Components and mix design

Three stages in mix design (zoom)

Three stages can be distinguished in the design of bituminous mixtures:

  • stage 1: choice of components;
  • stage 2: theoretical mix design;
  • stage 3: verification by testing.

The appropriate choice of materials is based on knowing how the characteristics of the components affect the characteristics of the mixture. This knowledge has been gained through a considerable number of research projects addressing this topic.

The theoretical mix design aims at achieving an appropriate composition by volume. This requires the most accurate possible calculation of the voids in the mineral aggregate, which are to be partly filled with binder. In addition, the ratio between the volume of filler and the volume of binder plays an important part in the stiffness of the mastic. The calculation method designed for that purpose at BRRC is implemented in the PradoWin software package. Some characteristics of the mixture, such as stiffness, can be predicted in this stage as well, from the characteristics of the components and the mix composition by volume.

Finally, the outcome of the analytical mix design process needs to be verified by testing. Depending on the test results, either the choice of components or their proportions in the mixture can be further optimized.

As part of this activity, BRRC constantly works on improving the PradoWin software. The results of new research in this field are included. Updates are regularly disseminated to the users, and BRRC frequently organizes training sessions for them.