Tensar Research Summary - MemberClicks · Tensar International Corporation TriAx® Research & Development Project Summary project specifications to achieve a firm and unyielding subgrade

Tensar International Corporation TriAx® Research & Development Project Summary

TensarResearchSummary

EvaluationofusingTensar®TriAx®GeogridswithrecycledaggregatebasematerialsAvenue144,TulareCounty,California

Aspavement sections constructedmore than 20 yearsago come to the end of their design life and

trafficdemands increase, continual reconstruction and wideningof localandstateroads are being

performed.Manyofthese improvementsareinurbanareaswhere the timeand expense of

hauling outmaterials fromdemolishedpavement,and truckinginnew rawmaterialsto the projectsite,

are significant.Additionally,the ancillarytraffic loadingon adjacentstreetsaswellastrafficcongestion

isproblematic for the owner and residents.For these reasons using recycled materials for roadway

construction is becoming more prevalent. An economical alternative consists of crushing and

processingtheonsitematerials(ACor PCC)or usingexistingon-siteaggregatebaseasroad base.

However,manydesignersquestion theperformance of recycledmaterials for roadbase due

the inconsistency that can be created from the demolition, crushing operations or excavation

processes toproducethesematerials. Toprovideconfidence toownersanddesigners that recycled

materialscanbeused,Tensar InternationalCorporationevaluatedthe performanceofthesematerials

when usedwith TriAx Geogrid. Our data indicates the recycled material can successfully be used

withTriAxGeogrids to providea quality foundation for flexibleand rigidpavements. Byadding a TriAx

Geogridbeneath or within a recycled aggregatebase, the potential non-uniformities of the recycled

materials,aswellasprojectrisk,isminimized. Tensar approached Tulare County about incorporating TriAx

Geogrid into the roadway section of the Avenue 144

reconstruction project. Adding TriAx Geogrid between the

subgrade and aggregate base materials, is an effective

method of creating a stiffer and more uniform foundation

that will maintain integrity over timeby improving the load

transfer.Thiscomposite section of TriAx and aggregatebase

creates a mechanically stabilized layer (MSL). The TriAx

enhancementresultsinlessdeformationduringconstruction,

and duringthe pavement’s life. This is accomplished by TriAx

interlocking with and confining the aggregate base. The

confinement reduces the potential for contamination of the

aggregatebase with thesubgrade soilandthe MSLprovides

a resilient layer that minimizes the potential for differential

movements of the pavement surface that initiate structural

distress.Thisalsomoves


the critical failure layer into the surface course which creates a “perpetual pavement” that provides

preferred,costeffectivemaintenanceoptions.Additionally,anMSLwithTriAxGeogridallowsforthe

reduction of aggregate and asphalt thickness while providing equal or greater performance

benefits. Tensar proposed a reduction of ½’ of asphalt and 5.5” of aggregate base course

material. Additionally, the Tensar alternate designutilized reclaimed asphalt as aggregatebase

coursematerial. These options offered Tulare County significant savings in bothmaterials and

constructiontime.

Tensar agreed to conduct post-construction performance field validation to verify both the

performanceof theTriAxmechanically stabilized layer and todemonstrate that TriAxGeogrid

used with reclaimed asphalt pavement or other recycled materials provides equivalent or

superior performance compared to equivalent

aggregatebaseorRAPsections.

Tensar conducted multiple Automated Plate Load

Tests (APLT) to measure the improved

performance of aggregate base (recycled and

virgin aggregates) with TriAx. The thickness of the

aggregate sections tested ranged between 4

inchesand 18 inches.For thisspecifictesta nominal

9 inches of RAPwas evaluated. This material was

pulverized in-placeand loaded directly into belly-

dumps for use asaggregatebase. The exposed

subgrade was then compacted in accordance with


project specifications to achieve a firm and

unyielding subgrade. TriAx Geogrid was then rolled

out on

the subgradeand the pulverizedRAPmaterialwasplacedon theTriAx. Atestsectionwas located

within the limits of project. The followingdiagramspresentthe RAP sectionsevaluatedusing the

extendedcycle(10,000)APLTforthisproject:

Ingios® performeda seriesofAutomatedPlate Load Test’s (APLTs)

at the subject site. APLT is a system developed to perform fully

automatedstaticand repetitive/cyclicplate loadtests,per AASHTO

and ASTM test methods. For performance validation the

measured deformation between the control sections and TriAx

test sections are compared with stress dependent resilient

modulus testing and extended 10,000 cycle tests at a constant

stress.

Figure 1 andFigure 2 demonstrate thebenefit of theMSL.These graphs showthepermanentand

recoverable deformations with a 10,000-cycle plate load test with an applied pressure of about 15

poundsper square inch on a 12-inch diameter plate. This repetitive loading simulates traffic loading

over time. Inthis case the loading applied is more than double what thesurface of theaggregate

base, below the wearing surface, will experience during the life of the pavement. The critical

measurement parameterwiththistestisthe deformationofeachsystem. The controlsectionwithout

geogrid showed about 4 timesmore permanent deformation than the TriAx section over the 10,000

cycles.

Figure1:9 inchesRAP, NoGeogrid Figure2:9 inchesRAP, Geogrid


Why isdeformationsignificant?

With less deformation a more uniform surface is created. This uniform surface creates a non-

yieldingfoundationforpavingandultimatelyprovidesa betterfoundationforrigidor flexiblepavements.

Thistestshowsthe reducedpotentialfordeformationwithan MSL.

Figure3 showsthe resilientmodulusof the aggregatebase versusthe appliednormalstressusinga

12- inch diameter plate. One-hundred cycles testing were performed at different stress states,

depicted by the blue and red dots in Figure 3. The results demonstrate that 9 inches of RAP,

underlain by TriAxGeogrid, wasmore resilient to loading when compared to thecontrol section with

10inches of CrushMiscellaneousBase.


Note: Averageaggregate base resilientmodulus,similarsubgradeswithMrgreaterthan10,000psi.

Why istheresilientmodulus(Mr)of theTriAx sectionimproved? Figure4

Figure 3 demonstrates two benefits of adding TriAx to a

pavement section.Thefirst benefit is the improvedMrof

the aggregate base. This is the result of the TriAx

interlocking with and confining the aggregate base. The

confinement results in increased vertical capacity of the

aggregate base. The second benefit is the reduced

potential for Mrdegradation over multiple cycles. Typically,

the Mr of an aggregate base will degrade over multiple

cycles as the aggregate particles migratedownward into

the aggregate base (Figure 4). The unique shape and

configuration of TriAx Geogrid allow for excellent interlock

andconfinement.

Whatistherangeof grainsizedistributionsthatcanbe usedwith TriAx Geogrid?


Figure5

The chart above is a compilation of more than 13 types of aggregatebases that have been tested

using the APLTmethodto verify the improvedperformancewith TriAx Geogrid. The lines on the chart

represent the range of preferred grain size distributions that can be usedwith TriAx Geogrid. The

materialstestedincluded:

• RAP• CrushedConcrete• CrushedMiscellaneousBase• VirginAggregateBase, and;• SalvagedBase


Materials that fall between these ranges have proven to have optimal performance with TriAx

Geogrid. This includesmaterials that are 100% RAP, 100% concreteor a combination. This doesnot

excludeothertypes ofaggregatebases.However,foroptimalperformanceaggregatebasesthat

fall within the gradations above will perform better. In summary, the testing shows that TriAx

Geogrids improve theperformanceofwellgradedgranularmaterialsthroughmechanicalinterlock.

Conclusions

The testing here demonstrates that using recycled materials placed on TriAx Geogrid provides

improved performance compared to the control sectionswithout stabilization. Benefits of including

TriAxwithintheplannedpavementsectioninclude:

• Reducingdeformation• More uniformsupportcharacteristics• Improvedperformanceof theaggregatebase through confinementand reduced

subgrade soilcontamination.Thismaintainsdrainagepropertiesofthe aggregatebaseovertime.

• Enhancedperformanceofvirginaggregatesaswellasrecycledaggregates.

The resultsof the testingare consistentwiththe findingsof the AcceleratedPavementTestingofover150

APLT’sperformedon sectionsenhancedwithTriAxGeogrid.Resultscanvary dependingon the quality

ofthe aggregate,type ofgeogridand subgradestrength.

To learn more about Tensar TriAx Geogrid or opportunities for APLT testing, please contact the Tensar

Corporation.

GeneWeddle MatthewKennedy

925-9798407 510-704-3084

[email protected] [email protected]


References:

1. “InSituPerformanceVerificationofGeogrid-StabilizedAggregateLayer UsingAutomatedPlateLoad Testing,Avenue144, Tulare,California”,preparedbyDavidJ.White,Ph.D.,P. E.datedApril9, 2018.

2. AASHTO,MEPDG, 2015

3. “Full-ScaleEvaluationofGeogridReinforcedThinFlexiblePavements”preparedbyU.S ArmyEngineerResearchand DevelopmentCenter,datedAugust2,2011.

4. “PerformanceofGeogrid-StabilizedFlexiblePavements”preparedbyU.S ArmyEngineer

Researchand DevelopmentCenter,datedJuly2014.

5. “Full-scaleacceleratedtestingofmulti-axialgeogridstabilizedflexiblepavements,”Geotechnicaland structureslaboratory,Engineeringresearchand developmentcenter,June2017,reportcanbe obtainedat https://erdc-library.erdc.dren.mil/xmlui/handle/11681/22653

6. “Fieldand LaboratoryEvaluationofaMechanicallyStabilizedSalvagedBaseCourseinthe

ConstructionofUS 12Marmarth,NorthDakota”,MarkH.Wayne,Ph.D.,P.E,DavidJ.White,Ph.D.,and JayKwon, Ph.D.,P.E.,preparedforthe Mid-ContinentSymposium2011.

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Tensar Research Summary - MemberClicks · Tensar International Corporation TriAx® Research & Development Project Summary project specifications to achieve a firm and unyielding subgrade