Development and Optimisation of Cast Geopolymer Moulds for Blown Glass Manufacturing

This thesis investigates the development of lightweight cast geopolymer moulds for mould-assisted glass blowing. Ten potassium-activated, metakaolin-based formulations were screened using laboratory operations required for casting and evaluated for open porosity, geometric density, flexural strength, compressive strength, and qualitative optical microscopy. Selected materials were then transferred to larger hemispherical sections and assembled into mould couples. Formulations 6 and 10 were retained based on combined processing, physical and mechanical evidence. Their mean open porosities were 12.07 ± 3.13% and 10.25 ± 1.03%, respectively, and their mean flexural strengths were 10.18 ± 0.61 MPa and 9.24 ± 1.07 MPa. Scale-up showed that the laboratory procedure could not be reproduced by simply multiplying the batch size: vessel and blade limitations, agglomeration and high viscosity required adaptation of the mixing operation, and gradual feeding of the solid components provided a workable scale-adapted approach. The manufactured mould couples were evaluated during glass manufacture in Murano, where the cast sections were transported, handled, assembled and used in open and closed configurations in contact with hot glass. The moulds were released from the glass without difficulty, and no immediate material failure was recorded. The factory trial produced good-quality transparent and coloured glass pieces with approximately spherical forms. The results document a casting-based development pathway and demonstrate manufacturing feasibility. Accurate alignment and coupling of the separately cast mould halves remained the principal manufacturing limitation.