RU2354623C1 - Asphalt concrete mix - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: road construction materials include organic binder and can be applied in obtaining asphalt concrete mixes used in I-IV grade highway surface construction in I-IV climate zones, as well as airfield surfaces and floors in business premises. Asphalt concrete mix includes sand, bitumen and mineral powder of reused asphalt concrete at least partially milled to size under 1.25 mm, with powder content in the mix within 1 to 20 wt %. Milling of reused asphalt concrete is performed by electromagnetic reducer of alternate current with 35 to 100 Hz frequency, with electric current direction alternating 35 to 100 times per second, at constant magnet presence in work chamber in amount from 50 to 90 vol. %.

EFFECT: increased point of break of asphalt concrete articles.

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Description

The invention relates to the field of building materials, in particular building road materials containing an organic binder, and can be used in the preparation of asphalt mixtures used for the coating of roads of categories I-IV in climatic zones I-IV, as well as aerodrome covered and floors in office space.

Known (SU, copyright certificate 975754, 1982) is an asphalt concrete mixture containing bitumen, sand and industrial waste - heavy shale fusas, which include shale resin, water and the mineral part.

A disadvantage of the known asphalt mixture should be recognized as a low tensile strength while high water saturation.

Also known (SU, copyright certificate 742407, 1980) is an asphalt mixture containing bitumen, sand and caprolactam production waste - spent filter powder tripoli.

A disadvantage of the known asphalt mixture should be recognized as a low tensile strength while high water saturation.

The closest analogue of the proposed asphalt mix can be recognized asphalt mix in accordance with GOST 9128-97 "Mixes asphalt concrete road, airfield and asphalt concrete". M., MNTKS, 1998, containing bitumen, mineral powder and sand.

A disadvantage of the known asphalt mixture should be recognized as a low tensile strength of asphalt concrete products while their high water saturation.

The technical problem solved by the proposed composition of the asphalt mix is to obtain a sand asphalt mix with improved physical and mechanical properties.

The technical result obtained by the implementation of the asphalt mix of the proposed composition is to increase the tensile strength of asphalt concrete products.

To obtain the indicated technical result, it was proposed to use an asphalt concrete mixture containing sand, bitumen and mineral powder, moreover, used asphalt concrete was used at least partially crushed using an electromagnetic grinder to the size not exceeding 1.25 mm. Preferably, the content of used asphalt in the mixture ground using an electromagnetic grinder is from 1 to 20% by weight.

A feature of the proposed asphalt mix should be recognized as the introduction into its composition of crushed to a size less than 1.25 mm of used asphalt concrete.

The production process of the grinding product - crushed used asphalt concrete includes the following steps:

- milling of asphalt concrete with a road mill,

- crushing and separation of asphalt concrete chips into fractions using a crushing and screening plant.

- the final grinding of a fine fraction of 0-5 mm is produced in an electromagnetic grinder. With such grinding, the particle size distribution of the grinding product approaches the particle size distribution of the mineral powder (all particles are finer than 1.25 mm).

The grinding of used asphalt concrete to the indicated dimensions can be carried out in an electromagnetic grinder containing a housing (inductor) made of copper or aluminum busbars and a working chamber placed in the inductor. The working chamber can be made of both ferromagnetic materials (sheet steel) and diamagnetic materials (rubber, glass, polymeric material, fiberglass, etc.). In the loading chamber, a hatch is made for the receipt of the crushed material, as well as a hatch for removing the crushed components of asphalt concrete. To hold the magnetic shredders in the chamber volume, use the magnetic field of the inductor and the output grid.

An alternating electromagnetic field creates an electric current passing through the turns of the inductor.

Permanent magnets have south and north poles. The alternating electromagnetic field of the inductor is sinusoidal, pulsating and, since an alternating electric current with a frequency of 35 to 100 Hz is used, the direction of the electric current changes from 35 to 100 times per second, respectively, the current frequency. At the same time, the alternating magnetic field created by the alternating electric field changes. Permanent magnets try to turn around their axis as many times a minute, but since of them in the working chamber from 50 to 90% by volume, then they, colliding with each other, acquire a chaotic, Brownian boiling motion, i.e. form a magneto-boiling layer. Each permanent magnet has its own magnetization vector and magnetic torque.

As was experimentally established, asphalt concrete, in which the mineral powder is completely or partially replaced by the grinding product of used asphalt concrete, has a higher compressive strength. This is achieved due to the fact that the surface of the feedstock already containing bitumen is subjected to mechanical activation in an electromagnetic grinder.

In the case when the mineral powder is completely replaced by the grinding product, the maximum content of the grinding product must correspond to the maximum possible content of the mineral powder for a particular type of asphalt concrete mixture. When using a smaller amount of the grinding product, mineral powder is added to the mixture (to ensure that the grain composition of the mixture meets the technical requirements).

So, for example, for a sandy asphalt mixture of type “D” the amount of input grinding product can be in the range from 1 to 20%.

In order to assess the effect of the grinding product of previously used asphalt concrete on the strength of new asphalt concrete, a series of experiments was performed in which the mineral powder was initially partially and then completely replaced with the specified grinding product.

Table 1 shows the used composition of the samples (% wt.)

Table 1 No. p / p Applicable Materials Composition No. 1 Composition No. 2 Composition No. 3 Composition No. 4 Composition No. 5 Composition No. 6 Composition No. 7 one Natural sand,% 73 76 70 73 76 72 72,2 2 Mineral powder,% twenty 16,2 18.2 10 2.2 0 0 3 Product grinding% 0 one 5 10 fifteen twenty 21 four Bitumen,% 6.8 6.8 6.8 6.8 6.8 6.8 6.8

The use of the same amount of bitumen in model mixtures makes it possible to unambiguously compare the strength characteristics of asphalt concrete.

The strength characteristics of asphalt concrete mixtures under compression for the indicated model compositions are given in Table 2.

table 2 Indicator Composition No. 1 Composition No. 2 Composition No. 3 Composition No. 4 Composition No. 5 Composition No. 6 Composition No. 7 The compressive strength at 50 ° C, MPa 1.34 1.65 1,69 1.75 1.81 1.87 1.83

When checking the physical and mechanical properties of the asphalt concrete sample, GOST 12801-98 (test methods) was used.

Introduction to the known, close to the recommended in accordance with GOST 9128-97, the composition of the asphalt mix crushed to a size of not more than 1.25 mm of previously used asphalt in a preferred amount of from 1 to 20% wt. provides increased tensile strength of the new finished asphalt concrete pavement.

Claims (1)

An asphalt concrete mixture containing sand, bitumen and mineral powder from at least partially crushed to a size not exceeding 1.25 mm of used asphalt concrete when its content in the mixture is from 1 to 20 wt.%, Moreover, to grind used asphalt concrete we used an electromagnetic grinder with alternating electric current with a frequency from 35 to 100 Hz, with a change in the direction of electric current from 35 to 100 times per second, with the content of permanent magnets in the working chamber of the grinder from 50 to 90 vol.%.