RU2460703C1 - Asphalt-concrete mixture - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: asphalt-concrete mix contains bitumen, crushed stone, natural or crushed sand and a mineral powder, such as cakes - wastes from production of nonferrous metals and chalky flour at the ratio from 1:2.3 to 1:1.5, with the total content of ferrum and aluminium oxides (Fe₂O₃+Al₂O₃) of not more than 7%, with the following ratio of components, wt %: oil bitumen - 5.2-5.7, crushed stone - 19.0-23.5, grinding siftings - 47.2-52.1, natural sand - 17.9-19.0, mineral powder - 4.7-5.7.

EFFECT: improved physical-mechanical properties of asphalt concrete based on new compositions of mixtures.

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Description

The invention relates to road-building materials, namely, compositions of asphalt mixes based on viscous petroleum bitumen and aggregates that can be used in the construction and repair of roads, as well as airfield coatings.

Known asphalt mixture containing sand, bitumen and mineral powder from partially crushed to a size not exceeding 1.25 mm of used asphalt concrete with a content of 1 to 20 wt.% In it (Patent No. 2354623 C1, priority date 08.28.2007, publication date 05/10/2009, authors Lupanov A.P. et al. RU).

A disadvantage of the known mixture is the limited raw material base due to the fact that it uses mineral powder from used asphalt concrete, crushed in a special electromagnetic grinder with preliminary milling of asphalt concrete with a road mill and subsequent crushing and separation of asphalt concrete chips into fractions using crushing and screening installation, which also indicates the high energy intensity of the process of preparing mineral powder.

Also known asphalt mixture reinforced with wood fibers and containing crushed stone, sand, bitumen, active mineral powder in the following ratio of components, wt.%: Wood fibers 0.3-0.7; bitumen grade BND 60/90 5.7-6.9; crushed stone, fractions of 5-15 mm 37.76-45.29; screening of a large fraction of crushed stone with a particle size of 0.071-5 mm 49.0-37.14; active mineral powder, fraction with particle sizes of 0.071-0.315 mm 6.64-9.97 (Patent No. 2262491 C2, priority date 03.02.2003, publication date 10.08.2004, authors Telyufanova O.P. et al. RU).

A disadvantage of the known mixture is the low water resistance of asphalt concrete, limiting the service life of the pavement using this asphalt concrete mixture, which is associated with the presence of wood fibers in its composition.

As a prototype adopted asphalt mixture containing crushed stone, sand, mineral powder and bitumen, rationally selected in accordance with the requirements of the standard (GOST 9128-97 "Mixes asphalt road, airfield and asphalt concrete." - M .: MNTKS, 1998, prototype).

The disadvantage of the prototype should be recognized as a low tensile strength and low water resistance of asphalt concrete based on mixtures regulated by the standard.

The problem solved by the proposed compositions of asphalt concrete mixtures is to expand the raw material base by using industrial industrial wastes to produce asphalt concrete with improved physical and mechanical properties based on new mixtures.

The technical result obtained by the implementation of asphalt mixtures of the proposed compositions is to increase the tensile strength and water resistance of asphalt concrete.

To achieve the technical result provided by the invention, an asphalt concrete mixture containing bitumen, crushed stone, natural and crushed sand and mineral powder, according to the invention, contains cakes - non-ferrous metal production waste and limestone flour in the ratio of 1: 2.3 to 1 as a mineral powder: 1.5, with a total content of iron and aluminum oxides (Fe ₂ O ₃ + Al ₂ O ₃ ) not more than 7%, with the following ratio of components, wt.%: Petroleum bitumen 5.2-5.7; crushed stone 19.0-23.5; screening crushing 47.2-52.1; natural sand 17.9-19.0; mineral powder (cakes + limestone flour) 4.7-5.7.

To implement the invention, the selection and preparation of components for their mixing in accordance with the requirements of the standards is carried out:

- GOST 9128-97 "Mixtures of asphalt road, airfield and asphalt concrete." - M .: MNTKS, 1998;

- GOST R 52129-2003 “Mineral powder for asphalt concrete and organomineral mixtures”. - M .: MNTKS, 2003;

- GOST 12801-98 "Materials based on organic binders for road and airfield construction." - M .: MNTKS, 1998.

The use as a mineral powder of a mixture of cakes, which are waste in the production of non-ferrous metals, and limestone flour is permissible by GOSTs and is justified by the following factors.

The cake powder is obtained by fine grinding in mills a dried pasty mass formed in the form of waste in the production of non-ferrous metals. According to the classification of GOST R 52129-2003, it can be attributed to powders of the MP-2 brand - powders from non-carbonate rocks, solid and powdery industrial waste. The chemical composition of cakes, for example, of the Krasnoyarsk non-ferrous metals plant, is given in Table 1.

Table 1 The chemical composition of the cakes Chemical composition, wt.% SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ Cao MgO SO ₃ N ₂ O Cl 0.4-3.5 0.2-1.5 11.5-21.5 20.0-35.0 1.0-3.5 4,5-7,5 1.0-2.3 0.02-10.0

From table 1 it is seen that the cakes have a complex mineralogical composition, but the properties of asphalt concrete are mainly affected by iron and aluminum oxides and free calcium oxide. In accordance with the requirements of GOST R 52129-2003, the requirements for the mineral powder for asphalt concrete are the total content of aluminum oxide Al ₂ O ₃ and iron oxide Fe ₂ O ₃ , which should be no more than 7% for activated mineral powders and 1.7 for non-activated powders %, and the content of free active lime (CaO) should be no more than 3%. According to table 1, the chemical composition of the cakes does not meet the requirements of GOST R 52129-2003 for the content of iron oxide Fe ₂ O ₃ and aluminum oxide Al ₂ O ₃ , and the cakes do not contain free CaO. The grain composition of the cakes is compared with the requirements of GOST R 52129- 2003 for powders grade MP-2 are given in table.2.

table 2 Grain composition of cakes Size of sieves, mm Private balances, g Private balances,% Total residues,% Passed through a sieve,% GOST requirements for MP-2 1.25 0 0 0 one hundred Not less than 95 0.63 0 0 0 one hundred 0.315 3.44 6.88 6.88 93.12 80 to 95 0.16 7.68 15.36 22.24 77.76 0,071 8.04 16.08 38.32 61.68 Not less than 60 Bottom 30.84 61.68 one hundred 0 Amount 50.00 100.00

As can be seen from table 2 on the grain composition of the cakes meet the requirements of GOST R 52129-2003.

The physicomechanical properties of cakes in comparison with the requirements of GOST R 52129-2003 for MP-2 powders are given in Table 3.

Table 3 Physico-mechanical properties of cakes The name of indicators The properties GOST requirements for MP-2 True density, g / cm ³ 2.42 - The average density, g / cm 1.19 - Porosity,% 50.8 No more than 40 Swelling of a mixture of powder with bitumen,% 2,8 No more than 3.0 Water resistance of samples from a mixture of powder with bitumen 0.65 Not less than 0.7 Bitumen rate, g 107.6 No more than 80 Humidity,% by weight 0.61 No more than 2.5 The content of water-soluble compounds,% 8.37 No more than 6

As can be seen from the table, cakes for porosity, water resistance, bitumen content and the content of water-soluble compounds do not meet the requirements of GOST. However, the possibility and necessity of their use in asphalt concrete is related to the fact that the cakes have a fine grain composition that meets the requirements of GOST, are waste products of non-ferrous metallurgy that require disposal, which is associated with high costs, and, finally, the cost of cakes is much less than the cost of standard carbonate mineral powders. The use of cakes in the production of the proposed asphalt mix will expand the raw material base and utilize cakes, reduce the cost of producing mineral powder, which is a scarce component of asphalt concrete.

To adjust the chemical composition and physico-mechanical properties of the cakes, it is proposed to dilute them with limestone flour produced by the Krasnoyarsk Chemical and Metallurgical Plant according to TU 574-004-00196533-2009.

The amount of limestone flour and cake can be calculated by the formula:

, где

where

m _ref. - total percentage of oxide in the initial cakes (Fe ₂ O ₃ + Al ₂ O ₃ );

m _end - the final percentage of oxides (Fe ₂ O ₃ + Al ₂ O ₃ ) in a mixture of cakes with limestone flour;

m _{Izv. flour} - weight (kg, g) of limestone flour, which must be added to the cakes to obtain the required oxide content (Fe ₂ O ₃ + Al ₂ O ₃ );

m _cakes - mass (kg, g) of the original cakes.

Limestone flour according to the classification of GOST R 52129-2003 refers to the MP-1 brand - powders, inactive and activated from sedimentary (carbonate) rocks. Table 4 shows the grain composition of limestone flour in comparison with the requirements of GOST R 52129-2003 for powders of grade MP-1.

Table 4 Grain composition of limestone flour Size of sieves, mm Private balances, g Private balances,% Total residues,% Passed through a sieve,% GOST requirements for MP-1 1.25 0 0 0 one hundred Not less than 100 0.63 0 0 0 one hundred 0.315 0.01 0.01 0.01 99,99 Not less than 90 0.16 5.81 5.81 5.82 94.18 0,071 14.78 14.78 20.60 79.40 70 to 80 Bottom 79.40 79.40 100.00 0 Amount one hundred one hundred

As can be seen from table 4, the limestone flour according to the grain composition meets the requirements of GOST R 52129-2003. Physico-mechanical properties of limestone flour in comparison with the requirements of GOST for powders of grade MP-1 are given in table 5.

Table 5 Physico-mechanical properties of limestone flour Name of indicator Value GOST requirements for MP-1 Porosity,% 33.21 No more than 35 Swelling of samples from a mixture of powder with bitumen,% 0.92 No more than 2.5 Humidity,% by weight 0.24 No more than 1,0 True density, g / cm ³ 2.65 - The average density, g / cm ³ 1.77 - Bit capacity, g 65 -

As can be seen from table 5, for all physical and mechanical properties, limestone powder meets the requirements of GOST R 52129-2003.

In the examples, a mineral powder was used, consisting of cake and limestone flour, two compositions (wt.%):

composition No. 1 composition No. 2 cake thirty 40 limestone flour 70 60

The compositions of the mineral powder are calculated on the basis of data on the chemical analysis of cakes taking into account the total content of iron and aluminum oxide (Fe ₂ O ₃ + Al ₂ O ₃ ) in them according to the formula (1).

The advantages of the proposed asphalt mixes using cakes and limestone powder as a mineral powder are shown on the compositions of fine-grained mixtures, which in terms of particle size distribution satisfy the requirements of GOST 9128-97 for type II “B” mixtures.

Four obtained compositions of the asphalt concrete mixture were prepared on the obtained mineral powder (Table 6). Asphalt mix was prepared at the Krasnoyarsk asphalt plant DSU-2 (road construction department) Krasavtodorstroy.

Table 6 Asphalt mixes Components The content of the compositions, wt.% one 2 3 four Bitumen 5.2 5.7 5.2 5.7 Crushed stone 19.0 23.5 19.0 23.5 Screening crushing 52.1 47.2 52.1 47.2 Natural sand 19.0 17.9 19.0 17.9 Mineral powder composition No. 1 4.7 5.7 Mineral powder composition No. 2 4.7 5.7

The prepared asphalt concrete mix was laid on the territory of the same asphalt concrete plant and tested in the laboratory DSU-2. The quality of asphalt concrete was determined according to GOST methods (GOST 12801-98 “Materials based on organic binders for road and airfield construction”, MNTKS, Moscow, 1998) and was compared with the properties of asphalt concrete according to GOST 9128-97 for the 3rd road-climatic zone.

The properties of these compositions are given in table.7.

Table 7 Properties of asphalt mixtures Indicators Suggested formulations GOST 9128-97 one 2 3 four The average density of asphalt concrete, g / cm ³ Not normal. 2.59 2.59 2,37 2,38 Strength under compression, MPa, at: 20 ° C 4.44 4.77 2.67 2.74 Not less than 2.2 50 ° C 1.74 1.10 1.16 1.13 Not less than 1.0 0 ° C 8.52 8.37 5.09 4.90 No more than 12 Water resistance coefficient 1,03 0.98 1,07 1.12 Not less than 0.85 Water resistance coefficient with prolonged 0.83 0.78 0.89 0.88 Not less than 0.75 water saturation Water saturation,% volume 2.83 2.28 2.47 2.21 1.5-4.0

As can be seen from table 7, according to the tensile strength at 20, 50, 0 ° C and water resistance, the proposed compositions of asphalt concrete have better performance than the known compositions (prototype).

Claims (1)

Asphalt concrete mixture containing bitumen, crushed stone, natural and crushed sand and mineral powder, characterized in that it contains cake - non-ferrous metal waste and limestone flour in the ratio of 1: 2.3 to 1: 1.5 as a mineral powder, with a total the content of iron and aluminum oxides (Fe ₂ O ₃ + Al ₂ O ₃ ) not more than 7% in the following ratio of components, wt.%:
oil bitumen 5.2-5.7 crushed stone 19.0-23.5 screening crushing 47.2-52.1 natural sand 17.9-19.0 mineral powder (cake + limestone flour) 4.7-5.7