Geothermal clay-based geopolymer binders

Significance 

Recent advances in building material technology have favored the development of geopolymers.  Geopolymers are three-dimensional amorphous binder materials. Their excellent binding capability combined with low carbon emission production process put them at the forefront as potential replacements of ordinary Portland cement. Geopolymerzation, the main geopolymer formation technique, involves dissolution of monomers which is crucial for condensation and polymerization. The synthesis of many alternative materials such as fly ash and rice husks rely heavily on the availability of the limited industrial by-product in use, which hinders large scale application in some countries. In this study, clay material obtained from geothermal well drilling sites will be used to develop geopolymers. This clay has a favorable composition of clay minerals, such as alumino-silicates, which possess desirable binding capabilities. More so, little has been reported on the potential applications of geothermal clay.

Researchers from Wuhan University of Technology in China and Michoacan University of Saint Nicholas of Hidalgo in Mexico used alumino-silicates present in geothermal clay for the preparation of geopolymers. Their work purposed to present the potential of commercializing geopolymers as environmentally friendly construction material obtained from industrial waste without intricate pretreatment. Their work is currently published in the research journal, Applied Clay Science.

The researchers commenced the empirical procedure by preparing the kaolinite rich geothermal clay into geopolymer binders. During calcination of the geothermal clay in the preparation process, sodium silicate-sodium hydroxide combination in alkaline activator, and water content effects were observed. The team then characterized the thermal nature of the geothermal clay where characteristics of cristobalite and kaolinite were observed. Eventually, the researchers characterized the morphology, microstructure and measured the mechanical properties of the geothermal clay-based developed geopolymers.

The research team observed that the kaolinite rich geothermal clay possessed higher reactivity than normal clays in geopolymerization. Moreover, the reactivity of the geothermal clay was seen to be enhanced through calcination. Additionally, thermal analysis of the geothermal clay showed analogous behavior as that of kaolinite, but it was affected by the endothermic nature of critobalite. The researchers also noted that by heating at temperatures above 550°C, the compressive strength and microstructure of the geothermal clay-based geopolymers remarkably improved. It was therefore concluded that high water content lead to a porous structure and low compressive strength of the resultant geothermal clay-based geopolymers.

The study successfully demonstrated the synthesis and microstructural characterization of geothermal clay-based geopolymers. In their work, they have shown that kaolinite rich geothermal clay can be synthesized into geopolymers of low compressive strength. As geothermal clay is supposed to be of intermediate dissolution reactivity in geopolymerization, this synthesis might extend the kinds of raw alumino-silicates in geopolymer formation. The study therefore enriches the types of raw aluminosilicates for the synthesis of geopolymers and gives a further understanding on geopolymerization reactions.

Reference

Qian Wan, Feng Rao, Shaoxian Song, Carlos Alberto León-Patiño. Geothermal clay-based geopolymer binders: Synthesis and microstructural characterization. Applied Clay Science volume 146 (2017) pages 223–229.

 

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