Taconite As a Lower-Cost, Alternative High-Friction Surface Treatment to Calcined Bauxite for Low Volume Roads in Minnesota

This four+ year 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)-type applications. Six pavement test sections approximately 1/10th of a mile (160 meters) in length were established 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 GSB (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 (DFT) and a British Pendulum (BP) Skid Resistance tester, while the Minnesota Department of Transportation's (MnDOT's) locked-wheel pavement friction tester (LWPFT) was used a minimum of once a year. Supplemental laboratory and environmental testing and a life cycle assessment (LCA) of HFST systems utilizing taconite and bauxite aggregate were also performed, as was a demonstration of SCRIM (Sideway-force Coefficient Routine Investigation Machine) technology. Taconite and calcined bauxite HFST test sections produced the highest friction numbers, about 40 to 50% higher than the chipseal control. Taconite's friction numbers averaged 6% lower than calcined bauxite's and exhibited virtually no divergence from calcined bauxite's friction numbers over time. Collectively, project findings suggest that taconite aggregate can provide comparable friction performance to calcined bauxite, at a significantly smaller environmental footprint.