Among the high praise the Bay Bridge's new eastern span has received for engineering and design is another significant achievement: a lower carbon footprint than its predecessor.
Carbon dioxide output was reduced by at least 60 million pounds by using cement containing 25 to 50 percent recycled materials instead of traditional Portland concrete, according to Jeff Davis, vice president and general manager of Central Concrete Supply Co., which engineered more than 40 mixes specifically for the new span.
The environmental impact is 20 to 25 percent lower than that of Caltrans public works projects prior to Assembly Bill 32, California's 2006 Global Warming Solutions Act, which requires the state to reduce greenhouse gas pollution to 1990 levels by 2020.
"In the last four, five years, Caltrans was extremely aggressive and proactive," Davis said. "And through that, we were designing concrete for this job that was cutting-edge as far as low [carbon dioxide]."
Central Concrete, the local operation of U.S. Concrete, readily took on the "uncompromising demands" the project presented, according to Greg Allen, manager for MCM Construction Inc., a lead contractor.
Since first becoming involved in the Bay Bridge project in 2001 by supplying equipment and technical expertise, Central Concrete has delivered more than a quarter-million cubic yards of its product -- equivalent to covering a football field 153 feet deep.
The concrete's green qualities do not compromise its performance, Davis said, which is extremely high and designed to last more than a century.