Cold recycling asphalt pavements is a strategy used by transportation agencies to reduce road construction costs and increase sustainable practices, but engineers often don’t have a complete performance characterization of the recycled material. This can lead to overdesigned pavement structures. This project developed tools and methodologies to better understand the engineering characteristics and capabilities of the recycled materials to ensure the structural integrity and long-term performance of newly constructed roads without costly overdesigns.

To mitigate the deterioration of gravel roads, transportation agencies can apply a chemical stabilizer to improve aggregate cohesion. This project examined the mechanical, environmental and economic performance of five stabilizers and three application methods to determine the best options for reducing gravel road deterioration. Results demonstrated that stabilization reduced gravel loss, maintenance frequency, fuel use and long-term costs. Three of the tested stabilizers performed well, and the blade-mix and direct-injection methods generally performed better than the spray-on surface treatment.

Low slump concrete overlays are an effective way to extend the life of bridge decks, but MnDOT’s current low slump mixture has begun showing extensive cracking after installation, prompting the agency to seek a revised mixture that reduces cracking while still achieving low permeability and a minimum compressive strength of 4,000 psi. MnDOT evaluated a new low slump concrete mixture, both with and without glass fibers, alongside the existing mix, and found that each version of the new mixture provided adequate strength and electrical resistivity. Although the fiber‑reinforced option costs more and requires slightly more finishing effort, it significantly reduces crack sizes by about 50%, improving toughness and potentially extending service life.

Winter road deicers often migrate from roadside soils into sensitive groundwater, prompting this study of how commonly used salts—and agro‑based additives like beet juice—move through typical U.S. soils. Through a national survey, lab testing with sandy loam, and supporting machine‑learning analysis, researchers found that chloride migrates quickly through permeable soils, and beet‑juice additives increase that mobility by reducing adsorption to soil particles. While sodium and magnesium ions show limited retention, they may still migrate over time. These findings underscore the need for cautious, site‑specific winter maintenance practices, especially near vulnerable water sources, and are summarized in practical fact sheets to help agencies adjust deicer use and reduce environmental impacts.

MnDOT’s Complete Streets engagement kits are an innovative and engaging way to explore multimodal street design.  The upcoming in-person demo of the kits will be facilitated by the creator of the kits and is an opportunity for MnDOT staff to experience this tool first-hand. This event will demonstrate how the kits can be used in both casual and structured settings.

Thursday, August 13, 10:00-11:15 a.m.

Please turn your attention to this exciting upcoming webinar to learn how intersection design can impact communities.