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cracks will continue to expand until that surface seal doesn't really cover them and prevent the intrusion of the chlorides." Hunter says INDOT has really struggled with expansion joints. "I'll talk to the construction people about it and I'll talk to our asset managers about it, and they'll say they felt like the contractor really went above and beyond doing the best job they possibly could. But, we still get these failures, simply because it's so hard to replace an expansion joint. It has been one of the biggest issues." Iowa Department of Transporta- tion Bridge Preservation Engineer, Gordon Port, echoes the troubled experience with expansion joints. "We're in the process right now of trying to replace some expansion joints because they almost always leak at some point in time," he ex- plains. "That causes deterioration of substructures and even superstruc- tures, and the corrosion of steel beams. Particularly of concern to us, is that you can always blast and clean a steel beam, but when you get precast or prestressed concrete beams that get moisture in them and you get corrosion—that's a little more challenging." Port says Iowa's top preservation activity is installing high-density polymer concrete overlays, where 1/4-inch of the surface is milled off and 1 1/2-inches of overlay is added. "We've been using these since the 1970s, and that's probably been our most effective long-term preservation activity. It probably wasn't thought of as preservation back then, but it definitely extended the time before additional work was needed on the decks." For the North Carolina Depart- ment of Transportation's Division 1, which is the northeast corner of the state extending to the Outer Banks, latex modified concrete with hydrodemolition preparation is the preservation technique of choice. Latex modified concrete is a hydraulic cement with aggregates added when mixed with a latex emulsion. It was designed in the late 1960s and is essentially a wa- terproofing compound that reduces porosity. RK&K Consulting Engineer and NCDOT Division 1 Resident Engineer, Jeff Thatcher. says it's providing mixed results in his expe- rience. "The consistent challenge is we're using these new technologies like latex modified concrete and we end May 2016 | EquipmentWorld.com 70 better bridges | continued Montana DOT workers place a latex- modified concrete overlay on the Clark Fork Bridge. Image: Montana DOT