Prediction of Deterioration of Concrete Bridges

Abstract

In the early 20th century, the general idea was that concrete structures would never show deterioration. However, in the 1990s concrete structures showed an increase in number of cracks and area of spalling. Especially spalling of the concrete cover could create a harmful situation to the users. Spalling of the cover is caused by corrosion of the reinforcement, which leads to expansion and therefore delamination of outer layer of concrete. Corrosion of the reinforcement is caused by the presence of sufficient carbon dioxide and/or chlorides at the reinforcement. Carbon dioxide originates from the atmosphere, and chlorides originate from the de-icing salt that is used to keep the roads free from ice during the winter season. In this research study a method is suggested to determine the development of damage to concrete bridges over time. This method uses physical models to determine the ingress of carbon dioxide and chlorides. Probabilistic techniques are used to determine the damage to concrete structures since the parameters like cover depth is a stochastic parameter. Due to the use of physical models the changes in construction practice over the last decades can be taken into account when the damage to concrete structures is determined. For example, the start of application of de-icing agent (1960s) is taken into account. The result of the predictive model is compared to over 90 inspection results of Dutch bridges, from which was concluded that the proposed model accurately describes the observed damage. From the prediction it was learned that the damage to concrete bridges will double in the coming decades.