for Deicing and Pothole Patching Applications

This report presents modeling of temperature profiles for application of microwaves to pothole patching and roadway deicing. Values of key parameters are estimated and presented for asphalt-aggregate composites containing varying magnetite content (compacted and with voids), ice, and water. The key parameters are: microwave absorption coefficient at 2.45 GHz, density, heat capacity, and thermal conductivity. This reports summarizes the work we were able to complete, including a large number of equations characterizing key parameters and an extensive list of references. The natural magnetite in taconite is an outstanding microwave absorber. Consequently, when a truck-mounted microwave generator is driven over an ice-covered roadway constructed with crushed taconite as the aggregate, the microwaves should pass through the ice and be absorbed as heat at the road-ice interface, allowing the ice to be easily detached and scraped away. This energy-efficient process is the only non-chemical method of deicing practical for many miles of roadway. Adoption of this deicing method could lead to a significant demand for taconite aggregate. The same microwave equipment used for deicing could be used yearround for pothole patching applications, with the microwave energy used to generate just the required amount of hot mix on-site for permanent repairs.