Ceramics-Silikáty 67, (2) 227 - 234 (2023)

Two different mix compositions were prepared to compare the effect of waste glass sludge, with and without a crystallising admixture, on the properties of fresh cement paste and hardened cement paste. In Composition 1 cement was replaced by different percentage of waste glass sludge: 0 %, 5%, 10%, 15%, 20%, 25%, and 30%. In Composition 2 the same cement content was used with the addition of the crystallising admixture added at 1 % by weight of the binder. The tests showed that the replacement of 20 % of cement with waste glass sludge improved the properties of hardened cement paste, but the properties of fresh cement paste deteriorated. The results of the tests with composition 2 containing the crystallising admixture showed that the crystallising admixture had a negligible effect on the properties of hardened stone, while the properties of fresh cement paste improved in comparison with the specimens without the crystallising admixture. The overall results showed that 20 % was the optimum amount of cement to be replaced with waste glass sludge and that crystallising admixture could be one of the solutions to improve the workability of the mixtures modified with waste glass sludge.