The influence of the type and grain size of glass waste on the physical and mechanical properties of cement mortars

Due to the problem of dwindling natural resources and increasing waste volumes, the use of various waste materials as a substitute in cement-based products is gaining particular importance. This study compared the effect of two types of waste glass – transparent and blue – in two fractions (<0.063 mm and 2 mm - 0.063 mm), used as a partial sand substitute, on the physical and mechanical properties of cement mortars. Thirteen sample series were prepared, including a control sample (CS) and samples with glass added at 10 %, 20 %, and 30 % by weight of cement as a substitute for aggregate (standard sand). The tests were conducted in accordance with applicable PN-EN standards, assessing workability (flow table method), flexural and compressive strength after 7 and 28 days, water absorption, and frost resistance. The study showed that glass additives reduced the workability of mortars, particularly in the case of fine fractions, although some of the mixtures improved mechanical properties. After 28 days, the highest compressive strength was achieved for mortars with 10 % - 20 % blue glass (over 62 MPa), exceeding the reference sample. Flexural strength was also highest for samples with 10 % blue glass (<0.063 mm). The results suggest that appropriately selected glass type and amount can positively influence the performance of cement mortars, supporting the concept of sustainable construction.