Calcined Low-grade Clays as Sources for Zeolite Containing Material
The continuous development and expansion of a raw material base in response to increasing environmental and technical requirements for most consumable commodities are crucial for the sustainable development of resource- and energy-intensive materials and technologies. As the sources for alkali-activated cements and zeolites, recent studies have reported the suitability of applying calcined clays with various chemical compositions, percentages, and constituent clay minerals and secondary minerals. In this article, the results of a feasibility study on the alkali activation of low-grade clays with 7.26 % montmorillonite/chlorite and 23.14 % kaolinite/montmorillonite minerals are reported. The 6M NaOH activation of clays thermally treated at 700 °C results in the formation of a hardened paste with a compressive strength of up to 5 MPa, with an N-(A)-S-H binder gel and zeolite Na2Al2Si2.5O9∙6.2H2O being the main reaction products.