RU2558049C1 - Cold method for obtaining asphalt concrete of increased strength for repair and construction of automobile roads - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: in a cold method for obtaining asphalt concrete of increased strength for repair and construction of road pavements using mineral material in the form of crushed stone, sand by their being mixed with cement and bituminous emulsion, with further application of the obtained asphalt-concrete mix onto the road base and its compaction, mixing is performed at addition to the above said cold mineral material for 100 of its wt % subsequently in 40-90 seconds of the next components, wt %: cement - 3.0-6.0, nanocomposite additive with particle size of 50-300 nm, mainly 80-160 nm, which contains the following, parts by weight: active silicic acid 0.01-3 and latex based on styrene, ester of acrylic acid, butadiene, acrylonitrile, acrylic or methacrylic acid, their mixtures 1 (in terms of a dry substance) 0.075-0.25, cationic bituminous emulsion (in terms of bitumen) 2.0-5.0.

EFFECT: saving of energy resources and improving strength of asphalt concrete.

4 tbl, 5 ex, 4 dwg

Description

The invention relates to the field of production of building materials and can be used for the cold manufacturing of asphalt concrete road, airfield mixtures and asphalt concrete used to perform repair and restoration work and the device of new pavements of increased strength.

In the future, when describing the developed technical solution, the following terms will be used:

- asphalt-concrete mixture - a rationally selected mixture of mineral materials (crushed stone, gravel, natural sand and sand screenings crushing crushed stone, mineral powder) and binders in the form of cement and other target additives, taken in certain proportions and mixed at ambient temperature;

- nanocomposite additive based on a water-borne polymer dispersion and a dispersion of active silicic acid with a specific particle size;

- cationic bitumen emulsion type EBK-3;

- asphalt concrete - compacted asphalt mixture, including the listed components.

There are various methods of preparing cold asphalt mixtures and asphalt based on them. The technology for preparing cold asphalt mixtures is given in numerous publications, inventions and patents (“Horizons of Education”, the Altai State Technical University Scientific and Educational Journal, Materials of the All-Russian Scientific and Technical Conferences “Science and Youth”, issues No. 12, 13, 14, 15 for 2010 - 2013. Subsection "Construction of roads and airfields"; Kozlova EI, Cold asphalt, M., 1958, p. 42; Auth. Certificate 975754, 1982; Pat. 2345966, 2009; Pat. 2345967, 2009; Pat. 2382802, 2010; Pat. 2362751, 2009; Pat 2447225, 2012).

For all these developments, the term or method for preparing cold asphalt is ultimately reduced to the possibility of processing it at ambient temperature. At the same time, all known methods and technologies provide for the main stage of mixing mineral fillers and molten bitumen at 120-160 ° C. In the known large-tonnage volumes of production of asphalt concrete, significant energy inputs are thus required for the production of a cold mixture. In addition, the use for liquefying bitumen up to 25 mass. % of solar or industrial oil, which further determines the necessary ductility of cold asphalt concrete mixture under storage and compaction conditions when patching the pavement, along with a sharp, more than 2 times higher cost of such asphalt concrete in comparison with hot leads to increased fire hazard of the preparation, use and to air pollution by evaporation of solar oil or other hydrocarbons from piled cold asphalt.

In addition to the above, the most important drawbacks of traditional cold asphalt concrete are its very low rates according to GOST 9128-2009 and the actual compressive strength (20 ° C) in the dry state from 1.5 to 2.0 MPa, and after prolonged water saturation, having a value of 5 to 9% by volume of absorbed water, strength decreases to 0.8-1.5 MPa. With such qualitative characteristics, high water absorption and, accordingly, low frost resistance due to the destructive effect of absorbed moisture during freezing and thawing of asphalt concrete, the coating after repair work is short-lived and requires constant, almost annual renewal. At the same time, the cost of major repairs of the road, 1 km long and 6 meters wide, of brands I or II can reach 10-11 million rubles, and the replacement of asphalt pavement makes up about 50% of the above total costs.

Asphalt mixes and asphalt mixes of the hot manufacturing method by mixing mineral fillers warmed up to 180-200 ° С and bitumen of different grades melted at 160-180 ° С, depending on its viscosity, have slightly higher strength characteristics compared to cold ones. For example, compressive strength according to GOST 9128 - 2009 at 20 ° С hot asphalt concrete has lower limits depending on type and grade from 2.0 to 2.5 MPa, and at 50 ° С these indicators fall to 0.8-1, 2 MPa, which is often one of the reasons for the formation of a rut in the summer when driving on heavy vehicles and the associated decrease in speed and traffic safety. Hot asphalt concrete is also characterized by high rates of water saturation (up to 4.0-5.0% by volume), respectively, reduced adhesion, water resistance and frost resistance, leading to the formation of macro - and microcracks with further destruction of the road surface.

These shortcomings of cold and hot asphalt concrete can be partially eliminated by the introduction of various additives modifying bitumen additives in order to increase the adhesion of bitumen to gravel, moisture resistance and frost resistance. So, for example, in US Pat. 2345967, 2009 and US Pat. 2345966, 2009 a cold mixture for repairing asphalt concrete pavements is obtained by mixing at 110-120 ° C with crushed stone of molten bitumen and solar oil (20-25% by weight of bitumen) with additives of polyethylene polyamine (5-12% by weight of bitumen), organic fatty acid (8-16% by weight of bitumen) and additives of fibrous materials (3-5%) in the form of basalt or cellulose microfiber. The proposed composition of the mixture, as the authors believe, improves the caking properties of the mixture during storage, the cohesion index and resistance to delamination. However, the other, most important characteristics - compressive strength, shear, water saturation and others are not indicated. The use of water-soluble and very toxic polyethylene polyamine in such large quantities, which can easily be washed out of the coating by rainwater and pollute the environment, is also completely unjustified.

Compositions and methods for modifying bitumen for the hot method of manufacturing asphalt concrete are also known, aimed at hardening the pavement by introducing styrene-butadiene-thermoplastic elastomer and an adhesive additive consisting of melt oil and triethanolamine in the ratio (wt.%): Bitumen 97.3-77 0; thermoplastic elastomer 2-16; adhesive additive 0.7-7.0. Similarly, it was suggested that styrene butadiene or isoprenstyrene thermoplastic elastomers in the form of block copolymers be pre-dissolved in industrial oil and then mixed with heated bitumen and then with the necessary amount of mineral fillers - crushed stone, sand and other materials (US Pat. 2038360, 1995). The proposed methods are mainly aimed at improving the conditions for the modification of bitumen and at increasing its temperature range of softening and viscosity. Any increase in strength properties, water resistance and other characteristics of the resulting asphalt concrete in these patents is not given. Such tests were carried out using Polygum as a polymer-bitumen binder, developed by Petrochem Technologies LLC (Polymer-bitumen materials TU 5775-001-63759559-11, Moscow, 2011) in experimental sections of roads. The test results of high-density grade I asphalt concrete according to GOST 9128-2009 on a polymer-bitumen binder “Polygum” or crushed stone-mastic asphalt concrete ШМА - 15, performed by the company LLC “Dorekspert”, Moscow, showed hardening at 20 ° of these road materials in about 1 , 5 times in comparison with the requirements of GOST. However, tests at 50 ° C indicate a sharp decrease in strength characteristics, more than 2 times, compared with indicators at 20 ° C. Water saturation remains at a high level and exceeds 2% by volume.

As the closest analogue of the developed technical solution, it is possible to recognize the cold preparation of base layers and highly loaded pavements by the cold recycling method (Cold Recycling. Application Guide, Wirtgen GmbH, Hoher Strobe 2,53578 Windhagen, Germany, 2nd edition, 2006). The known method offers the technology and the necessary equipment for the preparation of road mixtures based on mineral materials of natural origin (crushed stone, mineral powders, sand and others) and binders in the form of cement, lime with the addition of bitumen emulsion by cold mixing using Recycler or in conditions factory installation with further arrangement of the road base or topcoat layers with appropriate compaction instead of hot asphalt mixtures. The use of bitumen emulsion in combination with mineral cement in the proposed technology instead of hot mixes, as well as modern mobile equipment and local materials, allows us to reduce the cost of 1 km of road with a width of 9.5 m from € 244,340 with conventional hot reinforcement of asphalt up to 132385 € with the use of asphalt concrete after strengthening by the cold method. However, judging by the data presented, the replacement of hot bitumen with bitumen emulsion in equal amounts with respect to the filler (crushed stone, milled asphalt concrete or other mineral material) in combination with cement or lime does not significantly increase the adhesion and cohesion interaction in the asphalt concrete mixture after compaction and its ripening in time in comparison with a hot asphalt coating. This is primarily due to the fact that in a hot asphalt mixture, all stone material is completely enveloped in molten bitumen with an adjustable film thickness that acts as a contact adhesive. When using a bitumen emulsion having bitumen droplets from 0.001 to 0.01 mm, their coalescence and the rate of conversion to a continuous film depend on the moisture content of the compacted mixture, air humidity, the surface charge of the bitumen emulsion drops and the total surface of the mineral component, including cement particles . All these factors in the known method lead to partial enveloping of both large and small grains and insufficient adhesive and cohesive interaction in the system of the mineral part - bitumen component after uncontrolled coagulation of the emulsion under the action of cement and fillers. It should also be noted that there is a significant drawback of the considered cold version, in which only a bitumen-cement binder is used, which requires, due to the accelerated hardening of the cement in the wet state, laying and compaction of the mixture no later than 4 hours after the preparation of the mixture, i.e. there are practically same as for hot asphalt mixtures.

The technical problem solved by the developed cold method for producing asphalt concrete consists in the possibility of obtaining asphalt concrete mixture and the use of asphalt concrete at ambient temperature with increased strength properties in a wide temperature range (from 0 to 50 ° C), with increased water resistance for repair and paving while maintaining the specified characteristics of the asphalt mixture for up to 24 hours in a wet and loose state until the technological stage of the device and compaction Foot coverings.

The technical result obtained by the implementation of the developed method eliminates the cost of gas consumption for heating the mineral material that is part of the asphalt mix. The compressive strength of the resulting asphalt concrete at a temperature of 20 ° C and 50 ° C increases by 80-100% in comparison with the requirements of GOST 9128-2009. The value of water resistance in terms of long-term water saturation,% by volume, increases by 3-5 times for asphalt concrete of various types and grades. The indicated advantages remain for at least a day for loosened, wet asphalt mixtures.

To achieve the proposed technical result, a cold mixture is used to repair or arrange the upper layers of the coatings of roads and city streets, containing mineral material - gravel of various breeds and grain sizes, natural sand and gravel crushing screenings, asphalt concrete granulate, active mineral powder, cement, bitumen emulsion cationic and nanocomposite additives based on copolymer latex with polar functional groups in combination with active silicic acid in the following ratio oshenie, wt%:

- mineral material one hundred - cement, GOST R52119-2003, brand M-400 or M-500 2-6 - nanocomposite water-borne additive, in on a dry matter basis 0.05-0.25 - cationic bitumen emulsion EBK-3, GOST R 521128-2003, in terms of bitumen 2-5

As part of the nanocomposite additive, it is proposed to use an aqueous dispersion consisting of a polymer binder in the form of latex based on styrene, esters of acrylic acid, butadiene, acrylonitrile, acrylic or methacrylic acid or mixtures thereof with the addition of an aqueous dispersion of active silicic acid with particle sizes from 50 to 300 nm, mainly 80-160 nm, while the mass of active silicic acid is used in an amount to one part of the polymer from 0.01 to 3 wt.h.

The features that distinguish the proposed technical solution from the known, the following:

- are used as part of the asphalt mix and asphalt concrete based on it of the cold method for producing and using nanomodifying additives of polymer-mineral composition based on copolymer latexes containing polar monomers and functional groups in combination with aqueous dispersion of active silicic acid. At the same time, nanoparticles of the polymer phase and its composition with silicic acid in a selected average size of 50-300 nm (see Fig. 1, 2) in combination with the addition of mineral cement and additional organic cement, cationic bitumen emulsion create the necessary conditions for the maximum realization of adhesive and cohesive interactions in the system - particles of mineral filler (crushed stone, sand, granulate, screenings and others), cement, polymer-composite additives and bitumen, which also includes amine derivatives emulsate compounds ora cationic emulsion as an auxiliary adhesive additive.

- The complex effect of additives of mineral cement, nanocomposite additives of the proposed composition and additives of bitumen emulsion leads to the most effective result in achieving increased strength properties and water resistance of cold asphalt concrete while observing the following mixing order of the proposed components of the asphalt concrete mixture, namely, to a precisely measured amount of the mineral mixture, consisting, for example, depending on the type and type of mixture from a given amount of fine-grained (up to 20 mm) or coarse-grained of pure (up to 40 mm) crushed stone, screenings of crushing crushed stone, natural sand with or without mineral powder additives, accurately measured by weight of cement quantity is fed with constant stirring, then a nanocomposite additive and only after that bitumen emulsion is introduced. The mixing time after the introduction of each additive is 40-90 seconds. The total humidity, taking into account the natural moisture content of the fillers and moisture added with the nanocomposite and bitumen emulsion, is maintained at the level of 8-12 mass. %

The proposed conditions and strict adherence to the procedure for combining these components are regulated by colloidal chemical processes taking place in the proposed system. So, at the stage of combining mineral granular material with cement, only mechanical averaging of the mixture occurs without any surface phenomena. But, as soon as a polymer-containing nanocomposite additive is introduced into this mixture, a number of significant colloidal chemical processes take place with the direct participation of the surface of the granular material and compounds of calcium, magnesium, aluminum and other elements that are part of cement with a colloidal system of composite nanoparticles, the surface of which is coated with a protective a layer of a nonionic anionic emulsifier and a hydration shell that determine the particle charge, zeta potential (see Fig. 1, 2), their aggregative stability and further and in the formation of a polymer-silicate hydrophilic-hydrophobic layer on the surface of the particles of granular material and cement. With the selected nanosizes of polymer particles with ester or carboxyl groups present in the molecular chain and the selected particle size of the active silicic acid in an anionic form containing highly reactive silanol functional groups, it is possible to form strong chemical ionic and covalent bonds of the coprecipitated composite additive with cement and crushed stone surface of various rocks, gravel and sand, as well as for intramolecular interactions at the polymer - active cream interfaces non-acid is cement. The possibility of the formation of multiple effective chemical bonds is determined many times, more than 10 ³ times, by the total surface of polymer and silicic acid nanoparticles in comparison with the total surface of cement and, moreover, mineral materials accepted in road construction per unit volume of asphalt concrete mix.

Thus, in the first stage of the preparation of the mineral mixture, all particles of crushed stone, sand, powder and cement are covered with a thin film of the proposed nanocomposite mixture, which has a partially negative charge and a hydrated structural-mechanical layer of oriented water molecules to the surface of the film and silicic acid. In the loosened state, before the stage of compaction of the road mixture, cement is as if in an isolated state from water, and its setting speed is relatively low, which allows to increase the permissible time before compaction or transportation of the asphalt concrete mixture without compromising its workability and physico-mechanical properties. With further compaction of the asphalt pavement, the speed of hardening of the asphalt concrete increases sharply.

The formation on the surface of a mineral material of a thin, negatively charged composite layer in contact with a positively charged cationic bitumen emulsion determines the most uniform distribution of bitumen particles in the asphalt mix and its participation in the compensation neutralization of opposite charges between the two types of binders, with the formation of new chemical bonds between the active polymer silicic acid and functional groups of the acid or aldehyde type in the molecules of bitumen, using used in the production of cationic emulsions EBK-3 in accordance with GOST R52128 - 2003.

The use of the proposed method of nanocomposite additives, including active silicic acid with particle sizes in the range of 50-300 nm, makes it possible to achieve the greatest degree of compaction of the asphalt concrete mixture, while providing 3-5 times greater water resistance of asphalt concrete with prolonged water saturation and in addition to this, taking into account known specific properties of silicic acid, a higher slip resistance of the proposed wet asphalt concrete with car tires can be achieved, which contributes to NIJ security and speed of movement of vehicles.

The high adhesive-cohesive interaction of each of the components in the proposed composition of asphalt concrete, which is based on the formation of various chemical bonds, determines the solidity of the entire composition, which is confirmed by the destruction of individual particles of granite crushed stone without separation of the binder layer along the boundary with the crushed stone surface (see Fig. . four).

Testing of high-strength asphalt concrete obtained by the proposed cold method for pavement was carried out under exactly the same conditions by mixing a mineral mixture consisting of crushed stone of various breeds and sizes, sand, mineral powder that meet the requirements of GOST 9128 - 2009 “Road asphalt concrete mixtures, airfield and asphalt concrete ”with hydraulic cementitious cement of the same brand (cement GOST31108 - 2003) with equal optimum moisture content of the road mixture, which was 8-12 mass. % and the same load, equal to 30 MPa when pressing samples for two minutes for testing, with a height of 50 mm and a diameter of 50 mm.

The water resistance of the samples of asphalt concrete made according to the invention, according to the traditional cold method and the prototype method is presented in the form of typical kinetic curves of the limiting water saturation in time (see Fig. 3).

The size distribution of polymer particles and active silicic acid particles and their electrophoretic characteristics in polymer dispersions and in a nanocomposite additive were determined by laser spectroscopy using a modern ZETATRAC model (NPA152 - 31 A) manufactured by the US company Microtrac Ins. (see Fig. 1, 2).

For the manufacture of industrial batches of asphalt concrete mixtures according to the proposed cold method, stationary equipment of existing asphalt concrete plants of the existing preparation technology having the necessary nodes for efficient mixing of bulk and liquid materials, metering devices for their transportation to mixing, and also modern plants for the high-quality production of cold asphalt mixtures can be used leading companies in the world: Amman Wirtgen (Germany), SAF (France), Kolotikone (Finland). From the media it is known that the Finnish road companies use the most durable coatings from asphalt concrete, which uses latex-bitumen compositions. The proposed plants can be in stationary or mobile design with a capacity of 120 to 400 tons per hour. In Scandinavia, more than half of the roads were built using high-strength cold asphalt mixes (see International Specialized Journal "Construction Equipment and Technologies" No. 7 (91) November 2012, pages 52-56, article "Cold Asphalt", Silkin V.V. ., Rudakov V.V., Lupanov A.P., Silkin A.V.).

The invention is illustrated by examples of specific performance.

Example 1

For testing in a mechanical mixing device having a useful volume of the working chamber of 10 dm ³ and a screw mixer with a rotation speed of 40-60 rpm, asphalt mixtures of type B (Bx) or B (Bx) are prepared, fine-grained. The composition and grain size of the mineral components correspond to GOST 9128 - 2009.

For all these options (100 wt.%) Were introduced organic-mineral binders in the following quantities, mass. %

1. Cement 4.0 2. Nanocomposite based additive aqueous dispersion of acrylate type (styrene - 65 wt.%, butyl acrylate - 35 mass. %) in terms of dry matter mineral mixture (ratio copolymer: active silicic acid by weight 1: 1) 0.125 3. Bituminous emulsion EBK-3 3.0

The asphalt-concrete mixture is prepared in an amount of 10 kg, taking into account the ratio indicated in table 1, while mixing the crushed stone with granite screenings, sand, and mineral powder is strictly observed. After this, a weighed portion of cement is introduced, mixed for 40-60 seconds, then a weighed portion of the nanocomposite additive, mixed for 40-60 seconds, and only then the calculated amount of bitumen emulsion is added. Stirring is continued for another 5-10 minutes, bringing, if necessary, the total humidity of the loose mixture to 8-12 mass. % Samples are formed from the obtained asphalt mixtures at a pressure of 30 MPa for 2 minutes and tested according to the methods of GOST 23558-94 in comparison with the properties of asphalt concrete according to the prototype and the current GOST. The test results are shown in table 2.

The obtained values of strength properties at different temperatures and especially at 50 ° C, as well as water resistance in terms of the limiting water saturation of fine-grained asphalt concrete B and C obtained by the proposed cold method, significantly exceed the similar types of traditional hot or cold asphalt concrete.

Examples 2, 3

In example 1 for listed in table 1 the compositions of mineral materials according to paragraphs. 1-4 asphalt mixtures are prepared with the introduction of organic mineral binders in the following quantities, mass. % (see table 3).

The obtained values of the strength properties and water resistance of asphalt concrete according to examples 2 and 3 confirm their high level at different dosages of organomineral binders with a decrease in bitumen consumption from 6-8 mass. % in known hot recipes, up to 2.0 mass. % in the proposed method with providing higher physical and mechanical properties. Comparative test results are shown in table 4 and 2.

Example 4

In Example 1, an organomineral binder was introduced into a mineral mixture of composition Type 1 B using styrene-butadiene-carboxylate latex (styrene - 60.0 wt.%, Butadiene - 38.0 wt.%, Methacrylic acid - 2.0 wt.%) As a polymer dispersion. with a distribution of polymer particles in size within 60-170 nm with the following quantities, mass. % in relation to the mineral mixture 1.

1. Cement 6.0 2. Nanocomposite based additive styrene butadiene carboxylate latex, in in terms of dry matter min. mixtures (ratio 1 copolymer: active silicic acid by weight 1: 3) 0.125 3. Bitumen emulsion EBK-3, in terms of bitumen 2,5

The prepared samples of cold asphalt concrete from the mixture of example 4 have a compressive strength at 20 ° C of 4.8 MPa, at 50 ° C of 3.6 MPa, the maximum water saturation by volume,% - 0.21.

Example 5

In Example 1, an organomineral binder was introduced into the mineral mixture of composition 2 (Table 1) of type B using a copolymer butadiene-styrene-acrylonitrile carboxylate latex with a particle size in the range of 50-250 nm, mainly in the range of 80-140 nm and characterized by the most high strength properties (the strength of the copolymer at break 26 MPa), resistance to oxidative aging and water resistance of the copolymer (swelling in water) less than 0.3 mass. % The ratio of the components of the organomineral binder to 100 mass. % of the mineral mixture of composition 2 (table 1) is as follows:

1. Cement 4.0 2. Nanocomposite based additive butadiene-styrene-acrylonitrile carboxylate latex, ratio in copolymer, parts by weight butadiene - 40, styrene 32.5, acrylonitrile - 26.0, methacrylic acid - 1.5 in terms of dry substance min. mixtures (copolymer: active ratio silicic acid by weight 1: 0.01) 0,075 3. Bitumen emulsion EBK-3, in terms of bitumen 3.0

The prepared samples of cold asphalt in example 5 have a compressive strength at 20 ° C of 5.6 MPa, at 50 ° C of 4.5 MPa, the maximum water saturation by volume% is 0.14.

The achieved results with a relatively reduced consumption of nanocomposite additives are explained by the high quality characteristics of the proposed copolymer and its participation in the formation of chemical bonds and the monolithic structure of asphalt concrete.

Example 6

In example 4, prepared in a cold way, unconsolidated asphalt mixture with the specified composition and amount of organic mineral binders at a moisture content of 10.3 mass. % leave for one day in an airtight container. The samples of asphalt concrete made after this have a compressive strength of 20 ° C - 4.1 MPa, at 50 ° C - 3.2 MPa, maximum water saturation by volume,% - 0.3. The obtained characteristics differ little from the similar data for the initial asphalt concrete according to example 4, which has not undergone storage in the form of an unconsolidated mixture.

Example 7

In example 4, organic-mineral binders were introduced into a fine-grained mineral mixture of composition 1 (table 1) of type B in the changed order, namely: cement is added first with stirring - 6 mass. %, then, without stopping mixing, add a sample of cationic bitumen emulsion - 2.5 mass. % in terms of bitumen and lastly a nanocomposite additive based on styrene carboxylate latex and active silicic acid in the amount of 0.125 mass. % in terms of dry matter.

After the bitumen emulsion was introduced in the indicated order, the distribution of bitumen in the mineral mixture, as well as in pressed samples of asphalt concrete, was uneven, with separate clumps. The compressive strength of the obtained samples is not equivalent and varies at 20 ° C in the range of 1.5-2.1 MPa, at 50 ° C 0.6-1.1 MPa.

Example 8 (prototype).

In 10 kg of mineral mixture, 100 mass. %, consisting of 45% fine-grained crushed stone of granite, fraction 5-20 mm, sand from screenings of crushing granites, fraction 0-5 mm - 32 wt. %, natural sand - 18 mass. %, mineral powder, GOST R52129 - 2003 - 5.0 mass. % when mixing with a mechanical stirrer contribute cement - 4.0 mass. %, mix for 40 seconds and then at a temperature of the mixture of 20-25 ° C, while continuing to mix, add bitumen emulsion EBK-3 diluted with water to 25-30% concentration, based on 4.0 mass. % bitumen in relation to 100 mass. % mineral mixture. The dilution of the bitumen emulsion is carried out in such a way that the total humidity, taking into account the natural moisture, is 8-12 mass. % The mixture is stirred for an additional 5 minutes. After that, samples with a height of 50 mm and a diameter of 50 mm are molded in a mold for two minutes at a pressure of 30 MPa to determine the physicomechanical properties and water resistance by the maximum water saturation. Tests are carried out after a set of maximum strength by samples with air humidity of 90-100%.

The results of determining the strength properties of cold-formed asphalt concrete according to the requirements of the prototype are shown in table 2 and are equal: strength at 20 ° C - 2.4 MPa, at 50 ° C - 1.4 MPa, water saturation of 4.1% by volume (Fig. 3) . As can be seen from the above data, the strength indicators of asphalt concrete at 20 ° C, obtained according to the prototype, mainly meet the requirements of GOST 9128 - 2009 for hot mixtures of type B and C and somewhat exceed the requirements for cold asphalt concrete of type Bx and Bx. However, the obtained values are more than two times inferior to samples of cold asphalt concrete, especially at 50 ° С, made according to the invention in all variants of mixtures and with different types of polymer binders in the used nanocomposite additives.

Visual studies of the surface of cracked samples indicate that many particles of crushed granite or granite screenings remain uncoated with bitumen adhesive (see Fig. 4), and bitumen itself in this asphalt concrete mixture exists as its own fine phase, which can soften at 50 ° С and weaken the strength of asphalt concrete by more than 2 times, which is also characteristic of hot asphalt concrete obtained in accordance with the current GOST. The use of cement additives in the prototype (up to 4 wt.%) As an additional mineral hydraulic binder upon contact of cement with a cationic emulsion leads to its rapid and uncontrolled coagulation due to the dehydration of the system by cement and the transfer of the cationic bitumen emulsion from an aggregate-stable state in an acidic environment ( pH 2-3), characteristic of the emulsion, to the state of uneven, spontaneous lumpy coagulation in an alkaline (pH 9-11) medium, characteristic of cement water dispersions. In this state, bitumen particles block the surface of the cement particles with a hydrophobic layer that isolates it from water, and thus sharply limit the ability of cement to bond mineral particles in the asphalt mix.

By tests of asphalt concrete made by the proposed cold method, it was found that the production of asphalt concrete using a mineral hydraulic cement binder in combination with a nanocomposite additive based on copolymers of styrene, butadiene with polar comonomers based on acrylic acids and active silicic derivatives with a selected particle size within 50 -300 nm in combination with a cationic emulsion of bitumen allows to obtain asphalt concrete for coating and car repairs roads without heat energy for their production, corresponding and exceeding the requirements of GOST 9128-2009 and the well-known prototype in terms of strength characteristics at 20 and 50 ° C by 80-100%, and water resistance in terms of long-term water saturation by 3-5 times.

Claims (1)

The cold method of producing increased strength asphalt concrete for the repair and construction of road surfaces using mineral material in the form of crushed stone, sand by mixing them with cement and bitumen emulsion, followed by applying the resulting asphalt concrete mixture to the road base and compacting it, characterized in that the mixing is carried out upon introduction to the cold specified mineral material per 100 of its mass. % sequentially with an interval of 40-90 sec of the following components, mass. %: cement - 3.0-6.0, nanocomposite additive with a particle size of 50-300 nm, mainly 80-160 nm, containing, mass. h: active silicic acid 0.01-3 and latex based on styrene, ester of acrylic acid, butadiene, acrylonitrile, acrylic or methacrylic acid, mixtures thereof 1 (in terms of dry) 0.075-0.25, cationic bitumen emulsion (in terms of on bitumen) 2.0-5.0.

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