WO2018090105A1

WO2018090105A1 - Soil stabilizing composition

Info

Publication number: WO2018090105A1
Application number: PCT/AU2017/051278
Authority: WO
Inventors: Michael Harvey
Original assignee: OFB Soil Binder Pty Ltd
Priority date: 2016-11-21
Filing date: 2017-11-21
Publication date: 2018-05-24
Also published as: AU2017361990A1

Abstract

The invention resides in a soil stabilizing composition comprising: a first polymer that comprises an acrylamide monomer; a second polymer that comprises an acrylate monomer; and a solvent; wherein the first polymer and second polymer directly cross-link to stabilize a soil substrate. The invention also resides in a method of stabilizing a soil substrate including the steps of: providing a soil stabilizing composition comprising a first polymer that comprises an acrylamide monomer, a second polymer that comprises an acrylate monomer, and a solvent; treating the soil substrate with the soil stabilizing composition; and curing the soil stabilizing composition; wherein the first polymer and second polymer directly cross-link to stabilize the soil substrate.

Description

SOIL STABILIZING COMPOSITION

FIELD OF THE INVENTION

[0001 ] The present invention relates to the field of construction. More particularly, the present invention relates to soil stabilization. Most particularly, the present invention relates to a soil stabilizing composition.

BACKGROUND TO THE INVENTION

[0002] Roads and pavement play an important role in the operation of an economy. Roads are required in the production, distribution, trade and consumption of goods and services. The lifetime and cost of roads impact on their economic viability. In this regard, the composition and characteristics of soil can have a significant impact on roads and/or infrastructure placed thereon.

[0003] Soils are usually classified by particle size, and range from fine- grained, high expansion clays and silts to large rocks. Dislocation and diminution of particles or of particle agglomerates are the primary cause of deterioration of natural soils and man-made structures placed thereon. As such, the stability of soil can have a significant impact on the lifetime and cost of roads and infrastructure. [0004] In order to alleviate this problem, soil can be treated so that it is embedded in a matrix, or confined mechanically, or compacted into an interlocking arrangement that holds the particles together.

[0005] One common solution is to utilize asphalt, concrete or other road binders. However, it will be appreciated that these materials are expensive and may not be commercially feasible, particularly in areas where there is low traffic volume. [0006] Another method is to use bonding agents which agglomerate individual soil particles and hold them firmly in place to form cohesive structures. These structures are composed of individual particles which are interlocked mechanically into coherent bodies with a bonding agent so that they resist displacement when exposed to forces such as mechanical abrasion and erosion. These forces can destroy the coherence of these bonded structures. Many attempts have been made to create bonding agents that take into account different soil properties. One such attempt was to combine different bonding agents. However, the desired combination of effects could not be achieved by using mixtures of individual components because soils can have a preferential affinity for different compounds.

[0007] Other attempts to solve this problem have been focused on the use of polymer/monomer blends as aqueous or petroleum dispersions, often in combination with asphaltic mixtures. These blends often require elevated temperatures or have specific constraints on the substrate. Additionally, these materials may also require additional time for curing, or have a severely limited lifespan. Another common problem with these blends is that they can separate into different phases.

[0008] One attempt to provide additional soil stabilization is described in US Patent Application No. 2014/0169879. This document utilizes co-polymers to provide improved subgrade soil binders. The co-polymer is produced from monomers of acrylamide, sodium acrylate and 3-acrylamido-N,N,N- trimethylpropan-1 -aminium chloride. The cationic aminium chloride functional group adsorbs to clays through electrostatic interactions. This copolymer is directed towards soils with high clay content, and is less suited towards soils with lower clay content.

[0009] It should be clear that it would be desirable to alleviate the abovementioned problems. Furthermore, it would be advantageous to provide a commercial alternative which can be used instead of the current expensive solutions and still provide high quality roads capable of sustaining traffic.

SUMMARY OF THE INVENTION [0010] In a first aspect, although it need not be the only or indeed the broadest aspect, the invention resides in a soil stabilizing composition comprising:

a. a first polymer that comprises an acrylamide monomer; b. a second polymer that comprises an acrylate monomer; and c. a solvent

wherein the first polymer and second polymer directly cross-link to stabilize a soil substrate.

[001 1 ] The first polymer may be a polymer that comprises acrylamide monomer. Preferably the first polymer is polyacrylamide.

[0012] The second polymer may be a polymer that comprises acrylate monomer. The second polymer may further comprise other monomers. Suitably the second polymer further comprises a styrene monomer and is preferably a styrene-acrylate polymer. [0013] The second polymer preferably has a minimum film forming temperature of less than about 10^QC, and most preferably the minimum film forming temperature is between about 0^QC and about 10^QC

[0014] The second polymer suitably has a glass transition temperature of greater than about 0^QC, preferable between about 5^QC and about 20^QC, and most preferably between about 8^QC and about 20^QC.

[0015] In one form the solvent is a polar solvent, which may be water.

[0016] In another form, the soil stabilizing composition may further comprise additives, which may be surface tension modifiers, adhesion promoters, cross- linking curing agents, stabilizers, colouring agents and preservatives. [0017] In one form, the first polymer is present in an amount between about 1 and about 10 parts per 10000 parts solvent. Preferably the first polymer is present in an amount between about 2 and about 5 parts per 10000 parts solvent.

[0018] In a preferred form, the second polymer is present in an amount between about 4 and about 40 parts per 100 parts solvent and preferably in an amount between about 8 and about 25 parts per 100 parts solvent. The second polymer is most suitably present in an amount between about 10 and about 16 parts per 100 parts solvent. [0019] In one form, the soil stabilizing composition provides an increase of suitably greater than a 5%, preferably greater than a 7%, and most preferably greater than 10% in the California Bearing Ratio (CBR) of a treated soil substrate compared to an untreated soil substrate.

[0020] In a second aspect, the invention resides in a method of stabilizing a soil substrate including the steps of:

a. providing a soil stabilizing composition comprising a first polymer that comprises an acrylamide monomer, a second polymer that comprises an acrylate monomer, and a solvent;

b. treating the soil substrate with the soil stabilizing composition; and c. curing the soil stabilizing composition,

wherein the first polymer and second polymer directly cross-link to stabilize the soil substrate.

[0021 ] The soil stabilizing composition is as described in the first aspect.

[0022] The soil substrate may be selected from the group consisting of asphalt grindings, coal dust, concrete grindings, ground glass, crusher dust, recycled bitumen, bull dust, bauxite dust, fly ash and expansive clays.

[0023] In one form, the method further includes the step of diluting the soil stabilizing composition with additional solvent.

[0024] In another form, the step of providing the soil stabilizing composition further includes the step of producing the soil stabilizing composition, and the method of producing the soil stabilizing composition includes the steps of:

a. dispersing a first polymer that comprises an acrylamide monomer in a solvent; and b. adding and dispersing a second polymer that comprises an acrylate monomer.

[0025] In one form, the method further includes the step of pre-applying a solution comprising a surface tension modifier. In one embodiment, the surface tension modifier is the first polymer.

[0026] The various features and embodiments of the present invention referred to in the individual sections above apply, as appropriate, to other sections, mutatis mutandis. Consequently features specified in one section may be combined with features specified in other sections as appropriate.

[0027] Further features and advantages of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, the invention will be described by way of example only with reference to the accompanying drawings, in which:

FIG 1 is an exemplary diagram of the soil stabilizing composition stabilizing a soil substrate.

DETAILED DESCRIPTION OF THE INVENTION

[0029] Embodiments of the present invention reside primarily in a soil stabilizing composition. Accordingly, the composition and method steps have been described with only the specific details that are necessary for understanding the embodiments of the present invention, so as not to obscure the disclosure with excessive detail that will be readily apparent to those of ordinary skill in the art having the benefit of the present description.

[0030] In this specification, adjectives such as first and second, at least, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Words such as "comprises" or "includes" are intended to define a non-exclusive inclusion, such that a composition or method that comprises a list of elements does not include only those elements but may include other elements not expressly listed, including elements that are inherent to such a composition or method. [0031 ] As used herein, the term 'about' means the amount is nominally the number following the term 'about' but the actual amount may vary from this precise number to an unimportant degree.

[0032] As used herein, the term 'soil' refers to the surface or ground in which roads and/or infrastructure is built upon, and includes top soil and subsoil. Additionally, the term 'soil' also relates to aggregates which are not limited to natural materials and may include asphalt grindings, coal dust, concrete grindings, ground glass, crusher dust, recycled bitumen and the like.

[0033] In a first embodiment, the invention resides in a soil stabilizing composition. The soil stabilizing composition comprises a first polymer that comprises an acrylamide monomer, a second polymer that comprises an acrylate monomer and a solvent. The soil stabilizing composition is advantageously able to provide stability to a soil substrate and is discussed in more detail hereinafter.

[0034] The first polymer is a polymer that comprises an acrylamide monomer. It will be appreciated that the first polymer may be a polymer produced from multiple monomers, wherein one of the monomers is an acrylamide monomer. In this regard, the first polymer may be a homopolymer or heteropolymer. In one embodiment, the first polymer is polyacrylamide. It will be appreciated that the first polymer may be an ionic polymer. In an embodiment, the first polymer is a cationic polyacrylamide polymer. The first polymer is suitably a cationic polymer of high molecular weight. The first polymer has a molecular weight of suitably between about 1 x10⁴ and about 1 x10⁹ Daltons, and more preferably between about 1 x10⁵ and about 1 x10⁸ Daltons.

[0035] The second polymer is a polymer that comprises an acrylate monomer. It will be appreciated that the second polymer may be a polymer produced from multiple monomers, wherein one of the monomers is an acrylate monomer. In this regard, the second polymer may be a homopolymer or a heteropolymer. Other non-limiting examples of monomers that can form part of the second polymer are styrene monomers, vinyl monomers, acetate monomers, ethylene monomers and combinations thereof. As such, the second polymer can be a styrene-acrylate polymer. It will be appreciated that the second polymer may be a non-ionic polymer. In an embodiment, the second polymer is non-ionic styrene-acrylate polymer.

[0036] The second polymer has a minimum film forming temperature suitably less than about 10^QC, and preferably between about 0^QC and about 10^QC.

[0037] The second polymer has a glass transition temperature suitably greater than about 0^QC, more suitably between about 0^QC and about 25^QC, preferably between about 0^QC and about 20^QC, more preferably between about 5^QC and about 20^QC, and most preferably between about 8^QC and 20^QC. [0038] The solvent may be any solvent in which the first polymer and second polymer can be dispersed. The solvent may be a polar solvent or a non-polar solvent. The solvent may suitably be water, an alcohol, a glycol, a glycol ether, an ester alcohol, a ketone or an aprotic solvent. Non-limiting examples of the solvent include water, methanol, ethanol, isopropanol, butanol, pentanol, 2,2,4- trimethyl-1 ,3-pentanediol monoisobutyrate and N-methyl-2-pyrrolidone. In one embodiment, the solvent is water. It will be appreciated that the solvent is not limited to pure solvents and can include a blend of one or more solvents. For instance, the solvent may be a mixture of aliphatic alcohols and water.

[0039] The soil stabilizing composition may further comprise additives. The additives can include surface tension modifiers, adhesion promoters, cross- linking curing agents, stabilizers, colouring agents and preservatives. It will be appreciated by the person skilled in the art that the list provided is not an exhaustive list, but merely exemplify some of the types of additives that can be utilized. These additives provide additional, or alter, characteristics of the soil stabilizing composition and thus the treated soil substrate. The additives are preferably dispersible in the solvent, are active at low concentrations and nontoxic.

[0040] The surface tension modifier can be ionic or non-ionic. Preferably, the surface tension modifiers are alkylphenol ethoxylate (APEO) free. APEO's have been linked to altering reproduction, feminization and lowering the survival rates in fish, and as such it is preferable to avoid their use. It will be appreciated that the type of surface tension modifier may be chosen based on the soil substrate that is to be stabilized.

[0041 ] The cross-linking curing agent increases the hardness of the substrate. Suitable cross-linking curing agents include aziridines, carbodiimides and metal salts. A non-limiting example of a cross-linking curing agent is zinc ammonium chloride.

[0042] It will be appreciated that the amount of solvent in the soil stabilizing composition depends on the amount of dilution required. In this regard, the soil stabilizing composition may be provided as a concentrate, where there is less solvent, or as a working soil stabilizing composition where there is more solvent. The concentrate and working composition are stable and easy to handle. In this regard, in one embodiment, the concentrate and working composition are non- corrosive. [0043] The concentrate may be transported on-site and diluted with a suitable solvent to form the working composition. The amount of diluting solvent required is determined by the amount of dilution required to form the working composition.

[0044] The working composition has the first polymer present in an amount suitably between about 1 and about 10 parts per 10000 parts solvent, more suitably between about 2 and about 8 parts per 10000 parts solvent, preferably between about 2 and about 6 parts per 10000 parts solvent, and most preferably between about 2 and about 5 parts per 10000 parts solvent. [0045] The working composition has the second polymer in an amount suitably between about 4 and about 40 parts per 100 parts solvent, more suitably between about 6 and about 30 parts per 100 parts solvent, preferably between about 8 and about 20 parts per 100 parts solvent, and most preferably between about 10 and about 16 parts per 100 parts solvent. It will be appreciated that greater amounts of the first polymer and second polymer can be used in the working solution but will obviously incur a greater cost.

[0046] It has been surprisingly found that aggregates used for road production mixed with the working composition, when dry, exhibit a significant increase in the California Bearing Ratio (CBR) compared to the untreated aggregate. The CBR is a penetration test for evaluating the mechanical strength of the ground beneath new roads and pavement. CBR measures the pressure required to penetrate the soil or substrate with a plunger of a standard area to a depth of 2.5mm and 5mm. The measured pressure is then divided by the pressure required to achieve an equal penetration in a standard crushed rock material. In summary, the higher the CBR the harder the surface. The standard material for this test is crushed California limestone which has a value of 100. The tests show that by blending the first polymer with the second polymer, it significantly increases (>10%) the CBR above the level of using the second polymer alone. Additionally, there is a significant increase in CBR over a significant range of substrates. This is an unexpected result because, at the levels used, the first polymer on its own displayed no significant increase in CBR compared to the untreated substrate. It should be clear that there is a synergistic effect in using the first polymer with the second polymer. This increase in CBR in the treated substrate is sufficient for roads and infrastructure to be built thereon. The present soil stabilizing composition offers additional strength and thus lifetime to the soil substrate. This is particularly advantageous to the resultant road or infrastructure built thereon. In one embodiment, the soil stabilizing composition provides an increase of suitably greater than a 5%, preferably greater than a 7%, and most preferably greater than 10% in the California Bearing Ratio (CBR) of a treated soil substrate compared to an untreated soil substrate. [0047] It is postulated that the first polymer has a synergist effect on the second polymer because the first polymer comprises at least one monomer comprising acrylamide and the second polymer comprises an acrylate monomer. It is believed that the amide group of the first polymer undergoes a condensation reaction with the carboxyl functional group to form a cross-link. In this regard, as the water evaporates or migrates away during the curing process, the loss of water results in the equilibrium of the reaction being shifted towards the cross- linked product. This reaction is non-reversible, in that if excess water is added to the crossed-linked product it does not fragment back to the first polymer and second polymer. As such, it is believed that the other functional groups that are compatible in this manner can be used.

[0048] Additionally, it is also postulated that, when the first polymer is cationic, the cationic charge causes the first polymer to be attracted to the surface of some soils. Clayeous surfaces typically have negatively charged sites and so the use of a cationic polymer can lead to an electrostatic interaction between the first polymer and the substrate. This promotes better adhesion and agglomeration of light particles such as dust. As such, the soil stabilizing composition can act as a dust suppressant. The improved bonding and lower micro particulate loading provides improved penetration and improved adhesion of the second polymer to the substrate in a stronger 'bond' which is less likely to de-lamination from the substrate.

[0049] FIG 1 shows a diagram of the postulated mechanism of soil stabilization. The soil is represented by the agglomerates in between the first polymer and the second polymer. The working composition is applied and allowed to permeate through the soil substrate. The working composition is then allowed to cure so that water evaporates or migrates away, and leads to a loss of water. The loss of water results in the equilibrium being shifted to the cross- linked product through a condensation reaction, and results in the soil being encapsulated in a matrix of the cross-linked polymers. [0050] The cross-linked polymers provide the structural integrity and mechanical strength required to build roads and/or infrastructure. It will be appreciated that the surface tension of the soil stabilizing composition will also affect the penetration of the working composition. It will also be appreciated that the relative simplicity of the first polymer and second polymer allows for the composition to be easily synthesized and easily modified to achieve the desired characteristics. In one embodiment, the first polymer and second polymer directly cross-link to stabilize the soil substrate. Directly cross-linking refers to the first polymer being directly bonded to the second polymer without an intermediate molecule or reagent. In a preferred embodiment, the amide functional group of the first polymer undergoes a condensation reaction with the carboxyl function group of the second polymer to form a N-acylamide bond (- C(O)NHC(O)-) that stabilize the soil substrate.

[0051 ] Once cured, the cross-linked polymer forms a matrix which provides additional mechanical strength to the soil substrate. The formation of the covalent bonds is particular strong and imparts significant strength and flexibility to the soil substrate. Additionally, as shown in FIG. 1 , a single polymer molecule can cross-link with multiple other polymer molecules leading to an intricate crosslinking network which provides flexibility and strength. This is a distinct advantage over stabilizing compositions which utilize a single polymer strand as they do not offer this flexibility and mechanical strength. [0052] The working composition has suitable processability which, when cured, has desirable high strength and flexibility characteristics over a wide temperature range.

[0053] In one embodiment, the soil stabilizing composition is environmentally friendly. In this regard, the first and second polymer can be chosen to minimize their environmental impact. Preferably, the first and second polymers are free of APEO and ammonia. Additionally, when applied, the soil stabilizing composition does not require external coalescing agents. Other additives are similarly selected to minimize the environmental impact. Once cured, the composition is inert and does not substantially degrade or release petroleum or asphaltic material. For instance, soil stabilizing composition does not require the use of polycations to achieve soil stabilization. In other words, the soil stabilizing composition does not comprise polycations.

[0054] Although, the soil stabilizing composition can be cured at ambient conditions, it will be appreciated that curing the soil stabilizing composition may be assisted by the application of curing conditions. Curing conditions include, but are not limited to, applying a dehydration agent and applying higher temperatures.

[0055] As previously mentioned, the CBR is an important test to determine the strength and flexibility of a substrate. In this regard, the working composition was applied to clayey gravel red brown laterite under laboratory conditions. In this regard, the CBR of the untreated clayey gravel red brown laterite is about 7. Typically, the target CBR is 100. It was found that the use of the abovementioned soil stabilizing composition increased the CBR to about 250 at 2.5 mm and about 310 at 5.0 mm. It should be apparent that the use of the present soil stabilizing composition resulted in a significant increase in CBR compared to untreated laterite.

[0056] Laterite is typically a very poor substrate to form roads and infrastructure upon, and typically has a low CBR. The abovementioned working composition was applied to a laterite substrate and tested to see its effect on the unconfined compressive strength. In this regard, the target compressive strength for the laterite was 5.0 MPa, and the laterite treated with the working composition achieved a compressive strength of 6.0 MPa. This result represents a significant increase in compressive strength through the use of the working composition. This increase in compressive strength indicates that a compaction that might require 500mm of material may only require about 50mm of material. This leads to a much more efficient method of treating the soil. This increase is a significant increase compared to industry standards.

[0057] This increase in compressive strength can result in 40% less maintenance, and increase the lifetime of the road and infrastructure built thereon. Additionally, the abovementioned working composition was applied to other soil substrates and resulted in increased strength in all cases. Tested substrates included crusher dust (fine and coarse), crusher dust and sand, decomposed granite, clay, crusher dust and recycled glass, quarry gravel, plumbers gravel, coal dust, recycled bitumen, sand, road base (river rock and clay), fly ash and a combination of granite, sand and clay. [0058] Additionally, another advantage of the present soil stabilizing composition is that the soil can be reused if cracked. In this regard, the cracked treated soil may be broken down and retreated with fresh soil stabilizing composition. This is advantageous when compared to other soil stabilization techniques, such as concrete. In this regard, cracked concrete must be removed once cracks appear so that a new layer of concrete can be put down. This is a costly and time consuming process.

[0059] Alternatively, cracked surfaces may be repaired by filling with fresh soil. In this regard, cracked surfaces or holes can be patched by simply filling the cracked surface or hole with new material and treating the new material with the soil stabilizing composition.

[0060] The soil stabilizing composition, as described hereinabove, can be used to stabilize a soil substrate. The soil substrate can be stabilized through treatment with the soil stabilizing composition and curing the treated substrate. The resulting treated soil substrate has desirable high strength and flexibility characteristics over a wide temperature range, and is stabilized such that road and pavement can be formed thereon.

[0061 ] As previously mentioned, the soil stabilizing composition may be in the form of a concentrate that needs to be diluted to form a working composition. In this regard, the soil stabilizing composition may require dilution with a suitable solvent.

[0062] The soil substrate can be treated with the working composition in any manner known to the person skilled in the art. In this regard, the soil stabilizing composition can be mechanically mixed into the soil substrate, or alternatively be sprayed onto the soil substrate and allowed to penetrate through the soil substrate. [0063] Additionally, the soil stabilizing composition may further be applied as a top coat to the soil substrate. The inventors have found that fine dust-like soil substrates may repel water for a significant amount of time before the surface tension is broken and the working composition can penetrate through the substrate. For instance, coal dust and bull dust are significantly hydrophobic and exhibits slow wetting time when sprayed with water. The average wetting factor for coal dust can vary with a number of factors including: coal type, particle size of the dust, level of entrained inorganic material, phenolic hydroxyl content on the coal dust surface, and carbon content in the coal dust. [0064] In one embodiment, the method of stabilizing a soil substrate further includes the steps of pre-applying a solution comprising a surface tension modifier. In one embodiment, the surface tension-modifier is the first polymer. It has been found that an additional step of pre-applying a solution comprising the first polymer can reduce the surface tension of fine dust-like soil substrates. It is postulated that the pre-application neutralizes the surface charge on the fine dust-like soil substrate and collapses the dust-like substrate. As such, the density of the fine dust-like soil substrate increased and less volume of working solution is required. Furthermore, it is postulated that the pre-application assists to consolidate and aggregate the dust onto larger clusters which makes the resultant stabilized soil more stable. This additional step allows the working composition to more efficiently penetrate and stabilize the soil substrate. It will be appreciated that if the soil stabilizing composition does not penetrate into the soil substrate then a layer of soil stabilizing composition may be formed on the surface of the substrate. [0065] The inclusion of the step of pre-applying a solution comprising the first polymer alleviates this problem. Furthermore, the addition of extra first polymer in this pre-application step provides further amide functional groups to crosslink/bond with the carboxyl functional groups of the second polymer when it is applied with the soil stabilizing composition. As such, it is postulated that the additional first polymer further assists in stabilizing the soil substrate. [0066] It is postulated that the combination of the solution comprising polyacrylamide and then the soil stabilizing composition forces the latex emulsion to separate, forcing de-emulsification of the latex and rapid formation of a cohesive layer which binds the dust. Furthermore, this additional step appears to create cross-linking in the mass which is both long lasting and resilient. This result is not observed in either polyacrylamide or the soil stabilizing composition alone. It is postulated that the polyacrylamide may reduce water evaporation and thus prolong the contact between the dust-like particles and the water.

[0067] The first polymer is as substantially described hereinabove. Non- limiting examples of the dust-like substrate includes bull dust, bauxite dust and fly ash.

[0068] The soil stabilizing composition can be produced by first dispersing a first polymer that comprises an acrylamide monomer in a solvent; and adding and dispersing a second polymer that comprises an acrylate monomer. [0069] The first polymer may be provided as a polymer emulsion. The first polymer may be added to a solvent and dispersed to form a mixture. The second polymer may also be provided as a polymer emulsion. The second polymer may then be added to the mixture and dispersed to provide the soil stabilizing composition. [0070] As mentioned hereinabove, the soil stabilizing composition can be a concentrate or a working composition. As such, the soil stabilizing composition can have different amounts of solvent. In order to dilute the soil stabilizing composition, additional solvent can be added at any stage to form the soil stabilizing composition with the desired concentration. [0071 ] As previously mentioned, the soil stabilizing composition may further comprise additives. In one embodiment, the production of the soil stabilizing composition further includes a step of adding and dispersing an additive or additives. [0072] Dispersion can be performed in any disperser known in the art. The dispersion is suitably completed at above about 500 rpm, more suitably between about 2000 rpm to about 10000 rpm, preferably between about 4000 rpm to about 8000 rpm, more preferably between about 5000 rpm and 7000 rpm, and most preferably about 6000 rpm.

[0073] It should be appreciated that the present soil stabilizing composition is easily manufactured, imparts high compressional strength, high toughness, moderate tensile modulus and relatively low elasticity to the soil substrate so that roads and infrastructure can be built thereon. The present soil stabilizing composition offers a commercial alternative that can be used instead of expensive materials. This is particularly desirable in areas where there is little traffic volume.

Examples

Pre-application of a solution comprising the polyacrylamide [0074] A solution of polyacrylamide in water was first added to the coal dust which assists in breaking the surface tension thereof. Once the polyacrylamide has penetrated throughout the coat dust, it is left for up to an hour. A working solution of the soil stabilizing composition is then applied at a ratio of between 2:1 and 50:1 (soil stabilizing composition : polyacrylamide solution) and mixed in. The ratio is selected based on the specific application and the degree of permeability desired ranging from very low permeability to quite permeable. Binding of the coal dust particles is essentially immediate and complete.

[0075] The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this invention is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

Claims

A soil stabilizing composition comprising:

a. a first polymer that comprises an acrylamide monomer;

b. a second polymer that comprises an acrylate monomer; and c. a solvent,

The soil stabilizing composition of claim 1 , wherein the first polymer is polyacrylamide.

The soil stabilizing composition of claim 1 or 2, wherein the second polymer further comprises other monomers selected from the group consisting of vinyl monomers, acetate monomers and ethylene monomers.

The soil stabilizing composition of claim 3, wherein the second polymer is a styrene-acrylate polymer.

The soil stabilizing composition of any one of the preceding claims, wherein the second polymer has a minimum film forming temperature of less than about 10^QC, or between about 0^QC and about 10^QC

The soil stabilizing composition of any one of the preceding claims, wherein the second polymer has a glass transition temperature of greater than about 0^QC, or between about 5^QC and about 20^QC, or between about 8^QC and about 20^QC.

The soil stabilizing composition of any one of the preceding claims, wherein the solvent is selected from the group consisting of water, methanol, ethanol, isopropanol, butanol, pentanol, 2,2,4-trimethyl-1 ,3- pentanediol monoisobutyrate and N-methyl-2-pyrrolidone.

The soil stabilizing composition of any one of the preceding claims, wherein the solvent is water.

9. The soil stabilizing composition of any one of the preceding claims, further comprising surface tension modifiers, adhesion promoters, cross-linking curing agents, stabilizers, colouring agents and/or preservatives.

10. The soil stabilizing composition of any one of the preceding claims, wherein the first polymer is present in an amount between about 1 and about 10 parts per 10000 parts solvent, or between about 2 and about 5 parts per 10000 parts solvent.

1 1 . The soil stabilizing composition of claim 1 1 , wherein the second polymer is present in an amount between about 4 and about 40 parts per 100 parts solvent, or between about 8 and about 25 parts per 100 parts solvent, or between about 10 and about 16 parts per 100 parts solvent.

12. The soil stabilizing composition of any one of the preceding claims, wherein the soil stabilizing composition provides an increase of suitably greater than a 5%, or greater than a 7%, or greater than 10% in the California Bearing Ratio of a treated soil substrate compared to an untreated soil substrate.

13. A method of stabilizing a soil substrate including the steps of:

14. The method of claim 13, further including the step of diluting the soil stabilizing composition with additional solvent.

15. The method of claim 13 or 14, wherein the step of providing the soil stabilizing composition further includes the step of producing the soil stabilizing composition.

16. The method of claim 15, wherein the step of producing the soil stabilizing composition includes the steps of:

a. dispersing the first polymer; and

b. adding and dispersing the second polymer.

17. The method of any one of claims 13 - 16, further including the step of pre- applying a solution comprising a surface tension modifier.

18. The method of claim 17, wherein the surface tension modifier is the first polymer.

19. The soil stabilizing composition or method of any one of the preceding claims, wherein the soil substrate is selected from the group consisting of asphalt grindings, coal dust, concrete grindings, ground glass, crusher dust, recycled bitumen, bull dust, bauxite dust, fly ash and expansive clays.