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ISS 2500 Ionic Soil Stabilizer is a water-soluble chemical used in the construction of all types of roads utilizing in-situ materials.

It is 100% organic and is derived from combined organic sulfur and buffered acids that are combined as bi-soleplates. ISS is a true catalyst, it is not consumed in its function but continues and perpetuates its action as long as water is present.

ISS is an economical construction method for all type of roads, parking areas, by-passes, airfields and foundations. Stabilizing with ISS improves the physical and mechanical characteristics of soils. Field and laboratory tests show that the increase found in layer strength is not only due to compaction, but is also due to the improvement of material properties such as PI, grading modulus and linear shrinkage.


                 alt             alt

                     Before treatment                   After treatment with ISS 2500


ISS permanently alters the soil allowing maximum compaction and preventing the reabsorption of water. Treatment with ISS releases the absorbed water from the soil particles, minimizing the voids and allowing the particles to be compacted to much greater densities thereby increasing the shear strength and bearing capacity of the layer.

Treatment with ISS is permanent and the compacted layer has a high density and high load bearing capacity and is unaffected by extreme climatic conditions.


ISS is used in base, sub-base and sub-grade materials.

With ISS you can achieve the required density with soil that is normally discarded. There is no need to strip and haul this material way. The expense of removing materials and replacing them with costly borrowpit materials can be completely avoided when using ISS.

Therefore on average, uo to 75% of the cost of road construction  by methods hitherto employed ( i.e. without ISS ) can be saved.

This means that, instead of building 1 km of road ( or similar paved surface ) you can now, for the same money, build 2, 3 or even 4 km with ISS!



ISS works with most soils encountered in road construction but soil testing is reccommended. ISS works in soil types: A-2-4, A-2-6, A-4, A-5, A-6 and A-7. In Addition, the soil should have a PI with a minimum of 10% of the soil particles passing through the 0,075 mm (#200) sieve ( see Soils Table ).



This introduction is not intended as a detailed explanation but merely serves to give a fundamental understanding of ISS and the effect it has on a alarge number of soil types.

Soil stabilisation can be debided into four main classifications:

1    Physiomechanical   :   Compaction

2    Granulometric           :   Mixtures of Soil

3    Physiochemical        :   Cement, lime, asphalt

4    Electrochemical        :   ISS 2500 Ionic soil Stabilizer


Action of ISS on soil particles

The fine particles of clays and silts, due to their mineralogical composition have an excess of negative ions ( anions ) and therefore attract positive ions ( cations ) of water, making this water adhere to them to form pellicular water. This clay is unsuitable for construction as the adsorbed water acts as a lubricant on the soil particles thus preventing compaction of the soil.

ISS, by its chemical composition, has an enormous potential ionic exchange capacity. When small quantities of ISS are added to water, they activate the ions H+ and (OH )-, ionising the water which them vigorousl exchanges its electrical charges with the soil particles forcing the pellicular water to break its electrochemical bond with the soil particles to become free water which can then drain from the soil through gravity or evaporation.

This electrochemical reaction of ionic exchange is permanent and irreversible.

Once the pellicular water separates from the fines in an irreversible  electrochemical process and drains as free water, the soil particles settle and align themeselves in such a way that they attract each other. A higher densification of the soil mass is achieved eliminating all the voids.*



 Equipment Required

Grader ( with sacrifice or ripper )                                                                                                           Compactor ( 10 ton )

Water Truck                                                                                                                                                Disc plough, rotavator ( optional )


Water / ISS volume calculations


Calculate the totaal area to be staabilised with ISS giving the total m² to be treated.


ISS is applied together with the water required to bring the material to optimum moisture content. About 0, 5l for   every 1cm of dept per m² is required but may vary according to the material's in-situ moisture content and weather conditions. If the material is already at or above optimum, a minimum of 1l/m² of water must be used.


       Standard application rate for ISS is 0.03l per m²

        The are in m² is multiplied by the ISS application rate to give the quantity of ISS required.

        Example:     Area to be stablished      7,000m²

                              ISS application rate      0, 03 l/m²

                              7,000m²x0,03l/m² = 210l ISS


4     MIXING

The total amount of water required to bring the material to optimum moisture is devided by the capacity of the water truck to estimate the total number of water loads required. The quantity of ISS required is then devided into this total number of water loads. It is advisable to only add the  ISS to the first two-thirds of the required water loads.

Note:     If optimum moisture content is obtained before the last load of ISS mixture has been applied, the excess load should be applied during or after compaction. If however optimum content has not been obtained after the last load of ISS mixture has been applied, clean water without ISS must be used.                



                                                 Step 1: Rip / scarify

  A motor grader is used to prepare the area to be  stabilized by ripping the road to the required depth( 150-200mm ). All clods should be broken to +/- 50mm using the grader' blade or the disc plough.




                                       Step 2: ISS application

 ISS is applied together with the water needed to bring the road up to optimum moisture content for compaction using a standard water Bowser.

  The ISS solution should be applied in multiple passes of the water truck. If more moisture is needed after all the ISS has been applied, clean water should be used. If the material is already at or above optimum, a minimum of 1ℓ/m² of water be used.




                                                                                              Step 3: Mixing

  Between and after spraying, the material should be mixed using a grader or disc plough until an even moisture content is achieved. This can also be achieved with a grader using the window method. There are no time constraints when establishing with ISS. If rain or machine stoppage is        experienced, simply bring the material back to optimum moisture content and continue constructing.




                                                             Step 4: Shaping

Once the correct moisture content has been achieved, the road is shaped or cambered as required, allowing for proper drainage.




                                                                 Step 5: Compacting

The road is compacted to the required density using preferably a vibratory compactor. Plain water may be used to maintain the surface moisture if necessary.




                                  Step 6: The finished road

 The finished road should be lightly watered twice daily for two to three days after completion or until covered. The ISS- treated road may be opened to traffic immediately.




                                     Step 7: Sealing the road

       If desired, a sealant or subsequent layer can be placed directly on the ISS – treated surface.




                                Appearance of the road after

                                    application of ISS 2500®


     An ISS-treated road may. Several days after final compaction and watering, produced a surface best described as having crocodile skin-like cracks. These cracks are normal and necessary to allow the escape of air, water vapor and gases. If the road surface is not primed or covered, these cracks will heal with time and traffic.




How ISS functions as an ion exchanger and how it acts upon colloidal particles during application

In general oil mechanics, it is usual to draw a distinct between two phenomena of water: static in water and water in motion. The later in particular ( where the motion is caused by penetration or by the action of gravity ) greatly helps accelerate many reactions initiated by treatment with ISS. Static water, though it does not move under the actions of gravity, is nevertheless not completely motionless. Generally speaking, the motion caused by osmotic forces or molecular movement is very slight but, over a long period of time, considerable masses of water may nevertheless be transported as a result of this - either as a liquid or as a gas ( evaporation) . Static water remaining in the soil can be subdevided into four categories differing from one another chiefly in the order of magnitude of the force with which they adhere to the soil particles.

With the exception of chemically combined crystalline water, all the above -mentioned types of water are involved in the ISS reaction process. Since the main function of ISS is to reduce the amount of water held in the soil in order to form voids for optimum compaction and, alternatively, to decrease the swelling capacity of the individual soil particles, the characteristics of these various categories of water in the soil now be briefly discussed.


Chemical Water

This water, which is incorporated in the crystal structure and thus chemically combines with the soil minerals, forms only a very minor proportion of the water in the soil. It cannot be expelled from it by drying with temperatures above 110^oC. From the technical construction point of veiw, this water can be regarded as an integral constituent of the soil itself and can be ignored in construction.


Adsorbed Water

Water adhering to the surface of the soil particles can be partly, but not entirely, driven out by drying in an oven. When soil dried in this way is allowed to cool, it will reabsorb water in amounts dependent on the humidity of the ambient air.


Water held by surface tension

Most of the water reatined in soils is derived from water which has been held by surface tension at the points of contact between particles or which otherwise can move as pore water or as free water in the capillaries and larger voids.


Capillary water

This is water lodged in the pores between the soil particles; it can be partly or entirely removed by seepage, evaporation or water extraction with suitable equipment.

The most difficult problem is raised by the adsorbed water which adheres to the whole surface of the soil particle and almost forms part therof. This film of water enveloping the particle, which untimately governs the expansion and shrinkage of colloidal soil constituents, cannot be completely eliminated by purely mechanical methods. However by means of temperature effects and the addition or removal of water with mechanical pressure, it is possible to vary the amount of water held in this manner. Such variations are attended by swelling or shrinkage. This provides an ideal point of operation for ISS. To obtain a better understanding of this, the principle on which the action of ISS is based will be explained. In this context, the electrostatic characteristics of soil particles will also have to be considered. As a result of  a lowering of the dipole moment of the water molecule, there occurs association into an hydroxyl ( - ) and a hydrogen ( + ) ion. The hydroxyl ion in turn dissociates into oxygen and hydrogen, while the hydrogen atom of the hydroxyl is transformed into a hydronium ion. The latter can, in the nascent state, accept or reject positive or negative charges, according to circumstances.

Normally , the finest colloidal particles of soil are negatively changed. The envoloping film of absorbed water contains a sufficient number of positively charged metalions - such as sodium, potassium. aluminum and magnesium - which ensure charge equalisation with respect to the electrically negative soil ion.


Absorbed or hydroscropic water

Absorbed or hydroscopic water is, as already stated, mainly responsilble for the swelling and shrinking properties of soils. A soil particle comprising only chemically combined water swell, ( i.e.)  it cannot alter its structural density. Only the film of absorbed water adhering firmly to the particle surface can expand in volume as a result  of further water absorption when the soil is wetted. This effect is more particularly is prominent in fine- grained soils, such as clays. Since this absorbed water is held in a "stable" form on the clay particles, thickening of this water flm will involve a displacement of the centres of the particles toward one another with the over all effect that the volume of the mass of soil increases. Therefore, in order to achieve the densest possible packing of the clay particles to obviate the undesirable swelling and shrinking behaviour of such soil, it is necessary merely to reduce the thickness of the water film ( which, as has already been pointed out, is held very firmly to the particles) or to break the  film. The only possible way to this economically and permanently is by ion exchange. Because of its electrokinetic properties, the ISS solutions acts upon the positive and the negative charges of the soil particles. The effects of this action are threefold.

1. The film of the absorbed water is greatly reduced and in facat entirely broken.

2.  The soil particles acquire a tendency to agglomerate.

3.   As a result of the relative movement, the surface area is reduced and less absorbed water can be held

      therby, so that this in turn reduces the swelling capacity. Moreover, these three factors facilitate to com

      paction of the soil or indeed make it in fact possible.

In bringing out this phenomenon, the positive charges of the hydronium ion or of the negatively charged hydroxyl ion will normally combine with the positive charge to excert adequate pressure on the possitively charged metal ions in the absorbed water film. As a result of this, the existing electrostatic potential barrier is broken. When this reaction occurs, the metal ions migrate into the free water which can be washed or removed by evaporation. Thus the film of absorbed water enveloping the particles is reduced. The particles therby lose their swelling capacity and the soil as a whole acquires a friable structure. This is an irreversible process.

 The hydrogen ions which are liberated in the dissociation of the water molecules can once again react with free hydroxyl ions and form water along the gaseous hydrogen. It is important to note that the moisture content of the soil affects the surface tension and is thus a factor affecting compaction.

It should furthermore be pointed out that dry soil is poorly suited for compaction only because of the surface tension of the water contained in it. This is the reason why a certain total quantity of ISS solution is necessary for processing the area of ground in question. This is important, for if less than the total required quantity of solution applied, its penetration into the ground will be adversely affected. These two phenomena  ( gas and water formation and surface tension ) can be reduced by an increase in moisture content.

If the forces involved are reduced as a result of increase moisture content, the ISS solution can penetrate more easily into the capillary structure of the soil and the ion exchange process can take place more rapidly. The water released in consequence can therfore either seep away or be expelled by the kneading action of, for instance, a sheepsfoot roller and then evaporate at the surface. ISS therfore creates favourable conditions for compaction by changing the zeta potential of the clay and silt particles.

The zeta potential ( electrokinetic potential ) decreases with increasing concentration of the ions of opposite charges from the ISS solution. The cations and anions are liberated fron the diffuse double layer, which reduces the swelling properties of the soil.

The shrinkage time diagram clearly shows a kind of wastooh patern with the teeth deminishing to zero in course of time. It thus appears that, when water is added after shrinkage has occured, the shrinkage decreases to an amount corresponding to the amount of capillary water that has emerged. If the soil is allowed to dry again so that the water evaporates from it, the shrinkage that will then occur will never be quite as great as it is was previously. This accounts for the fact that surface treated with ISS solution and left uncovered will always increase in stability over a prolonged period of time.

The most notable properties of ISS and their effects on the soil therefore are:

1.  Reduction of the dipole moment which has a water repelling effect on the individual soil particles and at the same times reduces the swelling capacity.

2. The electrokinetic phenomenon causes the stabilisation of the soil particles. As a result, the soil acquires higher shearing strenght and its compatibility is significantly improved. In general, the soil particles align themeselves parallel to one another and, because of the formation of an electrical cushioning, causes a sliding effect that takes place in the horizontal molecular structure.

3.  Broadly speaking, a soil collodial character has a structure comparable to a house of cards. Because of this, the soil can contain a fairly large amount of voids which are filled either with water or with air. During treatment of ISS, these voids must be in any case be filed with pore water derived from the static water. Only in this way can ion exchange by higher valency cations take place and the dipole moment of the soil particles be reduced.

When the reaction has occured, less water can accumulate in the soil than was originally possible. As a result, the swelling capacity is reduced and the internal moisture of the soil is reduced.

Subsequent additions of water cannot reverse this process and once the latter has been accomplished, the swelling capacity is destroyed and the shearing strenght is increased.

For the processing solution to function correctly, the minimun requirement is that the soil should have optimum water content. A slightly higher water content will intesify the reaction but on no account must the amount  of water in the soil approach the saturation limit for this will result in the reduction in penetration power and the effectiveness of the process. A further problem that can arise if the soil water content reaches saturation is that the surface of the ground becomes sealed off by the original swelling effect.



Plasticity Index is used to described the condition wher clay exist. It is common practise to discard densely graded bases with a PI in excess of 6. There are some exceptions to the rule that the higher the PI of the clay, the more difficult it is to stabilize. However, it is almost universally believed that clays can only be improved by reducing the plasticity index.

In order to understand PI, let us define it. Plastic Limit denotes the percentage of moisture by weight that must be added to dry clay in order to cause it to begin to lose its coefficient of friction and, instead, to be bound together by the cohesiveness of thin films of water. Liquid limit is the percentage of moisture that must be added to dry clay in order to cause it to flow at a certain rate because of the increased thickness of the water film between adjacent soil particles. The differnce between them is the plastic index.

It should be borne in mind that only clays on or near the surface of the earth are free to exhibit these characteristics. When under compression, because of other soil, base material, paving or over burden, or because of mechanical compactive effort, or both, clay cannot absorb much water in excess of that required to fill the voids that exist  between the particles. Therefore except for those clays found on the shoulders and slopes and in that ditches along the right- of- way, clay that is normally encounterd during road buildings operations is not subject to the physical laws by which plasticity index is determined.

PI is usually reduced by ading sand or other granular material, lime or cement. While some chemical reactions do occur in the soil when lime or cement is added, they perform essentially the same function as sand, that of reducing the proportion of the particles possessing colloidal or surface active characteristics. Finely divided clays have both. Sand has either.

Lime or cement must be added to clay at a rate of atleast 6% by weight if significant practical results are to be obtained. Often higher rates needed, and there are clays that cannot be satisfactorily stabilized regardless of the amount used.

Where sand or other granular material is used, the amount added must be from a minimum of 10 to as high as 50%. These massive quantities of lime, cement or sand increase bearing values and improve the internal drainage of the clay. While PI is also reduced, It is actually only a measuring guide. It is the fact that bearing values are higher and that internal drainage is improved so that soft spots and frost lensing do not occur.

There are some chemical formulae that will reduce PI drastically. Unfortunately, they also reduce the bearing values of clays. To use a chemical that would reduce the PI of a clay form 20 to 60 while also redusing the CBR from 10 to 5 would obviously be foolish. Therefore, the statement that is sometimes made in regard to clay that the only thing of importance is to reduce the PI is completely unfounded.

ISS 2500 Ionic Soil Stabilizer will, when used in accordance with instructions increase the bearing values and reduce the moisture content permanently. It also, to some extent, reduces the PI. However, it should be kept in mind that, with this system of stabilization, it is possible to correct the problems of clays without reducing the PI to the same extent as would be necessary when using the other methods described above.

It has been said that, to treat a clay soil primarily for the purpose of reducing the PI, is like trying trying to cure a fever instead of the disease that is the cause. The afflictions of clays are low bearing values when wet and poor moisture equilibrum. When these are properly treated to the level required in base or subbase with ISS 2500, the plasticity index the results is only a static.