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StructuralLightweightAggregate

AllRocksAreNotCreatedEqual:ACaseStudyofSLWAinGeotechnical

EngineeredApplications

ImaniBrodieSurratt,E.I.CarolinaStaliteCompany

AboutStalite

• Foundedin1961inSalisbury,NC• ManufacturingplantinGoldHill,NC• 700ktonsofSLWAproducedin2016• Largestfacilityintheworld• SpecializeinexpandedslateSLWA

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ExpandedSlate?

• ParentMaterial=Meta‐ Argiliite– Greystriatedrockwithfoliationsthatbeararesemblancetoslate.

– Metamorphicrock• Volcanicash SedimentaryClayLayerMetamorphicRock(MetaArgiliite)

• Uwharrie Mountainsin“SlateBelt”• Meta‐Argiliite ~Slate

ManufacturingProcess

Mining Extraction ConveytoRotaryKiln

Cooling

Crushing+Screening

Transport

Expanding

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¾" ½" 3/8"

5/16" Fines

WHATMAKESSLWA“ONEOFAKIND”?

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• VitrifiedCeramic• Hardness~Quartz• ChemicallyInert• Non‐Porous• FreeDraining• TwicethevolumeperunitweightofNWA

Physical&ElectrochemicalPropertiesof¾”x#4

Property

Density – DampLoose 48pcf

Density – CompactedInPlaceMoist 60pcf

SpecificGravity(Dry) 1.45

Absorption 6%

Angle ofInternalFriction(Compacted) 40‐42°

Organic Impurities 0%

ElectricalResistance 30,000– 40,000ohm‐cm

Sulfate Content 32ppm

pH 7‐9

LAAbrasion 25‐30%

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PropertyComparisons

PropertySLWA¾”X#4

NormalWeightAggregate

Density – DampLoose 48pcf 89‐ 105pcf

Density – CompactedInPlaceMoist 60pcf 110‐ 130pcf

Angle ofInternalFriction(Φ)Compacted

40‐ 42° 26‐ 33°

pH 7‐ 9 5‐ 10

LAAbrasion 25‐ 30% 10‐ 45%

Applications

• LightweightConcrete• LightweightConcreteMasonryUnits• RoadSurfacing• Structural&LoadBearingSoil• SoilAmendment• FiltrationMedia(Stormwater,Wastewater)• Greenroof &NurseryBedMaterial

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GEOTECHNICALAPPLICATIONS

Landscape and Plaza Fills•Minimizes Dead Loads

•Free draining which helps minimize hydrostatic potential

•Due to reduced mass of fill more planters and levels can be added

•Stalite is easy to transport and install these applications

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Bulkheads and Retaining Walls•Reduces soil thrust and bending moments

•Reduces pressures against both the abutment and the end slope

•Allows for free drainage

•Improves embankment stability

Repair and Rehabilitation

•Reduces dead load on existing structure

•Stalite is very durable with controlled gradations allowing for uniform in place density and load distribution

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Fill Over Poor Soils and Marsh Lands

•Poor construction sites can be reclaimed and developed

•Long term settlement is controlled and reduced

•Design elevations can be achieved with much lower fill weights than when using conventional fill

•Controlled fill allows uniform load distribution

Waterfront Structures

•Allows economical modification of marine terminals

•Reduces lateral thrust and bending moments

•Allows increased dockside draft

•Allows for free drainage and control of in-place density

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•Reduces dead load on buried pipes and structures

•Minimizes hydrostatic potential

•Allows for higher fill construction over buried pipes and structures

•Provides thermal insulation to underground pipes and structures

•Economical alternative to flowable fill

Underground Conduit and Pipelines

TestingStandardsforGeotechnicalApplications

• ASTM–C330‐14–C191–D2794–D3080–D4253–D4254

• AASHTO–T104–T288–T289–T290–T291

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CASESTUDY:JAMESF.BYRNESHIGHSCHOOLDUNCAN,SC

JamesF.ByrnesHighSchoolPhaseI&IIConstruction

• Location:Duncan,SC• 2015‐2016AcademicSchoolYear

• Engineer:BailyandSonEngineering,Inc.

• SiteCivilContractor:McKnightConstruction

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ProjectScope

• Demolishexistingclassroombuildingfromoriginal

• Constructanewmulti‐storyclassroomwing

GeneralProjectInfo

– Phase1of4– ConstructionTimeline

– September2015throughMay2016

• Duringtheacademicyear!

• Fullyfunction,fullcapacityhighschool

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GeotechnicalScopeofWork

– 7500TonsofLightweightEstimated

– Blastintoexistinghillside(15+feetvertically)

– Stabilizetheexposedslope– Constructapoured‐in‐placeconcreteretainingwallin4segmentstofurtherstabilizeandsupporttheslope

– Backfillthoseretainingwallswith7500TonsofStalite¾”

GeotechnicalDesignConstraints

– Mainschoolbuildingsexiston265’EL– ConstructionSiteConstraints:

• Schoolpropertyelevationdrops20+feetverticallywithin>500linearfeet

• Phase1additionsweretobeconstructedona~200feetofthatslope• Ahistoricbuildingwastobeprotectedfromconstruction.

– EasementforUnloading+StagingArea• DrivewaytoexistingCafeteriaontheexistingcampus(singlecarwidth)atelevation~265’

• DrivewaytoFieldhouseandathleticfacilitiesatelevation~255’• EasementbetweenthenewclassroombuildingandtheHistoricBuilding(oldgymnasium).

– Foundationandexteriormasonrywallswereconstructedconcurrenttotheretainingwallconstruction

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WhySLWAWasSpecified?

ExpeditetheconstructiontimelineEaseofcompactionHighAngleofInternalFriction=LessBackfillMaterialDecreasedloadingonfoundationsofhistoricstructuresonsiteIncreasedSlopeStability

ConstructionSite

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NOTABLEPROJECTS

CATSI‐485LightRailStation–Charlotte,NC

• Contractor– CrowderConstruction

• GeotechnicalEngineer– F&R

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MSEWallonI‐40WesternLoop–Greensboro,NC

• Contractor– ArcherWestern

• GeotechnicalEngineer– NCDOT+FosterGeotechnical

PentagonSecuredEntrancefromI‐395– Washington,D.C.

• Contractor– Fachinna Construction

• GeotechnicalEngineer– Mactec

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HistoricRockWallPreservationonSaludaRiver– Columbia,SC

• GeotechnicalEngineer– F&ME

NC133BridgeApproach–Wilmington,NC

• Contractor:APAC • GeotechnicalEngineer– NCDOT

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InSummary

Allrocksarenotcreatedequal

SLWA=Multifacetedgeotechnicaldesignsolution