Evaluation of Reducing NO and SO₂ Concentration in Nano SiO₂-TiO₂ Photocatalytic Concrete Blocks

The use of titanium dioxide in concrete block pavements is a promising approach to reduce air pollution in the roadside. When TiO₂ is used as an additive of cement concrete or mortar, it is not dispersed uniformly due to agglomeration between particles causing the degradation of photocatalytic reaction. To improve the photocatalytic performance of TiO₂, the Nano SiO₂-TiO₂ (NST) has been developed by coating TiO₂ with SiO₂ as a support using the sol-gel method. The environmental performance of concrete blocks incorporating NST as an additive was evaluated using both laboratory and full-scale chamber experiments. It was observed from laboratory environment chamber testing that the NO reduction efficiency of concrete blocks with 4% NST ranged from 16.5 to 59.1%, depending on the UV intensity. Results of the full-scale chamber test on NST concrete blocks indicated that the NO and SO₂ reduction efficiencies were 22.3% and 14.4% at a 564 W/m² of solar radiation, respectively. It was found that the increase in UV intensity and solar radiation had a positive effect on decreasing NO and SO₂ concentration. In the future, the NST will be applied at in-service photocatalytic block pavements to validate the environmental performance in field conditions.