Characterization of DEF affected concretes: detection and modification of properties

The evolutions of the different physicochemical and mechanical properties as a function of the expansion due to Delayed Ettringite Formation (DEF) in concrete are studied. In comparison of sound materials, some characterizations were made in accordance to the level of expansion: in the initial time, in the latent period, in the accelerating phase and at the end of expansion. The characterization was as follows; SEM analysis was used to observe the presence of DEF. Physical tests linked to transfer properties; gas permeability and electrical resistivity were measured to detect micro-cracks generated by the DEF advancement. To observe the impact of micro-cracks, compressive strength and static modulus were experimentally determined. It was observed that few tests can be used to detect theses pathologies earlier, during the latent period. Gas permeability, electrical resistivity and elastic modulus results were promising. These tests are very sensitive to the development of micro-cracks generated in the concrete by the development of swelling due to DEF.