Effect of Multiple Environmental Factors on the Adhesion and Diffusion Behaviors of Chlorides in a Bridge with Coastal Exposure: Long-Term Experimental Study

Abstract

Corrosion of steel reinforcement caused by airborne salt penetration into concrete cover is a very important reason for the deterioration of concrete structures exposed to an atmospheric marine environment. The current durability of coastal concrete bridges is an academic and engineering concern worldwide. In this study, three outdoor exposure experiments in the atmospheric marine environments, considering multiple environmental factors, were carried out spanning 4 years to investigate chloride adhesion and diffusion behaviors at the Amatori Bridge of Wakayama Prefecture in Japan. It was found that the distribution of accumulated chlorides on the concrete and steel surfaces is not only time dependent but also space dependent, which is related to the local weather conditions and geography. Note that the annual average wind speed around the bridge site is relatively low (approximately 3 m/s), which is a speed range rarely reported in the existing literature. The relationship between chlorides from airborne salt and chlorides that penetrate into concrete specimens is discussed quantitatively based on a specific tubular collection device (TCD) and the electrometric titration method. It was also observed that chloride deposition increases obviously during typhoons than during periods with no unfavoable weather event. In addition, two groups of mortar specimens were placed under and beside the bridge to explore the influence of seasonal rainfall distribution on the chloride diffusion behaviors in mortar specimens. The research results are expected to determine the priority for the maintenance and management of coastal bridges in Japan.