Thermal, optical and mechanical properties of new glass compositions containing fly ash

The investigation of new compositions is crucial for the expansion of possible applications of glass, from the typical applications for building engineering, in the form of cast blocks or float glass, to more advanced technologies, such as 3D-printed glass or glass-to-metal connections. Since high melting temperatures and brittleness are two important drawbacks of glass, this work aims to improve both properties. Characterisation techniques, such as thermal analysis, nano-indentation, and UV/VIS spectroscopy, are used to evaluate the properties of the samples. The modification of the properties is achieved via changes in the composition of the glass, using compounds such as phosphorus pentoxide, aluminium oxide and boron oxide. Then, the choice of different glass formers and modifiers contributes to the development of compositions with lower melting and glass transition temperatures. The reduction of the melting temperature allows a saving of energy during the manufacturing. The structures of the glasses differ from the standard soda–lime–silica and borosilicate glasses, leading to a different mechanical behaviour. Furthermore, these new compositions incorporate up to 35% of fly ash in their formulas. The valorisation of these by-products reduces costs and gas emission.