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A Study on Soil Stabilization through Innovative Material for Construction of Rural Roads

A Study on Soil Stabilization through Innovative Material for Construction of Rural Roads - A Case Study of East Gujarat

Ujjval J. Solanki - Lecturer, Darshan Institute of Engg. and Technology-Rajkot
Dr. N.C. Shah - Professor and Section Head, Civil deptt. SVNIT-Surat.
R.G. Dhamsaniya, - Asst. Prof., Darshan Institute of Engg.& Technology-Rajkot
M.D. Barasara – Asst. Prof., Darshan Institute of Engg.& Technology-Rajkot


Rural road connectivity is one of the key components for rural development, as it promotes access to economic and social services, generating agricultural income and productive employment. There are number of important points to be considered while involving suitable and economical designs for the low volume rural roads in India. For construction and maintenance as well as the level of quality control that can be effectively exercised in rural areas. To the extent possible, the use of locally available materials as such or after suitable processing has to be maximized in the larger interest of economy.

The study is aimed to improve engineering performance of locally available in situ material for subbase and base course of rural road. The name of innovative material is Consolid system of soil stabilization which is suggested by The Committee for Accreditation of New Materials and Techniques formed under the aegis of Highway Research Board of Indian Roads Congress to accredit patented or new materials/techniques, developed in India/abroad and evaluated as per recognized National/International Specifications has accredited the Consolid System for stabilization of subbase/base course on dated 4th August 2009

The study area is selected by NRRDA at East Gujarat–Rural road to check the improvement in soil parameter useful for rural road construction. The soil in East Gujarat contain Gravel with marginal proportion of clay particles. For efficient performance Consolid system demand equal proportion of Gravel, sand and silt & clay particles. One study stretch of length 1 Km is constructed by locally available in situ clay with treatment by Consolid system and CBR, UCS and Capillary rise tests are performed. Soak CBR is improved 18.55% from 3.2% and UCS is improved 2000 kPa from 250 kPa. which shows significant improvement in engineering properties of soil.

The treatment has made possible to use locally available in situ material. It also replace the granular material i.e. GSB material in sub base course, and also consolid system reduces the demand for heavy wearing course save resources and construction time.

Introduction

The Soil stabilization, in the broadest sense it is the alteration of any inherent property of a soil to improve its engineering performance. Improvement of stability or bearing power, density, shear parameter, reduce compressibility, permeability, swelling and shrinkage property by the use of controlled compaction, proportioning and/ or the addition of suitable admixtures or stabilizers.

The Consolid System

The Consolid system is a Swiss Technology for Permanent Soil Stabilization. Producer of consolid system in India is Grace & Sachi Enterprise-Ahmedabad and the competent authority of this company is Mr. Manish Shah. Consolid444 (Liquid) and Solidry (Powder) products are commercial. Table 1 shows the Consolid system component details

Table 1 Consolid System component properties
Sr. No Details Consolid 444 Solidry (SD)
1 Chemical composition Aqueous solution of a mixture of 20% mono-molecular and poly-molecular interfacial active substance. -Organic material Blend of 96.5 % of Portland cement and lime, coated with 3.5 % Solidry
2 Form Liquid Powder
3 Color Milky white to yellow brown Light grey
4 Work Strong reduction of water absorption through reducing the capillary activity Reduce permeability Lower OMC and Higher density of treated soil Strongly reduced swelling and shrinking behavior Solidry prevents the treated soil from water soaking in by closing the capillary.

The consolid soil stabilisation system was expressly developed for soil stabilisation. Every cohesive soil possesses the characteristic to petrify again. It requires a very long time and high pressure. Through the addition of catalysts we can speed up this process. The consolid soil stabilization system speeds up the natural process of solidification of all kinds of cohesive soil. It improves and consolidates the soil. The consolid system is changing the behaviour of any soil itself toward petrification and does not act as a binder or chemical reactant. A soil, once treated remains treated for permanent and will keep the advantages of the upgrade without timely limitation. A treatment of soils with additives products of the consolid system allows to upgrade any kind of soil to risk free construction material. The improvement of the treated soil is substantial and allows to incorporate up to 50 to 70 % of clayey, silty fines material which is usually classified as unacceptable for construction purposes in road construction or road rehabilitation. The treatment improves not only the stability and loading capacity; it enables also a tailored realization of full impermeability, which allows to use treated soil as lining in ponds or artificial lakes, dams and other water exposed constructions. Such treated impermeable soil material is also excellent construction material for dams, railway embankments and formations, but also of high value to form bottom soil layers as well as covering soil material at disposal areas to avoid seepage and the pollution of groundwater.

The consolid system for soil stabilization is always affected by two products, which are used together. It is consolid444 (C444) and solidry (SD). Consolid444 (C444) liquid components and solidry is a powder like component. The two components are mixed with the soil. Afterwards the soil is fully compacted. The consolid soil stabilisation system can be used for almost every kind of soil. The consolid soil stabilisation system is a total system, not only compaction aid or something else. It allows to change the behaviour of the treated soil completely. Water is the most effective enemy of stability; consolid fights against the capillary rise of water and agglomerated the fines irreversible.

A soil loses its bearing strength by taking up water. Therefore any diminution of such water absorption will yield increased bearing capacities. The CBR value (California Bearing Ratio) taken as an indicator for the bearing capacity of a soil, a CBR value of 3–5 times that of an untreated soil can be expected by the consolid soil stabilisation treatment. The use of consolid system in the field has some economical advantages on cost. Using local soil as much as possible instead of bringing the material from outside, the digging of the local soil and exchanging with the material brought from outside and avoiding the cost of both transportations, one of the most important advantages of the consolid system is the opportunity to use and develop the local material that generally causes costs to increase, when local material needs to be exchanged with the material that is brought from outside, the opportunity to pre-mixing the material and saving construction time.

As cement and lime are additives with hydraulic binding properties, they significantly increase the CBR values of any soil they are applied. However, consolid system does not have any binding property. Although the natural soil sample used in this study is not a type of soil on which consolid system has a maximum effect, it is considered that good CBR values are obtained. Since the consolid soil stabilisation products interact with the fine particles that thanks to the treatment can be used as natural binders, sand has to be mixed with cohesive soil prior to the treatment with the consolid soil stabilisation additives in order to obtain a content of fines of approximately 20%–30%. The soil mix prepared in this way can then be treated just as any other soil. In principle all cohesive or semi-cohesive soils or soils with a certain amount of silt (0.002–0.1 mm) lead to a permanent soil stabilisation. The optimal soil mixture is 1/3 clay and silt (0–0.2 mm), 1/3 sand (0.2–2 mm), and gravel and stones (2–200 mm). Missing fractions are easily mixed in from nearby soils.

Scope of The Study

To Study soil stabilization for subbase and base course using innovative material namely Consolid system of soil stabilization for rural road in East Gujarat at District –Dahod. Taluka: JHALOD. One stretch of road details as shown in Table No 2, and Figure 1.

Table 2 Location of field study
Sr. No Name of road Length of Road - Km. Study
01 Karath Kali Mahudi Bharkha 1.02 Jhalod. Dist Dahod
Innovative Material for Construction of Rural Roads
Figure 1: Study area location

Objectives of the Study

To study the improvement in physical and engineering properties of soil using innovative material namely Consolid system application in sub base and base course in rural road in East Gujarat at District –Dahod. Taluka: JHALOD.

Codal Practice for Stabilized Soil in Pavement.

IRC: SP: 72-2007-Guidelines for the design of flexible pavement for low volume rural roads.

Subbase materials: Liquid limit and plasticity index of not more than 25 and 6 respectively. The soaked CBR value should not be less than 20. If the material is not available in economical leads, the subbase material meeting the prescribed grading with a soaked CBR value of not less than 15 can be permitted with the approval of competent authority. The minimum thickness of subbase shall not less than 100mm.

Subbase course-Cement treated

The cement content for cement treated subbase should be determined by mix design, yielding a 7 day unconfined compressive strength of not less than 17 Kg/cm2.= 1700 kPa.

Base course material

Soil cement base:
The soil cement mix should be designed to attain a minimum laboratory 7 day UCS of 2.76 MN/m2. =27.6 Kg/cm2 = 2760 kPa. The thickness of base shall not less than 150mm.

IRC: 51-1992 -guidelines for the use of soil lime mixes in road construction.

As per IRC: 51-1992 UCS Design procedure should be preferred since it is more realistic as compared to CBR Design.

Strength Criteria: For testing the strength of stabilized soils, the CBR test is widely used in the case of gravelly soil where as UCS test is often used with fine grained soils.

CBR Test: Minimum CBR value for the lime stabilized sub base should be 15% for low trafficked rural road.

UCS Test: In terms of the unconfined compressive, the lime stabilized soil used for sub base should have a strength of 700 kPa (kN/m2 ) = 7 Kg/cm2.

IRC-8 IRC-88-1984 :recomme- nded practice for lime flyash stabilised soil base/subbase in pavement construction.

The minimum unconfined compressive strength and CBR values after 28 days curing and 4 days soaking should be 7.5 Kg/cm2 and 25% respectively. In terms of seven days curing and 4 days soaking, the minimum unconfined compressive strength and CBR values should be 3 Kg/cm2 and 10 % respectively.

Innovative Material for Construction of Rural Roads
Figure 2: Existing prepared earthwork of gravelly material Figure 3: Composite soil

Design of Experiment

Innovative Material for Construction of Rural Roads
Figure 4: CBR mould preparation on site
The purpose of the experimental work is to investigate the effect of addition of Consolid System of soil stabilization on various Engineering properties of soil like CBR value in soak and unsoak condition, Unconfined Compressive strength (UCS). One more test which typically represent the field condition–Capillary Rise Test is performed, and also to investigate its utilization as a Subbase and Base course for rural road construction.

As shown in Table 3.1 the soil sample is tested for CBR unsoaked and soaked with and without consolid system. CBR test is performed as per IS: 2720 (Part-16). UCS Test: IS 2720 (Part-10) -1973.

UCS–Unconfined Compressive Strength test, It is mostly performed on fine grained soil. The maximum load that can be transmitted to the sub-soil by a foundation depends upon the resistance of the underlying soil or rock to shearing deformation or compressibility. Therefore it is the prime importance to investigate the factors that control the shearing strength is commonly investigated by means of compression test. The purpose of this test is to obtain a quantitative values of compressive strength and shearing strength of such soil in an undrained state.

Innovative Material for Construction of Rural Roads

Field Application of Consolid System

The soil sample collected from study stretch District: Dahod. Taluka: Jhalod, The physical properties is tested for 2 samples and CBR test performed collected on every 500 mt. Total length of road is 1.02 Km. The results shown in Table-1 Testing on Native soil of Karath kali Mahudi Bharkha Dabar falia Road.

Innovative Material for Construction of Rural Roads

Testing of Soil Samples of Study Stretch

East Gujarat. Dist: Dahod, Taluka : Jhalod.- One study stretch

Composite soil preparation

Innovative Material for Construction of Rural Roads
Figure 5: Application of Solidry Powder on Trial stretch at Karath kali Raod. Figure 6: Mixing with rotavator and compaction by roller
For Maximizing the use of in situ material there is cohesive soil is available nearby so the cohesive soil is placed over the prepared subgrade and mixed with coarser particle of the granular sandy material. The composite soil is ready to use for consolid system application.

As per manufacturer’s guidelines C444-Liquid and solidry powder mixed with soil by using rotavator and compaction by static roller of 10 ton as shown in fig-5 and Fig-6.

Innovative Material for Construction of Rural Roads
Figure 7: Treated top surface of Road at Karath Kali Mahudi Road Figure 8: Treated and Untreated soil sample for capillary rise test

As shown in Fig-7 compacted top surface of road.

Capillary Rise Test

Capillary rise test performed on UCS test size sample of 40 mm dia and 80 mm length. Samples are prepared as per UCS sample preparation procedure. Soil samples are prepared with and without consolid treatment. Soil samples are put in 20 mm deep water and capillary rise is measured.

Innovative Material for Construction of Rural Roads
As shown in Fig -8 left hand side sample is treated and right hand side is untreated

As shown in Fig 9 untreated soil sample fell down after one hour of capillary rise test. This shows the water proofing effect of consolid treatment.

Innovative Material for Construction of Rural Roads
Innovative Material for Construction of Rural Roads
Figure 9: Treated and Untreated soil sample for capillary rise test.-untreated sample fell down within one hour. Figure 10: Field CBR Testset up at Karath Kali Road

Field CBR Test on Study Stretch

After completion of stabilization treatment with Consolid on 1.02 Km of road field CBR test is performed on top surface of road. Field CBR test is performed after three week of road construction. The surface is left for routine traffic and vehicular movement has been started on prepared surface of road. Test set up as shown in Fig- 10

Innovative Material for Construction of Rural Roads
As shown in above Table No 8 there is significant improvement in CBR value. The test results shows that after period of time stability of road is improved. Prepared surface become stable and none yielding. From the above results average CBR may be considered in the range of 25% to 40%. The CBR at the time of construction before one month was 27.1%.

Innovative Material for Construction of Rural Roads

Economic Aspects

Overview

Quantifying the cost of stabilized soil is a very difficult issue to address. This is the result of several factors real figures can only be obtained when the full design of the construction makes use of all advantage of the treatment. For cost comparison treated and untreated pavement section cost is compared for crust provided on the study stretch. Study stretch at karath kali mahudi Road cross section as per Fig No 11. The treated layer thickness is same with untreated pavement course. Treated pavement has replaced the subbase course of Granular material (GSB) and base course of WBM/WMM. The treated pavement also replaces the bituminous binder course of BM/MPM. The cost is workedout for the crust provided at study stretch. The rates are as per DPR of this project.

Innovative Material for Construction of Rural Roads
Cost calculation for the study stretch with consolid treatment

The pavement thickness design and cross section as shown in Figure No 11. Cost calculation only for the provided crust. The cost calculation as shown in Table no 9. The rates are as per study stretch work, quantities are worked out for 1 Km length of road. The cross section of the road is as per Figure No-11. The cross section is for treated subbase and base course pavement.

Innovative Material for Construction of Rural Roads
Figure 11: Typical Cross section of Rural road with Consolid treatment

As shown in Fig 11 the cross section of rural road pavement for soil stabilization treatment with Consolid system. The Table no. 8 shows the cost calculation with chemical treatment. The cross section of road crust detail shows that there is replacement of Granular sub base course and 75 mm thick Water bound macadam (machine crushed metal) for base course. There is also total replacement of Bituminous binder course only surface course is provided with 25 mm thick Open Graded premix carpet (OGPC) with seal coat. The total cost for the above treatment is worked out Rs.13,41,680=00

Innovative Material for Construction of Rural Roads
Cost calculation for the study stretch without Consolid treatment

As shown in Fig 12 is the cross section of rural road pavement for usual construction practice. The Table no 10 shows the cost calculation without chemical treatment. The cross section of road crust detail shows that there is 175 mm thick Granular sub base course and 75 mm thick Water bound macadam (machine crushed metal) for base course. There is Bituminous binder course is provided by 50 mm thick Modified penetration macadam and surface course is provided 20 mm thick Open Graded premix carpet (OGPC) with 5 mm thick seal coat. The total cost for the above treatment is worked out Rs.12,54,052=00

Innovative Material for Construction of Rural Roads
Figure 12 Typical Cross section of Rural road with treatment

The difference between untreated and treated cost is 12,342/- with the Consolid system per km construction of rural road cost savings Rs.12,342/-

The benefit is in terms of saving in resource, the chemical treatment replace the Granular material and WBM (Machine crushed metal) so it is the benefit by saving useful resource. The saving is in bituminous binder course which also saves the resource.

The possible savings are substantial
  1. There is no soil to exchange – (May be some material has to be borrowed to improve the in-situ soil) which gives substantially savings in material and transportation costs.
  2. Bituminous course thickness is reduced
  3. Construction time can be saved.

Conclusion

The consolid additives improves the strength properties of soil expresses as CBR and UCS are increased if the treated material is dried back to about 50% OMC. Once the treated soil has been dried back, water ingress into the soil is prevented at high degree. The moisture content remains low and the strength high. The Atterberg’s limits are therefore not relevant.

From the laboratory experiment it is clearly identified that the treatment improves CBR 4 to 5 times and UCS is improved 11 to 12 times which shows that Consolid system increases the cohesion between soil particles and improves the shear strength of soil which ultimately improves the load bearing capacity.

The field CBR test is carried out on prepared base course it is in the range of 25 to 40%, The Laboratory CBR at the time of construction was 18.55 %. The field CBR results shows that there is considerable improvement in CBR after traffic movement on the road and there is a chance of further improvement in stability.

The new capillary rise test shows the actual effect of treatment. The test shows that the treatment create the water proofing effect, control water sensitivity of soil by reducing or destroying the capillary rise of water and by controlling the soaking in of surface water as one of the main supposition for stability.

It become feasible to replace the superior and costly layer of granular Subbase and Base course of WBM and bituminous binder course of MPM/BM/BBC, need wearing course only.

The use of consolid system can be attractive and most viable alternative in the regions where scarcity of granular material and stone metals are of high cost.

The Comtt for accreditation of New materials and techniques formed under the agies of highway research board of Indian Road congress to accredited patented or new materials has accredited large number of materials / techniques for a period of two years and these are being used on trial basis.

References

  • Alam singh "Soil Engineering in theory and practices" Vol-III selected topics. CBS publishers 2002,New Delhi.
  • ASTM :D1633 Standard Test Methods for Compressive Strength of Molded Soil-Cement Cylinders.
  • ASTM :D 5102-96 Standard Test Method for Unconfined Compressive Strength of Compacted Soil-Lime Mixtures
  • A.U. Ravi Shankar et.al. " Bio-Enzyme Stabilized Lateritic Soil as a Highway Material" Paper no-553 Journal of the Indian Road Congreee, July-September-2009, 143-151.
  • Behad Kalantari "Peat Soil Stabilization, using ordinary Portland cement, Polypropylene Fibres, and Air Curing Technique" EJGE Vol 13,2009.
  • Consolid AG Switzerland "The Consolid System manual"
  • D Neeraja et. al. "Use of certain admixtures in The construction of pavement On expansive clayey subgrade International Journal of Engineering Science and Technology.
  • IRC: 88-1984 "Recommended practice for lime fly ash stabilized soil base/sub base in pavement construction" 1984 published by Indian road congress-New Delhi.-1984.
  • IRC: 51-1992 "Guidelines for the use of Soil-Lime mixes in road construction." 1984 published by Indian road congress-New Delhi.-1992.
  • IRC SP:20-2002 "Guidelines for the design of flexible pavement for low volume roads" published by Indian road congress-New Delhi.-2002.
  • I.S. : 2720 ( Part 1 to 41) "Various Method of Test for Soil."
  • Madhavi Vedula et al "Low Cost Soil Stabilization Technique for Rural Road Construction" Commemorative Issue For National Conference on Rural Road and Exposition Green sampark PMGSY-2007.
  • Mark C. Jogan, "Low cost Technique of base stabilization" Iowa department of Transportation,1994.
  • Quality Assurance hand book for Rural Roads-Ministry of Rural Development Govt of India. National Rural Road Development Agency. Volume-I -2007
  • Kadiyali L.R. "Principles and Practices of Highway Engineering, Khanna Publishers-Delhi-2006.

NBMCW March 2012

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