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Abstract
Incorporation of TiO2 into cementitious materials is an important technology in the field of photocatalytic pollution mitigation; however, the photocatalytic activity of TiO2 is limited by specific surface area, poor gas diffusion and light transmission performance of cementitious materials. In this study, a novel photocatalytic lightweight aggregate—photocatalytic ceramsite sand (PCS) was synthesized by loading TiO2 on activated porous ceramsite sand (CS) with negative pressure method to solve problems in application of photocatalysts in cementitious materials. Photocatalytic cement material (PCM) was prepared by loading PCS on the surface of cementitious materials, which improved the photocatalytic activity and efficiency of TiO2 in cementitious materials. It was found that the pore structure (pore volume, size distribution and interconnectivity) of ceramsite sand (CS) varies with particle size. The photocatalytic removal rate of benzene on PCS increased significantly through adjusting ceramsite sands in appropriate pore structure and TiO2 at best coating ratio. The photocatalytic activity of PCS slightly decreased but still remained active after incorporated into concrete. 2 μL benzene was degraded completely in 200 min by 5 g 4PCS-1.25~2.35 and 300 min by PCM-5, and was still degraded over 80% in 400 min by PCM-5 after exposure to natural environment for 6 months. The results suggested that the photocatalytic activity of TiO2 in cementitious materials was enhanced by the preparation of PCS and PCM, which could provide more gas diffusion, higher specific surface area, more TiO2 active sites, and prevent TiO2 particles from being influenced by the envelope of cement hydration products and the carbonation of cement.
Highlights
In recent years, there is an increasing interest in applying photocatalysts in cementitious materials to eliminate urban air pollutants [1,2,3,4,5]
Previous studies [6,7,8] showed that the photocatalytic activity of photocatalysts, especially the long-term photocatalytic performance, decreased obviously after being applied in cementitious materials, whether TiO2 was coated on the surface or mixed with the substrates
Vaish et al [11] presented visible light active photocatalytic filler based on BaTiO3 and reduced graphene oxide immobilized in Portland cement could be readily reinforced the photocatalytic performance for xanthene dye degradation
Summary
There is an increasing interest in applying photocatalysts in cementitious materials to eliminate urban air pollutants [1,2,3,4,5]. There are two ways to improve the photocatalytic activity of photocatalytic cementitious materials effectively: increasing the absorption of air pollutant and reducing the coverage of photocatalysts by cementitious materials or hydration products [16]. Some methods such as introducing the high porosity expanded shale into concrete [17], controlling the pore structure of cement pastes [18] and regulating the microstructure of mortar cement [19] have been developed to enhance the photocatalytic activity of photocatalytic cementitious materials
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