Synthesis and characterization of hemp and flax fiber reinforced geopolymer composites

Reinforced Ordinary Portland Cement (OPC) has for a long time been a viable binder until the realization of its huge contribution to the excess carbon dioxide emitted in the atmosphere during its fabrication. The aim of this research work is to synthesize and characterize Collie fly ash based geopolymer composites reinforced with flax and hemp fibers. It was shown in this work that fiber reinforced geopolymer composites are possible supplements or substitutes to OPC because of the composites’ high flexural strength, low emissions of carbon dioxide during synthesis and low cost of fabrication. Energy Dispersive Spectroscopy (EDS) was used to determine the elemental composition. Samples were analyzed for fractural strength in vertical and horizontal orientations of the fabrics, with respect to an applied test load. Scanning Electron Microscopy (SEM) was used to study the microstructure. The highest flexural strength achieved in this study was 7.9 ± 0.2 MPa, which was for hemp reinforcement in an orientation where the load was perpendicular to the plain of the reinforcement fabrics (horizontal orientation). This flexural strength is higher than the value of  6.4 MPa reported for OPC by Li et al.  Key words: Geopolymer composites, cementitious material, flexural strength.