Some road engineers suggest that simply lowering the freezing point of the bridge deck is a proven and effective way to reduce accidents caused by black ice. But what does that mean? Pouring alcohol on bridge decks may also prevent black ice from forming, but it's not an economical solution.
Fortunately, there are more practical methods of de-icing that employ special de-icing chemicals. To meet the challenges of maintaining safe roads, manufacturers are consistently revising the formulations of these de-icing chemicals. Their goal is to lower the freezing points by depressing the freezing point of water on a wide range of substrates.
As a result, when time and weather conditions permit, state DOT fleets apply de-icing chemicals on raw, untreated concrete bridge decks to help lower the freezing point on the surface, and thus prevent ice from forming.
The effort began in the 1980s when researchers at the Virginia DOT established a Multiple Coat Epoxy Polymer Overlay Specification. It outlined the chemical and physical properties for an epoxy compound that has shown outstanding durability and performance. These efforts also developed a chloride test to examine the effectiveness of the epoxy overlay and provide near zero permeability.
But one of the best aspects of the specification was including an angular shaped, gap-graded aggregate of specified required hardness, size, and shape. This meets the requirements of AASHTO T103-91, “Soundness of Aggregate by Freezing and Thawing,” to produce long-term durability and anti-skid properties.
This research received national attention in 1993. The Rapid Concrete Bridge Deck Protection, Repair and Rehabilitation, SHRP-S344, Strategic Highway Research Program, released “a study of polymers that have shown an established long-term history of use and acceptance as a waterproofing compound providing a long-term durable, anti-skid resistant surface.” Mike Sprinkel, associate director, Virginia Transportation Research Council, and professor Richard Weyers at Virginia Tech, co-authored the report.
This led to “Guide Specifications for Polymer Concrete Bridge Deck Overlay,” which was released by AASHT0-AGC-ARTBA, indicating similar chemical and physical properties for waterproofing and durability with specified aggregate for long-term antiskid properties. Details included surface preparation, with quality control assurance procedures to determine suitability of the deck as a candidate for a polymer overlay.