Paul D Krauss

Preliminary Corrosion Investigation of Prestressed Concrete Piles in a Marine Environment: Deerfield Beach Fishing Pier

Between the Fall of 1991 and Spring of 1992, a new fishing pier was constructed in Deerfield Beach, Florida, to replace a badly deteriorated pier that was demolished. The precast, prestressed concrete piles used in the construction of the new pier contained a water-based organic corrosion inhibitor consisting of amines and fatty acid esters. This inhibitor offers corrosion protection by reducing chloride ingress and by forming a protective film at the surface of embedded steel. In the Fall of 1993, a preliminary corrosion investigation of the piles was performed to assess the performance of the concrete used in the construction of the pier and to establish baseline values for future investigations. The techniques used included visual and half-cell potential surveys, and determination of chloride ion contents. Chloride ion contents at the reinforcing steel level were found to be well below that which would induce corrosion. Other types of testing and analytical techniques that may be used in future investigations to assess the performance of the piles and to predict their useful service life are also discussed.

Condition Survey of Older West Virginia Bridge Decks Constructed with Epoxy-Coated Reinforcing Bars

Chloride-induced corrosion of steel reinforcing bars is a major cause of deterioration in concrete bridge decks in northern climates. Corrosion-resistant epoxy-coated reinforcing (ECR) bars were introduced in the 1970s. In 1993, the West Virginia Department of Transportation (DOT) performed surveys of bridge decks treated with ECR and uncoated bars built in the mid-1970s. While deterioration was observed on uncoated bar decks, deterioration of decks built with ECR was found to be limited. The current investigation consisted of a questionnaire and review of the condition reports of the decks examined by the West Virginia DOT in 1993, followed by field condition surveys of six decks built with ECR to determine how the ECR was performing. The six bridge decks inspected were in good to excellent condition, with the exception of two spans of Bridge 2930, which were reinforced with uncoated black bars. The decks with ECR exhibited less than 0.15% corrosion-induced deterioration. Any deterioration observed on ECR decks was concentrated at cracks or construction joints. All actively corroding ECR bars had an average coating thickness less than 7 mil (0.007 in.), the current minimum specified thickness. Decks reinforced with uncoated black bars included in the 1993 study had an initial service life of 18 to 21 years, and an overlay was applied to all of these decks to address corrosion-related damage. The decks constructed with ECR are now 33 to 35 years old, and none have required rehabilitation to address corrosion-related deterioration.

Repair materials and techniques for concrete structures in nuclear power plants

The paper summaries portions of work of the Structural Aging Program, sponsored by the Nuclear Regulatory Commission (NRC). The paper addresses the assessment and repair of concrete structures in nuclear power plants. It presents the results of a survey of the the nuclear power plants in the United States to identify susceptible concrete components, rates of occurrence of deterioration, and to determine the durability of repairs. The paper describes deterioration mechanisms and discusses their effect. Repair techniques are described. Evaluation techniques and nondestructive test techniques are also discussed.

HIGH-PERFORMANCE CONCRETE FOR THE RECONSTRUCTION OF WACKER DRIVE

The existing viaduct structure on Wacker Drive in downtown Chicago, Illinois, is being replaced due to severe corrosion of the embedded reinforcing steel and spalling of the concrete cover. A new structure is being built using high-performance concrete (HPC). The deck is posttensioned HPC concrete, with a latex-modified concrete overlay placed over the deck to provide the wearing surface and further protection of the embedded steel in the HPC deck. A prototype of the structure was built and load tested to failure. This paper discusses the development of the HPC, and the importance of screening raw materials, testing of HPC mixes, and the implementation of a quality assurance program.