Prediction of asphalt stiffness

If the laboratory determination of the stiffness of bituminous mixtures is not feasible, the stiffness can be estimated by empirical methods. 

The volume of bitumen and the volume of the mineral aggregates in the mixture are easily determined by volumetric calculations. 

The University of Nottingham has also developed a method for calculating asphalt stiffness (Brown 1980). The data required are the stiffness modulus of the bitumen, in pascals, determined from Van der Poel s nomograph, and the voids in the mineral aggregate (VMA). The equation used to calculate the stiffness is as follows  

Both methods/procedures can only be applied when the stiffness of bitumen exceeds 5 MPa, and for the Nottingham method, it can be applied only to asphalts with VMA values ranging from 12% to 30% (Bonnaure et al. 1977 Brown 1980). 

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