Depollution is the removal of contaminants and impurities from the environment. The newest tool for achieving depollution is a photocatalyst. Photocatalysts accelerate the chemical reaction whereby strong sunlight or ultraviolet light decomposes organic materials in a slow, natural process. When used on or in a concrete structure, photocatalysts decompose organic materials, biological organisms, and airborne pollutants. Dirt, soot, mould, bacteria and chemicals that cause odors are among the many substances that are decomposed by photocatalytic concrete. These compounds break down to have a minimal impact on the environment.
Titanium dioxide (TiO2), a white pigment, is the primary catalytic ingredient, and can be incorporated in the cement manufacturing process. When activated by the energy in light, the white pigment creates a charge that disperses on the surface of the photocatalyst, and reacts with external substances to decompose organic compounds. Photocatalytic concrete has other environmental benefits, such as reflecting much of the sun’s heat and reducing the heat gain associated with dark construction materials. This keeps cities cooler, reduces the need for air-conditioning and reduces smog. Designing projects with photocatalytic precast concrete also helps to promote aesthetic endurance, keeping the structure looking like new for decades.