Jämförelse mellan mekaniska egenskaper och nedbrytning av hjullast: del 2

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To study the correlation between the degradation of unbound base layer and mechanical properties (primarily Los Angeles test but also micro Deval test) a number of materials has been exposed by wheel load of VTI’s Heavy Vehicle Simulator (HVS). The first round was performed during the winter 2010–2011 and the second round during the following winter. In each round there were five materials tested. In the second round there were four new materials and one “old” as reference material. In this report results from round II will be presented, as well as some common results from both of the rounds, I and II. The results from round 1 are presented in VTI notat 4-2011. (Håkan Arvidsson: Comparison between the Los Angeles value and degradation from traffic load).The degradation has been defined as the difference in grain size distribution before and after HVS test. The degradation can be described in several ways. One way is as the difference in the area under the grain size distribution curve, another way is to sum the difference in percentage passing for all sieves or a few, e.g. the increase of fines by using results from the sieves 0.063–0.125 mm. The rutting has been measured by laser. The rutting is inversed proportional to the increase of fines. The increase of fines probably increases the stability in this quite coarse base layer grading. The materials with less increasing of fines have most of the hard minerals (quarts and plagioclase). The conclusion of these two tests on unbound base layer materials is that you partly can explain the degradation (change of grain size distribution) with mechanical properties (like Los Angeles and micro Deval). The correlations confirm this explanation and depend partly on an extreme material. Hellman et al (2013) show that degradation and crushing of the aggregates during compaction have a correlation with mechanical properties by studying microstructure and degree of crushing in microscope. Therefor the conclusion is that there is a degradation and crushing of aggregates in unbound base layer materials exposed by compaction and heavy traffic load.

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