At one time or another, it seems most people in East Portland use the Sellwood Bridge to get to the West Side. Learn why Multnomah County is using “superglue” to prolong the life of the bridge …
Injection ports, affixed to the concrete directly over the cracks, allow the contractor to force high-strength epoxy into Sellwood Bridge cracks under high pressure.
Story and photos by David F. Ashton
It isn’t a joke that the Sellwood Bridge – dedicated in 1925, and considered to be in the poorest condition of all major Oregon bridges – is now held together with glue.
Earlier this year, Multnomah County bridge crews examined every inch of the bridge. They documented cracks in its concrete superstructure, particularly on the ramp approaches to the bridge on both sides of the river.
The epoxy is being pumped through these plastic tubes, into the injection ports, under high pressure.
During the last two weeks in August, contractors completed a $100,000 project that involved cleaning 450 lineal feet of cracks and filling them with an epoxy cement.
“The process prevents water from corroding the steel rebar in the concrete, and slows the growth of cracks,” explained county spokesman Michael Pullen.
The ports are sealed with a red cap after the crack is filled.
Epoxy injected under pressure
Drivers who ignored the “Bridge Closed” signs, drove up to the foot of the bridge, and then had to make a U-turn, couldn’t see the workers as they injected the epoxy into cracks during the evening hours.
A crewmember of the Leewens Corporation, the Seattle-based company contracted to do the injection work, showed us the “mixing head” with which the two-part epoxy is mixed, ready to be pumped into the cracks.
This superglue isn’t just smeared into the cracked concrete. Workers first clean out the fissures, then install “ports” into which the epoxy mixture is pumped. Then, the mixture, now a high-strength bonding agent, is used to seal the cracks and ports.
A supervisor charts the progress of the epoxy treatment as the project continues.
We watched as a worker on a high-lift, 60 feet above the ground, attached two epoxy-filled tubes to the ports, and then injected the glue under 50 pounds of pressure till it oozed from an adjacent port. The ports were then capped, and the worker moved on.
According to information provided by the contractor, “a full depth permanent repair is achieved by injecting a high-strength epoxy grout, under pressure, into the crack”.
Below the bridge ramp, a supervisor charted the progress of each injection, as the crew moved from site to site.
Although most of the epoxy injection work was completed during the twilight hours on each of the days the bridge closed just before 6:30 pm, the bridge remained closed all night – to all but cyclists and pedestrians – to allow the epoxy to cure without vibrations from traffic.
The bridge is now open to motorists, but it remains closed to vehicles weighing 10 tons or more.
Weight restriction stays in place
The per-vehicle weight limit on the Sellwood Bridge was reduced to 10 tons in 2004, after cracks were found in the concrete girders that support the bridge ramps.
“This summer’s repairs will not allow those weight limits to be increased,” Pullen conceded. ”But the project should extend the life of the bridge at its current service level, until a long-term solution is implemented.”
© 2008 David F. Ashton ~ East Portland News