Investigation the role of aluminosilicate fibers in the microstructure and mechanical properties of geopolymer composites

In this research, metakaolin-based geopolymers reinforced with aluminosilicate fibers were investigated at room temperature and after exposure to 700 oC. Geopolymers were synthesized from metakaolin, micro silica and potassium hydroxide. The different molar ratios of silica to alumina and water content were studied. 1, 3, 5 and 7 weight percent of aluminosilicate fibers were added to the geopolymer composition. The mechanical strength and microstructure of the samples were studied. The results showed that the flexural and compressive strength values of the optimal sample at ambient temperature are equal to 5.87 and 19.05 MPa, respectively. By adding 5 wt% aluminosilicate fibers, the maximum of flexural and compressive strength values were obtained. However, by heating the composite samples at 700 oC, flexural and compressive strength values were 10.34 and 17.86 Mpa, respectively. Decrease in the mechanical strength at 700 oC is due to the strong chemical connection between aluminosilicate fibers and geopolymer binder during the heat treatment.