Calcium nitrite corrosion inhibitor has been commercially available in the U.S. since 1978. In that period of time, over 200 parking structures, 100 marine structures, and more than 230,000 m 3 (300,000 yd 3) of precast/prestressed bridge girders have been constructed with concrete containing calcium nitrite. In this paper, several of the oldest structures, along with several test sites, were evaluated to determine the corrosion performance. The condition assessment included a visual evaluation of the structure, determination of chloride and nitrite contents in the concretes, and determination of the corrosion activity. The corrosion tests consisted of corrosion potential mapping and polarization resistance testing to determine the corrosion rates at the time of the evaluation. These assessment techniques are applicable to all steel reinforced concrete structures with or without some modifications. The assessment showed that all of the structures with calcium nitrite are performing well. In two cases, there is evidence that corrosion is in progress on adjacent structures that were not protected with calcium nitrite. The nitrite analyses document that calcium nitrite is stable in concrete and remains at the reinforcing bars. Diffusion of chloride is not increased in the concretes with calcium nitrite, and there is evidence of a reduction in chloride penetration in some cases.

In the early 1960s, the city of El Paso constructed the Texas, Piedras, Raynor Street Bridge, a mile-long, four-lane artery leading to the center of downtown, and a main road important to many businesses and merchants. Time and the effects of chloride penetration from road salts, plus carbonation, took its toll on this bridge. Corrosion of the reinforcing steel led to spalls on pier caps and corrosion of columns, in addition to massive spalling and delaminations of the bridge deck and parapets. Early in 1990, a complete structural repair of the bridge was conducted. Attempts to repair the bridge were unsuccessful. Cracks and delaminations in the substrate and in the areas that had been repaired were evident. Due to safety concerns, the bridge was closed for structural repairs. Repairs began again in November 1991. The first stage of repair consisted of removing the previous failed materials and all unsound concrete. Once all areas were prepared, the low-pressure spraying of a structural, one-component, high-strength fiber reinforced, shrinkage-compensated product began. Three men were employed in the batching and spraying of the material--two at the hopper/mixing unit, and one operating the spray nozzle. Using a pump for placement, the contractor was able to realize a maximum of 3 yd 3 per hr. Workers with trowels followed closely behind the nozzle man, and, using a finishing aid, were able to finish the placement quickly and efficiently. Circular bridge piers were finished with a template to maintain the design cross section. A water-based curing compound was applied to insure maximum moisture retention and full hydration of the mortar. All patches were covered with thermal protection for 7 days, to allow for cure. Because the sprayed material adheres well, it performed exceptionally on all of the vertical and overhead repairs required on this bridge. Its excellent bond strength, outstanding structural properties, and low permeability provided the needed characteristics for this job. The sprayability of the product meant less labor required on the job and faster turnaround. Since this was the second repair of this bridge, these characteristics were very important. The product performed exceptionally well and resulted in a hard and dense repair.

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 role of concrete in the corrosion of steel in reinforced concrete has received a considerable amount of attention in recent years. This is due to the recognition of the strong relationship between the nature of the concrete and its ability to protect embedded steel. Therefore, in addition to some of the commonly used corrosion protection methods that focus on either coating the concrete, increasing the cover of the concrete, coating the reinforcing steel, or the use of inhibitors that change the nature of the surface of the reinforcing steel, other methods should be included that emphasize the role of the concrete mix design. Paper deals with the contribution of concrete to the corrosion of reinforcing steels in reinforced concrete. Twenty-six mix designs that represent concretes that could be used today were selected for study. Variables included cement content, water content, amount and type of fly ash, the addition of superplasticizers, and air entrainment. Strength and macrocell current were measured as a function of chloride exposure. The results of 1 year of cyclical exposure to 3.5 percent NaCl solution revealed that the concrete influences the corrosion process greatly. Furthermore, modification of concrete can become another method of corrosion protection through a better understanding of the relationship between the corrosion process and concrete mix design.

Penetrating concrete sealers are often used on highway bridges and parking structures to slow down the rate of chloride-related reinforcing steel corrosion, thereby extending service life and reducing life-cycle structure costs. Silane sealers are the type most commonly used and are evaluated. Presents data on the effects of several variables on the resultant dampproofing performance and penetration depth. These variables include substrate conditions that influence sealer penetration depth, total active silane content, and the effects of subsequent silane retreatments. The Alberta Transportation and Utilities (AT&U) sealer evaluation methods that are used to measure dampproofing performance and effective penetration depth are described. Data show that the permeability of modern high-quality, low-permeability concretes can be significantly improved by silane sealers, whereas porous, high water-cement ratio concretes may be more effectively sealed by barrier coatings that seal the surface of porous concrete and do not penetrate. The concept and method of measuring the effective penetration depth is explained. Increasing the concentration of the active silane in a penetrating sealer improves both the effective penetration depth and the overall dampproofing performance on modern, good-quality concrete. Periodic resealing of the concrete with lower concentrations of silane results in a similar effect. Resealing can be successfully done through the previously sealed surface without expensive methods of surface preparation as long as the surfaces are clean and dry.