A Procedure for Determining ``Performance of Thin Polymer Overlays on Alberta Bridge Decks
P. D. Carter
Appears on pages(s):
Bridge decks; chlorides; corrosion; cracking (fracturing); durability; freeze-thaw
durability; polymer concrete
This paper reports on the overall field performance and some of the lessons learned from more than 100 thin polymer overlays in the province of Alberta, Canada. These overlays were applied between 1985 and 1995 as maintenance work to existing concrete decks, where it was thought that protection against moisture and chloride absorption was needed to reduce the rate of bridge deck deterioration. The paper is intended to answer the basic question what has been learned from ten years of thin overlay experience? Two measures of field performance are presented on overlays in service for up to ten years with special attention to overlays aged from eight to ten years. Various types of polymer overlay failures are discussed. The reported field performance suggests that different proprietary polymer overlay materials have varying degrees of resistance to degradation by ultraviolet radiation. The physical properties of the proprietary overlay materials change with time and exposure conditions. The materials appear to lose flexibility and compatibility with concrete at diiering rates. Field performance indicates that the type of aggregate used in the thin overlay systems also affects the overlay performance and compatibility with concrete. The aggregates contribute significantly to the durability of the overlays. Workmanship, as reflected by contractor experience, is shown to be a significant service life factor. Field experience shows that polymer overlays have been effective in increasing the durability of non-air-entrained concrete exposed to aggressive environments, but the effectiveness was reduced when reflective cracks propagate from the deck through the polymer overlay. Most bridge deck cracks have not reflected through the overlays after eight to ten years in service and remain sealed by the polymer overlays. Reflective cracks are different from most bridge deck cracks in that they require special repairs to prevent propagation through the overlay within a period of several years.