Performance of photo-catalytic paving blocks made from waste

Preliminary studies at The Hong Kong Polytechnic University showed that concrete paving blocks made from local waste materials (including construction/demolition waste and waste glass cullet) can be used to remove nitrous oxide (NO) when titanium dioxide (TiO2) was incorporated in the mix design. To determine the effectiveness of the photo-catalytic paving block when used in field conditions, a batch of factory-produced photocatalytic paving blocks was produced and used in an actual site trial. The air quality of the field testing site was continuously monitored to analyse the effect of the blocks towards the surrounding air quality. The observations showed that nitrogen oxide (NOx) concentrations were reduced by 13% at ground level and by 10% at the breathing zone. After a period of four months the blocks were removed from test site and taken back to the laboratory to analyse whether their ability to remove NO had been degraded. The results showed a decrease in performance of 23%, which is low compared with tests on similar products.