Originalscientificpaper

Croat. j. for. eng. 37(2016)2 333

Optimum Utilization of Rice Husk Ash for Stabilization of Sub-base Materials

in Construction and Repair Projects of Forest Roads

Mehran Nasiri, Majid Lotfalian, Amir Modarres, Wei Wu

Abstract

Forest roads play an important role in forest management, timber transportation and forest protection. However, minimum standards are considered for pavement materials due to the traffic volume and economic situation of forestry projects. Therefore, this paper aims to (a) evaluate the role of Rice Husk Ash (RHA) as a soil stabilizer of sub-base layer to improve the quality of materials and (b) determine the optimum utilization among 10 combinations of soil, lime and RHA regarding the environmental factors. The results of laboratory studies on soil A–6 (AASHTOO classification) indicates a general decrease in the maximum dry density (MDD) and an increase (21.9%) in optimum moisture content (OMC) with increase in RHA content. Adding RHA (9%) causes a decrease (13.3%) in liquid limit and plasticity index (PI) of soil. However, this improving effect is not as much as the influence of lime. The California bearing ratio (CBR) of stabilized soil in both saturated condition and optimum water content was 28% and 37.5% more than the natural soil, respectively. The maximum unconfined compressive strength (UCS) values were recorded for 9% RHA, 237 KN m-2 after 28 days curing time, which was 23 KN m-2 more than the natural soil. According to the results, the combination of Soil+4% Lime+9% RHA could be used as the optimum consumption of mate-rials for stabilization of sub-base layer in construction of forest roads.

Keywords: forest road, stabilization, rice husk ash (RHA), CBR, UCS, OMC, MDD

and A–7. These soils generally contain silt and clay andareclassifiedinbadtoaverageclassesintermsofroad construction (AASHTO 1986).Tohavetherequiredstrengthagainsttensilestress-

esandstrainsspectrum,thematerialsusedforcon-structingsub-baselayershouldhavesuitablespecifi-cation.Theuseofsoilstabilizersisoneofthewaystoimprove themechanicalspecificationof thesesoils(Nairetal.2008,Jamiletal.2013).Limehasbeenusedseveraltimesinforestroadprojectsasastabilizer(Péterfalvietal.2015).Thereactionbetweensoilandlimeisperformedveryslowly.Inaddition,inthepres-enceoforganicmattersinforestroadmaterials,purelimecannotbeasuitablestabilizer.However,theex-tensiveuseoflimeisharmfultotheenvironmentandroadsidevegetationintheareawithnon-calcareous

1. IntroductionForestroadsaredesignedundersubstantiallylim-

itedconditions.Inmostcases,minimumstandardsareconsideredforlayersduetothetrafficvolumeandeconomicsituationofforestryprojects.Themostim-portantpavementlayerofforestroads(accessroads)issub-baselayer,sincetheconstructionofbaselayeronforestroadsisnotjustifiedaccordingtoitsstan-dards.Severaltypesofsub-basematerialscanbeusedconsidering the type ofmaterials in borrow area,weatherconditions,numberoftrafficandeconomicsituation.Usually,borrowmaterialsareusedfortheconstruction of forest roads. Experiences have re-vealed that according toAASHTOO classification(AASHTO1986), thematerialsused for the accessroadsareusuallyplacedinclassesofA–4,A–5,A–6

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bedrock.Duetolimitationsintheuseofstabilizerssuchascementinforestroads(Khanetal.2012),ricehuskash(RHA)withahugeamountofsilicaandhighspecificsurfacecouldplayamajorroleinsoilstabiliza-tionmethodwithlime(Weitingetal.2012).GiventhatRHAisnotsuitableforcattlefeedingandit isalsonon-biodegradable,itcouldbeconsideredasaninex-pensivestabilizer.LowcostandavailabilityaswellasthestabilizationspecificationofRHAhaveledmanyresearcherstoinvestigateRHAasanalternativeforsoilstabilization(Bashaetal.2005,JhaandGill2006,Onyangoetal.2007,Nairetal.2008,Ramezanianpouretal.2009,Chobbastietal.2010,SabatandNanda

2011,Harichaneetal.2011,Milanietal.2012,Weitingetal.2012,Trivedietal.2013,Jamiletal.2013).Onyangoetal.(2007)inTanzaniausedthenatural

pozzolanastheroadpavementstabilizer.Heshowedthatpozzolanwasoneofthemostappropriatestabi-lizersinlow-volumeroadandthatitwaseconomi-cally effective.Chobbasti et al. (2010) showed thatRHAwaseffectiveinreducingtheliquidandplasticlimitsofsoil.Alhassan(2008)reportedthattheUncon-finedCompressiveStrength (UCS)would improvewiththeuseofRHAandthehighestUCSwasmea-suredby6–8%inthecombinationofsoilandRHA.Thevaluesofoptimummoisturecontent(OMC)and

Fig. 1 Map and geographical location of the study area

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maximumdrydensity(MDD)werealsoreportedinstudiesofBashaetal.2005andTrivedietal.2013.TheyconcludedthattheOMCincreasedandMDDreducedbyincreasinginRHApercent.SeveralstudieshaveexaminedtheCaliforniaBearingRatio(CBR)ofsoil(JhaandGill2006,Chobbastietal.2010,PurbiSenetal.2011,SabatandNanda2011).TheystatedthattheadditionoflimetothesoilhadquicklyaffectedthesoilCBR,whichhadincreasedovertime.ByconductingaCBRtest,SabatandNanda(2011)showedthatthead-ditionofmentionedmaterialstothesoilhadincreaseditsstrengthby20%comparedtothenaturalsoilsam-ples.Byfurtherinvestigations,itwasfoundthatmost

oftheconductedstudieswereperformedforurbanandruralroadsandimportantenvironmentalfactorshavenotbeenexamined.Theamountoflimeusedinsomeofthesestudieswasveryhighandreachedanamountof10%,whileinthisstudy,theenvironmen-talissuesi.e.theuseoflesslimeandfindingacom-binationthatimprovesthemechanicalpropertiesofsoilwereconsidered.Therefore,thispaperaimsto(a)evaluatetheroleofRiceHuskAsh(RHA)asasoilstabilizerofthesub-baselayerand(b)determinetheoptimumutilizationamong10combinationsofsoil,limeandRHAregardingtheenvironmentalfactors.

2. Materials and Method

2.1 Study AreaThisstudywasconductedinaroadofCaspian

forest (Azarroodbasin),northof Iran(Fig.1).ThelatitudeandlongitudeofAzarroodbasinare36°08′5″Nand52°45′58″E,respectively.Inthisregion,thereisamoderatemountainousclimatewithcoldwintersandhumidsummers.Theforestaltituderangesfrom360to1490metersabovesealevelandaveragean-nualprecipitationis800mm.Alborzearthdamwithaheightof72mwasconstructedinthisarea(Latifietal.2012).Therefore,duetotheearthdamandsoilero-sion,oneofthemostimportantsolutionstopreventsedimentdeliveryfromforestroadsandtostrengthentheroadmaterialsistheuseofstabilizers.

2.2 Identification of SoilAbout350kgofsoilwerecollectedfromthebor-

rowarea(excavationslopes)neartheAlborzDam.Soilswereputin50kgbagsandtransferredtothesoilmechanicslaboratory.Inthelaboratory,soilswerere-mixedwelltogetherandusedwithrespecttotheob-jectivesofthisstudy.Inordertoidentifythesoil,testssuchassieveanalysisandspecificgravity(Gs)were

done.Forthispurpose,thedriedsoilsampleswereplacedinthetopmostsieveanddrysievingwasper-formedusingamechanicalsieveshakerforamini-mumperiodof10min.Thespecificgravity(Gs)ofsoilsamplesweredeterminedusingapycnometer(ASTM-D854)andtheaverageofsoilGswasrecorded2.74.Also,theliquidandplasticlimitsofthesoilwerede-terminedinordertostudytheAterrberglimitsandclassifythesoil.AccordingtotheAASHTOsoilclas-sificationsystem,thestudiedsoilisclassifiedasA–6soilandaccordingtotheUnifiedSoilClassificationSystem(USCS),itisnamedSM(SiltySandwithGrav-el).Table1showsmoreinformationaboutengineeringpropertiesofthestudiedsoil.Inordertostabilizethesub-basesoil,atfirstrice

huskandhydrated limewereprepared fromfarmfieldsofnorthernIranandAlborzIndustrialfactory,respectively.Thetypeofusedlimeisslakedlimeandsomeof itscharacteristicsareshowninTable2.Tomakericehusk,ricehuskmustbeburnedathightem-peratures(about500°C)(Chobbastietal.2010).Afterburning,theobtainedRHAwereplacedintheopenairtocompletetheashproductionprocess(Fig.2b).SomecharacteristicsofTaromhuskashareshowninTable3(Chobbastietal.2010).

Table 1 Properties of the natural soil

Laboratory tests Rate

Liquid limit, % 39.4

Plastic limit, % 28.2

Plasticity index, % 11.2

Specific gravity, Gs 2.74

OMC, % 16.2

MDD, Mg m–3 1.54

UCS, KN m–2 214

CBROWC, % 9.5

CBR saturated, % 7.5

AASHTO classification A–6

USCS classification SM

Table 2 Characteristics of the used lime

Non Hydrated CaO %

Non Hydrated MgO %

pHCO2

%Ca(OH)2

%

1.62 0.8 11.2 0 92.8

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2.3 Mix DesignsByexaminingdifferentstudies,itcanbeconcluded

thatsoilpropertiesareoneofthemostimportantfac-torsofmixdesign.Somestudieshaveconsideredthevalueof6%oflimeconsumption(Muntohar2002);someotherproposedthevalueof10%.Accordingtotheobjectsi.e.theminimumuseoflime,acombinationof4%and6%wasconsideredinthisstudy.However,theadditionofRHAvariedindifferentstudies.Forexample,Alhassan(2008)andChobbastietal.(2010)consideredamaximumof12%and7%RHAforA–7–6andA–4soils,respectively.Inthisstudy,theRHAval-uesof5,7,9and12%wereconsideredregardingtheLiquidlimit(LL)=39.4,PlasticLimit(PL)=28.2andA–6soil,respectively.Table4showsthemixdesignofmaterials.

2.4 Methods of TestingSoilmechanics testswere designed in order to

evaluatetheeffectofstabilizers.So,materialswerepreparedaccordingtothemixdesignandstudiedus-ingtestsofCBR,UCS(7,14and28dayscuringtimes),ATERBERGandCompaction.Foramoreaccuracy,thenumberofreplicationsforCBR,UCS,ATERBERGandCompactiontestwereconsidered3 times(foreachsample).TheCaliforniaBearingRatiotest,orCBR-test,isanempiricaltest,whichisusedasanimportantcri-terioninpavementdesign.Withthistest,thebearingvalueofroadsub-baseandsub-gradecanbeestimat-ed.Inaddition,itisoneofthecommontestsforassess-ingthestrengthofstabilizedsoils.Thistestwascon-ducted in accordance with the standard ASTMD1883-07(2002)intwoconditionsofsaturationandoptimumwatercontent.Accordingtothepurposeofthestudy,thistestcanexaminethestrengthofstabi-lizedsamplescomparedtothenaturalsoilsamples.Also,theproctorcompactiontestswereperformedinaccordancewiththestandardASTMD069807E01(2002)inCBRmould;byconductingthistest,itcanbeseen

Table 3 Chemical characteristics of the Tarom husk ash (* 10-6)

P, % Mg2+, % Ca2+, % K, % Na, % SiO2, %

24.7 66.1 0.016 0.124 0.114 83.7

Fig. 2 Laboratory tests to identify specification of different combinations (a) and produced RHA and rice husk (b)

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howmuchfreespaceofaggregatesisfilledbystabiliz-ersandhowtheoptimumwatercontentisaffected.TheCBRtestiscarriedoutonmaterialpassingthe20mmtestsieve.RegardingweatherconditionsofnorthernIran,CBRsamplesaresaturatedforabout4d(Chobbastietal.2010).Soilsamplesweremovedintocylindricalplunger(proctorcylinder)andcompactedin5layerswith56blowsperlayers.TheCBRtestswere performedusing the load-measuringdevice,whichisconnectedtothecompressionmachinewiththeloadingrateof1mm/min.Themouldwiththesampleandthesurchargeweightswereplacedinthemachineandloadingratesweremeasuredatevery2.5mmdisplacementandCBRrateswerecalculatedforeachsample.Oneofthemostusefulmethodsofeval-uatingthestrengthofstabilizedsoilisUCStest.Therequiredamountofadditivetobeusedinstabilizationofsoilcouldbedeterminedbythistest.Inthisstudy,thetestwasperformedforsampleswith7,14and28dayscuringtimetoconsiderthetimefactor(Alhassan2008).ThistestwasperformedinaccordancewiththestandardASTMD2166.Thecompressiondevice(ahydraulic-actuatedloadingpistonwiththecapabilityofinfiniteratesofstrainandstressloads)wasusedtomeasuretheUCSrates(Fig.2a).Also,specialtrim-mingwasnotneededbecausetheCaliforniasamplerwasusedinthistest.Afterextrudingthesoilsample,specimenswereplacedonthebottomplateofthecom-pressionmachineandcompressionloadwasapplied.ThentheratesofUCSwerecalculated.TheATER-BERGlimitstestwasperformedinaccordancewiththestandardASTMD4318-05(2002).Accordingtothepurposeofthisstudy,thistestcanshowhowmuchtheaddedpozzolanicmaterialscouldimprovesoilprop-

ertiesintermsofATERBERGlimits.Tomeasuretheliquidlimit,about250grofthestudiedsoils(themate-rialpassingtheNo.40sieve)wereweightedandthor-oughlymixedwith15to20mlofdistilledwater.Mix-ingwasdoneonaglassplatetokeepthewholesampleat thesamemoisturecontent.The liquid limitwasmeasuredusingaCasagraundecup.Plasticlimitoffine-aggregatesinsandymaterialshaveamajorinflu-enceonthestrengthofusedmaterials.MaterialswithaPI(plasticityindex)exceedingtheallowedvaluesshouldnotbeusedonbaseandsub-baselayers,be-cause materials with higher PI have lower shearstrength.Theplasticlimitisoftenusedtogetherwiththeliquidlimittodeterminetheplasticityindex.Tomeasuretheplasticlimit,about20gofthestudiedsoils(thematerialpassingtheNo.40sieve)isneeded.Samplesweremixedwiththedistilledwaterfor10mintoformaplasticballandthenrolledoutunderthefingersonaglassplate.Therateofrollingshouldbebetween80to90strokesperminutetoforma3mmdiameter.Aftercrumbling,thepiecesofcrumbledsoilwerecollectedtodeterminethemoisturecontent.

2.5 Data AnalysisStatisticalcomparisonsweredoneusingtheSPSS

16 software to comparemeans among treatments.Data(differentcombinationofmaterials)wereana-lyzedusingANOVAandTukeyHSDtestintermsofsoilmechanicalproperties.Also, thegraphicaldis-playsweremadeusingtheSigmaPlot12.0software.

3. Results and Discussion

3.1 Compaction CharacteristicsTherewasanincreaseinOMCwiththeincreaseof

RHAcontents(Fig.3).ThetrendisinlinewithAlhas-san2008andRoyetal.2010.AccordingtoFig.3,itcanbe found that the soil OMC for combinations ofS+4L+7RandS+6L+9Rhadincreased19%and21.9%,respectively,comparedtothenaturalsoilsamples.TheincreasewasaresultoftheadditionofRHA,whichreducedthequantityoffreesiltandclayfractionandcoarser materials with larger surface areas wereformed(theseprocessesrequirewater).Furthermore,thisindicatesthatmorewaterwasneededtocompactthesoil-RHAmixtures(Ramezanianpouretal.2009).AccordingtoFig.4,addingRHAtothesoilcaused

adecreaseinMDD.ThetrendisinlinewithAlhassan2008,Bashaetal.2005,Trivedietal.2013.GiventhattheMDDforthenaturalsoilandS+6Lwas1.54Mgm-3 and1.42Mgm-3,respectively,byadding9%RHAitwaspossibletoreducethesoilMDDto1.21Mgm-3.

Table 4 Investigated mixtures and mentioned indices

Mix design Index

Soil S

Soil+6% Lime S+6L

Soil+4% Lime+5% RHA S+4L+5R

Soil+4% Lime+7% RHA S+4L+7R

Soil+4% Lime+9% RHA S+4L+9R

Soil+4% Lime+12% RHA S+4L+12R

Soil+6% Lime+5% RHA S+6L+5R

Soil+6% Lime+7% RHA S+6L+7R

Soil+6% Lime+9% RHA S+6L+9R

Soil+6% Lime+12% RHA S+6L+12R

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ThereductioninMDDcanberelatedtothereplace-mentofsoilbyRHAinthemixture,whichhasarela-tively lower specific gravity compared to the soil(OsinubiandKatte1997).ItmayalsoberelatedtothecoatingofsoilbyRHA,whichresultstolargeparticleswithlargervoidsandlessdensity(Chobbastietal.2010). The reduction in theMDDmay also be ex-plainedbyconsideringtheRHAasfiller(withlowerspecificgravity)inthesoilvoids.

3.2 ATERBERG LimitsTheresultsshowedthatthesoil liquidlimitde-

creasedwithanincreaseintheRHA(Fig.5).ThetrendisinlinewithJhaandGill2006,Onyangoetal.2007,PurbiSenetal.2011.TheliquidlimitofthenaturalsoilandS+6Lwas39.4and29.7,respectively.Accord-ingtoFig.5,itcanbefoundthat9%RHAcanreducethesoilliquidlimitto26.1%.Thecomparisonofre-

Fig. 5 Influence of RHA and lime on plastic and liquid limits

Fig. 4 Influence of RHA and lime on MDD parameterFig. 3 Influence of RHA and lime on OMC parameter

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ductionratiobetweentreatmentsindicatedthatthelimecanhaveamuchgreatereffectonthereductionofthesoilliquidlimit(areductionof10%).Thereasonforthisreductioncouldbethechemicalreactionbe-tweenthelimesandsoilthatrequiremoremoistureandprovidesthismoisturefromthesoil.Theresultsshowedtheplasticlimitdecreasedwith

anincreaseintheRHA(Fig.5).Theresultsareconsis-tentwithMuntohar2002,Trivedietal.2013.Theplas-ticlimitofthenaturalsoilandS+6Lwas28.2%and25.8%,respectively.Similartothesoilliquidlimit,thecomparisonofthereductionratiobetweentreatmentsrevealedthatlimecanhaveamuchgreatereffectonthesoilplasticlimit.

3.3 California Bearing RatioTheresultsindicatedinbothsaturatedcondition

andoptimumwatercontentthattheadditionofRHAcouldincreasethesoilCBR;however,theincreasingtrendvariedfordifferentpercentages(Fig.6).TrendsshowninFig.6areinagreementwithChobbastietal.2010,PurbiSenetal.2011,SabatandNanda2011.Inthe saturated condition, the treatment of S+4L+7RreachedthehighesteffectivenessonCBR(anincreaseof27%)andthendecreased.Alhassan(2008)reportedthat thehighesteffectivenessonCBRforsaturatedconditionwas18.5%.ThecomparisonresultsshowedthattheCBRofsaturatedconditionwas28%and19%higherthanthenaturalsoilandS+6L,respectively.TheresultsofoptimumwatercontentalsoindicatedthattheCBRreacheditsmaximumvaluesinthetreatment

ofS+4L+7R(46%)andthendropped.Themaximumdifferences recorded forCBRwere37.5%and28%higherthanthenaturalsoilandS+6L.

3.4 Unconfined Compressive StrengthAccordingtoFig.7,itcanbefoundthattheUCSdid

nothavealotofchangeswithincreasinginlime(4%limeor6%lime).TheUCSvaluesincreasedwiththeadditionofRHAtoitsmaximumatbetween7–9%RHAandthendroppedfrom12%RHA.AccordingtoFig.7,thehighestrateofincreaseinUCSoccursinthefirst28days.ThetrendisinlinewithAlhassan2008andJhaandGill2006.Alhassan(2008),statedthatthehigh-estUCSwasrelatedto8%RHAand28dayssamples.ThecomparisonresultsshowedthatthemaximumUCSofstabilizedsoil(237KNm-2)was23%and16%higherthanthenaturalsoil (214KNm-2)andS+6L(221KNm-2).ThesubsequentincreaseintheUCSisattributedtotheformationofcementitiouscompoundsbetweentheCaOHpresentinthesoilandRHAaswellasthepozzolanspresentintheRHA(Jamietal.2013).ThereasonofthisreductionintheUCSvaluesaftertheadditionof9%RHAcouldbeexcessRHAintro-ducedtothesoilandhenceformingweakbondsbe-tweenthesoilandcementitiouscompoundsformed.

4. ConclusionWeconcludedthatpozzolanicmaterials,suchas

ricehuskash(RHA),increasethematerialsqualityinsoilstabilizationmethodwithlime.Sincethericehusk

Fig. 6 Influence of RHA and lime on CBR parameters; (a) Saturated condition; (b) Optimum water content

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isanagriculturalwastematerialanditisavailableinmanycountriesatlittleornocost(1$foreachgunny-bagsinIran),theproducedashfromricehuskcanbeusedasanappropriateandinexpensivestabilizerinsub-baselayerofforestroads.So,thisstudyintroduc-esthebestcombinationofsub-basesoil,ricehuskashandlimebyexaminingtenmixdesigns:According toCBRresults, the combinationsof

S+4L+7RandS+6L+12Rhadbestperformance.Byex-amining the values of UCS, the combinations of

S+4L+9RandS+6L+9Rwereselectedasthemostef-fectiveones.AccordingtotheOMC,thecombina-tionsofS+4L+9R,S+6L+9RaswellasS+6L+12RwereselectedasthebestcombinationsandaccordingtoMDD,thecombinationsofS+4L+9R,S+4L+12RandS+6L+9Rhadalmostthesameperformance.There-sultsofsoilplasticandliquidlimitsindicatedthatthecombinationsofS+4L+9RandS+6L+9Rhadthebestperformanceinreductionofbothplasticandliquidlimits.So,accurateexaminationsbetweenthemen-

Fig. 7 Influence of RHA and lime on UCS parameters; (a) 7 days curing time; (b) 14 days curing time; (c) 28 days curing time

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tionedtreatmentsshowedthatthecombinationofS+4L+9RandS+6L+9Rcouldbeconsideredasanop-timumutilizationtostabilizesub-basematerials.Thepositive effects of these two combinations in im-provementofmechanicalpropertiesofA–6soilareshowninFig.8.However,theimportantaspectistheuse of less limedue to environmental issues sur-roundingforestroadsandeconomicsituationoffor-estroadsprojects.Thus,thecombinationofS+4L+9Rwasselectedasthebestcombinationforstabilizing

thesub-basematerialsofforestroadsduetolesscon-sumptionoflime.

AcknowledgementsTheauthorswouldliketothanktheUniversityof

SariAgriculturalSciencesandNaturalResourcesforfundingthisresearchandtoacknowledgethesupportofMr.Bozorgpour,Mr.ValizadehandMr.Savadkoohifortheir invaluableassistanceinsoilsamplingandlaboratorytests.

Fig. 8 Comparison between the natural soil and combinations of S+4L+9R and S+4L+9R in improvement of mechanical properties of materials; CBR-OPT: CBR owc; CBR-S: CBR saturated; UCS-28: 28 days curing time; Where letters in superscript differ, data are signifi-cantly different between combinations for each soil mechanical test (p<0.05)

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5. ReferencesAlhassan,M.,2008:Permeabilityoflateriticsoiltreatedwithlimeandricehuskash.AssumptionUniversityJournalofThailand12(2):115–120.

AmericanAssociationofStateHighwayandTransportationOfficials(AASHTO),1986:StandardSpecificationsforClas-sificationofSoilsandSoil-AggregateMixturesforHighwayConstructionPurposes(M145).WashingtonDC,USA.

AmericanSocietyforTestingandMaterial(ASTM),2002:TestMethodsforLaboratoryCompactionCharacteristicsofSoilUsingStandardEffort(D0698-07E01).AnnualBooksofASTMStandard.Section4Vol.0408USA.

AmericanSocietyforTestingandMaterial(ASTM),2002:TestMethodsforLiquidLimit,PlasticLimit,andPlasticityIndexofSoils(D4318-05).AnnualBooksofASTMStandard,Section4Vol.0408USA.

AmericanSocietyforTestingandMaterial(ASTM),2002:TestMethodsforCBR(CaliforniaBearingRatio)ofLabora-toryCompactedSoils(D1883-07).AnnualBooksofASTMStandard,Section4Vol.0408USA.

Basha,E.A.,Hashim,R.,Mahmud,H.B.,Muntohar,A.S.,2005:Stabilizationofresidualsoilwithricehuskashandcement.ConstructionandBuildingMaterials19(6):448–453.

Chobbasti,A.J.,Ghodrati,H.,Vahdatirad,M.J.,Firouzian,S.,Barari,A.,Torabi,M.,Bagherian,A.,2010:Influenceofusingricehuskashinsoilstabilizationmethodwithlime.FrontiersofEarthScienceinChina4(4):471–480.

Jamil,M.,Kaish,A.B.M.A.,Raman,S.N.,Zain,M.F.M.,2013:Pozzolaniccontributionofricehuskashincementitioussys-tem.ConstructionandBuildingMaterials47:588–593.

Jha, J.N.,Gill,K.G.,2006:Effectofricehuskashonlimestabilization.JournaloftheInstitutionofEngineers87:33–39.

Harichane,K.,Ghrici,M.,Kenai,S.,2011:Effectofcuringtimeonshearstrengthofcohesivesoilsstabilizedwithcom-binationoflimeandnaturalpozzolana.InternationalJour-nalofCivilEngineering9(2):90–96.

Khan,R.,Jabbar,A.,Irshad,A.,Khan,W.,NaeemKhan,A.,Mirza,J.,2012:Reductioninenvironmentalproblemsusingrice-huskashinconcrete.ConstructionandBuildingMateri-als30:360–365.

Latifi,N.,Matro,A.,Khari,M.,2012:MonitoringresultsofAlborzearthdamduringconstruction.ElectronicJournalofGeotechnicalEngineering17:2474–2484.

Milani,S.,Silva,A.,Paula,D.,2012:Physical,MechanicalandThermalPerformanceofcement-stabilizedrammedearth-ricehuskashwalls.JournalofMaterialsinCivilEngineering24(6):775–782.

Muntohar,A.S.,2002:UtilizationofUncontrolledBurntRiceHuskAshInSoilImprovement.DimensiTeknikSipilJour-nal4(2):100–105.

Nair,D.G.,Fraaij,A.,Klaassen,A.K.,Kentgens,P.M.,2008:Astructuralinvestigationrelatingtothepozzolanicactivityofricehuskashes.JournalofCementandConcreteResearch38(6):861–869.

Osinubi,K.J.,Katte,V.Y.,1997:Effectofelapsedtimeaftermixingongrainsizeandplasticitycharacteristics,soillimemixes.NigeriaSoc.Engin.TechTrans32(4):65–76.

Onyango,M.,Macha,I.,Busch,C.,2007:UseofNaturallyOccurringPozzolansforRoadConstructioninTanzania.9th InternationalConferenceonLow-VolumeRoads.June24–27,Austin,Texas.

Péterfalvi,J.,Primusz,P.,Markó,G.,Kisfaludi,B.,Kosztka,M.,2015:EvaluationoftheEffectofLime-StabilizedSub-gradeonthePerformanceofanExperimentalRoadPave-ment.Croat.j.for.eng36(2):269–282.

Purbi,S.,Mukesh,N.,Dixit,M.,2011:EvaluationofStrengthCharacteristicsofClayeySoilbyAddingSoilStabilizingAd-ditives.InternationalJournalofEarthSciencesandEngineer-ing4:1060–1064.

Ramezanianpour,A.A.,Khani,M.M.,Ahmadibeni,G.H.,2009:TheEffectofRiceHuskAshonMechanicalPropertiesandDurabilityofSustainableConcretes.InternationalJour-nalofCivilEngineering7(2):83–91.

Roy,T.K.,Chattopadhyay,B.C.,Roy,S.K.,2010:EffectofAl-ternativeMaterialsonEngineeringPropertiesofAlluvialSoilforConstructionofRoadSubgrade.ProceedingofTraf-ficandTransportationStudies1331–1340.

Sabat,A.K.,Nanda,R.P., 2011: Effect ofmarbledust onstrengthanddurabilityofRicehuskashstabilisedexpansivesoil.Internationaljournalofcivilandstructuralengineering1(4):939–948.

Trivedi,J.S.,Sandeep,N.,Chakradhar,I.,2013:OptimumUtilizationofFlyAshforStabilizationofSubGradeSoilus-ingGeneticAlgorithm.ProcediaEngineering51:250–258.

Weiting,X.,Tommy,Y.L.,Shazim,A.M.,2012:Microstruc-tureandreactivityofrichhuskash.ConstructionandBuild-ingMaterials29:541–547.

Optimum Utilization of Rice Husk Ash for Stabilization of Sub-base Materials in Construction ... (333–343) M. Nasiri et al.

Croat. j. for. eng. 37(2016)2 343

Received:October27,2015Accepted:February02,2016

Authors’address:

MehranNasiri,PhD.student*e-mail:me.nasiri@sanru.ac.ir;me.nasiri66@gmail.comAssoc.prof.MajidLotfalian,PhD.e-mail:mlotfalian@sanru.ac.irSariuniversityofagriculturalsciences and natural resourcesDepartmentofForestengineeringP.OBox576,Badeleh,Sari,MazandaranIRAN

Assoc.prof.AmirModarres,PhD.e-mail:a.modarres@nit.ac.irBabolUniversityofTechnologyDepartmentofcivilengineeringP.O.box484,ShariatiAv.,Babol,MazandaranIRANProf.WeiWuPhD.e-mail:wei.wu@boku.ac.atUniversityofNaturalResourcesandLifesciencesInstituteofGeotechnicalEngineeringP.O.Box85084,ViennaAUSTRIA

*Correspondingauthor