Application Of Gray System Theory To The Design Of Asphalt Mixture

Asphalt mixture is a building materials, whose performance is extremely complicated. It has many components, such as coarse aggregate, fine aggregate, slag, asphalt or other additives. With different source material, different temperature, different production processes and different experimental conditions,every component affects the performance of the asphalt mixtures differently. This is a gray system. When designing asphalt mixture ,we find it difficult to accurately grasp the law. Conducting the research of asphalt mixture, we usually do experiments and acquire datas, then to discover the nature of asphalt mixture. Due to the limited experimental conditions, limited manpower, limited material resources, we usually acquire little data. So, asphalt mixture is a complex system,which is gray and has little data.The advantage of gray system theory is to study"some information known","Some information unknown","small sample",and"poor information"uncertaint systems.The gray system theory is to handle known information and generate new information,then to grasp the law. Gray system models do not require or restrict experimental datas specially.So,using gray system theory to analyse asphalt mixture has advantages.Gray system theory has been widely used since appeared. In the 1990s,it is applied to asphalt mixture.At present ,gray system theory is mainly applied in the following directions.(1)using gray correlation analysis method (or gray correlation entropy method)to analyse the relationship between mashall indexes and road performance;(2) using gray correlation analysis method to analyse the relationship between the asphalt chemical composition and three indexes of asphalt;(3)applying the theory of gray-clustering decision to comprehensively assess the asphalt pavement situation or construction status;(4)gray forecast model is to predict some indexes of asphalt pavement condition in long time,such as deflection and flatness.in order to maintain and repair pavement better.The paper tries to use gray system theory to determine the optimum of asphalt ,to choose the best gradation and guide the design of asphalt mixture.Above,it is mentioned that now there is a hot research ,which is to use gray correlation analysis method (or gray correlation entropy method)to analyse the relationship between mashall indexes and road performance. Obviously, it can guide the design of asphalt mixture, but not directly.This paper put forward using gray correlation entropy method to analyse the relationship between road performance and asphalt mixture gradation or asphalt amount,then to identify the key factors,and it would guide us to reasonably choose materical or content when doing the design of asphalt mixture.The paper consists of six chapters. Of these chapters, chapters three, four and five are kernels.Chapter one is the introduction. First, it analyzes the complex characteristics of asphalt mixture system,and introduces the advantages of gray system theory.Using gray system theory to analyse asphalt mixture has advantages. Then it introduces the emergence and development of gray system theory,and it focus on introducing the application of gray theory in asphalt mixture and cited the current research directions. Finally, it introduces the ideas and contents of this paper.Chapter two introduces the basic concepts and basic principles of gray system theory.It introduces the basic components of the theory and describes briefly its modeling.Gray system theory was born only 20 years ,so many people are not familiar with it.The author arranges this chapter in order to make the readers know something about the theory.Chapter three put forward using gray correlation entropy method to analyse the relationship between road performance and asphalt mixture gradation or asphalt amount.There are many factors,which affect the performances of asphalt mixture.All these factors determine the quality of asphalt mixture.When designing asphalt mixture,if we can know which is a major factor, which is a secondary factor,what factors play a role in promoting the system, what factors will not affect the development of the system.,we would be able to seize the key design process and know how to improve the performance of the mixture.First,the chapter introdyces the basic principles and methods of gray correlation analysis, then gives an example.The author analyse chiefly the relationship between road performance and asphalt mixture gradation or asphalt amount and identify the key affecting factors,then rank the affecting factors based on the size of entropy correlation and analyse the reasonableness of the order. That would guide us to reasonably choose materical or content when doing the design of asphalt mixture.Chpater four applys prediction model theory to establish GM(1,1) and GM(1,N) model according to less data,and forecasts optimum asphalt content and optimum fiber content.When determine optimum asphalt content, we generally select several asphalt content and do Marshall test,acquire Marshall indexes and compose curves,then determine optimum asphalt content.When designing the doped fiber asphalt mixture, the process becomes complicated.It needs to do a lot of tests,but the results may not be very satisfactory.This chapter uses gray prediction theory to establish forecast model according to less data,and forecast required datas,then analyse the forecast data to determine optimum asphalt content and optimum fiber content. That can save time, manpower, resources for us.First,the chapter introdyces the basic principles and methods of gray prediction model , then gives an example,and detail tell about the process of using the theory to the example. Forecast datas and the experimental results are very similar, and it shows that this method is scientific. This chapter also prepares computer programs to simplify the modeling process to facilitate the practical use.Chapter five applys gray multi-objective decision-making method to choose the best gradation in a variety of circumstances. When we design of asphalt mixtures, there are many kinds of materials,such as aggregate, asphalt, slag and other materials. The physical properties ,prices and freight rates of each material are different,different matericals combine a variety of mixtures whose nature and road performance varies. Some have good performances of anti-rutting , but poor cracking resisitance , some have good water-stability , but low-intensity . Under such circumstances, how to select a project which meets the demands and is economy? Gray multi-objective decision-making theory in this chapter will answer this question . .First,the chapter introdyces the basic principles and methods of gray multi-objective decision-making , then gives an example, detailing the application of gray decision, the analysis results agree well with the experience comprehensive analysis results. This chapter also prepares computer procedures to simplify calculation to facilitate practical application.Chapter six is the last part. And this chapter is summarization of this paper in which the content and direction are also pointed out for further study.