Splitting cracks as performance indicator for existing structures

Research Project, 2021 – 2023

Which performance indicators can be used for structures in a changing climate? We cannot rely on past experience alone; instead we must understand and be able to model and quantify the underlying physical mechanisms, in order to be able to predict structural safety in a changing future. Climate change will result in both higher average temperatures and more frost cycles, mainly in areas where many roads will be opened for heavier loads (74 tonnes). The combined effect of corrosion and frost on safety therefore becomes significant. In previous research, one degradation mechanism at a time has usually been studied. However, new results show a strong interaction between corrosion, the main cause of deterioration, and frost. Furthermore, almost all research is based on test samples subjected to accelerated corrosion, while doubts have been raised whether natural degradation affects the structure differently.

In this project, both accelerated and naturally deteriorated samples, with corrosion and frost separately and together, will be studied. Through advanced experimental technologies, such as combined neutron tomography and X-ray, digital image correlation and fiber optics, we will get an insight into the reinforced concrete during the deterioration process, which provides the necessary data for basic understanding. Non-linear finite element analyses will be used, which describe volume expansion of both corrosion and water freezing in cracks, and how these phenomena interact. The influencing mechanisms will be separated, and their combined effects will be explained. The most important parameters will be studied in sensitivity analyzes. The outcome will be a proposal on how splitting cracks can be used as a performance indicator for existing structures. In the end, the project will contribute to significant economic and environmental savings for society, and also to  preserve cultural values, as we with increased knowledge can repair and replace existing structures only when needed, with continued guaranteed structural safety.