RU2500636C1 - Rubberised asphalt concrete mixture for bases and lower layers of coating - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to field of road-building materials and can be applied for creation of bases and lower layers of automobile roads and aerodrome pavements in all climatic zones. Rubberised asphalt concrete mixture for bases and lower layers of pavements includes road-metal, sand and bitumen. Mixture additionally contains rubber crumb and secondary linear polyethylene of low density, with the following component ratio, wt %, for porous rubberised asphalt concrete mixture: 20-40 mm fraction road-metal - 16.5-23.9, bitumen BOR 60/90 - 3.0-5.0, rubber crumb - 0.4-0.8, secondary linear polyethylene of low density - 0.1-0.3, sand - the remaining part, and for highly porous rubberised asphalt concrete mixture: 20-40 mm fraction road-metal - 39-45, 5-20 mm fraction road-metal - 31-40, sand from sweepings of 0-5 mm fraction crushing - 5.6-18.2, bitumen BOR 60/90 -2.0-4.0, rubber crumb - 0.3-0.6, secondary linear polyethylene of low density - 0.1-0.2, sand - the remaining part.

EFFECT: improved physical-mechanical characteristics of asphalt concrete mixtures, which makes it possible to increase service life of road coating.

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Description

The invention relates to the field of road-building materials and can be used to arrange foundations and lower layers of coatings for roads and airfields in all climatic zones.

Recently, in most developed countries of the world there has been a tendency to increase the stability of asphalt concrete base layers and lower coating layers due to the use of polymer-bitumen binders, since it is in them that the maximum tensile (lower layer in the package of asphalt concrete layers) and shear stresses (middle layer in the package asphalt concrete layers).

The known compositions of the asphalt mixture АС 22 BS and АС 16 ВС (see TL Asphalt-StB 07 Technische Lieferbedingungen für Asphalt; ) for the device of the binder layer (lower coating layer) containing crushed stone, sand and polymer modified bitumen. However, the use of expensive polymer-modified bitumen leads to a significant increase in the cost of asphalt mixtures, limiting their use in our country.

The closest analogue of the proposed invention in technical essence and the achieved result are porous and highly porous crushed stone asphalt mixes for the lower layers of coatings and substrates according to GOST 9128 “Mixes of asphalt concrete road, airfield and asphalt concrete. Technical conditions ”(pp. 2-14), consisting of crushed stone, sand and bitumen.

The disadvantages of the known asphalt mixtures should be recognized as low values of compressive strength (at 50 ° C, 0.5-0.7 MPa is sufficient) and water resistance coefficient during prolonged water saturation (at least 0.5-0.6), which are for coarse-grained mixtures and not standardized at all, as well as crack resistance by tensile strength at split.

The technical task of the invention is the production of rubberized porous and highly porous asphalt mixtures with improved physicomechanical properties and lower cost compared to the use of polymer-modified bitumen through the use of recycled materials, as well as reducing environmental damage due to waste disposal: used automobile tires and linear low density polyethylene.

The essence of the invention lies in the fact that the rubberized asphalt mixture for substrates and lower layers of coatings, including crushed stone, sand and bitumen, further comprises rubber crumb and secondary linear low density polyethylene, in the following ratio, wt.%: For porous rubberized asphalt concrete mixes: crushed stone of a fraction of 20-40 mm - 25-31; crushed stone of fraction 5-20 mm - 25-29; sand from screenings of crushing fraction 0-5 mm - 16.5-23.9; BND 60/90 bitumen - 3.0-5.0; rubber crumb - 0.4-0.8; secondary linear low density polyethylene - 0.1-0.3; sand - the rest; for highly porous rubberized asphalt mixes: crushed stone fraction 20-40 mm - 39-45; crushed stone of fraction 5-20 mm - 31-40 mm; sand from screenings of crushing fraction 0-5 mm - 5.6-18.2; BND 60/90 bitumen - 2.0-4.0; rubber crumb - 0.3-0.6; secondary linear low density polyethylene - 0.1-0.2; sand - the rest.

The introduction of fine rubber crumb together with the polyolefin component (secondary linear low density polyethylene) contributes to the improvement of the whole range of physicomechanical properties of the asphalt mix. This effect is associated with the peculiarity of the resulting structure: the mineral skeleton is connected not by low-strength bitumen binder, but by a rubber-polymer-bitumen binder, more resistant to cracking and plastic deformation.

Characteristics of raw materials

1. Sand

For the preparation of rubberized asphalt mixtures, sand was used from screenings of crushing gravel from gravel produced by Progress LLC, fraction 0-5 mm, Republic of North Ossetia: strength grade - 1200, the content of clay particles determined by the swelling method - 0.00%; as well as natural sand produced by OJSC “Mostovskoy DSZ”, Krasnodar Territory: grade for strength - 1000, the content of silty and clay particles - 2.6%.

2. Crushed stone

For the preparation of rubberized asphalt mixtures, crushed stone of a fraction of 20–40 mm produced by LLC Progress, the Republic of North Ossetia, and also crushed stone of a fraction of 5–20 mm produced by OJSC Mostovskaya DSZ, Krasnodar Territory were used. The main properties of crushed stone are presented in tables 1 and 2.

Table 1 The main properties of crushed stone fraction 20-40 mm LLC "Progress" Breed Crushability mark Abrasion Grade Brand for frost resistance The content of grains lamellar and needle-shaped,% by weight Granite 1200 I1 F300 2.7

table 2 The main properties of crushed stone fraction 5-40 mm OJSC "Mostovskoy DSZ" Breed Crushability mark Abrasion Grade Brand for frost resistance The content of grains lamellar and needle-shaped,% by weight Gravel 1000 I1 F300 8.8

3. Road bitumen

For the preparation of rubberized asphalt mixes, BND 60/90 grade petroleum road bitumen produced by the Saratov Oil Refinery was used. The main properties of bitumen are presented in table 3.

Table 3 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, ° С Flash point, ° С Change in softening temperature after heating, ° C at + 25 ° C at 0 ° С at + 25 ° С at 0 ° С 71 22 fifty 96 3.9 -19 298 four

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 4.

Table 4 Physico-mechanical properties of secondary linear low density polyethylene (LLDPE-V) Density, kg / m ³ at 23 ° C 918-923 at 20 ° C 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 PTR21.6 / PTR2.16 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 10 variants of mixtures. Samples were prepared as follows: granules of secondary polyethylene were introduced into pre-heated to 200 ° C mineral materials (gravel of different fractions, sand from crushing screenings and natural). The mixture was stirred in a laboratory stirrer for 1 minute. Then bitumen heated to a temperature of 150 ° C and rubber crumb were fed into it, and the mixture was further mixed for 2 minutes. After that, standard cylindrical samples with a diameter of 101.0 mm were prepared from it. Compaction of the samples was carried out according to GOST 12801-98.

According to the Manual for the Construction of Asphalt Concrete Pavements to SNiP 3.06.03-85 (p. 26), the lower layers of coatings on roads of I-II category are made of porous asphalt concrete, and on roads of III-IV categories of highly porous asphalt concrete; in the upper layers of the bases, both porous and highly porous asphalt concrete can be used. In this regard, rubberized porous and highly porous asphalt mixtures were developed.

The developed porous and highly porous asphalt mixtures were prepared with various percentages of rubber crumb from 0.2% to 1.0% in 0.2% increments for porous asphalt concrete and from 0.15% to 0.75% in 0.15% increments for highly porous asphalt concrete. The content of linear linear low density polyethylene ranged from 0.01% to 0.4% in 0.1% increments for porous asphalt concrete and from 0.05% to 0.25% in 0.5% increments for highly porous asphalt concrete.

The main characteristics of the quality of asphalt concrete are the compressive strength at a temperature of 50 ° C, the crack resistance - the tensile strength at split at a temperature of 0 ° C, and the coefficients of heat resistance and long-term water resistance. The coefficient of heat resistance is very important, since it shows how the strength of the material reacts to temperature changes, and the less it is, the better.

The best performance of the proposed asphalt mixture was observed with the introduction of crumb rubber in the composition of porous asphalt in the range from 0.4 to 0.8% and secondary linear low density polyethylene in the range from 0.1 to 0.3%. For highly porous asphalt concrete, the best results were obtained with the introduction of crumb rubber in the range from 0.3 to 0.6% and secondary linear low-density polyethylene from 0.1 to 0.2%.

The investigated composition of the mixtures and the results of their tests are given for porous mixtures in table 5, for highly porous in table 6.

From the results shown in tables 5 and 6, it can be seen that the samples from the proposed composition are characterized by increased crack resistance, water resistance, heat resistance and tensile strength at 50 ° C. The data obtained indicate that the rubberized porous and highly porous asphalt mixes are characterized by increased deformation resistance, crack resistance and water resistance compared to the prototype.

Claims (1)

Rubberized asphalt mix for substrates and lower layers of coatings, including crushed stone, sand and bitumen, characterized in that it further comprises rubber crumb and secondary linear low density polyethylene in the following ratio of components for porous rubberized asphalt mix, wt.%:
Crushed stone fractions of 20-40 mm 25-31 Crushed stone fractions 5-20 mm 25-29 Sand from screenings of crushing fraction 0-5 mm 16.5-23.9 Bitumen 60/90 BND 3.0-5.0 Rubber crumb 0.4-0.8 Secondary Linear Low Density Polyethylene 0.1-0.3 Sand Rest,
and for highly porous rubberized asphalt mix, wt.%:
Crushed stone fractions of 20-40 mm 39-45 Crushed stone fractions 5-20 mm 31-40 Sand from screenings of crushing fraction 0-5 mm 5,6-18,2 Bitumen 60/90 BND 2.0-4.0 Rubber crumb 0.3-0.6 Secondary Linear Low Density Polyethylene 0.1-0.2 Sand Rest