Effects of Silica Fume on the Pore Structure and Properties of Mortars Exposed to Sulphate Aggressive Media

The use of additions as clinker replacement has become very popular, due to the advantages that they provide, especially regarding the improvement of cement industry sustainability. The microstructure of cement-based materials has a direct influence on their service properties. In this research, mortars with different contents of silica fume (up to 10%) have been studied. These mortars were exposed to aggressive media with presence of sodium and magnesium sulphate along 90 days. On one hand, the evolution of their pore structure was characterised using different results provided by mercury intrusion porosimetry technique, such as intrusion-extrusion curves and logarithm of differential intrusion volume versus pore size curves. On the other hand, the compressive strength and the steady-state ionic diffusion coefficient obtained from resistivity of the samples, which was measured using impedance spectroscopy, were also studied. In general, silica fume mortars showed good performance, although the greatest deterioration of these mortars was observed in a mixed magnesium and sodium sulphate solution.