Performance evaluation of structural properties for soil stabilised using rice husk ash

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  • This article was downloaded by: [The University of Manchester Library]On: 04 December 2014, At: 09:35Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

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    Performance evaluation of structuralproperties for soil stabilised using ricehusk ashAditya Kumar Anupama, Praveen Kumara & G.D. Ransingchung R.N.aa Department of Civil Engineering, Indian Institute of TechnologyRoorkee, 247667, Roorkee, Uttarakhand, IndiaPublished online: 11 Mar 2014.

    To cite this article: Aditya Kumar Anupam, Praveen Kumar & G.D. Ransingchung R. N. (2014)Performance evaluation of structural properties for soil stabilised using rice husk ash, RoadMaterials and Pavement Design, 15:3, 539-553, DOI: 10.1080/14680629.2014.891533

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  • Road Materials and Pavement Design, 2014Vol. 15, No. 3, 539553, http://dx.doi.org/10.1080/14680629.2014.891533

    Performance evaluation of structural properties for soil stabilised usingrice husk ash

    Aditya Kumar Anupam, Praveen Kumar and G.D. Ransingchung R. N.

    Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, Uttarakhand,India

    (Received 15 April 2013; accepted 31 January 2014 )

    The present study aims to stabilise local clayey soil with a varying percentage of rice husk ash(RHA). The RHAwas collected from rice milling located near Roorkee city. As this material isabundantly available in the local area, efforts have been made to investigate the potential of theRHAsoil mixtures with respect to shrinkage limits, compaction characteristics, unconfinedcompressive strength (UCS), triaxial test, split tensile strength test and the California bearingratio (CBR) after subjected to different humidity conditions, so as to utilise in road construction,if found suitable. The laboratory results indicate that admixing of RHA decrease the maximumdry density, but increased optimum moisture content with increase in RHA content. Inclusionof RHA not only improved CBR, UCS and split tensile strength of clayey soil but also, shownconsiderable improvement on cohesion and angle of internal friction too.

    Keywords: clayey soil; RHA; California bearing ratio; unconfined compressive strength;triaxial test; split tensile strength

    1. IntroductionRice husk is profusely available in rice producing countries like China, India, Indonesia,Bangladesh, Brazil and South East Asia. Rice husk is mainly used as a fuel in industries inboilers for process energy requirements and for power generations. Rice husk is a fuel havinghigh ash content, varying from 20% to 25% of rice husk and content having 8090% of silica. Inthe majority of rice producing countries much of the husk produced from the processing of rice iseither burnt for heat or dumped as a waste. India alone produces around 120 million tons of ricepaddies per year, giving around 24 million tons of rice husk and 4.4 million tons of rice husk ash(RHA) every year (Govindarao, 1980). Farm income can be increased both directly and indirectlyif economically profitable means of utilising rice husk generated are utilised in industry or roadsector. There are many reported uses of rice husk such as a fuel in brick kilns, in furnaces, in ricemills for the parboiling process, as raw material for the production of xylitol, furfural, ethanol,acetic acid, lignosulphonic acids, as a cleaning or polishing agent in metal and machine industryand in the manufacturing of building materials, etc. (Govindarao, 1980).Indian clayey soils can be problematic for direct utilisation of subgrade construction. Clayey

    soil applies to soils that have the tendency to swell when their moisture content is increased.Soils containing the clay mineral montmorillonite generally exhibit these properties. The clayeysoils have a low bearing capacity in the presence of water and more shrinkage cracking in the

    Corresponding author. Email: addiknit03@gmail.com

    2014 Taylor & Francis

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  • 540 A.K. Anupam et al.

    dry condition. Admixing some percentage of cement or cementitious material with soil improvesthe bearing capacity, but crack formation due to shrinkage cannot be minimised. Hence, highwayengineers are making a constant effort to find the right material that really has the potential toimprove the bearing capacity as well as improve the shrinkage cracking control. In the presentstudy, efforts have been made similarly in this direction, by utilising RHA as an admixture toimprove and strengthen the properties of clayey soil. The long-term performance of the structuralproperties for soil admixed with RHAwas evaluated in the laboratory by conducting tests like theshrinkage limit, standard Proctor, the California bearing ratio (CBR), the unconfined compressivestrength (UCS), triaxial and the split tensile strength test.

    2. BackgroundSeveral studies havebeen carried out on the effectiveness of clay stabilisation byRHAadmixing. Inthis context, Basha, Hashim, Mahmud, and Muntohar (2005) studied the stabilisation of residualsoils by chemically using cement and RHA. They evaluated compaction, strength and X-raydiffraction of such properties of the soil. It was observed that cement and RHA reduced theplasticity of soils. In general, 68% of cement and 1015% RHA show the optimum amount toreduce the plasticity of soil. They observed that the addition of cement and RHA increased theoptimum moisture content (OMC) and diminished a certain amount of maximum dry densities(MDDs) that correspond to increased cement and RHA percentage. It has been reported that theoptimum cement content is 8% without RHA. The CBR value determined was maximum at 4%cement and 5% RHA mixtures with soil. According to the compressive strength and plasticityindex parameters, 68% of cement and 1520% RHA showed the optimum amount required toimprove the properties of soil.Muntohar (2011) stabilised clayey soil with lime andRHAmixtureswith plastic waste fibres to improve the tensile strength. The fibre content varied from 0.2% to0.4% by dry weight of soil, and the fibre length was 20mm. Three sizes of cylindrical specimensviz. 50mm diameter by 100mm height, 70mm diameter by 140mm height and 150mm diameterby 300mm height were tested. The lime used for stabilisation was estimated to be 12% of thedry soil mass and the ratio of the lime to RHA was 1:1. Inclusion of 0.2% and 0.4% plastic wastefibres was able to improve the tensile strength behaviour of the stabilised soil. Higher fibre contentresulted in a higher tensile strength and toughness index of the stabilised soil. Yadu, Singh, andTripathi (2011) investigated the potential of RHA to stabilise black cotton (BC) soil. Soil wasstabilised using different amounts of RHA, as 3, 6, 9, 11, 13 and 15%. The performance of RHAmodified soils were evaluated using different performance tests namely, CBR andUCS. It has beenreported that admixing of 9% RHA improves unsoaked CBR value upto 24%. Further increase ofRHA dosage beyond 24% resulted in the lowering of the CBR value. There was approximately77% increase in UCS at 9% RHA as compared to BC soil. Based on these performance tests, ithas been found that admixing of 9% RHA improves remarkably the strength of BC soil Dimter,Rukavina, and Drag (2011) investigated the effect of fly ash in the cement-stabilised pavementbase course materials. They observed that the amount of fly ash strongly influences the strengthof the stabilised mixes. Increasing the amount of fly ash in the binder leads to a decrease in thecompressive and indirect tensile strengths. El-Aziz and Abo-Hashema (2013) used limeHomrastabiliser to stabilise clayey soil. They found that 5% lime with 15% Homra (L + H : 5+ 15%)gives improvement similar to lime alone (11% lime). This is a valuable conclusion to reduceusing of lime by increasing the per cent of Homra as waste materials. Behak and Nunez (2013)used RHA as a soil stabiliser with lime. Temperature of burning on the reactivity of RHA andmixtureswith sandy soil and limewas investigated. It was found that themaximumUCSvalue andsplitting tensile strength value corresponds to the 20% RHA with 10% lime mixture at 28 and 56

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  • Road Materials and Pavement Design 541

    days. Sandy soils with RHA and lime ide an alternative material for the sub-base and base layersof low-volume traffic pavements. Camargo, Edil, and Benson (2013) used Class C fly ash forstabilisation of recycled pavement material (RPM) and a road surface gravel (RSG). They foundthat the UCS of RPM and RSG stabilised with fly ash increased with increasing fly ash contentand curing time and plastic strains for RPM and RSG with fly ash were smaller than the plasticstrains of the recycled materials alone. Noor, Aziz, and Suhadi (1993), Mantohar and Hantoro(1999), Chandra, Kumar, and Anand (2005), Alhassan (2008), Brooks (2009), Choobbasti et al.(2010), Seco, Ramirez, Miqueleiz, and Garcia (2011) and Olawale and Oyawale (2012), haveanalysed the suitability of RHA in highway sectors and the usefulness of the same with soil hasbeen recommended for the construction of subgrade or sub-base.In order to better understand the behaviour of expansive soils admixed with RHA, a series of

    experiments was carried out using clayey soil for different percentages of RHA. Shrinkage limitand compaction behaviourwere studied. Shear strength and deviator stress were determined for allthe samples with or without RHA ranging from 5% to 35% by weight of soil. This article mainlydeals with the effect of RHA addition in clayey soil on compaction; shear strength, CBR valueand shrinkage characteristics to assess the usefulness of RHA for modifying the soil structure, toimprove the load bearing capacity.

    3. Materials3.1. SoilClay of medium compressibility (A-7-6) soil is used for this study. The index properties such asthe liquid limit, plastic limit, plasticity index and other important soil properties as per AmericanAssociation of State Highway and Transportation Officials (AASHTO) and the soil classificationsystem used in the USA are presented in Table 1. Figure 1 presents the grain size distributioncurves of the soil.

    3.2. Rice husk ashRHA is a predominantly siliceous material obtained after burning of rice husk in a boiler or openfire. The lime reactivity test was conducted as per IS: 1727-1967, which indicated that the fullyburned RHA exhibits greater reactivity. This waste material having pozzolanic properties can beutilised in the stabilisation process for road construction. For this study, RHA was obtained frompaddy mill, Roorkee. It was fine grained siliceous in nature light weight and grey in colour. Thechemical composition was determined by X-ray fluorescence analysis. The physical and chemicalproperties are presented in Table 2. Figure 2 presents the grain size distribution curves of the RHA.

    Table 1. Physical properties of soil.

    Properties Values

    OMC (%) 17Maximum dry density (g/cm3) 1.68Specific gravity 2.74Liquid limit (%) 46Plastic limit (%) 21Plasticity index 25Unified soil classification CLAASHTO soil classification A-7-6Type of soil Clay of medium compressibility

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    0102030405060708090

    100

    0.001 0.01 0.1 1 10

    Per

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    Partical size (mm)

    Figure 1. Grain size distribution of soil.

    Table 2. Properties of rice husk ash.

    Physical properties Chemical properties

    Property Value Constituents % by weight

    Type Class F or low lime fly ash (FA) Ignition loss 8.2Specific gravity 2.17 SiO2 72.2Liquid limit 78 Al2O3 5.4Plastic limit Non-plastic Fe2O3 2.1OMC (%) 75 CaO 4.1MDD (g/cm3) 1.57 MgO 1.7Lime Reactivity (kg/cm2) 34

    0102030405060708090

    100

    0.1 1 10 100 1000

    Per

    cent

    age

    fine

    r (%

    )

    Partical size (m)

    Figure 2. Grain size distribution of RHA.

    4. Laboratory investigation and interpretation of results4.1. Shrinkage limit (wS)The opposite effect of shrinking is swelling soil. A volume change soil swells with increasingmoisture content, but it will shrink with decreasing moisture content. Soil shrinkage can causeserious distress to a foundation/structure. The mechanism is the same as the expansive, but inthe opposite direction. When wetter than the wS, the soil is fully saturated, but when drier, thesoil becomes unsaturated. The soil changes to a lighter colour at the wS due to the water recedingwithin the pores. In fact, the volume continues to decrease on drying beyond the wS. As soil is

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  • Road Materials and Pavement Design 543

    dried below the plastic limit it shrinks and becomes brittle until all the particles are in contact andthe soil can shrink no further. This point is called the shrinkage limit. The soil still has moisturewithin it but if any of this moisture is lost by further drying, air has to enter the soil to replace it.This test was conducted as per IS 2720 (Part 6). The variation of wS of soil with the addition ofdif...

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