New Liberty Memorial Bridge built with Lafarge fly ash concrete

HERNDON, VA. — High-performance fly ash concrete from Lafarge is playing a key role in achieving the high strength, long-term durability, and extended service life goals for the new Liberty Memorial Bridge in Bismarck, N.D., the company said.

The signature high-profile, long-span bridge, dedicated to honoring North Dakotan veterans, provides more vertical clearance for tall boats and has a longer than average space between the sup­ports that hold the bridge above the water, allowing more of the river and scenery to show. The massive center section of the bridge is over 285 feet in length, with a total of 14 spans on 13 piers, with 6 piers located in the Missouri River.

The $62-million 2370-foot-long structure used almost 20,000 cubic yards of high-performance 35 MPa (5,000 psi) concrete containing Class F fly ash and Type I/II portland cement. Derived from burning coal in electric utility plants, fly ash can be used as a supplementary cementitious material for improving the strength, durability, and other properties of concrete.

In addition to its economic and performance advantages, fly ash use in concrete is also good for the environment as it saves virgin raw materials and makes use of an industrial by-product that might otherwise be disposed of in landfills. It also allows concrete producers to optimize their use of portland cement, thereby reducing the carbon footprint and lowering the embodied energy of concrete.

The Liberty Memorial Bridge project began in mid-2006 and the first phase of construction — one lane open in each direction — was completed in November 2008. The environmentally-friendly, high-performance fly ash concrete mix design met quality construction needs during both hot weather and freezing winter conditions, as well as for the mass concrete pours requirements in the piers and abutments.

The project’s final construction phase — removal of the old bridge and completion of the new four-lane bridge with plazas and riverside parks — is expected to be finished in July 2010. The bridge design incorporates a 10-foot wide pedestrian walkway and five overlooks or concrete walkouts as a tribute to each branch of the military: Army, Navy, Air Force, Marines, and Coast Guard.

For more information about Lafarge North America, please visit www.lafarge-na.com.