Highly-efficient green photocatalytic cementitious materials with robust weathering resistance: From laboratory to application

The combined use of nano-TiO₂ with cementitious materials offers an environmentally-friendly way to combat the air pollution problem. However, a trade-off between a high efficiency and a robust weathering resistance has often to be made for most of the attempted nano-TiO₂ incorporation methods. This paper developed a simple and effective “spraying” method to coat nano-TiO₂ particles on the surface of concrete surface layers (CSL). The results showed that the NO_x removal rate of the samples increased with an increase in both the concentrations of nano-TiO₂ solutions and the number of times of the spraying action. And the conditions for preparation of the Spray AB (the CSL were first sprayed with the 30 g L⁻¹ TiO₂-solution 20 times, followed by mechanical compaction, and for another 20 times after the compaction) were found to be optimal in terms of NO_x removal performance and weathering resistance. The Spray AB was superior to the 5% TiO₂-intermixed samples with respect to photocatalytic NO_x removal ability. Compared with TiO₂-dip-coated samples, the Spray AB samples had better and robust weathering resistance. A case study on the factory-fabricated green Eco-blocks (produced by the laboratory-developed spray method and the conventional intermix method) was performed. Examination and comparison on their respective photocatalytic NO_x removal further verified the advantages of the spray method over the intermix method.