| Abstract [eng] |
The silicate-based binder industry is one of the most carbon-intensive industries. This is due to the use of carbonate raw materials and high production temperatures. To reduce emissions, the search is on for a substitute for traditional binders is ongoing. A group of materials that is attracting a lot of attention is low-base calcium silicates, such as wollastonite, which hardens in a carbon dioxide environment. This mineral requires three times less calcium carbonate and a lower temperature of around 400 °C to produce. If the production of wollastonite is carried out in two stages, hydrothermal synthesis and calcination, a waste product from alumina production, silica-gel, which contains both aluminium and fluoride ions, can be used. These impurities are bound into stable compounds during the synthesis process, making this production more environmentally friendly in three aspects: 1) lower carbon dioxide emissions, 2) lower energy consumption, and 3) the use of industrial waste. This thesis investigates the synthesis of wollastonite and the influence of starting materials on the structure and composition. The obtained synthetic materials were investigated for their application as binders or fillers in polymer composites. The application of silica-gel waste as a source of silica results in the formation of a calcium fluorosilicate, cuspidine. The formation of this mineral from various starting materials, its structure and binding properties in both water and carbon dioxide environments were also investigated in this thesis. |
