Suitability of Natural Fibres in Geotextile Applications

IGC 2009, Guntur, INDIA

SUITABILITY OF NATURAL FIBRES IN GEOTEXTILE APPLICATIONS Mahuya Ghosh Scientist, Geotech Cell, Indian Jute Industries’ Research Association, Kolkata–700088, India. E-mail: [email protected] P.K. Choudhury In-charge, Geotech Cell, Indian Jute Industries’ Research Association, Kolkata–700088, India. E-mail: [email protected] Tapobrata Sanyal Geotech Advisor, Indian Jute Industries’ Research Association & Jute Manufactures Development Council, Kolkata–700016, India. E-mail: [email protected] ABSTRACT: Natural fibres, like jute, coir, sisal, etc. have quite a few inherent properties suited to meet the requirements of different types of geotextiles. Shorter durability of natural geotextiles is a matter of apparent concern of end-users in general, though their eco-compatibility gives them an edge over man-made geotextiles. Availability of jute in abundance, especially in the eastern region of the Indian sub-continent, its spinnability and other features backed by more-than-century old expertise of jute mills in making a variety of fabrics should augur a promising future of Jute Geotextiles (JGT). This paper presents some details regarding application of JGT. Besides, use of other natural geotextiles and related studies finds mention in the paper. Additionally, some new but novel natural fibre- based geotextiles developed to meet typical enduse requirements have also been discussed. 1. INTRODUCTION Man-made geotextiles based on petrochemical derivatives have doubtful eco-compatibility. There are certain associated problems as well. There is slow but sure depletion of the valuable source warranting its controlled use. There is thus unabated rise in prices of the raw material as a result which in turn makes geotextiles expensive. There is therefore a need for search for eco-friendly, renewable, abundantly available and economically viable alternatives. Increasing inclination to use natural geotextiles stems from this necessity. In this paper, the scope of the natural fibres to be used as raw material for geotextiles, applications of different commercial natural products and nature and functional efficacy of some newly developed natural geotextile products have been discussed. 2. NATURAL FIBRES FOR GEOTEXTILES AND THEIR SCOPE VIS-À-VIS SYNTHETIC FIBRES A fibre would be suitable for manufacturing geotextiles when (a) It possesses suitable mechanical properties and in some cases along with good hydraulic properties

(b) It is reasonably resistant to bio-degradation Natural fibres can be of vegetable, animal or mineral origin. Vegetable fibres have greatest potential for use in geotextiles because of their superior mechanical properties. The important vegetable fibres which are either in use or have potential to be used as raw material for geotextiles are jute, coir, sisal, flax, kenaf, abaca, pineapple etc. From Table 1, it is clear that jute has better mechanical properties (desirable for reinforcement application) and more hygroscopic (desirable for drainage application) than the conventional polypropylene and polyester fibres (generally prepared from recycled polymers) used for manufacturing geotextiles. Being more hygroscopic, amount of volume swelling in water for these natural fibres would be also higher than the man-made fibres. This will directly cause reduction in pore size and an increase in thickness of the geotextile filter fabric made out of natural fibres. This thicker and denser filter fabric is expected to function as a more effective filter.

Table 1: Some Related Properties and Characteristics of Different Fibres for Geotextile Applications (after Batra, 1985) Type of fibre Jute Coir Sisal Polyester Polypropylene

Tenacity N/tex 0.3–0.9 0.18 0.37–4.7 0.3–0.8 0.3–0.8

Extension at break (%) 1–1.8 41–45 1.9–4.5 15–55 15–35

Initial modulus N/tex 17–19 4.22 25–26 6–12 2–9

Work of rupture, N/tex 0.005 0.016 0.0043 0.020–0.092 0.082

497

Volume swelling % 44.3 – 39.5 – –

Moisture regain % at 65% RH, 20ºC 12–14 10 11–14 0.4-0.6 < 0.1

Lignin content % 12–14 30 9.9 Nil Nil

Suitability of Natural Fibres in Geotextile Applications

Spinning of coir fibres to prepare uniform and finer count yarn is a very difficult job owing to the very fundamental limitation of the raw material itself. Coir fibres exhibit a wide range of dimensions, varying in length from 50 mm to 300 mm and in diameter between approximately 100 μm and 400 μm. The longer fibres are also thicker. Basically, the population of coir fibres is a heterogeneous mixture of fibres varying widely in mechanical properties such as in bending rigidity and breaking load. Traditionally, this extremely heterogeneous fibre mass is twisted as a bunch and finally a 2-ply yarn structure is formed which is evidently very thick and uneven. Obviously to design suitable woven fabric structures for different applications, initially one has to improve the coir spinning process starting with a segregation of the different component groups of fibres within the coconut husk. In this regard jute fibre spinning technology is far ahead and hence has a definite advantage. Coir fibres differ from jute fibres in another aspect too; jute fibres exhibit moderately high modulus as well as high tenacity and very low extension at break whereas coir fibres behave exactly in the opposite manner, viz. moderately low modulus, low tenacity and very high extension at break. Hence, they can be employed as ideal partners for a blended product (Banerjee, 2004). The growth of micro-organism on natural fibres depends on their chemical composition. To this end, the presence of lignin decreases moisture absorption, since lignin is hydrophobic. In addition, layers of lignin in the inner middle lamella and close to the fibre surface will resist penetration of water into the cellulosic cell wall (Batra, 1985). Hence, the lignin content is supposed to hinder microbial attack by keeping the fibre bulk at low moisture level. In this respect alone, coir fibre with 30% lignin content stands out as extremely resistant followed by jute (about 12%) and leaf fibres (about 10%). Even in contest of lignin-hemicellulose ratio, jute coir and leaf fibres appear to have distinct advantage over the other bast fibres. In terms of the crystallinity of the cellulose content, which also influences the biodegradability (Batra, 1985), no comparative results are available for these fibres although it is quite high for the leaf fibres and low for coir. In some specific geotechnical applications, ambient environment provides a degree of protection to the natural product. For example, in asphalt overlay application, the concerned geotextile would be surrounded by asphlatic environment. The asphalt itself will resist or delay biological degradation (Ghosh, 2006; Banerjee & Ghosh, 2008). Sisal, a leaf fibre, is also available in considerable volume in our country. Oosthuzen & Kruger (1994) reported the successful application of sisal geotextile product for erosion control application in South Africa. Further scientific investigation is needed to assess its efficacy in solving other geotechnical problems and finally to incorporate this fibre in the basket of natural raw materials for different geotextile products.

3. DIFFERENT NATURAL GEOTEXTILE PRODUCTS 3.1 For Erosion Control Application Rickson (2003) reported that woven jute fabrics performed the best among other natural and synthetic erosion control products under numerous experimental conditions, with different rainfall intensities and soil types. In the process of investigating jute’s superiority over others, she identified some extremely important geotextile properties having good correlation with erosion control performance. These are area of the geotextile (% cover), water holding capacity of geotextile, geotextile induced roughness to the flow, weight of geotextile when wet and depth of flow enhanced by the geotextile. 3.1.1 Soil Saver Soil Saver’ is a brand name of open weave Jute Geotextile (JGT) which has been in use in Europe and America since early 1950s control for of surficial soil erosion caused by precipitation, principally in slopes through vegetation (Sanyal, 2004). Each grid (opening) in open mesh woven JGT, like ‘soil-saver’, helps confine detached soil particles within and thus prevent their migration. Simultaneously, the weft yarns of soil-saver act as successive mini-barriers to reduce the velocity of surface run-off. Additionally, jute having high water holding capability can absorb water to about 500 % of its dry weight. No other hard textile fibre can claim to possess this level of capability as reported by Oosthuzen & Kruger, 1994. Hence, JGT, when wet, would create more intimate contact with the soil surface underneath due to increased drapability. Moreover, it has the unique property of forming mulch on biodegradation, keeping a congenial humidity level and curbing extremes of temperature which fosters fast vegetative growth. At present, three types of soil-saver are in common use. Their technical specifications are provided in Table 2. Table 2: Specifications of Soil Saver’s (after Sanyal, 2004) Type/ Properties Areal density (g/m2) at 20 % moisture regain Threads/ dm (MD × CD) Thickness (mm) Fabric Width (m) Open area (%) Strength (kN/m) (MD × CD) Water holding capacity (%) on dry weight Maximum durability (yrs.)

1 292

500

2

3 730

12 × 12 2 1.22 60 10 × 10 400

6.5 × 4.5 4 1.22 50 10 × 7.5 500

7×7 6 1.22 40 12 × 12 500

2

2

2

3.1.2 Bitumen-Coated JGT To achieve enhanced durability of JGT in some specific application of erosion control, like in control of river bank

498

Suitability of Natural Fibres in Geotextile Applications

erosion where the product would be continuously exposed to water, bitumen-coated JGT are employed. Sanyal (2006) have reported the successful field trials of employing bitumen-coated JGT to mitigate river bank erosion at Nayachar Island in the estuary of the river Hoogly, West Bengal and the eastern bank of the river Phulahar in the district of Malda, West Bengal. Rot resistant chemicals have been applied to defer the degradation of the geotextile by about 3-4 years, by which time it is expected that siltation would take place between the boulders laid over the geotextile. JGT can prevent the migration of soil from the bank and it has sufficient permeability to neutralize differential over pressures. Specifications for typical bitumen coated JGT are provided in Table 4.

3.1.4 Sisal Geotextile Oosthuzen & Kruger (1994) have reported successful application of sisal geotextile in the semi-arid region, like South Africa where the bulk of rainfall is in the form of heavy thunder showers. Two types of sisal geotextile (nettings), having areal densities of 300 g/m2 and 1000 g/m2 were employed. The report shows that the sisal fibre compares very favourably with other natural fibres, like jute and coir. Sisal geotextile provides protection against soil erosion for a period of up to two years while at the same time creates suitable micro-climate for the germination and growth of new vegetation. 3.2 Jute Geotextiles for Separation and Filtration Specifications of woven JGTs used for these kinds of applications are provided in Table 4.

3.1.3 Coir Geotextile Mattings In some severe situations, either because of climate or steepness of slope, a longer period of function by the erosion control geotextile is required. Coir-based geotextiles provides both the advantages of bio-degradability and longevity required for slow establishment of vegetative cover. Coir-based geotextiles have been shown to persist, in UK upland conditions, for at least three years and to retain their erosion control functions. Comparative efficacy of coir and jute as vegetative growth facilitator has not been studied in depth. Coir incidentally absorbs water around 150% of its dry weight as compared to jute’s 400% to 500%.

Table 4: Specifications for Typical Woven JGTs (JGT Manual, 2008) Properties Grey Rot Bitumen (untreated) resistant treated Mass/unit area (g/m2) 760 760 1200 Threads/dm (MD × CD) 102 × 39 102 × 39 102 × 39 Width (m) 0.76–2.0 0.76–2.0 0.76–2.0 Thickness (mm) 2 2 2 Strength (kN/m) 20 × 20 20 × 20 21 × 21 (MD × CD) Extension % at break 10 × 10 10 × 10 10 × 10 (MD X CD) AOS (O90) μ 300 300 150 Water permeability at 10 50 50 20 cm water head (l/m2/s) Puncture resistance (N) 380 380 400 Durability (yrs.) Normal 1 2 4

Rao (1995) has reported the successful use of Coir Mattings for the rectification and regeneration of a landslide in the Western Ghat region of Kerala, India. Two varieties of coir mattings, Type A and Type B, were selected for the present field application. The physical properties of these Coir Mattings are presented in Table 3. Table 3: Properties of Coir Geotextile Mattings (after Rao, 1995) Property Areal density (g/m2) Opening size (mm) Number of yarns/m length (a) Machine direction (Picks/m) (b) X-machine direction (Ends/m) Wide width tensile strength (kN/m) (a) Machine direction (b) X-machine direction Strain at failure (%) (a) Machine direction (b) X-machine direction

Type A Type B 915 440 6.0 × 10.5 15.6 × 22.5 118

56

75

40

24.8 17.5

10.5 7.1

40.0 35.0

30.0 27.5

3.3 Jute Geotextiles for Filtration and Drainage Applications Specifications of nonwoven JGTs used for these kinds of applications are provided in Table 5. Table 5: Specifications for Nonwoven JGTs (after JGT Manual, 2008) Properties Type-1 Type-2 Weight (g/m2) 500 1000 Thickness (mm) 4 8 Width (m) 1.50 1.50 Strength (kN/m) (MD × CD) 4×5 6×7 Elongation at break (%) (MD × CD) 20 × 25 20 × 25 Pore size (O90) Micron 500 300 Co-efficient of water permittivity 3.4 × 10–3 3.4 × 10–4 (m/s) Durability (yrs.) Normal 1 1 499

Suitability of Natural Fibres in Geotextile Applications

3.4 Prefabricated Vertical Drains (PVDs)

4. NATURAL GEOTEXTILES DEVELOPED IN INDIA

Construction on sites underlain by thick strata of soft cohesive soils leads to long term settlement problems. These are best controlled by pre-consolidating the clay up to the anticipated settlement under design load, frequently in combination with the installation of prefabricated vertical drains (PVDs), to reduce the time required for foundation stabilization. The main aim of the application of PVDs is to accelerate the consolidation time by shortening the drainage path.

4.1 Brecodrain

A PVD is generally consisting of two parts, the sheath and the core. For synthetic fibre based PVDs, the sheath is a nonwoven filter fabric used to prevent the entry of soil particles and allow only water to penetrate inside the drain while the core is made in different profiles and helps in transporting water vertically through the drain. The entire PVD is 100 mm wide and 4-6 mm thick. The synthetic fibres used for these PVDs have a long life, but their intended function completes within a much shorter period and after that they do not apparently serve any purpose. On the other hand, these drains exhibit poor shear and buckling behaviour. Consequently, considerable amount of kinking occurs in such drains on consolidation of soil, resulting in a drop in discharge capacity. To this end, Lee et al. (1989) have reported the development and several field applications of PVD (brand name: Fibredrain) based on natural fibres, viz. jute and coir.

As regards discharge capacity, the ‘brecodrain’ performs better in the kinked condition than the commercial drains and it discharge capacity is less affected with increase in percentage of kinking compared to other commercial drains.

This PVD is basically a triaxially braided sheath of jute yarns encasing sixteen coir yarns and developed at Indian Institute of Technology Delhi (Banerjee et. al. 1997). The braiding technology has been successfully employed to produce drains on a single machine in one single stage operation. The important properties of ‘brecodrain’ are provided in Table 6.

4.2 Jute Asphalt Overlay Fabric

3.4.1 Fibredrain

It is 100% jute based asphalt overlay fabric developed for low traffic roads, like district and rural roads in India (Ghosh, 2006). This product would resist propagation of reflective cracking in pavements. The construction of the product is leno weave based. According to the functional requirements of the specific end-use, these geotextiles have moderately high Young’s modulus and suitable grid openings to be firmly anchored with the surrounding aggregates of the asphalt concrete ensuring the prevention of further crack opening. The related functional properties of the fabric (code name: Mod JAO) is provided in Table 7.

Fibredrain is made of jute and coir developed at the National University of Singapore is nowadays a well-accepted commercialized product (Lee et al. 1989). The important properties of the product are provided in Table 6. In comparison to synthetic prefabricated vertical drains (PVDs), this drain is expected to behave better in terms of kinking and buckling along with its eco-friendliness.

Table 7: Tensile Properties of Mod JAO (after Ghosh, 2006) Wide width Wide width Young’s strength, kN/m elongation % Modulus, MPa Warp- Weft- Warp- Weft- Warp- Weftway way way way way way 38.7 36.3 4.9 5.0 222.0 185.7

Table 6: Properties of Fibredrain & Brecodrain (after Banerjee et al. 1997) Variables (Unit) 1. Material Composition Sheath Core 2. Width (mm) 3. Thickness at 20 kPa (mm) 4. Weight of material/linear m (g) 5. Material strength at 1st break point a) Strength (kN) b) Extension % 6. AOS of Sheath i) O90 (mm) 7. Permeability at 50 mm water head and 2 kPa pressure (mm/s) 8. Discharge Capacity under 50 kPa pressure (ml/s)

Fibredrain

Brecodrain

Jute Fabric Coir Yarn 92–93 9.0 136 + 96

Jute Fabric Coir Yarn Approx. 100 10.2 260 + 68

4.5 4–5

2-2.4 5–6

0.425–0.6 0.41

0.3 0.54

13.1

22.0

4.3 Jute-Coir Pre-Seeded Erosion Control Blanket (PsECB) It has been recommended by Rickson (2003) that for preventing loss of soil, it would be desirable to use a product with a cover which is as close to 100% as possible. This observation pointed to the advantage of using nonwoven fabrics. It is also reported that heavy, needle-punched, nonwoven jute products are not suitable for vegetation growth. It is, however, quite conceivable to develop a nonwoven fabric based on the blend of jute and a suitable natural fibre that would lead to a more open and bulky material, permitting both light and space for growth of vegetation. Considering the two aspects of compatibility and availability, coir was chosen as the second component. It was decided to explore the possibility of trapping suitable seeds in the nonwoven fabric during the process of needle punching itself. Such a Pre-seeded Erosion Control Blanket (PsECB) would just need to be spread on a slope and suitably watered for the 500

Suitability of Natural Fibres in Geotextile Applications

seeds to germinate and vegetation to take root. The areal density (mass per unit area) of the final product was 380 g/m2 (Banerjee, 2004). 5. CONCLUSIONS In the context of ‘International Year of Natural Fibres (2009)’ and modernization of infrastructure in India, utilization of natural fibres in different national schemes is attracting encouragement. But, there is need to develop scientific research based new natural geotextile products as well as their promotion for commercialization. These are the only routes for the natural product manufacturing industry to reach the same platform as those already occupied by synthetic industry. REFERENCES A Manual on Use of Jute Geotextiles in Civil Engineering, (2008). 3rd Ed., JMDC, Kolkata, 59. Banerjee, P.K., Rao, G.V. and Sampath Kumar, J.P. (1997). “Characteristics of the Brecodrain for Soft Soil Consolidation”, Proc. Geosyn. Asia’97, Bangalore, 1: VI. 3–24. Banerjee, P.K. (2004). “A Strategy for Development of Geosynthetic Products”, Proc. Geosyn. India 2004: Geosyn.- New Hor., New Delhi, 377–385.

Banerjee, P.K. and Ghosh, M. (2008). “Studies on Jute-Asphalt Composites”, Jl. of Appl. Polym. Sci., 9/5: 3165–3172. Batra, S.K. (1985). “Other Long Vegetable Fibres”, Handbook of Fib. Sci. & Tech.: Fib. Chem., 4: 750–781. Ghosh, M. (2006). “Development of Jute-Based Asphalt Overlay Fabric”, Ph.D. Thesis, IIT Delhi, India. Lee, S.L., Karunaratne, G.P., Das Gupta, N.C., Ramaswamy, S.D. and Aziz, M.A., (1989). “A Vertical Drain Made of Natural Fibre for Soil Improvement Projects”, Proc. Int. Workshops on Geotext., Bangalore, 1: 271–276. Oosthuizen, P. and Kruger, D. (1994). “The Use of Sisal Fibre as Natural Geotextile to Control Erosion”, Proc. of 5th Int. Conf. on Geotext., Geomem. & Reltd. Prod., Singapore, 871–874. Rao, G.V. (1995). “Erosion Control with Natural Geotextiles”, 5th Chapter, Ero. Cont. with Geosyn., New Delhi, 59–92. Rickson, R.J. (2003). “The Use of Jute Based Products as Geotextiles”, Proc. of Int. Jute Symp.: Indian Jute–a New Symphony, Kolkata, 161–175. Sanyal, T. (2004). “Soil Saver—Its Scope and Limitation”, Proc. of National Sem. on Diver. Uses of Jute and Alld. Fib. Crops, Barrackpore, 141–145. Sanyal, T. (2006). “Jute Geotextile in Erosion Control and Strengthening of Sub-Grades—Two Case Studies”, Proc. Geosyn.- Recent Develop., New Delhi, 298: 206–217.

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