Civil and environmental engineers are the modern-day builders of civilization. From airports to parking lots, these engineers are responsible for the infrastructure that billions of people use every single day. One problem that has become a costly durability issue for civil infrastructures is corrosion. In the U.S., recent estimates by the Federal Highway Administration indicated that there are approximately 200,000 steel bridges and about 240,000 pre-stressed and reinforced concrete bridges, and roughly 15 percent of these bridges were considered structurally deficient due to corrosion [Materials Performance, 2002]. Of the estimated $137.9 billion cost of corrosion across industries, the direct cost of corrosion in highway bridges exceed $8 billion.
Recently, corrosion issues with post-tensioned tendons and grouting materials, such as enhanced chloride concentrations in raw materials and inadequate grout setting after pumping, for segmental bridges have garnered national attention. Industry, federal and state transportation organizations are involved to respond to observations of the material deficiencies and associated corrosion development. The recent corrosion issues appear distinct from earlier understood corrosion mechanisms. Particularly, recent instances of severe corrosion have not been consistently associated with enhanced chloride presence and grout voids formed from excessive formation of grout bleed water. Also, carbonation of the grout pore water, which may create corrosion conditions, was not identified. Furthermore, the recent corrosion issues have involved new grout materials meeting current material specifications.
CEE Assistant Professor of Structural Engineering Kingsley Lau is leading a study to understand the corrosion mechanisms of the steel components in tendons with deficient grout materials. The study looks to identify important material parameters in the corrosion development of strand in deficient grout materials, including elucidating the possible role of aqueous sulfates, pore water pH, and oxygen presence in corrosion initiation. Research outcomes aim to provide information to support possible future modification of building material specifications. Important findings include providing empirical support for establishing conditions and threshold limits for aggressive chemical species that may initiate corrosion of steel in deficient grout. Furthermore, FIU is aiding state and local transportation departments in assessment of available non-destructive technologies, such as Magnetic Flux Leakage, that may be used to identify bridge locations that have corrosion-related damage. These technologies are to be used to aid in identifying priorities for bridge maintenance and repair.
Lau is also engaged in research assessing novel coating materials for bridge applications. The study aims at providing state transportation departments understanding of associated corrosion deterioration modalities and possible application for bridge steel components subjected to various environments. Identification of novel coating systems is important so that effective and economical coatings may be applied with environmental considerations by transportation agencies to reduce bridge maintenance costs.
CEE is fast establishing itself as a major institution in Florida addressing the challenges with bridge durability related to corrosion. A corrosion and infrastructure materials durability lab, including an outdoor weathering facility as well as collaboration with the FIU structural engineering group, state and local transportation agencies and industry, has been developed to address the growing challenges associated with the sustainability of the aging civil infrastructure in the US.