Synthesis, microhardness, fracture toughness and microstructural features of chitosan containing alkali activated geopolymers.

In this work, geopolymer matrix samples containing different amounts of chitosan, specifically 1, 3, 5 and 10 wt%, were produced to study the effect of a ductile phase within a much more brittle one. The reference geopolymer was produced mixing a commercial metakaolin with sodium silicate solution and sodium hydroxide solution. Geopolymeric slurries were caste into mold and hardened by a thermal treatment at 70 °C and then at ambient temperature for 28 days. Hardened materials, containing different amount of chitosan, were examined by mean of X-ray diffraction, Fourier Transform Infrared Radiation, Scanning Electron Microscope investigation. Microhardness and fracture toughness were measured to study the effects on the samples chemistry and microstructure caused by the introduction of chitosan into the geopolymer. It has been observed that the addition of chitosan lowers materials porosity and microhardness, but slightly improves their fracture toughness. [ABSTRACT FROM AUTHOR]