The Effect of Different Types of Boron Minerals on the Mechanical and Microstructural Properties of Geopolymer Based Mortars

Geopolymer-based materials produced by activating industrial by-products such as fly ash, slag, and metakaolin with alkali activators have engineering properties that compete with Portland cement (PC)-based composites. However, it is necessary to diversify the raw material sources with different industrial by-products to be used more widely compared to the current PC production volumes. In this sense, the evaluation of calcium (Ca)-based colemanite, sodium (Na)-based tincal and both calcium and sodium-based ulexite in cement-free geopolymer mixtures may make these types of boron minerals more valuable than their use in PC-based composites. In this study, research on the mechanical properties and microstructure effects of colemanite, ulexite and tincal-based boron minerals as binders in the production of geopolymers has been studied. In the results, it was observed that the tincal substitution was comparable to the reference mixtures containing 100% slag, although colemanite and ulexite reduced the mechanical properties. Research findings show that tincal is more suitable for use as a substitute than colemanite and ulexite. However, it is thought that boroaluminosilicates should be handled more comprehensively by testing tincal as an alkali activator as well as its substitution as a binder.