Taconite Aggregate as an Enhanced Friction Surface Treatment Alternative

A 4-year-plus project (2020–2025) assessed whether friction aggregate produced from a byproduct generated by Minnesota’s taconite (iron ore) mining industry can provide adequate or comparable skid resistance performance to calcined bauxite in high friction surface treatment (HFST) applications. Six pavement test sections, each approximately 0.1 mi (160 m) long, were installed at a low volume road location northwest of Duluth, Minnesota. Two epoxy-based HFST-equivalent test sections using taconite and calcined bauxite aggregate were the project’s focus. Three test sections of gilsonite-based pavement preservation surface treatments, utilizing a slightly finer gradation of taconite friction aggregate, were also installed, while a section of existing chipseal pavement acted as the control. Friction properties were measured twice a year using a dynamic friction tester and a British Pendulum tester, while the Minnesota Department of Transportation’s locked wheel pavement friction tester was used a minimum of once a year. Laboratory and environmental testing, and a life cycle assessment of HFST systems, utilizing taconite and bauxite aggregate, were also performed. Friction properties were also measured as a demonstration of Sideway-Force Coefficient Routine Investigation Machine technology. Taconite and calcined bauxite HFST test sections produced the highest friction numbers, about 35%–50% higher than the chipseal control. Taconite’s friction numbers were within 6% of calcined bauxite’s, exhibiting virtually no divergence from calcined bauxite’s friction numbers over time. Collectively, this project’s findings suggest that taconite aggregate can provide comparable friction performance to calcined bauxite at a significantly smaller environmental footprint.