Presentation title Month XX, 2013

A Comparison of Pavement Foundation Stabilization TechnologiesPeter J. Becker, M.S.Graduate Research AssistantCenter for Earthworks Engineering Research (CEER)pbecker@iastate.edu

David J. White, Ph.D., P.E.Associate Professor and holder of Richard L. Handy ProfessorshipDirector, Center for Earthworks Engineering Research (CEER)Department of Civil, Construction and Environmental EngineeringIowa State Universitydjwhite@iastate.edu Center for Earthworks Engineering ResearchCenter for Earthworks Engineering Research1This presentation will compare the performance of different pavement foundation stabilization techniques used at the Central Iowa Expo (CIE) roadway reconstructionProject overviewPerformance (as constructed, freeze-thaw, & recovering)Cost analysis

2Center for Earthworks Engineering ResearchThe testing area encompasses 24 test sections distributed over 12 north-south roads 3

Center for Earthworks Engineering ResearchPrior to reconstruction, each test section comprised the following cross section4GRANULAR BASEA-1-a (SM)SUBGRADEA-6(5) (CL)BIAXIAL GEOGRIDExisting ProfileCHIPSEALCOATING8

Center for Earthworks Engineering ResearchRoadways were reconstructed with different pavement foundation stabilization techniquesControlMechanical stabilization of subgrade (Mix A-1-a with A-6(5))Geocell-reinforced subbase (4 in. and 6 in.)Geotextile fabric (non-woven and woven)Polymer grid (biaxial and triaxial)5% cement stabilized subbase5% cement and 0.4% fiber stabilized subbaseFibrilated polypropylene (FP) and monofilament polypropylene (MP) fibersRecycled subbase10% cement (PC) stabilized subgrade10%, 15%, and 20% fly ash (FA) stabilized subgradeHigh Energy Impact Compaction (Converted to control section)

5Center for Earthworks Engineering ResearchPerformance was measured using the following in situ testing equipment6

Falling Weight Deflectometer (FWD)Dynamic Cone Penetrometer (DCP)

Center for Earthworks Engineering ResearchMechanical stabilization of subgrade is the mixture of good quality geomaterial with poor quality subgrade 7

Center for Earthworks Engineering ResearchGeocells use confinement to strengthen geomaterials8

Center for Earthworks Engineering Research8Geotextile fabrics provide separation and filtration for pavement layers9

Woven Geotextile FabricNon-woven Geotextile FabricCenter for Earthworks Engineering ResearchPolymer grids provide planar reinforcement to pavement layers10

Center for Earthworks Engineering Research

Cement stabilization (of subbase) increases strength and stiffness. Fiber stabilization increases toughness, shear strength.11

FP FibersMP FibersCenter for Earthworks Engineering ResearchRecycled subbase test section included 6 in. nominal subbase below modified subbase layer12

Center for Earthworks Engineering ResearchCement stabilization (of subgrade) increases strength and stiffness13

Center for Earthworks Engineering ResearchFly ash stabilization (of subgrade) increases strength and stiffness14

Center for Earthworks Engineering ResearchCement stabilized sections yielded comparatively higher modulus values overall from FWD testing15

Center for Earthworks Engineering Research15Cement stabilized sections yielded comparatively higher modulus values overall from DCP testing16

ModifiedSubbase LayerSubgrade orRecycledSubbase LayerCenter for Earthworks Engineering ResearchInvestments in foundation stabilization will increase modulus and can potentially lead to better pavement performance17

Center for Earthworks Engineering ResearchCorrelations were made between FWD modulus and DCP penetration index18

Modified Subbase LayerSubgrade or Recycled Subbase LayerCenter for Earthworks Engineering ResearchMultivariate statistical analyses showed that the surface subbase elastic modulus layer becomes statistically insignificant during the spring thaw19TermEstimateStandard Errort RatioProb. > tStatistically SignificantR2 Adj.October 2012 Testinglog(EFWD) = b0 + b1log(PICLS) + b2log(PISG or RSB)bo10.4690310.11284792.77