Winter Tenting of Highway Pavements: Test Program and Discussion of Causes and Mechanisms

008125172000Final ReportPDFTech ReportFHWA-NH-RD-12323CSPR-0004(6)FreezingFrigid regionsFrost heavingSodium chlorideTransverse crackingThawDesignGeotechnologyHighwaysPavementsI22: Design of Pavements, Railways and GuidewaysI23: Properties of Road SurfacesI42: Soil MechanicsUnited StatesUnited States. Federal Highway AdministrationKestler, Maureen A.Krat, Audrey S.Roberts, Glenn E.US Army Cold Regions Research and Engineering LaboratoryNew Hampshire. Dept. of Transportation. Bureau of Materials and ResearchUS Transportation CollectionTenting consists of localized frost heaving in the immediate vicinity of transverse pavement cracks. It produces a highly irregular riding surface, leads to premature pavement-surface deterioration, occurs on highways designed for high traffic volumes and to withstand freezing and thawing, and is frequently exhibited by pavements in otherwise good condition. The objective of the project discussed was to investigate causes and mechanics of the phenomenon. Several transverse cracks at four test sites were monitored for salt concentration, moisture content, subsurface temperature, freezing point depression, and heaving throughout several winter/spring seasons. Testing on New Hampshire highways was determined to be a near-surface phenomenon caused by a complex combination of factors, with the underlying cause being intrusion of road salt-sand mix into the base course. Available water (meltwater and precipitation serving as a transport medium), cracked asphalt (providing a water entry point), salt-sand mix (for winter road maintenance), freeze-thaw cycling of the base course (due to temperature fluctuations and saline-induced freezing point depression), and the phase diagram of NaCl (salt coming out of solution as freezing occurs, thereby increasing salt concentration adjacent to the freezing front, increasing the freezing point depression even further) all appear to be necessary components for tenting to occur.82