Application Research Of Granite In Upper Layer Of Asphalt Pavement In Megathermal And Rainy Areas

Along with the fast development of highway in China, aggregates used in asphalt aavement, such as basalt and limeston, are difficult to meet the construction needs of the current high grade asphalt pavement, due to uneven regional distribution, insufficient deposits of the local area. Granite is widely distributed in our country, and it is rich in reserves. However, it would lead to loose pavement, pit and other early damage to the road, for the poor adhesion with asphalt as pavement material and easy to peel off under the action of water. Currently granite is seldom used by asphalt pavement. It has important social significance and economic value to the highway construction and environmental protection in our country to research and solve the defect that using granite as pavement material.This paper studied systemically granite aggregate, asphalt mortar, granite asphalt mixture, and put forward related evaluation methods and evaluation indexes around the granite aggregate and asphalt adhesion. Relying on the solid engineering, the granite stone was successfully applied to the asphalt pavement, and the following results were obtained.Firstly, the investigation and sampling of granite aggregate has been carried out in Hainan Province about test and preliminary screening of the conventional index of coarse aggregate. Image representation method was used to evaluate the contour shape and edge of granite coarse aggregate. The evaluation method and evaluation index of the shape characteristics of aggregate are presented, which provide reference and basis for the selection of asphalt pavement of Expressway.Secondly, scanning electron microscope (SEM) was used to study the characteristics of the adhesion interface between granite and asphalt. Image processing and computer programming were used to obtain characterization of the surface profile of asphalt and aggregate adhesion, to establish the relationship with adhesion and to propose a microscopic evaluation method of adhesion.Furthermore, by adhesion test, and using dynamic shear rheometer (DSR) to research viscoelasticity of asphalt mortar which add a certain amount of stripping agent, the best amount of anti stripping agent was determined.Combined with anti stripping scheme, the design and optimization for Mix proportion of granite asphalt mixture were carried out, which added ideal granite asphalt mixture. In view of the high temperature and rainy weather conditions, the test conditions of the Hamburg rutting test and water damage sensitivity test were used to study the durability of the mixture, and verify the anti stripping method.Finally, based on the real project, this paper applies the research results to the test road. Through field testing and sampling laboratory test, the result indicated that the granite asphalt mixture that using the mix ratio design and anti stripping method in this paper had good water damage resistance and high temperature resistance to rutting durability, which can completely meet the requirements of high grade asphalt pavement.