‘Glass based stoneware’ as a promising route for the recycling of waste glasses

Soda–lime–silica scrap or waste glasses are almost widely accepted sintering additives for the manufacturing of traditional ceramics. Although interesting, this solution does not fully exploit the potentialities of glasses compared to feldspar fluxes. In fact, glasses exhibit the softening and consequently the ability of viscous flow sintering, at much lower temperatures than those required for feldspar melting, and this could be very useful to develop ‘environmentally friendly’ ceramics, i.e. made with a reduced consumption of energy and natural raw materials. In the present study, a high glass recycle approach is reported, which replaces the feldspar flux, in the formulation of porcelain stoneware, with finely powdered soda–lime glass or glasses from dismantled cathode ray tubes (CRTs). This allowed the manufacturing of ceramics at 880–920 and 750–775°C, respectively. The final products were optimised by the addition of calcium hydroxide for soda–lime glass and Al₂O₃ platelets for CRT glasses, in order to promote the partial devitrification of the glass or control the fracture propagation. Owing to their overall mechanical properties (bending strength exceeding 70 MPa, hardness exceeding 6 GPa, fracture toughness exceeding 1⋅1 MPa m^0⋅5), the new products could find applications in the construction industry.