The first reinforced concrete structures were built at the end of the 19th century. In the early 20th century, when the first concrete bridges were built, the general idea was that concrete made with sufficient cement would prevent the reinforcement from corroding. In these days, it was assumed that an everlasting protective layer would prevent such corrosion. During the 1980s and 1990s, a strong increase in the need for maintenance of concrete bridges was observed in the United States and Great Britain. It is therefore not surprising that in the United States approximately 150 to 200 bridges, of a total of 600,000, suffer partial or full collapse in any year. However, long before a bridge collapses, sections of concrete may come off because of spalling. These loose sections of concrete might already endanger passing traffic. In this paper, "failure" is therefore defined as the undesirable event of an intolerable amount of spalling. The scope of the paper is thus limited to deterioration that results in damage to concrete bridges due to cracks and concrete spalling that is the result of corrosion of the steel reinforcement. This paper introduces a new solution to Fick's second law of diffusion; this solution takes into account both the ongoing hydration of the concrete and the start of application of salt as a deicer in the late 1960s. A new model is used to predict the extent of spalling of Dutch concrete bridges. The outcome of the model is used to validate the results of 92 inspections of Dutch concrete highway bridges.
Abstract