Characterization of the degradation of self-compacting concretes in sodium sulfate environment: Influence of different mineral admixtures

The effects of the type of mineral addition on the behavior of SCCs in sodium sulfate environments were studied. Three strength classes (30 MPa, 50 MPa and 70 MPa) and three different mineral additions were investigated: limestone filler, fly ash and natural pozzolan. The results were compared to those of vibrated concretes. Compressive strength, mass and dimensional changes dues to sodium sulfate attack were determined. The microstructure was studied using SEM–EDS and XRD analysis. For 720 days of immersion in 5% Na2SO4 solution, the penetration depth of sulfate in different samples was quantified using SEM–EDS. The results were consistent with those of XRD analysis. This study shows the benefic effect of the incorporation of a natural pozzolan as a mineral admixture in SCC on the resistance of these concretes in sodium sulfate medium. SCCs with natural pozzolan present characteristics very comparable with those of SCC mixtures with fly ash. It appears that the use of vibrated concretes or SCC with limestone filler, especially with low compressive strength, in a rich sodium sulfate environment is not recommended.