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A Study on Engineering Properties of Cement Stabilized Seashore Soil

Dr. Samson Mathew, Asst. Professor, P. Selvi, PhD Student, and K.B.Velliangiri, Former P.G.Student, Department of Civil Engineering, National Institute of Technology, Trichirappalli

Soil stabilization is a technique for improvement of weak soils. The engineering properties of soil can be improved by soil stabilization. Two road stretches located in seashore areas have been selected for this study and three samples were collected from each road stretch at various locations. This study deal about the improvement of weak soil particularly in seashore area. Oneis Aranthangi-Kattumavadi road in Pudukkottai District. Another is Mannarkudi–Adhiramapattinam road in Thanjavur District.

The Engineering properties like Specific gravity, Optimum Moisture Content, Maximum Dry Density, Liquid limit, Plastic limit and Grain size analysis of the collected samples were identified by suitable laboratory tests. The strength tests like unconfined compressive strength and California bearing ratio tests were conducted in NIT laboratory.

Thanjavur and Pudhukottai samples along the above road stretches are having silt and clay particles from 30 to 45%. Based on the soil properties, it was considered that the cement is a suitable stabilizer. Cement used as a soil stabilizer in different percentages (2%, 4%, and 6%) is tested in all soil samples. The test results are compared with the initial engineering properties and strength properties.

Introduction

Development of an adequate network of roads, especially in remote areas is of vital importance in the socio-economic development of villages in a country. The transportation facilities have to be continuously upgraded and improved so as to keep pace with the traffic demand, which is being generated, by the development plans and resultant expanding economy. However, development of a large network of roads by traditional practices and techniques require heavy financial investments. Soil stabilization methods using locally available cheaper materials have considerable scope in reducing the initial construction cost of the pavements. The soil deposits along the coast may be of silty sand, silty clay, soft clay or any other soil type. Soil at a particular location may be unsuitable, wholly or partially, to the requirements of the construction engineer. But the various developmental activities necessitate making use of these lands, which are not having the desirable properties as an engineering material.

The following are the ways of dealing with unsatisfactory soils:
  • By pass the bad soil
  • Remove bad soil and replace with good material
  • Redesign the structure
  • Treat the soil to improve its properties. Such treatment is called soil stabilization.
Soil stabilization in the broadest sense is the alteration of any property of a soil to improve its engineering performance.

Research Significance

India has about 6000km long coastline stretching along nine states i.e. Gujarat, Maharastra, Goa, Karnataka, Kerala, Tamilnadu, Andhra Pradesh, Orissa, and West Bengal. There was a tremendous construction activity along the coast. In south India, the Tamilnadu state boundary has a long coastal line in eastern side along Puthukkottaitai, Thanjavur, Thiruvarur, Nagappa- ttianam, Ramanathapuram, Cuddalore, Chennai, Negercoil and Kanyakumari districts.Most of the road network near seashore area is poor in condition due to the settlement of subgrade soil. This settlement is purely occurred by the volume changes of subgrade soil. In its natural state the engineering properties of the soil is considered as very poor, if it is used as a subgrade layer for pavement construction. So, it is necessary to control the variability of the geotechnical properties of the soil using different additives. The main purpose of this research is to improve the load carrying capacity of the natural soil. The soil samples along the road stretches from Puthukkottai and Thanjavur districts are predominantly with silt and clays. Thesilt and clay contents are ranging from 30–50%. It also may affect the strength of the subgrade. In this work, an attempt was made to analyse the engineering properties of the natural soils and their improvement with suitable stabilizer.

Literature Review

Engineers are often faced with the problem of constructing roadbeds on or with soils, which do not possess sufficient strength to support wheel loads imposed upon them either in construction or during the service life of the pavement. It is, at times, necessary to treat these soils to provide a stable subgrade or a working platform for the construction of the pavement. These treatments result in less time and energy required for the production, handling, and placement of road and bridge fills and subgrades and therefore, less time to complete the construction process thus reducing the disruption and delays to traffic. These treatments are generally classified into two processes, soil modification or soil stabilization. The purpose of subgrade modification is to create a working platform for construction equipment. This modification in the pavement has no role in the design process. The purpose of subgrade stabilization is to enhance the strength of the subgrade and this increased strength is taken into account in the pavement design process. Manikant Mandal and Dr. Mayajit Mazumdar (1995), a study was made on the effect of additives on lateritic soil stabilization with cement and lime. Particularly, the strength and fatigue behavior, under repeated flexture, of stabilized latertic soil treated with additives, have not been studied in our country till now. Sodium carbonate analytical reagent grade was used as an additive. Static and dynamic tests were carried out on specimens of soil-cement and soil-lime mixtures prepared under standard as well as modified compaction. It has been found that sodium carbonate used as an additive in trace amounts, improves the strength of soil-cement and soil-lime. Also, the additive increases the value of modulus of rupture and durability of the stabilized soil. A. Arumugam and K. Muralidharan (1997), stabilizing the locally available soils and using them as subgrade materials generally reduce the cost of pavement construction. It was concluded that the mechanical stabilization saving in the construction cost of pavement upto 43% has been effected. Lime and cement stabilization saves the amount by 46.2% and 27.56% respectively. T.Lopez-Lara, J.A. Zepeda-Garrido and V.M. Castario (1999) this paper includes the evaluation of the main index properties of the soil, along with a characterization of the materials through X-ray diffraction. It has concluded that the polyurethane was the one material gives good performance to the soil, with 6% addition. Emhammed. A. Basha, Roslan Hashim and Agus S.Muntohar (1999), This paper presents the chemical stabilisation of soils using cement and rice husk ash. Three types of soils, residual soils, kaolinite and bentonite, were used in the study. Cement and rice husk ash reduced the plasticity of residual soil, kaolin, and bentonite. A considerable reduction was attained by cement-stabilised soils. In general, 6–8% of cement and 10–15% RHA shows optimum amount to reduce plasticity of soils. Reduction in plasticity index is an indicator of improvement. The maximum dry density of cement–stabilised residual soil and kaolin slightly decreased with increases in cement content, in contrast with cement-stabilised bentonite. Adding rice husk ash and cement increase the optimum moisture content of all soils. Azm S. Al-Homoud, Taisir Khedaywi and Abdullah M. Al. Ajlouni (1999), This research was undertaken to compare the effectiveness and economic feasibility of bitumen, lime, and cement as stabilizing agents for reduction of swell potential of a swelling soil from Northern Jordan. The results of this study showed that for a soil containing high percent fines, cutback bitumen treatment causes more reduction in swell potential than cement and less reduction than lime. For this type of soil the bitumen is the economical agent compared to lime and cement. Virender Kumar (2002), A study on the effect of lime as stabilizing agent and Na2 CO3 as an additive, when added to the soil-flyash combination has also been investigated. A combination of 70% soil, 28% flyash , 1% lime and 1% Na2 CO3 has been found to give best results against the optimum use of flyash in soil. In the soil flyash mix, flyash content beyond 15% does not reduce the permeability nor improve the dry density. Anil Misra, Debabrata Biswas and Sushant Upadhyaya (2004), This paper focuses upon the laboratory evaluation of the (1) stabilization characteristics of clay soils blended with self-cementing class C flyash, and (2) residual self-cementation capabilities of ponded class C flyash. In the analyses, it was found that the stabilization characteristics are the functions of curing time, curing condition, and clay mineralogy. Results obtained from the analyses showed that the OMC changes due to the addition of flyash, also the samples rapidly gained the compressive strength and stiffness within 7 days curing period, and the greatest increase occurred in 1 day due to the rapid hydration reaction of class C flyash. Typically the strength tends to increase up to 14 days curing period, and beyond 14 days, the strength retarded. After 28 days the samples became brittle. Costas A.Anagno– stopoulos (2004), In this study, a laboratory test programme was carried out to find out the effect of inclusion of cement and acrylic resin on physical and engineering behavior of a soft clay. A series of tests are conducted with the addition of 5% to 30% of cement contents and acrylic resin of 5% . It is concluded that the development of strength and stiffness for a short curing time (7 days) is delayed significantly because of A.R addition while for long curing time (28 days) the engineering parameters are increased considerably. Also addition of A.R showed a small increase in Cc for all percentages of cement because A.R is having the tendency to keep water in its molecule. S.A.Aiban, H.M.Al-Ahmadi, I.M. Asi, Z.U.Siddique, and O.S.B. Al-Amoudi (2005) The main objective of this study was to upgrade the load carrying capacity of pavements constructed on sabkha soils, using geo textiles, and to assess the effect of geotextile grade, base thickness, loading type (static and dynamic) and moisture condition (as-molded and soaked) on the soil fabric-aggregate (SFA) systems. The effect of geotextile in improving the load-carrying capacity of soil becomes negligible at higher deviator stress (i.e. 200 kPa) level. Also the inclusion of the A-400 geotextile was almost similar to the improvement achieved when adding 6.5% Portland cement. Suksun Horpibulsuk et al. (2006) The characteristics of strength development in cement stabilized low plasticity and coarse-grained soils. A phenomenological model to predict the laboratory and field strength development based on a single trial test is presented in this work.

Experimental Programme

Materials and their Properties

The soil samples used for this study were collected from the following road stretches and their corresponding labels are given against the location. The engineering properties of these samples were found out and suitable stabilization methods have been identified based on these properties. The basic properties are presented in Table 1, 2.

Engineering Properties of Natural Soil

Samples from Pudukkottai district

  • Road stretch from Aranthangi to Kattumavadi at km 8/4 (sample P1)
  • Road stretch from Aranthangi to Kattumavadi at km 14/8 (sample P2)
  • Road stretch from Aranthangi to Kattumavadi at km 24/8 (sample P3)
  • Samples from Thanjavur district
  • Road stretch from Mannargudi to Athirampattinam at km 60/0 (sample T1)
  • Road stretch from Mannargudi to Athirampattinam at km 66/4 (sample T2)
  • Road stretch from Mannargudi to Athirampattinam at km 73/0 (sample T3)
The specific gravity of Pudukkottai and Thanjavur soils are ranging from 2.70-2.75. This range is following the typical specific gravities of Inorganic clay according to IS 2720. Considering the particle size of the natural soil samples in both the locations presence of sand content is high compared to fine contents. Presences of fines in the Thanjavur samples are higher than the Pudukkottai soil. The IS soil classification guidelines were followed to classify the soils. Based on the Consistency limits, both the soils were classified as SC (clayey sand) soil group.

The Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) values for all samples were depicted in Tables 1 and 2. It was observed that the OMC values for the Thanjavur samples are having greater value than Puthukkottai samples. The specific surface area for the fine-grained soil is maximum. So, it is necessary to add more water to get the maximum MDD in the case of Thanjavur soil samples. The Unconfined Compressive strength (UCC) of the natural soils may be expressed in terms of their consistency. Considering the UCC values from Table 1, the P1 and P3 samples were categorized as "very stiff" and P2, T1, T2, T3 are having "stiff" consistency.

Except P2 sample remaining are giving less than 3% California Bearing Ratio values. So, the natural soil strength may be improved by adding Cement.

Properties of Cement

Experimental Programme

The soil samples from Pudukkottai district are mixed with different percentages of cement as 2, 4, and 6, similarly the samples from Thanjavur district are mixed with 1,2,3 and 4% of cement have been subjected to different laboratory tests. According to the Indian standards the consistency limits, compaction characteristics, unconfined compressive strength, California Bearing Ratio tests were conducted on various mixes. The test results are presented in Table 3, 4 respectively.

Engineering Properties of Natural Soil

The UCC test was conducted on cylindrical specimens are prepared at Optimum Moisture Content. In natural and stabilized form the specimens were tested in compression testing machine immediately after moulding. The CBR tests were conducted for four days soaking period only.

Results and Discussions

Consistency limits

From Table 3, 4, it was observed that the Plasticity index decreased from 7 to NP with 6% cement addition in Puthukkottai district samples. The samples P1 and P2 are showing NP state at 6% cement addition. But sample P3 shows the reduction at 4% cement itself. The PI reduction is occurring at 4% cement in T2 and T3 samples and at 3% cement in T1 sample. The addition of cement increases the plastic limit and decreases the liquid limit. The PI is a measure of a soil's cohesive properties and is indicative of the amount and nature of clay mineral. The substantial reduction of Plasticity Index values indicates not only an improvement in the volume change characteristics but also modification of the soils into more stable and workable material. The effects of cement on consistency limits of all the soil samples are graphically represented in Fig 1-6.

Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 1: Plasticity Index Vs various Cement Content of sample P1
Figure 2: Plasticity Index Vs various Cement Content of sample P2
Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 3: Plasticity Index Vs various Cement Content of sample P3
Figure 4: Plasticity Index Vs various Cement Content of sample T1
Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 5: Plasticity Index Vs various Cement Content of sample T2
Figure 6: Plasticity Index Vs various Cement Content of sample T3

Proctor Compaction Test

The results of standard proctor test on soil treated with different percentage of cement are shown in Table 3, 4 for Puthukkottai and Thanjavur district samples respectively. The Pudukkottai soil samples are having the OMC values in the range of 7.2-8.8%. But the stabilized samples are showing a range of 7.6-9.9%. The Optimum Moisture Content increases with increase of cement content in all soil samples. It is observed that the dry density decreases in all soil samples with increase in cement content.This is due to the basic fact that the soil-cement mix may have difference in specific gravity than the original one. Also the addition of water causes the bulking phenomenon in the stabilized soil. During this time the capillary forces resisting the rearrangement of particles against the external compactive energy. The fine cement particles influence the compatibility of soil-cement material. This soil-cement interaction resulting in the cementitious products also it gains strength.

California Bearing Ratio

The effect of cement on California bearing Ratio of the stabilized soils are depicted in Table 3,4 and represented in Figure 7-12. It is observed that the addition of 6% cement increases the CBR value of the Puthukkottai natural soil (P3) from 2.90% to 135%. Similarly, addition of 4% cement increases the CBR value of the Thanjavur natural soil (T3) from 2.50% to 68%. The reason for this strength improvement is the pozzolanic action in soil-cement material. The cementitious reaction between cement and clay takes place as primary and secondary processes. Hydration of the cement is regarded as the primary reaction and forms the normal hydration products that bind particles together. In the secondary process, the fresh calcium hydroxide formed in the primary phase reacts with the silica and alumina in the clay to form additional cementitious material.

Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 7: CBR value comparison chart for various Cement Content for sample P1
Figure 8: CBR value comparison chart for various Cement Content for sample P2
Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 9: CBR value comparison chart for various Cement Content for sample P3
Figure 10: CBR value comparison chart for various Cement Content for sample T1
Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 11: CBR value comparison chart for various Cement Content for sample T2
Figure 12: CBR value comparison chart for various Cement Content for sample T3

Unconfined Compressive Strength

The Unconfined Compressive (UCC) strength values are increased from 2.34 to 5.76 kg/cm2 at 6% cement on Puthukkottai district sample (P3) are given in Table 3 and Figure 13-15. Addition of 4% cement shows a significant improvement in UCC values on Thanjavur samples (T2) from 2.45 to 5.65 kg/cm2 are given in Table 4 and Fig 16-18.

The cement treated specimens exhibit notably higher strength than do natural soil specimens. It was also observed that the cement treated soils achieved higher strength at lower strain when compared to the natural specimens. The higher strength is attributed to the presence of cementation bonds in cement treated specimens.

Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 13: UCC comparison chart for various Cement Content for sample P1
Figure 14: UCC comparison chart for various Cement Content for sample P2
Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 15: UCC comparison chart for various Cement Content for sample P3
Figure 16: UCC comparison chart for various Cement Content for sample T1
Engineering Properties of Natural Soil
Engineering Properties of Natural Soil
Figure 17: UCC comparison chart for various Cement Content for sample T2
Figure 18: UCC comparison chart for various Cement Content for sample T3

Conclusions

The following conclusions are drawn from this research work
  • As per Indian Standard based on the consistency limits of the natural soil samples from Puthukkottai and Thanjavur are classified as SC (clayey sand).It was identified that Cement is the suitable stabilizer for this SC soil group.
  • The PI values are ranging from 8 to 9 only. This shows that the amount of clay content is lower than the silt content. Considering the state of plastic of the soils they are falling in 'low' plastic category.
  • Plasticity Index of the all samples from Puthukkottai samples are reduced with the addition of 2-6% cement. With the addition of 4% cement the plasticity index of all the samples from Thanjavur comes down to approximately 0. At this plasticity index soils are quite friable and workable.
  • The maximum dry density decreases and optimum moisture content increases with the addition of Cement. The Pudukkottai soil samples are having the OMC values in the range of 7.2-8.8%. But the stabilized samples are showing a range of 7.6-9.9%.
  • The cement required to get 10% CBR is 1%. Addition of 6% cement gives a maximum CBR values in the range of 126-135% on Puthukkottai samples. Similarly, 4% cement gives a maximum value in the range of 66-68% on Thanjavur samples. As the cement is a costlier one, using a small quantity will economize the road project.

References

  • Manikant Mandal and Dr. Mayajit Mazumdar (1995), "A Study on the effect of sodium carbonate as an additive to stabilized soil," Indian Highways, December 1995, pp. 31–36.
  • Dr. A. Arumugam and K. Muralidharan (1997), "Optimi- sation of Pavement construction cost on stabilized soil subgrade," Indian Highways, March 1997, pp. 33–42.
  • T.Lopez-Lara, J.A. Zepeda-Garrido and V.M. Castario (1999), "A comparative study of the effectiveness of different additives on the expansion behavior of clays," www.ejge.com
  • Emhammed. A. Basha , Roslan Hashim and Agus S.Muntohar (1999), "Effect of the cement–Rice husk ash on the Plasticity and compaction of soil," www.ejge.com
  • Azm S. Al-Homoud, Taisir Khedaywi and Abdullah M. Al. Ajlouni (1999), "Comparison of effectiveness and economic feasibility of bitumen, lime and cement as stabilizing agents for reduction of swell potential of a clayey soil," Indian Highways, January 1999, pp.51–58.
  • Prof (Dr) Virender Kumar, (2002), "Compaction and permeability study of a soil stabilised with Flyash, Lime and Na2CO3 ", Journal of The institution of Engineers" Volume 82, Febraury 2002, pp. 173–176.
  • Anil Misra, Debabrata Biswas and Sushant Upadhyaya (13 Decemeber 2004), "Physio- mechanical behavior of self cementing class C flyash-clay mixtures," www.sciencedirect.com
  • Costas A.Anagnostopoulos (2004), "Physical and Engineering Properties of a cement stabilized soft soil treated with Acrylic Resin additive," www.ejge.com
  • S.A.Aiban, H.M.Al-Ahmadi, I.M. Asi, Z.U.Siddique, and O.S.B. Al- Amoudi (8 March 2005), "Effect of geotextile and Cement on the performance of sabkha subgrad," www.sciencedirect.com.
  • Suksun Horpibulsuk et al. (2006), "Strength Development in Cement stabilized low plasticity and Coarse grained soils: Laboratory and Field Study," Soils and Foundation, vol.46,No.3, pp.351–366.
  • IS 2720 (part 4)-1984 Test For Grain size Analysis
  • IRC 37–2001, Guide lines for the Design of flexible pavements (second revision)
  • IS 2720 (part XXI)–1976 (Test for soils)
  • IS 2720 (part XXII)–1972 (Test for soils)
  • IS 2720 (part XXVII)–1977 (Test for soils)
  • IS 2720 (part XXIII)–1976(Test for soils)

NBMCW January 2009



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