Chemical durability of glass with compositions of mineral fibres

Abstract

The objective was the study of the relation between the composition and chemical durability of glass with the composition of man-made mineral fibres. The other purpose was to compare the corrosion rate of chip glass with results previously obtained from fibre compositions. Finally, the effect of CO2 , phosphate, binder, and buffer solution at pH 5 were also studied. In the theoretical part, Gibbs free energies of dissolution were computed using multicomponent norm calculation. In the experimental part, experiments were performed with four types of glasses, i.e; borosilicate glass, E glass, slag, and basalt, both with original MgO/CaO ratio and MgO free, exposed to a simulated extracellular lung fluid (Gamble's solution), at 37C, and with a sample surface area to solution volume ratio of 0.1cm-1 : the CO2 partial pressure and pH were varied. The same durability sequence was found as previously determined in flow experiments with fibres of very similar composition. All glasses were slightly more stable in CO2 (5%) saturated Gamble's solution that in N2 saturated one. At pH 5, the basic basalt and slag glasses assumed very high corrosion rates, whereas the borosilicate fibre JM became very durable. The latter finding is explained by the depletion of alkali and boron converting the depletion into a high silica alumina glass. Some evidence is presented that the MgO content of a glass causes an inhibited corrosion in the presence of a binder.