RU2415165C1 - Rubber stone-mastic asphalt mix - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to road construction and can be used in road pavement in all climatic regions. The invention relates to a rubber stone-mastic asphalt mix for road construction which contains road bitumen, crushed stone, sand from grinding screenings, mineral powder and a stabilising additive. The mineral powder used is rubber crumbs with size of up to 1 mm and the stabilising additive used is low-density secondary linear polyethylene, with the following ratio of components in wt %: crushed stone 60-84; road bitumen 5.5-7.5; rubber crumbs 1.0-1.8; low-density secondary linear polyethylene 0.2-0.8; sand from grinding screenings - the rest.

EFFECT: improved physical and mechanical characteristics of the stone-mastic asphalt mix.

1 ex, 4 tbl

Description

The invention relates to the construction of roads and airfields and can be used in the device of the upper layers of pavement.

The specificity of the structure of crushed stone-mastic asphalt concrete (ASHMA) provides for their composition with an increased content of crushed stone, bitumen and mineral powder, which makes it possible to create a material resistant to cracking and shear deformations. At the same time, in the process of production of crushed stone and mastic asphalt concrete mixtures, various stabilizing additives are added to them, the main purpose of which is to hold a bituminous binder not adsorbed by the surface of the mineral aggregate, and to prevent the separation of alkali mixtures during its preparation, storage, transportation and placement.

In most formulations, free or granular fibers (cellulosic, polymeric or other) are used as stabilizing additives in AHMA mixtures, which are supplied to the mixture in the required amount during its preparation. They include imported additives based on cellulose fibers, specially manufactured for road construction, for example, VIATOP, TORSEL, ANTROCEL, etc. The disadvantage of such additives is the high cost and the need for additional technological steps in the preparation of alkali mixtures for the introduction of bitumen adhesive additives to improve the adhesion of the binder to the surface of the mineral material.

Thus, the use of durable crushed stone with an improved (cuboid) shape of grains, a high content of bitumen and mineral powder, expensive stabilizing and adhesion additives as a part of ASM makes this material much more expensive than traditional asphalt concrete.

A number of inventions are known (US Pat. RF 2312116, US Pat. RF 2273615, US Pat. RF 2274617), which solve the problem of improving the quality and reducing the cost of a stabilizing additive, without improving the properties of alkaline alkaline microsat.

The main direction of improving the properties of alkali alkaline alkaline alkali sulfate is the introduction of various polymer components into a stabilizing additive, but this does not solve the problem of reducing the cost of alkaline alkaline alkaline alkaline alkaline microxyaniline.

Known stabilizer for alkaline amalgam, including cellulose fiber and oxidized atactic polypropylene (US Pat. RF 2348662). This composition ensures the stability of the alkali mixtures during storage, transportation and installation, provides a higher level of adhesive properties of bitumen or asphalt binder with the mineral components of the mixture during its preparation, increases the water resistance of alkali mixtures without prior modification of bitumen. However, it does not affect its strength characteristics.

Known SCHMA using in its composition additives, including astringent, rubber crumb, mineral oil and polymer (US Pat. RF 2222559). In this case, a bitumen emulsion is used as a binder, polyacrylamide is used as a polymer and, in addition, cellulose fibers and aluminosilicate are used as a binder. However, in the technical solution of the invention, the composition of the mixture is shown and only one of its properties is runoff, so the effect of the additive on the basic properties of alkaline alkali metal oxide is not clear.

Known stabilizing bitumen-rubber compositions for asphalt paving, in which rubber is used in the form of fine crumbs (US Pat. Japan 279573, US Pat. 5683498) to improve the performance characteristics of the coating. The disadvantage of these compositions is that rubber crumbs that are not fixed in the mixture will inevitably stand out from the coating during operation.

Known polymer-reinforcing granular stabilizer for alkaline amalgamate, including bitumen, polyamide fiber, a polymer-reinforcing additive from waste waterproofing pipelines, and as an adhesive - surfactant cationic type (US Pat. RF 2272795). A significant drawback is the use of a large number of expensive materials and multi-stage stabilizer preparation technology.

The closest analogue of the proposed invention in terms of technical nature and the achieved result are SchMA mixtures for road construction according to GOST 31015-2002 “Asphalt concrete mixtures and crushed stone-mastic asphalt concrete. Specifications ”, including road bitumen (5.5-7.5%), crushed stone (40-95%), sand from crushing screenings (5-30%), mineral powder (10-20%) and a stabilizing additive (0 , 2-0.5%). In this case, the stabilizing additive mainly provides only the stability of the mixture to delamination.

The disadvantages of the well-known SchMA mixtures should be recognized as low values of tensile strength (at 20 ° C, 2.0-2.5 MPa is sufficient; at 50 ° C - 0.6-0.7 MPa) and the coefficient of water resistance during prolonged water saturation (0.75- 0.90), as well as their high cost.

The technical task of the invention is to obtain resistant to delamination of rubberized gravel-mastic asphalt concrete (RCA) mixtures with improved physical and mechanical properties and lower cost due to the use of recycled materials, as well as reducing environmental damage due to waste disposal: used car tires and linear low density polyethylene.

The essence of the invention lies in the fact that the rubberized crushed stone and mastic asphalt concrete mix for road construction, including road bitumen, crushed stone, sand from crushing screenings, mineral powder and a stabilizing additive, while the mixture contains rubber crumb up to 1 mm in size as a mineral powder, and as a stabilizing additive, secondary linear low density polyethylene, in the following ratio of components, wt.%:

Crushed stone 60-84 Road bitumen 5.5-7.5 Rubber crumb 1.0-1.8 Secondary linear low density polyethylene 0.2-0.8 Sand from crushing screenings rest

The introduction of finely divided rubber crumbs together with a polyolefin component (secondary linear low density polyethylene) instead of mineral powder contributes to the improvement of the whole complex of physicomechanical properties of alkali mixtures. This effect is associated with the peculiarity of the resulting structure: the crushed stone frame is connected by an unconventional asphalt binder (mineral powder and bitumen), and the rubber-polymer-bitumen binder, more resistant to cracking and plastic deformation. In addition, the rubber crumb also plays the role of a stabilizer, and the mixture proposed by SCMA is cheaper, because it uses recycled materials instead of mineral powder and expensive stabilizing additives. The use of crumb rubber - a product of the processing of worn-out car tires, contributes to their disposal, which is of great environmental and economic importance. This is due primarily to the fact that worn tires are a source of long-term environmental pollution. In addition, rubber is flammable and not biodegradable, and a bunch of rubber tires is a fairly convenient place to live entire colonies of rodents and insects, many of which are a source of infectious diseases.

Tire recycling is preferred because 80% of the world's tire supply is made from synthetic rubber, which is derived from oil, a non-renewable natural resource. The technology of tire recycling, and not their storage, burial and incineration, is of great economic importance, since in this case the natural reserves of valuable raw materials are preserved, the environmental situation is improved and the loss of large areas of land for rubber waste dumps is eliminated.

Characteristics of raw materials

1. Crushed stone.

Crushed stone - inorganic granular granular material with grains larger than 5 mm, obtained by crushing rocks, gravel and boulders, simultaneously mined overburden and host rocks or substandard waste from mining enterprises for the processing of ores (ferrous, non-ferrous and rare metals of the metallurgical industry) and non-metallic minerals of other industries and subsequent screening of crushing products.

Granite crushed stone produced by Pavlovskgranit OJSC of the Voronezh Region was used to prepare the RCMA mixtures. The main properties of crushed stone are presented in table 1.

Table 1 Main properties of crushed stone of Pavlovskgranit OJSC Breed Crushability mark Abrasion Grade Brand for frost resistance The content of grains lamellar and needle-shaped,% by weight The content of crushed grains,% by weight Granite 1200 I1 F50 No more than 15 Not less than 85

2. Sand from screenings of crushing of granite crushed stone.

Sand is a sedimentary rock, as well as artificial material consisting of rock grains. Very often it consists of an almost pure mineral of quartz (the substance is silicon dioxide).

For the preparation of RCMA mixtures, sand was used from the screenings of crushing granite crushed stone: the strength grade is 1000, the content of clay particles determined by the swelling method is not more than 0.5%.

3. Road bitumen.

Bitumens (from Latin bitumen - mountain resin) - solid or resinous products, which are a mixture of hydrocarbons and their nitrogen, oxygen, sulfur and metal derivatives. Bitumens are insoluble in water, completely or partially soluble in benzene, chloroform, carbon disulfide and other organic solvents, with a density of 0.95-1.50 g / cm ³ .

For the preparation of RCMA mixtures, BND 60/90 oil road bitumen was used. The main properties of bitumen are presented in table 2.

table 2 Physical and mechanical properties of bitumen BND 60/90 Needle penetration depth, 0.1 mm The softening temperature of the ring and ball, ° C Stretch, cm Fragility temperature, ° C Flash point ° C Change in softening temperature after heating, ° C at + 25 ° C at 0 ° C at + 25 ° C at 0 ° C 75 23 43 > 100 5,0 -17 235 3

4. Secondary linear low density polyethylene (LLDPE-V) is made from a previously used stretch film by crushing it, washing it from foreign impurities and regranulating. Its physico-chemical characteristics are shown in table 3.

Table 3 Physico-mechanical properties of secondary linear low density polyethylene (LLDPE-V) Density, kg / m ³ at 23 ° C at 20 ° C 918-923
920-925 Melt flow rate at 190 ° C and a load of 2.16 kg, g / 10 min 1,5-2,4 The spread of the melt flow index within the batch,%, no more ± 10 The number of inclusions, pcs., No more twenty The ratio of the melt flow rate PTR _21.6 / PTR _2.16 20-35 Tensile yield strength, MPa, not less 10 Tensile strength, MPa, not less 28 Elongation at break,%, not less than 700

5. Rubber crumb.

Rubber crumb is a product of the processing of used automobile tires.

We used rubber crumb with a particle size of up to 1 mm, manufactured in accordance with TU 38-108035-97.

Example. For experimental verification of the claimed compounds were prepared 5 variants of mixtures. Samples were prepared as follows: granules of secondary polyethylene were introduced into mineral materials (crushed stone and sand from crushing screenings) preheated to 190 ° C. The mixture was stirred in a laboratory stirrer for 1 minute. Then bitumen and crumb rubber were fed into it, and the mixture was further mixed for 2 minutes. After that, cylindrical samples with a diameter of 71.4 mm according to GOST 12801-98 were prepared from it. Traditional mixtures were prepared according to GOST 31015-2002 with the addition of Viatop on bitumen BND 60/90 and the developed rubber compounds with different percentages of rubber crumb from 0.8 to 2.0 in 0.2% increments and secondary linear low-density polyethylene from 0, 1 to 1.1 in increments of 0.2% with their total content of 1.9-2.1% by weight of the mineral material. From the comparative tests and analysis of the results found that asphalt mixtures of the proposed compositions have better physical and mechanical properties compared with the mixtures of the prototype.

The best performance of the proposed asphalt mixture was observed with the introduction of crumb rubber in the range from 1.0 to 1.8% by weight of the mineral material and secondary linear low density polyethylene in the range from 0.2 to 0.8%.

The investigated mixtures and test results of asphalt concrete are shown in table 4.

From the results shown in table 4, it can be seen that the samples from the proposed composition are characterized by increased strength at 20 and 50 ° C, shear adhesion and long-term water resistance coefficient.

Thus, the obtained data indicate that the proposed RCMA is characterized by increased deformation resistance, crack resistance and water resistance compared to the prototype.

In addition, the developed composition ensures the disposal of worn-out car tires, which in the modern world, where the number of cars is growing steadily, acquires great environmental and economic importance.

The proposed RCMA due to the use of secondary raw materials instead of mineral powder and expensive stabilizing additives is much cheaper than analogues.

Claims (1)

The rubberized crushed stone and mastic asphalt mix for road construction, including road bitumen, crushed stone, sand from crushing screenings, mineral powder and a stabilizing additive, characterized in that the mixture contains rubber crumb up to 1 mm in size as a mineral powder, and as a stabilizing additive - secondary linear low density polyethylene in the following ratio, wt.%:
Crushed stone 60-84 Road bitumen 5.5-7.5 Rubber crumb 1.0-1.8 Secondary linear low density polyethylene 0.2-0.8 Sand from crushing screenings Rest