Road salt, most often sodium chloride (NaCl) melts ice and is a crucial tool for winter maintenance crews around the world. However, the constant application of road salt is resulting in long-term environmental and economic impacts. To slow the negative effects of sodium chloride deicers by optimizing salt use, researchers from WTI and Washington State University completed Understanding the Salt Phase Diagram, a project sponsored by Clear Roads, a Federal Highway Administration (FHWA) pooled fund. Led by Laura Fay, WTI’s Cold Climate Operations and Systems Program Manager, the team completed a literature review and laboratory investigation of the NaCl phase diagram, a graphical representation of the physical states (liquids or solid salt/ice) of salt brine depending on concentration and temperature. They distilled the information into training materials to help winter maintenance practitioners better understand the salt phase diagram and to support efficient and effective roadway deicing.

To provide visual aids for the training materials, the researchers needed to demonstrate the behavior of salt solutions in a laboratory setting. They collected video and photographic evidence of ice formation in salt brine at a range of concentrations and temperatures, verifying the familiar process of lowering ice’s freezing point with the addition of salt. They also clarified the effects of high salt concentrations on ice formation.

By synthesizing their laboratory data, the researchers created an updated NaCl phase diagram, fact sheet, and accompanying video. WTI’s Visual Communications Manager, Neil Hetherington, ensured that the phase diagram was associated with easily recognizable design elements (e.g., green = good = ice prevention). Fay noted, “Neil [Hetherington] took subject matter that was science and engineering heavy and converted it into useful, digestible information that is easily transferable. He also took time to collect quality photographs which effectively conveyed the information.”

The research has been well received. Fay has presented the training materials and findings to multiple organizations. “These materials serve as powerful education tools,” noted Fay, “and they are being used across the country.”

The full report is available on the project webpage of the WTI website.  The video may be found here: https://www.youtube.com/watch?v=xzrvOoJGH_w