RU2351561C2 - Method for reinforcement of asphalt concrete mix - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention is related to the field of road construction materials. Method for reinforcement of asphalt concrete mix by means of asbestos fibers introduction in its composition, consists in the fact that asbestos fibers are introduced in asphalt concrete mix, previously mixing it with mineral powder at mass ratio of asbestos fibers/mineral powder equal to 0.024-0.363, with further addition of chrysotile-asbestos fractions to prepared mixture with particle size of 0-5 mm, crushed stone (fractions of chrysotile-asbestos) with chip size of 5-20 mm, bitumen and additive Amdor-9 (mixture of polyaminoamids and polyaminoimidosolins) at the following ratio of components, wt %: asbestos fibers of class 0.075-0.5 mm - 0.135-2.64, fractions of chrysotile-asbestos with the following size, mm: 0-5 - 34.88-39.12, size of 5-20 - 53.26-44.59, mineral powder - 5.63-7.28, bitumen BND 90/130 6.064-6.338, additive "Amdor-9" - 0.031-0.032.

EFFECT: lowering expenses for production of asphalt concrete mixes and emission of pollutants in environment.

4 tbl, 2 ex, 1 dwg

Description

The invention relates to the field of reinforcing asphalt concrete pavements and can be used for the construction of roads, airfields, etc.

A known method of reinforcing asphalt mixtures with steel fiber fibers [1].

This method is characterized by increased crack resistance, however, the strength of the mixture is lower compared to unreinforced. In addition, during the construction of roads by the known method, difficulties arise with compaction of the asphalt mix, requiring high costs. The method is metal-intensive and costly.

A method for reinforcing an asphalt concrete mixture with organic polymer fibers is described [2-3]. Reinforcing elements are obtained by cutting finished organic polymer fibers into segments up to 20 mm long, which leads to an increase in the cost of production of asphalt concrete mix. A dispersion-reinforced mixture is prepared by introducing segments: organic polymer by drag into hot mineral materials directly in the mixer of the installation.

In the asphalt-concrete mixture, the fibers form strong clusters that perceive and distribute stresses from the action of dynamic loads on a limited volume of the coating layer, since the fibers bind mineral formations only in adjacent formations adjacent to them. Therefore, the introduction of very short fibers does not increase the strength of the asphalt mixture, which leads to a decrease in shear resistance, crack resistance of the road surface, etc.

A known method of reinforcing an asphalt mixture [2] by introducing organic polymer fibers into it during mixing, the fibers being introduced into the asphalt mixture hot immediately after they are molten from the melt.

The disadvantage of this method is associated with the need to heat the fibers to a hot state (melt), which increases the energy consumption for the preparation of the asphalt mix. In addition, heating of organic fibers leads to the evaporation of harmful substances into the environment.

A method for reinforcing asphalt mixtures [4] is proposed, which consists in introducing into its composition wood fibers obtained from wood chips by drying it in an upward flow of air and subsequent drying in a mill. Moreover, when preparing the asphalt mixture, the mixer is first served with mineral powder, bitumen and a surfactant, and then in the mixing process - wood fibers, gravel and sand.

The disadvantage of this method is associated with insufficient durability and the possibility of decomposition (decay) of wood fibers, which leads to accelerated aging of bitumen and asphalt concrete.

A method of obtaining an asphalt concrete mixture with improved rates of swelling, degree of delamination, water resistance and tensile strength at split, frost resistance, etc. was developed in [5]. In this case, the asphalt mixture includes, wt.%: Bitumen 5.2-7, sand from crushing screenings 27-38, chrysotile asbestos fraction of 2.8-5 mm of the 4th group of grade A-4-30-04-1 and rubble - the rest. Moreover, bitumen and chrysotile asbestos are used with a mass ratio of (7-13) / 1.

The disadvantage of this method is that in the asphalt concrete mixture, asbestos fibers are not in a free state, but in the composition of the rock - fractions of chrysotile asbestos, which significantly reduces their reinforcing effect.

A method has been developed for reinforcing road asphalt concrete using chrysotile asbestos [6], which we adopted as a prototype.

According to this method, when up to 5% of asbestos fiber is introduced, the strength characteristics of asphalt concrete increase, the deformation modulus, water and frost resistance increase, the adhesion coefficient of the road surface increases, and its service life is extended.

However, with the introduction of asbestos, the consumption of bitumen increases from 7 to 11 wt.%. In addition, asbestos is toxic and pollutes the environment, therefore, its use for the device of the upper layers of pavement is prohibited [7].

The objective of the invention is to reduce the cost of production of asphalt concrete and toxic emissions into the environment.

This is achieved due to the fact that in the method of reinforcing the asphalt mixture by introducing asbestos fibers into its composition, asbestos fibers are introduced into the asphalt mixture, pre-mixed with mineral powder: (MP) at a mass ratio of asbestos fibers / MP equal to 0.024-0.363, followed by adding to the mixture obtained fractions of chrysotile asbestos with a particle size of 0-5 mm, crushed stone (fractions of chrysotile asbestos) with a size of gravels of 5-20 mm, bitumen and Amdor-9 additive (a mixture of polyaminoamides and polyaminoimidosolines) in the following enii, wt.%:

Asbestos fiber 0.135-2.64 Chrysotile Asbestos Fractions fineness, mm; 0-5 34.88-39.12 5-20 53.26-44.59 Mineral powder 5.63-7.28 Bitumen BND 90/130 6.064-6.338 Additive "Amdor-9" (mixture of polyaminoamides and polyaminoimidosolines) 0,031-0,032

As an additive to the mixture, mineral powder (MP) was used, prepared from the waste products of the enterprise Uralasbest OJSC. The grain composition and physicomechanical properties of this MP are given in Table 1-2. From the data of Table 1 it follows that according to the grain composition MP corresponds to the requirements of GOST 16557-78 and GOST 9128-78. MP consists of serpentinite, epidositol, magnetite, talc, olivine, carbonates, etc.

The amount of MP introduced into the asphalt mixture is 5.63-7.28 wt.%. A decrease in the content of MP in the composition of asphalt concrete below 5.63% decreases its strength, and an increase in the proportion of MP in the asphalt mix above 7.28% does not change its physical and mechanical properties.

Upon receipt of the asphalt-concrete mixture, asbestos fibers of the Uralasbest OJSC enterprise, class 0.075-0.5 mm, which have no technological value, are used. The amount of asbestos fibers introduced into asphalt concrete is 0.135-2.64 wt.%. The chemical composition of the fibers is as follows - 3 MgO * 2H ₂ O 2SiO ₂ .

Table 1
Grain composition of non-activated mineral powder prepared from asbestos of OJSC “Uralasbest” The size of the holes, mm 1.25 0.63 0.315 0.14 0,071 less than 0,071 total Private residues, wt%. _ 0.02 0.35 2.14 15.06 82,43 one hundred Total residues, wt.% - 0.02 0.37 2,51 17.57 one hundred Full passages, wt.% one hundred 99.98 99.63 97.49 82,43

table 2 Physico-mechanical properties of non-activated mineral powder prepared from asbestos of OJSC “Uralasbest” №№ results Indicators pp test one Porosity,% by volume 25.98 2 Density (bulk density), kg / m ³ 1880 3 True density, kg / m ³ 2540 four The bitumen rate, g: when the content of gly- powder impurities in the powder of not more than 5%, one and a half oxides of Al ₂ O ₃ + Fe ₂ O ₃ , not more than 1.7% by weight 77.9 5 Water resistance of samples from a mixture of powder with bitumen 0.8 6 Humidity,% by weight 0.1

Asbestos fibers are introduced into asphalt mixed with MP at a mass ratio of asbestos fibers / MP equal to 0.024-0.363. This is due to the fact that asbestos fibers interact with MP with the formation of molecular compounds, which lead to a significant increase in their activity in the system and an improvement in the physico-mechanical properties of asphalt concrete (strength, water resistance, crack resistance, etc.). An increase in the ratio of asbestos fiber / MP more than 0.363 and a decrease in this ratio less than 0.024 affects the performance of asphalt mixtures.

Chrysotile asbestos fractions with a grain size of 0-5 mm (sand) according to GOST 8735-88 and 5-20 mm according to GOST 8267-97 of an enterprise of OJSC Uralasbest with a content in the mixture, wt.%: 34.88-39, are used for the preparation of the asphalt-concrete mixture. 12 and 53.25-44.59, respectively. The indicated ranges of chrysotile asbestos (sand) and crushed stone fractions provide stable asphalt concrete mixtures, the use of asbestos fibers in a system with MP and chrysotile asbestos fractions increases the strength of the asphalt concrete mixture, since a larger number of reinforcing compounds per unit volume of the mixture are included in the spatial structure.

Amdor-9 additive used for the preparation of asphalt concrete is a mixture of polyaminoamides and polyaminoimidosolines according to TU 0257-003-35475596-96. The amount of the specified additive in the composition of the mixture (asphalt concrete) is 0.031-0.032.

The drawing shows the installation diagram, allowing to implement the proposed method.

The installation consists of two production lines. In one line, chrysotile asbestos fractions are obtained, and in the other, asphalt mixture.

A plant for producing chrysotile asbestos fractions includes: (see drawing) - asbestos waste warehouse 1, belt conveyor 2, drying drum 3, elevator 4, screen 5 and silos for dispersed chrysotile asbestos fractions: 0-5 mm 6 and 5-20 mm 7.

For the preparation of sand-gravel fractions with a particle size of 0-5 and 5-20 mm, the waste from the asbestos-processing factory in Asbest in accordance with GOST 9128-97, which are transported to the installation by road, is used as feedstock. After unloading the vehicle, the waste as a bulldozer is loaded into a receiving hopper 1, from which it is fed to a drying drum 3 using a conveyor 2. After drying in the drum 3, the waste as an elevator 4 is fed to a screen 5, where it is dispersed into fractions with a particle size of 5-20 mm (crushed stone) and 0-5 mm (sand) entering the silos 7 and 6 and further into the silos 11 and 8 of the asphalt concrete plant.

For the production of asbestos fiber and MP, screening and crushing of chrysotile asbestos fractions of class 6-4 and 4-2 mm are carried out, followed by separation of the crushed mixture.

The production line for the production of asphalt mix consists of bins 8-13 (see drawing) for feedstock, batchers 14, prefabricated tank 15 and mixer 16 and includes the following operations.

Asbestos and MP fibers are first fed into the mixer 16 from the bins 9 and 12 through the batchers 14 through a cold elevator, which are mixed. Then, chrysotile asbestos fractions with a particle size of 0-5 mm (sand), crushed stone (chrysotile asbestos fraction) with gravel size of 5-20 mm, BND bitumen 90 are fed sequentially to the same mixer 16 from bins 8, 11, 13 and 10. / 130 and additive Amdor-9.

With further mixing of all components, the formation of a reinforced asphalt mixture occurs.

The technology for producing asphalt concrete is illustrated by examples.

Example 1. Prepare a hot fine-grained asphalt mixture of type B using the following materials, wt.%: Crushed stone (chrysotile asbestos fraction) with a particle size of 5-20 mm 53.26, sand (chrysotile asbestos fraction) with a particle size of 0-5 mm 34 , 88, asbestos fibers of the class 0.075-0.5 mm 0.135, mineral powder (MP) 5.63, bitumen BND 90/130 6.064, additive Amdor-9 0.031.

MP is first mixed with asbestos fibers, then with constant stirring, a mixture of fibers and MP is successively added: sand (chrysotile asbestos fraction) with a particle size of 0-5 mm and crushed stone (chrysotile asbestos fraction) with crushed stone sizes of 5-20 mm. The resulting mixture is heated to 150 ° C, then a mixture of bitumen grade BND 90/130 and additive Amdor-9, heated to 140 ° C, is added to the heated fiber-mineral mass. The temperature of the finished mixture is 140 ° C. The formation of samples of asphalt concrete is carried out in accordance with GOST 12801 - 98. The composition and physicomechanical properties of the resulting hot fine-grained asphalt mixture of type B are given in tables 3-4. As can be seen from table 4, the resulting asphalt concrete mixture No. 1 in terms of physical and mechanical properties: compressive strength at 0 ° C 11.2 MPa, water resistance 0.93, water resistance with long-term water saturation of 0.72, etc., meets the requirements of GOST 9128 -97 (type B) on the II-III brand.

Example 2. Prepare a hot fine-grained asphalt mixture of type B with the following mass ratio of components, wt.%: Crushed stone with a particle size of 5-20 mm 49.52, sand with a particle size of 0-5 mm 37.84, asbestos fibers 0.5, MP 6 , 04, bitumen BND 90/130 6.04, additive Amdor-9 0.03, according to the procedure described in example 1. Get asphalt mixture No. 2 (see table 4) with physico-mechanical parameters that meet the requirements of GOST 9128- 97 for type B asphalt concrete grade II.

The results of determining the physicomechanical parameters of asphalt concrete obtained from a hot dense fine-grained mixture of type B with different component ratios are given in table 4. As can be seen from the table, the physicomechanical properties of the obtained asphalt concrete: water saturation, compressive strength at different temperatures, shear resistance, fracture toughness, adhesion of bitumen to the mineral part, porosity, etc. when the content of asbestos fibers in the mixture is 0.135-2.64% and bitumen consumption 6.064-6.338 wt.%, meet the requirements GOST 9128-97 on asphalt type B I-III mark.

The proposed method, in comparison with the prototype [6], allows to reduce the cost of production of asphalt concrete mixtures, since with a reduced consumption of asbestos fiber (according to the proposed method) - 0.135-2.64 wt.%, The consumption of bitumen decreases from 7-II% to 6.064 -6.338 wt.%.

Reducing the consumption of asbestos fiber for the preparation of asphalt mixtures makes it possible to exclude their clumping on the anchors of the mixers in the mixers.

In addition, the environmental status of the production of asphalt mixtures is improving, since the consumption of asbestos fiber is reduced from 5 wt.%, (According to the prototype [6]) to 0.135 wt.% (According to the proposed method).

Table 3 Compositions of asphalt concrete mixtures (I-V) type B, wt.%, Used to obtain asphalt concrete Mixture Components The compositions of mixtures I-V, wt.%. I II III IV V 1. Asbestos 0.135 0.5 0.92 1.82 2.64 fiber 2. Sand class 34.88 37.84 39 38.32 39.12 0-5 mm 3. Crushed stone class 5-20 mm 53.26 49.52 48,2 46.3 44.59 4. Mineral 5.63 6.04 5.63 7.2 7.28 powder 5. Bitumen BND 6,064 6.07 6.22 6.33 6,338 90/130 6. Additive Amdor-9 0,031 0,03 0,03 0,03 0,032

Literature

1. Talantova K., Tolstenev S. Composite - steel fiber concrete in road construction. Auto roads. 1999. No. 9. S.24-26.

2. A.S. RU 2102353 C1 dated 01.15.1996. Lukashevich V.N. and others. A method of reinforcing an asphalt mixture.

3. Reinforcement of asphalt concrete pavements during the construction and reconstruction of pavement. Overview information TsSTI Minavtodor RSFSR. M .: 1990. Issue 5. Car roads. S.24-26.

4. RF patent No. 2262491.

5. RF patent No. 2229451.

6. Enrobes specianoc a as ages di vers 1 -ere hartit. Lassalle 1., Remillion A., Secard D. Rev. gen. Routes et asrod. 1981.55. Suppl. 1-12 (franc.): Waterproof asphalt with asbestos. Asbestos-asphalt waterproofs freeway decks Highway and Heavy constr.

1976. 119. No. 10.128-128 (English). EI "construction and ex p.avt.dorog.

1977. No. 11. S.10-11.

7. Prohibition of the use of stone materials with the inclusion of asbestos for the construction of pavements. 1977. T. 92. No. 8. S.26 (English).

Claims (1)

A method of reinforcing an asphalt-concrete mixture by introducing asbestos fibers into its composition, characterized in that the asbestos fibers are introduced into the asphalt-concrete mixture pre-mixed with mineral powder at a mass ratio of asbestos fibers / mineral powder equal to 0.024-0.363, followed by the addition of chrysotile- fractions to the resulting mixture. asbestos with a particle size of 0-5 mm, crushed stone (chrysotile asbestos fractions) with a crushed stone size of 5-20 mm, bitumen and Amdor-9 additives (a mixture of polyaminoamides and polyaminoimidosolines) in the following ratio NII, wt.%:
Asbestos fiber class 0.075-0.5 mm 0.135-2.64 Fractions of chrysotile asbestos fineness, mm: 0-5 34.88-39.12 5-20 53.26-44.59 Mineral powder 5.63-7.28 Bitumen BND 90/130 6.064-6.338 Additive Amdor-9 0,031-0,032