ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/296646
Portland Cement Association Service Life Design for 100 Years? T his past summer, I had the opportunity to follow portions of Route 66 through Illinois. Back in 1926, Route 66 (known as the "Mother Road") was the primary cross-country highway from Chicago, Ill., to Santa Monica, Calif. Although the route has been replaced by a modern interstate, portions of the old highway still exist. Along this route, I encountered two concrete bridges: a reinforced concrete beam bridge built in 1921 and still carrying restricted traffic and a concrete arch bridge built in 1915. The concrete on both bridges is in remarkably good condition considering their ages. This issue of ASPIRE TM includes ar ticles about replacing or restoring three old bridges: the Downer Place Bridges from 1909, Jack's Run Bridge from 1924, and Stillwater Viaduct from 1932. The last issue of ASPIRE featured the replacement of the West 7th Street Bridge in Fort Worth, Tex., originally built in 1913—100 years ago. Did the designers and builders of these original bridges consider a service life?—I doubt it because they had this wonderful new material called concrete that would last forever! Fast forward 100 years and we have a lot more options that can be used to produce durable and long-lasting concrete bridges. Are we smart enough to use current concrete technology to replicate what our predecessors accomplished without it? The Strategic Highway Research Program 2 has been investigating service life beyond 100 years and their reports are being published. We should be able to design concrete bridges for at least a 100-year service life. In many aspects, we can learn from the durability studies performed for major bridge crossings in Europe and Asia. Here, service-life design is approached in the same way as structural design. There are loads (environmental conditions) and there are resistances (freezing and thawing resistance, etc.). In the United States, we generally use a deemed-to-safety approach with a prescriptive specification. According to the National Cooperative Highway Research Program Synthesis 441, state specifications for concrete to be used in bridges remain largely prescriptive. All state specifications now permit the use of one or more supplemental cementitious materials (SCMs) in concrete. The use of SCMs contributes to reducing chloride penetration to the reinforcement and is a step in the right direction. In addition, we can add corrosion inhibitors to raise the threshold level before reinforcement corrosion begins. We a l s o h a v e a l t e r n a t i v e c o r r o s i o n - r e s i s t a n t reinforcement that can be used including epoxy-coated reinforcement, metal-clad reinforcement, low-carbon chromium steel, stainless steel, and fiber-reinforced polymers. AASHTO now has a standard practice, PP65-11, that provides a prescriptive approach and a performance approach for dealing with reactivity of concrete aggregates. This again is a step in the right direction. Modern concrete technology provides us with many approaches to use as illustrated by the above examples. Our challenge is to select the appropriate ones to use for a given bridge in a particular location for the desired service life. Please let us know how you are approaching durability and extending service life on your projects. Photo: Ted Lacey Photography. Dr. Henry G. Russell, Managing Technical Editor 2 | ASPIRE , Winter 2014 E D I T O R I A L Editor-in-Chief William Nickas • email@example.com Managing Technical Editor Dr. Henry G. Russell Program Manager Nancy Turner • firstname.lastname@example.org Associate Editors Emily B. Lorenz Craig A. Shutt Art Director Paul Grigonis Layout Design Tressa A. Park Tom Scully Editorial Advisory Board William Nickas, Precast/Prestressed Concrete Institute William R. Cox, American Segmental Bridge Institute Dr. David McDonald, Epoxy Interest Group Dr. Henry G. Russell, Henry G. Russell Inc. Cover Morning mist and sunlight captures the distinct architectural features of the Jeremiah Morrow Bridge, including curved deck overhangs, parabolic bottom soffit, and pier twin wall capitals. Photo: Ohio Department of Transportation Ad Sales Jim Oestmann Phone: (847) 838-0500 • Cell: (847) 924-5497 Fax: (847) 838-0555 • email@example.com Reprints Paul Grigonis • firstname.lastname@example.org Publisher Precast/Prestressed Concrete Institute James G. Toscas, President Postmaster: Send address changes to ASPIRE, 200 W. Adams St., Suite 2100, Chicago, IL 60606. Standard postage paid at Chicago, IL, and additional mailing offices. ASPIRE (Vol. 8, No. 1), ISSN 1935-2093 is published quarterly by the Precast/ Prestressed Concrete Institute. Copyright 2014, Precast/Prestressed Concrete Institute. If you have a project to be con sidered for ASPIRE, send information to ASPIRE 200 W. Adams St., Suite 2100 • Chicago, IL 60606 phone: (312) 786-0300 • www.aspirebridge.org • e-mail: email@example.com American Segmental Bridge Institute Epoxy Interest Group Expanded Shale Clay and Slate Institute Post-Tensioning Institute Precast/Prestressed Concrete Institute AspireBook_Win14.indb 2 12/10/13 12:53 PM