Advancing self-cleaning performance in metakaolin-based geopolymers through in-situ zeolite formation and TiO2 integration

The deterioration of self-cleaning properties of cementitious materials upon hydration was addressed by in-situ zeolite formation within metakaolin-based geopolymers. Pastes with varied in-situ zeolite content were formulated by adjusting the Si/Al ratio of initial raw materials and curing temperatures. The impact of in-situ zeolite formation on self-cleaning performance was systematically investigated through phase composition, optical property and microstructure analyses. Zeolite A formation notably enhances self-cleaning performance, despite contributing to higher band energy and lower Urbach energy. The increases in crystalline zeolite amount and matrix porosity enhances mass transfer capacity. The open pore structure of zeolite facilitates the formation of connective channels during particle growth, mitigating the “sheltering” effect of the surrounding media for photocatalysts and ensuring improved self-cleaning performance upon hydration. This study summarizes the synthesis conditions for zeolite A, providing mechanistic insights into in-situ zeolite formation in metakaolin- based geopolymers and emphasizes its promising potential for optimizing self-cleaning properties in cementitious materials.