(SDOT photos, courtesy Darin Stephens)
Some driving the Spokane Street Viaduct in recent days have asked why squares are being cut from some of its newly paved surface. The questions started in the comment section following our Friday update on the close-to-completion project.
As promised, we followed up with SDOT. Project spokesperson Paul Elliott talked with project manager Stuart Goldsmith and replies that the problem is delamination – some of the new concrete didn’t bond with the old concrete: “Repairing and resurfacing the old bridge deck required a hydro-demolition process to clean and roughen the old deck to ensure a good bond when the new thin lift micro silica overlay was then applied. If there is any oil or other dirt remaining, we can end up with delamination/an inadequate bonding.” (The hydro-demolition process was discussed in our story about a work-zone tour two months ago.)
The delaminated spots were discovered with a low-tech type of testing, which you can see in WSB coverage of the Fauntleroy Expressway seismic-retrofit work back in January – “the best way to determine whether or not the bond is solid is to drag metal chains across the top and listen for problem areas,” as Elliott explains it. The problem spots (we’re checking back to ask how many) were cut out for repairs:
He says the work will not set the schedule back further. Meantime, other work that’s going on includes pouring of the permanent concrete barrier between westbound and eastbound – the green material is the rebar:
And here’s a section after the pour:
Milestones ahead for the project: Friday morning, as noted in our day-by-day closure list, the Harbor Island onramp to the eastbound SSV reopens after its long closure; starting next Monday (August 20th) the 1st Avenue South offramp from the eastbound SSV closes for about 5 weeks, during which time it’ll be repaved.
ADDED 6:18 PM: SDOT’s reply to our followup questions, which included: How much of the resurfaced bridge deck has the delamination problem? Why did it happen? What about concerns of an uneven surface post-repairs?
The percentage of the new roadway requiring repair due to delamination was less than 5% of the total resurfaced area and was well within expectations given the condition and age of the old deck. Delamination repair was anticipated as part of the deck refurbishing process, which is why we test it, and does not delay the project.
Drivers on the roadway, to include motorcycle riders, should not be able to detect the cuts once they are filled with concrete. We will continue to review the contractor’s work to ensure the roadway meets the required specifications prior to the city accepting the work as complete.