Effect of Particles Morphology on the Mechanical Properties of Aluminosilicate-Based Geopolymers

Geopolymers were obtained by alkaline activation of heat-treated aluminosilicates of the kaolinite subgroup (Al2Si2O5(OH)4·nH2O) with different particle morphologies, namely, platy, spherical, and tubular. Raw platy kaolinite, synthetic kaolinite with spherical particle morphology, and nanotubular halloysite were used. It was found that the morphology of the aluminosilicate precursor and the SiO2/Al2O3 value determine the processes of phase formation in the geopolymerization reaction, which significantly affects the mechanical properties of geopolymers. The maximum compressive strength of the obtained geopolymers increases in the precursors as follows: spheres (43 MPa) < plates (56 MPa) < tubes (85 MPa). The flexural strength of geopolymers in the precursors increases in the following order: plates (6 MPa) < spheres (8 MPa) < tubes (16 MPa). The data obtained will make it possible to obtain functional geopolymer materials with a given set of physicochemical properties.