Soil stabilization means alteration of the soils properties to meet the .... Any type
of soil, except organic soil or highly plastic clays, may be stabilized with.
Utilization of Solid Waste for Soil Stabilization: A Review Prasad P. Dahale Research Scholar & Asst. Prof. Civil Engg. Deptt. PCE, Nagpur (India)
Dr. P.B. Nagarnaik Professor Civil Engg. Deptt. GHRCE, Nagpur (India)
Dr. A.R. Gajbhiye Professor and HOD Civil Engg. Deptt. Y.C.C.E., Nagpur (India)
ABSTRACT Soil stabilization means alteration of the soils properties to meet the specified engineering requirements. Methods for the stabilization are compaction and use of admixtures. Lime, Cement was commonly used as stabilizer for altering the properties of soils. From the recent studies it is observed that, solid waste materials such as flyash, rice husk ash are used for this intended purpose with or without lime or cement. Disposal of these waste materials is essential as these are causing hazardous effects on the environment. With the same intention literature review was undertaken on utilization of solid waste materials for the stabilization of soils and same is presented here.
KEYWORDS:
Solid waste materials, Flyash, Rice Husk Ash, Strength, Plasticity
Index
INTRODUCTION Solid waste term includes all those solid and semi-solid materials that are discarded by the community. Improper management of solid wastes causes adverse effects on the ecology which may lead to cause possible outbreak of diseases and epidemics. Solid wastes are broadly classified in to three group’s namely Industrial waste, Agricultural waste, and Municipal waste apart from other categories of wastes. Industrial wastes are the waste arising from industrial activities and are hazardous in nature due to presence of toxic substances. Flyash (FA) is an industrial waste being generated from thermal power plants and it is available in fine dust form. FA contain trace amount of toxic metals such as Cr, Th, Pb, Hg, Cd, etc. which may have negative impact on the health of humans, animals and plants growth too. Indian generates 160 million tons of flyash from different thermal power stations annually and about 65,000 acres of land are used as ash ponds, says 2006 Confederation - 2443 -
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of Indian Industries report on flyash. Thus huge amount of flyash generated, is not only causing environmental problem, but also creating problems associated with its disposal. At present there are four major power plants working in Vidharbha region of Maharashtra State (India) namely Koradi Thermal Power Plant, Chandrapur Thermal Power Plant, Khaparkheda Thermal Power Plant and Paras Power Station producing flyash around 74,98,017 MT/year (Year 2008-09) but only 21% of the generation is being utilized by different sectors such as cement, bricks manufacturing, land filling and in road constructions, etc. but still large quantum of flyash dumped near power station on open fields. Vidharbha region blessed with natural resources mainly coal and manganese, contributing nearly 5000 million tons / year of coal and about 40% of total manganese production in India. 63% of total electricity supply to the state contributed by Vidharbha region. Government has taken initiative to promote the infrastructure and industrial development in these underdeveloped region and sanctioned projects like special economic zones (SEZ), Multi Model International Cargo Hub and Airport at Nagpur (MIHAN) and to meet the demand of electricity for these proposed projects additional 43 new power plants are also sanctioned in the region. Some of the major plants in process are, Adani Power Tiroda, NTPC Mouda, Lenexis Energy Nagpur, Mahagenco Chandrapur, etc. Due to these upcoming power plants in the region, flyash production will increase to a great extent and existing problem of FA disposal will become serious. Rice is the primary source of food for billion peoples across the world. At present around 600 mt of paddy produced annually. India is second largest producer of rice next to china. In Vidharbha, Chandrapur, Bhandara, Gondia, Nagpur and Gadchiroli districts are known for rice production. Yearly production of rice is about 0.32 million tons resulting huge husk production. Rice husk is the shell produced during dehusking of paddy. Rice husk being agricultural waste dumped near the mills or burnt in open fields. Numerous problems arises from rice husk disposal such as, methane generation due to fermentation of RH with microorganisms, being light and fine particles causing breathing problems, bad effect on the health are reported such as acute and chronic effect affecting eyes, skin and upper respiratory tract and allegoric response such as nasal catarrh, asthma and limitation of RH because of low nutritious value, long periods required for decomposition are not appropriate for composting of manure. Thus, proper and safe disposal of rice husk is again a big problem. In Maharashtra and particularly Vidharbha region top layers comprises of black cotton soils deposits are observed everywhere which is basically a clayey soil comprises of montmorillonite clay mineral as its major constituent. These soils are black in color thus the name black cotton soil suggested, are found suitable for agricultural purposes but are problematic in nature to the civil engineering projects. Effect of volumetric changes in the form of swelling and shrinkage under the water influence pose numerous problems to the structures built on it such as cracks, undulations, uneven surfacing, settlement of different nature and magnitudes, etc. These soils are having less bearing capacity, less shearing resistance and are generally not suitable / ideal as a foundation soil for construction purposes. Following Fig.1 shows major soil deposits in India. Vidharbha having major deposit of such problematic soils
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Figure 1: Major Soil Deposits in India To make black cotton soils suitable as a good substratum for construction usage improvement in existing properties are necessary. Different ways are available for enhancing engineering performances of soils are soil stabilization, soil reinforcement, etc. Admixtures like lime, cement were used traditionally for stabilization purposes. Recent studies shows Flyash and RHA alone or in combination with lime or cement can be used for effective stabilization of weak soils to a great extent. With the same intention author have undertaken review of utilization of these waste materials as stabilizer and same is presented here. This may found to be an economical treatment method for soils as these materials are available locally and such solution will definitely found beneficial for the developing countries like India where economy is the prime concern for adopting any new method or technique. Additionally, safe disposal mechanism can be suggested for the waste being generated which will help in reducing the hazardous effect on the environment of the region.
FLYASH STABILIZATION Flyash is the finely divided residue that results from the combustion of pulverized coal. Flyash is most commonly used as pozzolan in PCC applications. Pozzolans are siliceous or siliceous and aluminous materials, which in a finely divided form and in the presence of water, react with calcium hydroxide at ordinary temperature to produce cementitious compounds. Flyash is typically finer than Portland cement and lime. Flyash consists of silt-sized particles which are generally spherical, typically ranging in size between 10 & 100 µm. Fineness is one of the important properties contributing to pozzolanic reactivity of flyash. Flyash consists primarily of oxides of silicon, aluminum, iron and calcium. Magnesium, potassium, sodium, titanium and sometimes sulfur are also present to a lesser degree. Flyash used as mineral admixture are classified as either class C or class F based on its chemical composition. American Society for Testing and Materials (ASTM) specification C 618 suggested the chemical composition of class C and class F flyash. Class C ashes are generally obtained from sub-bituminous coals and consist primarily of calcium alumino-sulfate glass as well as quartz, tricalcium aluminates and free lime (CaO). Class C ashes contain more than 20% - 2445 -
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CaO. Class F ashes are typically derived from bituminous and anthracite coal and consist primarily of an alumino-silicate glass, with quartz, mullite and magnetite also present. Class F has less than 10% CaO. Following table 1 gives chemical requirements for flyash to be used as mineral admixture in concrete as per ASTM C 618.
Table 1: Chemical requirement for flyash for use as mineral admixture (ASTM C 618) Mineral Admixture Class
Chemical Composition
F
C
Silicon Dioxide, SiO2 + Aluminum Oxide, Al2O3 + Ferric Oxide, Fe2O3 (min. %)
70.00
50.00
Sulphur Trioxide, SO3, max. %
5.00
5.00
Moisture Content, max. %
3.00
3.00
Loss on Ignition, max. %*
6.00
6.00
Available Alkalis, as Na2O, max. %**
1.50
1.50
Note: * use of class F pozzolana containing upto 12% LOI may be approved by the user if either acceptable performance record or laboratory tests results are made available. ** This is optional requirement applies only when specifically requested.
Table 2: Chemical requirements for flyash for use as pozzolana (IS: 3812 (Part 1) 1981)
Chemical Composition
Requirement
Silicon Dioxide, SiO2 + Aluminum Oxide, Al2O3 + Ferric Oxide, Fe2O3 (min. %)
70.00
Silicon Dioxide, SiO2, % by weight, min.
35.00
Magnesium Oxide, MgO, % by weight, max.
5.00
Sulphur Trioxide, SO3, % by weight, max. %
3.00
Available Alkalis, as Na2O, max. %**
1.50
Loss on Ignition, max. %*
6.00
Flyash color can be light to dark grey depending upon its chemical and composition. FA with high lime concentration has light color. Brownish color associated with high iron content whereas dark color represents unburned carbon content in flyash. Flyash quality is affect by fuel characteristics, various aspects related to combustion and collection processes. In general four - 2446 -
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main characteristics of flyash for use are loss on ignition (LOI), fineness, chemical composition and uniformity. The review of literature (Raymond 1961; Joshi et al.,1975; Gatti and Tripicano ,1981; Leonards and Balley,1982; Mehar 1985; Martin et al, 1990; Usmen et al,1992; Maher et al 1993; Raza and Chandra,1995; Boominathan et al,1996; Sivapullaiath et al, 1996; Singh et al, 1996; Sinha et al, 1998; Sridharan et al, 1998; Digioia and Brendel,1998; Erdal Cokca,2001; Consoli et al,2001; Kaniraj & Havanagi,2001; Pandien et al, 2002; Vimal Kumar,2003; Khadilkar et al.,2003; Phanikumar & Sharma,2004; S Bhuveneshwari, 2005; S Kolias et al,2005; Edil et al.,2006; John L. Daniels et al,2008; Yuanzhao Chen,2009; Emmanuel Okunade,2010; Ramadas T.S.et al, 2011; Michel J. McCharty, 2011; Brooks R et al (2011); Udayshankar et al, 2012 shows that mostly usage of fly ash is in the construction of pavement/highway embankments. The geotechnical characteristics of fly ash, fly ash-soil mixtures were studied by different investigators to suggest its suitability as structural fill / back fill.
LIME/ CEMENT STABILIZED SOIL / FLYASH Chemical stabilizers like cement, lime are added to soil improve its volume stability, strength, stress-strain behavior, permeability, and durability. The improvement in the properties is achieved by the hydration of cement and formation of cementitious products that create strong bond between the soil particles. Soil-cement/soil-lime can be used as a base material in road pavement, slope protection for embankment dams, canals, river banks, spillways, and highway and railway embankments. Any type of soil, except organic soil or highly plastic clays, may be stabilized with cement or lime. Kezdi (1979) discussed cementation effects in both fine grained and granular soil. In finegrained silts and clays, the hydration of cement would result in strong bonds between various mineral substances and the matrix formed encloses the non-bonded soil particles. This matrix develops into a cellular structure, which controls the strength of the stabilized material. This would result in reduction of plasticity and increase of shear strength of the mixture. In granular soils, the particles would be cemented only at their contact points without formation of continuous matrix. The overall strength of the stabilized granular soil would depend on the inter particle bond and the natural strength of the particles themselves. Kezdi concluded that the effect of cementation would be stronger for well-graded soils. Granular soils pulverize and mix more easily than fine grained soils and also, they require less amount of cement resulting in more economical soil-cement. Brief summary of the research work on cement stabilized fly ash or soil-fly ash mixtures carried out by different investigators is given below in Table 4
RHA STABILIZATION Rice husk is a major agriculture byproduct obtained from the food crop of paddy. For every 4 tons of rice 1 ton is of rice husk is produced. Burning of rice husk generates about 15-20% of its weight as ash. RHA being very light is easily carried by wind and water in its dry state. RHA is difficult to coagulate and thus contributes to air and water pollution. Additionally cumulative generation of ash requires large space for its disposal. On the basis of studies carried out on physical and chemical properties of rice husk ash suggested that RHA cannot be used alone for stabilization of soil because of the lack of cementitious properties. The high percentage of siliceous materials in rice husk ash indicates it has potential pozzolonic properties. The normal method of conversion of husk to ash is incineration. Properties of RHA depend upon, whether the husk have undergone complete destructive combustion or have been partially burnt. RHA has been classified into high carbon char, low carbon ash and carbon free ash. On the basis of - 2447 -
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temperature range and burning duration crystalline or amorphous form of silica are obtained from husk ash. Different factors influencing ash properties are incineration condition (temperature and duration), rate of heating, geographic location, fineness, color and crop variety and year of crop production. Research studies have shown that physical and chemical properties of ash are dependent on the soil chemistry, paddy variety and climatic conditions. Studies have also shown that difference may be due to fertilizers applied during the cultivation. The chemical composition of RHA from the various location are given in following table 3 reported by A Muthadi et al (2007) shows that the variation in chemical composition especially silica content is not high (range 85%-95%). All other constituents are available in small range. Color changes are associated with the completeness of combustion process as well as structural transformations of silica in the ash. Ash of white color is an indication of complete oxidation of the carbon, which is also an indication of availability of large portion of amorphous silica in the ash. At high temperature strong interaction between potassium and silica ion cause the formation of potassium polysilicate combined with carbon resulting in grey color ash. At higher temperature with prolonged burning result in ash with pink color representing silica of crystalline form.
Table 3: Comparison of chemical properties of RHA from various locations (Reported by A Muthadhi et al (2007)) Constituent
Weight (%) Netherlands India 86.90 90.70
Malaysia 93.10
Brazil 92.90
Iraq 86.80
USA 94.50
Canada 87.20
Alumina as Al2O3
0.21
0.18
0.84
0.40
0.40
Trace
0.15
Iron as Fe2O3
0.21
0.43
0.73
0.40
0.19
Trace
0.16
Calcium as CaO
0.41
1.03
1.40
0.40
1.40
0.25
0.55
Potassium as K2O
2.31
0.72
2.46
2.20
3.84
1.10
3.68
Magnesium as MgO
1.59
0.35
0.57
0.50
0.37
0.23
0.35
Sodium as Na2O
*
0.02
0.11
0.10
1.15
0.78
1.12
Sulphur as SO3
*
0.10
*
0.10
1.54
1.13
0.24
Loss on Ignition
2.36
*
5.14
4.80
3.30
*
8.55
Silica as SiO2
* Not reported
The review of literature (A S Muntohar (2002, 2005 &2009), E A Basha et al. (2004), J.N. Jha (2004), Chun Yang Yin et al. (2006), Alhaji Mohammed Mustapha et al (2007), T.K. Roy (2008), Musa Alhassan (2008), Sharma R. et al. (2008), V. Ramana Murty et al. (2008), Fidelis Okafor et al. (2009), T.K. Roy (2010), Anwer Hossain et al. (2011), Edeh J.E. et al. (2012) shows that one of the prominent uses of RHA is in improvement of soil performance. The geotechnical characteristics of RHA- soil mixtures were studied by different investigators to evaluate their suitability as stabilizer. Summary of the literature review carried out for the application of RHA as stabilization for soil and are presented in the table 5 below.
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Table 4: Application of solid waste for stabilization of soil Alteration Agent Soil + Flyash
Soil + Flyash
Soil + Flyash
Soil + Flyash
Soil+ Flyash+ Cement
Soil + Flyash
Test Carried out Compaction, Triaxial Shear test (UU test), California Bearing Ratio (CBR), Permeability Compaction, Triaxial compression test, Consolidation, CBR
Atterberg’s Limit, Compaction, Permeability, Triaxial Compression test Atterberg’s Limit, Compaction, Triaxial Compression test, Chemical Analysis, Consolidation Particle size distribution, UCS, Chemical analysis
Particle size distribution, Compaction test, Permeability, Consolidation,
Remarks
References
Suitability of Agecroft and bold hopper fly ashes, from U.K., for use as an embankment fill material. As the duration of curing increases CBR values increased. Trial embankment sections were constructed and monitored for a year. From the laboratory and field data, it was concluded that pulverized fuel ashes could be successfully used as an embankment material especially on soft compressible ground.
Raymond (1961)
Investigations for the use of flyash structural fill material collected from Grand Avenue power plant of Kansas City power and Light Company (KCPL), U.S.A. Significant improvement observed in shear strength after one week curing period. It was observed from consolidation test results fly ash did not compress significantly under ordinary loads. Trial sections were constructed at Missouri river flood plain close to Hawthorn plant. The post construction test results indicated that fly ash could be used for structural fill and as a lightweight backfill behind retaining structures. Similar, geotechnical investigations on coal ashes collected from Vado Ligure Power plant, Italy. Variation of strength and deformability characteristics of fly ash with time was studied. Improvement in the permeability characteristics and consistency limits of soil mixes observed with increase in curing periods.
Joshi et al. (1975)
Attempt was made to proposed use of Indianapolis fly ash, USA as a structural fill material. From the compaction test results it was observed that the variation of dry density was irregular at higher moisture contents. Bleeding was initiated at moisture contents resulted in erratic 40% and the bleeding moisture content corresponded to optimum moisture content. From the findings it was proposed that finer ash samples exhibited higher strength as compared to the coarser samples. It was observed that, calcium content and particle size distribution of fly ashes are the most important parameters that influenced the rate of strength development. Compressive strength tests were carried out on the different fly ash-cement mixtures. The development of high strength in high calcium fly ashes was due to the presences of reactive crystalline compounds as C3A and a more active calcium aluminosilicate glass. In case of low calcium fly ashes reactivity was found to be directly proportional to particles size 45 µm. High calcium fly ashes were relatively less sensitive to particle size distribution. Geotechnical properties of fly ashes from coal burning utilities in Pennsylvania, Delaware, and New Jersey, USA, to investigate their suitability in construction of highway embankments. Fly ash in partially saturated state displayed an apparent cohesion due to tensile stresses of retained capillary water. Hence, the effective friction angle, Φ’, was considered as the major factor for long term stability analysis. Results of the standard extraction procedure toxicity tests showed low metal leaching characteristics of fly ash.
Leonard & Bailey (1982)
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Gatti & Tripicano (1981)
Mehta (1985)
Martin et al. (1990)
Vol. 17 [2012], Bund. Q Soil + Flyash+ Lime+ Cement
Compaction, UCS, durability & permeability
Soil + Flyash + Lim Sludge Soil + Flyash + geofabric
Compaction & UCS
Compaction, Swelling, CBR & UCS
Soil + Flyash + Lime
Atterberg’s Limit, Compaction, UCS
Soil + Flyash
Atterberg’s Limits, Compaction, UCS, Consolidation
Soil + Flyash+ Lime /Cement
Atterberg’s Limits
Soil + Flyash+ Lime
Atterberg’s Limits, Compaction, CBR, UCS
Soil + Pond
Grain size distribution,
2450 Properties of fly ashes from Soma B power plant in Mania, Turkey and Yatgan power plant in Mugla, Turkey, to assess their potential for utilization in pozzolanic pavements and liners. From compaction test results it was observed that with increasing stabilizer content, MDD decreases and OMC increases up to 10 % stabilizer. Test results showed for both fly ashes, the strength increases with increase in cements content for all curing periods. Increasing lime content, on other hand, shows decrease in compressive strength for both fly ashes at 7 and 28 days curing periods Whereas trend was different at 3 days curing, showed continual increase. Combined stabilizer (7.5% lime + 7.5 % cement) produced intermediate results. Laboratory studies to find the feasibility of lime sludge amended fly ash for utilization as an engineered fill material. It was observed that the mixes compacted well and possessed relatively high compressive strength. The mixtures had low permeability and were successfully utilized as landfill cap and as a liner material. Studies carried out for use of fly ashes to stabilized alluvial soils, so as to use them as sub grade and base course in airfield and road pavements. The tests were conducted on fly ash, soil and their mixtures having various fly ashes: soil ratio. The study indicates that soil treated with fly ash gave considerable improvement in CBR value of soil. With incorporation of geofabric CBR value further increased In India studies has been carried out to proposed use of flyash for stabilization of soils collected from Ennore thermal power station, Chennai with and without lime incorporate. Addition of lime to fly ash resulted in flocculation and particle aggregation. It was observed that WL and WP were reduced with the lime treatment whereas UCS increased by about 25 %. The compressibility of fly ash reduced to almost one fourth of the original value due to lime treatment. It was concluded that lime treated fly ash could be effectively used for embankment over soft clays. Review of geotechnical characteristics of the fly ashes from different power plants in India presented by the author. Shear strength properties of fly ash were affected by variations in density, moisture content, particle size distribution and chemical composition. Primary consolidation of fly ash was very quick. It was also reported that the heavy metal ion retention characteristics of fly ash were dependent on the free calcium oxide content. High calcium fly ash retained large amounts of metal ions compared to low calcium fly ash. Studies carried out to analyze effect of fly ashes from Neyveli and Vijaywada, India, to back cotton soil collected from Davangere, Karnataka state, India. Effect on plasticity index was investigated; it was observed that, with increase in flyash content WL decreases and WP increases leads decrease in IP. It was proposed that the use of fly ash for the stabilization of these soils was considered as an effective and economical method compared to cement or lime stabilization. Addition of fly ash improved the physical of back cotton soil significantly. Effects of different proportions mixes of lime and fly ash on local soil of Varanasi evaluated to propose suitability of fly ash-soil lime as a base and subbase material for the roads. From the study, it was conclude that good results were obtained when soil was stabilized with 15 % of lime and fly ash in the proportion of 1:3. Different proportions enabled an increase in the CBR value from 4.00 % to 20.70 % and the unconfined compressive strength from 134 KN/m2 to 680 KN/m2. Geotechnical characteristics of Indian coal ashes discussed which include fly ash, bottom ash pond ash. Coal
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Usmen et al. (1992)
Maher et al. (1993) Raza & Chandra (1995)
Boominathan & Ratnea (1996)
Shridharan et al. (1996)
Sivapullaiath et al. (1996)
Singh et al. (1996)
Sridharan &
Vol. 17 [2012], Bund. Q ash
Soil + Flyash
Soil + Flyash + Carbide lime
Permeability, Compaction test, specific gravity
Atterberg’s limit, Swelling test, Compaction test, Consolidation test, Chemical analysis Compaction, Brazilian tensile test, Triaxial compression test
Soil + Flyash
Compaction
Soil + Flyash
Compaction, CBR
Soil + flyash + Cement
Soil + Flyash
UCS test
Free Swell Index, Swelling potential, Atterberg’s limit, Compaction, UCS, Hydraulic conductivity
2451 ashes had low specific gravity and were non-plastic. It was reported that the moisture content- dry density relationship was influenced by their specific gravity. Apparent cohesion was developed in the partially saturated state and the coefficient of permeability depended on grain size distribution, degree of compaction, and pozzolanic activity. It was observed that, coal ashes had high rate of primary consolidation and the secondary consolidation depended on free lime content, carbon content and chemical composition. Carried out investigations using Soma Flyash and Tuncbilek flyash and added it to expansive soil at 0-25%. Specimens with flyash were cured for 7days and 28 days and then after tests were conducted. From his experimental findings it was confirmed that the plasticity index, activity and swelling potential of the samples decreased with increasing percent stabilizer and curing time and the optimum content of flyash in decreasing the swell potential was found to be 20%. He concluded that both high and low calcium class C fly ashes can be recommended as effective stabilizing agents for improvement of expansive soils. Addition of carbide lime and flyash improved the stress-strain behavior of a sandy soil. The friction angle, cohesion and average modulus shows increasing trend. The maximum triaxial stiffness occurred for the specimen molded on the dry side of OMC, while the maximum strength occurred at OMC as an effect of initial reaction. After 28 days, pozzolanic reactions magnified brittleness and further increased triaxial peak strength and stiffness. Correlations were established for MDD of compacted fly ash in terms of OMC and specific gravity (G). The correlations of MDD with OMC were expressed in the form of log-log, exponential, and linear curves. Fly ashes used in the study were obtained from Rajghat thermal power station, New Delhi and Chemical manufacturing company, Bochum, Germany. The study indicates that, the correlations would be useful for the efficient design of the compaction test and for field compaction control. Studied the effect of two types of fly ashes Raichur fly ash (Class F) and Neyveli fly ash (Class C) on the CBR characteristics of the black cotton soil. From the tests findings it was concluded that, incase of use of Raichur flyash the variation of CBR of fly ash-BC soil mixes can be attributed to the relative contribution of frictional or cohesive resistance from fly ash or BC soil. Whereas for Neyveli fly ash use increase of strength with the increase in the fly ash content, additional puzzolonic reaction responsible for forming cementitious compounds resulting in good binding between BC soil and fly ash particles Experiments to evaluate the factors influencing strength of cement fly ash base courses. Stabilizer content was determined by conducting UCS test on stabilized fly ash specimens cured at different curing conditions. Six different curing conditions, including controlled and ambient conditions, were adopted in the study. It was reported that, UCS of stabilized flyash specimens depends on curing, unit weight, and water content in addition to cement content, curing period. Effect of fly ash on engineering properties of expansive soil was studied through an experimental programme. Flyash added to the soil at varying proportions causes’ reduction in plasticity characteristics and FSI by about 50% by the addition of 20% fly ash. The hydraulic conductivity of expansive soils mixed with flyash decreases with an increase in flyash content, due to the increase in maximum dry unit weight with an increase in flyash content. Effect of fly ash is akin to the increased compactive effort; hence the expansive soil is rendered more
- 2451 -
Pandian (1998)
Erdal Cokca (2001)
Consoli et al. (2001)
Kaniraj & Havanagi (2001)
Pandian et.al. (2002)
Kaniraj & Gayathri (2003)
Phanikumar & Sharma (2004)
Vol. 17 [2012], Bund. Q
Soil + Flyash
Soil + Flyash + Cement Soil + Flyash
Atterberg’s Limits, Compaction, UCS, Core Cutter Atterberg’s Limits, Compaction, UCS, Split tensile strength, Flexural strength, CBR
2452 stable. Undrained shear strength of the expansive soil blended with flyash increases with the increase in the ash content. Reported improvements in properties of expansive soil treated with fly ash at varying percentages. Both laboratory trials and field tests have been carried out. It is observed that field application is through mixing of the two materials (expansive soil and flyash) in required proportion to form a homogenous mix. Trial embankment of 30 m length by 6m width by 0.6m thickness constructed and insitu tests were carried out Strength tests were carried out on samples prepared with various percentages of fly ash & cement. In-situ stabilized subgrade with flyash and cement were analyzed for construction traffic and for operating traffic. Results were compared with conventional flexible pavements without improved subgrades shows technical benefits of stabilizing clayey soils with fly ash and cement.
S Bhuveneshwari et al (2005) S. Kolias et al (2005)
Atterberg’s Limits, CBR test
Evaluate the effectiveness of self cementing fly ashes from combustion of sub-bituminous coal at electric power plants for stabilization of soft fine grained soils. Tests were conducted on soil and soil-fly ash mixtures prepared at different water contents. The results indicated that, addition of fly ash appreciably increased CBR and resilient modulus of soils.
Edil et al. (2006)
Soil+ Flyash + Lime + Gypsum
Leaching test, compaction
Ambarish Ghosh & Chillara Subbarao (2006)
Soil+ Flyash + Lime + Gypsum
UCS, CBR, Tensile strength test
Results of leaching tests carried out on lime –flyash stabilized with or without gypsum in soil presented. It is reported that gypsum has been found effective in reducing the leaching of lime from flyash stabilized with lime. Effects of factors like lime content, gypsum content, curing period, and flow period on the leaching of lime from compacted stabilized flyash matrix. Compacted specimens were cured for 7 and 28 days. Concentration of calcium in the leachate was reduced to 80 from 540 ppm for addition of 1% gypsum to flyash stabilized with 10% lime and cured for 28 days. Laboratory tests results of flyash stabilized with lime alone or in combination with gypsum are discussed. Effect of lime content, gypsum content and curing periods on tensile strength, bearing ratio, durability characteristics of stabilized flyash analyzed. UCS test results for the mixes cured at 0 days are presented to develop relationship between tensile strength and UCS. It is reported that flyash stabilized with lime and gypsum showed medium durability after 28 days curing and thereafter increase with increasing curing periods. Empirical model to estimate tensile strength, bearing ratio and durability indices of stabilized flyash from UCS test results were proposed. Use of lime and FGD gypsum material to stabilize coal combustion fly ash was evaluated. Five test pads were constructed to evaluate the influence of lime and FGD gypsum on fly ash leachability and to measure the effect on permeability, durability, strength and constructability. Measurements were made in the field and also with remolded laboratory specimens. Results suggested that lime influences fly ash leachability, although this varies according to mixing condition, as well as the contaminant of concern. Lime amendment reduced the mobility of cadmium; however, arsenic, chromium and selenium were all present at increased concentrations relative to the test pad constructed of fly ash alone.
John L. Daniels & Gautham P. Das (2008)
Soil + Flyash + Lime + Gypsum
Permeability, Durability, UCS
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Ambarish Ghosh & Chillara Subbarao (2006)
Vol. 17 [2012], Bund. Q Soil + Flyash + Lime + Cement
Soil + Flyash
2453
UCS, Compaction, Cleavage strength,
Attempt was made and reported to overcome long curing duration problems of associated road construction using cement by provide early strength of lime and fly-ash stabilized macadam. Various tests were carriedout on limefly ash-cement stabilized macadam applying standard curing (T: 20±2°C, RH: ≥95%) and high-temperature curing (T: 60±2°C, RH: ≥95). Further, relationship curve between strength and curing age is found by applying different regression models. Strength gain relationship between high temperature curing and standard curing is achieved. It is reported that, high temperature curing helps in reducing longer curing periods and help in early strength gaining.
Atterberg’s limit, CBR, UCS
Effects of addition of self-cementing coal fly ash on the engineering properties of three lateritic soils from southwestern Nigeria were studied. It was observed, for all the soils, that increasing coal fly ash contents brought about increasing improvements in the plasticity and mechanical properties of the soils. At 12.5% flyash addition to the soil reduction in WL, IP and OMC observed with increase in MDD and CBR. Studies carriedout in laboratory for utilization in road base and sub-base construction of class F flyash alone and stabilized with varying percentages of lime and phosphogypsum. Empirical model has been developed to estimate the bearing ratio for the stabilized mixes through multiple regression analysis and linear empirical relationship presented to estimate soaked CBR from unsoaked CBR for stabilized pond ash. Test results indicates that pond ash-lime-phosphogypsum have potential applications as road base and sub-base. Laboratory tests on expansive soils treated with lime and flyash are conducted. Properties of expansive soils are noticed in a better improved way. Three expansive soils for tests taken from Amalpuram, Bhimavaram and Warangal. Result shows addition of lime 4% improvement of strength is about 40%-60% whereas swelling pressure reduced by 4 times at 10% lime addition. Investigated possible utilization of flyash to overcome sulphate heave experienced by soil-lime mix. Clay containing soluble sulphate may react with lime to form ettringite, causing increase in volume called heave. Incorporation finer flyash help in reduction of heave suggested on the basis of physical (Scanning electron microscopy and mercury intrusion porosimetry) and composition (X-ray diffraction) analysis. Effects of various locally available stabilizing agents like OPC, lime and flyash have been studied for strength improvement. Specimens were prepared by mixing varying proportions stabilizers with clayey soils separately. UCS and Atterberg limits of the soils were determined separately after curing specimens for 7 days. 7.5%-8% of portland cement gave UCS strength is around 28 kg/cm2 which is satisfactory for road use under Indian climatic condition. 7 days peak strength of soil-lime specimen was found at 7.5% lime content. Evaluated the effect of post‐compaction moisture variations on the resilient modulus (MR), UCS and modulus of elasticity (E) of cementitiously stabilized subgrade soils. Class C fly ash (CFA) and hydrated lime were used as the stabilizing agents. Results showed that MR, UCS and E values increased due to drying and decreased due to wetting. MR‐moisture, UCS‐moisture and E‐moisture models were developed and proved to be useful in predicting the variations of MR, UCS and E values of stabilized subgrade soils with moisture changes. These models can be used, in the new M‐E PDG, to predict MR, UCS and E values of stabilized sub‐grade soils with
Soil + Flyash + Lime + gypsum
Compaction, CBR
Soil + Flyash + Lime
Atterberg’s limit, compaction, UCS & swelling test
Soil + Flyash + Lime
Grain size distribution, Compaction, Swelling, Fineness test,
Soil + Flyash + Lime
Atterberg’s limit, Compaction, UCS
Soil + Flyash + Lime
Compaction, UCS, CBR
- 2453 -
Yuanzhao Chen (2009)
Emmanuel Okunade (2010) Ambarish Ghosh (2010)
Ramadas T.S. et al (2011)
Michael J McCharty et al (2011) Purbi Sen et al (2011)
Brooks, R. et al (2011)
Vol. 17 [2012], Bund. Q
Soil + Flyash
Atterberg’s limit, Compaction, UCS, CBR
2454 moisture variations Investigation program was undertaken to stabilize black cotton soil in Hubballi - Dharwad using flyash. Significant improvement in index properties, compaction and strength characteristics of black cotton soil observed under Dandeli flyash. It is reported that the effect of flyash treatment depending upon the quantity of flyash mixed with the black cotton soil for stabilization.
Udayashankar et al (2012)
Table 5: Application of RHA for stabilization of soil Alteration Agent Soil + RHA +Lime
Test Carried out
Remarks
References
Compaction, UCS
Investigation on utilization of ashes produced from uncontrolled rice husk burnt in Yogyakarta, Indonesia. Tests were carried out individually or in combination in which RHA content were varied from 7.5, 10 and 12.5 % and lime content from 2,4,6 and 10% (by dry weight of soil). Remolded samples were tested at OMC and MDD shows decrease in swelling potential of expansive soils and improvement in strength and bearing power under soil-lime-RHA.
A.S. Muntohar (2002)
Soil + RHA +Cement
Atterberg’s Limit, Compaction, UCS
Stabilization of residual soil using cement and rice husk ash. Investigation includes evaluation of properties of soil such as compaction, strength and X-ray diffraction. Test result shows that both cement and RHA reduces the plasticity of soils. In terms of compressibility, addition of rice husk ash and cement decreases MDD and increases OMC. From the viewpoint of plasticity, compaction, strength characteristics and economy addition of 6-8% cement and 10-15% RHA is recommended as an optimum amount.
E.A. Basha et al (2004)
Soil + RHA +Lime
Compaction, UCS
Laboratory test results of RHA+ Lime stabilized soils are discussed. Amount of lime required for stabilization (LRS) is determined by Eades and Grim's Method. It is reported that UCS of stabilized soils decreased with increasing molding water content, but it is still higher than of the un-stabilized soils. In general, higher lime content results to a higher UCS. The maximum strength of the stabilized soil is attained at lime-RHA ratio of 1/2. The UCS of the stabilized soil increased significantly about 7- 9 times to the un-stabilized UCS.
A.S. Muntohar (2005)
Soil + RHA +Lime
Compaction, CBR UCS
Evaluates the effectiveness of using rice husk ash as a puzzuolanae to enhance the lime treatment of soil. Studies carried out on influence of different mix proportions of lime and RHA on various properties of the soil. The result shows that addition of RHA enhances only strength developments but also durability of lime stabilized soils.
J.N. Jha (2006)
Soil + RHA
Compaction, UCS,
Study of solidification/stabilization of lead contaminated soil using OPC and RHA presented. Effect of varying lead
Chun-Yang Yin
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Vol. 17 [2012], Bund. Q + Cement
pH test
Soil + RHA + Cement
Compaction, CBR, UCS
Soil + RHA
Compaction, CBR, UCS
Soil + RHA + Lime + Calcium Chloride
Compaction test, UCS test, CBR test
Soil + RHA + CaCl2
Compaction test, Swelling test, UCS test
Soil + RHA + Cement
Atterberg’s Limits, Compaction test, UCS test
Soil + RHA
Atterberg’s Limits, Compaction test, UCS test
2455
concentrations (in the form of nitrates) in soil samples on physical properties such as UCS, setting times to early mixtures and changes in crystalline phases as well as chemical properties like leachability of lead, pH, alkalinity of leachates are studied. Results indicates that usage of OPC and RHA as an binder system for stabilization of lead contaminated soil is more favorable in reducing the leachability of lead from treated soil than a binder system with OPC alone. Laboratory tests were carriedout on the laterite soil collected from Maikunkele area of Minna, Nigeria. Soil was stabilized with 2-8% cement. Effect of RHA on the soil was investigated with respect to compaction characteristics, CBR and UCS test. Result shows, general decrease in MDD and increase in OMC all with increase in RHA content from 2-8% at specified cement content. Substantial improvement in CBR and UCS with increase in RHA content at specified cement contents. Reported the use of rice husk ash for stabilization of lateritic soil of Maikunkela area of Minna, Nigeria. Performance of soil-RHA was investigated w.r.t. compaction characteristics, CBR and UCS. Test result indicates a general decrease in MDD and increase in OMC with increase in RHA content. In addition to this, improvement in CBR and UCS observed under the application of RHA & max. UCS recorded at 6-8% RHA. Experimental results obtained from tests conducted on remolded expansive soil specimens blended with RHA and stabilized with lime and calcium chlorides are discussed. The amounts of RHA, lime, and calcium chloride were varied from 0-16%, 0-5%, and 0- 2%, respectively, by dry weight of the soil. It was found that the stress-strain behavior of expansive clay improved upon the addition of up to 5% lime or up to 1% calcium chloride. Maximum improvement in failure stress of 225 and 328% was observed at 4% lime and 1% calcium chloride, respectively. RHA content of 12% was found to be the optimum with regard to both UCS and CBR in the presence of either lime or calcium chloride. An optimum content of 4% in the case of lime and 1% in the case of calcium chloride was observed even in clay-RHA mixes. Modification of black cotton soil using CaCl2 and rice-husk-ash (RHA), which resulted in two favorable combinations of soil+0.5% CaCl2 +8% RHA and soil +1% CaCl2 +6% RHA with non swelling properties, while retaining high unconfined compressive strength values. The mix of soil +0.5% CaCl2 +8% RHA was taken for further study in view of its economy due to lower CaCl2 content. The field heaves measurements of footings, pavement slabs, and canal lining panels cushioned with the proposed chemically stabilized soil (CSS) mix revealed that the CSS cushion can effectively reduce their heave and hence it can be recommended as an alternative to conventional CNS cushion in localities of scarcity for suitable CNS materials. Chemical stabilization using RHA and cement suggested. Three types of soils namely residual soil, kaolinite soil and bentonite were used in the study. Experimental studies include evaluation of index properties of soil and compaction, alongwith characterization of materials by X-ray diffraction. Test result shows that both cement and RHA reduces plasticity of soils, decrease in MDD and increase in OMC observed. Effect of RHA on geotechnical properties of soil classified as A-2-6 or SW for sub grade purpose. Investigation includes evaluation of properties such as compaction, consistency limits and strength of soil with RHA content of 5%, 7.5%, 10% and 12.5% by weight of dry soil. The results obtained show that the increase in RHA increased the OMC
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et al (2006)
Alhaji Mohammed Mustapha et al (2007) Musa Alhassan (2008)
Sharma R., Phanikumar B., & Rao B. (2008)
V. Ramana Murty et al (2008)
A.S. Muntohar (2009)
Fidelis Okafor et al (2009)
Vol. 17 [2012], Bund. Q
Soil + RHA + Lime +
Compaction test, UCS test, CBR test
Soil + RHA Pond Ash + Lime
Compaction test, CBR test
Soil + RHA + Cement Kiln Dust
Atterberg limits, compaction, UCS , Splitting tensile strength,, CBR Durability Grain Size Distribution, Compaction, CBR test.
Soil + RHA + Cement
Soil + RHA + Cement
Compressive strength
2456
but decreased the MDD. Increase in RHA content reduces plasticity and increased volume stability as well as strength of soil. 10% RHA content was observed to be the optimum content. An experimental study was undertaken to explore the possibility of utilization of the alternative materials like pond ash, rice husk ash (RHA) by mixing with local alluvial soil by adding small percentage of lime for the construction of road subgrade as cost effective mix. Investigation was undertaken using rice husk ash (RHA) and pond ash with soils to enhance the quality of the soil as subgrade material. CBR value in soaked and unsoaked condition increases in a small amount for addition of RHA, but with addition of lime in RHA mixed soils, better increment has been observed in the CBR values both in the soaked and unsoaked conditions. Further mixing pond ash with the soil showed increment in CBR both in unsoaked and soaked condition and mixing of pond ash upto 150% has shown that the gain in CBR value is more than double for soaked and unsoaked conditions Cement kiln dust, rice husk ash, and their combinations are used variously as stabilizers in different percentages (maximum up to 20%) to develop and evaluate stabilized clayey soils. Correlations between strength, modulus of elasticity and CBR are established. It is reported that, developed stabilized soil mixtures have shown satisfactory strength and durability characteristics and can be used for low-cost construction to build houses and road infrastructures. Laboratory evaluation of the characteristics of rice hush ash (RHA) stabilized reclaimed asphalt pavements (RAP) subjected to British Standard light; BSL (standard Proctor) compactive effort to determine the compaction characteristics and CBR values was carried out. Test results show that the properties of RAP improved when treated with RHA, using up to 2% cement additive. The particle size grading improved from 100% coarse aggregates for 100% RAP to 10 - 90% coarse aggregate with 10 - 90% fines for the various RAP + RHA mixtures containing up to 2% cement. The CBR values also increased from 8 and 14% for the unsoaked and soaked conditions, respectively, for 100% RAP content to 73 and 79% (soaked condition) for 89.25% RAP in the RAP/RHA mix proportions with 1.5% cement/89% RAP content in the RAP/RHA mix proportions with 2% cement content, with corresponding unsoaked CBR values of 28 and 26%, respectively. Generally, soaked samples recorded higher CBR values than unsoaked samples. The RHA stabilized RAP mix proportions with 89.25% RAP/1.5% cement content, and 89% RAP/2% cement content with CBR values of 73 and 79% (soaked for 24 hours) can be used as subbase or subgrade materials in road construction. Investigation carriedout to propose use of RHA in to the cement stabilized rammed earth system. Best suited mixture to meet the normal masonry requirements was selected for the construction of prototype building, which underwent technical assessment of its structural and thermal performance and of the durability of its cement-stabilized rammed earth-RHA wall. Results showed that sandy soil, when partially replaced by the maximum ash content 7.5% and stabilized with 10% cement, proved to be promising alternative material. It is proved high quality construction material that can be used for build energy efficient houses
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T.K. Roy (2010) T. K. Roy et al (2010)
Hossain Anwar, K. (2011)
Edeh J. E. et al (2012)
Ana Paula Da Silva Milani et al (2012)
Vol. 17 [2012], Bund. Q
2457
CONCLUSION On the basis of literature survey carriedout following concluding remarks are made; •
The quality of fly ash produced depends on different factors as the degree of pulverization of coal, design of furnace, changes in coal supply, changes in boiler lad and hence in firing conditions.
•
Depending upon the CaO content flyash can be categorized as class C and class F flyash. Class C flyash has high CaO content whereas class F flyash contain low CaO.
•
Physical and chemical properties which influence the pozzolanic reactivity of the fly ash are unburnt carbon content or loss on ignition, specific surface area, silica, alumina and lime content.
•
Fly ash can be used for variety of civil engineering applications like lower layers of road pavement, in the development of low permeability flowable fill, material, as a dike material, and as reclamation material.
•
Cement/ lime stabilized soil-fly ashes mixtures can be used in a variety of civil engineering applications.
•
Stabilized material can be used as an embankment fill material, for improving soils for embankment foundations, sub-base and base course layers of road pavement
•
Unconfined compressive strength of stabilized soil-fly ash mixtures depends not only on curing time but also on the cement and the fly ash content.
•
Rice husk ash an agricultural waste can be effectively used for stabilization of soils using cement or lime as additive.
•
Rice husk ash is source of silica has numerous applications in silicon based industries.
•
Type of silica formed from RHA is depends upon temperature and duration of heating. At temperatures ≤ 6000C amorphous silica forms, whereas at greater temperature ≥ 9000C crystalline silica obtained.
•
Addition of RHA to the soil in general increases optimum moisture content and reduces the maximum dry density.
•
Rice husk ash and lime/ cement altered the texture of clay soil by reducing the fine particles.
•
RHA and lime/cement improves plasticity index and swelling potential of expansive soils reduces with admixture addition.
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45. Sharma, R., Phanikumar, B., and Rao, B. (2008). “Engineering Behavior of Remolded Expansive Clay Blended with Lime, Calcium Chloride, and Rice-Husk Ash.” Journal of Material in Civil Engineering, Volume 20, ASCE, 509–515. 46. Basha et al (2009) “Effect of Cement- rice Husk Ash on the plasticity and Compaction of soil.” Electronic Journal of Geotechnical Engineering. Volume 8 47. Fidelis Okafor et al (2009) “Effect of Rice Husk Ash on Some Geotechnical Properties of Lateritic soil.” Leonardo Electronic Journal of Practices and Technologies, Issue 15, 67-74. 48. Robert Brooks (2009) “Soil Stabilization with Flyash and Rice Husk Ash.” International Journal of Research and Reviews in Applied Sciences, vol.1, 20-217. 49. Kharifa Harichane et al (2009) “Effect of combination of lime and natural pozzolona on the plasticity of clayey soils.” Proceeding of 2nd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering, 574-581. 50. Yuanzhao Chen, Zhenxia Li, and Xuancang Wang (2009) “Research on Rapid Curing Technology of Lime-Flyash-Cement Stabilized Macadam.” Proceeding of International Conference of Chinese Transportation Professionals (ICCTP 2009), 1-8. 51. Joel Beeghly et al (2010) “Dredge Material Stabilization Using the Pozzolanic or SulfoPozzolanic Reaction of Lime By-Products to Make an Engineered Structural Fill.” International Journal of Soil, Sediment and Water, vol.3, 1-21. 52. Felix Okonta et al (2010) “Compaction and Strength of Lime – Flyash Stabilized Collapsible Residual Sand.” Electronic Journal of Geotechnical Engineering, vol. 15, 1976-1988. 53. M Ahmaruzzaman (2010) “A review on the utilization of fly ash.” Journal of Progress in Energy and Combustion Science, Elsevier, 327-363. 54. T.K. Roy et al (2010) “Effect of Alternative Materials on Engineering Properties of Alluvial Soil for Construction of Road Subgrade.” Proceeding of Traffic and Transportation Studies 2010, 1331-1340. 55. Ambarish Ghosh (2010) “Compaction characteristics and bearing ratio of pond ash stabilized with lime and phosphogypsum.” Journal of Materials in Civil Engineering, ASCE, 343-351. 56. K. Mallikarjuna Rao et al (2010) “Influence of Fly Ash on Compaction Characteristics of Expansive Soils Using 22 Factorial Experimentation.” Electronic Journal of Geotechnical Engineering, vol. 13, 1-19. 57. Tapash kumar Roy (2010) “Influence of Lime on Alluvial Soil Strengthened with Pond Ash and Rice Husk Ash for Construction of Subgrade of Road.” Proceeding of GeoShanghai 2010, 385391. 58. Vimal Chandra Pandey et al (2011) “Impact of Flyash incorporation in soil systems.” Journal of Agriculture, Ecosystems and Environment, ELSEVIER, 16-27. 59. M.J. McCarthy et al (2011) “Identifying the role of fly ash properties for minimizing sulfateheave in lime-stabilized soils.” Journal of Fuel, Elsevier, 27-36. 60. Erdem Tastan et al (2011) “Stabilization of Organic Soils with Fly Ash.” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 819-833. 61. Lokeshappa B et al (2011) “Disposal and Management of Flyash.” Proceeding of 2011 International Conference on Life Science and Technology, vol.3, 11-14. 62. Khelifa Harichane et al (2011) “Effect of curing time on shear strength of cohesive soils stabilized with combination of lime and natural pozzolana.” International Journal of Civil Engineering, vol.9, 90-96. - 2460 -
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63. Y. Mleza, M. Hajjaji (2011) “Microstructural Characterization and physical properties of cured thermally activated clay-lime blend”. Journal of Construction and Building Materials, Elsevier, 226-232. 64. J Alam et al (2011) “Flyash Utilization in different sector in Indian Scenario.” International Journal of Emerging Trends in Engineering and Developments, vol.1, 1-14. 65. T.K. Ramadas et al (2011) “Geotechnical characteristics of three expansive soils treated with lime and flyash.” International Journal of Earth Sciences and Engg. vol.4, 46-49. 66. Purbi Sen et al (2011) “Evaluation of Strength Characteristics of Clayey Soil by Adding Soil Stabilizing Additives.” International Journal of Earth Sciences and Engineering, vol.4, 10601064. 67. G.V. Rama Subbarao et al (2011) “Industrial Wastes in Soil Improvement.” International Scholarly Research Network, ISRN Civil Engineering, vol. 2011, 1-5.
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© 2012 ejge
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