RU2797158C1 - Asphalt concrete - Google Patents

Abstract

FIELD: road building materials.

SUBSTANCE: invention relates to hot fine-grained asphalt concrete mixtures and can be used for coating of public roads of category IV and landscaping of public areas. The asphalt concrete mix contains, wt %: crushed stone from gravel 31-35, sand from screenings of crushing 60-65, drill cuttings 4-9, bitumen (over 100% of the mineral part) 5.4-6.0.

EFFECT: increasing the physical and mechanical properties, expanding the range of materials in the road construction industry, and reducing the cost of asphalt concrete.

1 cl, 3 tbl

Description

The invention relates to road-building materials, in particular to hot fine-grained asphalt concrete mixtures, and can be used for pavement of public roads of category IV and improvement of public areas.

Known composite building material (Author's certificate RU No. 2629634, publ. 2013). The composite building material contains drill cuttings with a density of 1.3 to 1.8 kg/dm ³ , cement as the main binder in the amount of 4-12% by weight of the mixture, a desiccant and a mineral filler. Building gypsum is used as a desiccant in an amount of 2-4% by weight of the mixture, and natural sand is used as a mineral filler in an amount of 40-70% by weight of the mixture. This material has an increased strength value; also, upon receipt of the material, drilling waste - drilling cuttings - is additionally disposed of.

The disadvantage of this composite material is that its use is limited to industrial production areas, and most often, it is carried out in oil fields.

Known asphalt mixture (author's certificate SU No. 1248986, IPC SW 26/26, SW 18/12, publ. 08/07/1986), including, wt. %: bitumen 6.3-8.5; mineral powder activated with fatty acids 2.0-16.0; mineral filler (sand) - the rest; moreover, the specified asphalt mixture as an activated mineral powder contains 98.6-99.8 wt. % waste tailings flotation of the first stage of wet magnetic separation of ore with a magnetite content of 2-6 wt. % and 0.2-1.4 wt. % of activating material in the form of waste products from the production of sebacic acid. Asphalt concrete made on the basis of such a mixture has increased coefficients of crack resistance and water resistance (0.91-1.00), high compressive strength.

The disadvantage of the known asphalt mixture is the need to use an activating material for the mineral powder, which leads to an increase in the cost of the resulting mixtures.

The closest in technical essence to the proposed one is asphalt concrete (patent RU No. 2755172C1), containing crushed stone, sand from crushing screenings, mineral powder, drill cuttings, natural sand as a fine mineral material in the following ratio of ingredients, wt.%:

natural sand 11-14 rubble 45-48 Sand from crushing screenings 35-39 Drill cuttings 4-8 Bitumen (over 100% of the mineral part) 5-5.3

The disadvantage of the known asphalt concrete, taken as a prototype, is the multicomponent composition, as well as the rise in the cost of the resulting mixtures due to the use of crushed stone in its composition.

Signs of the prototype, coinciding with the essential features of the claimed invention, are: crushed stone, natural sand, drill cuttings and bitumen.

The task to be solved by the claimed invention is to expand the range of materials used in the road construction industry, to obtain a cheaper asphalt concrete mixture through the use of inexpensive inert materials, with performance characteristics and physical and mechanical properties corresponding to regulatory documents: density and strength of the material, porosity of the mineral composition.

The problem was solved due to the fact that crushed gravel was used in the known asphalt concrete containing crushed stone, sand from crushing screenings, drill cuttings and bitumen, in the following ratio of components, wt.%:

Crushed gravel 31-35 Sand from crushing screenings 60-65 Drill cuttings 4-9 Bitumen (over 100% of the mineral part) 5.4-6.0

Distinctive features of the claimed invention from the prototype are: the use of crushed stone from gravel in the composition of the mixture and other quantitative composition of its components.

The distinctive features of the proposed mixture in conjunction with the known will reduce the cost of asphalt concrete, while maintaining the compliance of asphalt concrete with the requirements of regulatory documents for performance and physical and mechanical properties.

The following inert materials are used for the preparation of asphalt concrete mix:

1. Crushed stone from gravel fraction from 5 to 20 mm in accordance with GOST 8267-93 “Crushed stone and gravel from dense rocks for construction work. Specifications".

2. Sand from crushing screenings, fraction from 0 to 5 mm in accordance with GOST 8735-2014 “Sand for construction work. Test Methods".

3. Drilling cuttings is a man-made material of oil production, in dried form it is free-flowing fine sand of dark gray color, without the formation of conglomerates during its long-term storage. Hazard class - IV. The moisture content of the original drill cuttings is 60-70%, the density of the wet drilling cuttings is 1.7-2.1 t/m ³ . The fineness modulus of the dried drill cuttings M _k = 0.057 according to GOST 8735-2014 "Sand for construction work". Test Methods".

The physical-mechanical and chemical properties of drill cuttings were studied. The average elemental composition of the studied drill cuttings samples is presented in Table 1.

Table 1

Element Content K2O, % 2.78-3.59 Al2O3, % 8.20-16.50 MgO, % 2.01-2.32 SiO2, % 53.30-78.90 Na2O, % 3.14-4.15 CaO, % 4.53-9.02 Loss on ignition, % 3.40-6.00 Oil products, mg/kg 382.4-6010.0 Oil, % 3.5-6.0

The oil content in the studied samples of drill cuttings ranged from 3.5 to 6.0%. These are mainly paraffin-naphthenic hydrocarbons - 40-46.8%, of which 16-25.5% are solid paraffins, 18-24.2% are aromatic hydrocarbons, 17-21.1% are resins, 5-5, 5% - asphaltenes.

The macrocomponents contained in drill cuttings also include inorganic water-soluble salts, the main of which are chlorides (chlorides of magnesium, calcium, ammonium, sodium) with a concentration of 0.01-0.27%. Drill cuttings contain significant amounts of kaolin and quartz. The content of kaolin in the composition of drilling cuttings is determined by its amount in the drilling fluid. The quantity and type of mineral materials in the BSHU is determined by the conditions of the passage of rocks during well drilling.

An important criterion for assessing the degree of negative impact of drill cuttings on the environment is the presence of oil, heavy metal compounds, which are the most dangerous elements of drill cuttings that can lead to a long-term change in the chemical composition of the geospheric shells of the Earth due to their high water migration hazard.

A comparative analysis of the content of heavy metals in gross and mobile forms in drill cuttings samples with established hygienic MPC standards (GN 2.1.7.2041-06, SanPiN 2.1.5.980-00) was carried out. The results of the analysis are shown in table 2.

table 2

Gross forms TM (RD 52.18.685-2006) Element Results, mg/kg MPC of soil in populated areas
, mg/kg sample 1 Sample 2 Sample 3 Sample 4 CD 0.9±0.2 0.4±0.2 0.6±0.2 0.4±0.2 2.0 Cr 22.3±0.9 19±0.9 21.6±0.9 9.9±0.9 0.05 Ni 28±0.6 9.4±0.6 17.3±0.6 19.8±0.6 80 co 10.9±0.4 2.3±0.4 2.1±0.4 6.6±0.4 - Pb 8.5±0.7 9.1±0.7 4.6±0.7 12.3±0.7 32 Cu 16±0.8 7.1±0.8 14.5±0.8 18.5±0.8 132 Mn 535±5 104±5 95±5 212±5 1500 Movable forms TM (PND F 16.1:2.3:3.50-08) Element Results, mg/kg MPC of the soil of populated areas,
mg/kg sample 1 Sample 2 Sample 3 Sample 4 CD <0.2 <0.2 <0.2 <0.2 1 Cr 0.89±0.2 1.62±0.2 1.82±0.2 0.74±0.2 6 Ni 3.6±0.6 1.0±0.2 2.6±0.1 3.0±0.6 4 co 1.8±0.4 1.6±0.4 1.4±0.4 1.2±0.4 5 Pb 2.8±0.7 2.8±0.7 3.2±0.7 3.4±0.9 6 Cu 2.30±0.6 0.42±0.13 2.02±0.5 3.32±0.8 3 Mn 207±5 27±4 23±4 51±4 500

The use of drill cuttings as part of an asphalt concrete mixture will not form a critical change in the chemical or physical composition of the geospheric shells of the Earth during the operation of an asphalt concrete pavement throughout its entire life cycle.

4. Bitumen 90/130 (over 100% MCh), in accordance with GOST 22245-90 “Road oil bitumen. Specifications". The penetration depth of the needle is 0.1 mm at 25°C - 90.

For the production of the proposed asphalt concrete mixture, it is not required to change the technology of its preparation at an asphalt concrete enterprise.

Asphalt concrete is prepared as follows.

Pre-dried drill cuttings for distribution in the composition of the asphalt concrete mixture are thoroughly mixed with mineral materials - crushed stone from gravel and sand from crushing screenings, after which the mixture is heated to a temperature of 165-175°C. After heating to the required temperature, bitumen is introduced into the mixture and the resulting mixture is stirred for 3 minutes in a forced-type mixer at a temperature of 150 °C.

The introduction of drill cuttings into the asphalt mix by pre-mixing together with the mineral materials of the original asphalt mix does not require changing the technological parameters of the preparation of the asphalt mix - preparation temperature, mixing time, etc., which is a great advantage.

According to the described method, several compositions of the asphalt concrete mixture were prepared under laboratory conditions, wt.%:

Mix 1 - gravel crushed stone - 31, crushing screenings - 65, drill cuttings - 4, bitumen 90/130 (over 100% of the mineral part) - 5.6;

Mix 2 - gravel crushed stone - 33, crushing screenings - 60, drill cuttings - 7, bitumen 90/130 (over 100% of the mineral part) - 5.6;

Mix 3 - gravel crushed stone - 31, crushing screenings - 60, drill cuttings - 9, bitumen 90/130 (over 100% of the mineral part) - 5.6.

Asphalt concrete samples were formed from the prepared mixture on a press under pressure, on which the mixture was tested for compliance with the requirements of GOST 9128-2013 “Asphalt concrete, polymer asphalt concrete, asphalt concrete, polymer asphalt concrete mixtures for highways and airfields. Specifications".

To compare the results of physical and mechanical indicators, an asphalt concrete mixture was additionally prepared according to the prototype, containing traditional mineral powder in the following ratio of components, wt.%: gravel crushed stone - 32, crushing screenings - 62, mineral powder - 6, bitumen 90/130 (over 100% of the mineral part) - 5.6. The compositions of the mixtures and the results of their tests are given in table 3:

Table 3

Test results Indicators Requirements GOST 9128-2013 (2009) Prototype mix 1 mix 2 mix 3 1. Medium density - 2.39 2.40 2.38 2.37 2. Porosity of the mineral part, % No more than 22 16.4 15.4 15.1 18.7 3. Residual porosity, % 2.5-5.0 3.2 2.8 3.2 3.8 4. Water saturation, % 1.5-4.0 2.5 2.0 2.8 3.5 5. Compressive strength:
20ºС, not less
50ºС, not less
0ºС, no more 2.0
1.1
12.0 5.84
2.47
11.0 4.38
2.90
10.8 3.76
2.31
11.1 2.56
1.34
11.2 6. Shear resistance according to: coefficient. internal friction, not less 0.75 0.92 0.90 0.82 0.80 7. Shear resistance by: shear adhesion at
temperature 50°C, not less 0.40 0.67 0.60 0.51 0.48 8. Crack resistance in terms of tensile strength at a split at a temperature of 0°C and a strain rate of 50 mm/min 2.5-7.0 5.46 5.07 5.21 5.30 9. Water resistance, not less 0.75 0.90 0.92 0.83 0.80

Based on the research results, it can be concluded that mixtures 1, 2 and 3 fully comply with the requirements of GOST 9128-2013 and are not inferior in their physical and mechanical properties to the prototype mixture. Also, the test results showed that mixture 1 has the optimal physical and mechanical properties.

The use of the proposed asphalt concrete mixture, which has the required strength characteristics, will expand the range of materials in the road construction industry, reduce the cost of asphalt concrete, and also reduce the negative environmental impact from the disposal of oil industry waste - drill cuttings.

Claims (2)

Asphalt concrete mixture containing crushed stone, sand from crushing screenings, drill cuttings and bitumen, characterized in that crushed gravel is used as part of the mixture, in the following ratio of components, wt.%: Crushed gravel 31-35 Sand from crushing screenings 60-65 Drill cuttings 4-9 Bitumen (over 100% mineral content) 5.4-6.0