RU2656484C1 - Modifier composition for asphalt mixtures - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to road-building materials, namely to modifying asphalt-concrete compositions, and can be used on the device for coating roads, aerodromes, bridges in different climatic zones. Composition comprises a rubber powder having a particle size of not more than 1 mm and a specific geometric surface area of at least 3,500 cm²/g, taken in an amount of 60–75 % of the total weight of the composition, and a filler. At the same the rubber powder is made in the form of crushed rubber, activated by asphalt deasphalting, and the filler is an alumina powder or powder of a material containing alumina as the main component.

EFFECT: technical result consists in obtaining a modifier that does not lead to a decrease in the density of asphalt concrete, as well as in simplifying the technology of obtaining this composition and in expanding the arsenal of asphalt concrete modifiers.

1 cl, 1 tbl, 3 ex

Description

FIELD OF THE INVENTION

The invention relates to road-building materials, namely, modifying compositions based on rubber powders and can be used on the device for coating roads, airfields, bridges in various climatic zones.

The federal target program "Development of the transport system of Russia" determines the need for the development and implementation in practice of road construction of modified asphalt mixes that ensure the durability of road surfaces. The most well-known and widespread modifiers (polymeric materials) that can significantly improve the properties of road surfaces include rubber powders obtained by the disposal of worn tire covers of vehicle wheels and other rubber products made on the basis of non-polar rubbers.

State of the art

It is known that the introduction of rubber powder into asphalt mixtures improves the performance properties of asphalt concrete (V. A. Kuznetsov et al. Auth. St. No. 292917, 1971, B. M. Blind. "Study of the effect of rubber powder on the properties of asphalt concrete." Balashikha, SoyuzDorNII Publishing House, 1972; “Road Asphalt Concrete.” / Under the editorship of Prof. LB Gezentsvei. M., “Transport” publishing house, 1985).

Rubber powders are obtained mainly from the processing of obsolete automobile tires (as well as other rubber products) made on the basis of non-polar rubbers.

The following requirements are imposed on such powders:

- particle size not more than 1.0 mm;

- the value of the specific geometric surface is not less than 3500 cm ² / g.

The resulting rubber powders, satisfying the above indicators, are quickly dispersed in bitumen introduced into the asphalt mixture, and do not lead to an increase in the production time of these mixtures. In addition, such (active) rubber powders retain the basic physical and chemical properties of tire rubbers, which provides them with the ability to connect at the molecular level with petroleum bitumen. The production of such powders on an industrial scale is carried out on the equipment of the Astor Company Limited Liability Company (LLC). The standard of organization is Astor Company LLC STO 2519-004-05263796-2007. RUBBER GRINDED. Specifications, Perm. , registered with FSUE “ROSOBORONSTANDART” on April 23, 2009, entered in the register for No. 200/055470; Patent RU No. 2254992, published on June 27, 2005). On this equipment, as a result of the simultaneous effect of volume compression, shear deformations, the difference in the angular velocities of the surfaces of the grinding tool and intense friction of the surface layers of the material, the process of grinding stressed rubber in air is a chain mechanochemical process of alternating interdependent physical and chemical stages. An important feature of grinding rubbers in the apparatus of Astor LLC is the relatively low process temperature (145-150 ° C). At these temperatures, the elastic component of the deformation of the rubbers is preserved, which provides an increased ability of the powders to combine with petroleum bitumen. This leads to an increase in strength, to a decrease in the formation of cracks and ruts in asphalt concrete pavements.

Known modifying composition for asphalt mixtures based on rubber powder (prototype), including, based on the total weight of the composition:

- from 60 to 75 wt.% active rubber powder, a tire product (vehicle tire covers) and / or rubber products with a particle size of not more than 1 mm and a specific geometric surface of at least 3500 cm ² / g;

- filler, which is ground mica or a mixture of ground mica and diatomite, containing from 15 to 25 wt.% ground mica and from 5 to 10 wt.% diatomite,

- from 1.0 to 2.5 wt.% adhesive and

- from 1.0 to 2.5 wt.% structuring additives,

where the active rubber powder is a rubber powder with a developed specific surface obtained by thermomechanical grinding, or a rubber powder chemically activated with petroleum oil, or a mixture thereof (see the description of the invention to patent RU No. 2458083, publ. 10.08.2012).

Signs of the known composition that match the features of the claimed invention are that it contains an active rubber powder with a particle size of not more than 1 mm and a specific geometric surface of at least 3500 cm ² / g, taken in an amount of 60 ÷ 75% of the total mass composition, and filler.

The reason that prevents obtaining the technical result in the known modifying composition, which is provided by the invention, is that the introduction of a known modifier based on rubber powder into asphalt concrete leads, on the one hand, to an increase in the strength and shear stability of asphalt concrete at elevated temperatures, as well as to an increase in stability to rutting, and on the other hand, to a decrease in the density of asphalt concrete, which is one of the most important indicators providing a corrosion resistance ivost asphalt concrete with prolonged water saturation and alternate freezing-thawing. In addition, the production technology of the known modifier is complex due to the relatively large number of components.

The technical problem to which the invention is directed is the need to create a modifier based on rubber powder, which, while retaining the known advantages of asphalt concrete modified with rubber powder, would not lead to a decrease in the density of this asphalt concrete due to the presence of the specified rubber powder in asphalt concrete. The technical problem also lies in the need to simplify the technology for producing a modifying composition based on rubber powder. The technical problem also lies in the need to expand the arsenal of asphalt concrete modifiers.

Disclosure of the invention

The technical result that mediates the solution of this technical problem is that the introduction of rubber powder into the asphalt mixture does not reduce the density of the asphalt due to the compensating effect of the filler (together with asphalt deasphalting). Moreover, due to the activation of the rubber powder by deasphalting asphalt (diffusion of deasphalting asphalt into the micropores of the rubber), the adhesion of the bitumen film to the surface of the particles of the rubber powder is improved, which improves the interaction of the rubber powder with bitumen during the preparation of the asphalt mixture. The technical result also consists in simplifying the technology for producing the modifying composition by reducing the number of ingredients necessary and sufficient to obtain the modifying composition. The technical result also consists in expanding the arsenal of asphalt concrete modifiers.

The technical result is achieved by the fact that the modifying composition for asphalt mixtures contains activated asphalt deasphalting rubber powder with a particle size of not more than 1 mm and a specific geometric surface of at least 3500 cm ² / g, taken in an amount of 60 ÷ 75% of the total weight of the composition, and filler, which is an alumina powder or a powder of a material containing alumina as a main component. The technical result is also achieved by the fact that the above crushed rubber is obtained from worn tire covers of wheels of vehicles by mechanical destruction of these tires with subsequent regrinding at a temperature of not more than 150 ° C.

The implementation of the invention

The modifying composition for asphalt mixtures is a mixture of rubber powder activated by deasphalting asphalt, in the amount of 60 ÷ 75% of the total weight of the composition, and a filler, which is an alumina powder or a powder of a material (mixture) containing alumina as the main component ( rest).

The requirements for rubber powder and the technology of its production are determined by the Standard of Astor Company Limited Liability Company (Perm) STO 2519-004-05263796-2007. GRINDED RUBBER (Technical conditions), entered into the register of the Federal Service for Defense Orders on 04.23.2009 for No. 200/055470. In accordance with this standard, rubber powder (crushed rubber) is obtained from worn tires according to GOST 8407 by mechanical destruction of tires with subsequent regrinding on rotary knife crushers and fine grinders and separation of textile and metal cord. The rubber powder thus obtained (for the purpose of its use in a modifying composition) has the following basic parameters: particle size of not more than 1 mm; the value of the specific geometric surface is not less than 3500 cm ² / g; mass fraction of cord cord residues (viscose, kapron, etc.) not more than 3.0%; humidity not more than 1.5%; mass fraction of ferrous metal particles not more than 0.02%; mass fraction of rubber of other fractions (rubber particles outside the range of the specified fraction) is not more than 15%; complete absence of mechanical impurities (sand, stones, etc.). In addition, a significant technological parameter that affects the properties of rubber powder, important from the point of view of its use in the modifying composition, is the relatively low process temperature (145 ÷ 150 ° C). At such temperatures, the elastic component of the rubber deformation is preserved, which provides an increased ability of the rubber powder particles to combine with petroleum bitumen, polymers and crude rubber.

Asphalt deasphalting is a waste in the production of residual oils (bitumen with a low oil content). Deasphalting asphalt, in contrast to residual and oxidized bitumen from the same oil, contains less solid paraffins. The presence of paraffin in bitumen reduces adhesion, so its content should not exceed 5%. For example, residual bitumen may contain 1.6% (mass.) Paraffin, and asphalt deasphalting with propane of the same bitumen - 0.8% (mass.) (Gun RB Oil bitumen. M., "Chemistry", 1989, p. 118).

Asphalt deasphalting is used (in accordance with the invention) to activate the rubber powder in order to improve its interaction with bitumen in the preparation of the asphalt mixture; to improve the adhesion of the bitumen film to the surface of the particles of rubber powder. To do this, deasphalting asphalt is heated to a temperature of 140 ° C, introduced into a rubber powder in an amount of 10% by weight of the powder, thoroughly mixed to a homogeneous state, and then left for a day (24 hours). When mixing and further maintaining the mixture of rubber powder and deasphalting asphalt, deasphalting asphalt (resins and asphaltenes) diffuses into the rubber micropores and, accordingly, activates the surface of the rubber particles.

As a filler in the claimed modifying composition used powder with a density of the powder material of at least 3.75 g / cm ³ . In an advantageous embodiment, alumina (Al ₂ O ₃ ) powder is used as filler. For this purpose, a powder of a material (a mixed substance) containing alumina as the main component (i.e., at least 50% of the total filler mass) can also be used.

To obtain the claimed modifying composition, take, for example, 60% of asphalt-activated deasphalting rubber powder, which is mixed with 40% of said filler until uniform.

The high density of the filler in combination with activated asphalt deasphalting rubber powder allows to obtain asphalt concrete with a density corresponding to serial asphalt concrete (without modifier) while maintaining all the known advantages of using rubber powder as an asphalt concrete modifier.

This is confirmed by the following results of comparative studies of various asphalt concrete: composition No. 1 - without modifier (serial asphalt concrete); composition No. 2 - with the modifier of the prototype (patent RU No. 2458083 C1); composition No. 3 - with the declared modifier, in which a powder of a material (mixed substance) containing α-alumina in an amount of up to 70% of the total mass of the filler is taken as a filler.

Composition No. 1 (serial asphalt concrete):

Crushed stone of fraction 5-20 ......... 40%

Crushed stone of fraction 5-10 ......... 15%

Screening crushing ................... 41%

Mineral powder ....... four%

    ∑ = 100%

+ Bitumen BND 90/130 ........... 4.5%

Composition No. 2 (asphalt concrete with a modifier according to patent No. 2458083):

Crushed stone of fraction 5-20 ......... 40%

Crushed stone of fraction 5-10 ......... 15%

Screening crushing ................... 41%

Mineral powder ....... four%

    ∑ = 100%

+ Bitumen BND 90/130 ........... 4.5%

+ Modifier according to the specified patent ... 0.5%

Composition No. 3 (asphalt concrete with the declared modifier):

Crushed stone of fraction 5-20 ......... 40%

Crushed stone of fraction 5-10 ......... 15%

Screening crushing ................... 41%

Mineral powder ....... four%

    ∑ = 100%

+ Bitumen BND 90/130 ........... 4.5%

+ Modifier declared ... .. ... 0.5%

Indicators of physico-chemical properties of these asphalt concrete (compositions 1-3) are shown in the following table:

No. p / p The name of indicators Serial Asphalt Concrete Modified Asphalt Concrete Requirements according to GOST 9128 (I mark) Composition No. 1 Structure
Number 2 Composition No. 3  one The average density, g / cm ³  2.66  2.60  2.65 -  2 The limit of compressive strength, MPa
at 20ºС not less
at 50ºС not less
at 0ºС no more

3.95
2.12
7.3

4.78
2.11
8.69

4.86
2.04
9.65

2,5
1,0
11.0  3 Water resistance, not less 0.97  0.98  0.94 0.90  four Water resistance during prolonged water saturation, not less 0.94  0.85  0.85 0.85

5 Shear resistance by:
- coefficient of internal friction, not less
- adhesion at shear at a temperature of 50ºС, not less

0.92

0.48

0.95

0.48

0.94

0.51

0.87

0.25

Thus, asphalt concrete with the declared modifier (composition No. 3) has almost the same density as asphalt concrete without a modifier (composition No. 1). In addition, the claimed modifier differs from the known lower content of components, which simplifies the technology of its production.

Claims (2)

1. Modifying composition for asphalt mixtures containing rubber powder with a particle size of not more than 1 mm and a specific geometric surface of at least 3500 cm ² / g, taken in an amount of 60-75% of the total weight of the composition, and a filler, characterized in that the rubber powder is made in the form of crushed rubber activated by deasphalting asphalt, and the filler is alumina powder or a powder of a material containing alumina as the main component. 2. The modifying composition according to claim 1, characterized in that said crushed rubber is obtained from worn tires of wheels of vehicles by mechanical destruction of these tires with subsequent regrinding at a temperature of not more than 150 ° C.