The Willamette River Bridge provides a critical link on the I-5 corridor near Eugene, Oregon. In 2002 shear cracks found in the original 1961 structure prompted installation of a temporary bridge and planning for permanent northbound and southbound bridges. Construction of the new bridges began in the summer of 2009. By mid 2013 both the 1985 feet-long northbound and the 1759 feet-long southbound bridges were completed.
Slag cement was used to reduce heat of hydration in the large mass concrete footings and to achieve Oregon Department of Transportation (DOT) performance based “alternate” HPC requirements for the bridge decks. For the mass concrete a 60% slag cement replacement met heat and strength requirements, and yielded 56-day strengths exceeding 6200 psi. Where the bridge arches met in the middle of the river (dubbed “The Ice Breaker”), the steel reinforcement was extremely congested, and that portion could not be vibrated. A self-consolidating mixture using slag cement was developed that enabled filling the forms without leaving any voids. For bridge decks, Knife River was able produce a 30% replacement slag cement concrete mixture that achieved less than 1,000 coulombs when tested for at 90 days according to AASHTO T-277. This alternate concrete mixture provided outstanding quality, durability, strength, finishability, and pumpability.
Project credits: Oregon Department of Transportation, Owner; OBEC Consulting Engineers, Engineer; Hamilton Construction Company and Slayden Construction, Contractor; Knife River Corporation-NW-Eugene Division, Concrete Supplier; Cal Portland, Portland Cement Supplier; Ash Grove Cement, Slag Cement Supplier.