Fiber-reinforced mineral wool geopolymer composites

• Main Author: Adesanya, E. (Elijah)
• Format: Dissertation
• Language: English
• Published: University of Oulu 2015
• Subjects: Environmental Engineering
• Online Access: http://urn.fi/URN:NBN:fi:oulu-201506271885; http://nbn-resolving.de/urn:nbn:fi:oulu-201506271885

This thesis investigates the utilization of mineral wool (glasswool and rockwool) as precursor with metakaolin in geopolymerization. In 2015, mineral wool waste in Europe is estimated to be 2.4 metric tonnes, and it is currently landfilled. The utilization of this waste in geopolymer composites is one of the motivation towards this study. Indeed, addition of these mineral wools to metakaolin-based geopolymers matrices showed significant improvement in the mechanical properties. The literature section of this thesis describes the previous knowledge on geopolymerization, the materials used in geopolymer and the factors affecting the mechanical strength. In the experimental part, the first goal was to achieve mix composition with highest mechanical strength and also a workable paste of geopolymers. This was done with the following factors held constant: SiO₂/Al₂O₃ = 3.8 and Na₂O/Al₂O₃ = 1, and varying the following: H₂O/Na₂O from 10 to 13, SiO₂/Na₂O from 3.21 to 4.02, mineral wool/metakaolin mass ratio from 0–1, and water/binder (w/b) mass ratio from 0.42 to 0.55. The different mix compositions was calculated at varying substitution (10%, 20%, 30%, 40% and 50%) of metakaolin with mineral wool using both glasswool and rockwool in different matrices to determine the effect of mineral wool substitution on the properties of the geopolymer. Mechanical strength tests were done to determine the effects of mineral wool addition in the geopolymer. Results from the test shows maximum compressive strength of 33 MPa when 20% of the metakaolin was substituted with mineral wool. Further substitution was observed to reduce the mechanical properties of the geopolymer. Also, optimization of glasswool and rockwool in different compositional mixes was done to select a particular mineral wool to be used further in the course of the study. Glasswool precursor with metakaolin showed better compressive strength using the chosen SiO₂/Al₂O₃ and Na₂O/Al₂O₃-ratios, compared to rockwool and was continued as the co-binder with metakaolin during reinforcement with fibres. Additionally, during the investigation the matrices were cured at various temperatures (50, 60, 80 and 100 °C). Results showed best mechanical strength was achieved when the geopolymer matrices were cured at 50 °C. XRD and TGA where used to characterize the behaviour of the raw materials and geopolymer samples and to verify geopolymer formations and its thermal stability respectively. Geopolymers in general during testing experiences brittle failure, this limitation can be corrected using fibre reinforcement. Geopolymer composites with glass, carbon and cotton/polyester fibres were investigated using a simple layering method. Data from these preliminary tests showed that cotton/polyester blend fibre exhibited better ductility and flexural strength than glass and carbon fibre.