Pavement design engineers specify joint sealants in pavements and slabs to minimize surface water from infiltrating the pavement slab's joint. Their concern is either buildup or even an item harder than the concrete could work itself into the joint and create a point that, over time, would cause spalling or chunks of concrete to break from the joint edges.
This dates back to the beginning of concrete pavement design. But many think it's time to reassess this practice. Procedures for installing slabs and pavements have changed. Contractors are better able to install sturdy sub-bases. The design for lateral reinforcement has improved. Placement technologies are superior to the those used in the 1980s. And mix designs yield a more consistent and stronger material.
It's time to determine whether to continue pavement joint filling, says Scott Eilken, owner of Quality Saw & Seal of Bridgeview, Ill. Eilken is co-chair of a new research initiative that seeks to answer the question of seal or no seal. The Seal/No Seal (SNS) Research Committee formed to determine whether to continue the practice and to provide a cost analysis of the current requirement to seal pavement joints.
The committee includes concrete contractors, sealant suppliers, research engineers, and owners. They represent the entire group that is responsible for sealing and maintaining pavement joints and cracks across the nation.
The study comes at an important time. In December, Brian McCarthy, Portland Cement Association president and CEO, gave some reasons for renewed optimism in “Cement Outlook: Turnaround in 2010 Signals Return to Sustained Growth.” He cited the potential growth of concrete pavement as one reason for optimism.
There is a paradigm shift in the cost of building concrete roads versus asphalt roads. Owners now recognize that concrete is not only a more durable solution for building roads, it is also less costly, both for the long term and for the initial investment, McCarthy said.
Proving that the practice is unnecessary would help ensure that this cost differential remains. “As cost pressures continue, there is increased interest in eliminating transverse joint sealants as a means of lowering the cost of concrete pavements,” says Eilken.
There is support for this research. ACI Committee 325's document, “Guide for Design of Jointed Pavements for Street and Local Roads,” states that for low-volume roads and city streets with short joint spacings, opinions vary on the effectiveness of joint sealing. But for long joint spacings and for highway pavements with high truck volumes, the document recommends the practice only where local experience has shown a benefit. It suggests that “joint sealants may not be cost-effective in dry climates.”
The SNS committee has contracted with Soil Mechanics Engineers to conduct profile testing of several Federal Highway Administration sites. Also, the states of Colorado, Florida, Ohio, and Minnesota have agreed to conduct profile testing of the FHWA sites constructed in those states.
The study plans to establish new test sections to evaluate different joint sealing features and address the seal/no seal question for both dowelled and un-dowelled pavements in all environmental zones.
As part of the effort to construct new test sections, the first project is underway on State Route 59 near Joliet, Ill., which includes building four lanes through an urban area with curbs and gutters, along with intersections. The project, comprised of a 9 ¾-inch-thick dowelled portland cement concrete pavement placed on a 12-inch base, includes building eight sealed and two unsealed sections. Joints are spaced 15 feet apart.
The two southbound lanes will be constructed first and are the location of the sealant experiment. The design consists of sealing the longitudinal and transverse joints with hot pour and silicone sealants. The transverse joint sealants will be installed in two joint geometries—a single saw cut and reservoir cut. The longitudinal joints will only use a narrow joint geometry. The test sections are complete. The northbound lanes, which are not part of the sealant experiment, will be built in 2010. Walsh Construction is building the roadway and Quality Saw and Seal is constructing the joint experiment.
To learn more about the SNS committee, contact Eilken of Quality Saw and Seal at 708-728-1895 or Charley Grady of CRAFCO at 602-363-5519.