Introduction In the construction industry it is necessary to maintain a balance between cost and performance

Introduction
In the construction industry it is necessary to maintain a balance between cost and performance, along with satisfying environmental regulations, which has become a important challenge for engineers. Soil stabilization is a method of improving strength and durability of soil. Most common application of soil stabilization can be seen in construction of roads and airfields pavement. In Chemical stabilization it is done by adding different chemical additives to the soil , which alter the geotechnical properties of soil by physically combining with soil particles. Enzymes enhance the soil properties and strength. TerraZyme is non corrosive, non toxic, and inflammable liquid which extracted from the vegetable and fruit extract, which can be easily mixed with water at the optimum moisture content. TerraZyme improves strength of soil by significantly changing the properties of soil. Life of a structure stabilized with TerraZyme increases as CBR value is increased and consistency limits are decreased. By Using TerraZyme the chemical bonding is significantly increased and a permanent structure is formed, which can resist wear and tear, infiltration and weathering of soil particles.Bio enzyme replaces the need of granular base and sub base, which further reduces the cost of construction. Dosages of TerraZyme mainly depends upon the type of soil, clay content and plasticity index of soil.
Soil Stabilization:-
Soil Stabilization is the alteration of soils to enhance their physical properties. Stabilization can increase the shear strength of a soil and/or control the shrink-swell properties of a soil, thus improving the load bearing capacity of a sub-grade to support pavements and foundations.
Problems in Soil:-
Expansive Soil-Expansive soil has tendency to swell when its moisture content increases, and may impose a potential risk to safety of many civil engineering structures such as roads, railways and airport runway foundation constructed on this type of soil.( H Hasan, et al. 2016). Expansive soils” are those which experience great changes in volume when their water content varies. These types of soil are widely distributed throughout the world (Huang and Wu, 2007; Sabtan, 2005), although they are especially abundant in arid zones, where conditions are suitable for the formation of clayey minerals of the smectite group such as montmorillonite or some types of illites (Avsar et al., 2009; Nowamooz and Masrouri, 2008; Sabtan, 2005). These clays are characterized by having a very small particle size, a large specific surface area and a high Cation Exchange Capacity (CEC) (Fityus and Buzzi, 2009; Nalbantoglu, 2004; Nalbantoglu and Gucbilmez, 2001). The swelling of this type of clay is related to three types of factors: geology, the engineering factors of the soil, and local environmental conditions. Geology primarily determines the presence in the soil of these types of expansive clay minerals. Among the engineering factors included are the soil moisture content, plasticity and dry density. The most important local environmental conditions to consider are the amount of the clay fraction in the soil, its initial moisture conditions, and confining pressure (Sabtan, 2005). Volume changes of these types of soil are a major cause of natural disasters, since they cause extensive damage to the structures and infrastructure on top of them (Assadi and Shahaboddin, 2009; Avsar et al., 2009; Chen et al., 2007; Ferber et al., 2009; Huang and Wu, 2007). This has even led some authors to refer to them as “calamitous soils” (Chen et al., 2007).

Loose Soil- The behavior of loose granular soils has been studied by many researchers for many years. Most of their studies have focused on the saturated behavior of loose clean sands ~Casagrande 1976; Sladen et al. 1985; Ishihara 1993; Sasitharan et al. 1993; Yamamuro and Lade 1998!. These studies have shown that very loose sand exhibits flow failure during undrained shearing. This may lead to the so-called ”static liquefaction.” Most fill materials used for constructing slopes in the Far East have been weathered granular soils, which contain some quantity of fines, and they are unsaturated in nature. Most studies on the behavior of unsaturated soils have focused on fine-grained soils ~Alonso et al. 1990; Maatouk et al. 1995; Wheeler and Sivakumar 1995; Cui and Delage 1996!. Recently, more efforts have been made to understand thebehavior of unsaturated weathered granular soils ~Toll 1990; Gan and Fredlund 1996; Han and Rahardjo 2000!. However, most of these investigations focused mainly on the shear strength of the unsaturated soils. Other mechanical behavior, like the stress– strain relationship, volume change, and dilatancy are also important, particularly when analyzing the stabilization measures of the loose fill slopes.( Charles W. W. Ng, and A Chiu 2003)

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Necessity of Sub grade improvement:-
Although a pavement’s wearing course in a highway/ road is most prominent, the success or failure of a pavement is more often dependent upon the underlying subgrade – the material upon which the pavement structure is built. Other than that in order to-
1)Improve low strength soil (CBR ; 5) as per IRC 037.
2)Moisture Control.
3)Enhancing Index properties and strength properties of soil.
Different methods of soil stabilization:-
H Afrin (2017) Concluded that the improvement methods of stabilization are:
1)Mechanical Stabilization
2)Stabilization by using different types admixers
a)Lime Stabilization
b)Cement Stabilization
c)Chemical Stabilization
i)Organic
ii)Inorganic
d)Fly ash Stabilization
e)Rice Husk ash Stabilization
f)Bituminous Stabilization
g)Thermal Stabilization
h)Electrical Stabilization
i)Stabilization by Geo-textile and Fabrics
j)Recycled and Waste Products etc.Thermal stabilization
The selection of the method depends on modification of properties sought in shear strength, compatibility and permeability of the soil and on the depth and thickness of compressible layer, type of structure, allowable, total and differential settlements, available time and equipment, local experience, environmental factors and their costs. Because of the great variety of soils no, one method is ever successful in more than a limited number of soils. When a material or combination of materials with adequate mechanical stability cannot be obtained or where enhanced strength or resistance to water softening is required, then it is advisable to consider stabilization with chemicals.

Advantages and disadvantages of different stabilization methods
Addition or removal of soil particles In case of longest roadway replacement of soil is not adequate.
Organic Chemical Eco friendly, low cost with higher bearing capacity.
Lime Dust problem, slurry application.
Cement Uneconomical as requirement of cement quantity is higher.
Membrane stabilization Costly in nature as well as careful laying needs to be done.

Enzyme:-
Enzymes by definition are an organic catalyst that speeds up a chemical reaction, that otherwise would happen at a slower rate, without becoming part of the end product.  They began being used in commercial applications in the agriculture industry and were found to have stabilization qualities in certain soil types and classifications. Enzyme- Natural, Non toxic, non flammable, Non Corrosive liquid enzyme formulation fermented from vegetable extracts that improves the engineering properties of the soil. Enzymes cause the water typically held on the exterior of a clay particle to be shed and in turn blanket the clay particle causing the particle to become neutral in charge, which pulls the particle closer together.  This not only reduces the water that can be absorbed in the clay structure but it strengthens the soil and bonds the structures together. Enzymes are environmentally friendly, organic products that when used properly can provide great soil stabilization qualities for road construction, roadbeds, airstrips, storage yards, access roads and in military applications.
TerraZyme a Bio Enzyme Stabilizer:-
TerraZyme is a natural, non-toxic, non-corrosive and non-inflammable liquid, produced by formulating vegetable extracts. Organic enzymes come in liquid form. They are perfectly soluble in water, brown in colour with smell of molasses. Their aroma has no effect. Neither gloves nor masks are required during handling. TerraZyme is specially formulated to modify the engineering properties of soil. They require dilution in water before application. TerraZyme when added to water and mixed with soil alters the engineering properties depending upon the type of the soil and dosage of enzyme. These enzymes are liquid additives, which act on the soil to reduce the voids between soil particles and minimize absorbed water in the soil for maximum compaction. The enzymes react with the organic matter (humid matter) in the soil to form cementations material. This decreases the swelling capacity of the soil particles and reduces permeability. The application of TerraZyme enhances weather resistance and increases load bearing capacity of soils. These features are particularly evident in fine-grained soils such as clay in which the formulation affects the swelling and shrinking behaviour. The reaction is at micron level and the presence of finely divided humid matter and clay-sized particles is essential. Presence of clay is essential as the bonds formed bind this size of particles. The formulation has the ability to change the matrix of the soil so that after compaction the soil loses its ability to reabsorb water and the mechanical benefits of compaction are not lost even after water is reapplied to the compacted soil. Once the enzyme reacts with the soil, the change is permanent and the product is bio-degradable (Puneet Agarwal ; Suneet Kaur 2014). TerraZyme, manufactured by Nature Plus Inc- U.S (under ISO- 9002 procedures) is an excellent replacement for metalling and solling.

TerraZyme is available in two formulations:
a.TZ for most common soil stabilization applications.
b.TZ for soils with high clay content.
Mechanism of Soil Stabilization by Bio-Enzyme
Puneet Agarwal ; Suneet Kaur (2014) concluded that in clay water mixture positively charged ions (cat-ions) are present around the clay particles, creating a film of water around the clay particle that remains attached or adsorbed on the clay surface. The adsorbed water or double layer gives clay particles their plasticity. In some cases the clay can swell and the size of double layer increases, but it can be reduced by drying. Therefore, to truly improve the soil properties, it is necessary to permanently reduce the thickness of double layer. Cat-ion exchange processes can accomplish this. By utilizing fermentation processes specific micro-organisms can produce stabilizing enzyme in large quantity. These soil-stabilizing enzymes catalyze the reactions between the clay and the organic cat-ions and accelerate the cat-ionic exchange without becoming part of the end product. TerraZyme replaces adsorbed water with organic cat ions, thus neutralizing the negative charge on a clay particle. The organic cat ions also reduce the thickness of the electrical double layer. This allows TerraZyme treated soils to be compacted more tightly together. TerraZyme resists being replaced by water, thus reducing the tendency of some clay to swell.
Clay Water effect- Enzyme reduces size of double layer of clayey, thereby reducing swell in clayey in soil. Cat ion Exchange- Thickness of double layer is reduced permanently, which reduces the water absorption by clay, which in turn reduces plasticity in clay and increases molecular structure of clay. Enzyme stabilization effects- Organic cat ions have large flat structures approaching size of clay particles, which then neutralizes the negative charge of clay by covering it. Other TerraZyme effects- It facilitates the removal of pore water leading to higher densities and reduced void percentages, leading to realignment of particles, thereby reducing permeability of soil.
Benefits of Using TerraZyme(Avijeet Agencies ( P) Ltd):-
I.Cuts costs by 10%-20%
II.Higher CBR value/higher road strength: TerraZyme base structures have a much higher CBR value.
III.Lower the maintenance cost by 30%-50%
IV.Saves construction time by 50%
V.Pavement thickness is reduced by 5%-10% in phase of trials.
VI.Environment friendly and bio-degradable product.
VII.The product has been accredited by IRC.

Discussion
Puneet Agarwal ; Suneet Kaur (2014) concluded that by using TerraZyme in black cotton soil with a dossage of 0.25ml/5kg ; 4ml/5kg strength of the soil can be increased to 20.2% ; 6.2 % respectively. By using TerraZyme in Lateritic soil with a dossage of 0.029ml/kg ; 0.050 ml/kg Shankar et al. (2009) stated that liquid limit and plastic limit of soil drastically changes and enchances the strength of soil significantly. Venika Saini ; Priyanka Vaishnava (2015) used dossage of TerraZyme 3.0m3/200ml ; 1.5m3/200ml in Clayey silt(CM) soil, where liquid limit and plastic limit decreases to 10.771%, 8.82% and 21.15%, 4.68%. Incase of strength properties using different dossage of TerraZyme (3.0m3/200ml ; 1.5m3/200ml ) Venika Saini ; Priyanka Vaishnava (2015) concluded that CBR value get increases by 3.65% ; 15.87%. Using geotextlie with different dossage of Terrazyme (200ml/3m3 ; 4ml/5kg ) Gayatri Nair and Shyla Joseph (2016) concluded that CBR and UCS values get increased to 6.68% and 36.85% , 6.73% and 166.58%. Itthikorn Phummiphan et al.(2015) used high calcium fly ash(FA) based geopolymer in LA soil where increasing in UCS values found out to be 128.8% for 7-90 days curing period. Saroglou I. Haralambos (2013) used Portland cement (CEMII/ B-M (P-L) 32.5 N) which is mixed with different proportions in different type of soil such as CL, ML, SM, GPGM, GC it was noticed UCS values get higher percentage increase for different types of soil by using 7% of cement as compare to 3% of cement.

Conclusions

Author Name
Type of Soil
Methodology
Dosage
Index properties of treated soil
Strength properties of treated soil

Puneet Agarwal, Suneet Kaur (2014)
Black cotton soil.
Bio-Enzyme (TerraZyme)
0.25ml/5kg
4ml/5kg
UCS
UCS
20.27%
6.52%
Shankar et al. (2009) Lateritic soil Bio-Enzyme (TerraZyme) 0.029ml/kg

0.050ml/kg
LL
PL
LL
PL -4.33%
-0.4%
-6.67%
-4% CBR
UCS
CBR
UCS 35.29%
118.05%
24%
84.71%
Venika Saini, Priyanka Vaishnava (2015)

Clayey silt(CM) Bio-Enzyme (TerraZyme)

3.0m3/200ml

1.5m3/200ml LL
PL
LL
PL -10.71%
-8.82%
-21.15%
-4.68%
MDD

MDD 3.65%

15.8% CBR

CBR
3.65%

15.87%

Author Name
Type of Soil
Methodology
Dosage
Index properties of treated soil
Strength properties of treated soil

Gayatri Nair and Shyla Joseph (2016)
Silty Clay (CH-MH)

Bio-Enzyme (TerraZyme) with Coir geotextile.
200ml/3m3

4ml/5kg


CBR
UCS
CBR
UCS
6.68%
36.85%
6.73%
166.58%

Jyoti S.Trivedi et al.(2013)

Fine grained organic soil(OH)
Using Fly Ash in Sub-grade stabilisation.

Fly Ash LL OMC MDD
CBR
CBR
4.87%
4.93%
10%
20% 1.9%
5.04% 7.89%
3.86%
-2.13%
0%

Author Name
Type of Soil
Methodology

Index properties of treated soil
Strength properties of treated soil

Itthikorn Phummiphan et al.(2015)

Lateritic Soil
Using high calcium fly ash(FA) based geopolymer in LA soil.
The optimum (Na2SiO3:NaOH) ratio exhibiting the highest ?dmax is found 20.21 kN/m3.
UCS(7-90 days)
128.8%
increases

Saroglou I. Haralambos (2013)
CL, ML, SM,
GP-GM, GC
Portland cement (CEMII/ B-M (P-L) 32.5 N) is mixed with different proportions in different type of soil.
Strength properties of treated soil
UCS
Cement % 3% 7%
CL
ML
SM
GPGM
GC 39.13%
61.54%
21%
101.92%
68.35%
28.37%
50.64%
21.28%
37.73%
-1.92%

References
1.Puneet Agarwal, Suneet Kaur. (2014). Effect of bio-enzyme stabilization on unconfined compressive strength of expansive soil. International Journal of Research in Engineering and Technology, Vol. 03, pp. 30-33.
2.A. U. R. Shankar, H. K. Rai, R. Mithanthaya. (2009). Bio-enzyme stabilized lateritic soil as a highway material. Journal of the Indian Roads Congress, pp. 553.
3.Gayatri nair s, Shyla joseph a, (2016). Effect of bio enzyme and geotextile on strength characteristics of sub grade soil. International Research Journal of Engineering and Technology, Vol. 03, pp. 1891-1897.
4.Venika Saini, Priyanka Vaishnava. (2015). Soil stabilization by using TerraZyme. International Journal of Advances in Engineering ; Technology, Vol. 08, pp. 566-573.
5.I. Phummiphan, S. Horpibulsuk, P. Sukmak, A. Chinkulkijniwat, A. Arulrajah, S.L. Shen. (2015). Stabilization of marginal lateritic soil using high calcium fly ash-based geopolymer. International Journal of Research in Engineering and Technology, Road Materials and Pavement Design, pp. 01-15.
6.Jyoti S.Trivedi, Sandeep Nair, Chakradhar Iyyunni. (2013). Optimum Utilization of Fly Ash for Stabilization of Sub-Grade Soil using Genetic Algorithm. SciceneDirect, Vol, 51. pp. 250-258.
7.Saroglou I. Haralambos. (2013). Compressive Strength of Soil Improved with Cement. International Foundation Congress and Equipment Expo Contemporary Topics in Ground Modification, Problem Soils, and Geo-Support, ASCE.
8.

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