Alkali activated materials using pumice from the Aeolian Islands (Sicily, Italy) and their potentiality for cultural heritage applications: Preliminary study

In this paper, the potentialities of pumice-based geopolymers have been explored with the aim to evaluate their use as restoration materials. In particular, the behaviour of Aeolian pumice during alkali activation process, either alone or in binary mixtures with metakaolin, has been assessed using sodium hydroxide and sodium silicate activators. Hardened products were characterized by: X-ray diffraction; infrared spectroscopy; thermo gravimetry and electron microscopy. Furthermore, Hg-intrusion porosimetry, water absorption, compressive strength and colorimetric measurements were carried out in order to define the technical features of the produced geopolymers. The results reveal that Aeolian pumice mixed with small quantities (20-30 wt%) of metakaolin is suitable for the formation of lightweight geopolymers which exhibit an accessible porosity up to 30%, water absorption of about 18.0%, and satisfactory 28-day compressive strength up to 12 MPa. These values indicate good breathability and adaptability to the substrates of the proposed formulations. Final products display a homogeneous and compact amorphous matrix, and their colour mimic the original stones, highlighting their potential role in Cultural Heritage preservation. (C) 2020 Published by Elsevier Ltd.