Suitability of alkali activated materials using tuff for cultural heritage applications: preliminary study

In this paper, the suitability of tuff-based alkali activated materials have been explored to validate their use as restoration materials. In particular, the behavior of two different tuffs, chabazite- and clinoptilolite-rich, used in mixtures with metakaolin (CH_MK and CL_MK respectively), has been assessed using sodium hydroxide and sodium silicate as alkaline activators. Hardened products were characterized by: X-ray diffraction, infrared spectroscopy and thermogravimetry. Mineralogical characterization confirmed the occurrence of the alkaline activation and FTIR spectra showed the absorption bands typical of the amorphous structure of aluminosilicates as further confirmation of tuff interaction with alkaline activators. To define the technical performance of the alkali activated binders, water absorption under vacuum, open porosity and capillary absorption was measured in accordance with European Standards’ prescription. Finally, all the produced samples were compared to traditional products such as pozzolana and cocciopesto lime-based binders. The results of the chemical-physical characterization (Figure 1) proved that, both the alkali activated tuff-based products, are compatible with the existing historical materials and also with the traditional repairing mortars.