RU2215084C1 - Method of preparation of asphalt-concrete mix - Google Patents

Abstract

FIELD: manufacture of building materials, particularly, asphalt-concrete mix; applicable at asphalt plants and other construction organizations. SUBSTANCE: method including use of bitumen and mineral component from sand, crushed stone, screenings of stone crushing and mineral powder and consists in sizing of sand, crushed stone and screenings of stone crushing, grinding of a sand, portion in disintegrator, dosing of components of mineral component and their mixing, heating of components of asphalt-concrete mix, mixing of mineral component with bitumen. Additionally introduced into composition of mineral component is mineral filler in amount of 2-3 wt.% of mineral component. Mineral filler is produced by adding of lime in grinding of sand in disintegrator, with lime-sand ratio equaling (00:40)-(90:10) wt.p.p. In preparation of asphalt-concrete mix, components of mineral part are subjected to cold dosing and cold mixing. In this case, lime fulfils function of sand activator. Slaked and nonslaked lime are usable in method. EFFECT: higher service properties of asphalt-concrete and economic efficiency of method, reduced amounts of liberated impurities (dust, gases, etc). 2 cl, 1 dwg, 2 tbl

Description

 The invention relates to the field of production of building materials, in particular asphalt mixture, and can be used in asphalt plants and other construction industries.

A known method of preparing an asphalt mixture, including mixing the mineral aggregate with moistened mineral powder and heated bitumen (see US Pat. RF 2040502 IPC ⁶ C 04 V 26/26, E 01 C 7/18, 07/27/1995 Bull. 21).

 The disadvantage of this invention is the need for additional wetting of the mineral powder, as well as low rates of long-term water resistance: 0.70-0.89.

A known method of preparing asphalt mix, comprising mixing in a high-speed disintegrator solid bitumen with mineral powder, sand and subsequent heating of the mixture in a furnace (see US Pat. RF 1756302 A1 IPC ⁶ C 04 V 26/26, 08/23/1992, Bull. 31) .

 The disadvantage of this method is the low value of the coefficient of long-term water resistance: 0.85 - 0.90.

The closest in technical essence and the achieved result is a method of preparing an asphalt concrete mixture, including sorting sand and gravel by fractions, selecting materials with grain sizes from 0.5 to 5 mm, grinding mineral powder from selected material fractions of 0.5-5 mm on a disintegrator, dosage of the components, mixing them together, and then with bitumen (see US Pat. RF 2083754 C1 IPC ⁶ E 01 C 19/10, B 02 C 13/06 10.07.1997, Bull. 19).

The disadvantages of the prototype are:
1) reduction of the service life and reliability of equipment due to premature wear of the disintegrator organs when using hard rocks (granite, quartz, etc.);
2) obtaining asphalt concrete with low physical and mechanical properties when using crushed rocks with a negative surface charge as a mineral powder;
3) the technological difficulty of obtaining an asphalt concrete mixture lies in the strict selection of particles of sand and crushed stone with a size of 0.5-5 mm, which requires the use of additional equipment.

 The aim of the invention is to increase the operational properties of asphalt concrete and reducing the amount of emitted pollution (dust, gases, etc.).

 The result is achieved in that in a method for preparing an asphalt concrete mixture comprising bitumen and a mineral component from sand, gravel, crushed stone screenings and mineral powder, consisting in sorting sand, crushed stone and crushed stone screenings, grinding part of the sand in a disintegrator, dosing the components of the mineral component and mixing them, heating the components of the asphalt mixture, mixing the mineral component with bitumen, the mineral component is additionally introduced into the composition of the mineral component 2–3 wt.% calculated on the mineral component obtained by adding lime when grinding in a sand disintegrator, while the ratio of sand to lime is chosen to be 60:40 ÷ 90:10 (parts by weight), and when preparing the asphalt mixture cold dosing and cold mixing of the components of the mineral part.

 The result is also achieved by the fact that lime is used both slaked and quicklime.

For the preparation of ABS used:
- coarse mineral components: crushed stone fractions of 3-10 mm and 5 -20 mm according to GOST 8267-93, medium-sized sand according to GOST 8736-93, to improve the structure and increase the density of the mixture, crushed stone crushing screenings according to GOST 8736-93 were introduced into the compositions and GOST 9128-97;
- mineral powder in accordance with GOST 16557-78;
- lime components according to GOST 9179-77, sand of medium size GOST 8736 -93 were used as components of the mineral filler;
- bitumen was used grade BND 90/130 according to GOST 22245-90.

 The drawing shows a flow chart of the production of asphalt mix. From warehouse 1, coarse dispersed ABS mineral components (sand, gravel, screening crushed stone crushing) are fed through a cold metering unit 2 to a screen 3, divided into fractions, fed to a hopper 4. The required amount of sand is fed to a disintegrator 5, and from the hopper 6 to the same lime comes in. This method uses a disintegrator having a working body in the form of square fingers, which makes it possible to grind and activate the surface of the particles of components more efficiently than the circular cross section and contributes to more efficient use of fingers, since a worn working surface can be changed to unworn. For the preparation of mineral filler can be used both slaked and quicklime, which acts as an activator of sand. The ratio of sand to lime was chosen equal to 60:40 - 90:10 (parts by weight). After grinding a mixture of sand and lime in a disintegrator, a mineral filler is obtained. The composition of the mineral component uses a standard mineral powder, the amount of which is regulated by GOST 9128-97 "Mixtures of asphalt road, airfield and asphalt concrete. Technical conditions" and depends on the type of asphalt concrete, i.e. from its particle size distribution. To prepare samples of the composition of the asphalt mix (according to the examples of Table 1), 6 wt.% Of the mineral powder was added to the mineral component.

 A method of preparing an asphalt mixture (ABS) is as follows. Sand, crushed stone and crushed stone crushing screen are fed from the bins 4 through the batcher 8 to the cold mixing mixer 7, mineral filler is fed from the disintegrator, mineral powder is transported from warehouse 9 through the feed hopper 10. From the mixer 7, the ABS mineral component is sent to a drying and mixing plant 11, where the material is heated to operating temperature. Then, from the working boiler 12 through the dispenser 13, bitumen preheated to the operating temperature is fed into the mixing part of the installation 11 and the ABS components are mixed. The preset operating temperature of mineral materials, a binder (bitumen) and a mixture depends on the viscosity index of the binder and is standardized according to GOST 12801-98 "Materials based on organic binders for road and airfield construction. Test methods." Ready ABS is fed to the hopper-filler 14 or loaded into a dump truck 15.

 The compositions of the ABS are shown in table. 1, the properties of the resulting asphalt concrete - in table. 2.

 The proposed method is intended for the preparation of hot and warm asphalt mixtures. These mixtures are used for the device of the upper layers of the coating of roads, airfields, city streets and squares, roads of industrial enterprises.

The advantages of the proposed method include:
- increase in the coefficient of long-term water resistance, and, accordingly, the service life of asphalt concrete pavement;
- reduction in water saturation and swelling;
- an increase in compressive strength;
- the use of freshly ground filler makes it possible to save bitumen up to 1.5% due to the high surface activity of the filler components;
- through the use of a method for preparing asphalt concrete mix by cold dosing, the ecology of the production of asphalt concrete is improved;
- saving of thermal energy due to the exclusion of preliminary drying of the mineral material and more rational organization of the technological process, which eliminates heat loss in the intermediate operations for the production of asphalt mix;
- elimination of the need to build additional warehouses for storage and aggregates for feeding filler.

Claims (2)

 1. A method of preparing an asphalt mixture, including bitumen and a mineral component from sand, gravel, screenings of crushing crushed stone and mineral powder, which consists in sorting sand, crushed stone and screenings of crushing crushed stone, grinding part of the sand in a disintegrator, dosing the components of the mineral component and mixing, heating components of the asphalt mixture, mixing the mineral component with bitumen, characterized in that the mineral component is additionally injected with a mineral filler in an amount of 2-3 wt. % based on the mineral component obtained by adding lime during grinding in a sand disintegrator, while the ratio of sand to lime is chosen equal to, wt. hours: 60: 40 ÷ 90: 10, and in the preparation of the asphalt mixture produce cold dosing and cold mixing of the components of the mineral component.  2. The method according to p. 1, characterized in that the lime is used as slaked or quicklime.

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