Prediction of fatigue performance

Some laboratories and organisations have developed various methods/techniques (equations or nomograms) from which the fatigue performance of asphalt can be predicted more easily with reasonable accuracy. The predictive methods are based on asphalt stiffness, bitumen properties (penetration index, volume of bitumen or softening point) or air voids. 

A method for predicting the fatigue life of asphalts by the use of a nomograph has been developed by Bonnaure et al. (1980). The required data are percentage volume of bitumen, V, penetration index of the bitumen (PI), stiffness modulus of the mixture, d initial strain 

In the first approach, the permissible asphalt strain to fatigue, can be predicted when two parameters are known the stiffness modulus of the asphalt and the volume of the bitumen in the mix. The equation developed is as follows (Shell International Petroleum Co. 1978 Van Dijk 1975)  

Another nomograph was developed by Cooper and Pell (1974) referring to dense-graded macadams and hot rolled asphalts. The nomograph is expressed by the following mathematical equation  

---