Abstract

State departments of transportation use bridge deck overlay systems to prolong bridge deck service lives. Consisting of a thin layer of material applied to a concrete bridge deck surface, overlays form a protective barrier that improves ride quality, protects embedded reinforcement from harsh environmental conditions, enhances structure durability, and improves deck drainage. Over the past 20 years, the Kentucky Transportation Cabinet has made significant investments in overlays, rehabilitating nearly 5,000 bridge decks with them — roughly 1/3 of all bridges statewide. Given the significant investment in overlays, and the fact they degrade over time — eventually re-exposing bridge decks to harsh environmental conditions, — it is critical to understand what factors influence their performance and condition. This study sought to identify predictors or metrics that can account for variability in overlay performance throughout Kentucky and support accurate forecasting of future conditions. Using data from the Cabinet’s Bridge Management System, along with field inspections, chloride analysis, and imagery captured with a forward looking infrared (FLIR) camera, researchers attempted to identify statistical relationships between variables such as crack width/depth, crack length, average daily traffic, and amount of deck patching, and overlay condition. Limited by the constraints of a small data set (93 bridges), researchers did not uncover robust statistical relationships. Analysis found, however, that epoxy overlays exhibited the least linear cracking as well as the narrowest cracks. Asphalt overlays had the least amount of deck patching, but generally suffered from the deepest cracking. Epoxy overlays were in the best condition overall. The FLIR camera has utility for taking photos of bridge decks, however, image capture must occur under very precise conditions (e.g., no traffic, favorable weather) and image interpretation must be done by trained experts.

Report Date

9-2025

Report Number

KTC-26-01

Digital Object Identifier

https://doi.org/10.13023/ktc.rr.2026.01

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