RU2435743C1 - Rubberised vibro cast asphalt mix - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to road construction materials and can be used in building, repairing and overhauling road asphalt coatings, as well as building and repairing bridge floors and overhead crossings. The rubberised vibro cast asphalt mix contains crushed stone, sand from grinding screenings and binding substance. The rubberised vibro cast asphalt mix contains rubber crumbs with size of up 1 mm and low-density secondary linear polyethylene, and the binding substance used is asphalt cement, with the following ratio of components in wt %: crushed stone 53-70, asphalt cement 7.0-9.0, rubber crumbs 0.8-1.4, low-density secondary linear polyethylene 0.3-0.6, sand from grinding screenings - the rest. ^ EFFECT: improved physical and mechanical properties of vibro cast asphalt mix, which improves transport and operational characteristics of road surfaces and increases service life of the road surfaces, and also lowers the cost of the asphalt mix by recycling car tyres and low-density linear polyethylene. ^ 4 tbl, 1 ex

Description

The invention relates to the field of road-building materials and can be used for construction, repair and overhaul of asphalt concrete pavements, as well as for the device and repair of layers of the carriageway of bridges and overpasses.

In the construction of roads, asphalt mixtures prepared in accordance with GOST 9128-97 are widely used, however, these mixtures have a residual porosity of more than 1% and, therefore, are ineffective as a material for waterproofing layers, and also require high-quality compaction, which is possible not in all cases.

The known composition of the cast asphalt mixture for coating the roadway of the bridge, containing,%: crushed stone - 35-41, sand from crushing screenings - 10-20, natural sand - 6-16, mineral powder - 20-26 and polymer-bitumen binder - 10-16 (US Pat. RF 2341479). In this case, components are used in the polymer-bitumen binder in the following ratio, wt.%: Bitumen BND 90/130 - 87-91, styrene-butadiene-styrene block copolymer "Kraton D-1101CM" - 9-13.

In addition to using a large amount of expensive polymer, which leads to a significant rise in price of the already expensive type of asphalt concrete, the only description used in the description of the invention is “shear resistance to punch at 25 ° C”, although as in Russian TU 5718-002-04000633-2006, as in the European normative document DIN EN 13108-6, the shear resistance is determined by the depth of the indentation of the stamp at 40 ° C, and thus, the presented results do not allow to fully evaluate the properties of the invention.

A known mixture for cast asphalt, containing, wt.%: Crushed stone - 41-48, sand - 17-29, mineral powder - 18-22 and bitumen 8.9-11.0. The amount of bitumen in each specific mixture is calculated according to a certain formula (US Pat. RF 2062762).

However, the ratio of mineral components in this mixture is selected exclusively for patching or work on small areas, and the mixture is not suitable for the construction of a long roadbed. The use of BND 40/60 grade bitumen in this mixture without a polymer modifier does not provide the required crack resistance in winter and shear resistance in summer.

Known cast asphalt mixes have a relatively small amount of crushed stone, "floating" in the asphalt mortar, which does not allow them to withstand high shear forces. Unlike these mixtures, vibrocast asphalt concrete has a frame structure, in which the voids in the crushed stone frame are completely filled with sand and asphalt binder, which provides increased shear resistance of this material.

Known vibro-compacted hot asphalt mix for the construction and overhaul of road asphalt pavements (US Pat. RF 2087445), containing, wt.%: Crushed stone fraction 5-20 mm - 50-55; sand - 20-25; asphalt binder, consisting of bitumen and fine fractions of mineral powder - 21-25. The amount of bitumen in an asphalt binder is 7.24-7.50.

The specified mixture provides the desired properties of vibrated asphalt concrete (as indicated by the authors) for the second road-climatic zone, while this requires a high content of mineral powder, which significantly increases the cost of the material. For the southern regions (III and IV road-climatic zones), more stringent requirements for the heat resistance of mixtures should be imposed, which requires the introduction of polymer modifiers. The same conclusions can be drawn regarding a number of vibro-compacted asphalt mixtures that do not contain polymer modifiers (US Pat. RF 2114953 and US Pat. RF 2160337).

The closest analogue of the proposed invention in technical essence and the achieved result is a vibro-compacted hot asphalt mix (US Pat. RF 2196751), containing, wt.%:

crushed stone of the 5-20 mm fraction - 32.6-40.8;

sand - screening crushing fractions up to 5 mm - 13.0-16.0;

milled asphalt fraction up to 15 mm - 26.0-28.0;

synthetic oil solution

high molecular weight polybutadiene rubber - 0.2-0.4;

asphalt binder - 20.0-23.0.

The specified mixture, in addition to the complexity of the preparation technology in the production environment, is characterized by the use of an expensive polymer component and an increased amount of asphalt binder, which compensates for the reduction in the cost of the mixture due to the use of milled asphalt concrete. Unfortunately, the authors do not take into account the change in the particle size distribution of milled asphalt concrete after heating in an asphalt mixing plant, and due to the heterogeneity of its properties and type in industrial applications, difficulties will inevitably arise with maintaining a constant particle size distribution of the cast asphalt concrete. The data presented do not contain such an important indicator of vibrocast mixtures as water saturation and, moreover, this composition does not provide the necessary crack resistance of asphalt concrete (low tensile strength when split).

The technical task of the invention is to obtain vibrocast asphalt mixtures with improved physical and mechanical properties and lower cost due to the use of secondary raw materials (used car tires and linear low density polyethylene), the utilization of which significantly contributes to the reduction of environmental damage.

The essence of the invention lies in the fact that the rubberized vibrocast asphalt mixture includes crushed stone, sand from crushing screenings and a binder, while additionally containing rubber crumb up to 1 mm in size and secondary linear low density polyethylene, and a viscous oil road bitumen is used as a binder, in the following ratio of components, wt.%: crushed stone - 53-70; viscous oil road bitumen - 7.0-9.0; rubber crumb - 0.8-1.4; secondary linear low density polyethylene - 0.3-0.6; sand from crushing screenings - the rest.

The introduction of finely divided rubber crumbs together with secondary linear low-density polyethylene and the exclusion of mineral powder from the composition contributes to the improvement of the whole range of physicomechanical properties of vibrated asphalt mix. This effect is associated with the peculiarity of the resulting structure: the crushed stone frame is connected not with a traditional asphalt binder (mineral powder and bitumen), but with a rubber-polymer-bitumen binder (rubber crumb, secondary linear low density polyethylene and bitumen), more resistant to cracking and plastic deformation . In addition, crumb rubber also serves as a stabilizer, and the proposed rubberized vibrocast mixture is cheaper, because it uses recycled materials instead of mineral powder. 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.

Characteristics of raw materials

1. Crushed stone.

For the preparation of rubberized vibrocast asphalt mixes, crushed stone from gravel produced by OJSC Mostovskaya Crushing and Sorting Plant of the Krasnodar Territory was used. The main properties of crushed stone are presented in table 1.

Table 1 The main properties of crushed stone OJSC "Mostovskoy crushing and screening plant" 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 Gravel 1000 I1 F300 6.2 89.6

2. The sand.

For the preparation of rubberized vibrocast asphalt mixes, sand was used from screenings of crushing gravel from gravel produced by Inert LLC of the Krasnodar Territory: strength grade 1000, clay particles determined by the swelling method, 0.1%.

3. Road bitumen.

For the preparation of rubberized vibrocast asphalt mixes, BND 60/90 oil road bitumen produced by the Saratov Oil Refinery 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 73 24 49 95 3.8 -21 292 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 3.

Table 3 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 PTR _2.16 / 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: pellets of secondary polyethylene were introduced into pre-heated to 220 ° C mineral materials (crushed stone and sand from crushing screenings). 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 71.4 mm were prepared from it. Compaction of the samples was carried out by vibration in accordance with GOST 12801-98 (as for samples from hot mixtures containing more than 50% crushed stone by weight, only without subsequent compaction by pressing).

The developed vibrocast mixtures were prepared with various percentages of rubber crumb from 0.5 to 1.7 in increments of 0.3% and secondary linear low density polyethylene from 0.2 to 0.6 in increments of 0.1% with a total content of 1, 4-1.9% by weight of the mineral material.

Water saturation, tensile strength at a temperature of 20 ° C and 50 ° C, crack resistance - tensile strength at a split at a temperature of 0 ° C, and heat resistance and long-term water resistance coefficients are taken as the main quality characteristics of vibrated asphalt concrete. The coefficient of heat resistance is very important here, since it shows how the strength of the material reacts to temperature changes, and the less it is, the better.

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 and satisfy the strength properties of the requirements for dense mixtures.

The best performance of the proposed asphalt mixture was observed with the introduction of crumb rubber in the range from 0.8 to 1.4% by weight of the mineral material and secondary linear low density polyethylene in the range from 0.3 to 0.5%.

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

From the results shown in table 4, it is seen that the samples from the proposed composition at low water saturation are characterized by increased crack resistance, water resistance, heat resistance and tensile strength at 50 ° C. The data obtained indicate that the rubberized vibrocast asphalt concrete 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 rubberized vibrocast asphalt mix due to the use of secondary raw materials instead of mineral powder and expensive stabilizing additives is much cheaper than analogues.

Claims (1)

Rubberized vibrocast asphalt mix, including crushed stone, sand from crushing screenings and a binder, characterized in that it further contains crumb rubber up to 1 mm in size and secondary linear low density polyethylene, and a viscous petroleum road bitumen is used as a binder in the following ratio of components, wt.%:
Crushed stone 53-70 Viscous Oil Road Bitumen 7.0-9.0 Rubber crumb 0.8-1.4 Secondary linear low density polyethylene 0.3-0.6 Sand from crushing screenings Rest