Transcription
Proceedings of the 4th International Conference on Civil Engineering for Sustainable Development(ICCESD 2018), 9 11 February 2018, KUET, Khulna, Bangladesh (ISBN-978-984-34-3502-6)STABILIZATION OF SOIL BY MIXING WITH DIFFERENT PERCENTAGES OFLIMEM A Ashraf1, M A Hossen2, M A Ali3 and B P Chakaraborty 31Professor,2Southern University Bangladesh, Bangladesh, e-mail: [email protected], Southern University Bangladesh, Bangladesh, e-mail: [email protected] Students, Southern University Bangladesh, Bangladesh, e-mail: [email protected] urbanization in our cities has created a tremendous demand for developable landespecially in the periphery of our cities and towns. We have found several researches dealing withsoil-cement and soil-lime stabilization but none has dealt with the specific type of soils which arefound in and around the city of Chittagong. We have found from the past researches that cementperforms better with sandy soil while lime performs better with silty/clayey soil. In this research, wehave tried to check the performance of lime with two different types of soils: hilly soil from Khulshiarea and paddy land soil from South Salimpur within the city. Lime-stones were procured from localmarket. For the ease of measurement and for easy and uniform spreading over soil before mixing, itwas converted into powder by sprinkling water on it. It was found that the lime stone procured fromthe local market had a lime content of 63.2%. Lime-powder in variable percentages of 0%, 2%, 4%,6%, 8%, 10%, 12%, and 14% were used as stabilizer. The compressive strengths of lime stabilizedsoil were evaluated for different curing period: 7 days, 14 days, 28 days and 60 days. It was foundthat the load bearing capacity of soil increased with the increase in percentage of lime to a certainlimit. It was, also, found that strength increases with the increase in curing period. At 8% lime content,maximum compressive strength were found in paddy land soil while at 6% lime content maximumcompressive strength were found in hilly soil. Hilly soils are generally sandy while the paddy land soilsare silty / clayey. It was found that less limes were necessary for stabilizing sandy hilly soil comparedto silty paddy land soil. Since lime is cheaper compared to cement, it may become a viable alternativeof cement for soil stabilization. Before arriving at a definite conclusion on the use of lime stabilizedsoil, further researches with lime using all different varieties of soils in and around the City ofChittagong will be necessary.Keywords: Quick Lime, hydrated lime; curing period; soil compressive strength, soil-lime stabilization1. INTRODUCTION1.1Background InformationIn the last few decades, world population has increased rapidly especially in developingcountries like Bangladesh. Buildings are being built and roads are constructed byencroaching into paddy land. Hills in Chittagong are continuously being lebelled to buildhouses on it. We like it or not buildings are built on paddy land and the hills. Since paddyland soils are mostly silt with some clay and the hill soils are generally loose fine sand with asmall percentage of silt and clay, engineers often had to go for costly foundation like deepfoundation in these type of soils. Construction is risky in these soils due to unevensettlement, land slides and or shear failure. Deep foundations are, sometimes, beyond thefinancial capacity of average home builders trying to build a three or four story building to beclaimed and taken pride of as their own house.Therefore, a suitable and low cost alternative to deep foundation is to be identified for theaverage home owners going for a low rise building. Soil stabilization techniques mightbecome the cheap alternatives against the conventional technique of deep foundation usingpre cast or cast in situ piles. Improvements in engineering properties of soil such asincreases in soil strength (shear resistance), stiffness (resistance to deformation) andICCESD-2018-4683-1
4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)durability (wear resistance), reduction in swelling potential of wet clay soils can be done bysoil stabilization(Sultan et al. 2014).Soil stabilization involves the blending of natural soils with chemical agents such as lime,cement (OPC or PPC) and asphalt (Rogers et al.). These agents are generally potentialbinders which effectively bind together the soil aggregates. As a result, load carrying andstress distribution characteristics of soil improve; excessive shrinkage and swelling in soilcome under control. A very common and cheap technique to improve the soft clay soil is toadd a certain percentage of lime with the soil (Farooq et al. 2011). Lime in the form ofquicklime (calcium oxide – CaO), hydrated lime (calcium hydroxide – Ca[OH]2), or limeslurry can be used to treat the soils. Hydrated lime is created when the quicklime chemicallyreacts with water. It is hydrated lime that reacts with particles of clay and permanentlytransform them into a strong cementious matrix (Ajayi 2012) .1.2 Chemistry of Lime TreatmentThe chemical reactions between clay and lime particles can be grouped under two distincttypes of changes; one is a short term change termed as modification and the other is a longterm change termed as stabilization. In modification, the process of ion exchange makes theclay minerals flocculate and agglomerate leading to a reduction in plasticity, swell andmoisture content. In stabilization, pozzolanic reaction takes place over a long period of timethat creates cementitious products which are responsible for long-term gain in strength(Bozbey et al. 2016).1.3Drying:If quicklime is used, it immediately hydrates (i.e., chemically combines with water) andreleases heat. As a result, soil dries quickly, because part of the water present in the soilparticipates in the reaction, and the rest evaporates due to heat of hydration. The hydratedlime produced thus will subsequently react with clay particles. These subsequent reactionswill slowly cause additional drying because of a reduction in soil’s moisture holding capacityby way of modification in soil structure known as floculation. Floculation increases drainagecapability of the soil and reduces the soil’s moisture holding capacity. If hydrated lime orhydrated lime slurry is used instead of quicklime, drying occurs only through changes in thesoil structure. This, in fact, increases the draining capability of of the soil; reduces the waterholding capacity of the soil and increases its stability. In fig.1, it can be seen that watercontent Wn is reduced to W’n after treatment with lime.1.4Modification:After initial mixing, the calcium ions (Ca ) from hydrated lime migrate to the surface of theclay particles and displace water and other ions. The soil becomes friable and granular,making it easier to work and compact. At this stage the Plasticity Index of the soil as shownin Figure 1 decreases dramatically, as does its tendency to swell and shrink. The process,which is called “flocculation and agglomeration," generally occurs in a matter of hours.(Kerni, Sonthwal, and Jan 2015)Figure 1: Effect of lime addition on the consistency of soilICCESD-2018-4683-2
4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)1.5Stabilization:When adequate quantities of lime and water are added, the pH of the soil quickly increasesto above 10.5, which enables the clay particles to break down. Silica and alumina arereleased and react with calcium from the lime to form calcium-silicate-hydrates (CSH) andcalcium-aluminate-hydrates(CAH). Both CSA and CAH are cementitious products similar tothose formed in Portland cement. They form the matrix that contributes to the strength oflime-stabilized soil layers. As this matrix forms, the soil is transformed from a sandy, granularmaterial to a hard, relatively impermeable layer with significant load bearing capacity. Theprocess begins within hours of lime addition and can continue for years in a properlydesigned system. The matrix formed is permanent, durable, and significantly impermeable,producing a structural layer that is both strong and flexible.Therefore the purposes of binder addition to soft clays can be stated briefly (Bozbey et al.2016) as: To increase the strength and stiffness of soft soil To improve the differential deformation properties of the soft soil To increase dynamic stiffness of the soft soil To remediate contaminated soilThe aim of this study is to determine the engineering properties and unconfined compressivestrength of paddy land soil and hill soil. Additionally, this study investigates the improvementof the unconfined compressive strength of soil by mixing different percentages of lime withsoil. Finally, it gives information about optimum lime content for this particular types of soilfor improving the unconfined compressive strength of the soil . Four different time periods forcuring were considered.2. LITERATURE REVIEWSoil stabilization is a procedure where natural or synthesized additives are used to improvethe engineering properties of weak soil. Several reinforcing methods are available forstabilizing soils. Therefore, the techniques of soil stabilization can be classified into anumber of categories such as physical stabilization, chemical stabilization and mechanicalstabilization. There is a rich history of the use of soil stabilization admixtures to improve poorsub grade soil. Improvement in performance by controlling volume change and byincreasing strength was in practice (Navale et al. 2016).Tedesco (2006) studied soil compressibility before and after lime treatment with respect tothe effects of initial moisture content of compacted soil sample, the curing time and the testprocedure. He used a unique percentage of lime equal to 3% by weight of soil for all soilspecimens. Using standard and modified Proctor tests, the samples were prepared withmoisture content corresponding to optimum water content. In addition to the odometer, hedeveloped a delayed procedure, which involved tests with constant curing time of 7 and 28days. He pointed out that the lime-treated soil samples exhibited lower compressibility;particularly for samples compacted on the dry side and that dramatic over consolidation wasobtained by dynamic compaction.4% addition of lime with Gazipur clay soil increased the unconfined compressive strength atdifferent curing period by four to six times. Strengths with 4% lime were, also, found to be1.5 to 2 times higher compared to the addition of lime in the range of 2, 6 and 8%.(Farooq etal. 2011). Better strength was recorded when Gazipur soil was combined with 4% limeBy adding 6% lime with sandy clay maximum strength found was 198.44 KPa for 6%addition of lime (Jawad et al. 2014).ICCESD-2018-4683-3
4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)It is evident from literature review that lime stabilization is one of the most practical and costeffective techniques of sub grade stabilization. However, it is to be noted that in coldweather, lime stabilization could not give the desired strength in soil. The goal of thisresearch is to clearly understand the behavior of lime in increasing compressive strength oflocally available soil.3. METHODS & PROCEDURESThe soils used in this study were classified according to Unified Soil Classification System(USCS). For the classification Atterberg limit test, Sieve Analysis test as well as HydrometerAnalysis test was conducted. The consistency limit test includes liquid limit and plastic limittests of soil by using the Casagrande apparatus in accordance with ASTM specification. TheASTM standard procedure was followed in performing particle-size analysis of fine grainedsoil which was based on the principle of sedimentation of particles, and is measured byflotation of hydrometer for 36 hours. The results associated with the classification of both soilsamples were showed in the tabular format in Table 1.Table1: Classification and Engineering Properties of SoilSoil Properties (Paddy Land Soil)ParameterAs Per Unified Soil Classification System(USCS)SandGroup Symbol SMSilt & ClayLiquid LimitPlastic LimitPlasticity IndexOptimum Moisture Content(OMC)SalinitySoil Properties (Hilly Soil)As Per Unified Soil Classification System(USCS)Group Symbol SCLiquid LimitPlastic LimitPlasticity IndexOptimum Moisture Content(OMC)SalinitySandSilt & ClayPercentages (%)68324743.53.516Nil594130.52010.512NilLime in the form of Lime-stones (CaCo3), quicklime (calcium oxide – CaO), hydrated lime(calcium hydroxide – Ca (OH) , or lime slurry can be used to treat soils. Quicklime is2manufactured by chemically transforming calcium carbonate (limestone – CaCO3) intocalcium oxide. Hydrated lime is created when quicklime chemically reacts with water. In ourcase, lime-stones were collected from the local market. Properties of lime-stones procuredfrom the local market are given in Table-2.ICCESD-2018-4683-4
4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)Table 2: Properties of Lime-stones procured from local marketLime Properties.SL No.123(1 2)4ParameterPercentages (%)Calcium oxide –63.2CaOMoisture22.9CalciumHydroxide86.1Ca(OH) 2Residual13.9MaterialsIn this research, performance of lime with two different types of soils: hilly soil from Khulshiarea and paddy land soil from South Salimpur within the city were assessed. For the ease ofmeasurement, it was converted into powder by sprinkling water on it. It was found that thelime stone procured from the local market had a lime content of 63.2%(Table 2). Limepowder in variable percentages of 0%, 2%, 4%, 6%, 8%, 10%, 12%, and 14% were used asbinder/stabilizer. The unconfined compressive strengths of lime stabilized soil wereevaluated for different curing period: 7 days, 14 days, 28 days and 60 days. The overallworking framework is shown in Figure 2.Figure 2: Flowchart of Methods and ProceduresICCESD-2018-4683-5
4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)4. RESULTS AND DISCUSSIONSThe results of the unconfined compressive strength tests are given in this section.Unconfined compressive strengths were estimated from stress strain diagram and plottedagainst eight different percentages of lime content for four different curing periods and areshown in figure 3. It shows that unconfined compressive strength increases as the curingperiod increases for all the hilly soil samples tested in this study. It also shows thatunconfined compressive strength increases for (0% - 6%) lime content and decreases forfurther increment of lime content in the samples. The initial increment of unconfinedcompressive strength for using (0%-6%) percent of lime is due to the hydration of lime in thehilly soil sample and the later decrement of unconfined compressive strength for using (8 to14 %) percent of lime is due to the presence of excessive lime, having less compressivestrength compared to soil, in the hilly soil sample. It is clear from the Figure that 6% limecontent in the hilly soil gives highest unconfined compressive strength after each curingperiod. The compressive strength is highest after a curing period of sixty days. It is clear thatcompared to cement lime takes more time in curing for gaining adequate strength.Figure 3: Unconfined Compressive strength (UCS) of hilly Soil with different percentages oflime and different curing periodFigure 4 shows that unconfined compressive strength against four different curing periodsfor eight different percentages of lime soil mixture. It showed that that with 0% limes content,unconfined compressive strength is almost similar for all four curing periods. That meanswhen no lime is used, increase in curing period will have no appreciable effect on thestrength of soil. However, for varying percentages of lime in lime soil mixture, considerablevariations of unconfined compressive strengths were observed. The optimum lime contentrequired to produce maximum strength depends on curing temperature and curing period.From the figure:4, it is also found that soil without lime gives the lowest unconfinedcompressive strength and addition of 6% lime content with hilly soil showed largest values ofunconfined compressive strength for all curing periods.ICCESD-2018-4683-6
unconfined compressive sttrength(psi)4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)9080700% Lime2% Lime4% Lime6% Lime8% Lime10% Lime12% Lime14 % Lime60504030201007142860curing time (days)Figure 4: Unconfined compressive strength of Hilly soil as a function of curing period foreight different lime soil mixturesstrength (psi)In figure 5 it is shown that unconfined compressive strength increases with the increase inthe length of curing period, even when the percentage of lime remained unchanged. It alsoshowed that with further increase in lime, in all curing periods, strength decreases.908070605040302010083.877 DaysStrength14 daysStrength28DaysStrength60 DaysStrength78.8055.9440.250%2%4%6%8%10%12%14%16%% limeFigure 5: Unconfined compressive strength of hilly soil against percentages of lime for 7, 14,28, 60 days of curing period.Unconfined compressive strength was estimated from stress strain diagram and plottedagainst eight different percentages of lime content for four different curing periods. In figure6, it shows that unconfined compressive strength increases as the curing period increasesfor all the paddy land soil samples tested in this study. It also shows that unconfinedcompressive strength increases for (0% - 8%) lime content and decreases for furtherincrement of lime in the samples. The initial increment of unconfined compressive strengthfor using (0%-8%) percent of lime is due to the hydration of lime in the paddy land soilsample and the later decrement of unconfined compressive strength for using (10 to 14 %)percent of lime due to the presence of excess lime (having less compressive strengthcompared to soil) in the paddy land soil sample. It is clear from the Figure that 8% limecontent in the paddy land soil gives highest unconfined compressive strength at each curingperiod used in this study.ICCESD-2018-4683-7
Compressive strength(psi)4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)1.00.90.80.70.60.50.40.30.20.10.0000000007 day0000000014 day0000000028 day0000000060 Day00000000% of lime7 day14 day28 day60 DayFigure 6: Unconfined Compressive strength (UCS) of Paddy Land Soil with the differentpercentages of limeFigure 7 shows the plotting of unconfined compressive strength against four different curingperiods for eight different percentages of lime soil mixture. It shows that (0% lime content)unconfined compressive strength is almost similar for all four curing periods indicating noeffect of curing period on unconfined compressive strength for 100 percent sample soil.However, for other cases (lime soil mixture) considerable variation of unconfinedcompressive strength was observed with varying percentage of lime content in soil indicatingthe effect of lime content on unconfined compressive strength. From the Figure 7, it is alsofound that soil without lime gives the lowest unconfined compressive strength and 8% limecontent in paddy land soil gave largest values of unconfined compressive strength for allcuring periods. Therefore, adding only 8% of lime with paddy soil gives considerableimprovement in the strength of soil.Unconfined compressivesttrength (psi)70.0060.000% Lime50.002% Lime40.004% Lime30.006% Lime20.008% Lime10% Lime10.0012% Lime0.00714286014 % Limecuring time (days)Figure 7: Unconfined compressive strength of Paddy Land Soil as a function of curing periodfor eight different lime soil mixturesICCESD-2018-4683-8
4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)In figure 8 it is shown that the unconfined compressive strength increases in respect ofcuring period when the percentage of lime is constant. It also showed that with furtherincrease of lime in all curing period, strength decreases.Figure 8: Unconfined compressive strength of Paddy Land Soil against percentages of limecontent for 7, 14 and 28 days curing period.5. CONCLUSIONSIt was found that the soil strength increased with the increase in percentage of lime to acertain limit. It was, also, found that strength increases with the increase in curing period. At8% lime content, maximum compressive strength was found in paddy land soil while at 6 %lime content maximum compressive strength was found in hilly soil. Hilly soils are generallysandy while the paddy land soils are silty/clayey. It was found that less limes were necessaryfor stabilizing sandy hilly soil compared to silty paddy land soil.RECOMMENDATIONSThe following recommendations are suggested for further research work. Different varieties of soil sample, especially soils frequently found and used in thelocality, can be analyzed for same and similar percentages of lime used in this study. Impact of cyclic wetting–drying on swelling behavior of lime-stabilized soil is to beinvestigated.ACKNOWLEDGEMENTSSouthern University Bangladesh Civil Engineering Laboratory and its resources were usedduring this research work.The authors thank the laboratory technicians for their help duringthe investigations.ICCESD-2018-4683-9
4th International Conference on Civil Engineering for Sustainable Development (ICCESD 2018)REFERENCESAjayi, Emmanuel Sunday. 2012. “Int . J . Forest , Soil and Erosion , 2012 2 ( 4 ): 165-168 ISSN 22516387 [ PRINT ] 2251-824X [ Online ] November 2012 , GHB â TM S Journals , IJFSE ,Shabestar , Iran Effect of Lime Variation on the Moisture Content and Dry Density of Lateritic Soilin Ilorin , Nigeria . Received : 2012-01-29 Accepted : 2012-03-22 Shabestar , Iran 165.”2(November): 165–68.Bozbey, Ilknur et al. 2016. “Importance of Soil Pulverization Level in Lime Stabilized 091.Farooq, S M, M A Rouf, S M A Hoque, and S M A Ashad. 2011. “Effect of Lime and Curing Period onUnconfined Compressive Strength of Gazipur Soil , Bangladesh.” : 4–8.Jawad, Ibtehaj Taha, Mohd Raihan Taha, Zaid Hameed Majeed, and Tanveer A. Khan. 2014. “SoilStabilization Using Lime: Advantages, Disadvantages and Proposing a Potential Alternative.”Research Journal of Applied Sciences, Engineering and Technology 8(4): 510–20.Kerni, Vipul, Vinod Kumar Sonthwal, and Umar Jan. 2015. “Review on Stabilization of Clayey SoilUsing Fines Obtained From Demolished Concrete Structures.” International Journal of InnovativeResearch in Science, Engineering and Technology 4(5): 296–99.Navale, A V, B E Gite, M D Mundada, and S B Kolhe. 2016. “SOIL STABILISATION USING FLY-ASH& LIME.” (3): 4588–96.Rogers, C. and S. Glendinning, 1996. Modification of clay soils using lime. Proceeding of Seminar onLime Stabilization, pp: 99-114.Sultan, T et al. 2014. “Experimental Study of Silty Clay Stabilization With Cement and Lime in Multan ,Pakistan.” 19(Iii): 28–33.Tedesco, D.V., 2006. Hydro-mechanical behaviour of lime-stabilised soils. Ph.D. Thesis, University ofCassino. Cassino, Italy.ICCESD-2018-4683-10
Soil stabilization techniques might become the cheap alternatives against the conventional technique of deep foundation using pre cast or cast in situ piles. Improvements in engineering properties of soil such as increases in soil strength (she
