Cemex has supplied structural concrete for two transit systems in the California Bay Area: San Francisco’s new intermodal Transbay Transit Center and an extension of the Bay Area’s Rapid Transit system into Silicon Valley.
The concrete Cemex supplied for these massive projects had very specific considerations due to the Bay Area’s groundwater levels and the sustainability specifications of each project.
In San Francisco, the Transbay Transit Center underground structure required stringent low permeability and low shrinkage concrete. Complex logistics due to the location in an extremely busy neighbourhood meant that Cemex trucks could only be dispatched from 11:00pm on Friday through Saturday afternoon to complete the 15 large, continuous pours of up to 5000 cubic yards.
Along the Berryessa extension’s 10-mile route in the South Bay, groundwater levels varied and required individualised attention. Cemex worked closely with the client to develop, test and deliver 35 tailor-made concrete mix designs to meet the needs of each section of the line.
Architect César Pelli’s firm, Pelli Architects, designed the Transbay Transit Center with the aim to achieve a Leadership in Energy & Environmental Design gold certification. A Cemex quality control team worked closely with the client to design concrete mixes for all the structures, which included up to 35% supplementary cementitious material.
The Berryessa project also had sustainable components, including a concrete mix that Cemex designed specially using recycled material removed from the old rail beds and a concrete mix for the massive foundations that included 50% supplementary cementitious material.