The effect of glass composition on the reactivity of synthetic glasses

The reactivity of synthetic glasses depends on their chemical compositions. In far from equilibrium dissolution experiments, the reactivity of Ca‐rich glasses with compositions similar to blast‐furnace slag is found to be much higher (up to ~60 wt.% after 7 days) compared to Si‐rich glasses with compositions similar to type F fly ash (up to ~20 wt.% after 7 days). Isothermal calorimetry and TGA experiments conducted on model systems containing portlandite and calcite and on glass‐blended Portland cement confirmed the higher reactivity of the Ca‐rich glasses. The degree of glass reaction after 91 days ranged from 7 to 20 wt.%. The results showed also a higher reactivity of the glasses containing more aluminum (both for Ca‐rich and Si‐rich glasses) indicating that not only calcium but also aluminum acted rather as network modifier than as network former. The results confirm a strong dependence of the glass reactivity on the degree of polymerization of the glass network.