Development of test method for determination of stiffness modulus

There is a great variation between the laboratories when determining the stiffness modulus of bituminous pavements. This is a problem in connection with the evaluation and control of the stiffness modulus of bituminous pavements performed by different laboratories. It is also an obstacle with reference to the stiffness modulus of bituminous pavements in connection with performance based contracts. Stiffness modulus is also an important parameter when designing road structures. Inaccuracy about the measured stiffness modulus can lead to unreasonable thicknesses of pavement layers. In an earlier study concerning the determination of stiffness modulus, it was stated that the comparative tests showed that there is a great variation both within and in-between the results of different laboratories. The aim is to refine the test method for determining the stiffness modulus in a way that partly leads to less variation between stiffness modulus measurements performed by different laboratories, partly to increased knowledge of different apparatuses used in Sweden. This is done by controlling and comparing the load pulse and the resulting deformation pulse when using variable loading. Force and deformation were registered by different systems (additional stress and strain gauges). Dummy specimens, with more stable characteristics than bituminous test specimens, were used as a completion to the calibration and for the analysis of stress, deformation, loading time and pulse of different apparatuses