Investigating and modelling behavior of asphalt mixtures during road construction : with focus on transportation and unloading phases of road construction ; Undersökning och modellering av beteendet hos asfaltsblandningar vid urlastning under vägkonstruktion

Asphalt mixtures are exposed to different types of loads and conditions during different phases of road construction. Before the road is finished, the asphalt mass has been exposed to different temperatures, transshipment, and compaction which result in redistribution of the constituent materials. Depending on their properties, each asphalt mixture is expected to behave differently and may therefore require different types of handling during the construction phase. How different asphalt mixes behave and the risks of separations in different phases of construction are not fully understood. This project aimed to develop simple and effective methods to simulate some of the road construction phases at laboratory scale in order to carefully study their possible effects on the homogeneity of different asphalt mixtures. Therefore, the potential of occurring segregation during two of the least known phases of the road construction, i.e. transportation and truck unloading phases, were investigated using both laboratory and computer simulations. The results of laboratory tests indicated that the coarse graded mixture was the most sensitive asphalt mixtures among the tested ones during both transportation and unloading phases. Besides, the output of the laboratory part also suggested that the push-off technique seems to be relatively better unloading technique than the tilting one to avoid segregation for dense and gap graded asphalt mixtures; however, it was the tilting technique that appeared to be superior to the push-off for porous asphalt mixtures. Based on the results of the laboratory simulation the focus of the discrete element simulation part was on an idealized coarse graded mixture with different viscosities. Results of the computer simulation enabled investigating possible impacts of transportation and truck unloading parameters, such as road unevenness, thermal inhomogeneity inside truck trailer, change of truck trailer geometry, on causing segregation in the generated asphalt mixtures. The overall results ...