AUTHOR=Korat Lidija , Ducman Vilma 

TITLE=Characterization of Fly Ash Alkali Activated Foams Obtained Using Sodium Perborate Monohydrate as a Foaming Agent at Room and Elevated Temperatures

JOURNAL=Frontiers in Materials

VOLUME=Volume 7 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2020.572347

DOI=10.3389/fmats.2020.572347

ISSN=2296-8016

ABSTRACT=Alkali activated foams have been extensively studied in recent years, due to their high performance and low environmental footprint compared to foams produced via other methods. Three types of fly ash differing in chemical and mineralogical composition and specific surface, were used to synthesise  alkali activated (AA) foams. Sodium Perborate Monohydrate (SPM) was added as a foaming agent and sodium dodecyl sulphate (SDS) as a stabilizing agent. Foams were characterized at room temperature and after exposure to an elevated temperature (1000 oC). Densities from 1.2 down to 0.3 g/cm3 were obtained, depending on the type of fly ash and quantity of foaming agent added. Correspondingly, compressive strength ranged from 1 to 6 MPa. After firing to 1000 oC, the density of samples prepared using fly ash with the highest SiO2 and Al2O3 content, i.e RI fly ash, remained approximately the same, while the compressive strength increased on average by 50 %. In the other two types of fly ash the density increased slightly after firing, due to significant shrinkage, and compressive strength increased by as much as 800 %. XRD analysis confirmed the occurrence of a crystallisation process after firing to 1000 oC, which resulted in newly formed crystal phases, including nepheline, sodalite, tridymite and gehlenite.