In this study, a mineral matrix based on hydrous sodium metasilicate (NSH5)-activated slag cement (AASC) was found to be suitable for solidification of sodium nitrate solutions with concentrations of up to 700 g/l and nitrate ion-exchange resins with volume of up to 35%. XRD, TG/DSC, FTIR, and SEM/EDS analyses were used to study the wasteforms. Increasing the nitrate solution concentration decreased the rates of hydration and structure formation process of the system GGBFS-NSH9-NaNO3 solution, the amount of the Ca-, Si-, Al-, and Mg-containing reaction products, and slightly decreased the compressive strength of the wasteforms.