关键词: 道路工程, 混凝土, 表面构造, 灰度值, 图像法, 光照强度, 露骨率

Abstract: In order to provide more convenient and accurate measurements of characteristics of concrete surface structure, based on the data of Shantou-Zhanjiang expressway in Guangdong province, rapid sampling by means of digital image processing technology and analysis and calculation in late stage was realized. And the influences of illumination, shooting angle and distance, image processing calculation rule and the cleanliness of concrete surface on the measurement results were also studied. The results show that filtering and denoising should be carried out before the surface structure characteristics of the concretes initial image are identified. When shooting angle is frontal, shooting distance has little effect on the gray value. With the increase of illumination，the gray value increases first and then decreases. Debris on the surface of concrete will be reflected on the image, thus interfering with the judgement of the characteristics of concrete surface structure. Therefore, the appropriate illumination should be selected through experiments, and maintain stability throughout the process. At the same time, the surface of the measured concrete should be kept clean.

Key words: highway engineering, concrete, surface structure, gray value, image method, illumination, exposed aggregate ratio