Thin Polymer Overlays On Bridge Decks PDF Download

Bridges in Kansas are exposed to winter conditions, including deicing chemicals used to keep the roads and bridges clear of ice and snow. These chemicals and water are harmful to the concrete and the steel reinforcing bars used in bridge structures. The objective of this study was to develop a durable thin bonded overlay with chloride resistance to protect the reinforcing steel of the bridge deck. Overlays were developed and monitored after their initial placement on four bridges. The overlay materials selected by the Kansas Department of Transportation (KDOT) had promising results from laboratory testing. Four different overlay materials were selected based upon KDOT's laboratory results and were tested on four separate bridge decks. Three of the bridges are located in Greenwood County and one in Sedgwick County. All four bridges were new construction; the three in Greenwood County are pre-stressed concrete girder design and the Sedgwick County Bridge is a steel girder design. The data from the testing and monitoring were used to determine if there are benefits to using thin bonded overlays for bridge deck wearing surfaces and which types of thin bonded overlays have the largest benefits. The materials chosen for the overlays were: Type IP cement concrete, Type IP cement with 3% silica fume concrete, Type I / II cement with 5% silica fume and polypropylene fibers concrete, and Type II cement with 5% silica fume and steel fibers concrete. Construction samples and bridge deck cores were tested for compressive strength, permeability, chloride concentration, overlay adhesion, and cracking resistance. The permeability tests showed the overlays containing the Type IP cement were the least permeable while the steel and polypropylene fiber overlays were the most permeable. The Type IP cement overlays meet the design specification of passing less than 1,000 coulombs (1.5 inch thickness); however, the overlays with the fibers do not. The ability of each overlay to resist chloride ion migration will only truly be known as 'in service' time accrues. Based upon the chloride ion contamination after five years, all overlays would appear to be functioning equally unless there is cracking in the overlay.