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This interim report presents the results after 5 years of a study undertaken to evaluate multiple layer polymer concrete overlays over a 10-year period. The report indicates that an overlay of low permeability and high skid resistance can be successfully installed by a contractor or by state or federal labor forces with a minimum of disruption to traffic. With one exception, the initial condition of the I0 overlays that have been evaluated since 1981 was good to excellent from the standpoint of permeability, skid resistance, and bond, although some overlays were better than others. Also, with one exception, the overlays were in good to excellent condition after one year in service, but the permeability had increased and the bond strength and skid resistance had decreased significantly. Although evaluations made at 3 years and 5 years of age showed a continuing decrease in skid number and bond strength and an increase in permeability, three overlays near Williamsburg had an acceptable skid number and permeability at 5 years of age, but these overlays can be expected to delaminate further at an age of 5 to 10 years, because the concrete surface was not properly prepared prior to placing the overlays and because moisture, temperature change, and traffic deteriorate the bond interface. Multiple layer polymer overlays constructed in accordance with the special provision of March 1987, can be assumed to have a useful life of 10 years and to provide an economical alternative for extending the life of decks for which maintenance should be done during off-peak traffic periods.
The Iowa ultra-thin project demonstrated the application of thin portland cement concrete overlays as a rehabilitation technique. It combined the variables of base preparation, overlay thickness, slab size, and fiber enhancement into a series of test sections over a 7.2-mile length. This report identifies the performance of the overlays in terms of deflection reduction, reduced cracking, and improved bonding between the portland cement concrete (PCC) and asphalt cement concrete (ACC) base layers. The original research project was designed to evaluate the variables over a 5-year period of time. A second project provided the opportunity to test overlay rehabilitation techniques and continue measurement of the original overlay performance for 5 additional years.
The installation of thin polymer concrete overlays on five bridges on I-85 near Williamsburg, Virginia, has demonstrated that an overlay of low permeability and high skid resistance can be successfully installed by a contractor with a minimum of disruption to traffic of approximately eight hours per lane. The initial condition of the overlays was excellent from the standpoint of permeability, skid resistance, and bond, although some overlays were better than others. All were in good to excellent condition after one year in service, but the permeability had increased and the bond strength and skid resistance had decreased significantly. Based on the data collected during the first year it is projected that the overlays constructed with LB183 resin will have a useful service life of at least five years and that the MMA overlay will fail in less time.