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GJESR RESEARCH PAPER VOL. 1 [ISSUE 10] NOVEMBER, 2014
ISSN:- 2349–283X
GEO-FIBER REINFORCED FLYASH FOR GROUND IMPROVEMENT 1Ravi
Mishra Post Graduate Student Department of Civil Engineering, Madan Mohan Malviya University of Technology, Gorakhpur, India Email: ravi12mishra@gmail.com
2Dr.S.M
Ali Jawaid Associate Professor Department of Civil Engineering, Madan Mohan Malviya University of Technology, Gorakhpur, India Email: smaj@rediffmail.com
ABSTRACT: This paper illustrates the possibility of utilization of the fly ash generated from the coal/lignite based thermal power plants through ground improvement technique, leading to an effective waste management. In this study samples were prepared by mixing different percentage of fly ash with different percentage of soil, with an aim to compare strength gain with geo-fiber. Fly-ash mixed with highly compressible soil and reinforced with geo-fiber may find potential applications in road and embankment constructions with due regards for its strength characteristics, durability, longevity and environmental safety. KEYWORDS: Generation; Utilization; Environmental safety 1. INTRODUCTION Fly ash closely resembles volcanic ashes used in production of the earliest known hydraulic cements about 2,300 years ago. Those cements were made near the small Italian town of Pozzuoli – which later gave its name to the term pozzolan. A pozzolan is a siliceous/aluminous material that, when mixed with lime and water, forms a cementations compound. The difference between fly ash and portland cement becomes apparent under a microscope. Fly ash particles are almost totally spherical in shape, allowing them to flow and blend freely in mixtures. That capability is one of the properties making fly ash a desirable admixture for concrete. The aim of the work is to stabilize the fly ash obtained from thermal power plant by mixing it with soil and geo-fiber, which can subsequently be utilized for various geotechnical and highway engineering applications such as filling of embankments, construction of highways, replacement of poor subgrade soil etc.
the benchmark for determining the quality of compaction. The dry density of fill is of primary importance, as it is the major parameter of strength and compressibility of the fills. 2. Materials i.
Soil
ii.
Fly Ash
iii.
Geofiber
2.1 Soil The soil sample which was collected from Ravindra Nagar (Dhoos) Kushinagar. The engineering properties, proctor’s compaction test and grain size distribution curve of the soil is given in Table 1 and, Fig 1, Fig 2 respectively.
The performance of stabilized mixes depends upon the compaction or densification of the fill, proper compaction is therefore, critical to the performance of fly ash, fly ash-soil and fly ashsoil-geo-fiber fills. The maximum dry density (MDD) and optimum moisture content (OMC) obtained by Proctor compaction test becomes
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Table 1 Engineering Properties of Soil
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GJESR RESEARCH PAPER VOL. 1 [ISSUE 10] NOVEMBER, 2014
ISSN:- 2349–283X
Fig. 1 Result of Proctor’s Compaction Test on Soil
Fig 2 Grain Size Distribution Curve For Soil
2.2 FLY ASH The fly ash used in the study was brought from Tanda Thermal Power Station situated at Ambedkar Nagar in Uttar Pradesh, which was
available free of cost. Fly Ash is classified as silt of low compressibility. Fly Ash from Electrostatic Precipitator (ESP) is continuously removed to buffer hopers located near ESP by means of vacuum pumps. From buffer hoppers,
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GJESR RESEARCH PAPER VOL. 1 [ISSUE 10] NOVEMBER, 2014 dry fly ash is conveyed to storage silos, from there it can be unloaded dry to pneumatic tank trucks or conditioned with water by hydro mix dust conditioners for discharge to open bed trucks, Ash to be stored is removed by belt conveyers to ash storage area. Bottom ash is continuously collected in wet hoppers, ground to sand size and periodically transferred to one of six hydro bins for decanting. For the present investigation, dry fly ash from hopper is collected in polythene bags. Fly Ash can be collected into different categories such as dry fly ash, bottom fly ah, conditioned fly ash. Dry fly ash can be collected from different rows of electrostatic precipitators. Bottom ash is collected from bottom of the boiler. Conditioned fly ash is also available in ash mound for use in landfills and ash building products. Two classes of fly Ash are defined by ASTM C618: Class F Fly Ash and Class C Fly Ash. The main difference between these classes is the amount of calcium, silica, alumina, and iron content in the ash. The chemical property of the fly ash is highly influenced by the chemical content of the coal burned. (i.e., anthracite, bituminous, lignite). The free lime content of fly ash contribute to self- hardening, fraction of lime, present as free lime in the form of calcium oxide or calcium hydroxide, controls selfhardening characteristics of fly ashes.
ISSN:- 2349–283X
Table 2 Engineering Properties of Fly Ash (Type Class F)
Fig 3 Result of Proctor’s Compaction Test on Fly Ash
The engineering properties of flyash are given in table 2.
Fig 4 Grain Size Distribution of Fly ash
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GJESR RESEARCH PAPER VOL. 1 [ISSUE 10] NOVEMBER, 2014
ISSN:- 2349–283X
Table 4 Elemental Composition of materials in Flyash (Source NTPC Tanda)
polypropylene as for as strength, chemical innertness and durability is concerned. Steel fibers are prone to rust and acids. Glass fibers although costly but can bear temperature up to 1500 c. asbestos, glass, carbon fibers have been found to be resistant to alkaloids and other chemical attack. Polypropylene fibers used in the study were cut from locally available continues fibers. The physical and engineering properties of the fibers are shown in Table 5.
3. GEOFIBER The various types of synthetic fiber that may be used for strengthening the soil or fly ash are polypropylene, nylon, plastic, glass asbestos etc. These are preferred over natural fibers because of their higher strength and resistance. Polypropylene fiber are resistant to acidic, alkaline and chemical. These fibers have high tensile strength, resistance to sea water and melting point i.e. 850 C. poly amide has inherent defect of getting affected by the ultraviolet rays from sun but when the fibers are enbeded in soil are not affected by solar radiation. Synthetic fibers are also show a great biological resistance. The important properties of polypropylene are its versatility, excellent chemical resistance, low density, high melting point and moderate cost. All these make it an important fiber in construction applications. So far as fiber structure of polypropylene is concerned, it is composed of crystalline and non- crystalline regions. Fiber spinning and rawing may cause the orientation of both crystalline and amorphous regions. The degree of crystallinity of polypropylene fiber is generally between 50-60%, depending on processing condition. Crystallization occurs between glass transition temperature and equilibrium melting point. Polypropylene fibers are being used extensively throughout the USA and Canada in all types of concrete construction, and they have proven to be an effective method of controlling shrinkage cracks in concrete. Polypropylene fibers were tested in eight different media (distilled water, iron, bacteria culture, seawater and soil) for seventeen months and found no degradation. Result showed that there was no change in tensile strength. Plastic fiber shows loss in strength with temperature. Nylon is comparable with
Table 5 Physical and Engineering Properties of Geo-fiber.
4. Mix Preparations for Stabilization of Fly Ash The fly ash is mixed with highly compressible soil and geo-fiber in different proportion, thereafter, best mix has been found on the basis of Optimum Moisture content and California bearing ratio test and then to the best mix has been selected to improve the properties of soil. The following proportions of mix were prepared and the Geotechnical properties of mix proportion are shown in Table no. 6.
On the basis of past research (Sharif, 2012) we found that 2% geofiber mixing gives the best result in soil stabilization therefore we mix 2%
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GJESR RESEARCH PAPER VOL. 1 [ISSUE 10] NOVEMBER, 2014
ISSN:- 2349–283X
geofiber in different percentage of soil and flyash. 5 RESULTS AND DISCUSSION 5.1 Stabilization of Fly Ash Different percentage at which Fly Ash was mixed with soil and its OMC and CBR is given in Table 7. From the table and graph it is clear that strength of the mixture is maximum when 38% Fly ash and 2% is Geofiber added to the 60 %soil. On the basis of past research (Sharif, 2012) we found that 2% geofiber mixing gives the best result in soil stabilization therefore we mix 2% geofiber in different percentage of soil and flyash.
Fig 6 Result of Fly-ash and OMC As shown figure 6, it is observed that the Optimum moisture Content of the Fly ash increases on increasing the percentage of flyash in the mixture of soil and geofiber, because surface area of the sample increases.
Fig.7 Result of Fly-ash and CBR
Fig 5 Result of Fly-ash and MDD As evident from fig 5, on increase the percentage of fly ash in the mixture of soil and geofiber, leads to decreases in dry density because fly ash is light weight compared to soil and the particles present in the flyash are finer than soil.
Fig.8 Variation 0f OMC, MDD and CBR with different fly ash content.
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GJESR RESEARCH PAPER VOL. 1 [ISSUE 10] NOVEMBER, 2014 In order to compare the result obtained when 38% flyash, 60% soil and 2% geofiber is mixed maximum CBR of 5.24% is found and after this when the percentage of flyash is increased the CBR value decreases. 4. Conclusions With the aim to utilize the industrial waste such as fly ash from NTPC Tanda power plant for geo technical and highway applications in an environmentally safe manner, detailed investigations were carried out. Based on this study, the following conclusions are drawn. The dry density of Fly ash and Soil mix is less than that of virgin soil because Fly ash is light weight material as compared with soil. In order to achieve good quality structural fills, the MDD values obtained from standard proctor test may be adopted as a benchmark value. The CBR value of compacted fly ash was found 1.8% which is low and undesirable for construction. The bearing strengths of fly ash were increased to 5.24% on addition of fly ash and geo fiber to it. The optimum percentage of the mix is found as 60% soil + 38% fly ash + 2% geo-fiber based on strength criteria. Addition of small percentage of Geo-fiber to Fly ash enhances the bearing capacity of ashes. The mix containing 38%FA+60%Soil+2%GF has good bearing strength characteristics 5. Refrences 1. Beeghly, J. H. (2003). “Recent experiences with lime-fly ash stabilization of pavement subgrade soils, base, and recycled asphalt.” Proceedings of International Ash Utilization Symposium, 2003, Lexington, Ky., 0-967 4971–5–9, 435–452. 2. Bera, A. K., Ghosh, A., and Ghosh, A. (2007). “Compaction characteristics of pond ash.” Journal of Materials in Civil Engineering, 19(4), 349–357.
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3. Brooks, C. S. (1993). ‘‘Recovery of nonferrous metals from finishing industry wastes.” Seventh Symposium of Separation Science Technology for Energy Applications, Separation Science Technology, Knoxville, TN, USA, 28(1–3), 579–593 4. Bell F.G. (1996). Lime stabilization of clay minerals and soils. Engineering Geology, 42, 223–237. 5. Biswas, A., Gandhi, B.K., Singh, S.N. and Seshadri, V. (2000): “Characteristics of coal ash and their role in hydraulic design of ash disposal pipelines”, Indian Journal of Engineering and Material Science, Vol.7, pp.1-7. 6. Gray D.H. & Lin Y.K. (1972). Engineering Properties of Compacted Fly Ash. Jl. of SMFE, Proc. ASCE, 98, 361-380. 7. Hakari, Udayashankar D. (2010) “Geotechnical Characterstics of HubliDharwad Black Cotton Soils Mixed With Fly Ash: An Experimental Evalution”, Indian Geotechncal Confrence December 16-18, 2010. IGS Mumbai Chapter & IIT Bombay. 8. Kaniraj, S. R., and Havanagi, V. G. (1996). “Compressive strength of cement stabilized fly ash–soil mixture.” Cement Concrete Research, 29, 673–677. 9. Kaniraj, S. R., and Havanagi, V. G. (1999). “Geotechnical characteristics of fly ash-soil mixtures.” Geotechnical Engineering, 30 (2), 129–147. 10. Kaushik, S. K., and Kumar, A. (1998). “Fly ash–silica fumes high performance concrete–a state of the art.” Proceeding of Workshop on Utilization of Fly ash. ICI, Roorkee, 15–47. 11. Shah, S. S., and Ahmad, M. S. (2008). “Stabilization of heavy metal containing waste using Fly ash and cement.” Indian Geotechnical Journal, 38(1), 89-100. 12. Senadheera, S. P., Jayawickrama, P. W., Ashek, S., and Rena, M. (1998). “Crushed hydrated fly ash as a construction aggregate.” ASCE Geotechnical Special Publication, 79, 230.
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GJESR RESEARCH PAPER VOL. 1 [ISSUE 10] NOVEMBER, 2014 13. Sharif (2012). “Flyash mixed with waste sludge and reinforced with geofiber ” A.M.U.,Aligarh. 14. Sinha, U.N., Karthigeyan, S. and Sinha, A.K. (2000). “Shear strength characteristics of compacted fly ash used as geo material for the construction of embankment.” 2nd International conference on Fly ash Disposal and Utilization. CBIP, New Delhi, 71-76.
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