ABSTRACT
ABSTRACT: The modeling of asphalt materials to produce master curves is becoming more important in the development of pavement design methods. However, the current method being applied in the USA in the Mechanistic-Empirical Pavement Design Guide (MEPDG) uses a symmetrical sigmoidal model. This model can clearly be shown not to apply to many types of asphalt materials. This paper presents several additional approaches with different sigmoidal models which can be assessed within a mechanistic-empirical framework. This analysis is anticipated to be important as materials containing more modifiers are used and/or the greater use of materials not typical of those used to develop the original sigmoidal model adopted by many researchers. The generalized logistic sigmoid known as a Richards curve is a widely-used and flexible sigmoidal. Various forms of this generalized model are assessed and discussion is presented with relation to using this curve to describe the shape of a mastercurve of complex dynamic stiffness modulus of bituminous materials. The analysis shows that for the materials evaluated a generalized model format works very well. In addition, the data shows that the resulting master curves are non-symmetrical about a point of maximum gradient.
