Real time 3D monitoring and modeling of frost damage in concrete and sedimentary rocks

Contact: Maxim Deprez

At middle to high latitudes, frost weathering is one of the main causes for the degradation of porous building materials, such as natural building stones and concrete. Despite a lot of research and several developed theories, direct evidence which reveals the mechanisms behind the damage done by ice crystallization is still lacking. Determining these mechanisms is essential in order to produce better assessments of damage prevention and of the conservation of cultural heritage.

To solve this question, it is necessary to have a full understanding of the behaviour of the investigated material in frozen conditions for both macro and micro scale. The macro-scale properties (open porosity, permeability, compressive and tensile strength) and behaviour are determined by European standard tests. To do micro-scale experiments, it is essential to be able to look into the pores. This is where micro X-ray tomography comes into play. With the EMCT at the UGCT facility, it is feasible to do dynamic scans, which means the sample can be imaged in a temperature controllable cell, and multiple X-ray scans can be taken during cooling. Currently, the minimal scan speed with this equipment is 12 seconds per scan, and the maximal spatial resolution is about 5 µm.

In reality, however, building materials are usually prone to compressive or tensile stresses. These stresses could influence the susceptibility of the material to frost. To make a correct assessment about these possible changes, it is interesting to perform dynamic CT scans with the sample under a certain loading. Therefore, the temperature controllable cell can be replaced by an X-ray transparent cell which is able to perform compression and tensile strength tests on the sample while controlling the temperature. This way, frost and external stresses can be applied in one setup.