Valorization of aplite in alkali-activated materials.

Geopolymers belong to the broad family of alkali-activated materials that are considered to have much smaller carbon dioxide (CO2) footprint than traditional Portland cements. A wide range of metallurgical wastes are utilized as silicious sources to produce geopolymer components with a prospect of numerous applications in the construction field. At the same time, efforts have been also made to the valorization of aplite rock, which is found to be abundant in Finnvolldalen of Norway and consists mainly of quartz and alkali feldspar, resembling the composition of Na-rich pozzolans. In this framework, the current study focuses on the synthesis of inorganic polymers made of aplite and metakaolin as precursors. In addition, the production of synthetic Na-waterglass is also tested as candidate soluble silica donor in geopolymer systems, through the hydrothermal treatment of aplite. The obtained results confirm that inorganic polymers produced by hydrothermally treated aplite (HTA) and metakaolin (MK) lead to materials with enhanced compressive strength values compared to specimens produced by untreated aplite and MK. At the same time, sodium silicate solution from aplite and commercially available waterglass present similar properties, indicating that aplite can be used as alternative raw material in the production of sodium silicates. [ABSTRACT FROM AUTHOR]