Abstract
The mineral and chemical composition of aluminosilicates used in geopolymer systems is critical for optimal structure formation and the overall performance of the geopolymer products. The composition of alumosilicates can be altered during the technological processing, especially, at the stage of fine milling. This study investigated the effect of aluminosilicate contamination with Fe from milling yield, the characteristics of the aluminosilicates with a metal lining, structure formation, and hardened properties of geopolymers based on different natural and technogenic persilicic aluminosilicates. The formation of Fe-phases due to milling yield was detected by the XRF analysis and the XRD investigation revealed the formation of nanosized ferrous hydroxide or bernalite Fe(OH)3(H2O)0.25. The volume of an elemental cell of the nanosized bernalite per Fe atom is 4.5 times larger than that of the metallic iron. This results in the disintegration of the matrix, which was observed by SEM and then confirmed by reduced strength performance of geopolymer composites. Based on this study, the negative effect of Fe-phases from milling and nanosized ferrous hydroxide on structural characteristics and service performance of geopolymer composites based on natural and technogenic raw materials was concluded.
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