PURPOSES : The objective of this study is to quantitatively evaluate the visibility of a mixed-color asphalt pavement. METHODS : The visibility was compared and evaluated using a color pavement specimen, i.e., a pigment was added to the asphalt binder, which was used to fabricate a color pavement specimen, with red aggregate as the coarse aggregate, and the resultant difference in visibility was quantitively evaluated. The color asphalt mixture to which the pigment was added was prepared by varying the amount of pigment added — i.e., 3 %, 5 %, and 7 % of the total weight of the mixture — to confirm the change in visibility according to the amount of pigment added. For the color asphalt mixture with color aggregates, red-colored mudstone coarse aggregates(13mm and 10mm) were used. It is assumed that the surface of the produced specimen simulates the initial performance periods and the cut section of the specimen simulates the state of completion of the performance periods. RESULTS : The initial ΔE for the colored pavement exhibited the best visibility of WC-2-R. However, when considering the value of a in the red color pavement, the visibility of SMA13-R and WC-2-R was assessed as best; this is because SMA13-R exhibits a lower color difference than WC-2-R at the beginning of the performance periods but the red color is better. Upon completion of the colored pavement performance periods, the ΔE of each specimen using the SMA13-0C specimen as the reference specimen was high in SMA13-RC and ΔE using the WC-2-0C specimen as the reference specimen was also high in SMA13-RC. In addition, the a value is also higher than that of other mixtures so it is judged that the visibility of SMA13-RC is best when the performance periods are completed. CONCLUSIONS : The a value tended to increase with the increasing amount of pigment added at the beginning of the performance; however, it was found to decrease rapidly as the performance was completed. However, in the case of using SMA13-RC as the colored aggregate, since the color of the aggregate itself is red, it exhibits a constant value of 5.67 from the performance start to completion. Therefore, it is judged that a constant red color can be expressed during the performance period when the colored pavement using red colored aggregate is applied to the exclusive bus lane.

Red mud is a waste generated by the aluminium industry, and its disposal is a major problem for this industry. Red mud has a reddish-brown color and superfine particle characteristics. So, it can be a promising pigment admixture for concrete industry. An experimental study was conducted to investigate the potential use of red mud in color concrete. The micro structures of red mud and iron oxide pigment such as porosity, pore size distribution, diameter of particle were analyzed with the aid of SEM, X-ray diffraction(XRD), and the infrared absorbance. Tests on physical properties of color concrete, such as strength, slump, early shrinkage crack patterns, and color characteristics were carried out and the results were reported in this paper.