The effect of limestone type and nanosilica on the durability of limestone cement mortars

The influence of limestone type and nanosilica on the resistance of cement to the thaumasite form of sulfate attack (TSA) was systematically investigated. The sulfate attack of mortar specimens was evaluated using visual examination and mass, density and strength measurements. Samples were selected from the surface of prisms after 12 months of immersion and examined using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The results show that the prisms immersed in magnesium sulfate solution all showed signs of degradation. Limestone cement mortar is susceptible to TSA at 5°C. In mortar with high magnesium limestone, the damage was greater than in mortar with calcareous limestone. Prisms with nanosilica showed better performance than non-nanosilica prisms and this seems to be independent of limestone type. No obvious damage was observed in specimens exposed to sodium sulfate solution.