PURPOSES : Graphene nanoplates, which have recently been in the spotlight in various fields, are a layer of graphite used in pencil leads, with carbon arranged in hexagonal honeycomb shapes. The graphene is 0.2 nanometers thick, and it possesses high physical and chemical stability, high strength, and conductivity. These graphene nanoplates have been studied for application in various devices such as semiconductors and batteries, and in the construction sector, where they are used as additives to improve the durability of cement concrete. The purpose of this study was to investigate the physical, and functional properties of graphene-modified asphalt mixtures. METHODS : In this study, the graphene input content of asphalt mixture samples was determined using an asphalt performance grade (PG) test. Based on the results of the test, their strength, stiffness, thermal properties, and electrical conductivity were evaluated. Indirect tensile strength test and dynamic modulus (DM) test were conducted to evaluate the strength and stiffness, and thermal conductivity tests and electrical conductivity evaluations were conducted for determining the functionality of the graphene-modified asphalt mixtures. The thermal conduction test was used to measure the external temperature change over time by placing a general heated asphalt mixture and graphene-modified asphalt with the same raw material-specific mixing ratio inside the temperature chamber in order to measure the heat conductivity. The electrical conductivity was evaluated using a digital multimeter to measure the resistance of DC voltage and DC current via a 4-probe method. RESULTS : The performance grade (PG) test results showed that, for a dynamic shear rheometer (DSR), both tests met the baseline and that physical changes in the binder did not appear evident with graphene addition. Furthermore, each content met the baseline for the bending beam rheometer (BBR). The increasing ratio of flexural creep stiffness approached the maximum when 7.5% graphene was used. In indirect tensile strength test, an average of thrice the indirect tensile strength for graphene-modified asphalt was 0.92 N/mm2, which was approximately 0.04 N/mm2 higher than the average measured three times that of hot mix asphalt mixture, with the same raw material mixing ratio. In the thermal conduction tests, the temperature and the rate of change of temperature of the graphene-modified asphalt mixture were higher than those of the hot-mix asphalt mixture. Lastly, the results of the electric conductivity test using the 4-probe method showed that the electrical conductivity increased slightly as the graphene content increased, but overall, it showed very low electrical conductivity. CONCLUSIONS : In this study, the potential for enhancing the physical and functional performance of graphene nanoplates applied to asphalt mixtures was demonstrated. However, it is practically difficult to arrange graphene particles continuously within an asphalt mixture, which is believed to have very low electrical conductivity.

PURPOSES : Over the years, the concentration of fine dust is gradually increasing, thereby aggravating the seriousness of the situation. Accordingly, this study intends to install a clean road system using low impact development (LID) techniques on the roadside in order to reduce the scattering of dust on roads effectively. This system stores rainwater collected through gutters in rainy weather and sprays water onto the pavement surface to reduce the scattering of road dust. METHODS : The developed clean road system consists of a water tank, controller, rain detection sensor, and solar cell. Based on this, a test-bed construction was used to evaluate its applicability. By applying the developed system, actual applicability was evaluated through total suspended solid (TSS) test and fine dust measurement. TSS test was conducted to measure the reduction rate of scattering dust on the road owing to the water injected by the clean road system. A spray nozzle was used for the TSS test, and a nebulization nozzle was used for the measurement of fine dust. In order to increase the reliability of the test, three measurements were taken each, for normal road as well as unfavorable conditions road that reproduced the construction site. RESULTS : In this study, fine dust concentration measurement and TSS test were conducted to evaluate the practical applicability of the developed clean road system. From the TSS test, it was found that for both general roads and roads depicting bad conditions, the TSS value after the first spray was the highest, and the value after the second spray was sharply reduced, such that most of the re-dispersed dust was washed out after the first spray, and similar TSS value results were obtained after the third spray. Based on this result, the result of fine dust measurement showed similar fine dust reduction effect of 9%-15.9% regardless of the concentration of fine dust in the atmosphere. These results indicate that the concentration of fine dust in the atmosphere does not significantly affect of the degree of reduction in fine dust. CONCLUSIONS : In this study, a clean road system for reducing fine dust on the road was developed and its applicability was evaluated. In a future study, we intend to check the performance of the drainage pavement through performance evaluation of water permeability coefficient test and performance test in the form of drainage pavement. Through this, we intend to evaluate the applicability of the clean road system to which drainage pavement is applied. Moreover, we will develop a clean road system that applies drainage packaging, and analyzes the degree of fine dust reduction according to the spray angle, spray amount, and spray time of the clean road system in order to study the spray system with the optimum amount of fine dust reduction. In addition, in order to reduce fine dust in the winter, when fine dust is mainly generated, it is planned to install heating wires in spray pipes where freezing is expected. Lastly, the black ice prevention effect will be analyzed by mixing a certain amount of sodium chloride when spraying water.