Research Project Summary Information
Advanced Energy-efficient Coating Systems for Transportation Infrastructure(ST9951-1)
Corrosion of steel and steel reinforcement is a major deterioration mechanism for transportation infrastructure in New York State. Approximately 12% of the NYS bridge inventory (17,338 bridges in 2005) is structurally deficient, mainly due to corrosion-induced damage. The annual direct cost of corrosion for the U.S. highway bridges is estimated at $8.3 billion, consisting of $3.8 billion to replace structurally deficient bridges, and $4.5 billion for maintenance and repairs. Indirect cost associated with traffic delays, traffic control, loss of availability to use, . and productivity are more than ten times the direct cost of corrosion.
An efficient and cost effective way of protecting steel from corrosion is to use protective coatings. Proper concrete curing, increasing concrete cover depth, and using high performance concrete will significantly slow the rate of chemical attacks but cannot guarantee full protection against corrosion. Among existing systems, epoxy coatings are the most widely used for reinforcement corrosion protection and have shown satisfactory results when exposed to corrosive environments. Nevertheless, defects in the coating and/or inadequate film thickness facilitate the transport of the corrosive species to the substrate, which can result in progressive loss of adhesion accompanied with under-film corrosion.
Concrete acts as an excellent cover for embedded steel bars and provides an ideal environment for steel protection against corrosion due to its high alkalinity. However, chloride ions originating from deicing salts and marine exposure can penetrate the concrete cover and increase the chloride content of the concrete pore solution near the steel bars. Once the chloride concentration reaches a critical value, it destroys the passive film around the bar and, in the presence of oxygen and humidity, triggers the corrosion process. Corrosion products could occupy a greater volume than the original steel. This expansion exerts pressure on the concrete surrounding the steel reinforcement and results in tensile stress in the concrete cover, which may cause cracking with subsequent corrosion damage. Corrosion-resistant reinforcement increases the service life of the structure by increasing the chloride level at which the corrosion initiates.
If successful, this new technology may provide an improved way to prevent corrosion in transportation infrastructure and result in economical, environmental, and energy benefits for the State of New York. The economic benefits include saving billions of dollars in repair, maintenance, and replacement of transportation infrastructure. Other benefits include reducing traffic delays and congestions, reducing traffic control, and reducing loss of use and productivity. The environmental benefits include reducing the amount of waste materials resulting from the demolition of structurally deficient structures, which conserves landfill space, savings in the usage of new material required for replacement of these structures, and can increase the efficiency in use of construction materials. Cement is the one of the main components of concrete mixtures, and reducing cement consumption will reduce the emission of carbon dioxide and other greenhouse gases, which facilitates compliance with the environmental regulations. The energy benefits include savings in the energy required for maintenance, rehabilitation and replacement of damaged structures, and savings in energy consumption during the production of construction materials needed for new constructions.
Very competent laboratory research was conducted and well documented. The understanding of the corrosion issues was increased, but the commercial aspect of the coating product was never realized.
Attn: Comptroller's Office Po Box 5546
Potsdam, NY 13699
NYSERDA Contact Information
R&D -Transport & Power Systems