Post-functionalized roofing granules and process for preparing same

A plurality of functionalized roofing granules, wherein each granule of the plurality of functionalized roofing granules comprising:

• a base roofing granule;
• a first coating layer disposed over the base roofing granule, the first coating layer including at least one coloring material disposed in a binder based on an alkali metal silicate;
• a second coating layer disposed over the first coating layer, the second coating layer being a sodium ion barrier layer formed from silica glass or crystalline silicaceous material;
• a transparent or translucent outer coating layer disposed over the second coating layer, the outer coating layer including photocatalytic anatase titanium dioxide having an average particle size less than 0.2 microns disposed in a binder based on colloidal silica or an organic polymer, the outer coating layer not including a binder based on an alkali metal silicate, an alkaline earth metal silicate, or a metal phosphate.