Considerations in Performing Full Depth Reclamation in Cold Climates - PowerPoint Presentation

1. Considerations in Performing Full Depth Reclamation in Cold ClimatesTodd Thomas, P.E.Colas Solutions, Inc.

2. OutlineFull depth reclamation (FDR)Role of pavement in cold climatesProject selection guidelinesMix design considerationsConstruction considerationsPerformanceEnvironmental and cost advantagesSummary and conclusions

3. DefinitionsFDR – full depth reclamation construction processRAP – reclaimed asphalt pavement, created from the reclaimer grinding the asphalt pavementEATB – emulsified asphalt treated base, created when asphalt emulsion is mixed by the reclaimer with the reclaimed materials

4. Full Depth ReclamationFull Depth Reclamation (FDR) is a pavement rehabilitation technique in which the full flexible pavement section and a predetermined portion of the underlying materials are uniformly pulverized and blended together to produce a homogeneous stabilized base course.Common additives:Asphalt emulsionFoamed asphaltCement or fly ashThis presentation focuses on FDR with asphalt emulsion – asphalt emulsion treated base

5. Why RecycleCorrect pavement defectsIncrease structural capacityGeometry – Limited elevation rise or limited widthReuse valuable resourcesEconomicsReduce environmental impact

6. Typical Pavement Deteriorationand preservation or treatment method

7. Full Depth ReclamationSpread add-stone in front of reclaimer, if anyPre-pulverize the bituminous surface at the specified depth (4”-8”) while adjusting moisture contentShape pulverized material to proper grade and cross slopeCompact lightly to avoid moisture loss / carry traffic for short timeSpread dry additive if neededPerform mixing pass at specified depth while simultaneously mixing water and/or emulsion and mixingRoll with padfoot roller and remove pad marks with graderPadfoot roller sometimes not needed with 4” to 6” thicknessShape with graderFinal compaction – creates emulsified asphalt treated base

8. Full Depth ReclamationSource: NCHRP Synthesis 421

9. Role of Pavement in Cold ClimatesDistribute loads from heavy trafficEffective pavement designProtect frost-susceptible soil to prevent frost-heaveEffective side drainage or internal drainageSufficient thickness above frost-susceptible soilReduce effects from environmental-related damageDifferential frost heave movementSpring-thaw weakening

10. Role of EATB in Cold ClimatesReduces water infiltrationReplace air with asphalt in the granular baseReduces moisture susceptibility of granular base courses, thereby having better resistance to frost heave and spring-thaw weakeningCoat fines and reduce or eliminate water penetrationThicker bituminous structure moderates the freeze-thaw cycling effects in the pavement-> Reduce water penetration / reduce moisture susceptibility / create thicker layer

11. Project Selection ConsiderationsCurbed streets, highways, county roads. Paved or gravel roads.Typical blendsCan be 0% RAP to ~90%Asphalt thicknessReclaiming thickness usually 4 - 8 inchesReclaimer must go under asphalt layer

12. Project Selection ConsiderationsAggregate base thicknessEnough to stay out of subgradeSome subgrades may be suitable (sand, gravel)Stay out of clay or material with large stonesDrainageWell draining structures for curing and long-term durability is importantProper depth shoulders for GWTIf widening, ensure uniformity of materials across the pavement width due to differential frost heave?

13. Mix Design ConsiderationsMaterial evaluationNo. 200 on the RAP/aggregate blend typically < 20% for optimum performanceCleanliness of finesSE typically > 30 for optimum performanceAlternatively, PI < 6Use cement or lime if P200 is high or SE is lowUsually 1 to 1.5%Design emulsion content typically 3 to 6%65% residueLower emulsion content for higher percentage of RAP

14. Mix DesignSuperpave gyratory compaction or Marshall compaction – 30 gyrations or 50-blow Marshall hammerEarly strengthFor estimating ability to open to traffic after finish rollingFor understanding emulsion curing characteristicsUnderstand effects of additional lime or cementTesting time and temperature for local conditionsTests – Marshall stability or cohesiometer

15. Mix Design ConsiderationsMoisture susceptibilityTensile strength ratio (AASHTO T-283), with or without freezing. Affected by emulsion content, presence and amount of dry additive, and P200 quantity / qualityTube suction (Tx 117E). Sensitivity to moisture due to capillary action.Improved with cement or limeResilient modulus at 25°C – 150,000 psi or higher

16. Mix Design ConsiderationsThermal crackingAASHTO T-322, Determining the Creep Compliance and Strength of Hot-Mix Asphalt (HMA) Using the Indirect Tensile Test DeviceAETB mixtures can be designed to have good cold-temperature performancePredicted low temperature of pavement in Anchorage area:-30°C at surface-27°C at 3 inches depth

17. Construction ConsiderationsConstruction temperature 40°F and risingAt least 7 days before freezing temperatures (though hard to predict)Traffic allowed on EATB after finish rolling, assuming properly designed and constructed projectMay need to limit heavy trucksTypically 3 to 10 days before overlay or seal is appliedConsider a fog seal until overlay is placed to protect from rain and trafficMinimum double chip sealCement or lime aids in cure time

18. Performance - ExampleMnRoad high-volume road: I-94 WBPredicted low temperature of pavement:-32°C at the surface-28°C at 3 inches depthAll three mixes exceeded requirements27” annual precipitation6” or 8” EATB overlaid with 3” HMA3,500,000 ESALs – designed for 5 yearsOpened February 2009 – 60% of design traffic (2.2M ESALs to April ‘11)Performing well - No transverse cracking or performance issues4% emul3% emul0.75% emulFrost-susceptible soilMnRoad – “Improving the way we construct and maintain our highways in cold weather climates.”

19. The Environmental Road of the Future, by Pierre T. Dorchies of Sintra. Presented at the 2008 Annual Conference & Exhibition, Toronto, OntarioFrom: Energy, Emissions, Material Conservation and Prices with CRM for Flexible Pavement, by Chris Robinette and John Epps of Granite Construction. TRB 2010 Annual Meeting CDProductProjectEnergy ConsumptionFor the materials, manufacturing, hauling, and placement

20. GHG Emissions CO2 eq.For the materials, manufacturing, hauling, and placementThe Environmental Road of the Future, by Pierre T. Dorchies of Sintra. Presented at the 2008 Annual Conference & Exhibition, Toronto, OntarioFrom: Energy, Emissions, Material Conservation and Prices with CRM for Flexible Pavement, by Chris Robinette and John Epps of Granite Construction. TRB 2010 Annual Meeting CDProductProject

21. Economics of FDRInitial cost savings of 25% to 33% or higher compared to the cost of reconstruction have been realizedCase Study – 0.8 mile city street with 4 to 5 lanes3000 fewer loads of materials were trucked on and off the projectConstruction time was reduced from 120 days to 40 days

22. Summary & ConclusionsIn-place recycling is a cost-effective treatment for improving pavement conditionEATB reduces water infiltration in the pavement structure and reduces moisture susceptibility of granular basesEATB, when properly designed and constructed, is resistant to moisture damage and thermal crackingUse lime or cement to aid in curing and moisture susceptibilityProven cold temperature performanceFDR is a lower energy and lower GHG option compared to reconstructionEATB behaves like a lower stiffness HMA layer

23. Summary & ConclusionsFor more information on FDR and in-place pavement recycling and soil stabilization:www.arra.org