The purpose of this study was to determine the impact of a magnesium chloride-based deicer, a sodium chloride-based deicer, and the major salts contained in these deicers on seed germination and seedling growth and development of fifteen species of grasses and forbs native to Colorado. Seven of the fifteen species performed well at the low and medium concentrations of the salts and solutions; these are plants that can likely germinate in roadside areas.
Roadside vegetation is exposed to a variety of biotic and abiotic stresses that can impact plant health. Drought, pollution, disease, insects, lack of nutrients, and roadbed management practices may potentially act alone or synergistically to adversely affect plants in proximity to the roadside. To date, little published research documents the impacts of certain deicers on vegetation in relationship to other potential stresses. This study provides an ecological impact assessment of factors affecting the health of roadside vegetation in the state of Colorado including potential biotic and abiotic plant stressors and deicer applications.
This study is the evaluation of two thin bonded epoxy overlays. These two products were compared on the basis of physical properties, including mean texture depth, surface friction, bond strength, ability to stop chloride intrusion, and anti-icing properties, as well as traffic safety and cost. Both overlays worked as intended when they were initially applied on the bridge decks. Mean texture depth and friction testing have shown that they both provide a durable wearing surface with good traction.
The overall conclusion of the study is that application of magnesium chloride deicer having a chemical composition and application rate similar to those of 1997-98 is highly unlikely to cause or contribute to environmental damage at distances greater than 20 yards from the roadway. Even very close to the roadway, the potential of magnesium chloride deicer to cause environmental damage is probably much smaller than that of other factors related to road use and maintenance, including pollution of highway surfaces by vehicles and use of salt and sand mixtures to promote traction in winter. Magnesium chloride deicer may offer net environmental benefits if its use leads to a reduction in the quantity of salt and sand applied to roadways. The environmental safety of magnesium chloride deicer depends, however, on low concentrations of contaminants and avoidance of rust inhibitors containing phosphorus. Appropriate specifications for vendors and routine testing can insure the continued environmental acceptability of magnesium chloride deicers. Deicers provided by vendors should be monitored independently by CDOT for chemical characteristics. Any significant changes in processing or source material should be disclosed by the vendor. Colorado-based specifications should be developed for vendors. Independent specifications for low elevation could be developed, or the more stringent high elevation specifications can be applied to all purchases.
The results of this study confirm the performance of the baseline CDOT bridge deck mixes/systems, indicate some new products that show promise for implementation, and suggest that combinations of products might be the best approach to protection for Colorado bridge decks exposed to deicing chemicals.
This project focused on the chloride-induced corrosion of reinforcing steel in structural concrete. The primary goal of this project is to analyze the surface chloride concentration level of the concrete bridge decks throughout Colorado. The study indicates three factors that can affect chloride concentration levels in bridge decks: age of the concrete, traffic, and weather. Samples were collected from decks and curbs of bridges in different climate regions with various concrete ages and traffic levels. Water-soluble chloride concentrations were tested for all samples. Chloride concentration profiles for all the locations were listed and plotted. The deepest concrete powder was collected at a depth of 2 inches. The rebar level of the bridge was usually at or below this depth. The chloride concentrations of most bridge decks were below the critical values at the rebar level. The chloride concentrations of bridge decks are usually greater than that of bridge curbs. However, these bridge curbs showed deeper chloride penetration than the bridge decks. Younger bridges had much lower chloride concentrations, which is expected. Heavier traffic resulted in higher chloride concentrations. The bridges built in colder regions had a higher chloride concentration up to 2" depth (the rebar level). Climate may be the most significant influential factor among age, traffic, and climate when considering chloride concentration of bridge decks in Colorado. Corrosion protection should focus on the bridges decks who locate in the cold climate zone and with high traffic volume.
