Use of neutron radiography and tomography to visualize the autonomous crack sealing efficiency in cementitious materials

Penetration of moisture into building materials is at the origin of several damage mechanisms. In the case of cement-based materials crack formation is a common problem and highly accelerates the ingress of water and aggressive substances. Crack repair may be needed, however, repair works are expensive and in some cases cracks are even not accessible. Therefore, in this research we aim at autonomous crack sealing. Upon crack appearance, damage is sealed autonomously by the release of encapsulated agents. Visualization of the water uptake by means of neutron radiography for samples with manually and autonomously sealed cracks showed that in both cases ingress of water into the crack can be prevented depending on the type of agent. The efficiency of three different agents was examined and it was shown that the use of polyurethane or a water repellent agent were most promising. Neutron tomography scans demonstrated that poor results were obtained when encapsulated methyl methacrylate was used, since one component of the agent hardened inside the capsules before crack appearance. From the results we can conclude that autonomous sealing of cracks is feasible and that neutron radiography and tomography are suitable non-destructive test techniques to visualize the autonomous crack sealing efficiency.