Study of Geopolymer Composites Based on Volcanic Ash, Fly Ash, Pozzolan, Metakaolin and Mining Tailing

This work studies the feasibility to employ a combination of volcanic ash (natural waste) with different raw materials in the production of geopolymers: fly ash and mining tailing (considered hazardous solid waste), natural pozzolan, and metakaolin. This study compares the properties of geopolymers based on volcanic ash with fly ash, pozzolan, metakaolin, and mining tailing in a relation of 1:1 with the addition of NaOH 15M and Na₂SiO₃ as alkali activators. FTIR and XRD assays and mechanical tests were employed to characterize the geopolymers. The results showed that those materials can be used as raw materials to produce geopolymers. Additionally, the results revealed that prime material composition and their mineralogical characteristics influence the geopolymerization reaction and compression strength, reaching values of 35 MPa for the volcanic ash-pozzolan mixture. The pozzolan is a good source of Al₂O₃ and SiO₂ and is highly reactive to the alkali activators resulting in a better geopolymerization in comparison to the mixtures of volcanic ash with metakaolin, fly ash, or mining tailing.