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 Adm inistration (FHWA) monitors seasonal variations in Falling Weight Deflectom eter (FWD) deflections, air temperature, rainfall, soil temperature, moistu re content, and soil electrical resistance at numerous sites across North A merica. This study relates changes in pavement load carrying capacity repre sented by the pavement layer resilient moduli to selected environmental fac tors for a test pavement site in southwestern Manitoba. The significant env ironmental parameters causing seasonal variation in pavement layer resilien t moduli are identified as the surface temperature for the asphalt layer an d the thawing index for base and subgrade layers. The resilient moduli of v arious pavement layers show a substantial decrease in magnitude with increa sing values of respective environmental parameter. The present model can be used for preliminary verification of empirical pavement design and rehabil itation practices currently in use to account for seasonal variations.