Effect of Borosilicate Glass Wastes and Synthetic Silica on Cement Products Properties

This paper presents the findings of research study on the effect of borosilicate glass wastes on properties of cement paste and mortar. The borosilicate glass contains three times less alkali than soda-lime glass and about 12 % of boron oxide, so pozzolanic activity of borosilicate glass is three times higher compared to soda-lime glass. In order to increase the pozzolanic activity of glass precipitated synthetic silica was used. Mathematical models were used in order to test the effect of synthetic silica on pozzolanic activity of borosilicate glass. Test results indicate that replacement of 1 % of borosilicate glass by synthetic silica increased the pozzolanic activity up to 9.4 mg CaO/g of additive. By adding 5 % of borosilicate glass instead of cement, the standard compressive strength is reduced by about 20 %. However, complex additive of borosilicate glass (2–5 %) and synthetic silica (0.5 %) increased initial compressive strength of cement mortars to 10 %.