| Geopolymer is one of a new class of inorganic polymeric materials, and geopolymers made from alkali-activated metakaolin have found applications in many fields. However, the mechanisms of geopolymerisation are still not fully understood. Attempting to develop low cost geopolymer products for infrastructure application, fly ash, one of major industry wastes, is found to be a good candidate for replacing metakaolin partly or even completely. For fly ash based inorganic polymeric (FABIP) materials, it has been demonstrated that additional Al-source materials are necessary to achieve good mechanical properties. However, their role and effects are yet to be quantified. In this dissertation research, sol-gel chemistry of aluminosilicates is proposed, and found to be an effective approach to understand the mechanisms of geopolymerisation. Such model can explain why Al-source materials, such as metakaolin, are required for promoting geopolymerisation for FABIP, with investigating both the chemical and the mineralogical compositions of fly ash and the requirements of geopolymerisation. Further, an extensive mix composition study is undertaken to validate the proposed model. The effects of major mix constituents are thoroughly evaluated based on the physical and mechanical properties of the various fresh mixes and hardened samples. In addition, two series of experiments are designed to evaluate the durability performance of FABIP mortar: one for chemical resistance and the other for freezing-thawing resistance. The test results are evaluated and compared with those of Portland cement mortars. Finally, the potential application of FABIP materials is investigated based on their market needs and advantages over Portland cement. The production cost of FABIP is analyzed with comparison to Portland cement. It is observed that more and more applications will be found for FABIP materials with acceptance by industries and new legislation regarding environment protection and global sustainability. |
