THE BEARING CAPACITY OF PAVEMENTS WITH FROST RETARDING LAYERS. A TEST ROAD STUDY

For an extensive study of frost penetration and bearing capacity of roads with frost retarding layers of different composition and different thickness and surrounded by different types of bases and sub-bases a test road was built in western Sweden in 1966-67. During the construction period and the following year the various layers were followed up by measurement of dynamic elastic modulus by the wave propagation method, and several sections were subjected to repeated plate loading applying up to 50000 loads at each point in order to study the fatigue properties. For investigation of the development of bearing capacity the test road under traffic is followed up by measurements each year implying place bearing tests, levelling, cross profile and longitudinal profile by the CHLOE profilometer. Most frost penetration retarding materials caused an increase in rebound deflection and did in some cases cause a disastrous permanent deflection, which necessitated rebuilding. Some materials had no detectable influence upon the permanent deflection. The serviceability index as measured by the CHLOE meter decreased faster on some sections having insulating layers but showed in some sections a slower decrease than on the reference sections. The dynamic elastic modulus of the basecourse increased during the first year by more than 30% also in those having insulating layers beneath. The test road will be followed up for several years to come but has already given positive results for the frost protection aspect of road design. /AUTHOR/