As Lafarge Blends On Demand, Michigan Dot Approves Ternary Mix For Pedestrian Bridge

Lafarge North America, the largest supplier of cementitious materials in the U.S. and Canada, announced in mid-October it would provide high-performance

Lafarge North America, the largest supplier of cementitious materials in the U.S. and Canada, announced in mid-October it would provide high-performance Tercem 3000 cement blend to the Michigan Department of Transportation (MDOT) for construction of a new $7 million state-of-the-art, cable-stay pedestrian bridge in Detroit.

U.S. Concrete’s Superior Materials franchise will supply Tercem 3000 mixes for the cast-in-place Bagley Street pedestrian bridge, considered one of the most exciting elements to be built during Phase 4 construction of the Ambassador Bridge Gateway Project. With the pedestrian bridge being such an integral part of this massive project, it was very important that we focus on achieving the highest possible performance from the concrete used in the structure, says John Staton, materials engineer and manager of MDOT’s Materials Section.

The final and largest construction stage, Phase 4 of the Gateway Project is now under way to complete reconstruction of two Interstate freeways and improve access to the Ambassador Bridge, which is the primary U.S.-Canada commercial crossing carrying 23 percent of all surface trade between the two countries. Construction of the pedestrian bridge, which will extend over I-75 and I-96 to connect the east and west sides of Detroit’s Mexicantown community, will begin in March 2008. HNTB Corp. is the engineer for the project, with Walter Toebe Construction acting as primary contractor.

Tercem 3000 cement is a precisely formulated mixture of portland cement, ground granulated blast furnace slag, and silica fume. This ternary blend of materials works synergistically to meet our requirements for high-strength, long-term durability, and reduced permeability, says Tim Stallard, supervising engineer in MDOT’s Materials Technology Unit. It also offers excellent finishing qualities, as well as good freeze-thaw resistance when tested in accordance with ASTM specifications.

While enhanced strength and material properties were the primary reasons for choosing the ternary cement blend, the substantial environmental benefits are also desirable. Silica fume and slag are reclaimed industrial byproducts normally destined for landfills. Their use as a cementitious material reduces the portland cement content, thereby reducing energy consumed in the production process.

Before MDOT specified Tercem for the Bagley Bridge, it performed many lab and field tests to evaluate the product’s performance over the course of at least one winter season. The tests included placing Tercem concrete in several bridge overpasses throughout Michigan; and, as a result, Tercem is currently specified for several other MDOT bridges and continues to be monitored.

In addition to these high-performance and sustainability benefits, a local supply of high-quality preblended cement was also a key consideration in making our decision, adds Staton. Lafarge’s highly automated cement terminal on the Detroit River can create precisely proportioned and fully blended products, which brings a high degree of consistency, reliability, and quality control to this project.

Opened in June 2005 as part of the city’s economic revitalization of the riverside Springwells Industrial Park, the company’s $30 million Detroit River terminal is the largest cement silo in North America, standing more than 180 ft. high and 95 ft. in diameter. Although it appears from the outside to be one large round structure, the facility consists of one 17,000-ton-capacity main silo (for portland cement) surrounded by 10 peripheral bins (for a variety of specialized material), ranging in capacity from about 1,500 to 3,600 tons. Total capacity for the structure is approximately 44,520 tons.

Built by Graycor Construction Co. in just 14 days using an estimated 7,000 yds. of ready mixed placed in a continuous pour using slip-form molds, the silo also contains four precast columns made of Lafarge’s Ductal ultra-high-strength material.

All of the ingredients for Tercem are dry blended at the Detroit terminal by a mechanical blender that mixes at a rate of 500 tons/hour. The blending can be done either on demand direct to a customer’s truck or, for larger jobs, it can be preblended and transferred to a silo for storage.

Three bulk-loading bays and covered truck scales allow for year-round loading, unaffected by weather. The cement and cementitious materials are loaded through an automated delivery system, reducing load time for trucks. The operation also features a high-speed vessel receiving system for unloading of ships and barges. Additionally, it includes a 35,000-sq.-ft. packaged-product warehouse, where a high-speed packaging and palletizing operation can produce as many as 2,500 bags per hour.