X-ray computed microtomography on cementitious materials: Possibilities and limitations

In order to achieve a fundamental evaluation of durability on the 'engineering level', an extensive investigation of the microstructure on the 'materials science level' should be carried out. Many researchers have been developing microstructure models in order to predict the transport properties and durability properties of concrete. These models are based on, among other things, experimentally gathered knowledge on the hydration of cement, pore structure, porosity and the formation of the microstructure. Collecting full data on the microstructure of cement paste, mortar and concrete is not an easy talk since until now, not one single test method is available to achieve a complete and accurate picture of the real situation. With the introduction of X-ray computed tomography in the study of cementitious materials it became possible to provide a direct 3D reconstruction of the studied material which could be very useful for modelling transport and durability properties. At present the resolution of the reconstruction by X-ray CT is still restricted to a few micrometers, depending on the sample size and the specifications of the equipment used to make the X-ray measurements. However, in spite of these limitations this technique can provide interesting information on different aspects. In this paper some examples of applications will be given : crack formation, study of voids, degradation by means of acid/sulphate attack, ....