Geopolymers based on natural perlite and kaolinic clay from Morocco: synthesis, characterization, properties, and applications

Abstract This research focused on the elaboration of geopolymers based on natural Moroccan perlite at room temperature by adding calcined Moroccan kaolinic clay as a source of reactive alumina. The amount of calcined kaolinic clay ranged from 0 to 50%. A mixture of sodium silicate and sodium hydroxide was used as an alkaline activator. The calcined kaolinic clay effect on the physicochemical and microstructural properties of synthesized geopolymers was evaluated using several analytical techniques, such as compressive strength tests, P-wave velocity, density and porosity, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The outcome showed that the 10% calcined kaolinic clay addition leads to improvement in the physicomechanical properties and results in a geopolymer at room temperature with interesting physico-chemical characteristics at the age of 28 days. Incorporation of more than 10% calcined kaolinic clay favored the zeolites appearance (phillipsite and Na-faujasite) in the geopolymer matrix forming a heterogeneous microstructure, which led to the decrease of the mechanical properties of the synthesized geopolymers. These properties support the use of synthesized geopolymers as a good substitute for conventional construction materials (natural stones, stabilized soils, fired clays, and cement mortars).