Sustainable Lime-Silica Materials Based on Waste Packaging Glass

The use of waste packaging glass as a substitute for quartz sand may reduce the consumption of natural raw materials and provide an additional route for glass-waste valorization. However, the combined effects of glass color and replacement level on the relationships among the physical and mechanical properties of autoclaved lime-silica products remain insufficiently understood. This study therefore evaluated products in which 33%, 66%, and 100% of the quartz sand by mass was replaced with colorless, green, or brown waste packaging glass. Cylindrical specimens were autoclaved at 180 °C and a saturated steam pressure of 1.002 MPa for 8 h. Compressive strength, volumetric density, water absorption, and open porosity were determined, and their relationships were evaluated using Spearman's rank correlation analysis and linear regression. Both glass color and replacement level affected the investigated properties, while complete replacement of quartz sand produced the most pronounced changes. The series containing 100% colorless waste glass exhibited the highest compressive strength, water absorption, and open porosity, together with the lowest volumetric density. The colorless glass series also produced the strongest linear fits, with R² values of 0.9703 for compressive strength and volumetric density, 0.9892 for compressive strength and open porosity, 0.975 for water absorption and volumetric density, and 0.9473 for open porosity and volumetric density. The corresponding relationships for brown and green glass were generally weaker, with R² values ranging from 0.6615 to 0.9131. These results indicate that glass color and replacement level can be treated as material design variables and that the identified relationships may support preliminary mixture screening within the investigated compositional range. Following independent validation, these relationships could also support the preliminary assessment of other soda-lime-silica glasses, such as flat glass, tempered automotive glass, or photovoltaic panel glass, while accounting for differences in particle-size distribution, material purity, and the presence of coatings. Waste packaging glass can therefore be considered as a partial or complete substitute for quartz sand, particularly in lightweight, strength-oriented products intended for dry or protected environments. However, the increased water absorption of the colorless glass series and the limited scope of the laboratory tests require further validation before structural applications or applications involving moisture exposure can be recommended.