Concrete Products

OCT 2013

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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Page 32 of 51

FEATURE COVER STORY When JS1000 is used with precast deck panels, precast box girders or bulb-tee girder joints, fabrication and installation processes are simplifed, full deck continuity is achieved and the bridge deck joint is no longer the weakest link, Lafarge engineers affrm. Lafarge began JS1000 commercialization in 2004, initially through collaboration with the Ministry of Transportation of Ontario (MTO). The frst feld application involved a bridge at Rainy Lake over the Canadian National Railway line in 2006. MTO has led North American transportation agencies in Ductal Joint Fill applications since, followed by the New York State Department of Transportation. In North America, the JS1000 business has become self-perpetuating, Lafarge offcials note, indicating an opportunity for enormous growth. In 2010, fve bridges were completed with the product. In the summer of 2013, thirty-six projects were slated for completion by year-end. With projects now completed in Ontario, New York, Iowa, Montana, Massachusetts and Oregon, acceptance is increasing at a rapid pace. By the end of 2014, it is expected that Ductal Joint Fill projects will also be completed in Ohio, Pennsylvania, Manitoba, Nebraska, New Jersey, Utah and South Carolina. FHWA measures growth of Ultra-High Performance Concrete Adapted from the Federal Highway Administration's September 2013 Focus e-newsletter… A new report summarizes UHPC research, development, and deployment efforts around the world. Ultra-High Performance Concrete: A State-of-the-Art Report for the Bridge Community (Pub. No. FHWAHRT-13-060) includes details on materials and production; mechanical properties; structural design and testing; and, durability measurement. "This information allows State and local transportation agencies, researchers, and others to deepen their understanding of UHPC and the opportunities it offers to accelerate bridge construction," affirms FHWA's Ben Graybeal, who co-authored the report with Glenview, Ill., engineering consultant Henry Russell. UHPC is an advanced cementitious composite material developed in the 1990s and commercially available in the United States since 2000. It is typically acquired from a supplier in three separate components: pre-bagged cementitious powder, steel fibers, and chemical admixtures. Water completes the mixture. The UHPC is then placed into the formwork using standard construction equipment. The FHWA began investigating UHPC for highway infrastructure use in 2001 and has worked with State transportation departments to deploy the technology since 2002. Bridge applications have included using UHPC for precast/prestressed girders; precast waffle panels for bridge decks; and, as a field-cast material joining precast concrete deck panels, girders, and adjacent girder flanges. Compared to conventional concrete materials, Graybeal and Russell contend, UHPC exhibits superior properties such as exceptional durability, ductility, high compressive and flexural strengths, and long-term stability. It generally contains high cementitious materials, low water-to-cement material ratios, compressive strengths above 21,000 psi (150 MPa), and sustained tensile strength resulting from internal fiber reinforcement. These advanced properties have been used to develop new structural forms that facilitate accelerated bridge construction. While UHPC has higher initial costs than conventional concrete, bridges with UHPC components are expected to have a longer service life and require less maintenance than conventional structures. The new FHWA report highlights projects in the United States, Canada, Europe, Asia, and Australia—among 90-plus UHPC bridges in service worldwide. The first domestic highway structure to use UHPC was the Mars Hill Bridge in Wapello County, Iowa (2006)—a simple, singlespan structure with precast/prestressed girders and cast-in-place deck. Subsequent projects in Iowa have included the Little Cedar Creek bridge (2011), the world's first structure to feature a precast, full-depth UHPC waffle-deck panel system connected with field-cast UHPC joints. Ultimately, the material's mechanical and durability properties allowed the construction of a resilient, lightweight deck system that was completed in about 70 percent of the time compared to a similar design using conventional concrete mix. The new UHPC connection details eliminate conflict points between the reinforcing bars and discrete connectors, allowing for easy field assembly. Buy America provisions are relevant to the steel fiber reinforcement used in UHPC. States that are planning to use UHPC in projects should work with their FHWA division office early in the design process to determine the availability of a domestic manufacturer. "There are strong indications that a proven class of steel fibers will be domestically produced and available by the end of 2013," says Graybeal. While highlighting UHPC projects to date, the report also examines the future direction of the technology and current challenges to achieving wide-scale implementation in the United States. These include the need for more demonstration projects, cost-benefit studies, and a new design and production document based on the American Association of State Highway and Transportation Officials' Load and Resistance Factor Design BridgeDesign Specifications and the AASHTO LRFD Bridge Construction Specifications. October 2013 • 31

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