SP-151 The Philip D. Cady International Symposium was held in Minneapolis, Minnesota, on November 9 and 10, 1993. The symposium volume includes 15 papers on concrete bridges in aggressive environments. The papers address the performance, protection, assessment, and the repair and rehabilitation of concrete bridges. The performance papers include the corrosion protection afforded by concrete bridge deck overlays, corrosion in prestressed concrete bridges, and the use of calcium nitrite in field structures. Protection papers address the performance of silane sealers, coatings, and waterproofers. Condition assessment technologies include measuring the corrosion rate of steel in concrete and the diffusion of chloride ions in bridge decks with overlays. Experiences in the repair and rehabilitation of concrete bridges by practitioners is also presented. The Philip D. Cady Symposium was sponsored by ACI Committees 345, 222, 515, and 201.

Explains the technology developed by Alberta Transportation and Utilities for field prestressing repairs to precast, prestressed concrete bridge girders. This repair technique restores structural integrity quickly and cost effectively. Applications regarding high load impact damage and corrosion of prestressing strand are discussed, based on Reid Crowther's experience and application of this repair technique.

The importance of solvent- and plasticizer-free sprayable PU elastomers in the field of waterproofing of concrete structures has increased considerably over the last 10 years. Due to their excellent mechanical properties, their resistance to hydrolytic and microbial attack and chemical resistance, waterproofing membranes produced from spray-applied PU elastomers have proved to be very successful in many application areas in the building industry. Report deals with the chemical development of the PU system, the optimization of the processing technique, including the methods of preparing the concrete's surface to get good adhesion values and a seamless, watertight elastomeric membrane, the spray process itself, and the recommended machinery. Special attention is given to the influence of environmental conditions, such as temperature and relative humidity, on the mechanical properties and the performance of the waterproofing membrane in service. As the most important field application for spray-applied PU elastomers in Europe, bridge deck waterproofing membranes are discussed with special reference to the requirements set out in the regulations of the German "Bundesministerium fur Verkehr" and the "Bundesanstalt fur Materialprufung." The performance of spray-applied PU elastomers as waterproofing membranes for roofs, terraces, terracing in sports arenas, and car parks is discussed.

A computer simulation study of the penetration of chloride through concrete bridge decks with overlays was undertaken. The chloride transport was modeled as apparent diffusion. The apparent diffusion approach was based on the analyses of chloride concentrations obtained from field measurements. Part of the field data included untreated concrete decks and decks overlaid with latex-modified concrete, low-slump dense concrete, or microsilica concrete. The overlay field data was limited in number and repair details. In particular, the overlay data base did not include three significant details: the amount of original deck material removed, the thickness of the overlay placed, and the resistance to chloride penetration of the overlay material versus the original deck material. Consequently, a computer simulation was used to investigate the impact these three repair details have on enhancing the service life of a deck repaired with an overlay. Quality of material was defined by the apparent diffusion constant, a measure of the resistance to chloride penetration. The ranges for apparent diffusion constants were estimated from the overlay data base. Service life was defined as the time required to reach a critical chloride threshold level.

Describes investigation and design of repairs to the approach decks of the Verrazano Narrows Bridge in New York City. In addition, all the joints will be replaced, electric manholes and pull boxes will be rehabilitated, and new power and communications cables will be pulled. These bare concrete decks exhibit extensive deterioration in the form of spalls, cracks, leakage, and efflorescence. A total of approximately 787,000 square feet of deck area will be repaired; this includes approximately 150,000 square feet of deck replacement. Total estimated cost is $45 million, and the construction duration is 5 to 6 years.