Client:

Caltrans

Year:

2015

Location:

San Francisco, California

THE CHALLENGE

As the primary corridor for vehicles moving in and out of the city’s downtown core, the I-280 is vital for San Francisco traffic flow. To avoid major traffic disruptions for residents, repair work on a bridge hinge located on the highway’s Southern Freeway Viaduct required careful scheduling and logistics. Foremost among the planning concerns was concrete mixing, batching, and placement technique. Each hinge reconstruction consisted of four distinct types of concrete, so customization and batch speed would be crucial to project success.

THE SOLUTION

After careful consideration, a contractor using ProAll Volumetric Mixers was chosen for the job. The continuous pour capabilities of volumetric mixers were advantageous, as the concrete materials could be constantly replenished during placement for as long as necessary. The versatility offered by being able to adjust the mix on demand was also a meaningful benefit. The contractor was able to control the mix with admixture adjustment as the temperature varied and as the placement needs varied. There was no dead time waiting for strengths. The working time was engineered to be about an hour, so by the time the top of a stem was finished, the soffits achieved final set. Thanks to the unique advantages of mobile mixers, the bridge reconstruction was a resounding success.

53FT

BRIDGE WIDTH

100Hrs

BRIDGE CLOSURE LIMIT

16

MIX DESIGNS

qb concrete image

The contractor’s crews were openly impressed as to how soon forms could be stripped so as to move on to the next operation.


Roberto Luena, Engineer

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