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Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
Stabilization of weak pavement subgrades using cement kiln dust 2
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Stabilization of weak pavement subgrades using cement kiln dust 2

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  • 1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print), INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME TECHNOLOGY (IJCIET)ISSN 0976 – 6308 (Print)ISSN 0976 – 6316(Online)Volume 4, Issue 1, January- February (2013), pp. 26-37 IJCIET© IAEME: www.iaeme.com/ijciet.aspJournal Impact Factor (2012): 3.1861 (Calculated by GISI)www.jifactor.com © IAEME STABILIZATION OF WEAK PAVEMENT SUBGRADES USING CEMENT KILN DUST Brijesh Kumar1, Nitish Puri2 1 Assistant Professor, Department of Civil Engineering, HCTM Technical Campus Kaithal brijesh.k.thakur@gmail.com 2 Assistant Professor, Department of Civil Engineering, GCET, Greater Noida nitishpuri.ce.89@gmail.com ABSTRACT Clays are notoriously well known for giving rise to swelling problems and difficulties in construction due to excessive settlement and limited strength. Hence, such types of soils need to be stabilized before construction for improving their engineering properties. In soil stabilization, cement is commonly used as a stabilizing agent, to simultaneously increase the strength and stiffness of the originally weak, soft material. However cement is relatively expensive and potentially harmful to the environment when admixed with soils. The need for alternative stabilizing agents which could reduce the use of cement is therefore apparent. The objective of the present study is to investigate shear strength characteristics as well as mechanical strength of Kaolinite clay soil treated with 5, 10, 15, 20 and 25 % by weight of cement kiln dust. This has been done to make the soil suitable to build pavements over it. Standard Proctor tests have been conducted to determine optimum moisture content and maximum dry density of Kaolinite clay and Kaolinite clay stabilized with 5, 10, 15, 20 and 25 % of CKD passing 425 micron IS sieve. It has been observed that with increase in the percentage of cement kiln dust, OMC decreases and MDD increases. The decrease in OMC with increase in cement kiln dust content may be attributed to the addition of material which is classified as silty sand to the parent material. The presence of cement kiln dust having higher specific gravity may be the cause for increase in density. A series of unconfined compressive strength tests have been conducted to determine the strength characteristics of Kaolinite clay treated with various percentages of cement kiln dust. It has been observed that up to 20 % mixing of admixture, unconfined compressive strength (qu) and undrained shear strength (cu) increase significantly then decrease with further increase in percentage of stabilizer. It may be attributed to the addition of non-plastic silty material having free lime content. However, when the same samples were tested for mechanical strength by performing CBR tests, it has been observed that the CBR values increases with increase in percentage of CKD. It may also be attributed to the addition of non-plastic silty material having free lime content. Overall, it has been observed that the cement kiln dust effectively increases strength and hence make clays suitable for building pavements over it. 26
  • 2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEKeywords: Stabilization, Cement kiln dust (CKD), Maximum dry density (MDD), Optimummoisture content (OMC), Stabilization, Unconfined compressive strength (qu) and Undrainedshear strength (Cu).1. INTRODUCTION Weak foundation soil conditions can result in inadequate support and reduce structurallife. Soil properties can be improved through the addition of chemical or cementatious additivesi.e stabilization [1]. Soil stabilization refers to the procedure in which a soil, a cementingmaterial, or other chemical material is added to a parent soil to improve one or more of itsproperties. One may achieve stabilization by mechanically mixing the natural soil and stabilizingmaterial together so as to achieve a homogenous mixture or by adding stabilizing material to anundisturbed soil deposit and obtaining interaction by letting it permeate through soil voids. Thesechemical additives range from waste products to manufactured material which includes Portlandcement, Fly ash, chemical stabilizers and cement kiln dust. These additives can be used withvariety of soils to improve their native engineering properties. The effectiveness of theseadditives depends on the soil treated and the amount of additive used. The high strength obtainedfrom cement and lime may not always be required, however, and there is justification for seekingcheaper additives which may be used to alter soil properties.Invariably, any one of two methods is used to accomplish soil stabilization – mechanical andadditive. The effectiveness of a stabilization process can be gauged by the uniformity in blendingthe many materials. Usually, the preferred way of mixing is in a stationary or traveling plant.However other methods like scarifies, plows, disks, graders, and rotary mixers, are also largelypracticed. The method of soil stabilization is decided by the amount of stabilization required andthe prevailing conditions. Care must be taken to ensure that an accurate soil description andclassification is procured in order to select the correct materials and procedures. MechanicalStabilization is done by mixing soils of two or more gradations to result in a material of therequired specifics. This mixing of the soil can take place at the construction site, at a centralplant, or at a borrow area. The blended material is then spread and compacted to requireddensities. In additive method, an additive is any manufactured or commercial product that can beused to improve the quality of the soil, when added in accurate quantities. Portland cement, lime,lime-cement-fly ash and bitumen, alone or in combination, are commonly used additives tostabilize soils. The selection and quantity of additive used depends entirely on the type of soil andthe degree of improvement required.In this study, cement kiln dust (CKD) was used as an additive to improve the texture, compactionproperties and strength of kaolinite clay. Current study is based on the fact that when theadditives containing free calcium hydroxide are mixed with the soil, the calcium causes the clayparticles to flocculate into a more sand like structure reducing the plasticity of soil. Soilstabilization includes the effects of modification with a significant additional strength gain. Sincethe soil stabilization mechanism of fine grained soil requires calcium (in the form of lime) as themajor stabilizing agent, hence we can use CKD which contains high free lime for stabilization ofclay soil.2. NEED FOR PRESENT STUDY The shear strength is, without doubt, the most important engineering property of soil.Also bearing capacity criteria or shear strength failure criteria must be satisfied for satisfactoryperformance of foundations. Hence the most important design input parameter needed forgeotechnical design is soil’s shear strength [6]. 27
  • 3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEThere are three different type of failure mechanism, based on the pattern of shearing zones, havebeen identified as general shear failure, local shear failure and punching shear failure. In clays,punching shear failure is of great importance. It occurs in soils possessing the stress-straincharacteristics of a very plastic soil.Typical features of this mode are: a) Poorly defined shear planes b) Soil zones beyond the loaded area being little affected. c) Significant penetration of a wedge shaped soil zone beneath the foundation, accompanied by vertical shear beneath the edges of the foundation. d) Ultimate load cannot be clearly recognized.Hence proper investigations regarding strength of soil must be done to ensure long serviceabilityof pavements. The present work aims to understand the strength characteristics of kaolinitetreated with cement kiln dust. The globally growing demand of cement results in toweringcollection of CKD from cement plants. The disposal of this fine dust is very difficult and poses aserious environmental threat [7]. Our study also focuses on the reduction of the huge stock pilesof this material. A better understanding of these properties will enhance the usage of this materialin geotechnical engineering and highway engineering works.3. MATERIALS USED3.1 Kaolinite clay Clay mineral used in the experiments was collected from Starke & Co. Pvt. Ltd., 17Najafgarh Road, Near Zakhira Chowk, New Delhi-110015. It was classified as CI (clay ofintermediate compressibility) as per specifications of IS: 1498 (1970) [2]. The chemical andphysical properties are reported in Table 1 and Table 2 respectively. Table 1. Chemical properties of kaolinite clay Percentage By Weight Constituents (%) Al2O3 30.3 Fe2O3 1.5 TiO2 1.0 SiO2 56.2 CaO 0.56 MgO 0.90 Na2O + K2O 1.0 LOI 8.53.2 Cement kiln dust It was collected from Jaypee cement plant, Solan, Himachal Pradesh. It was classified asSM as per specifications of IS: 1498 (1970) [2]. The physical properties are reported in Table 1. 28
  • 4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Table 2. Physical properties of materials Materials Index Properties Kaolinite Clay Cement Kiln Dust IS Classification CI SM Specific Gravity 2.36 2.52 Liquid Limit 45 Plastic Limit 22 NP Plasticity Index 23 OMC 18% - MDD 1.69 g/cc - CBR (Unsoaked) 5.88 - CBR (Soaked) 2.36 -4. SAMPLE PREPARATION The whole process of sample preparation is divided into three parts, 1)Composition of samples, 2) Mechanical Mixing and 3) Static compaction.4.1 Composition of specimens Specimens of Kaolinite clay and Kaolinite clay treated with 5, 10, 15, 20 and25 % of cement kiln dust passing 425 micron IS sieve were prepared at maximum drydensity and optimum moisture content as per specifications of IS: 2720 (Part 7) (1974)[3].4.2 Mechanical mixing Oven dry soil was dry mixed with various percentages of oven dried cementkiln dust (CKD). Sufficient quantity of water was then added to bring the moisturecontent to the desired level. The mixture was then manually mixed thoroughly with aspatula.4.3 Static compaction Cylindrical specimens were compacted by static compaction in 3.9 cmdiameter split mould to the required height of 8.5 cm. The inner surface of the splitmould was smeared with oil to reduce friction during the extraction of sample. Thewet homogenous mixture was placed inside the split mould using spoon withcontinuous tapping with spatula and leveled. The whole assembly was staticallycompacted in loading frame to the desired density.The sample was kept under static load for not less than 20 minutes in order to accountfor any subsequent increase in height of sample due to swelling. All the specimenswere kept in polythene bags for maturing for three days. 29
  • 5. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Fig. 1 Samples kept for maturing5. ANALYSIS OF TEST RESULTS & DISCUSSION The objective of the present study is to investigate strength characteristics ofKaolinite clay soil treated with 5, 10, 15, 20 and 25 % by weight of cement kiln dust.This has been done to make the soil suitable to build pavements over it. In order toassess improvement in strength, unconfined compressive strength (qu), failure loadand undrained shear strength (cu) have been evaluated [8]. The results of these testshave been analyzed under the following headings:5.1 Moisture-density relationship Standard Proctor tests have been conducted to determine optimum moisturecontent (OMC) and maximum dry density (MDD) of Kaolinite clay stabilized withvarious percentages of cement kiln dust as per specifications of IS: 2720 (Part 7)(1974) [3] and the results are tabulated in Table 3. For Kaolinite clay OMC and MDDhave been observed as 18 % and 1.69 g/cc respectively. For Kaolinite clay stabilizedwith Cement kiln dust OMC varies from 19 to 16.5 % and MDD varies from 1.682 to1.736 g/cc. It has been observed that with increase in the percentage of cement kilndust OMC decrease and MDD increases upto 20 % CKD content as an additive. Butbeyond that, the value of MDD decreases and value of OMC increases. The decreasein OMC with increase in cement kiln dust content upto 20 % may be attributed to theaddition of material which is classified as silty sand to the parent material. Thepresence of cement kiln dust having higher specific gravity may be the cause forincrease in density. 30
  • 6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Table3. Compaction characteristics of Kaolinite clay treated with various percentages of cement kiln dust MDD OMC Description Of Sample (g/cc) (%) Kaolinite + 5% CKD 1.682 19 Kaolinite + 10% CKD 1.692 18.7 Kaolinite + 15% CKD 1.745 18.5 Kaolinite + 20% CKD 1.768 15 Kaolinite + 25% CKD 1.736 16.5Fig 2 to Fig 7 shows comparison of MDD and OMC for clay stabilized with variouspercentages of cement kiln dust. 1.7 Dry Density in g/cc 1.65 1.6 1.55 1.5 0 10 20 30 Moisture Content (%) Fig 2. Moisture content vs Dry densitycurve for Kaolinite clay 1.7 Dry Density in g/cc 1.65 1.6 1.55 1.5 0 10 20 30 Moisture Content (%) Fig 3. Moisture content vs Dry density curve for Kaolinite clay + 5% CKD 31
  • 7. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME 1.75 Dry Density in g/cc 1.7 1.65 1.6 1.55 0 10 20 30 Moisture Content (%) Fig 4. Moisture content vs Dry density curve for Kaolinite clay + 10% CKD 1.8 Dry Density in 1.7 1.6 g/cc 1.5 1.4 0 20 40 Moisture Content (%) Fig 5. Moisture content vs Dry density curve for Kaolinite clay + 15% CKD 1.8 Dry Density in g/cc 1.75 1.7 1.65 1.6 1.55 0 10 20 30 Moisture Content (%) Fig 6. Moisture content vs Dry density curve for Kaolinite clay +20 % CKD 1.75 Dry Density in g/cc 1.7 1.65 1.6 1.55 0 10 20 30 Moisture Content (%) Fig 7. Moisture content vs Dry density curve for Kaolinite clay +25 % CKD 32
  • 8. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME5.2 California bearing ratio California bearing ratio (CBR) tests were conducted to determine mechanicalstrength of kaolinite clay treated with cement kiln dust in soaked as well as unsoakedcondition as per specifications of IS: 2720 (Part 16) (1987)[5]. It has been observed thatvalue of CBR in both conditions increases with increase in CKD content as additive. Inunsoaked condition CBR varies from 6.78 to 9.21 and in soaked condition it varies from2.84 to 3.147. CKD Values for all samples are reported in Table 4 and represented inFigure 8. Table 4. CBR values of kaolinite samples stabilized with CKD CBR CBR Description Of Sample (Unsoaked) (Soaked) Kaolinite + 5% CKD 6.78 2.84 Kaolinite + 10% CKD 7.67 2.94 Kaolinite + 15% CKD 7.81 2.96 Kaolinite + 20% CKD 8.95 3.047 Kaolinite + 25% CKD 9.21 3.147 10 9 8 CBR 7 (Unsoaked) CBR values 6 5 4 3 CBR 2 (Soaked) 1 0 0 10 20 30 Percentage of CKD content (%) Fig. 8 Variation of CBR values with percentage of CKD content 33
  • 9. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME5.3 Strength Characteristics A series of unconfined compressive strength tests were conducted to determine thestrength characteristics of Kaolinite clay treated with various percentages of cement kilndust as per specifications of IS: 2720 (Part 10) (1973) [4] and the results are tabulated inTable 5. It has been observed that unconfined compressive strength (qu) and undrainedshear strength (cu) increase with increase in percentage of CKD upto 20 %. Furtherincrease in percentage of CKD as stabilizer leads to decreased values of qu and cu. Thiscan be attributed to the addition of non-plastic silty material having free lime content.Fig.9 shows comparison of cu for Kaolinite clay stabilized with various percentages ofcement kiln dust. Table 5. Strength characteristics of Kaolinite clay treated with various percentages of cement kiln dust UCS Undrained Shear Failure Load Description Of Sample qu Strength Cu (kg) (kg/cm2) (kg/cm2) Kaolinite 23.85 1.691 0.845 Kaolinite + 5% CKD 74.1 5.254 2.627 Kaolinite + 10% CKD 74.7 5.517 2.758 Kaolinite + 15% CKD 75.3 5.636 2.818 Kaolinite + 20% CKD 77.26 5.782 2.891 Kaolinite + 25% CKD 78 5.684 2.842 3.5 3 Undrained shear stregnth 2.5 2 1.5 1 0.5 0 Percentage of CKD asstabilizer (%) Fig. 9 Undrained shear strength Vs. Percentage of CKD as stabilizer 34
  • 10. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEThe failure patterns of kaolinite clay samples treated with various percentage of CKDcontent are shown in Fig. 10 to 15. Fig. 10 Failure pattern of axially loaded sample of Kaolinite Fig. 11 Failure pattern of axially loaded sample of Kaolinite + 5% CKD Fig. 12 Failure pattern of axially loaded sample of Kaolinite + 10% CKD Fig. 14 Failure pattern of axially loaded sample of Kaolinite + 15% CKD 35
  • 11. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEME Fig. 13 Failure pattern of axially loaded sample of Kaolinite +20 % CKD Fig. 15 Failure pattern of axially loaded sample of Kaolinite + 25% CKD6. CONCLUSIONS The study demonstrates the influence of cement kiln dust on the strengthcharacteristics of Kaolinite clay. The following conclusions have been drawn based on thelaboratory investigations carried out in this study: 1. It has been observed that with increase in the percentage of cement kiln dust OMC decrease and MDD increases. The decrease in OMC with increase in cement kiln dust content may be attributed to the addition of material which is classified as silty sand to the parent material. The presence of cement kiln dust having higher specific gravity may be the cause for increase in density. 2. Strength analysis of the kaolinite clay and Kaolinite clay stabilized with various percentages of cement kiln dust indicates that up to 20 % mixing of admixture qu and cu increases then decreases. It can be attributed to the addition of non-plastic silty material having free lime content. However, it has been observed that mechanical strength evaluated from CBR test increases with increase in CKD content.The study shows that treatment of soil with cement kiln dust is an effective method ofstabilization of problematic soils.To summarize, use of this industrial wastes is a beneficial proposition which is economicaland environment friendly as well. Results of this study can be used in construction ofpavements over CKD stabilized clay beds. 36
  • 12. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),ISSN 0976 – 6316(Online) Volume 4, Issue 1, January- February (2013), © IAEMEREFERENCES [1] Ho Meei-Hoan, Tarmizi Ahmad, Chan Chee-Ming and Bakar Ismail (2011), “Leachability and Strength of kaolin Stabilized With Cement and Rubber”, International Journal of Sustainable Construction Engineering & Technology, Vol.2, Issue1. [2] IS: 1498 (1970),”Indian Standard Methods of Test for Soils: Classification and Identification of Soil for General Engineering Purposes”, Bureau of Indian Standards. [3] IS: 2720 (Part 7) (1974), “Indian Standard Methods of Test for Soils: Determination of Moisture Content-Dry Density Relation using Light Compaction”, Bureau of Indian Standards. [4] IS: 2720 (Part 10) (1973), “Determination of Unconfined Compressive Strength”, Bureau of Indian Standards. [5] IS: 2720 (Part 16) (1987), “Indian Standard Methods of Test for Soils: Laboratory determination of CBR”, Bureau of Indian Standards. [6] Ranjan, Gopal and Rao, A.S.R. (2000), “Basic and Applied Soil Mechanics”, New Age International (P) Ltd., New Delhi. [7] Robert L. Parsons, Elizabeth Knee Bone, Justin P. Milburn (2004), “Use o Cement Kiln Dust For Sub-Grade Stabilization”. [8] Singh, Alam and Chowdhary, G.R. (1994), “Soil Engineering in Theory and Practice”, Geotechnical Testing and Instrumentation, Vol. 2, CBS Publishers and Distributors, Delhi. 37

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