PROPERTIES OF PHOSPHORUS-CONTAINING GEOPOLYMER MATRIX AND FIBER-REINFORCED COMPOSITE

In this work properties of geopolymer matrices based on silica fumed prepared with different alumina sources and phosphoric acid were discussed. To evaluate the pot-life of geopolymer resin at room temperature, the viscosity of geopolymer resins was coherently measured. Matrices were analyzed by means of XRD, FTIR ATR, SEM-EDS, Al-27, Si-29 and P-31 MAS NMR. Thermodimensional stability of fiber-reinforced composites was measured by dilatometry. Water resistance was tested in boiling water; chemical composition and NMR spectra of treated geopolymer matrices were analyzed. The nature of the alumina source influenced the mechanical and thermomechanical properties of the matrix. Although the phosphorus added enhanced the dimensional stability of geopolymer matrix/composites at high temperature, more than 50% of phosphorus was soluble and washed out of the matrix during boiling in water. The rest of phosphorus was probably bound to geopolymer or adhered to silica fumed particles. Still, the amounts of soluble SiO2 and Al2O3 were rather low and the total Si/Al ratio in the matrix remained constant. Properties of fiber-reinforced composites with 40-65 wt % of fiber were influenced more by fiber used than by the matrix. In contrast to an E-glass composite, which is brittle, a basalt fiber composite exhibits properties near to carbon fiber composites, except for a lower elastic modulus. Material mechanical parameters independent of sample size were calculated from flexural tests with various span-to-sample, height ratios. In contrast to composites reinforced with fiber rovings, composites reinforced with fabric fiber were more brittle and less anisotropic, which was reflected in material mechanical parameters.