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24 Bond strength tests were performed in February 2006. years. Carter (8) states that TPOs properly applied can pro- The thicknesses for the deicing overlays were 12 mm (0.49 vide service lives of up to 20 years, but that maintenance will in.) and 11 mm (0.46 in.), whereas the epoxy overlays were be required if the surface is intended to remain free of defects. 2.5 mm (0.10 in.). The bond strengths were 1.41 and 1.50 MPa (205 and 218 psi) for the deicing overlays and 1.59 and 1.89 MPa (230 and 274 psi) for the epoxy overlays. The per- WARRANTIES meabilities to chloride ion when tested in February 2006 were 23 and 246 coulombs for the deicing overlays and 1,226 Alberta and 1,367 for the epoxy overlays. In the Province of Alberta, each TPO contract requires a The bare tire skid numbers for travel lanes on the bare 5-year warranty signed by both the contractor and material concrete were 27 and 28 in June 2004 before the deicing supplier (8). Bankruptcy of either party leaves the other party overlays were installed; in October 2005, after overlay wholly responsible. The warranty covers failure of the wearing installation, the skid numbers were 59 and 60. In December surface exposed to normal traffic; it does not cover failures of 2005, the numbers dropped to 46 and 53 for the deicing over- the substrate. Repairs of distress that occur after the work was lays. For the epoxy overlays, the skid numbers were 22 and approved by the province are required to be made at the end 26 before overlay installation in June 2004. In the October of the 5-year period, except that large failures, defined as more after installation, the numbers were 57 and 49. No values than over 5% of the deck, must be repaired within 60 "good were reported for December. weather days" of notification, regardless of when the accu- mulated 5% distress developed. Carter (8) notes that this has Inconclusive results were obtained for ice and melting happened only twice. Even with the warranty, the contractor's snow performance on I-81 because insufficient ice and snow work is subject to approval by the province, and the contractor events had occurred at the time of the evaluation (43). is compensated only for work that has been approved. Smart Road Overlays LaGuardia Airport, New York Permeability and bond tests were not reported for the Smart The warranty used in the construction of LaGuardia Airport Road overlays. Skid tests were performed in November and is shown in Appendix C. The warranty was executed jointly December 2006 and January 2007. All skid numbers were by the material supplier and the contractor. The warranty 57 or higher. required that the contractor repair any defects that occurred within 5 years of installation. Snow was applied artificially to the Smart Road overlays. Friction tests were performed on the pavements: 4 passes on dry surfaces, 8 with snow, 4 after the first plow, and 12 after the RELATIVE COST second plow. Five snow experiments using artificially applied snow and one using artificial "black ice" were conducted. Sprinkel (4) reports that the cost of epoxy overlays, based on 1994 and 1995 bid tabulations in Virginia, was 25% of The results of the tests using artificial snow indicated that the hydraulic cement concrete overlays based on total initial both deicing and epoxy overlays would improve the fric- cost, and 36% if based on life-cycle cost assuming a 15-year tion of bare, tined concrete pavements or bridge decks in life for the epoxy TPO and 30-year life for the hydraulic the early stages of a snow storm before the snow removal cement concrete. However, the life-cycle cost for the epoxy equipment can arrive. However, no consistent conclusions is even lower if a 25-year life is assumed. could be drawn after the initial plowing for the snow and traffic conditions occurring during the tests. The difficulties Kansas DOT reported that the cost of milling and placement encountered in obtaining a uniform coverage with "natural" for TPOs between 2001 and 2008 was about 20% less than for quality snow and accurately defining the location of the fric- silica fume overlays. Traffic control costs are much lower for tion measurements precluded more accurate comparisons of TPOs because of the much shorter cure time (5 days versus performance of the two overlay systems (43). 2 days) and the elimination of overnight lane closures. For a four-lane structure, traffic control for a TPO would be approxi- mately 12% of that required for a silica fume overlay (44). SERVICE LIFE Sprinkel (4) states that projections suggest that, with the SPECIFICATIONS exception of the methacrylate slurry and the multiple-layer polyester overlays, TPOs constructed in accordance with National organizations have prepared three specifications AASHTO specifications (6 ) should have a service life of 25 for the installation of TPOs:
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25 1. Guide Specifications for Polymer Concrete Bridge 3. Specification for Type ES (Epoxy Slurry) Polymer Deck Overlays, AASHTO-AGC-ARTBA Task Force Overlay for Bridge and Parking Garage Decks, An 34, Washington, D.C., 1995 (6 ). ACI Standard, Reported by ACI Committee 548, ACI 548.9-08, American Concrete Institute, Farmington, 2. Specification for Type EM (Epoxy Multi-Layer) Poly- Hills, Mich., 2008 (45). mer Overlay for Bridge and Parking Garage Decks, An ACI Standard, Reported by ACI Committee 548, ACI 548.8-07, American Concrete Institute, Farm- ington Hills, Mich., 2007 (2).