Built between 2002 and 2007, the Veteran’s Glass City Skyway cost $273 million dollars and used the most cutting edge designs and materials, but that doesn’t mean it isn’t immune to manufacturing defects, or tainted materials. This bridge over Muamee River opened five years ago and has already had its share of issues, but this may be the most disturbing yet with far reaching implications.
The transportation department has been advised that the grout prepared at a Marion, Ohio, plant owned by the Sika Corporation contained excessive chloride compounds. The normal industry limit for chlorides in grout for use with steel cables is 0.08%, this grout had in excess of 0.5% at its highest levels. The most prevalent chloride in the grout is sodium chloride, a salt we are very familiar with as our own table salt. Sodium chloride is known to increase the corrosive strength of water and oxygen on steel; it is also know to speed the process of corrosion dramatically.
It is suspected several dozen projects across the United States have used this same chloride containing grout. Increased threat of corrosion discovered on several bridges due to high level of salts in grout used.
Ironically the function of this grout on this Skyway is to protect steel cables from road salts, water, and the oxygen that would normally be the primary causes of rust. However, the salts contained already in this grout may cause the steel cables to corrode prematurely. This accelerated corrosion won’t begin right away, but over time we can be sure tiny cracks will develop in the grout and the chlorides will be carried to the cables along with water and oxygen, beginning the process of corrosion that will weaken and cause damage to the bridge.
It is unknown how many infrastructure projects used the impacted grout, but it is clear many roads, bridges throughout the Midwest will have their long-term service life affected.
Issues with corrosion can happen with the best planned and best funded projects. A structure doesn’t have to be aging to require steadfast attention and monitoring of corrosion.
Corrosion monitoring systems in cases such as this could be invaluable to protecting the public good.