Seasonal variation in material properties of a flexible pavement

Seasonal variation of temperature and moisture causes considerable changes in the load-carrying capacity of pavements in geographical areas subjected to extreme freeze/thaw conditions. The Seasonal Monitoring Program (SMP) of the Long Term Pavement Performance (LTPP) study of the Federal Highway Administration (FHWA) monitors seasonal variations in Falling Weight Deflectometer (FWD) deflections, air temperature, rainfall, soil temperature, moisture content, and soil electrical resistance at numerous sites across North America. This study relates changes in pavement load carrying capacity represented by the pavement layer resilient moduli to selected environmental factors for a test pavement site in southwestern Manitoba. The significant environmental parameters causing seasonal variation in pavement layer resilient moduli are identified as the surface temperature for the asphalt layer and the thawing index for base and subgrade layers. The resilient moduli of various pavement layers show a substantial decrease in magnitude with increasing values of respective environmental parameter. The present model can be used for preliminary verification of empirical pavement design and rehabilitation practices currently in use to account for seasonal variations.