STABILIZATION OF WASTE DUMP USING FLYASH

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Bangalore is facing problems due to old municipal solid waste dump yards
situated close to the expanding city as they are in the expansion zone of growing city. These
dump yards needs to be reclaimed for infrastructure development such as roads, buildings and
other needs. To reclaim the old dump sites, it is necessary to know the characteristics of solid
waste, more particularly the geotechnical properties. The characteristics of dumps sites are not
generally suitable for foundations of most types of structures coming on them and their
properties need to be improved. Also their characteristics vary change with aging due to their
degradation. This paper presents the results of stabilization of dumped waste by addition of
pozzolanic material such as fly ash. Laboratory tests such as Direct shear and California
Bearing Ratio (CBR) have been performed on dumped waste with fly ash. It was found that
addition of 20% of fly ash the shear strength of dumped waste has increased considerably. Also
CBR of stabilized waste dumps, which is important in the reclamation of dumped sites, has been
analyzed. It was that CBR of stabilized dumps was higher value for 5 mm penetration than for
2.5 mm penetration and tests were conducted to confirm the same. It was observed that the
improvement in CBR is promising and further studies are required to improve to the material to
form suitable for foundations.

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STABILIZATION OF WASTE DUMP USING FLYASH

  1. 1. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 217 STABILIZATION OF WASTE DUMP USING FLYASH B. P. Naveen1 , P.V.Sivapullaiah2 , T.G.Sitharam3 and A.K. Sharma4 1, Research Scholar, Dept. of Civil Engg. IISc, Bangalore, Email: bpnaveen@civil.iisc.ernet.in 2, Professor, Dept. of Civil Engg.,IISc, Bangalore, Email: siva@civil.iisc.ernet.in 3, Professor, Dept. of Civil Engg.,IISc, Bangalore, Email: sitharam@civil.iisc.ernet.in 4, Research Scholar, Dept. of Civil Engg. IISc, Bangalore, Email:anilkr@civil.iisc.ernet.in ABSTRACT: Bangalore is facing problems due to old municipal solid waste dump yards situated close to the expanding city as they are in the expansion zone of growing city. These dump yards needs to be reclaimed for infrastructure development such as roads, buildings and other needs. To reclaim the old dump sites, it is necessary to know the characteristics of solid waste, more particularly the geotechnical properties. The characteristics of dumps sites are not generally suitable for foundations of most types of structures coming on them and their properties need to be improved. Also their characteristics vary change with aging due to their degradation. This paper presents the results of stabilization of dumped waste by addition of pozzolanic material such as fly ash. Laboratory tests such as Direct shear and California Bearing Ratio (CBR) have been performed on dumped waste with fly ash. It was found that addition of 20% of fly ash the shear strength of dumped waste has increased considerably. Also CBR of stabilized waste dumps, which is important in the reclamation of dumped sites, has been analyzed. It was that CBR of stabilized dumps was higher value for 5 mm penetration than for 2.5 mm penetration and tests were conducted to confirm the same. It was observed that the improvement in CBR is promising and further studies are required to improve to the material to form suitable for foundations. KEYWORDS: California Bearing Ratio, Direct shear, Municipal solid waste, Waste dump INTRODUCTION: Solid Waste Management is a very complex common problem in both developing and developed countries. Improper management in developing countries results in dirty public areas, waste recovery in the streets, dumping of garbage into streams and rivers, or open dumps leading to men, women and children made through the waste subjecting all of them to all kinds of diseases and accidents. The problem is aggravating due to rapid population growth, industrial development and changing eating habits and wide spread use of disposable containers. Many cities including Bangalore are also facing problems due to old dump yards situated close to the expanding cities (Naveen et al. 2013). These dump yards needs to be reclaimed for growing needs of the city infrastructure development. Already several of them have been reclaimed
  2. 2. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 218 without proper improvement causing distress to structures founded on them. To reclaim the old dump sites it is necessary to know the intrinsic qualitative and quantitative characteristics of solid waste as its increase demands alternative methods of handling, treatment and disposal. The characteristics of waste change with aging due to their degradation with aging. Geotechnical properties of the waste from dump site are generally don’t possess adequate geotechnical properties to support foundations for infrastructure development activities. Most of the prior dump sites have been reclaimed without proper treatment for laying road and construction of foundation, many residential and industrial structures (Naveen et al, 2014). These structures undergo large settlements and may also cause several failures. Further most of the dumpsites or reclaimed for road works. Need for Stabilization of dumped Waste for Pavements Thus, there is a need to improve the geotechnical properties of waste particularly the waste dump sites for road reclamation. Most commonly available and used stabilizing material is Flyash and is very important in the reclamation of Dumped sites. Flyash is a pulverized product from thermal power plants generated by the burning of coal. Indian Power plants burn about 500 million tons of coal per year and produces 200 million tonnes of fly ash at present, which shall grow by 900 mtpa (coal) and 350 mtpa (fly ash) by 2020. Most of the fly ash presently produced by electric utilities and industry is land filled or stored in disposal ponds. The production of Fly ash is expected to increase to about 200 MT per year by the year 2020. This would require about 4000 ha of land for the construction of ash ponds. Generally one acre of land is required per megawatt of power generation. Continuous studies have been carried out in India towards management of fly ash (FA), disposal and utilization. Fly ash could be a cost effective substitute for Portland cement in some markets. In addition, fly ash could be recognized as an environmentally friendly product, because it is a by- product and has low embodied energy. According to the American Coal Ash Association (ACAA), the largest utilization application of coal combustion fly ash is in concrete, concrete products and grout. But Fly ash has also been used recently for paving roads, and as embankment and mine fills. There are mainly two types of fly ash. Class F are generally low-calcium fly ashes with carbon contents less than 5% but sometimes as high as 10%.Class C fly ash has a higher percentage of calcium oxide and is more commonly used for structural concrete. Class C fly ash normally is composed of high-calcium fly ashes with carbon content less than 2%. Though Fly ash has been used in the above mentioned areas, its utilization in the field of stabilization of dumped wastes is not explored. Requirement for Road Reclamation Almost all of road network in India consists of flexible pavements. The design of flexible pavement is generally designed using California Bearing Ratio (CBR).
  3. 3. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 219 Fig. 1.A Typical cross section of a flexible pavement The performance of a pavement structure is related to the strength of underlying sub grade layers. Fly ash is used to stabilize soils and is used in different layer of flexible pavements. Fly ash compacted at optimum moisture content for a given compactive effort will have dry density at its maximum and consequently the maximum shear strength. Strength in the form CBR values forms an important basis for construction of many type of road construction. Typical layers of a conventional flexible pavement includes seal coat, surface course, tack coat, binder course, prime coat, base course, sub-base course, compacted sub-grade, and natural sub-grade (Fig. 1). For flexible pavement, as per IRC 37:2001, design sub grade CBR values ranges from 2% to 10% and design traffic ranges from 1 msa to 150 msa for an average annual pavement temperature of 35 degree centigrade. From the knowledge of several information and records of the pavement thickness and the values of C.B.R and its suitability for the expected traffic volume, the correct thickness can be designed (Table 1). Thus from this table it is found that CBR of 4 to 7% can used as soil sub grades. Table.1 Typical design CBR values for pavements Layer Design CBR (%) Thickness Bituminous Surfacing -- 8 Well graded gravel 95 13 Poorly graded gravel 20 19 Compacted Soil Subgrade 7 15 Soil Subgrade 4 -- LITERATURE REVIEW Stabilization refers to those techniques that reduce the hazard potential of a waste by converting the contaminants into their least soluble, mobile, or toxic form. Significant contributions have been done in the field of stabilization of contaminated soil using cement, fly ash, etc. (Malviya and Chaudhary, 2006; Kogbara et al. 2003). But due to increasing cost of cement, it is not encouraged to be utilized in such applications. Hence industrial waste materials are being promoted which not only reduces disposal problems but will be economical also.
  4. 4. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 220 Depending upon the specific chemical properties cementitious based materials have been used to treat soils/sludge contaminated with semi volatile organic contaminants. But studies related to the stabilization of MSW are not known. Bookter and. Ham (1982) has discussed about a method for the analysis of refuse stability has been developed and tested by analyzing refuse obtained directly from test lysimeters and actual landfills across the United States. Results obtained from the actual landfill situations are compared to those obtained from the test lysimeters of known refuse age in order to determine the degree of refuse stability in each landfill in relation to depth and location. Also, the results obtained from landfills of different geographical locations, different climatic situations, and different configurations are compared. Stabilization treatment can be done in different processes such as sorption processes, organic processes, Processes that use: (pozzolana, fly ash, lime and Portland cement), Macro-encapsulation, Micro-encapsulation). Hence in this paper the strength of the dumped waste and the CBR values after stabilization with fly ash are studied. WASTE SAMPLECOLLECTION AND TESTING METHODOLOGY Illegal Dumping of municipal solid waste (dumped waste) Illegal dumping of MSW is found next to Mavallipura landfill site area. This waste was brought in by the municipal and contract Lorries before the landfill was in operation. Fig. 2.Illegal dumping of municipal solid waste (Dumped waste) This waste includes newspaper, junk mail, today’s meal scraps, pieces of bread, roti, waste rice, raked leaves, dust grass clippings, broken furniture, abandoned materials, animal manure, sewage sludge, industrial refuse or street sweepings etc. and this waste was dumped in the open site, for the past 10 years in the form of a heap (of approximately 2.5m wide and 2m height). The waste was found mixed with the local soil around due to many reasons such as wind, disturbance by animals, etc. From this heap sufficient quantity of Dumped waste is collected and kept in closed bags and carried to the laboratory for testing.
  5. 5. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 221 Fly ash characteristics The Fly ash that has been used in this present study was collected from the Raichur Thermal Power plant which is in Raichur district of Karnataka state, India. The properties of Fly ash are mentioned below in Table 2. Table 2: Physical properties of Fly ash Properties Fly ash Colour Ash colour Specific gravity 2.01 Liquid limit (%) 32 Plastic limit (%) Non-Plastic Plasticity index (%) Non-Plastic OMC (%) 22% MDD (kN/m3 ) 12.46 TESTING METHODOLOGY Direct shear In many geotechnical engineering problems the value of the angle of internal friction and cohesion of the soil involved are required for the design. Direct shear test is used to predict these parameters quickly. The direct shear device is used to determine failure envelopes for soils. Sample preparation: The mass (M) of the wet sample (Dumped waste) at the required moisture content (w) to give the desired density (d) shall be calculated. A batch of sample thoroughly by mixed with 20% fly ash and water to give the required water content. Pour the weighed amount of sample in the direct shear mould and kept it for 7 days curing. After curing the sample the testing was done on until the specimen fails or at arrival of shear displacement of approximately 20 percent of the specimen length. Three tests are conducted at different normal loads. Tests were performed in accordance with IS: 2720 (Part 13):1986. California Bearing Ratio (CBR) California Bearing Ratio (CBR) test is a compressive nature penetration test. This test is an empirical test first developed in California, USA, for estimating the bearing value of highway sub-bases and sub grades. The test is specifically used to determine the mechanical strength as well as the potential strength of road sub grades and base courses materials including the recycled material generally used for road and airfield pavements. CBR value is a percentage comparison with the standard crushed rock from California and thus this test is a comparison test. The CBR test was conducted as according to IS: 2720 Part 16 (1997). Sample Preparation: The mass (M) of the wet sample (Dumped waste) at the required moisture content (w) to give the desired density (d) shall be calculated. A batch of sample is thoroughly by mixed with 20% fly ash and water to give the required water content. Then mould is fixed on the base plate. Place the filter paper inside. Pour the weighed amount of sample in the mould. Sample is tamped by the steel rod during the process of pouring and makes the top surface
  6. 6. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 222 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 VolumetricStrain(%) Shear Strain (%) Norma stress:50kPa Normalstress:100kPa Normalstress:150kPa 0.00 20.00 40.00 60.00 80.00 100.00 120.00 0.00 2.00 4.00 6.00 8.00 10.00 12.00 ShearStress(kPa) Shear Strain (%) Normal Stress=50kPa Normal Stress=100Kpa Normal Stress=150kPa roughly level. Then a filter paper was placed on the top of the sample and spacer disc was inserted. Mould has to be kept for 7 days curing. After curing, mould is kept in the testing machine with the base plate in position and the top surface exposed. Plunger shall be kept under a load of about 4kg so that full contact is ensured between the surface of the specimen and the plunger. Stress and strain dial gauges are set to initial zero-reading. Load is applied to the penetration plunger at the rate of penetration equal to 1.25mm per minute. The maximum load and penetration is recorded for a penetration of less than 12.5mm. California Bearing Ratio test was carried out as per IS: 2720 (Part 16):1986 procedure. RESULTS AND DISCUSSION Strength of Dumped waste with 20% flyash by Direct shear tests Fig 4 shows the typical shear strain versus shear stress response under different normal stresses for Dumped waste with 20% fly ash. Normal stress versus shear stress at 10% deformation was plotted and the shear strength parameters were calculated based on the Mohr-Coulomb failure criteria. Based on the analysis of the data, friction angle is 44°and no cohesion. A summary of the dumped waste with 20% fly ash results is presented in Table 3. Fig. 3. Shear stress vs. shear strain for Dumped waste with 20% fly ash Fig. 4.Volumetric strain vs. Shear strain for Dumped waste with 20% fly ash
  7. 7. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 223 Fig.5 shows the volumetric strain versus shear strain for Dumped waste with 20% fly ash mix. From this graph we can observe initially sample get compressed and then sample starts swelling (dilatation) for normal stress of 50 kPa hence dilatancy angle found to be 26.35° for 100kPa and 150kPa dilatation was not observed. Table 3: Direct shear test results for Dumped waste with 20% fly ash mix Normal stress (kPa) Peak shear stress (kPa) Φ (Degrees) 50 32.9 44100 73.67 150 108.80 CBR Values of Dumped waste after stabilization with Fly Ash Table.4 shows the comparison results of CBR test for waste without fly ash and 20% fly ash.From fig 6 & 7 show the load versus penetration for Dumped waste without Flyash and with 20% Fly ash. The CBR value of 5mm penetration is found to be 1.2%. Fig. 5. Load vs. Penetration for Dumped waste without fly ash Fig. 6. Load vs. Penetration for Dumped waste with 20 % fly ash
  8. 8. National Conference on Beneficial Use of Fly Ash in Construction industry & Agriculture-May 23-24, 2014. 224 Table 4: Comparison of CBR test results for Dumped waste Dumped waste Sample CBR value of 5mm penetration Waste +20% Flyash 1.2 Without stabilization 0.6 CONCLUSION Based on the tests conducted on waste samples collected from dump site the following typical values are obtained:  It was found that addition of 20% of Fly ash improves the shear strength particularly due to increase in coefficient internal friction angle without increasing cohesion intercept.  The strength is still not sufficient and there is need to use higher amount of fly ash to effectively stabilize the dumped waste.  CBR value of the stabilized waste dump is 1.2 % as against CBR of subgrade soil of 4%. With higher amounts of fly ash the waste dumps are promising for construction of proper pavements. REFERENCE:  Bookter, T.J., and Ham, R.K., (1982). “Stabilization of solid waste in landfills,” Journal of Environmental Engineering, vol.108, No.6, pp 1089–1100.  Kogbara, Reginald B., Abir Al-Tabbaa, Yaolin Yi, and Julia A. Stegemann. "Cement–fly ash stabilisation/solidification of contaminated soil: Performance properties and initiation of operating envelopes." Applied Geochemistry 33 (2013): 64-75.  IS: 2720 (Part 13)–1997. “Methods of test for soils,”Direct shear test. Bureau of Indian Standards.  IS: 2720 (Part 16)-1997. “Methods of test for soils,” California Bearing Ratio Test of Soils. Bureau of Indian Standards.  Malviya, Rachana, and RubinaChaudhary. "Factors affecting hazardous waste solidification/stabilization: a review." Journal of Hazardous Materials 137, no. 1 (2006): 267-276.  Naveen.B.P., Sivapullaiah.P.V.,Sitharam.T.G., " Disposal options for solid waste of Bangalore city based on its characteristics", IJEWM, Vol.12,No.1,2013,pp77-88.  Naveen.B.P. Sitharam.T.G., Sivapullaiah.P.V. “Evaluating the Dynamic Characteristics of Municipal Solid Waste for Geotechnical Purpose”, Current Advances in Civil Engineering, Vol.2, No.1, Jan.2014, pp.28-34.

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