Hoy [1998] concluded from experiments with containers of different sizes that no walleffect
has to be taken into account since the packing density in a small container was
the same as in a large container. This might, however, be the result of different levels of
compaction. In contrast to the results of Hoy, higher packing densities were obtained in
a larger container, which is reflected in the wall-effect (Fig. 4.2). The walls increased the porosity in case only fibres were tested. In contrast, such an increase of porosity was not
observed once the fibres were mixed with aggregates. The aggregates completely filled
the space between the walls and the fibres. To take this fact into account, the
experimental packing density of the fibres must be adjusted for the wall-effect, which
increases the virtual packing density. The effect of including the walls is reflected by the
improvement of the accuracy from approach A1 to A3. In the following, approach A3 is
applied to predict the packing density of the granular skeleton of SCFRC.