WO2002053645A1

WO2002053645A1 - Asphalt binder-modifying additive useful to manufacture hot mix, cold-laid bituminous mixtures and process for manufacturing both the additive and the mixtures

Info

Publication number: WO2002053645A1
Application number: PCT/EP2002/000045
Authority: WO
Inventors: Francisco Maria Manes; Osvaldo Félix VULIJSCHER; Andrés Gustavo GIGLIANI
Original assignee: MMGV SA
Current assignee: MMGV SA
Priority date: 2001-01-05
Filing date: 2002-01-04
Publication date: 2002-07-11
Anticipated expiration: 2003-07-05
Also published as: CL2003001615A1; EP1349897A1

Abstract

An asphalt binder-modifying additive useful to prepare bituminous mixes comprising from 2 to 6 weight % of a flux, 20 to 70 weight % of a refined olefinic lubricant and from 4 to 10 % of a solvent, on the basis of the asphalt binder.

Description

ASPHALT BINDER-MODIFYING ADDITIVE USEFUL TO MANUFACTURE HOT MIX. COLD-LAID BITUMINOUS MIXTURES AND PROCESS FOR MANUFACTURING BOTH THE ADDITIVE AND THE

MIXTURES DESCRIPTION This application relates to an asphalt binder- modifying additive that allows for the preparation of asphalt mixes in industrial plants at temperatures of (100 - 120°C) , that are capable of being applied at room temperature, e.g. at 0 - 55°C, the asphalt mixes thus prepared and a process of cold application thereof .

The asphalt mixes prepared with the additive of this invention are particularly useful in the paving, resurfacing and patching of roads and streets, and they have certain advantages over the traditional mixes . Among these, there can be mentioned: handling at a lower temperature, better storability and an immediate availability thereof; they possess a better workability, which attribute persists even for months in the stored mixture, as well as the capability to achieve excellent surface textures upon the application of low thickness flexible pavement, and they are more impervious to water, soaps and detergents. In order to promote the attachment of bituminous materials onto negatively charged surfaces, and as fillers, a amine additive of cationic polarity can be added, either to the chemical compound or to the binder.

PREVIOUS ART

The closest previous art discloses asphalt or bituminous compositions comprising styrene - butadiene - styrene polymers, propylene and a solvent. Some of these compositions are disclosed as possessing acceptable properties at room temperature. Regarding this aspect, see US 5,640,109 and US 3,312,157.

Similarly, US 5,911,817 discloses mineral base lube oils that can be added to asphalt compositions to improve their low temperature characteristics. US Patent

4,878,950 discloses a material for bituminous compositions for roofing applications comprising a low molecular weight olefin copolymer or homopolymer with improved low temperature characteristics.

US Patent 5,961,709 discloses an asphalt composition comprising paraffinic oils. US Patent 5,750,598 discloses the addition of a sulfur-donating vulcanization agent to a bitumen/ polymer composition.

Patent 3,312,157 relies on a principle that is similar to the one proposed in this invention, the main difference being that the asphalt mix is made with methyl benzene .

None of the above publications refers to the final achievement, which is an asphalt mix made under similar conditions as a hot mix, cold-laid asphalt concrete, by using the additive of this invention.

Argentine Patent AR 228,977 discloses an asphalt- based binder for cold bituminous treatments that uses amine additives for the manufacturing of asphalt mixes Amine additives are used in the present invention only when certain features are to be achieved, as . explained hereinbelow.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows the adherence result of asphalts modified with the additive of the present invention, either wet or dry, according to the results in Table 1.

Figure 2 shows the results of the aging tests carried out according to Table 2, at 100 rounds.

Figure 3 shows the results of the aging tests carried out according to Table 2, at 200 rounds.

Figure 4 shows the results of the aging tests carried out according to Table 2, at 300 rounds.

DETAILED DESCRIPTION OF THE INVENTION

The additive of the present invention has been particularly designed to be combined with asphalt cement which, with the addition of a solvent, allows to manufacture an asphalt mix at a temperature lower than the conventional temperature (« 150°C) , subsequently laying said mixture at room temperature, even when wet and at a low or high temperature (0 - 55°C) and to store it in the open air for long periods of time, which periods of time vary according to the amount of solvent used in the production thereof .

In order to promote the attachment of bituminous materials onto negatively charged surfaces and as a filler, the additive can also comprise, if desired, an amine compound of cationic polarity, such as an alkyl amido-imidazoline, as a cationic support designed to promote the subsequent adhesion onto siliceous aggregates, by displacing the monolayer that usually covers negative charge density surfaces. The amine compound can be added to the additive merely by stirring it in.

The additive of this invention is composed of 2 to 6 % by weight of a flux, 20 to 70 % by weight of a refined olefin lubricant and 4 to 10 % by weight of a solvent, expressed as a function of the asphalt binder.

The flux included in the additive of this invention is a composition comprising a) 28 - 60 weight % high viscosity, high or possibly low molecular weight polyisobutylene, b) 0 - 5 weight % of a dispersing agent, c) 6 - 18 weight % of a light low molecular weight olefin hydrocarbon with low viscosity and low sulfur percent and d) 35 - 70 weight % of a hydrocarbon solvent to solubilize the polyisobutylene.

The light, low molecular weight olefin hydrocarbon with low viscosity and low sulfur percent used in the flux can be a crankcase lube oil such as an Esso motor Oil- or YPF- or SHELL-type oil of a SAE 40 viscosity.

The dispersing agent used in the flux can be a liquid surface-active dispersing wetting agent such as e.g. a sulfonated naphtenic powder such as Sulfur S or Troixol 98 C.

The elastomeric physical characteristics of the polyisobutylene used in the flux provide the additive and the final asphalt mix with improvements such as no aging and no oxidation.

The solvent used in the flux can be a solvent that allows the viscosity of the polyisobutylene to be lowered, such as, e.g. An Exxon D-110 solvent or gas oil.

The flux serves to improve the adherence of the aggregate - asphalt binder dyad, thus avoiding a future segregation of the aggregate and providing the flexible pavement with a better performance in rainwater, a better grip, a better elastic memory, fatigue resistance, lower aging and, therefore, a longer life.

The percentage of flux can also be varied depending on whether it is designed for patching (a lesser amount) or for paving (a greater amount) . The greater the amount of flux in the resulting mixture, the lesser the workability and availability (delivery unloading) thereof due to its high adhesive power.

The olefin lubricant comprised in the additive of this invention is a high viscosity, readily emulsifiable refined olefin hydrocarbon, which can be a hydrocarbon usable as a hydraulic means and made with special lubricant bases and optionally with additives which provide it with wear-resistant, anti-corrosive, anti- oxidant and anti-rust properties.

The lube oil, which increases the workability of the mixture, must have a high calorific capacity in order to keep the manufacturing temperature for several hours and allow the polyisobutylene to adhere to the aggregate in a more effective manner, thus achieving a greater adhesiveness of the modified asphalt binder when laid.

The lubricants that can be used in the invention are those having a viscosity index of 95, a flash point of 180 to 242°C and a pour point of -10, such as, for example, products H22 to H220, with NUTO H32 from ESSO being particularly preferred.

The solvent included in the additive of this invention can be a high flash heavy solvent such as gas oil, fuel oil, diesel oil, kerosene, etc. The amount of solvent used can be adjusted depending on the temperature at the place the mixture is to be laid; e.g., in a cold zone, it requires a greater, amount of solvent and a lesser amount of additive.

The additive of this invention allows for the hot mix, cold-laid, asphalt mix to be stored outdoors during long periods of time (over 90 days) .

The ratios in the additive vary according to the type of asphalt binder to be used, to the future requirements the pavement under construction is going to be exposed to and to the aggregates available. Thus, asphalt mixes treated with the additive of the present invention show a reduced spray effect (increased safety) , due to their greater adhesiveness and low noise, and to the high percentages of voids in their structure. The asphalt mixes of this invention are particularly useful for building micropavements (2 - 3 cm thick) in the resurfacing of streets, highways and freeways.

MODIFIED ASPHALT BINDER

The asphalt binder of this invention comprises an asphalt binder (asphalt cement) and the above disclosed additive, optionally along with an amine compound that may be incorporated into the additive or that can be separately incorporated in order to promote the attachment of bituminous materials onto negatively charged surfaces and as fillers.

The cationic polarity amine compound is one of the alkyl amido-imidazoline type, as a cationic support to promote the subsequent adhesion onto siliceous-type aggregates, by displacing the monolayer that usually -covers negative charge-density surfaces. It can be incorporated into the asphalt binder in a ratio of about 0,2 to 0,4 per cent, by means of a pump flow that recirculates it until fully homogenized. Suitable amine compounds can be derived from the products sold by Laher Mercantil, Polydem S.A. or by Quimica Bonaerense.

The asphalt binder can be prepared relatively in advance to the addition of the aggregates in order to form the asphalt mix of this invention.

Such asphalt binder is made two hours before the manufacture of the mixture so as to homogenize it.

ASPHALT MIX

The asphalt mix of this invention comprises a bituminous mixture and the above disclosed additive, as well as optional components.

The asphalt mix thus formed possesses a viscosity that renders it fully workable at medium or room temperature. It can be stored and it can keep its workability properties for months, even under extreme cold or hot conditions . COLD-LAID ASPHALT MIX

This mixture is generally comprised of granite aggregates of different sizes - 6-20, 6-12, 3-9, 0-6 (size of the aggregates measured in millimeters for coarse, medium and fine mixes, i.e. final thicknesses ranging from 6 mm to 30 mm) , siliceous sands and mineral filler; RAP (Reclaimed asphalt pavement produced as a result of the milling of existing pavements associated with virgin aggregates) can also be used.

The maximum size of the aggregate is 20 mm.

In the preparation of the above mixtures, asphalt binders, the modifying additive, traditional stone aggregates, steel slag, siliceous sands and, in certain instances, fillers, are used. The optimum content of asphalt binder, as well as the general characteristics of the aggregates, must comply with standard (VN - E9 (86) , Vialidad Nacional [National Highway Administration] , Argentine Republic) .

The asphalt mix is an asphalt concrete that is hot mixed in continuous or volumetric asphalt plants by combining asphalt cement (the permeation of which is usually 70/100 and or 50/60) with selected stone aggregates and the novel modifying additive of the present invention, which allows it to be used when cold for patching, paving and resurfacing streets and roads. As to the most widely used asphalt binders, there are known 50/60, 70/100 or 150/200 (1/10 mm) (IRAM 6605 standard) , 50/60 being used for high ambient temperature areas, 70/100 for medium temperature locations and finally, 150/200 for low ambient temperatures.

The ratio of the modifying chemical compound varies according to the rheological behavior of asphalts . Likewise, the individual components of the chemical compound vary depending on the different objectives to be achieved.

In order to develop an asphalt mix with a highly significant degree of adhesiveness between the aggregate- bitumen dyad, we must increase the amount of flux and identify which of these constituents serves that purpose within the composition.

For the mixture thus prepared to possess an even higher degree of workability, the ratio of lubricant and the ratio of light and heavy solvents to be added can be increased.

Another important aspect to bear in mind is the average temperature at the work site, because where temperatures are higher, a fast-evaporating solvent will be used, whereas at low temperature sites slow- evaporating solvents are to be used.

The relative amounts of material to be employed in the preparation of the cold-laid asphalt mix will be the ones listed below:

It is necessary to point out that the above percentages vary, inter alia, according to the type of asphalt mix to be obtained, the level of stability intended and the stone aggregate available, as well as the type of asphalt binder.

The granulometric environments most frequently used are the usual ones for asphalt mixes established by the regulatory standards effective in each country.

Continuous Gradation Batch Gradation (thickness up to 4 cm) (Thickness up to 3 cm) Sieve No. % passing Sieve No. % passing

(Limits) (Limits) %" 100

Y₂" 95 - 100 %" 100 3/8" 8800 -- - 9955 33//88"" 90 - 100

N° 4 5533 -- - 7766 NN°° 44 33 - 42

N° 8 39 - 57 N° 8 25 - 35

N° 16 29 - 44 N° 16

N° 30 20 - 33 N° 30 14 - 25

N° 50 14 - 25 N° 50

N° 100 9 - 18 N° 100

N° 200 4 - 10 N° 200 7 - 12

In order to assess the quality parameters of the mixes under examination Marshall-type test samples are made without the addition of a solvent. In other words, we refer to asphalt residue + flux + lubricant .

The preparation thereof is carried out at about 150 - 160°C and at a compaction power of 75 strikes a face, and they are tested at 60°C according to the aforementioned National road system Standard.

The Marshall values to be obtained are as follows:

Stability of over 500 kg

Density higher than 2,300 g/cm3

Voids between (3 and 6) %

ASPHALT MIX TO BE APPLIED AT MEDIUM OR ROOM TEMPERATURE

A hot mix bituminous mixture will be used at an asphalt plant. The resulting mixture must be storable, and keep unaltered for a predetermined period of time as needed, and it should be capable of being extended by hand or by mechanical means (motor grader, asphalt finisher, asphalt-grouting equipments, etc.)

The modified asphalt cement to be used will contain plastomers, fluxes, adhesion enhancers and lubricants, such that its viscosity is as needed to produce a full coating of the aggregate, providing it with a suitable adhesion and furthermore allowing the mixture thus prepared to stay completely manageable for a preset period of time.

The stone aggregates to be employed must be of an excellent quality, from a granite source that is clay- and organic material-free, and they must meet the following requirements :

Minimum sand equivalent passing sieve No. 4 (V.N.E.- 10) 55

Maximum Los Angeles abrasion (IRAM 1532) 35 %

Minimum cubicity (retained aggregate on a 3/8" sieve) (V.N.E.-ll) 0,6

Maximum durability (attack with sodium sulfate, 5 cycles) IRAM 1525) 12 %

Depending on the intended coarseness, aggregates with sizes ranging from (0-6), (4-8), (6-12), (6-18) mm, siliceous sands and the incorporation of a filler will be employed. The moisture content in the mixture at the time it is laid (extended) will not be greater than 0,2 %.

The Marshall stability will not be lesser than 500 kg.

Adhesiveness Bridge: In order to achieve a perfect homogenization of the existing pavement and the micropavement to be applied, a priming or binding aspersion operation will be carried out, either with diluted asphalt or a polymer-modified asphalt emulsion, which will give the pavement sheet to be applied a perfect adherence and cohesion.

The amount to be applied per square meter will range from 0.250 liters/m² to 0.500 liters/m².

Compacting: It will be performed with an 8 to 10 ton motor grader in successive passes and subsequently with a self-propelled 18 to 20 ton pneumatic roller. The opening to motor vehicle traffic will be immediate, and no aggregate detachment should be observed after traffic circulation has begun.

PARTICULAR TECHNICAL POINTS

This type of bituminous materials consists of a mixture of stone aggregates and fluidized and additivized bituminous binder, hot-mixed by the supplier, such that it retains its workability and compactability properties, which allows for it to be stored prior to its application at the construction site. Its use makes it possible to reduce the cost of performing the constructive process, due to the fact that it can be spread and compacted at a medium and room temperature.

It is hot-mixed at an asphalt plant, wherein aggregates are coated with a modified bituminous binder. This kind of preparation promotes a high degree of homogenization in the mixture, which is extremely difficult to achieve with an in situ pre-mixture, the reason for this being that the percentages of each one of the components are automatically controlled.

The role of the modified bituminous binder is therefore essential, since it insures the preservation of a suitable viscosity during storage.

Since the mixture possesses a higher degree of voids during the initial service period, the additives employed in the modified bituminous binder increase the bitumen - aggregate bond, thus counteracting the deleterious action of water that might eventually penetrate therein.

The aggregate used must be of the highest quality because:

1) The deformation resistance of this type of mixes particularly relies, in its initial stage, on the internal friction of the mineral skeleton, whereby the hardness and the frictional texture of the aggregate are crucial .

2) The permeability of the mixture in such a stage necessitates the existence of a good creep stiffness of the binder.

To achieve the greatest densification, the mixture must retain the lubricant effect produced by the flux and the additives. Thereafter, with the action of traffic and weather conditions, the mixture will attain its optimal behavior.

If it is necessary to store the resulting asphalt mix in the open for long periods of time, the modified bituminous binder, along with a predetermined percentage of a solvent (Gas Oil) should be added, and when the temperature is under eight degrees centigrade it is desirable to cover it with a clear polyethylene film or the like, thereby keeping a control of the meteorological variables (greenhouse effect) .

Rainwater does not alter the properties of the mix.

The mix very successfully employed in patching and in rolling sheets with thicknesses of one to two inches.

It is compacted at medium or room temperature, by means of successive passes of smooth, pneumatic roller.

GRANULOMETRIC ENVIRONMENTS USUALLY EMPLOYED

Granulometric limits, expressed in terms of passing percentages according to different uses and thicknesses

In order to comply with the specified granulometric limits, aggregates of sizes (0-6) , (4-8) , (5-10) and (6- 12) are generally used.

INITIAL EVALUATION

As a means to quantitatively evaluate the initial status of the mixture we can mold a series of Marshall test tubes about two inches high.

The mixture is poured into a Marshall mold, on the base of which a polyethylene disc is previously placed, and 25 strikes are applied by a rod in order to arrange the particles. Thereafter, the surface of the mixture is covered by another polyethylene disc, a piston is placed thereon and an increasing intensity load is applied, up to a pressure of 135 kg/cm² at a rate of 5 mm/minute. The load is kept for five minutes and the mold is then removed.

The test tubes undergo a curing process during one day in the open and three days in an oven at 60°C. Every day they are weighed to confirm the total loss of volatile material.

They are left to cool to room temperature and their Apparent Density is then determined, which apparent density should be greater than 2.20 g/cm³.

Before the test tubes are subjected to the Marshall technique, their height (thickness) is to be measured, such that the stability value is corrected by the appropriate factor according to the tables .

Thereafter such test tubes are assayed following the Marshall technique, but at a temperature of 25°C (after soaking in water for one hour at 25°C) .

Once the Marshall parameters given by the assay are figured out, the following acceptable limits should be met:

Stability = greater or equal to 500 kg.

Flowability = ranging between 2 and 4 mm.

Stability/flowability ratio = greater than 100 kg/cm Voids (Rice method) = ranging between 3 and 8 %.

The percentage of modified bituminous binder to be used in the preparation of the mix will range from 4.8 to 4.4 %, depending on the specific surface area of the arid mixture .

Where a solvent is added (Gas-Oil) , such solvent will not exceed 14 % of the modified bituminous binder.

FEATURES OF THE ASPHALT MIX

The asphalt mix may be used under extreme weather and time conditions, because it is cold laid and it does not require any type of additional component such as solvents and/or additives.

The mix is shipped in bulk, and it is stored in the open en a pyramidal shape, for up to two years without any kind of difficulties and without losing its physical- chemical properties. It can be laid over wet or drenched surfaces, it being possible to achieve the patching and paving in minimum thicknesses, providing the mix with the same characteristics as a hot-laid one.

The application is carried out by hand or mechanical means and it is extremely easy and safe, added to the fact that it can be immediately open to traffic.

The mix is waterproof, which improves its water resistance and allows for it to be laid at times when it is not possible to apply a hot mix, for example onto ditches wherefrom water has just been removed.

After being laid and compacted at the construction site, the mix maintains its high cohesiveness and it exhibits a remarkable elastic behavior. It has the major capability to resist the reflection of all signs of cracks and fractures existing on the backing surface due to the fact that it is self-repaired merely by the traffic passing over it.

The time available for its compaction is very long, since densification is precisely the cause permitting the elimination of the ingredients that keep the asphalt concrete workable. During the compaction at the working site, relatively low densities are attained, but in a very short period of time such density becomes the same as the one found in a traditional hot-laid mix as a result of the simple compaction brought about by motor vehicle traffic.

This feature is of the utmost importance when a traditional patching is carried out, since if such patching is made with a hot mix, it gets cold right away when used in small amounts, thus rendering small compaction equipments normally used ineffective, and precluding a suitable finish and waterproofing of the repair from being secured.

The compaction developed by the action of traffic itself after the asphalt mix has been applied, apart from the waterproof quality thereof, prevents water from permeating the lower layers of the repaired area (pavement base) .

USE

Patching, paving, resurfacing of asphalt or concrete pavements, sidewalks, bike lanes, airport runways, parking lots, etc.

PERFORMANCE

It varies depending on its thickness, 21 - 30 kg per square meter being required to cover per cm thickness, this further depending on the characteristics of the source of the aggregate and apart from its size. It results in a weight of about 2,1 - 3,0 ton/m³. An amount of 24 kg/m³ is preferred in the case of aggregates from granite sources .

TACKING

A cut-back asphalt can be used such as for example asphalts fluxed (additivized) with a solvent, gasoline, turpentine, and gas oil, depending on whether they are fast, intermediate or slow cut-off; or with fast cationic or anionic emulsions .

APPLICATION

For Patching

The surface is cleaned (either by hand or mechanically) . It is not necessary to frame or prime the pothole; where tacking is required, it will be at about 300 to 600 g/m²; thereafter the asphalt concrete is applied in a thickness higher than level - 1 to 2 extra centimeters - and a slight compaction is carried out, whereafter it is made available for traffic.

For paving and resurfacing

In the case of pavement, a previous .tacking step is carried out at 300 to 600 g/m² with cut-back asphalt or an asphalt emulsion, whatever the case may be, this being applied with an asphalt finisher or a motor grader, once the supported mix has been spread over the entire area to be paved, or by hand, using the amount required to cover the predetermined thickness; it is then compacted with a motor roller and then with an air roller in succeeding passes.

A - PREPARATION OF THE FLUX

A tank (sized according to the amount to be made) provided with a jet or a crossed paddle stirrer is used at a variable speed of up to +/- 140 r.p.m., with heating (e.g. in an oil bath) at a constant temperature of 80°C to 100°C, and the ingredients are added in the following sequence: a) the low molecular weight, low viscosity, low sulfur, light olefin hydrocarbon, in a liquid state, dosed in accordance with the amount to be made; b) the powder sulfonated naphtenic dispersant, in the required amount, adjusting the addition until an appropriate homogenization is achieved in the 20' to 40' period it takes to fully disperse; c) polypropylene, preferably polyisobutylene (e.g. Opanol from BASF or VISTANEX from EXXON) of high or even low molecular weight with stirring until homogeneous . The stirring time required varies according to the amount to be prepared; d) The high flash solvent (e.g. Diesel Oil or Fuel Oil) in the same manner.

B - PREPARATION OF THE ADDITIVE

1) It is blended in a larger tank, heating the high viscosity refined olefin hydrocarbon in the same manner and at a temperature of 100 to 130°C.

2) an equivalent percentage of flux (A) is added with stirring until fully homogenous.

Note: the addition of light and heavy solvent (Kerosene - Gas Oil) is made just before preparing the asphalt mix as disclosed hereinbelow.

C - PREPARATION OF THE MODIFIED ASPHALT BINDER Asphalt cement is introduced into a heated tank (an asphalt tank in a manufacturing plant) , e.g. and asphalt cement of 50/60 or 70/100 or 140/200 permeability) in a sufficient amount to meet the requirements, bringing the temperature thereof to 150°C - 160°C (recirculating it by means of the plant's asphalt pump) and adding the chemical compound (A+B) , this being recirculated until the Asphalt - Additive mix is fully homogeneous, thereafter adding the light and/or heavy solvent such as, e.g., kerosene or gas oil, in the required amount . The heated tank can also be provided with a low revolution turbine in order to improve the mixing of the ingredients .

The A+B+C combination is referred to as Modified Asphalt Binder.

D - PREPARATION OF THE ASPHALT MIX

The cold-laid asphalt mix is prepared in an asphalt manufacturing plant in the same manner as the hot mix is made, except that care must be taken that the temperature of the modified asphalt binder (A+B+C) does not exceed 140°C (80 to 140°C for its preparation) and constantly recirculating the modified binder.

The addition of a solvent can be put off until one hour before the preparation of the asphalt mix, since this is approximately the time it takes for the above ingredients to homogenize.

The aggregates previously placed in the hoppers are conveyed to the burner wherein they are heated at the same temperature as the binder in order to remove the moisture thereof, for example by means of special coils containing special oils at high temperatures within the temperature limits specified by each bitumen manufacturer and the binder is added to a mixer, in a predetermined proportion within a variable period depending on the hourly production capacity thereof (such as, e.g., 40/60 tons/h or 80/100 tons/h) .

Once the asphalt mix is made, it is placed on a hopper-shaped platform and it is then loaded into a dumping truck to be shipped to the storage place, where it is to be stored outdoors in the form of a pyramid until used.

Aggregates can include fillers such as ground slags that have been comminuted to different sizes, which are byproducts of steel blast or electric furnaces.

The fillers most frequently used are: aggregate crush powders, Portland-type cements, fly ashes, commercial limestones, asphaltite, etc.

Traditional aggregates are from various sources, and of a different nature and granulometry. They are selected according to the type of mixture needed for the job, to the average thickness of the pavement and to the macro- and microtexture values desired.

In order to meter them, several granulometric practices are employed, which practices can be continuous or batch-like. In our country the batch granulometry is preferred at present, since they provide a better contact, better adhesiveness between the tire and the tread surface as much in motion as in braking.

Among the most widely used aggregates there can be mentioned the crushed stone granite aggregates, basalt aggregates, quartz aggregates, dolomite aggregates and ortho-quartz aggregates. However, they can vary in accordance with the requirements in each zone.

Slags that have been crushed to different sizes are byproducts of blast or electric furnace steel processes.

The most frequently used fillers are: aggregate crush powders, Portland-type cements, fly ashes, commercial limestones, asphaltite.

COMPARATIVE PROPERTIES OF THE ASPHALT MIXES OF THE PRESENT INVENTION AND THE ONES OF THE PRIOR ART

CHARACTERISTICS OF THE COLD-LAID HOT MIX ACCORDING TO THE INVENTION

1. It is applied under all weather conditions.

2. It can be applied at night .

3. It is applied in minimum lifts.

4. The useful life of the material is 20 % longer than that of traditional mixes .

5. The equipment required for its application is reduced by one half.

6. Labor performance is increased by 50 %.

7. Only one half of the tacking step is used.

8. It is not necessary to frame small potholes, therefore the material requirements are decreased.

9. It does not give off toxic fumes during its application.

10. Because of its composition, it does not result in stone segregation.

11. The application is faster, making it possible to rapidly release it to traffic.

12. It can be stored outdoors for long periods of time without losing its properties .

13. It is applied even in the rain.

14. In pavement and resurfacing, minimum lifts can be used starting from 10 mm.

15. In pothole patching and resurfacing, it results in savings of 25 % minimum.

FEATURES OF THE PRIOR ART MIXES

1. Their application is limited by weather conditions, because manufacturing plants do not produce them in rainy weather, high humidity or at night.

2. They cannot be applied at night because manufacturing plants are not working. 3. They give off toxic fumes within city limits, since the mixes have to be kept warm in kettles.

4. The quantitative yield is lesser. If it rains, the unused mix has to be disposed of.

5. If they do not keep the appropriate temperature on their application, they present an untidy appearance and the material is detached from the pothole.

6. They cannot be recapped with a lift of under 3 cm.

EXAMPLE 1

The assays carried out on the asphalt mix of the present invention are disclosed below:

Flux: It serves the purpose of improving the adhesiveness of the aggregate asphalt binder dyad, thus avoiding a future segregation of the aggregates . Therefore, it imparts a longer life on the pavement. It is comprised by: a) high viscosity polyisobutylene (low molecular weight hydrocarbon - propylene polymer) , b) Sulfur S (powder) (dispersant) , c) olefin hydrocarbon for lubrication. Its main features are:

ASTM method Density 0,850 at 15°C g/cm³ 1298 Flash point 215°C 92

Pour point -12°C 97

Viscosity 100°C CST 68 Method 445

Viscosity index 95 2,270

Rust test Passes 665

ISO VG Ranking 68 d) Solvent (light distillate hydrocarbon)

Note: The percentages of these products vary depending on the type of asphalt binder to be used, on the future requirements the pavement to be built is going to be exposed to and on the aggregates available.

Additive' s lubricant : It is a refined olefin hydrocarbon of high viscosity, with good emulsifiability, that is anti-corrosive, anti-rust and anti-foaming.

The highly stable hydraulic oil or lubricant base possesses an excellent anti-rust protection.

ASTM method Density (g/cm³) 0.850 at 15°C 1,298 Flash point (°C) 210 to 250 92

Viscosity index 92 2,270

Pour point -9°C 97

Viscosity @ 100°C CST Method (e/6 and D445

23)

Solvent in the Asphalt Mix: It is a combination of medium and heavy distilled hydrocarbon (such as kerosene and gas oil) the main characteristics of which are as follows:

ASTM method Density (g/cm³) Average 0,820 at 15°C 1,298 Top distilled point Between 240 and 380 (°C)

Flash point (°C) 52 to 60 92

Pour point (°C) 0 to 1°C 97

Average Viscosity (1.5 to 4) at 40°C D445

Freezing point: (variable depending on the area to be used in; -50°C for cold areas and -5°C for mild temperature areas) .

These values vary according to the percentages the various solvents with commercial names similar to those of kerosene are blended with gas oil and/or turpentine. Depending on the nature of the areas (cold or warm) where the asphalt mixes are to be used, rapid or slow- evaporating solvents will be needed (gas oil or kerosene) .

Dispersant Detergent: 300 parts per million.

The asphalt mix of the invention was tested based on the following composition:

Lubricant 69.9 to 22.8 Solvent 28 to 71.5

The values required for the asphalt mixes of the present invention are the ones detailed below:

Unit weight of the compacted asphalt mix test sample :

Minimum: 2.30 g/cm³

Voids (Rice Method) : 4 % Minimum

Marshal Stability: 500 kg Minimum

Marshal flowability: 2.0 mm Minimum:

Four test samples were made from a stored mix made 20 days before and they were tested at 60 and 40°C following the standards normally established for traditional asphalt mixes.

RESULTS OF ASSAYS ON ASPHALT MATERIALS

APPARENT DENSITY

Airborne weight (g) 1057.2 1065.4 1056.3 1058.0

Volume [cm³] 432.9 439.6 433.7 434.1

MARSHALL STABILITY Ring Factor: 10.8

Stability reading 91 90 104 91

Height adjustment 1.32 1.25 1.32 1.32 factor

The results attained in these assays, are similar to the values of hot mix, hot applied asphalt mixes.

ASPHALT CEMENT-MODIFYING CHEMICAL COMPOUND TO BE USED IN THE PREPARATION OF COLD-LAID ASPHALT MIXES

The mix was made at the asphalt manufacturing plant at a temperature of 140°C and it was stored outdoors, later to be applied at ambient temperature)

Formulae of the compound included in the asphalt cement

Note: Asphalt cement can have a penetration of 50/60 or 70/100.

The structure of the chemical additive is as follows :

Polyisobutylene (high viscosity)

- hydrocarbon/ low molecular weight polypropylene Polymer

- Sulfur S powder

- Olefin hydrocarbon (I) 2 kinds

- HIG FLAM Solvent

- 10 - 25 % Solvent (Gas Oil or kerosene)

- 4 - 8 % Olefin Hydrocarbon (2)

- 85.7 - 65 % Asphalt Cement

For the above stated reasons, the stone aggregate for the asphalt mix will range from 96.3 % to 93.5 %.

The high viscosity raffinate has good emulsifiability, it is anti-corrosive, anti-rust and anti-foam. Its properties can be as follows:

Viscosity index 92 as per ASTM 2270 method

Flash point between 210 and 250°C

Pour point -9

Viscosity between 6 and 23 at 100°C D445.

The lubricating olefin hydrocarbon has the following characteristics according to the ASTM method:

Density 0.870 at 15°C g/cm³ 1298

Flash point 215°C 92

Pour point -12 97 Viscosity at 100°C OST-68 445

Viscosity index 95 2270

Rust test passes 665

ISO VG 68 Dosing

The lubricant base has high chemical stability and a very good anti-rust protection.

Example 2

A typical modified asphalt cement according to this invention was prepared with the following components:

The above modified asphalt cement was added to a typical asphalt mix, according to the present invention, in the following ratios:

An asphalt mix of the present invention was thus achieved, with improved features.

Example 3

The following assay was performed with the aim of showing the adhesiveness of the modified asphalts of this invention, according to Table 1 below. TABLE 1

The results obtained in this assay are presented as a graph in Figure 1.

Example 4

The following assay was performed with the aim of showing the aging undergone by the modified asphalts according to the present invention, as stated in Table 2 below.

TABLE 2

The results obtained in this assay are presented as graphs in Figures 2 , 3 , and 4.

Claims

1. An asphalt binder-modifying additive useful to prepare bituminous mixes comprising from 2 to 6 weight % of a flux, 20 to 70 weight % of a refined olefinic lubricant and from 4 to 10 % of a solvent, on the basis of the asphalt binder.

2. The additive of Claim 1, wherein the flux comprises a composition of: a) 28-60 weight % of a high viscosity, high or eventually low molecular weight polyisobutylene , b) 0-5 weight % of a dispersant agent, c) 6-18 weight % of a light, low molecular weight, low viscosity and low sulfur olefin hydrocarbon, and d) 35-70 weight % of a hydrocarbon solvent to solubilize the polyisobutylene .

3. The additive of Claim 2, wherein the light, low molecular weight olefin hydrocarbon in the flux has a low viscosity and a low sulfur percent, and it comprises an engine crankcase lube oil with a viscosity of 40 SAE.

4. The additive of Claim 2, wherein the dispersing agent used in the flux • is a liquid, surface-active dispersing wetting agent such as a naphtenic sulfonated powder.

5. The additive of Claim 4, wherein the naphtenic sulfonated powder is Sulfur S or Troixol 98 C.

6. The additive of Claim 2, wherein the solvent used in the flux is Exxon D-110 or gas oil.

7. The additive of Claim 1, wherein the lubricant has a viscosity index of 95, a flash point of 180 to 242°C and a pour point of -10.

8. The additive of Claim 7, wherein the lubricant is selected among the products H22 and H220, with NUTO H32 sold by ESSO being particularly preferred.

9. The additive of Claim 1, wherein the solvent is a heavy, high flash point solvent .

10. The additive of Claim 9, wherein the heavy, high flash point solvent is selected among gas oil, fuel oil, diesel oil and kerosene.

11. The additive of Claim 1, optionally comprising an amine compound.

12. An asphalt binder that comprises and additive of Claim 1 together with an asphalt cement.

13. The asphalt binder of Claim 12, optionally comprising an amine compound of cationic polarity.

14. The asphalt binder of Claim 12, wherein the compound is present in an amount raging from about 0.2 to

0.4 % of the total composition.

15. The asphalt binder of Claim 13 , wherein the amine compound is and alkyl amido-imidazolidine.

16. The asphalt binder of Claim 12, which is 50/60, 70/100 or 150/200 (l/lO mm) (IRAM 6604 Standard), using 50/60 for high ambient temperature sites, 70/100 for medium ambient temperature sites and 150/200 for low ambient temperatures .

17. Asphalt mixes that are workable at medium or room temperature, which comprise an additive of claim 1 and aggregates .

18. The asphalt mixes of Claim 17, wherein the mixes comprise 6-20, 6-12, 3-9 . and 0-6-sized granite aggregates, siliceous sands and mineral fillers.

19. The asphalt mixes of Claim 17, wherein the aggregate is 20 mm in size.

20. The asphalt mixes of Claim 17, wherein both the asphalt binder and the aggregates comply with Standard VN

E9 - (86) , Vialidad Nacional (National Highway Administration), Argentine Republic.

21. The asphalt mixes of Claim 17, wherein permeability is 70/100 and/or 50/60.

22. The asphalt mixes of Claim 17, further comprising an amine compound.

23. A process for manufacturing the additive of Claim 1, which comprises mixing the flux, the refined olefin lubricant and the solvent.

24. A process for manufacturing the mixtures of Claim 17, wherein the additive and the aggregates are mixed at a temperature lower than 150°C.