Geompolymers and their engineering applications have attracted significant attention of the scientific community. This is due to properties such as good thermal stability and high resistance to aggressive environments. Most studies on this subject are based on traditional precursor materials such as calcined kaolinite clay (metakaolinite) and fly ash. The iron content is significant, reaching around 10% in metakaolinite, for instance. The role of iron in geopolymers still lacks systematic investigation. This can be attributed to the limitations presenting nuclear magnetic resonance (NMR) spectroscopy, which is a widely used technique to study geopolymers structure. Ferromagnetic elements such as iron, which is often present in some precursors, affect the magnetic response of the material, compromising the proper analysis of its structure by NMR results. Iron content in some industrial residues may be several times higher as it is often found in metakaolinite. This work presents x-ray diffraction, infrared and Mössbauer spectroscopy studies on the distribution of iron species in iron oxide/hydroxide-rich precursor, which was used to synthesized geopolymers.

The use of geopolymers as matrix in composites with syntactical fibers have been studied and proposed in the literature. Nonetheless, for the best know of the authors, there are no researches about the use of geopolymers as matrix in composites with natural fibers. The use of natural fibers is increasing in the automotive industries. One of the problems to expand the use of natural fibers in composite materials is the low fire resistance of the classical type of polymers. In this sense, geopolymeric matrices open up horizons for this type of application. This paper studies composites with geopolymeric matrices reinforced with two types of natural fibers: sisal (Agave Sisalana) and pineapple leaf fiber (PALF-Ananas Comosus). The mechanical properties of these new composites are investigated by mechanical tests. The results confirm the increasing in the mechanical performance whenever the fibers are under traction stress.