The Swedish Fortifications Agency’s (FORTV) property stock consists of numerous concrete structures built both above and below rock. Some of these structures have experienced cracking overtime which, in turn, can lead to subsequent problems such as reinforcement corrosion and deterioration of structural performance. Due to the fact that in many cases there are building requirements related to protection against forced entry and weapon attacks, it is of great importance for FORTV to gain an understanding of how cracks are developed, the significance of the crack development, how do cracks affect the performance, as well as how cracks can be remediated. A similar project, with a focus on so-called access protection, has earlier been managed by FORTV. During the project, it was ascertained that there is inadequate knowledge pertaining to crack repair.

The goals of this project were the following:Suggest a method or a tool to evaluate the extent of cracking in concrete structures which are included in protective facilitiesDescribe which parameters can initiate cracking.Describe repair methods to reinstate the functionality of concrete structures.

Cracking naturally takes place during the normal use of a concrete structure without influencingthe structure’s functionality given that it is designed correctly. However, there are other mechanisms which can initialize cracking in concrete structures. These mechanisms take place during various time periods (hardening, after hardening andduring the service life). Three crack groups have been identified accordingly: a) cracks due to poor workmanship, b) cracks due to chemical deterioration mechanisms and c) loading cracks.

Damage identification and a condition assessment can be conducted in different stages to determine the extent of cracking. It is firstly recommended to review the existing documentation coupled to the structure, followed by a preliminary inspection (visual), additional non-destructive testing and lastly destructive testing. Repairs are selected according to the source of the damage, it is to say concrete defects or corroded reinforcement. In addition, the functionality requirements for the structure shall be evaluated and the selected methods shall be assessed according to e.g. lifespan and cost.