The immobilisation of heavy metals from sewage sludge ash in geopolymer mortarsMateusz Sitarz, Tomasz Zdeb, João Castro Gomes, Erick Grünhäuser Soares and Izabela HagerMATEC Web Conf., 322 (2020) 01026DOI: https://doi.org/10.1051/matecconf/202032201026