RU2465231C1 - Asphalt mix and method for preparation thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the industry of construction materials, asphalt mix and a method for preparation thereof. The asphalt mix contains mineral material which contains crushed rock, fine aggregate, mineral powder, as well as asphalt binder and reinforcing fibrous filler, with the following ratio of components of the asphalt mix in wt %: crushed rock - 30-70, fine aggregate - 10-65, mineral powder - 5-40, asphalt binder - 3-15 (over 100% of mineral material), 0.1-0.15 wt % PAN fibres and 0.01-0.15 wt % carbon fibre (over 100% of the weight of mineral material). The carbon fibre in the mixture is finely cut carbon fibres with length of 3-40 mm from continuous carbon fibre having monofilament breaking strength of not less than 2.5 GPa. Also described is a method of preparing the asphalt mix.

EFFECT: high resistance to rutting and formation of quality and durable asphalt coat.

6 cl, 3 tbl

Description

Technical field

The invention relates to the construction materials industry, in particular to the composition of the asphalt mix used to create and repair coatings in road and airfield construction, as well as to a method for preparing the asphalt mix.

State of the art

Asphalt concrete pavement structures are the main type of roadway and pedestrian street, highway and airfield pavement structures, while asphalt concrete mixtures reinforced with various types of fibers are used to improve the operational properties of the pavement.

There are known technical characteristics for the construction of road structures using TP 103-07 asphalt concrete prepared by the Department of Urban Planning, Development and Reconstruction of the Government of Moscow, Moscow, 2007, according to which asphalt concrete mixtures with fibrous fillers make it possible to obtain reinforced asphalt concrete with increased crack resistance at low temperatures and resistance to the formation of plastic deformations at high temperatures. As the reinforcing fibers, various types of natural, polymer or synthetic mineral fibers can be used, for example cellulose fiber, asbestos fiber, glass fiber, basalt fiber and other types of fibers. However, the level of properties of fiber-reinforced coatings obtained according to these technical recommendations is still unsatisfactory. The disadvantage of methods using these types of fibers is either the lack of reinforcing properties, as in the case of cellulose fiber, which does not allow to achieve improved strength indicators, or poor adhesion, as in the case of polymer fiber, which does not allow to achieve improved crack resistance.

In the patent literature, in particular from CN 101081725, publ. 12/05/2007, it is known to use asphalt concrete with a fibrous aggregate of polyacrylonitrile fiber (PAN fiber) 1.5-2.5 decitex 6 mm long, added in an amount of 0.2-0.3 by weight of concrete. Asphalt concrete with polyacrylonitrile fiber aggregate has an increased service life and resistance to deformation, high temperature stability, high water resistance and does not have a harmful effect on the environment and the human body.

From CN 1908069, publ. 02/07/2007, it is known that 0.1-0.5% hollow or porous polymer fibers with a particularly complex cross-sectional shape are introduced into asphalt mixtures. The polymer fiber may be a polyester fiber, a polyacrylonitrile fiber (PAN fiber), or compositions of these fibers. However, the formation of a complex cross-sectional shape of the fiber additionally increases the cost of the process of obtaining asphalt mix without significant improvement in the properties of the coating.

The closest analogue of the claimed invention is an asphalt mixture according to CN 101798196, publ. 08/11/2010, containing fiber containing 15-35% polyester fiber, 35-55% wood fiber, 15-35% PAN fiber and 15-35% nylon fiber. According to CN 101798196, the introduction of a reinforcing fibrous filler of the specified composition improves the shear resistance, reduces rutting and deformation, increases toughness while reducing construction costs and reducing the weight of concrete. However, the mixture of fibers used in CN101798196 contains fibers from materials that sharply limit the temperature of the asphalt mixture production process, since their melting or decomposition temperature is much lower than the preparation temperature of most asphalt concrete, usually about 160 ° C. Thus, the use of this mixture of fibers becomes impossible or ineffective.

Thus, the use of a fibrous filler containing only PAN fiber or its mixture with polyester fiber, wood fiber and nylon fiber does not allow to achieve a given level of reinforcing properties, in particular, does not provide high resistance to rutting.

With regard to the method for preparing the asphalt mixture from the patent document KR 100893545, published on 04.17.2009, there is a method for producing a more stable asphalt concrete with the introduction of polyvinyl acetate (PVA) fiber and converter slag, in which to simplify the process of mixing and laying in the field carry out the stages of magnetic selection of converter slag of low density having a density of 3.3 g / cm ³ or less, carry out the classification of the selected converter slag p about the size of the particles into large aggregates and small aggregates, introduce the filler and PVA fiber into the powder mixing unit to prepare the combined filler, introduce the combined filler in the packaging bag and lay the resistant to formation of ruts of asphalt concrete by mixing and heating. However, storing the combined filler containing the filler and the PVA fiber in the packaging bags facilitates the delamination of the mixture and reduces the uniformity of the distribution of the fiber in the asphalt mix, thereby degrading the properties of the resulting coating.

From the patent of the Russian Federation No. 2156227, published on September 20, 2000, a method for preparing an asphalt concrete mixture is known, which is carried out by mixing heated mineral materials, including stone materials and mineral powder, with bitumen and a reinforcing filler, while basalt fibers of 2- length are used as reinforcing filler 40 mm, a diameter of 150-200 microns in an amount of 0.8-1.1% by weight of mineral materials that are uniformly added to the mineral powder through a metering tank, and then introduced into the mixer before starting oatsa main mixing. In this method, a pre-prepared mixture of mineral powder with basalt fiber is obtained by automatically feeding fiber from a metering tank to a conveyor elevator of mineral powder. During transportation, the fiber is distributed and mixed with mineral powder, and the mixture of mineral powder and basalt fiber thus obtained is then fed to a common mixer, after which heated stone materials and bitumen are loaded into the mixer and the mass is finally mixed. RF patent No. 2156227 solves the problem of reducing the cost of asphalt concrete mix, however, during transportation at the elevator conveyor, only partial preliminary mixing of the mineral powder with basalt fiber occurs, which does not provide the required uniformity of fiber distribution in the asphalt concrete mix and thereby worsens the uniformity of the properties of the obtained asphalt concrete coating .

SUMMARY OF THE INVENTION

The objective of the claimed invention is to overcome the disadvantages of the prior art and the development of fiber-reinforced asphalt concrete mixture, in which the composition and properties of the reinforcing fiber filler are best combined with petroleum bitumen, which ensures better adhesion of bitumen, durability of the resulting coating, maintaining a high level of its properties and a significant increase in resistance to the formation of a rut. The claimed invention also provides a better distribution of fibers in the total volume of the asphalt mix due to the density of the fibrous materials used, close to the density of the bitumen binder.

The developed asphalt mix according to the invention takes into account the coefficients of thermal expansion of the fibers included in the composition of the reinforcing filler, which should not vary significantly for the different types of fibers included in the composition of the reinforcing filler, and should not significantly differ from the similar coefficient of the bituminous binder. In technical solutions known from the prior art, these indicators were not taken into account, which led to a premature loss of the accumulated properties of the final asphalt mix and the formation of road surface defects in the event of sharp seasonal temperature fluctuations, as well as problems associated with the formation of a rut that significantly reduces traffic safety and requiring significant costs to eliminate it.

The object of the invention is solved due to the fact that the asphalt mixture according to the invention includes a mineral material containing crushed stone, fine aggregate, mineral powder, as well as a bituminous binder and reinforcing fibrous filler containing PAN fiber and carbon fiber, in the following ratio of components of the asphalt mix, wt .%:

crushed stone 30-70,

fine aggregate 10-65,

mineral powder 5-40,

bituminous binder 3-15 (in excess of 100% by weight of the mineral material),

PAN fiber 0.1-0.15 (in excess of 100% by weight of the mineral material),

carbon fiber 0.01-0.15 (in excess of 100% by weight of the mineral material).

The asphalt mixture of the specified composition provides a high level of properties and a significant increase in resistance to rutting. The coating obtained from the asphalt mixture according to the invention has a rutting rate of less than 0.60 mm / 10000 passes, measured at a temperature of 50 ° C and a load of 0.6 MPa.

The object of the invention is also solved by the fact that the method of preparing the asphalt mixture includes preliminary dry mixing of mineral powder and a reinforcing fibrous filler containing 0.1-0.15 wt.% PAN fiber and 0.01-0.15 wt.% Carbon fiber ( over 100% by weight of mineral material), in a mixer at a mixing speed of 200 to 1500 rpm, introducing a previously obtained mixture of mineral powder and said reinforcing fiber filler into mixed heated crushed stone and fine aggregate with following the heated bitumen.

When pre-mixing the mineral powder and the reinforcing fibrous filler, heating can additionally be carried out to a temperature of 45-120 ° C.

The claimed method provides a uniform distribution of a reinforcing fibrous filler containing PAN fiber and carbon fiber in the asphalt concrete mixture during its preparation, which helps to obtain uniform high properties of the asphalt concrete coating, in particular, stable high resistance to rutting.

The use of a reinforcing fiber filler composition developed by the inventors of the present invention, containing 0.1-0.15 wt.% PAN fiber and 0.01-0.15 wt.% Carbon fiber (in excess of 100% by weight of the mineral material) also increases the resistance of asphalt concrete to exposed to acidic or alkaline aggressive environments, it allows to reduce the thickness of the top layer of the coating and significantly reduce the cost of stone material.

The implementation of the invention

According to the invention, a reinforcing fibrous filler containing 0.1-0.15 wt.% PAN fiber and 0.01-0.15 wt.% Carbon fiber (in excess of 100% by weight of the mineral material) can be introduced into all types of asphalt mixtures, in in particular, in “high-density” asphalt mixtures and “A” mixtures with crushed stone content of 50-70 wt.%; “B” type asphalt mixtures with crushed stone content of 40-50 wt.%; “B” type asphalt mixtures with crushed stone content of 30-40 wt.%, as well as “G” type asphalt mixes without crushed stone; and mixtures "ЩМА" (crushed stone and mastic asphalt) with a crushed stone content of 60-70 wt.%.

The claimed mixture may contain from 0 to 70 wt.% Crushed stone, mainly from 30 to 70 wt.% Crushed stone. When the content of crushed stone is less than 30 wt.%, The content of fine aggregate should be increased to 95 wt.% Accordingly. For the preparation of crushed stone, durable frost-resistant igneous, metamorphic and sedimentary rocks can be used, as well as durable and frost-resistant, slowly cooled metallurgical slags. Preferably, the compressive strength of the rocks should be at least 100-120 MPa, and the sedimentary carbonate rocks and metallurgical slag should be at least 80-100 MPa.

In the manufacture of the claimed asphalt mix, fine aggregate is contained in amounts of 10 to 65 wt.%, And in asphalt mixes without crushed stone - from 10 to 95 wt.%. To obtain the claimed asphalt mixture can be used natural and crushed sands, screenings of crushed rock and gravel. The sands used must contain no more than 3 wt.% Dusty-clay particles. Typically, natural sand with a grain size of up to 5 mm or crushed sand grades 800 and 400 obtained by crushing rocks or crystalline metallurgical slag, as well as sand obtained from waste products from ferrous and non-ferrous metals, is usually used.

Mineral powder should be 5-40 wt.%. Mineral powder is obtained by grinding limestones, dolomites and other carbonate rocks with a strength of at least 20 MPa and a content of contaminants and clay impurities of not more than 5%. Powdered industrial wastes can also be used as mineral powder - fly ash of cement plants, ashes of thermal power plants.

Bituminous binder, mainly oil bitumen of grades 60-90, is introduced into the asphalt mixture in an amount of 3-15 wt.% (In excess of 100%) by weight of the total mineral material, including crushed stone, fine aggregate and mineral powder. Bitumens are organic binders consisting of high molecular weight hydrocarbons of naphthenic, methane and aromatic series, as well as their oxygen, sulfur and nitrogen derivatives.

Group composition of bitumen:

1. Oils - molecular weight of 300-500 AU, the content in bitumen is 40-60%.

2. Resins - molecular weight of 500-1000 AU, the content in bitumen is 20-40%.

3. Asphaltenes - molecular weight 1000-5000 AU, content in bitumen 10-25%.

4. Carbenes, carbides insoluble in benzene.

5. Asphaltic acids - their content determines the rate of adhesion of binders to stone materials.

6. Paraffins - worsen the properties of bitumen, giving it brittleness.

For the preparation of asphalt mixtures used viscous oil road and oil road liquid bitumen. For hot and warm asphalt mixes of grades I and II, only bitumen grades of BND grades should be used, and for hot and warm asphalt mixes of grades III and IV.

The claimed asphalt mixture also contains a reinforcing fiber filler, which includes PAN fiber and carbon fiber, while the mixture contains 0.1-0.15 wt.% PAN fiber and 0.01-0.15 wt.% Carbon fiber (over 100% by weight of mineral material).

Mostly PAN fiber is introduced into the asphalt mixture in the form of PAN fiber, which is a mixture of cut fine PAN fibers obtained by a method including

- chemical copolymerization of monomers — nitrile of acrylic acid (NAC), methyl acrylate (MA), itaconic acid in a solution of sodium thiocyanate in the presence of a parophore polymerization initiator and isopropyl alcohol chain growth regulator, to obtain a dope copolymer solution;

- forming the PAN fiber from the spinning solution and processing the formed fiber on the spinning units to obtain a fiber having desired properties;

- cutting the fiber in a drum-type cutting machine to produce PAN fiber with a given fiber length.

The characteristics of PAN fibers suitable for use in the preparation of asphalt concrete are shown in Table 1.

Table 1 Name of indicator Norm for fiber and tow Top grade I grade II grade one 2 3 four 1. The specific breaking load of the fiber, determined on the device Fo-1C, mN / tex, not less, for linear densities
0.17 tex -   262 2. The elongation of the fiber at break, determined on the device Fo-1C,%, not less, for a linear density of 0.17 tex - 26 23 3. Deviation of the actual linear density of the elementary fiber from the nominal,%, not more than for a linear density of 0.17 tex ± 6.0 ± 7.0 ± 9.0 4. Deviation of the actual linear density of the bundle from the nominal,%, not more than for a linear density of 0.17 tex ± 6.0 ± 7.0 ± 9.0 5. The number of twists per 1 cm, for linear densities of 0.17 tex - 4.4-6.4 3,5-6,4 6. Mass fraction of sizing,% 0.30-0.80 0.30-0.80 0.30-0.80 7. The whiteness of the bleached fiber,%, not less 80.0 80.0 75.0

The content of PAN fiber in the claimed mixture is from 0.1 wt.% To 0.15 wt.% In excess of 100% by weight of the mineral material. The introduction of PAN fiber into the asphalt mix below the lower limit of 0.1 wt.% Does not provide a sufficient level of properties of the mixture and the coating obtained from it, and the use of mixtures with PAN fiber content of more than 0.15 wt.% Can cause PAN clumping fibers when introduced into the mixture. The use of PAN fiber as a reinforcing component is due to the fact that it has an optimal ratio of elastic modulus to specific gravity, while the length of the PAN fiber fibers is preferably from 6 to 12 mm.

As a carbon fiber, the mixture may contain finely chopped carbon fibers with a length of 3 to 40 mm, with an average diameter of 20-22 μm of continuous carbon fiber having the characteristics shown in table 2.

table 2 Name of indicator Units rev. Carbon fiber Monofilament Tear Strength GPa 2.5-2.85 Monofilament Extension % 0.79-2 Modulus of elasticity monofilament GPa 210-230 The number of single fibers million / kg 300-1200 Fiber surface area m ² / kg 150-300 Combustion temperature ° C 3000 Melting temperature ° C does not melt Decomposition temperature ° C does not decompose

Carbon fiber can be introduced into the asphalt mixture in the form of carbon fiber, representing finely divided cut carbon fiber with a length of 4 to 18 mm, as well as waste from various stages of the production of carbon fiber and composite materials based on it, further ensuring the disposal of these waste.

The carbon fiber content in the asphalt mixture is from 0.01 to 0.15 wt.% In excess of 100% by weight of the mineral material. The introduction of carbon fiber into the asphalt mixture with a lower than the lower limit of 0.01 wt.% Does not provide a sufficient level of the properties of the mixture and the coating obtained from it, in particular it does not provide sufficient resistance of the coating to rutting. The use of mixtures with a carbon fiber content of more than 0.15 wt.% Significantly increases the cost of the asphalt mixture without a significant improvement in its properties.

The process of preparing the asphalt mixture is shown in the following embodiments of the invention.

Examples of implementation

The preparation of the mixture is illustrated by examples using mineral material containing 46 wt.% Crushed stone, 46 wt.% Quartz sand and 8 wt.% Mineral powder when 4.5 wt.% Bitumen (over 100% of the mineral material) is introduced into the mixture at various contents of reinforcing filler.

To prepare the claimed asphalt mix, a general method is suitable in which metered amounts of heated crushed stone and sand are fed into a mixer, after which a reinforcing fibrous filler containing PAN fiber and carbon fiber, mineral powder, and then heated bitumen is introduced and mixed until a homogeneous mixture is obtained .

But in order to obtain a more homogeneous mixture and a better distribution of the reinforcing fiber filler additive in the volume of the mixture, the proposed mixing method is optimal, in which the dry powder is first preliminarily mixed with the reinforcing fiber filler in the mixer. The mixing speed specified by the rotational speed of the shaft of the mixer mixers should be maintained in the range from 200 to 1500 rpm, and in these examples it was about 1000 rpm.

After that, the pre-obtained mixture of mineral powder and the reinforcing fiber filler uniformly distributed in it is introduced into the stirred heated crushed stone and fine aggregate, and then heated bitumen is fed and final mixing is carried out until a homogeneous asphalt mixture is obtained.

The physical and mechanical characteristics of the coatings obtained from the asphalt mixture according to the invention, containing 46 wt.% Crushed stone, 46 wt.% Sand quartz and 8 wt.% Mineral powder, with the introduction of 4.5 wt.% Bitumen (in excess of 100% from mineral material) and reinforcing filler with a different ratio of PAN fiber and carbon fiber are shown in table 3.

Table 3 No. Name of indicator Units rev. Requirements for a mixture of grade I type B (according to GOST 9128-97) Initial asphalt mixture of grade I type B + PAN fiber 0.1% PAN fiber 0.045% + carbon fiber 0.005% PAN fiber 0.1% + carbon fiber 0.01% PAN fiber 0.1% + carbon fiber 0.1% PAN fiber 0.15% + carbon fiber 0.15% PAN fiber 0.18% + carbon fiber 0.01% Comparative example Composition 1 Composition 2 Composition 3 Composition 4 Composition 5 one Density g / cm ³ 2.40 2.40 2.40 2.41 2.41 2.41 2 Tensile strength at compression at a temperature of 50 ° C MPa Not less than 1.20 2.2 1.7 2.2 2,3 2,4 2,4 3 Strength at compression at a temperature of 20 ° C MPa Not less than 2.5 6.7 6.2 6.7 6.8 6.8 6.7 four Tensile strength at compression at a temperature of 0 ° C MPa No more than 11.0 15.9 15,2 16.1 16.1 16.7 16.5 5 Water saturation for mixtures % 1.5 to 4.0 3.0 2,8 3.0 3.0 3.0 2,8 6 Tensile crack resistance at split at a temperature of 0 ° C MPa Not less than 3.5 no more than 6.0 4.2 3.9 4.2 4.4 4,5 4.4 7 Shear resistance by internal friction coefficient MPa Not less than 0.81 0.90 0.90 0.90 0.91 0.91 0.91 8 Shear adhesion at shear at a temperature of 50 ° C MPa Not less than 0.37 0.57 0.51 0.57 0.57 0.57 0.56 9 The porosity of the mineral composition % No more than 19 17 17 17 eighteen eighteen eighteen 10 The average rate of rutting at a temperature of 50 ° C, a load of 0.6 MPa mm / 10000 pass
Dov Not standardized 0.62 0.65 0.57 0.44 0.36 0.60

Table 3 also shows the requirements for similar mixtures according to GOST 9128-97, and as a comparative example, indicators are given for a similar asphalt mixture containing only PAN fiber.

Composition 1 contained 0.045 wt.% PAN fiber and 0.005 wt.% Carbon fiber (in excess of 100% of the mineral material) as a reinforcing fibrous filler. Such a content of PAN fiber and carbon fiber in the mixture is lower than the boundary values stated in the claims, and the gauge rate for composition 1 is 0.65 mm / 10,000 passes, which does not provide the required gauge resistance.

Composition 2 contained 0.1 wt.% PAN fiber and 0.01 wt.% Carbon fiber (in excess of 100%), which corresponds to the lower limit value of the declared content of the reinforcing filler. The average rutting rate for composition 2 is 0.57 mm / 10,000 passes, which significantly exceeds that of the comparative example.

A significant decrease in the rutting rate is also observed in composition 3, containing 0.1 wt.% PAN fiber and 0.1 wt.% Carbon fiber (over 100%), and composition 4, corresponding to the upper limit value of the declared content of reinforcing filler and containing 0 15 wt.% PAN fiber and 0.15 wt.% Carbon fiber (in excess of 100%). Moreover, the properties of composition 5, in which a reinforcing filler was used, containing 0.18 wt.% PAN fiber and 0.01 wt.% Carbon fiber, which for PAN fiber exceeds the declared boundary value, are not optimal.

As can be seen from the data shown in table 3, the use of a combination of PAN fiber and carbon fiber in the composition of the reinforcing filler when the mixture contains 0.1-0.15 wt.% PAN fiber and 0.01-0.15 wt.% Carbon fiber (in excess of 100% by weight of the mineral material) allows you to get an overall high level of properties of asphalt concrete pavement and reduce wear of the asphalt concrete pavement, leading to the formation of a rut.

Using the proposed mixture additionally allows you to control the properties of the final asphalt depending on the dosage and the ratio of PAN fiber and carbon fiber in the mixture, while mixtures with a high content of PAN fibers within the stated interval provide an increase in the compressive strength, and an increase in the content of carbon fibers in a larger degree promotes resistance to rutting.

The composition of the proposed asphalt mix and the method for producing it according to the invention significantly increase the resistance to rutting and provide an asphalt concrete pavement that has an average rut formation rate measured at a temperature of 50 ° C and a load of 0.6 MPa, less than 0.60 mm / 10000 passages, which ensures the creation of high-quality and durable asphalt pavement.

Claims (6)

1. Asphalt mixture, including mineral material containing crushed stone, fine aggregate, mineral powder, as well as a bituminous binder and reinforcing fibrous filler containing PAN fiber and carbon fiber, in the following ratio of components of the asphalt mix, wt.%:
crushed stone 30-70 fine aggregate 10-65 mineral powder 5-40 bituminous binder 3-15 (in excess of 100% by weight of the mineral material) PAN fiber 0.1-0.15 (in excess of 100% by weight of the mineral material) carbon fiber 0.01-0.15 (in excess of 100% by weight of the mineral material) 2. The asphalt mixture according to claim 1, which contains a PAN fiber containing fibers with a specific breaking load of at least 262 mN / tex for linear densities of 0.17 tex, while the length of the PAN fiber is 6-12 mm. 3. The asphalt mixture according to claim 1, which as a carbon fiber contains finely cut carbon fibers of a length of 3 to 40 mm from a continuous carbon fiber having a tensile strength of monofilament of at least 2.5 GPa. 4. The asphalt mixture according to any one of claims 1 to 3, which provides a coating of said mixture with a track formation rate of less than 0.60 mm / 10000 passes at a temperature of 50 ° C and a load of 0.6 MPa. 5. A method of preparing an asphalt mixture, including preliminary dry mixing of mineral powder and a reinforcing fibrous filler containing 0.1-0.15 wt.% PAN fiber and 0.01-0.15 wt.% Carbon fiber (in excess of 100% of mass of mineral material), in a mixer at a mixing speed of 200 to 1500 rpm, introducing a previously obtained mixture of mineral powder and said reinforcing fibrous filler into stirred heated crushed stone and fine aggregate, followed by feeding a heated bituminous binder. 6. The method according to claim 5, in which the preliminary mixing of the mineral powder and the specified reinforcing fibrous filler is carried out by heating to a temperature of 45-120 ° C.