A MIXTURE FOR A ROAD FORMATION AND METHODS FOR BLENDING AND

COMPACTION THEREOF

Copyright Notice

This patent specification contains material that is subject to copyright protection. The copyright owner has no objections to the reproduction of this specification for the purposes of review, but reserves all copyright.

Field of the Invention

The present invention relates to construction base material and in particular to a mixture for a road formation and methods for blending and compaction thereof.

The invention has been developed primarily for use in road bases and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use, and may be equally be applicable to other applications also including open-cut mine roads, underground mine roads, railway formations, airport pavements, reservoir linings, dams and the like.

Background

Existing unbound granular road base construction materials fail on account of traffic induced stresses, a problem exacerbated by the ingress of water, resulting in premature failure, and expenses in maintenance rehabilitation and the like.

To attempt to reduce road construction, maintenance and rehabilitation, conventional pavement design requirements focus on the strength of the materials comprising road base construction. In this manner, road base materials exhibiting high-strength characteristics, such as materials excavated from virgin natural rock are employed. However, a disadvantage of utilising materials having high-strength characteristics is the expense wherein cheaper but generally inferior waste material is ill suited for use.

Furthermore, in obtaining high strength road bases, current road construction technique rely on the tight granular interlock of aggregate particles so as to provide not only strength and stiffness but also to allow the permeation of water therethrough to lower drainage layers.

However, disadvantages of relying on granular interlock for strength is the energy intensive compaction process wherein compaction passes of up to 20 are often employed to obtain the desired compaction required for tight granular interlock of the aggregate particles. Furthermore, during the compaction process, the road material must be wet to the optimum moisture content which not only wastes water but also wastes time during the requisite dry back waiting period. Furthermore, the additional water may serve only to weaken underlying layers through saturation.

Furthermore, granular interlock, while possessing high-strength and stiffness, is prone to the ingress of moisture which are adversely impact on the strength and stiffness and results in dilation and sheer failure.

Yet further, drainage away from the road base is often imperfect including at least on account of inferior drainage layers, buildup of fines material, blockage or drains, and the like. As such, existing granular interlock structures are often damaged by a buildup of water in the road base which weakens the shear strength of the road base.

Furthermore, to overcome problems of premature failure of unbound bases, engineers typically add bonding agents, binders (such as cement, stabilising binders or bitumen) to improve and increase the strength of base mixtures. However, there are disadvantages of increased expense, pavement cracking under stress, which again permit the ingress of water resulting in deterioration, and erosion of cracks by water (wetting and drying) and under hydraulic pressures caused by tyres hitting water in cracks during wet weather, and freeze/thaw and the like.

Furthermore, differing road authorities have differing specifications, tests and limits for these specifications resulting in non-uniform specifications for road materials across jurisdictions. As such, there is no uniformity in the materials used in all jurisdictions.

The present invention seeks to provide to a mixture for a road formation and methods for blending and compaction thereof, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary

According to one aspect, there is provided a mixture for a road formation comprising fines and aggregates, wherein the ratio of the fines to the aggregates is selected in accordance with a desired permeability.

Preferably, the ratio of fines to aggregate is selected in to reduce the permeability.

Preferably, the ratio fines is sufficient to as to substantially fill the aggregate interstices.

Preferably, at least the filling of the aggregate interstices effects the desired permeability.

Preferably, the desired permeability is less than 5 x 10 ^~8 ms ^"1 . Preferably, the desired permeability is less than 4 x 10 ^"8 ms ^"1 .

Preferably, the desired permeability is less than 3 x 10 ^"8 ms ^"1 .

Preferably, the desired permeability is less than 2 x 10 ^"8 ms ^"1 .

Preferably, the desired permeability is less than 1 x 10 ^"8 ms ^"1 .

Preferably, the mixture comprises greater than 7% minus 75μιη fines.

Preferably, the mixture comprises greater than 10% minus 75μηι fines.

Preferably, the mixture comprises greater than 12% minus 75μηι fines.

Preferably, the mixture comprises greater than 20% minus 75μηι fines.

Preferably, the aggregates type is selected in accordance with strength.

Preferably, the strength of the aggregates type selected has a strength beneath a threshold.

Preferably, the strength is a wet 10% fines value of less than 95kN.

Preferably, the strength is a wet 10% fines value of less than 70kN.

Preferably, the strength is a wet 10% fines value of less than 50kN.

[1 ] Preferably, the strength has a wet/dry variation of less than 35%. ()

[2] Preferably, the strength has a wet/dry variation of less than 45%.

[3] Preferably, the strength has a Los Angeles Test value of less than 50%.

[4] Preferably, the strength has a Los Angeles Test value of less than 40%.

Preferably, a plastic index of at least one of the fines and the aggregates type is selected in accordance with a plastic index threshold.

Preferably, the plastic index is beneath the plastic index threshold.

Preferably, the plastic index threshold is 6.

Preferably, the plastic index threshold is 12.

Preferably, the plastic index threshold is 20.

Preferably, the aggregates type is selected in accordance with a shape characteristic.

Preferably, the shape characteristic is a sphericity.

Preferably, the aggregates type is selected for asymmetry.

Preferably, the sphericity is greater than 35% by proportional calliper.

Preferably, the sphericity is greater than 35% by flakiness index. Preferably, t e ratio of the fines to the aggregates is selected further in accordance with a post-compaction aggregate compression state.

Preferably, the compression state is a tri-axial compression state.

Preferably, the ratio of fines to aggregates is selected to increase the tri-axial compression of the aggregate by the fines.

Preferably, the ratio of fines to aggregates is selected to decrease aggregate particle contact.

Preferably, the ratio of fines to aggregates is selected to decrease aggregate granular interlock.

Preferably, either the fines or aggregates contain a desired pH.

Preferably, the desired pH of either the fines or aggregates is greater than 8.

Preferably, the desired pH of either the fines or aggregates is greater than 9.

Preferably, the desired pH of either the fines or aggregates is greater than 10.

Preferably, at least one of the fines and aggregates selected in accordance with a desired moisture content.

Preferably, the desired moisture content is a maximum moisture content

Preferably, the maximum moisture content is adapted to maximise shear strength and substantially reduce hydraulic pore pressure during compaction

Preferably, the maximum moisture content is greater than 2% below optimum moisture content as determined by Proctor method.

Preferably, the maximum moisture content is greater than 3% below optimum moisture content as determined by Proctor method.

Preferably, the aggregates comprise at least one of coal washery rejects; quarried natural rock; quarry scalps; recycled brick and tile, crushed concrete, rock; sandstones; weak sandstones; shales, mine gangue and industrial aggregate waste.

Preferably, the fines comprise at least one of low grade material; waste material; recycled material and non-virgin excavated rock.

Preferably, the fines comprise at least one of fly ash; red mud; lime slurry; industrial slurry; bag house dust; mine tailings and incinerator dust.

According to another aspect, there is provided a road base comprising the mixture as described herein. According to another aspect, there is provided a method of blending a mixture for a road base, the method comprising blending material so as to provide a mixture described herein.

According to another aspect, there is provided a method of milling a mixture for a road base, the method comprising milling road base material in accordance with a desired moisture content.

Preferably, the mixture comprises fines and aggregates and wherein at least one of the type of fines and aggregates is selected in accordance with the desired moisture content.

According to another aspect, there is provided a method of compacting a road base comprising compacting a mixture as described herein.

According to another aspect, there is provided a method of compacting a road base comprising compacting a mixture having a moisture content of greater than 2% below optimum moisture content as determined by Proctor method.

According to another aspect, there is provided a method of compacting a road base comprising compacting a mixture having a moisture content of greater than 3% below optimum moisture content as determined by Proctor method.

According to another aspect, there is provided a method of compacting a road base comprising a compaction stage comprising less than 5 compaction passes and usage stage comprising vehicular traffic usage.

According to another aspect, there is provided a method of compacting a road base comprising a compaction stage comprising less than 2 compaction passes and usage stage comprising allowing vehicular traffic usage.

According to another aspect, there is provided a mixture for a road base, when placed in a 150mm thick layer wherein the mixture comprises a ratio of fines to aggregates and moisture adapted to achieve a density of greater than 98% standard compaction (Proctor) after the second compaction pass using a road roller of less than 20 tonnes in weight, but greater than 12 tonne in weight.

According to another aspect, there is provided a mixture for a road base, wherein the mixture comprises a ratio of fines to aggregates adapted to achieve a density of greater than 2.2 t/m3 after a first compaction pass using a road roller of less than 20 tonnes in weight. Other aspects of the invention are also disclosed. Brief Description of the Drawings

Notwithstanding any other forms which may fall within the scope of the present invention, a preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 shows a road formation in accordance with the prior art; and

Fig. 2 shows a comparison of prior art road formation materials and the mixture as per the embodiments of the present invention;

Fig. 3 shows a comparison of the resultant density of the compaction process and comparing prior art road formation materials and the mixture as per the embodiments of the present invention.

Description of Embodiments

It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

There will now be described a mixture for road base construction providing advantages, efficiencies, benefits and the like when compared to existing road base construction mixtures. Similarly, there will also be described methods of preparation of such a mixture, methods for the compaction thereof and road base constructions comprising such mixture.

It should be appreciated that the mixture will be described herein with reference primarily for use as road base construction but that the mixture should not be construed as being limited to this application. Specifically, the mixture may be equally suited for other construction application also including for the use in airport runways and pavements, mine haul roads and underground roads; layers beneath railway ballast and, at least on account of the low permeability of the mixture as will be described in further detail below, for reservoir construction waste repositories, landfall liners and capping, dam construction and the like. For ease of reference, the mixture according to the embodiments described herein will be referred to for convenience purposes as the "matrix mixture" so as to distinguish the matrix mixture from existing road base material wherein, as will be appreciated from the below description, the term matrix refers to one of the characteristics of the matrix mixture being the supportive and cushioning tri-axial compression of aggregates by fines providing the advantages, efficiencies, benefits and the like as described herein, such as reduced permeability.

Roadbase

It is well known that water ingress and the resulting increase in moisture content of the roadbase weakens the road structure. Specifically, roadbase material shear strength decreases as moisture content increases leading to deterioration of the road base structure, the fragmentation thereof and the like. As such, it is desirous to prevent water ingress of a road base construction from a durability perspective.

For example, on existing unbound granular road formations, the granular road base material beneath the wearing surface on sealed roads and at the surface for unsealed roads contains road base which can become water affected during in pavement life. The passage of vehicle wheels over a granular road base imparts the load through the roadbase to the layers below. If the roadbase becomes moisture affected, this load is transmitted to the moisture affected road base which has lower shear strength and pavement failure can occur through rutting and shoving.. If moisture content continues to increase high pore pressures can develop within the road base. High pore pressures and restricted drainage creates an upward pressure towards the surface and blowouts and potholes form at the surface.. The edges of the pothole can be further eroded as granular road base disappears from the crater. There are two failure mechanisms working here: 1 ) initial instability and increased deformation by shear as moisture increases; and 2) pothole blowouts as moisture increases further and excessive pore pressures develop.

According to existing arrangements, beneath the road surface, the road formation comprises a series of layers wherein the layers are intended possess increasing permeability downwards to be permeable such that any water entering the structure from the top is dispersed downwards away from the road base towards a bottom drainage layer from whence the water can be drained away so as to prevent the adverse effects of moisture and pore pressure on the sheer strength of the road base.

Specifically, conventional road bases comprise discrete particles of proportionally sized aggregates that are compacted such that the each aggregate particle interlocks with and bears against adjacent aggregate particles (granular interlock) so as to form a strong, relatively stiff, coherent layer that retains some permeability. Furthermore, the drainage layer of the road formation comprise aggregates and is designed to facilitate drainage of water down and away from the upper, higher stress layers of the road formation.

Specifically, referring to figure 1 , there is shown a prior art road formation 100 comprising a base 105 adapted to allow the permeation of water therethrough to a drainage layer 1 10. Also shown is the desired path 1 15 of such water drainage wherein ideally the water drains from the base 105 through to the lower drainage layer 1 10 and away from the road formation 100.

However, in practice for economy, inferior quality high fines and/orhigh plastic index and/or low permeability, cheaper subbase and drainage layer material is oftentimes employed which hinders permeation of water therethrough. As such, also shown is the practical path 120 of the water wherein the water cannot permeate through to the lower drainage layer 1 10. As such, the increased moisture at the road base 105 resulting in lower shear strength in subsequent deterioration thereof. Such a problem may be compounded by the abrasion of the aggregate material in the base 105 resulting in fines material falling downwards and filling the interstices of the lower drainage layer 1 10 further hindering the permeability of the drainage layer 1 10 by preventing the water from flowing between the coarse aggregates of the lower drainage layer 1 10.

Now, as will be described in further detail below, there will be described a road base comprising the matrix mixture such that, as opposed to being designed to allow the permeation of water therethrough, the road base comprising the matrix mixture is adapted to reduce permeability so as to prevent the ingress of water within the road formation the first place. In this manner, the water is dispersed laterally from the road surface as opposed to permeating therethrough.

In this manner, the matrix mixture advantageously substantially ameliorates ingress or eliminates water variation and increase or saturation within the road base so as to maintain the sheer strength of the road base and prevent the development of high pore pressures.

As will become apparent from the description below, the matrix mixture exhibits superior long term shear strength and low permeability by comprising a mixture of aggregates and fines wherein the fines are adapted to substantially fill the interstices between the aggregate material so as to prevent the permeability of water through the interstices of the aggregate material.

It should be noted that the term "fines", "microfines" and the like are used herein interchangeably and no particular technical limitations should be imputed thereto accordingly and the terminology should rather be construed in a purposive manner. However, in embodiments, the terms as used herein may infer particles sizes of less than 75 μηη. (75 micro or 75 μηη or 75 x 10 ^"6 m)

Such a matrix mixture further enhances the compaction process allowing greater compaction than when compare to existing road base material.

As such, using the matrix mixture, there is afforded a low permeability road base.

Furthermore, the fines of the matrix mixture is provided in sufficient quantities so as to reduce aggregate-aggregate granular interlock of the aggregate material. Such granular interlock provides the stiffness and strength of existing road bases. However, by the fines of the matrix mixture cushioning and supporting the granular material and substantially preventing the granular interlock, the matrix mixture further advantageously provides a cohesive road base which is resilience to shear and the like at least on account of heavy traffic, ground subsidence and the like. Conventional aggregate-aggregate interlock roadbase requires high strength/durability materials to prevent their breakdown over time, with the repeated traffic loading. The load is transmitted downwards from aggregate to aggregate, by the friction at the aggregate-aggregate boundaries, via pathways through the granular material. This repeated abrasion at the aggregate-aggregate particle interface causes breakdown and generates fines that block the interstices and reduce permeability. In matrix mixture the aggregate-aggregate abrasion at points of contact is substantially reduced because the aggregates are surrounded and cushioned by the fines.

Material strength

Now, according to existing arrangements, to maintain the permeability existing road bases, the aggregates are compacted such that the strength of the layer is directly related to the strength, durability and soundness of the aggregates (determined by various test methods specified by road authorities) so as to provide the underlying strength of the road base for the life of the road. However, as alluded to above, the drainage layer of existing road bases comprises a mixture of fines and coarse aggregates which eventually becomes impermeable as additional fines collect in the interstices so as to block the interstices between the coarse aggregate material so as to hinder permeability.

Now, as the lower drainage layers become impermeable, moisture accumulates and the moisture content increases in the upper layers of the existing road base, reducing shear strength and causing failure at least through the effects of shear and/or high pore pressure ("pumping") resulting in adjacent aggregate particles abrading becoming dislodged and the like and the subsequent failure of the road base.

Further disadvantage of existing road bases, due to the design nature of such road bases wherein moisture is adapted to percolate downwards, is that pollutants leech from such existing road bases resulting in pollution of the environment. As such, so as to adhere with environmental restrictions, the material used for such existing road bases is washed prior to use.

Now, in contradistinction, the matrix mixture for use in road bases comprises a mixture of fines and aggregates wherein the fines is of sufficient quantity such that aggregate on aggregate contact is reduced. As such, the strength of the road base is now rather directly related to the tri-axial compressive strength producing a road base having comparable strength to the above-mentioned existing road base while having the advantage of allowing for the use of aggregate material having lower strength properties when compared to existing aggregate material.

Furthermore, with the matrix mixture providing an impermeable mixture there is advantageously provided the reduction of moisture variations in the material which result in improved shear strength, and reduction or elimination of hydrostatic pore pressure build up within the matrix mixture and furthermore, on account of the coarse aggregate material being cushioned by the fines, there is no aggregate-aggregate contact wear, crushing, abrasion and the like of the aggregate material reducing the above-mentioned failures of existing road surfaces on account of reduced shear strength and/or high pore pressure and coarse material crushing and abrasion..

Furthermore, the matrix mixture provides a road base that is cohesive such that cracking is reduced or eliminated on account of the above-mentioned traffic or subsurface destabilisation effects which adversely affect existing road bases. In this manner, the road base comprising the matrix mixture is able to "self heal" so as to maintain the integrity of the road base.

Furthermore, on account of the road base comprising the matrix mixture and so as to be substantially impermeable, the matrix mixture road base does not suffer from the disadvantage of existing road bases with respect to the leeching of pollutants, chemicals and the like. Furthermore, given that there is substantially no chemical leeching, there may be even incorporated known pollutants, toxic chemicals and the like to provide advantages not only in waste disposal but also alternatively or additionally in the enhancing the physical and chemical characteristics of the matrix mixture.

Material shape

According to existing arrangements, the shape of the material plays an important factor in compaction, density and permeability. Specifically, as alluded to above where existing road bases derive their strength from the interlock of adjacent aggregate material, such aggregate material is therefore specified in accordance with particle size, shape, strength and other physical parameters so as to enhance the granular interlock. Specifically, the more cubic the aggregate material with prescribed particle size distribution, the greater the strength of the interlock.

Such physical characteristics are often mandated by road authorities and key properties for the acceptance of road base material includes criteria relating to strength, a fixed sized bounds and fixed shape bounds. However, the disadvantage of such material is that it is generally expensive to produce and obtain such physically constrained material resulting in increased cost of the subsequent road base.

However, for road bases comprising the matrix mixture, as alluded to above, at least on account of the fines supporting and filling the interstices between the aggregates, the shape, dimensions and the like of the aggregates is not important and in this regard even asymmetric and therefore cheaper aggregate material may be advantageously employed for the purposes of forming road bases.

Type of material

As alluded to above, an important characteristic of existing road bases is the strength characteristics and in this regard, coarse aggregates are sourced predominantly from virgin excavated materials such as materials excavated from quarries which material is subsequently crushed, screened and sized to ensure that only aggregates with specific strength, shape and size, and particle size distribution characteristics are employed for the purposes of forming existing road bases. In this regard, waste materials from previously used products or processes are rarely suited for acceptance in accordance with the criteria set for the coarse aggregate layer predominantly because of quality control (consistency of characteristics) with regards to the strength, size, shape and particle size distribution.

Conversely, the material employed for the matrix mixture need not meet such stringent requirements. Specifically, as alluded to above, the aggregate material is supported by the fines material in tri-axial compression so as to advantageously allow for the use of aggregate material comprising lower or substandard strength, shape size and particle size distribution characteristics. In this manner, waste aggregate material, and even fines material, may be employed for the purposes of road bases dramatically reducing the cost of such road bases. Plasticity of material type

Plastic fines are explicitly excluded from the use in existing road base materials by the specifications of the road authorities because plastic fines material properties, and particularly shear strength is adversely affected by moisture in conventionalroad bases.

The Plastic Index of materials is defined by the Liquid Limit and Plastic Limit under the Atterberg Test and road authorities typically place limits on the Plastic Index, and sometimes the Liquid Limit. The limits, according to existing arrangement, for the Plastic Index of between 0 and 6 for road base materials is almost universally adopted by road authorities. Some road authorities specify a liquid Limit of between 20 and 30 for existing road base materials and an upper limit of 20 for the Plastic Limit. By contrast, the low permeability of matrix mixture permits the use of plastic fines provided that the fines are placed and compacted at substantially the correct moisture content during construction. Because matrix mixture comprise low permeable materials that substantially prevent the ingress of moisture and maintain low moisture content within the body of the material during the pavement life, any plastic material used for the matrix mixture is not substantially affected by moisture and can therefore be used as a material for the matrix mixture. The inclusion of clays or plastic material further reduces the permeability of the matrix mixture.

Generally, Plastic Limit limits for matrix mixture are substantially 0 to 12 or even 0 to 20 or more depending on the nature of the clay materials. The limits for Liquid and plastic limit may vary depending on the application.

Shrinkage of material type

Although generally not specified by road authorities, conventional materials are required to have a linear shrinkage of less than 2%, so as to mitigate against the effects of cracking during drying and subsequent ingress of water via these cracks. The predominant cause of shrinkage is drying during construction, wherein the material is wet for application and compaction and subsequently and allowed to dry for use.

Conversely, on account of the lower moisture content of the matrix mixture for compaction during construction, less shrinkage occurs. As such the effects of shrinkage are substantially reduced for the matrix mixture. As such, materials with a Linear Shrinkage of more than 2% and up to 5% can therefore be accommodated in the matrix mixture.

As such, material types generally excluded for use in road base construction and the like on account of inferior linear shrinkage properties may now be used such as sandstones, shales, baghouse dusts and industrial wastes including gypsum and lime.

Toxicity of material type

On account on of their low permeability there is considerable reduction in leaching from matrix mixture. Matrix mixture can therefore contain waste and toxic aggregates or fines (subject to environmental approval of authorities). Materials with pH from 0 to 14 can be accommodated, either in part, or in total in the matrix mix and the matrix mixture can have a pH between 0 and 14, which control is determined by environmental authorities.

Conversely, conventional roadbases made from virgin natural quarried materials typically have a pH between 6 and 8 on account of the inherent properties of the source rock.

Bonding of material type The addition of pozzolanic fines in the matrix material in unbound granular pavements is not to generate a pozzolanic reaction it is specifically included to improved workability. If pozzolanic fines are included in matrix material then the pH must be controlled to remain below pH = 12.4 in order to prevent the pozzolanic reaction occurring and to remain unbound.

The inclusion of pozzolanic fines in the matrix material which possesses a pH >12.4 will generate a pozzolanic reaction and the material will develop increased shear strength and tensile strength. This pozzolanic reaction can be controlled, and therefore the strength gain can be controlled, by either controlling the quantity of pozzolan available for the reaction or the availability of cations supplied through either the binder or the inherent pH of the aggregate and/or the fines .

The bound matrix with increased strength and low permeability becomes an improved medium in which to lock in wastes and toxic materials.

The construction of roads with matrix mixture containing pozzolanic materials permits the rehabilitation and treatment of the unbound structure at the end of its service life by either tyning and shaping at low moisture; and/or the addition of fines and/or aggregate for the reconstruction of an unbound granular pavement (mechanical stabilisation); and/or the addition of foamed bitumen (bitumen stabilisation); and/or by addition of a binder or cement to produce a bound pavement (chemical stabilisation). These are treatments of the matrix base material that provide for extended pavement life at the end of the service life of the pavement.

The advantages of a bound pavement with pozzolanic fines is the pozzolanic reaction which progresses slowly by comparison with the cementicious reaction. The particular advantages in road construction include 1 ) a slow reaction rate which permits extended time for construction and reworking, 2) the matrix mixture can be trafficked before strength gain is achieved (no curing time as would be the case for cement and concrete), 3) more time for high compaction under traffic before strength gain, 4) pozzolanic reaction is a low heat reaction so reduced thermal shrinkage occurs as compared to cement and concrete, 5) the material can be stockpiled for a few days before use and 6) autogenous healing of pozzolanic materials if cracks develop in the bound structure.

The addition of pozzolanic fines increases the range of options available in pavement design, construction, reduced maintenance and rehabilitation at the end of the service life of the original pavement.

Whether unbound or bound this technology provides a means of controlling the material properties of the matrix mixture, reducing and eliminating the effect of increased moisture on the material properties and preserving the long term shear strength by controlling mix design, production and construction.

Matrix mixture as compared to conventional arrangements

There will now be described the specifics of the matrix mixture in further detail and specifically the contradistinction as to existing road authority material specifications so as to highlight the differences between the matrix mixture and existing road base material.

Specifically, referring to figure 2, there is shown a visual comparison between existing road base material 205 and the matrix mixture 210.

Specifically, as is apparent from figure 2, the existing road base material 205 comprises aggregate material 210 compacted such that the aggregate particles abut against adjacent aggregate particles. As is apparent, the interstices between the aggregate particles 210 is open so as to allow the permeation of water therethrough. As alluded to above, the permeation of water through the upper layers of the road surface is a desired effect so as to attempt to achieve the drainage of the water away from the road base to the drainage layers of the road base.

As is also apparent from the existing road base material 205, each aggregate piece abuts against the adjacent aggregate particles resulting in aggregate on aggregate/point-point contact.

During the compaction process of such existing road base material 205, water is generally added to the material 205 so as to enhance slippage so as to allow adjacent aggregate particles to be compacted more effectively. As such, the road base material 205 is given in figure 2 generally shows adjacent aggregate particles 210 having been compacted as far as is possible. As alluded to above, such compaction provides the strength characteristics of the road base which is a desired outcome for conventional arrangements. However, as alluded to above, inefficiencies in the lower drainage layers may result in moisture increase within the interstices of the aggregate particles 210, reducing shear strength and creating hydraulic pressures or "pumping" which disengages the granular interlock of the aggregate particles 210 resulting in failure.

Conversely, there is shown in figure 2 the matrix mixture 210 comprising a mixture of aggregates 210 and fines 215. As is apparent, the fines 215 are provided in sufficient quantity so as to reduce granular interlock between the aggregate particles 210 such that the aggregate particles are cushioned or suspended by the fines "matrix". As is apparent, the ratio of the fines 215 to the aggregates 210 is selected in accordance with a desired workability and permeability, and in particular to increase compaction and reduce the permeability of the matrix mixture 210.

As is apparent, the fines 215 substantially fill the interstices between the aggregate particles 210 such that water cannot permeate between the aggregate particles 210, advantageously providing the water permeability characteristics and the resultant advantages as discussed above.

Permeability of the matrix material as compared to existing arrangements

Now, in contradistinction with existing arrangements there will now be discussed the differences between the permeability of the matrix mixture and conventional road base material.

Generally conventional road base conforming to road authority specifications has permeability in the order of 1 x 10 ^"5 ms ^"1 . European and USA road authorities often specify a minimum permeability to ensure permeability is maintained and ensure moisture flow through the material.

It shall be noted that in contrast to other jurisdictions, in 201 1 the NSW RMS introduced new specification requirement for Heavy Duty pavements with a maximum permeability requirement of 5 x 10 ^"8 ms ¹ . No permeability limit is imposed for materials used in roads that are not in the HD category.

Typically, road bases with fines content below 7%, which is typical of hard rock quarried material, has permeability greater than 5 x 10 ^"5 ms ¹ .

However, the water permeability characteristics exhibited by the matrix mixture depends on the road authority requirements but generally offers a maximum permeability of less than 1 x 10 ^"8 ms ^"1 .

There is described means for controlling the permeability of the matrix mixture through mix design, production blending and construction of the matrix mixture.

Particle Size distribution of the matrix material as compared to existing arrangements Conventional road base materials are designed on particle size distribution to achieve maximum or tightest packing. Road authorities particle size distribution specification requirements are set based on the Fuller and Thompson equation below. This is not the basis for matrix mixture. The matrix mixture relies on particle surface area for mix design. In this the design is similar to asphalt concrete mix designs in which voids are important. In

Matrix mixture improved workability (reduced energy to achieve compaction) and increased density result in reduced permeability. This is a holistic approach which accounts for all the particle surface properties such as shape, dimension, angularity, surface roughness, texture and asperities.

Particle size distribution or size grading is the principle means by which road authorities try control materials and optimise the particle size distribution to achieve or maximise packing during compaction - to increase density of the road base. Almost without exception every road authority places limits on the particle size distribution.

The theory behind maximum packing comes from Fuller and Thompson 1907, Fuller's Equation is often the basis for optimising PSD for maximum density: f \

= 100 where P = percentage passing the screen size d

D = maximum particle size

n = coefficient, generally accepted between 0.5 and 0.35 and most often at 0.45.

Specifically, referring to figure 4, there is shown a particle size distribution Graph 400 wherein the dotted line represents the coefficient n = 0.3; continuous line for n =0.45 and dashed line for n=0.5 for a maximum D = 20mm size road base.

From the Fuller Curve the road authorities determine the limits for each particle size for a maximum 20mm size road base generally applied :

Sieve Size DTEI VicRoads RTA MR WA TNZ M/4 QMR QMR RTA

(mm) 20mm 3051 Crushed MRS MRS 3051 HD

Classl Rock 11.05 11.05

Base Type 1 Type 2.1

19 =) - Of) ^ - lOf) W - 10") too 7*> - I T ⁾ 55 - <¾0 iiiiiiii

13.2 77 - 93 78 - 92 70 - 90 70 - 90 70 - 90 b. - bU - ,'U

2.36 29 - 49 30 - 48 35 - 55 30 - 45 22 - 42 « - -1 ?0 - ^ 35 - 55

0.425 -3 - 23 1^ - 22 12 - 30 11- 23 - 14- 22 tO - 25 12 - 30

0 075

In the USA much larger maximum size particles are permitted such as 1 ½ "or 40mm. In particular, it has been found that the particle size distribution for the aggregates is not important provided that there are sufficient fines to act as a matrix.

Now, there will be discussed the particle size distribution of the matrix mixture as compared to conventional road base mixtures. Generally, the matrix mixture is able to comprise a higher percentage of fines in the -75μηη size fraction than as permitted by the relevant authorities for road base aggregate mixtures. Specifically, exemplary maximum fines content is permitted by relevant road authorities is presented in the following table: Jurisdiction % Minus 75 micron Road Authority Specification allowed

NSW Was 4% - 18% until RMS QA Specification 3051

201 1 , now 7% - 14%

Qld Type 1 5%- 10% QMR MRTS05 Unbound Pavements

Type 2.1 4% - 15%

Vic Class 1 & 2 : 7% - 1 1 % VicRoads Section 812

UK 0% - 9% UK Specification for Highway Works

Series 800

USA 4% - 7% FHWA Standard Specification for

Construction ofRoads and Bridges on Federal Highway Projects

Furthermore, there is shown the maximum allowable content fines particles in granular material accordin to specifications in different countries:

In most countries fines is capped at 10% maximum passing 75μηι. Conversely, in the matrix mixture, the fine particles fill interstices to reduce permeability by surrounding the aggregate particles such that when compacted, the aggregate particles are placed in tri-axial compression. This "cushion of fines" protects the aggregate particles from "aggregate-on-aggregate" forces, prevents intersticial dilatancy which results in shear caused by the rotation and disengagement of aggregate particles, and improves the durability of the matrix mixture through low permeability.

As such, the matrix mixture will comprise fines particle with a percentage of -75 μηη fines substantially greater than those shown above, such as those comprising greater than 10%, 12%, 14% and even 16% fines by mass. Aggregate strength, soundness and durability of the matrix mixture as compared to existing arrangements

There will now be described the strength of the aggregates within the matrix mixture as compare to existing arrangements. Specifically, as alluded to above, the cushioning effect of the fines allows for aggregates of inferior strength (that is uncompressed strength) yet while providing for the matrix material exhibiting strength characteristics (compressed strength) on par with existing arrangements yet while not suffering from the disadvantages of existing arrangements including those relating to permeability. The allowance for use of weaker aggregate material advantageously allows for the use of waste material and the like which would otherwise be ineligible for use in road base construction.

Road authorities specifiy strength requirements for aggregate material for use in road base construction. There are several tests for aggregate strength, including 10% Fines Value Test or Aggregate Crushing Value, Los Angeles Abrasion Index and wet/dry variation test comprising 10% Fines Value Test or Aggregate Crushing Value with one soaked sample (24 hrs soak followed by towel drying) as compared to a dry sample.

Specifically, in the following table, there is shown exemplary minimum unconfined compressive strength requirements as mandated by various exemplary road authorities:

Jurisdiction Minimum Unconfined Test method

Compressive

Strength

RMS - NSW Wet Strength min 70kN T215 10% fines value

Wet/Dry Variation min

35%

DMR - Qld Wet Strength min 95kN 10% fines value

Wet/Dry Variation min

45%

UK 50kN Aggregate Crushing Value (10%

Fines) Vic Roads - Vic Assigned to each rock Los Angeles Abrasion Index

type annually. 40%

UK 50% Los Angeles Test

USA 40% Los Angeles Test

It should be noted that material properties can be measured in differing manners also including particle size distribution, Atterberg limits (plasticity - clay contents), California Bearing Ratio CBR, aggregate particle strength durability and soundness, shape and proportion. There are several different test methods that can be applied to measure all of these properties. Also, and each road authority often has its own unique variation of one of these test methods. For example, material/aggregate strength, durability and soundness can be measured by several different methods: 10% Fines Value; Wet/Dry Strength Varitaion, Los Angeles Abrasion test, Aggregate Crushing Value; Ultrasonic velocity etc. and each road authority often has unique variations of these test methods to test aggregate particle strength.

The applied test methods and limits for strength and durability for Australian jurisdictions is provided below:

Specification DTE I Vic RTA MR WA TNZ QMR QMR RTA MR WA

20mm Roads 3051 Crushed M/4 MRS MRS 3051W Natural

Classl Rock 1 1.05 1 1 .05 Natural Granular

Base Type 1 Type Granular road

2.1 road base bases

Again, as discussed above, in the matrix mixture, the fines filling the interstices between the aggregate particles support the aggregate particles so as to spread forces acting on each aggregate particle as opposed to conventional aggregate particle granular interlock which experiences point forces. Through the spreading of forces acting on the aggregate particles, aggregate particles of lower strength may be employed as compared to those mandated by existing specification.

Shape of aggregate particles as compared to existing arrangements

Furthermore, there will now be described the shape of the aggregate particles as compare to existing arrangements. Specifically, as will be described in further detail now, the shape of the aggregate particles when used in the matrix mixture may have a greater asymmetry as compare to the specification for aggregate particles for existing road base.

Specifically, the fines of the matrix mixture adequately fill the interstices between the aggregate particles of the matrix mixture so as to accommodate asymmetric aggregate particles. Conversely, for existing conventional road bases, symmetric aggregate particles are desirous so as to allow for a rigid and effective aggregate particle granular interlock.

In the table below, there is shown sphericity criteria specified by exemplary road authorities:

Jurisdiction Sphericity Criteria

RMS - NSW Max 35% Proportional Calliper

DMR - Qld Max 35% Flakiness Index

Vic Roads - Vic Max 35% Flakiness Index

Conversely, for the matrix material, on account of the fines being provided in sufficient quantities so as to reduce contact between adjacent aggregate particles, aggregate particles having asymmetric properties does not hinder the resultant strength of the road base.

Application moisture content as compare to existing arrangements

The moisture content of the matrix mixture upon application is generally far less than the moisture content of existing road base materials upon application. Specifically, as alluded to above, for existing road bases, the road base material is wet to approaching the optimum moisture content so as to provide lubrication (reduce friction and shear strength) and assist in the compaction process. Specifically, the wetting of the existing road base material enhances the slippage of the aggregate particles so as to enhance the compaction of the resultant aggregate particle granular interlock.

However, the existing arrangements requiring the wetting of the road base material application comprises disadvantages not only on the effect of increased moisture on the strength of materials below the road base, but also the wastage of water, and also in the time period mandated for the drying of the road base prior to the allowance of traffic thereupon.

Conversely, for the matrix mixture, it is desirous to have a low moisture content. It is the fines that provide the lubrication required for compaction. Specifically, a low moisture content reduces reactionary hydraulic pore pressures which would otherwise impeded the compaction process. Furthermore, the fines content increases the workability of the matrix material. Furthermore, the low moisture content of the matrix mixture allows the resulting road base comprising the matrix mixture to be ready for traffic sooner than compared to existing road bases which require a drying period. For example, for conventional road base mixtures, a dry back to either 70% of optimum moisture content or 70% of saturation is required which may take up to 2 weeks of dry weather to obtain.

For example, below are moisture content specifications set by various road authorities:

The optimum moisture content is the water content at which a specified compaction force can compact a mass to its maximum dry unit weight determined by the Proctor test. As such, as is evident from the above specifications, there is a tight threshold about the optimum moisture content.

Conversely, for the matrix mixture, the threshold about the maximum moisture content can be greater than 2% such as up to 5% below optimum moisture content as determined by Proctor test. That is, if the optimum moisture content measured by the Proctor test is 9%, then the matrix mix moisture content can be 7% to 4% by mass.

Furthermore, as will be described in further detail below, during the blending process of the matrix mixture, the moisture is regulated and controlled.

Type of aggregates and fines as compared to existing arrangements

As alluded to above, given the onerous strength, size , shape and particle size distribution requirements, particular for the aggregate material, of existing road base material, aggregate material is usually sourced from virgin natural rock excavation, followed by crushing, screening, blending, sorting and the like.

However, is also described above, the matrix mixture makes allowance for inferior materials including in terms of strength, shape and particle size distribution and therefore advantageously allows for the usage of waste materials and the like.

Specifically, for the matrix material the aggregate may be sourced from various sources including coal washery rejects, quarry scalps, recycled brick, concrete or natural rock including weathered and sedimentary rock, weak sandstones, shales and mine gangue, industrial aggregate wastes, recycled glass, power station ash, steel slags. For the fines materials, the fines materials for the matrix mixture may be sourced from various sources including fly ash, red mud, lime and industrial slurries, bag house dust, mine tailings and incinerator dust, recycled glass.

Method of compaction

There will now be described a method of compaction using the matrix mixture as compare to existing road base material.

As will become apparent, usage of the matrix mixture allows for far less intensive compaction as compare to existing arrangements resulting in a not only cost savings during the compaction process, but also time savings in allowing earlier traffic usage.

Specifically, as alluded to above, for existing road base material, given that strength and stiffness is a desired outcome for existing road bases, intensive compaction energy is employed to increase the aggregate on aggregate granular interlock so as to provide the permeable and rigidity of the road base.

However, for the matrix material, given that aggregate on aggregate granular interlock is not a design requirement, and the presence of sufficient fines facilitates compaction, fewer compaction passes may be employed. Specifically, for the preparation of a road base comprising the matrix material, typically a maximum of two passes with a vibratory roller followed by two passes with a static roller is employed whereafter traffic may be allowed onto the road. This is compare to existing compaction processes where up to 20 passes or more may be required to achieve the desired aggregate on aggregate granular interlock.

Road authorities generally control layer thickness when road base is spread and compacted. The thickness of each layer is controlled and limited (in the case of most Australian road authorities to 150mm) to ensure that the passage of the compaction roller achieves the required compaction density at the bottom of the layer. However, the matrix mixture possess superior workability so as to aid in compaction to the required density in layers of 250mm or more. This efficiency in time, energy and effort translates to significant cost savings.

Furthermore, for road bases comprising the matrix mixture, vehicular traffic further enhances the compaction process, and as such, it is often times desirable to introduce traffic as soon as possible.

Specifically, referring to figure 3, there is shown a graph 300 comparing the resultant density as a result of compaction of the matrix mixture material and conventional road base material. Specifically, the graph 300 shows the resultant density of the matrix mixture 305 when compared to the resultant density of conventional road base material 310. As is apparent from the graph, the matrix mixture material attains a greater density sooner and with less energy than conventional road base material. Specifically in the field on construction sites, from only two compaction passes, the road base comprising the matrix mixture attains a density which would require between five or six compaction passes for conventional road base material. It therefore requires less time to compact.

Method of blending

During the preparation process of the matrix mixture, the aggregates and fines will be blended in proportion according to the mix design and with the addition of sufficient water , typically within pug mills to produce a consistent quality product with the desired material properties.. During this process, as distinct from existing arrangements, the water content of the matrix mixture is controlled. Specifically, as alluded to above, the water content of the matrix mixture is controlled so as to attain moisture below optimum moisture content as determined by Proctor test.

Specifically, conventional materials require moisture within 2% of Optimum moisture content to achieve compaction. At this high moisture, conventional materials must be allowed time (2 to 4 days) to dry back, release the pore water pressures developed during compaction, and develop shear strength. Trafficked immediately these materials typically develop ruts in the wheel paths, shove at the edge of wheel paths and develop potholes.

Conversely, the matrix mixture can be placed and compacted at moistures below 2% of Optimum moisture content. At low moisture high pore pressure does not develop during compaction. As a result the matrix mixture possess adequate shear strength at the time of placement to enable traffic immediately after placement. Furthermore, once compacted, but still unsealed, the matrix mixture is much less likely to be deformed under traffic in wet weather because the matrix mixture possess low permeability.

An effective manner at in which to control the moisture content of the resultant matrix mixture is in the selection of materials, and specifically in the selection of the fines materials. For example, fly ash has a particular dryness and may be utilised in the blending process to reduce the moisture content of the resultant matrix mixture. In other embodiments, a mixture of different types of fines materials may be employed also depending on the application. Such a blending process is distinct from existing blending processors wherein during the blending processes of existing arrangements, it is rather the resultant strength of the mixture which is important in which case the drying back of the material is important to achieve shear strength, or various additives such as binders, cements and geopolymers and the like are added to enhance the resultant strength characteristics of the final mixture. Generally, the aggregates, fines and water constituents need to be mixed proportionally to produce a consistent quality blended product. Invariably, the ingredient materials are variable, both in their particle size distribution and moisture content, such that proportioning and moisture must be controlled during production to ensure.

Interpretation

Embodiments:

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the above description of example embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description of Specific Embodiments are hereby expressly incorporated into this Detailed Description of Specific Embodiments, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Different Instances of Objects

As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

Specific Details

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Terminology

In describing the preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "forward", "rearward", "radially", "peripherally", "upwardly", "downwardly", and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

Comprising and Including

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Any one of the terms: including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising. Scope of Invention

Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used.

Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention. Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Industrial Applicability

It is apparent from the above, that the arrangements described are applicable to the construction industries.