Gradation Parameters Optimization Study Of The Asphalt Middle Coat

Taking a wide view on gradation design methods both China and abroad, the Bailey Method not only considers the volumetric properties of the aggregate but also provides evaluating indicator of the gradation, so it posses predominance in design the skeleton density asphalt pavement .Firstly, according to analyzing the result of mechanics calculating, the asphalt middle coat is the leading area of resisting rut based on assurance certainly pavement performance. The asphalt middle coat also need ensures appropriate VMA for preferable stability. So this paper comes up with AC-20 asphalt concrete design goals as gradation design of the middle coat.Secondly, this paper analyses the steps of Bailey method, and discusses coarse aggregate designed density and 0.075mm percent of passing.Thirdly, Twenty seven groups of gradation are designed which are satisfied the condition of stone on stone contact by ways of the Bailey Method. This paper selects a new evaluation index-complex stability index to evaluate high-temperature stability of asphalt mixture. Because each specification of aggregate interact, they act on pavement performance linearly depedently.This paper introduces the three parameters of the Bailey Method to represent the gradation of asphalt concrete and comes up with multivariant non-linear model between the Bailey parameters and high-temperature evaluation index. The same method is applied to analyze volume property, just as well come up with multivariant non-linear model between the Bailey parameters and volume index.Lastly, compromisivly considering two dedign goals of the middle coat which are based on resisting rut and ensuring appropriate VMA, this paper gives reasonable range of the Bailey parameters. It simplifies Bailey dedign steps, and the paper confirms the engineering practicality of this optimistic method for the middle coat gradation.