X-ray tomography to visualise concrete degradation and (self)-healing

Concrete and stone structures suffer from two major damage problems: surface degradation due to physical, chemical or microbial weathering, and crack formation. It has been estimated that in Europe, 50% of the annual construction budget is spent on rehabilitation and repair of the existing structures. Computed X-ray tomography (CT), a radiological imaging technique, can be applied to study the effect of weathering on the microstructure of the building material. This technique will show loss of material situated at the exposed surface, formation of dense layers with reaction products and changes in internal pore structure. It can also be used to visualise cracks and investigate the efficiency of crack healing applications. A relatively new research domain aims at the development of smart, self-healing materials. Autonomous self-healing implies that the material is engineered in such a way that, upon cracking, the material will sense the damage and heal the crack. In this way the original material properties, such as strength, stiffness, and impermeability, will be largely restored. High resolution CT allows to examine the distribution of capsules with healing agents in the matrix, to visualise rupture of capsules upon crack formation, and to provide 3D images of the healing material that is released into the crack which will allow to judge the crack filling efficiency.