Study of Geopolymers Obtained from Wheat Husk Native to Northern Mexico

Abstract

Agro-industrial wastes such as wheat husk (WH) are renewable sources of organic and inorganic substances, including cellulose, lignin, and aluminosilicates, which can be transformed into advanced materials with high added value. The use of geopolymers is a strategy to take advantage of the inorganic substances by obtaining inorganic polymers, which have been used as additives, e.g., for cement and refractory brick products or ceramic precursors. In this research, the WH native to northern Mexico was used as a source to produce wheat husk ash (WHA) following its calcination at 1050 °C. In addition, geopolymers were synthesized from the WHA by varying the concentrations of the alkaline activator (NaOH) from 16 M to 30 M, namely Geo 16M, Geo 20M, Geo 25M, and Geo 30M. At the same time, a commercial microwave radiation process was employed as the curing source. Furthermore, the geopolymers synthesized with 16 M and 30 M of NaOH were studied for their thermal conductivity as a function of temperature, in particular at 25, 35, 60, and 90 °C. The chemical composition of the WHA, determined by ICP, revealed a SiO2 content close to 81%, which is similar to rice husk. The geopolymers were characterized using various techniques to determine their structure, mechanical properties, and thermal conductivity. The findings showed that the synthesized geopolymers with 16M and 30M of NaOH had significant mechanical properties and thermal conductivity, respectively, compared to the other synthesized materials. Finally, the thermal conductivity regarding the temperature revealed that Geo 30M presented significant performance, especially at 60 °C.