Preparation Technique and Properties of Nano-TiO2 Photocatalytic Coatings for Asphalt Pavement

Abstract

According to the characteristics of asphalt pavement, a kind of nano-TiO2 photocatalytic coating was prepared by using the emulsified asphalt as the carrier. All of its properties met the technical requirements. An exhaust gas degradation test device and its test steps were developed. The evaluation indexes, cumulative degradation rate, and degradation efficiency, were put forward. From the two aspects of the nano-TiO2 content in photocatalytic coatings and the spraying amount of photocatalytic coatings in the surface of slabs (300 mm × 300 mm), the exhaust gas degradation effects, the performances of skid resistance, and the water permeability of asphalt mixture were analyzed. The test results showed that the cumulative degradation rate of exhaust gas was better when nano-TiO2 content was increased in the range of 0–8% and the spraying amount was changed in the range of 0–333.3 g/m2. In practical engineering applications, the anti-skid performance of asphalt pavement can be satisfied when the spraying amount of photocatalytic coating was limited to under 550 g/m2. The spraying amount of nano-TiO2 photocatalytic coating had little effect on the water permeability of the asphalt mixture. Therefore, 8% nano-TiO2 content in the coating and a 400 g/m2 spraying amount were finally recommended based on the photocatalytic properties, as well as for economic reasons.

Smart, Photocatalytic and Self-Cleaning Asphalt Mixtures: A Literature Review

“…In order to obtain photocatalytic asphalt mixtures, it is possible to highlight four main techniques that can be utilized to apply the semiconductor materials in the asphalt mixtures: (i) spraying coating [6,9,39,45,67,70,72], (ii) volume incorporation [6,67,72,76], (iii) bitumen modification [70], and (iv) spreading [67,72,77,78]. Bitumen modification is developed before the manufacture of the asphalt mixture.…”

“…Wang et al [78] concluded that the friction and texture depth of the asphalt mixtures decreased when the spreading TiO 2 coverage rate (by emulsion spreading) is increased. Considering the local technical requirements, 550 g/m 2 is the maximum coverage rate that respects these parameters.…”

NOx-Reduction Performance Test for TiO2 Paint

“…From 2000 to 2010, only two studies were conducted in which TiO 2 photocatalysts were mixed with concrete and cement [ 31 , 32 ]. However, seven studies were conducted from 2010 to 2020 [ 29 , 33 , 34 , 35 , 36 , 37 , 38 ]. These studies mainly focused on road pavement materials, exterior materials, and roof finishing materials.…”

“…A review of previous studies on the application of TiO 2 is presented below. The most representative applications are cement road materials, which include pavement blocks [ 29 ], asphalt pavement [ 33 , 36 , 37 ], and mortar [ 34 , 35 ]. The reduction in NO x concentration was examined by adding TiO 2 photocatalysts to these cement road materials, and it was observed that the NO x concentration can be reduced by up to 60–80% [ 31 ].…”

“…Yu et al investigated NOx concentration reduction performance based on automobile exhaust gas concentration through field measurement and verified the optimal mass ratio [ 36 ]. Wang et al investigated the effect of exhaust gas decomposition by setting the UV irradiance as 26.7 W/m 2 , which is the average outdoor illumination, and it was confirmed that exhaust gas decomposition can be achieved when the nano-TiO 2 content is 8% [ 37 ]. Witkowski et al conducted NO removal experiment using a photocatalytic pavement block used for 7 years on a silver bicycle road, and the NO gas reduction performance was investigated by applying 300 W of light; scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) mapping analyses were performed to confirm TiO 2 mixing in the pavement block [ 38 ].…”