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

Project summary:

Real field data are lacking for a direct comparative performance evaluation of Mesabi (taconite) friction aggregate and calcined bauxite in high-friction surface treatments (HFST) applications. Calcined bauxite has been given a preferred status relative to HFST use by FHWA, but it is imported, expensive, and energy-intensive to produce. A recycled/byproduct alternative like Mesabi HFST aggregate may still provide adequate or comparable field skid-resistance performance and is significantly less energy-intensive to produce. The proposed project will install HFST systems using both aggregate types.

This study is evaluating whether Mesabi friction aggregate can partially or fully replace calcined bauxite in HFST applications by considering appropriate treatment installation alternatives, including but not limited to: various adhesion methods, such as epoxy, asphalt binder, and microsurfacing; varying blends of Mesabi friction aggregate and calcined bauxite including 100% Mesabi friction aggregate and 100% calcined bauxite (for comparison); and appropriate aggregate gradation.

Evaluation criteria includes: the cost to install/maintain, along with a comparison to standard HFST installations using calcined bauxite; skid-resistance test comparisons, monitoring performance, and evaluating wear over time in the field and the lab, including the effect of snow and ice maintenance operations (i.e., snow plowing); locked-wheel skid: https://www.dot.state.mn.us/materials/pvmtdesign/friction.html; dynamic friction tester (DFT) and British pendulum skid-resistance tester; evaluate bond strength of applied surface treatments to underlying pavement; assess/document potential impacts on snow-removal equipment (e.g., abrasion); assess effect of aggregate color on pavement surface temperature and impact on duration of snow and ice coverage; and assess impact of surface treatment on the retention and effectiveness of deicing chemicals.