Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/291564
RoadScience 6 April 2014 Better Roads "A valid question within the industry regards how well sealants work to improve pavement performance," APCA says. "That question remains largely unanswered and is the crux of the issue of whether to seal or not seal concrete pavement joints." State DOTs are "getting into the act" of placing no-seal test sites, ACPA says. "Many are simply omitting sealant from por- tions of a project," it reports. "These sections are candidates for [a] comprehensive study. After sufficient time and ex- amination, the results will establish the link between sealing joints using modern materials and pavement performance." There is no such issue with asphalt pavements, Eilken says. "We know there are a thousand reports that show the value of crack sealing in extending the lives of flexible pavements," he tells Better Roads. "We needed to answer that same question regarding concrete pavements." The missing link is research, ACPA says. "For years, research associated with sealant technology has been predicated upon the assumption that sealants contribute to pavement perfor- mance," ACPA notes, and that's colored the results. "Unfor- tunately, this assumption has directed research in a way that has left very little tangible evidence of the impact of sealants on overall pavement performance. Similarly, much of the evolutionary work with sealants was made on older pavement designs and with older sealing materials." Wisconsin DOT is the only agency to provide compre- hensive information on the impact of sealing to overall performance, ACPA says. However, ACPA says no one knows if WisDOT's conclusions are valid elsewhere. "Their original research needs to be expanded to a national scale to quantify differ- ences across various climatic con- ditions, soil conditions, concrete designs, pavement designs, ap- plications, [and] modern sealing materials," the association says. Sealing for thee, but not for me While Wisconsin DOT does not seal its high-level, high-speed concrete pavement joints, it's per- mitting matching funds for joint sealing on local, slower-speed, lower-level pavements if the local agency so decides. Research indicates that higher-speed traffic functions to suck fine aggregates, incompressibles and debris out of the joints but doesn't work that way for slower-speed roads, Eilken says, and interest continues in sealing joints in slower- speed, local agency applications. To this end, Eilken traveled to Wisconsin in February to describe best practice for joint sealing at a workshop of the Wisconsin Concrete Pavement Association. Wisconsin's new spec, 4-21.6 Cleaning and Sealing Joints, dated July 2013, unequivocally precludes sealing concrete joints, except only on "projects on local highways where joint seal- ing has been requested by the local government and approved by WisDOT," the specification provides. "WisDOT no longer allows the curing, sealing or filling of joints in concrete pavement on highways under their jurisdic- tion," the spec continues. "Local streets and roads for which WisDOT has project administration responsibility only (no project financing) may have joints sealed if the local govern- ment has expressed a preference for sealing and WisDOT has concurred." WisDOT's rejection of joint sealing notwithstanding for local use the DOT provides a textbook elaboration of joint sealing best practice. "Proper cleaning of the joints is essential if a long lasting seal is to be obtained," the DOT urges. "In all cases, the cut should be blown clear of dirt and should be dry before sealing. The saw cut is cleaned with compressed air or pressurized water. Be sure there is no oil Diamond blade wet sawing widens and washes transverse crack control joints prior to sealing. Photo courtesy of Seal/No Seal Group