IGC. 50 th. 50 th INDIAN GEOTECHNICAL CONFERENCE IMPROVEMENT IN LOAD BEARING CHARACTERISTICS OF RED MUD REINFORCED WITH SINGLE GEOGRID LAYER

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1 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India IMPROVEMENT IN LOAD BEARING CHARACTERISTICS OF RED MUD REINFORCED WITH SINGLE GEOGRID LAYER A.K. Choudhary 1, T.K. Sahoo 2, J. N. Jha 3, S.K. Shukla 4 ABSTRACT In developing countries like India where rate of industrialization is rapid, wastes coming out of various industries are not only creating serious environmental problems but also occupying vast tracts of scarce land for their disposal. On one hand management of wastes is posing big challenge for developing and developed countries all over the world and on the other hand conventional materials are becoming scarce and costly for any major engineering and geotechnical projects thus incurring a huge cost. Therefore a need to search for an economically viable substitute to these conventional materials is very much required. Bulk utilization of these industrial wastes is possible through geotechnical applications only eg. road/rail embankment, back-fill material and sub-base/base material for road pavements. Geotechnical characterization of these industrial wastes is likely to provide economically viable and environmentfriendly solutions for their gainful utilization and thereby solving the problem of their disposal to a great extent. Reinforced earth concept, a composite material formed by the combination of soil and reinforcement, may be useful in utilizing these industrial wastes as a substitute for conventional soil in embankments, fill materials, base and subbase and subgrade materials. The paper presents the results of a series of CBR tests carried out with red mud; an industrial waste of the aluminum industries. CBR tests were carried out with unreinforced red mud specimen as well as reinforced specimens with single layer of geogrid placed at varying embedment ratio and under soaked and unsoaked condition. The study reveals that reinforcing red mud results in appreciable increase in CBR and subgrade modulus value but there exists an optimum value of embedment depth at which the benefit of reinforcement placement are optimum. The proposed materials can be used effectively in embankment and road construction leading to a safe and economical disposal of these waste materials. 1 A.K. Choudhary, Civil Engineering, Associate Professor, Jamshedpur, India, drakchoudharycivil@gmail.com 2 T.K. Sahoo, Civil Engineering, Post Graduate student, Jamshedpur, India, tanmaya162@gmail.com 3 J. N. Jha, Civil Engineering, Professor, Ludhiana, India, jagadanand@gmail.com 4 S.K. Shukla, Civil Engineering, Associate Professor & Program Leader, Perth, Australia, s.shukla@ecu.edu.au

2 A. K. Choudhary, T.K. Sahoo, J. Jha, S. Shukla Keywords: Red mud, CBR, Geogrid, CBRI, PLR, Subgrade modulus.

3 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India IMPROVEMENT IN LOAD BEARING CHARACTERISTICS OF RED MUD REINFORCED WITH SINGLE GEOGRID LAYER A.K. Choudhary, Associate professor, N.I.T. Jamshedpur, India, T.K. Sahoo, Post graduate student, N.I.T. Jamshedpur, India, J. N. Jha, Professor, G.N.D.E.C. Ludhiana, India, S.K. Shukla, Associate professor & Program Leader, E.C.U., Perth, Australia, ABSTRACT: The paper presents the results of a series of CBR tests carried out with red mud; which is an industrial waste of the aluminum industries. CBR tests were carried out with unreinforced red mud specimen as well as reinforced specimens with single layer of geogrid placed at varying embedment ratios and under soaked and unsoaked condition. The study reveals that reinforcing the red mud results in appreciable increase in CBR and subgrade modulus but there exists an optimum value of embedment depth at which the benefits of reinforcement placement are optimum. The proposed materials can be used effectively in embankment and road construction leading to a safe and economical disposal of these waste materials. INTRODUCTION In developing countries like India where the rate of industrialization is rapid, wastes coming out of various industries are not only creating serious environmental problems but also occupying vast tracts of scarce land for their disposal. On one hand the management of wastes is posing a big challenge for developing and developed countries worldwide and on the other hand, the conventional materials are becoming scarce and costly for any major engineering and geotechnical projects thus incurring a huge cost. Therefore a need to search for an economically viable substitute to these conventional materials is very much required. Bulk utilization of these industrial wastes is possible through geotechnical applications only e.g. road/rail embankment, back-fill material and subbase/base material for road pavements [1,2]. Geotechnical characterization of these industrial wastes is likely to provide economically viable and environment-friendly solutions for their gainful utilization and thereby solving the problem of their disposal to a great extent. For sustainable economical and environmental protection measures, researches have been trying to find ways and means for utilization of these wastes as a substitute for natural earth especially in pavement construction. Reinforced earth, a composite material formed by the combination of soil and reinforcement, may be useful in utilizing these industrial wastes as a substitute for conventional soil in embankments, fill materials and base and sub base and subgrade materials [2].

4 A. K. Choudhary, T.K. Sahoo, J. Jha, S. Shukla This paper presents the results of an experimental study carried out with red mud, an industrial waste generated from alumina industries. It is a byproduct produced from caustic leaching of bauxite to form alumina by the Bayer process [3]. About 0.8 to 1.0 ton of red mud is generated during the production of one ton of alumina [4]. Disposal of red mud has been a great environmental concern for the alumina industries because of its high alkalinity. Recently; attempts are being made to find alternate uses of red mud for civil engineering purposes such as production of cement [5,6] brick [7,8], soil stabilizer [3] and pavement materials [9]. Geotechnical properties of red mud are similar to that of sand and clay [10]. Its frictional properties are similar to natural sand and compression characteristics are similar to clay and therefore; the red mud can be used in various geotechnical applications as a substitute for soil. This paper presents the strength and deformation characteristics of red mud with and without reinforcing elements. A series of CBR tests with varying embedment ratio of a single geogrid layer were conducted to determine the value of the optimum embedment ratio to get maximum reinforcement benefit.. MATERIALS For the experimental investigation the red mud was collected from Hindustan Aluminum Corporation Limited (HINDALCO), Muri, Jharkhand. Fig-1 shows the particle size distribution curve of red mud. Geogrid was obtained from local market. Table-1 and Table-2 shows physical properties of red mud and geogrid respectively. Fig-1 Particle size distribution curve of red mud Table-1 Properties of Red mud Parameter Value Particle size Distribution : Gravel size (%) 3.60 Sand size (%) Silt and Clay size (%) Specific gravity 2.80 Liquid limit (%) 43.0 Plastic limit (%) 32.0 Plasticity Index (%) 11.0 Maximum dry unit weight (kn/m 3 ) Optimum moisture content (%) IS Classification MI AASHTO Classification A-7-5 (9)

5 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India Table-2 Properties of geogrid Parameter Geogrid Material Polypropylene Aperture size (mm) 2.5 Thickness (mm) 0.5 Average breaking strength 5.0 (kn/m) EXPERIMENTAL METHOD Unsoaked and soaked CBR tests were performed on both unreinforced and reinforced red mud specimens compacted at their maximum dry unit weight and optimum moisture content corresponding to I.S light compaction. Amount of oven dried red mud and water required to fill the CBR mould before and after placing the geogrid was calculated separately. For the geogrid reinforced red mud specimen, geogrids were cut into circular disc of 145 mm diameter (internal diameter of CBR mould = 150 mm) so that it easily gets fit inside the specimen. For reinforced red mud specimen the weights of dry red mud and water needed to fill the specimen up to the embedment depth were calculated from maximum dry unit weight and optimum moisture content value obtained from light compaction test. Water and red mud were mixed thoroughly to achieve a uniform consistency. Red mud required to fill the portion below the reinforcement layer was compacted in the CBR mould by dynamic compaction to achieve required unit weight. After compaction, the surface was leveled and geogrid was placed over it. Then remaining red mud and water mixture were placed over the geogrid in layers and compacted to achieve required unit weight. Top surface of specimen was leveled and a layer of filter paper and perforated metal disc were placed over it. An annular surcharge weight of 25 N was placed over the metal disc and the whole assembly transferred to a soaking tank. The whole red mud-geogrid assembly is shown in Fig-2. The specimen was allowed for soaking for a period of 96 h. Then whole mould assembly was transferred to strain controlled loading frame to perform CBR test. Initially a seating load of 40 N was applied. Proving ring and deformation dial gauges readings were set to zero. Then load was applied through a loading plunger at a constant strain rate of 1.2 mm/min. Loads corresponding to different penetration were noted down up to final penetration of 12.5 mm. This procedure was repeated for different geogrid embedment ratios (z/d) of 0.25, 0.5, 0.75, 1.0, The embedment ratio is defined as the ratio of embedment depth of geogrid (z) to loading plunger diameter (d). For unsoaked CBR test, the specimen was not allowed for soaking and directly transferred to loading platform after compacting.

6 Load (kn) Load (kn) A. K. Choudhary, T.K. Sahoo, J. Jha, S. Shukla No geogrid z/d = 0.25 z/d = 0.50 z/d = 0.75 z/d = 1.00 z/d = Penetration (mm) Fig-2 Schematic diagram of reinforced red mud specimen RESULTS AND DISCUSSION The load-penetration curves from unsoaked and soaked CBR tests were compared to know the relative improvement in load bearing behavior of red mud with varying embedment ratios. Fig-3 and Fig-4 compare the load resistance (kn) versus penetration (mm) for unsoaked and soaked CBR conditions respectively. In these figures, it is observed that the red mud provides more resistance at unsoaked condition than soaked condition for a specific penetration. It is also seen that, the reinforced red mud provides more load resistance than the unreinforced one for both soaked and unsoaked conditions. The maximum load penetration resistance is observed at an embedment ratio of 1.0. Fig-3 Load-penetration curve for unsoaked CBR Penetration (mm) No geogrid z/d = 0.25 z/d = 0.50 z/d = 0.75 z/d = 1.00 z/d = 1.50 Fig-4 Load-penetration curve for soaked CBR Iit is also observed that the CBR value at 2.5 mm penetration is higher than 5 mm penetration in all cases of present investigation. Therefore, in the

7 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India present study the CBR value is taken corresponding to 2.5 mm penetration. Fig-4 shows the variation in CBR value with embedment ratio for both unsoaked and soaked conditions. An improvement in CBR value is seen due to geogrid reinforcement. It is observed that CBR value increases with embedment depth of geogrid layer but when embedment depth of geogrid layer is greater than the plunger diameter, CBR value start decreasing. At embedment ratio of 1, the maximum CBR value is obtained for both unsoaked and soaked conditions. red mud to the CBR value of unreinforced red mud. Variation in CBRI value with embedment ratio of reinforcement layer is presented in Fig-5. It is noticed that the improvement achieved for unsoaked and soaked conditions at embedment ratios of 1.0 are 3.7 and 4.0 respectively. Fig-5 Variation in CBRI value with embedment ratio Fig-4 Variation in CBR value with embedment ratio Relative improvement in CBR value of reinforced red mud is expressed by a non-dimensional parameter as the California Bearing Ratio Index (CBRI). It is the ratio of CBR value of reinforced Improvement in load-carrying capacity due to inclusion of a geogrid reinforcement in red mud can be expressed by a term as, the Piston Load Ratio (PLR). It is the ratio of plunger load at 12.5 mm penetration for reinforced red mud to plunger load at the same penetration for unreinforced specimen [11]. The variation in PLR value with embedment ratio for unsoaked and soaked condition is shown in Fig- 6. It is observed that when the geogrid embedment

8 A. K. Choudhary, T.K. Sahoo, J. Jha, S. Shukla depth (z) is equal to plunger diameter (d) the PLR value is maximum for both unsoaked and soaked conditions. The maximum PLR value obtained at z/d = 1.0 for unsoaked condition is 3.14 and for soaked condition is 2.1. Fig-7 Variation in subgrade modulus with z/d Fig-6 Variation in PLR with z/d Strength of red mud can be expressed by the subgrade modulus. It is the ratio of stress generated by plunger load at CBR value to the corresponding penetration. Fig-7 shows the variation in subgrade modulus value with embedment ratio for both unsoaked and soaked conditions. It is observed that with an increase in embedment ratio, the subgrade modulus value increases and reaches a peak value of kn/m 3 for unsoaked condition and kn/m 3 for the soaked condition at an embedment ratio of 1.0. Fig-8 shows the variation in percentage reduction in total pavement thickness with embedment ratio. The percentage reduction in total pavement thickness is calculated with respect to unreiforced red mud using the design charts given in IRC-37 (2001) [12] for a traffic loading of 5 msa. It is observed that at the optimum geogrid depth (ie. z/d = 1) pavement thickness is reduced approximately by 37% with respect to unreinforced one.

9 50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India Fig-8 Variation in Percentage reduction in pavement thickness with z/d The geogrid reinforcement transmits the vertical load in lateral direction by mobilizing friction between geogrid-red mud interfaces. The friction mobilization depends upon the vertical load, friction angle between geogrid and red mud surface and confinement of geogrid. The effect of embedment depth on load carrying capacity of geogrid is explained below. When the embedment depth of geogrid is low (z<d), the stress due to loading plunger on geogrid is high but due to less overburden pressure geogrid does not get sufficient confinement, hence the friction required to transmit vertical load in lateral direction is not sufficient. Therefore at z<d the improvement in load carrying capacity is not high. When the embedment depth is high (z>d) the overburden pressure on the geogrid layer is high, hence it gets sufficient confinement but stress due to the plunger load on geogrid is very low for sufficient mobilization of friction. At the optimum embedment depth (ie z/d =1), the geogrid gets sufficient vertical stress and confinement so the load bearing capacity is maximum. CONCLUSION From the present experimental investigations as presented above, the following conclusions can be drawn. 1. An insertion of geogrid reinforcement to red mud improves its load-bearing capacity. 2. The strength of geogrid reinforced red mud depends on the embedment ratio of reinforcement. The maximum strength is achieved at an embedment ratio of The CBR, CBRI, PLR and subgrade modulus values of reinforced red mud increases with an increase in embedment ratio up to 1.0 and thereafter decreases. REFERENCES [1] J. N. Jha, A. K. Choudhary, K. S. Gill, and S.K. Shukla., Behaviour of Plastic Waste Fibre-Reinforced Industrial Wastes in Pavement Applications, Int. J. Geotech. Eng., vol. 8, no. 3, pp , [2] A. K. Choudhary, J. N. Jha, and K. S. Gill, A study on CBR behavior of waste plastic strip reinforced soil, Emirates J. Eng. Res., vol. 15, pp , 2010.

10 A. K. Choudhary, T.K. Sahoo, J. Jha, S. Shukla [3] E. Kalkan, Utilization of red mud as a stabilization material for the preparation of clay liners, Eng. Geol., vol. 87, no. 3, pp , [12] Indian Roads Congress. "Guidelines for the design of flexible pavements." Indian code of practice, IRC 37 (2001). [4] X. Liu and N. Zhang, Waste Management & Research., [5] M. Singh, S. N. Upadhayay, and P. M. Prasad, Preparation of special cements from red mud, Waste Manag., vol. 16, no. 8, pp , [6] P. E. Tsakiridis, S. Agatzini-Leonardou, and P. Oustadakis, Red mud addition in the raw meal for the production of Portland cement clinker, J. Hazard. Mater., vol. 116, no. 1, pp , [7] T. Kavas, Use of boron waste as a fluxing agent in production of red mud brick, Build. Environ., vol. 41(12), pp , [8] J. Yang and B. Xiao, Development of unsintered construction materials from red mud wastes produced in the sintering alumina process., Constr. Build. Mater., vol. 22, no. 12, pp , [9] F. Kehagia, An innovative geotechnical application of bauxite residue, EJGE, vol. 13, pp. 1 10, [10] T. Newson, T. Dyer, C. Adam, and S. Sharp, Effect of Structure on the Geotechnical Properties of Bauxite Residue, J. Geotech. Geoenvironmental Eng., no. February, pp , [11] A.K.Choudhary, K. Gill, J. N. Jha,and S.K. Shukla, Improvement in CBR of the expansive soil subgrades with a single reinforcement layer, in Proceedings of Indian Geotechnical Conference, 2012, pp