The potentiality of volcanic ash from 2021 Cumbre Vieja Eruption (La Palma, Canary Islands, Spain) as starting material for the alkali activation process.

The latest eruption of the Cumbre Vieja volcano (La Palma, Canary Islands, Spain), started in September 2021 and lasted about three months, ejected huge quantities of volcanic ash that blanketed the surface of the entire island, reaching considerable thicknesses where closest to the eruptive centre and causing serious damage to residential areas and local cultivations. These natural deposits are considered as a difficult waste to dispose of. Recent works proved volcanic ash as an excellent starting material in the production of Alkali Activated Materials (AAMs) (Barone et al., 2021; Occhipinti et al., 2022). This work aims to study the potential employment of Cumbre Vieja pyroclasts as precursor for the geopolymerization process, making them suitable in the construction field in the view of promoting the circular economy system. For this reason, samples collected from different sites of the island were characterized to determine their mineralogical and chemical composition before to be used as raw materials. Mixtures of this precursor alone or in binary blends with metakaolin have been tested, with the aim to produce cementitious binders. Sodium hydroxide (8M) and sodium silicate solution have been used as activators. Lightweight geopolymers have been also prepared by the addition of foaming agents. AAMs were subjected to X-Ray Diffractometry, FT-IR spectroscopy, Scanning Electron Microscopy and uniaxial compressive testing for a complete mineralogical, textural and physical-mechanical characterization. 3D micro-structure was investigated by synchrotron light computed microtomography at micron scale that provided precise information on the abundance, morphology, and connectivity of the porosity and how it affects the overall structure of the AAMs. Preliminary results evidenced that Cumbre Vieja ash can be efficiently employed as raw material in the geopolymer production, which represent a promising alternative to the conventional building ones with great potential in the construction field.