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Comparison between the Los Angelesvalue and degradation from traffic load
by Håkan Arvidsson
VTI (Swedish National Road and Transport Research Institute)
SE-581 95 Linköping Sweden
Summary
Since 2004 the Swedish Road Administration has had requirements on unbound base
layer concerning the resistance to fragmentation, the Los Angeles-value. To study how
degradation from traffic load is affected by resistance to fragmentation five materials
with different Los Angeles-values were tested in VTI’s Heavy Vehicle Simulator
(HVS).
The degradation from the wheel load has been recorded by comparing the grain size
distribution before and after the HVS test. Some values from the grain size distribution
have been used or calculated to easier compare the grading curves with the Los
Angeles-value, e.g. content of fines (material < 0.063 mm) or the area under the grain
size distribution curve.
There is a clear degradation from the wheel load of the HVS in unbound base layer
materials. There is, however, not a clear connection between this degradation and the
resistance to fragmentation, Los Angeles-value. Therefore it is not possible from this
investigation to recommend a new level or category of requirements concerning the
resistance to fragmentation on unbound base layer material.
The most important conclusion is that the method that has been used in this project is
working to study the degradation and particle relocation in unbound layers.
VTI notat 4-2011 7