| Test Plan for Spray Applied Polymer Surface Sealer Study The detailed test plans, project reports and test reports are in the Project Library. In summary, the project began with a user survey and the development of Expert Task Groups and State-of-the-Knowledge workshops at Myrtle Beach, South Carolina on March 1, 2001, Flagstaff, Arizona on September 11, 2001, Washington DC in January 2002 (at TRB), and in Minneapolis, Minnesota on August 21st, 2002. Test projects were placed in Michigan, Arizona, Minnesota and California with a number of different emulsions. The projects were open to any emulsion suppliers who agreed to donate materials and the application of their products. The plan was to reapply the same products on treated and untreated sections at defined time intervals with a variety of testing (including the methods described in the Tests section below) on the test and control sections. Based on early results and the constraints of the projects, the original test plan was modified. Some tests were discontinued, and others added as experimental findings dictated. Test elements added late in the project included friction testing of sanded surfaces, emulsion surface tension, emulsion particle size and Bending Beam Rheometer low temperature testing of mix specimens cut from test cores. The original planned application sequence is diagrammed below. Materials were to be placed at two year intervals, with some new and some overlapping applications, and varying application rates. Planned Application Sequence
The original test plan is given in the table.  Descriptions of the test sites are given below, and the table gives a summary of the treatments. (Construction reports for some of the projects may be found in the Project Library and photos in the Photo Gallery.) Arizona, US 87 (40 miles north of Winslow), application of CSS-1h, Reclamite, Pass QB, ERA-25 and ERA-1 on September 12, 2001. Friction testing was done pre-project and at 1 and 30 days. A second application of CSS-1h, Pass QB and Reclamite was made on October 19, 2006. All the materials were tested on three different surface types: a dense graded surface, a chip seal surface, and an open graded asphalt rubber surface (AR-ACFC). Friction tests with the portable devices and the trailer were done in 2006 a few days after application. Sand was also used on a portion of the 2006 treatments. California Interstate 5 (described as "Marysville, 10 miles north of Sacramento"), application of Reclamite, Pass QB, CQS-1h, CSS-1h and Topein C on 10/25/01. Friction and surface texture data was collected before construction and after 1, 42 and 272 days. California State Route 78 (Salton Sea), application of Reclamite, Pass QB, CQS-1h, SS-1h, and a control section. Each of the products was placed over an asphalt rubber surface. Friction testing was done pre-project and at 1 and 30 days, and cores taken in 2007. Test Site Summary
Minnesota State Route 251 (Maple Island), application of CSS-1h, CRF, Pass QB, GSB Type B, Reclamite, and a control section on August 22, 2002. The Minnesota DOT also placed a chip seal. Additional applications were made in July, 2004 and on September 14, 2006.
Michigan M-35 (Perkins), application of CRF and Reclamite on 8/26/2002, with friction testing before construction and 1 day and 30 days later. Problems were encountered with controlling the field spray application to the specified rates. It is believed this site was covered before further testing could be done. Minnesota, Olmstead County Route 112 was a reconstructed pavement designed as part of an aging study by Western Research Institute. On September 13, 2006 test sections for this study were placed on the new pavement, including Pass QB, Reclamite and LD-7. Sanding was also included as part of the study to determine the effect on short-term friction. The coarse-graded SuperPave surface mix was highly permeable, so all emulsions adsorbed into the HMA fairly quickly. Same day friction testing was run before construction after allowing the applied products to cure. Friction and surface testing was done at all test sites using the portable Circular Texture Meter (CT Meter) ASTM E-2157 and Dynamic Friction Tester (DFT) ASTM E-1911. Some sites were also tested with a conventional skid trailer following ASTM E-274, Standard Test Method for Skid Resistance of Paved Surfaces Using a Full-Scale Tire. Cores were taken at various intervals from some of the projects and sent to the Western Research Institute for extraction and chemical and rheological testing. Samples were also sent to Mathy Technology & Engineering Services, Inc. (MTE) for rheological testing on mix slices. For the 2006 projects, samples were sent to the North Central Superpave Center for lab permeability testing, to the University of Minnesota for a newly developed Bending Beam Rheometer test on slices cut from cores, and emulsion samples to Akzo-Nobel for surface tension and particle size testing. Field permeability testing was abandoned due to the high permeability of the pavement surface. A follow-up Lessons-Learned Workshop was held January 21, 2007 in Washington D.C. with many of the study participants and expert task group members. The lessons-learned reported here are from that workshop. Summary of Lessons Learned: In this study, it became evident there are two different types of fog seal products: sealers that add new asphalt to seal the surface, and rejuvenators that soften age-hardened asphalt to restore desired mixture mechanical properties in the upper 3/8 to 1/2 inch of the pavement surface. Sealers: Sealer emulsions may be used for any number of paving applications, including sealing HMA dense mix from water and oxygen infiltration, recoating raveling open-graded mixes, or tying down loose aggregate on newly applied chip seals. Such products are frequently formulated with polymers or other additives as needs dictate. Although not meant to soften the underlying asphalt, the new binder can serve as a sacrificial layer that has a lower stiffness than the aged asphalt on the pavement surface, thus protecting the underlying surface from further deterioration, especially raveling and top-down cracking. Unlike the clay-stabilized coal tar or asphalt-based sealer products used for driveways and parking lots, this type of sealer needs to infiltrate the surface to provide the desired sealing. In this study, mechanical tests run on thin slabs of mixture indicate that the hardening rate of asphalt near the pavement surface can be slowed with such applications. More specifically, mixture Creep Tests run in torsion mode in a research-grade Dynamic Shear Rheometer (DSR) showed that these treatments had a distinct impact on the evolving flow time (modulus) of the mix and binder in the top 3/8 as the pavement aged, but had little influence below that. Field observations after four years of service showed the treated pavements still exhibited improved impermeability to water and reduced distress. The study participants found the term "infiltrate the surface" applicable to these fog seals. If the newly applied binder lies on the surface without infiltration, tracking and friction may be a problem. In the field studies, there was little problem with tracking of the harder asphalt-based materials, but traffic was kept off of these test sections until the emulsions had broken. These sealers are also especially effective for use on new chip seals in tying down dust as well as retaining chips. Rejuvenators: The second type of fog seal products includes those meant to soften or rejuvenate the aged asphalt. These generally are emulsions of oils meant to replace the oxidized "maltene" fractions in the asphalt, and may again include polymers, asphalt and other additives. The mix DSR testing showed that rejuvenator emulsions can significantly soften the asphalt in the upper 3/8 inch of the pavement surface, as long as the pavement is sufficiently permeable to accept the oil down to that depth. If the pavement is impermeable, the oil may remain on the surface, leaving a surface that may track and/or exhibit poor skid resistance. The study participants found the term "penetrate into the pavement" most apt for these rejuvenator seals. A common laboratory technique for judging the depth of emulsion penetration into the pavement is to cut thin slabs of mix (nominally 0.3 inch) from various depths, extract the binder with an 85:15 blend of toluene and 95% ethanol, and evaluate the extracted binder using conventional rheological test methods. Mixture tests on thin specimens cut from the pavement surface should be used to confirm that the aging binder has in fact been rejuvenated as predicted by the extracted binder rheology, particularly if pavement permeability is low. Rejuvenator emulsions are most useful on oxidized pavements where low temperature mix properties approach critical levels for cracking. However, conventional wisdom regarding the application of rejuvenators is based upon softening the aged asphalt by using blending charts to optimize binder penetration, viscosity, or dynamic modulus G*. If low temperature brittleness causes aged asphalt to crack, then blended properties of aged and virgin binders should be evaluated for relaxation and fracture properties at temperatures where failure occurs. It was noted that the oil-based rejuvenator emulsions without asphalt leave an oily residue on the tops of aggregates where the asphalt has been worn off, lowering friction. Tracking of oil onto unsealed sections was also observed. Thus sanding is strongly recommended for fog seal applications that include only rejuvenator oils. Other emulsions did not track noticeably after curing. However, friction numbers during the first four hours after application were typically doubled for all fog seal products, as long as angular sands were used and no loose surface sand remained. If sand is used, brooming should take place as soon as practical after the emulsion is fully cured. Supplier guidelines for some of these emulsions do not require sanding, particularly when residues are hard or are modified with polymers. The goal of the study was to determine the effectiveness of spray applied sealers. The user survey, the collected laboratory and field data, and the field observations all confirmed that a defined application strategy of fog seals is a cost-effective tool for pavement preservation. More Lessons Learned can be found on each page. | downloadable Documents: (Click to open) Proposal & Work Plan Construction Reports
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
