International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

www.ijaser.in ISSN: 2455-9288

INFLUENCE OF NANOSIZED ADDITIVES ON THE IMPROVEMENT OF CLAY SOIL 1 2

Mr.S.Anandha Kumar, Mr.R.Manikandan, PG Student, Department of Civil Engineering, Karur College of Engineering, Karur, India. 2 Assistant Professor, Department of Civil Engineering, Karur College of Engineering, Karur, India. 1

Abstract: Nanotechnology plays a vital role in various fields and Nowadays it started to develop in the soil stabilization too. Nanotechnology is the science that deals with the particles which are less than 100 nm. Because of the nanosize, it is ready to react with the additives very effectively. Due to its nano size the behavior of soil also exhibits different properties. Nano sized particles has high specific surface area when compared to non nano sized particles. By using this Nano sized particles in soil stabilization the shear strength and the dry density of the soil improves and the reaction is more effective. In this experimental investigation, an attempt is made to see the effectiveness of Nano sized silica and lime particles in the stabilization of soil. Finally Results show that the nano admixed soil gives UCC strength of 629 kN/m2 which is 1.4 times greater than non-nano admixed soil.

INTRODUCTION Presence of weak soil in the construction sites is a major issue for any type of construction. To enhance the properties of the weak soil, many methods like soil stabilization, soil reinforcement, grouting, addition of admixtures etc. are adopted. Addition of admixtures like Lime, fly ash, Cement, bitumen based on type of soil improves the properties of soil to some extent. Use of industrial waste as additives is recently under study, but it arises a question of toxicity. So there is a need for finding a new innovative material. One of the new innovative fields recently introduced to soil is Nanotechnology. Nanotechnology is recently been introduced to Geotechnical Engineering. Nanotechnology is the science that deals with the particles which are less than 100 nm. The size of the Nano particles plays a crucial role in behaviour of soil exhibiting different properties. Laboratory experiments conducted by Taha [1] to study the fundamental geotechnical properties of mixtures of natural soils and its product after ball milling mixture. Lab results showed that the value of Atterberg limits were higher after Nano-soil addition. However, its plasticity index reduces which is advantageous in many geotechnical constructions. Compressive strength of original soil Cement and 1% Nano soil mixture showed double its value without Nano soil. Thus Nano particles are potentially suitable for improving the properties of soil/clay for various applications. The addition of different Nano materials, including Nano Cu, Nano MgO and Nano clay on the geotechnical properties of soft soil sample from Peneng state was described by Zaid Hameed Majeed and Taha [2]. The unconfined compressive strength increased as the Nano material content increased up to a certain percentage in the soil and then decreased afterwards. Noll, Bartlett and Dochat [3] investigated the use of nano silica particles in enhancing soil strength against consolidation and permeability. The hydraulic conductivity of soil was reduced by 3- 4 folds with Copyright © 2016 by the Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

www.ijaser.in ISSN: 2455-9288

addition of Nano silica.

MATERIALS Soil

The soil was collected from Palamrajakkapatty, Dindigul, at shallow depth after removing the top 0.5 depth soil. Table 1. Index Properties of Soil

Properties

Values

Specific gravity Clay % Silt % Sand % Liquid Limit % Plastic Limit % Plasticity Index % Free swell Index % Soil Classification

2.67 79 17 6 80 32 48 60 CH

Table 1 shows the index properties of soil. The soil is classified as CH type and based on FSI value the soil gets high swell classification. The Maximum dry density of the soil is 1.52g/cc and OMC is 25.74%. From Unconfined compression test, it was found that the shear strength of the soil alone is 254 kN/m2 at OMC. Additives and their characterization Silica and lime were the two additives used here for soil improvement which are collected and stored. Lime powder collected from local market. Silica powder collected from Sree Easwara Enterprises, Sowripalayam, Coimbatore, Tamilnadu. From HRTEM analysis the particle sizes of raw Silica in the range of 2µ - 14µ and Lime in the range of 30µ - 150µ were calculated. Chemical composition of the additives was obtained by EDAX test. Results shows that Silica consists nearly 50% of silica and lime consisted 31% calcium and 17% magnesium as its major contributed chemicals.

METHODOLOGY Preparation of Nano Particles Nano particles are commonly prepared by bottom up method and top down method. Top down method begin with bulk materials (top) that are subsequently reduced into Nanostructures (down) by the way of physical, chemical and mechanical processes for examples mechanical ballmilling, grinding etc. Preparation of Nano particles has done by planetary ball milling. A specific quantity of (about 100gms) silica and lime milled for 6 hrs and for 12 hrs respectively.

Fig 1. HRTEM images of ballmilled SILICA particles Copyright © 2016 by the Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

www.ijaser.in ISSN: 2455-9288

Silica and lime are taken as additives to mix with soil. Silica is mixed with soil upto 15% (5%, 10% &15%) with the addition of lime from 2% to 10% (2%, 6% & 10%). For the optimum mix, Nano materials of those additives mixed with soil and tested. Nano materials were prepared by using ball milling. Characterization test carried out on unmilled additive and milled additive to compare particle size and chemical composition. The index properties, compaction test, UCC test were carried out in soil and Nano materials. These identical samples were prepared for their maximum dry density at optimum water content based on compaction curves obtained. The samples are tested for 7 days curing.

Fig 2. HRTEM images of ballmilled LIME particles

From HRTEM analysis, the particle sizes of milled Silica in the range of 24nm - 72 nm and milled Lime in the range of 31nm – 62nm were calculated (figure 1 and figure 2). After ball milling process, particle size got reduced compare to raw additives.

RESULTS AND DISCUSSIONS Influence of Non - Nano Sized Additives on the Index, Compaction and UCC Strength Properties of Soil Effect of Silica + Lime Mix on Index Properties of Soil The effect of silica and lime mix with soil on liquid limit is presented in fig 3 and 4. Fig 3 shows the liquid limit of soil is decreased linearly for 5%, 10% and 15% of silica admixed soil with addition of lime and beyond that, the liquid limit value is nearly constant for further increment of lime.

Fig 3. Effect of lime content on liquid limit of soil + silica mix Copyright © 2016 by the Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

www.ijaser.in ISSN: 2455-9288

Fig 4. Effect of silica content on liquid limit of soil + lime mix

From fig 5, it is observed that the plasticity index of soil is decreased for 5%, 10% and 15% silica admixed soil with increase in lime content. The plasticity index of silica admixed soil is decreased for increase in lime content upto 4% as inferred from figure 6. Beyond 4% lime content, the variation in plasticity index of silica admixed soil is almost marginal.

Fig 5. Effect of lime content on plasticity index of soil+silica mix

Fig 6. Effect of silica content on plasticity index of soil +lime mix Copyright © 2016 by the Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

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Effect of Silica + Lime Mix on Compaction Characteristics of Soil As per IS 2720 part VII, compaction test is carried out for the soil alone and soil mixed with additives. The value of maximum dry density and corresponding optimum moisture content are inferred from compaction curves. The results are tabulated below in table 2. Table 2. Effect of Silica-Lime mix on the compaction characteristics of soil

γ dmax (g/cc) 1.52

OMC (%) 25.74

2% Lime

1.50

26.31

6% Lime

1.49

26.80

10% Lime

1.48

27.01

2% Lime

1.47

27.86

6% Lime

1.46

28.03

10% Lime

1.46

28.75

2% Lime

1.45

28.98

6% Lime

1.44

29.21

10% Lime

1.43

29.81

Description Soil alone Soil+5%Silica

Soil+10%Silica

Soil+15%Silica

From proctor compaction test, the γ dmax values are 1.50g/cc, 1.47 g/cc and 1.45 g/cc respectively for 5%, 10%, 15% silica with 2% lime. The OMC values are in the range of 26.31% to 28.98%. For 6% lime, the γ dmax values are 1.49g/cc, 1.46 g/cc and 1.44g/cc respectively for 5%, 10%, 15% silica. The OMC values are in the range of 26.80% to 29.21%. The γ silica

dmax

values are 1.48g/cc, 1.46 g/cc and 1.43g/cc respectively for 5%, 10%, 15%

admixed with 10% lime. The OMC values are in the range of 27.01% to 29.81%. The optimum moisture content did not vary much for varying % silica unlike γ dmax. The reduction in γ dmax is expected because of the low specific gravity silica replaces soil and thereby the γ Mitchel [5].

dmax

decreases, Sridharan and Prakash [4] and James K.

The γ dmax is always lower in soil for any % of silica and lime. Compare to the effect of lime, the role of

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International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

www.ijaser.in ISSN: 2455-9288

silica is significant in reducing γ dmax values. The OMC value increases steeply with % of lime. This is due to enhanced water holding capacity of soil-silica-lime mix due to the formation of flocculated structure. Effect of Silica + Lime Mix on UCC Strength of Soil From the stress-strain curves for soil with increasing % of silica with 2% to 10% lime, the UCC peak strength is determined and presented in this section with reference to silica independently for varying lime. All the UCC strength values are corresponding to 7 days cured UCC specimens.

Fig 8. Effect of lime on the UCC strength of soil+ silica mix

As seen from figure 9 and 10, the UCC strength is always higher in soil + 10% silica for 2% and 6% of lime compared to soil + 5% silica and soil + 15% silica with varying % lime. The optimum % for effective utilization of soil + silica + lime mix seems to be 5% silica + 10% lime.

Fig 9. Effect of silica on the UCC strength of soil+ lime mix

Influence of Nano Sized Additives on the Index, Compaction and UCC Strength Properties of Soil Table 3 compares the influence of nano particles and non-nano particles on the index properties of soil. The liquid limit, plastic limit and plasticity index non-nano particles of 5% silica+10% lime in soil are 49%, 36% and 13% respectively. In the case of 5% nano silica+10% nano lime in soil, the values are 58%, 37% and 21% respectively. The nano particles produced higher plasticity characteristics compared to non-nano particles. This mainly because of enhanced surface area of nano particles which eventually give raise to more water holding capacity resulting in high Copyright © 2016 by the Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

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plasticity characteristics. The γ dmax and OMC of soil+5% nano silica+10% nano lime are 1.42g/cc and 32.03% and whereas forthe same combination, non-nano particles admixed soil produce the γ dmax value of 1.45g/cc and OMC of 27%. The lesser value of γ dmax and higher value of OMC of nano particles admixed soil are mainly because of enhanced specific surface area because of particle fineness. The UCC strength of soil alone is 254kN/m2, and that of soil+non nano particles of 5% silica+10% lime is 493 kN/m2. In the case of soil+5% nanosilica + 10% nano lime, the peak strength 629 kN/m2. Compare to non-nano particles in soil, the nano admixed soil yielded UCC strength of 629 kN/m2 which is 1.4 times higher than non-nano particles. The higher strength of nano particles admixed soil is mainly due to higher reactivity of silica and lime with the soil because of the enhanced specific surface area. Table 3. Effect of Nano sized silica and lime on the Index, Compaction and UCC strength properties

LL

PL

PI

ϒd max

OMC

%

%

%

g/cc

%

UCC Strength 2 kN/m

Soil alone

80

32

48

1.52

25.74

254

5% Silica + 10% Lime

49

36

13

1.45

27.01

493

5% Nano Silica + 10% Nano Lime

58

37

21

1.42

32.03

629

Descrip tion

Hydraulic Conductivity Of Nano Particles Admixed Soil

The co-efficient of permeability (k) of soil was determined using falling head permeability test with a mould diameter of 7.5cm and effective height 6cm. The permeability test was conducted on compacted soil+ additive mix corresponding to the ϒdmax and OMC of the mix constituents. Table 4. Co-efficient of permeability of nano particles admixed soil

Description Soil Alone 5% Silica + 10% Lime 5% Nano Silica + 10% Nano Lime

Permeability ‘k’ cm/sec -6

4.95 X 10 -6 2.92 X 10 -7 1.97 X 10 -6

The co-efficient of permeability of soil alone is 4.95 X 10 cm/sec. This value has -6 reduced to 2.92 X 10 for soil+5% silica+ 10% lime. The ‘k’ value reduced to almost a Copyright © 2016 by the Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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International Journal of Advanced Science and Engineering Research Volume: 1, Issue: 1, june 2016

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fold. The ‘k’ value of for soil + 5%silica + 10% lime is 1.97 X 10 cm/sec. This result clearly indicates that of the soil particles could effectively fill the void of the soil particles and thereby soil-additives matrix becomes less permeable nature. In this case, compared to non-nano particles, nano particles could effectively fills the pores of soil particles owing to its fineness and hence results in lower permeability values.

CONCLUSIONS Based on the analysis of results, the following conclusions may be drawn. 1.

Addition of Nano sized silica and lime additives on soil decreases the liquid limit and plasticity Index values and increases the plastic limit values. Decrease in liquid limit and plasticity index was more than non Nano sized additive mixtures with soil. 2. The maximum dry density of soil with addition of 5% Nano Silica + 10% Nano Lime decreases the dry density to 1.42 gm/cm3 with increase in OMC of 32%. 3. For addition of 5% Silica and 10% lime the UCC strength increased to 493 kN/m2 with 7 days curing. Upon adding Nano sized particles of Silica and Lime the same value increased up to 629kN/m2 with 7days curing. 4. The Nano particles admixed soil yielded the co-efficient of permeability, 10 times lower than that of non-nano sized additives silica and lime.

REFERENCES 1. Taha.,(2009), ‘A review of stabilization of Soils by using Nano materials’ Australian Journal of Basic and Applied Sciences, 7(2) ISSN 1991-8178, pp.576-581 2. Zaid Hameed Majeed and Mohd Raihan Taha, (2010), ‘Effect of Nano material treatment on geotechnical properties of a penang soft Soil’, Journal of Asian Scientific Research, pp.587-592 3. Noll M.R., Bartlett C., and Dochat T.M. (1992), ‘In situ Permeability Reduction and Chemical Fixing Using Colloidal Silica’, Proceedings of the 6th National Outdoor Action Conference, National Ground Water Association, Las Vegas, NV, pp 443-457. 4. Sridharan. A and K.Prakash, (2007), ‘Geotechnical enginceering characterisation of coal ashes’, 3rd Ed, CBS publishers, New Delhi, India. 5. James K.Mitchel and Kenichi Soga, 2005), ‘Fundamentals of Soil Behaviour’,3 rd Ed, John Wiley & Sons, New York, USA.

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