The effect of basalt chopped fiber reinforcement on the mechanical properties of potassium based geopolymer

The processing and mechanical properties of potassium-based geopolymer (K₂O·Al₂O₃·4SiO ₂11H₂O) composites containing 1/2 inch long basalt chopped fiber reinforcement have been evaluated and compared to previous data for 1/4 inch long basalt fiber reinforcement. Geopolymer composite test samples were hand fabricated at ambient temperature and cured in a constant humidity, 50°C temperature/humidity chamber. The effects of varying weight percent of fiber reinforcement and heat treatment temperature for fixed fiber content were examined in this study. Reinforcement by ten weight percent basalt chopped fibers significantly improved the room temperature average bend strength over that of pure geopolymer from roughly 2 MPa to 27 MPa. The composite was able to preserve 75% bend strength after heat treatment to 200°C and 12% strength after heat treatment to 600°C, with only five weight percent of fiber reinforcement. Addition of 1/2 inch long fibers showed 20-50% strength increases over the use of 1/4 inch fibers. A Weibull statistical analysis was performed showing a significant increase in reliability with increasing amounts of chopped basalt fiber reinforcement.