Bridge crack fix spawned more fissures
When Oregon transportation officials and lawmakers argued for the state's last big transportation measure, the $2.5 billion Oregon Transportation Investment Act of 2003, they often pointed to an alarming number of cracks in concrete bridge decks.
But while the funding package that year paid for about 80 new bridges and repair of about 160 others, the brand-new bridge decks began cracking almost immediately — to the surprise and dismay of ODOT engineers.
As a 2008 ODOT report noted, "bridge engineers are concerned about the early signs of deck cracking on many newly constructed bridges that portend future deck rehabilitation needs ... sooner than would have otherwise been expected."
By 2010, two-thirds of the concrete bridges built since 2003 were already showing cracking — two of them severely, ODOT records show.
Normally, decks are supposed to last 50 to 100 years. Cracks in bridge decks, however, can increase the amount of moisture inside a bridge deck, accelerating the degradation of the concrete and steel within it.
The cause of the outbreak of cracks wasn't immediately determined, and other states have had cracking problems, too. But ODOT's top bridge engineer, Bruce Johnson, now contends the addition of extra cement to the concrete to obj:23607} explains the extent of the problem in Oregon. The cracks are a "direct result" of combatting studded tires, he said earlier this year.
Click here to read an accompanying story on the debate over studded tires
The cracks have become an even greater concern, studies show, due to ODOT's increased use of magnesium chloride deicer and road salt in recent years to combat icy roads. Deicer and salt can accelerate the deterioration.
"Early-age bridge deck cracking is a major concern for many DOTs throughout the United States and specifically those in the Pacific Northwest," said a 2014 study done for ODOT. "Cracking within the first months of a bridge deck's lifespan severely hinders its long-term performance and durability, ultimately reducing the sustainability of this crucial piece of transportation infrastructure. Increased maintenance costs, driver interruptions and damage to the bridge structure may result."
"This is a specific problem that the Oregon DOT has experienced and is trying to find solutions to reduce or eliminate related cracking."
ODOT has adopted a variety of beefed-up bridge inspection methods to spot the cracks so they can be filled in with an epoxy-like seal. And the department continues to explore additional methods, including the use of drones.