Xuejuan Cao

Cooling Principle Analyses and Performance Evaluation of Heat-Reflective Coating for Asphalt Pavement

In the experiment, a self-made heat reflective coating (hereinafter named as HRC) was applied to the surface of asphalt pavement. The coating temperature reduction principle and the mechanism to mitigate the urban heat island effect (UHI) were explored by analyzing the material characteristics and features of atmospheric absorption spectrum. HRC features a good water-proof ability, strong oil resistance, abrasion resistance and ageing resistance. When it was painted on the surface of the dense-graded asphalt concrete, the pavement temperature could be reduced by about 9°C in hot seasons. The comprehensive pavement performance were evaluated through the following test: anti-skid test, accelerated abrasion test, freeze-thaw cycle test, and permeabiltiy test. The results shows the asphalt concrete pavement with adopting HRC has a strong abrasion resistance, a good resistance to temperature fluctation and a great significance to reduce water damage. And it also shows the skid-resistant ceramic granular should be added in the dense-graded asphalt pavement with HRC, which can greatly improve anti-skid capability.

Preparation of La-doped nanometer TiO2 and its application for NO removal on asphalt concrete

La-doped TiO2 nanoparticle was prepared by ultrasonic assisted sol–gel method. Its crystalline phase, surface morphologic structure and optical property were characterised by X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet visible light spectroscope (UV–VIS). The photocatalytic activity of La-TiO2 was evaluated by the degradation of nitric oxide (NO) under visible or ultraviolet irradiation. The results indicate that the photocatalysts exist lattice distortion and grain refinement after the modification, which cause more reactive centres on the surface, lead to the red shift of absorption spectra and the increase of absorption in ultraviolet light region. It concludes that the modified sample with 0.5% dosage of La has the optimal photocatalytic activity. Next, the La-TiO2 nanoparticles were well dispersed in silica sol and then loaded on the surface of asphalt concrete specimens, and the specimen’s degradation performance of NO was tested by using the self-designed photocatalytic performance tester. The results demonstrate that the specimens present considerable photocatalytic activity under different conditions of light sources, and the NO degradation rates diminish gradually with the increase of NO concentration in the mixed gas and the flow velocity. Under ultraviolet light and visible light irradiation, the NO degradation rates are 39.37% and 19.7%, respectively.

Analysis on the cooling effect of a heat-reflective coating for asphalt pavement

A type of self-made heat-reflective coating was applied on the surface of different types of asphalt concrete. The temperature of the asphalt mixture specimens with coatings that have different application rates was measured. By calculating the temperature difference between the specimen with and without the coating, the results show that the cooling value first increases and then becomes flat as the application rate of the coating increases. With the same coating application rate, dense-graded asphalt mixture has the best cooling effect, followed by the stone matrix asphalt (SMA) mixture, and finally, the open-graded friction course (OGFC) asphalt mixture has the lowest cooling effect of the tested specimens. The reason is that the OGFC asphalt mixture has a high per cent of air voids and part of the coating will penetrate into the air voids, so less coating is available to reduce the temperature. The SMA mixture has a higher texture depth than the dense-graded asphalt mixture, which compromises the cooling effect of the coating. The cooling mechanism was analysed through microscopic analysis methods, and the reflective spectrum was measured by ultraviolet–visible–near-infrared spectrometer. Results show that the coating has a high reflectivity due to the addition of fillers, which reduces the heat absorption of pavement. The Infrared spectra of the coating and fillers in the middle infrared region were tested by the Fourier transform infrared spectrometer. It indicates that the fillers have good thermal radiation ability in the atmospheric window. Accordingly, the coating presents a good cooling ability in this region, which can further reduce the temperature of the pavement. Pictures from the scanning electron microscope prove that there are many fillers scattered on the surface of the coating, which can bring about a good cooling effect.

Preparation of fluorinated acrylate coating with high albedo and its cooling effect on asphalt mixture

With regard to the high-temperature diseases of the asphalt pavement, an environment-friendly emulsion with high albedo was considered for reducing the pavement temperature. Firstly, the effect of types and dosage of the fluorine monomer on properties of the emulsion was analysed through using the conventional emulsion polymerisation. Afterwards, by taking the fluorine monomer as the shell and acrylic monomers as the core, the stability and hydrophobicity of the emulsion with different core–shell ratios were studied with the seed emulsion polymerisation method employed. Based on the results derived from adding different types and dosage, TiO2 to the core–shell emulsion, it can be easily found that a better cooling effect can be obtained with the optimum amount being 10% when the particle size of TiO2 concentrates on 200–1000 nm. Finally, the reflectance spectrum of the coating and the cooling values of the asphalt specimen with the coating were tested, respectively. The results show that the albedo of the coating reaches 78.64% and the specimen temperature can be reduced by 13°C when the normal asphalt mixture approaches 60°C.

Indoor and Outdoor Aging Behaviors of a Heat-Reflective Coating for Pavement in the Chongqing Area

AbstractThe indoor and outdoor aging behaviors of a heat-reflective coating were studied regarding the problems derived from aging and reduced cooling effects. A one-year natural exposure test of the coating on a roof and on concrete samples was conducted, and a 28-day xenon lamp aging test on concrete and cylindrical samples was carried out. Surface appearance, infrared spectrum, cooling value, and reflectivity changes in different aging periods were analyzed. The results show that the amount of solar radiation is a key factor in aging. Aging can cause a gradual increase in carbonyl content and thus lead to a decrease in resin light transmittance, given that the carbonyl group absorbs visible light and infrared rays easily. This results in a reduction in reflectivity and cooling value. Reflectivity and cooling value show a linear relationship in the indoor and outdoor aging process. With respect to reflectivity and cooling value, solar radiation has a downward quadratic parabolic tendency whereas xenon l...