ABSTRACT
It is common practice in Norway to use crushed rock in road structures. Recent regulations allowed a large variation of the particle size distribution in this layer. This paper focuses on the influence of effective particle size of crushed rock materials on heat transfer in pavements based on pavement structure thermal modelling using a partial differential equation solver. The normal temperature for the 1980 – 2010 period in various regions of Norway, as well as the coldest year (extreme conditions) were used together with the factor N as surface conditions of a typical pavement structure. The crushed rock was modelled using various values of effective particle diameter (d10), a material characteristic that significantly affects thermal properties of coarse materials. Along with temperature distributions, maximum frost depths were computed and expressed according to the climatic data of each site studied and as a function of the effective particle diameter. The results showed that d10 had a significant effect on frost depth mainly during the coldest winters as a result of increased heat transfer owed to natural convection. The results obtained also made it possible to establish a critical d10 value to minimize convection as a function of the mean annual air temperature, providing a simple tool to road designers for selecting the materials for subbase and frost protection layer (FPL).
