Determining of Asphalt Stiffness Modulus

Abstract

This chapter deals with the development of equation that expresses the bitumen stiffness modulus as a function of time, temperature and the simple properties of bitumen such as penetration (or penetration index) and softening temperature. As mathematical model for describing the stiffness of bitumen, Christensen and Anderson (CA) equation was used. The parameters of CA model were related to the bitumen properties based on Van der Poel’s experimental data. The instantaneous value for longitudinal modulus was obtained by extrapolation of values for stiffness modulus according to Van der Poel at low temperatures and small load durations. With the purpose of extrapolation, the model developed to describe the viscoelastic properties of amorphous glass forming polymers was applied. To express the zero-shear viscosity of bitumen as a function of temperature based on Van der Poel’s data, the parameters of time-temperature superposition function were related with the penetration index of binder. The approximate formula was obtained for the exponent of power in CA model as a function of penetration index. Using developed equation, stiffness modulus of bitumen can be easily calculated in a wide range of temperatures and loading time.