Preparation of Visible Light Photocatalytic Asphalt Pavement using Fe Doped g-C3N4 for Removal of Vehicular NO: Feasibility Study

Photocatalytic pavement based on traditional photocatalyst has been proposed to cure the air pollution caused by automobile exhaust. However, the low degradation efficiency under visible light limits the application of photocatalytic pavement in practice. A visible light photocatalytic asphalt pavement with higher degradation efficiency was developed in this study using Fe doped g-C3N4 (Fe-C3N4) as photocatalyst. The photocatalyst was added to slurry seal with the aim of improving wear resistance of the photocatalytic coating. The modification mechanism of Fe-C3N4 was analyzed by combining the microscopic characterization and NO removal efficiency of photocatalyst. The photocatalytic performance, skid resistance, and wear resistance of asphalt pavement were studied under visible light. The results indicated that Fe element could be used as an effective electron receptor to capture electrons in the conduction band of g-C3N4, which lead to a lower recombination rate of photoinduced electron-hole pairs, and could enhance the absorption intensity and broaden the response of g-C3N4 to visible light. In addition, the slurry seal specimen using epoxy resin instead of emulsified bitumen as binder had better photocatalytic performance. The NO removal efficiency of the epoxy resin slurry seal specimen reached the highest level when the Fe-C3N4 content was up to 50% of the quality of mineral powder. Both skid resistance and wear resistance of the specimen met the standard requirements of pavement. The specimen still retained an effective photocatalytic ability after the abrasion test.

Performance Evaluation of Slurry Seals Containing Reclaimed Asphalt Pavement

Preventive pavement maintenance methods such as slurry seals are cost-effective treatments that increase the longevity of pavements. The incorporation of recycled materials such as reclaimed asphalt pavement (RAP) into asphalt pavement helps to further reduce costs and energy consumption. The present research studied the feasibility of incorporating RAP into slurry seal mixtures or RAP slurry seals. Two slurry seal mixtures containing cement and hydrated lime as fillers were tested. The first mixture comprised slurry seal made with virgin aggregate and the second used RAP as the aggregate. The wet track abrasion test (WTAT) and loaded wheel test (LWT) were conducted to evaluate the performance of the mixtures. Wet cohesion and friction tests (sand patch and British pendulum) were performed on the selected slurry seal mixtures with the best performance under WTAT and LWT. The results show that it is possible to prepare slurry seal containing RAP. Although the curing time relative to the virgin aggregates increased by 1 h for RAP aggregate, the wear value in the WTAT decreased by half. Lateral displacement and the British pendulum test results improved considerably for slurry seals made with RAP aggregates. The results of the sand patch test on WTAT samples showed that slurry seals made with RAP should be lightly rolled after lay-down to improve their friction life. Cost analysis indicates that the use of RAP as an aggregate in slurry seal decreased costs by up to 14%. RAP slurry seal showed better overall performance with lower cost than the virgin slurry seal.