Relation Degree Analysis of Controllable Factors in the Bitumen Foaming Process

Abstract

PREFACEMost highways built early in China are approaching the period of repair or replacement. Road maintenance annually generates up to 160 million tons of waste bitumen pavement material, known as reclaimed asphalt pavement, (RAP) [1]. The practice of not reusing the RAP material in a timely manner will cause significant waste. Reasonable recycling and effective use of waste pavement materials has become a very urgent task. Foamed bitumen which is an environmentally friendly luting cement, is an excellent way to solve this problem [2,3]. Foamed bitumen can be utilized in a variety of construction technologies, such as foamed bitumen recycling construction technology, foamed bitumen warm mixing technology, foamed bitumen cold mixing technology, etc. However, because of various influencing factors of bitumen foaming, controlling the bitumen foaming process is quite complicated. Thus, producing high-quality foamed bitumen is quite difficult. At present, research on bitumen foaming process controlling have mainly focused on the following areas : 1) Determining the test conditions used for obtaining the optimum asphalt foaming effect; 2) exploring the main factors influencing the behavior of bitumen foaming; 3) discussing evaluation index authenticity of foamed bitumen; 4) establishing foamed bitumen recession equation according to different types of bitumen [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. See Table 1 for references. ABSTRACTIn the bitumen foaming process, the controllable factors, especially the water consumption in foaming, heating temperature of bitumen and bitumen viscosity can directly affect the technical performance of foamed bitumen. To improve the technical performance of foamed bitumen and reveal the influence rule of the controllable factors, the bitumen foaming mechanism is analyzed and the control model of the bitumen foaming behavior is established. After numerical calculation with CFD software, relation degree analysis of experimental data and simulation data was performed by utilizing the Grey relation analysis method. The average density inside the cavity flow field is used as the reference factor of theoretical analysis. Then the influence of the controllable factors on the foamed bitumen technical performance is respectively tested. The results show that the bitumen temperature affects the technical performance most significantly, water consumption of foaming secondly, and the least influentional is bitumen viscosity.