RU2769049C1 - Use of petroleum coke as a bitumen modifier - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to the field of construction. The use of petroleum coke powder with a particle size of 0.055-0.075 mm as a bitumen modifier in an amount of 5-15% of the total mass of petroleum coke powder and bitumen in the composition of an asphalt concrete mixture is described.

EFFECT: use of an alternative modified bitumen-based binder with improved properties, inexpensive and effective for use.

5 cl, 2 tbl, 3 ex

Description

The invention relates to the field of construction, in particular road construction, and is used to create new modified binders based on bitumen with improved properties for the manufacture of asphalt mixtures.

A common method for improving the properties of an asphalt mix is to add various types of additives.

Additives whose ultimate function is to improve the quality of the roadway include the following types of materials:

1. bitumen modifiers;

2. adhesive additives to bitumen;

3. Stabilizers SCHMAS (crushed stone-mastic asphalt mix);

4. asphalt concrete mix modifiers;

5. Structuring additives in asphalt mix.

At low temperatures bitumen becomes hard and brittle, at high temperatures it becomes soft and fluid. Bitumen is modified with various elastomers, the use of which is intended to improve the performance of bitumen at extreme temperatures. When bitumen is modified with styrene butadiene styrene, the polymer bitumen mixture becomes soft and more flexible at low temperature, and more viscous at high temperature.

The use of various bitumen additives is aimed at improving a particular property of bitumen: adhesion with the mineral component of the asphalt concrete mixture or plastic fluidity at low temperatures. There is an additive that prevents bitumen oxidation and, as a result, the formation of microcracks on the surface.

Additives that improve the adhesion (adhesion) of bitumen are introduced directly into the bitumen and into the mineral mixture. When grinding, a complex electric field is formed on their surface, the sign and magnitude of the potential of which are determined by the properties of the ions and the nature of their location on the surface. Most of the basic carbonate rocks (limestones, dolomites) have a positive charge, while acidic rocks (granite, quartz) have a negative charge. The complex composition of bitumen is dominated by anionic substances. From the point of view of the electrostatic theory of adhesion, we need to study the adhesion of bitumen to ground coke powder, which is explained by the opposite charges of the surface of the material and bitumen components.

Thus, the introduction of additives into bitumen containing polar groups and increasing the mobility of links of high-molecular compounds will increase its adhesion to coke.

Due to the insufficient quality of petroleum bitumen suitable for road construction, as well as to improve their properties, various additives have recently been proposed. Additives introduced in a relatively large amount, which significantly affect the structure and properties of the resulting binders, are called composite, or complex. The most common complex binders are bitumen-tar, bitumen-polymer, tar-bitumen-polymer.

To improve the properties of organic binders (bitumen and chains), increase their adhesion to materials (adhesion), plasticity at low temperatures, heat and weather resistance, and reduce viscosity, appropriate additives are introduced into their composition in an amount of up to 20%.

As is known, the most intensive aging of bitumen occurs in the process of preparing an asphalt concrete mixture. In this case, a thin film of bitumen is exposed to the simultaneous effects of high temperatures and oxygen. As a result of oxidation, bitumen quickly loses its plasticity. Further, over time, the plasticity of bitumen continues to decline, but this process is much slower, because. it occurs at ambient temperatures. Reducing the degree of bitumen oxidation for Russian conditions is especially important, because. the quality of initial bitumen in Russia is unsatisfactory and there are no hopes for its improvement in the future.

Currently, there are many developments in the field of creating effective bitumen modifiers, including those protected by patents of the Russian Federation.

From patent RU 2355655 with a publication date of 05/20/2009, a binder for the preparation of hot and cold asphalt concrete mixtures includes petroleum bitumen and a thinner. As a thinner, oil-containing fluids are used - natural surface oil shows, which are a waste from the production of underground mines during diamond mining, including 10-12 wt.% of mineralized water containing 39.4 g / l of mineral salts, mainly potassium and calcium chlorides, in the following ratio of components binder, wt.%: oil bitumen 50-95, these oil-containing fluids 5-50. The binder is prepared by conventional mixing in a paddle mixer bitumen with t=90-100°C with oily fluids with t=20°C for 3 minutes. fluids will solve the problem of ecological safety of the region.

From patent RU 2484109 with a publication date of 06/10/2013 an invention is known that relates to methods for obtaining an organic binder material used in briquette production, construction, in particular in the construction of roads, in the construction of buildings and structures. The method for obtaining a binder material includes mixing heavy residues of oil processing and high-temperature coking coal tar in the presence of oxygen, while a surfactant containing a carboxyl group is added to the resin before mixing. The technical result is the expansion of the raw material base for the production of a binder, the disposal of waste from coke production, in particular coal tar.

Also known is an asphalt concrete mix according to GOST 9128-84, prepared by mixing crushed stone, natural crushed sand, mineral powder and petroleum road bitumen in mixing plants in a heated state, taken in proportions determined by the requirements of this standard (see paragraph 3 of the standard). Also, the standard allows the use of an adhesive additive to improve the adhesion of bitumen to stone material.

Also known is a modified asphalt concrete mixture (patent RU 2466161, publ. 11/10/2012), which can be taken as the closest analogue, containing crushed stone, screenings of crushed stone, oil bitumen, in which rubber crumb with a size of 0.75 mm, mechanically activated together with magnesium nanospinel. This additive is added during the manufacture of hot asphalt concrete in the ratio by percentage composition: bitumen grade BND 90/130 in the amount of 100%, rubber crumb in the amount of 7% by weight of the bitumen, magnesium spinel in the amount of 0.5% by weight of the bitumen. In this mixture, nanodispersed magnesium spinel was used as an additive that improves the interaction at the interface "bitumen - rubber crumb". The resulting asphalt concrete has an improved set of strength properties. The increased strength properties of the obtained modified asphalt concrete in a wide temperature range can prevent cracking and increase the durability of the road surface, which can compensate for the costs of additional technological operations (mechanoactivation and the addition of crumb rubber to asphalt concrete).

The main disadvantages of the known solution are the significant costs of dispersing rubber waste, the difficulty of mixing and uniform distribution of the polymer component in the bituminous binder by volume and by the volume of the asphalt concrete mixture, which leads to a decrease in the quality indicators of the binder and the resulting asphalt concrete. Also, other important properties of the bituminous binder are not investigated in the source.

Thus, the object to which the present invention is directed is to provide an alternative modified bitumen-based binder with improved properties, inexpensive and effective for use.

The problem is solved by using petroleum coke powder with a particle size of 0.055-0.075 mm as a bitumen modifier in the amount of 5-15% of the total mass of coke and bitumen in the composition of the asphalt concrete mixture.

It is preferable to use petroleum coke powder in an amount of 6-12%, in particular 10% of the total mass of coke and bitumen in the composition of the asphalt concrete mixture.

Petroleum coke in the preferred embodiment is preliminarily subjected to heat treatment at a temperature of 250-1550°C until a moisture content of not more than 1 wt.%.

To obtain a powder, petroleum coke with a moisture content of not more than 1 wt.% is crushed to a particle size of 0.055-0.075 mm.

From the standpoint of the law of affinity of the structures of materials, the modifier in its chemical composition should be close to the chemical composition of bitumen. From the standpoint of improving properties, the modifier should have similar dimensions to those bitumen components that determine its properties to the greatest extent. We have found that the material that meets these requirements is coke.

The technical result of the claimed invention is as follows.

The introduction of coke into bitumen gives the stability of the surface layer on the pavement being laid, increases viscosity, strength, slows down the aging process, a layer formed from oils and resins is formed on its surface, and voids are also filled and, in general, the performance of the roadway is increased. Allows you to achieve maximum shear resistance of plastic flow at low temperatures, has a greater resistance to breaking load. Also, the use of petroleum coke with a particle size of 0.055-0.075 mm as a bitumen modifier makes it possible to reduce the amount of mineral powder in the composition of the asphalt concrete mixture without deteriorating the properties of the resulting asphalt concrete pavement.

The influence of coke on the medium being modified depends on the size, shape, properties of the surface and the presence of functional groups on it. It has been established by X-ray diffraction that the structural elements of carbon particles in coke are flat crystal lattices. They consist of six-membered carbon cycles (similar to benzene in the arrangement of carbon atoms). Carbon atoms form layers of condensed ring-like systems with an interatomic distance of 0.142 nm. These layers (lattices) are arranged in parallel at a strictly defined distance equal to 0.365 nm. The carbon particles prevailing in coke consist of separate primary formations - crystallites.

Thus, carbon particles in coke have a dimension relatively close to that of asphaltenes. Carbon particles are spherical globules and have a large specific surface area.

There is a genetic link between asphaltenes and carbon in coke. When moving from oils to resins and asphaltenes, the number of condensed cycles, heteroatoms, increases. Therefore, when mixing particles of carbon in coke with bitumen, a layer formed from oils and resins is formed on its surface, forming a structure in the form of a “hedgehog”, and voids are also filled. The result is a redistribution of bitumen components between molecular structures and the formation of new associates. The formation of additional dispersed particles strengthens the matrix of the material, increases the viscosity and strength. In addition, by binding the light components of bitumen, coke slows down the aging process.

It was experimentally found that the introduction of petroleum coke with a particle size of 0.055-0.075 mm into bitumen in an amount of 5-15 wt.% of the total mass of bitumen and coke improves the quality indicators of the resulting bituminous binder and asphalt concrete mixture.

This allows you to transfer the maximum amount of bulk bitumen to the state of "thin films", increase its viscosity and strength.

The invention is used to create new modified binders based on bitumen with improved properties for the manufacture of asphalt mixtures. Bituminous compositions with the addition of coke according to the proposed invention can be added to standard asphalt mixes, such as those described in GOST 9128-84, however, mineral powders may not be used.

For the implementation of the invention can be used viscous oil road bitumen, for example, grades BND 40/60, BND 60/90, BND 70/100, BND 90/130, BN 60/90, BN 90/130, liquid bitumen, roofing grades, etc. .p., but this list is not exhaustive.

To obtain a powder, petroleum coke is subjected to preliminary heat treatment at a temperature of 250-1550°C until it reaches a moisture content of not more than 1 wt.%. with its subsequent grinding to a particle size of 0.055-0.075 mm.

Heat treatment can be carried out at any temperature in the stated range, its purpose is to reduce the moisture content of the coke to values not exceeding 1 wt.%.

This is expedient for carrying out the process of grinding coke to a particle size of 0.055-0.075 mm, the specified grinding of petroleum coke provides easier and more uniform mixing with bituminous binder and greater filling (structuring).

The choice of the specified particle size range is due to the technical requirements for mineral powders GOST 32761-2014 and allows us to consider the possibility of replacing the organo-mineral components in the bituminous binder for asphalt concrete mixtures with petroleum coke powder.

The implementation of the invention is illustrated by the following examples.

Example 1

To prepare 1 ton of bituminous binder, 140 kg of petroleum coke powder with a particle size of 0.055-0.063 mm and 860 kg of bitumen are used. In the composition of this mixture, the amount of coke powder is 14 wt.% of the total mass of coke and bitumen. In the composition of asphalt concrete mixtures, the specified composition of modified bitumen (bitumen together with petroleum coke powder) is used, focusing on the bitumen content in asphalt concrete mixtures in accordance with the requirements of GOST R 58406.2-2020.

Example 2

To prepare 1 ton of bituminous binder, 60 kg of petroleum coke powder with a particle size of 0.063-0.075 mm and 940 kg of bitumen are used. As part of this mixture, the amount of coke powder is 6 wt.% of the total mass of coke and bitumen. In the composition of asphalt concrete mixtures, the specified composition of modified bitumen (bitumen together with petroleum coke powder) is used, focusing on the content of bitumen in asphalt mixtures in accordance with the requirements of GOST_32058-2013.

Example 3

To prepare 1 ton of bituminous binder, 100 kg of petroleum coke powder with a particle size of 0.060-0.070 mm and 900 kg of bitumen are used. In the composition of this mixture, the amount of coke powder is 10 wt.% of the total mass of coke and bitumen. In the composition of asphalt concrete mixtures, the specified composition of modified bitumen (bitumen together with petroleum coke powder) is used, focusing on the content of bitumen in asphalt mixtures in accordance with the requirements of GOST R 58406.10-20.

To analyze the properties of the modified bitumen for research, electrode coke total brand A was taken.

Data on the characteristics of coke are presented in Table 1.

Table 1
Quality certificate for electrode coke total, grade A Name of indicator Test method Meaning Mass fraction of total moisture, %, no more GOST 27588 12.3 Mass fraction of volatile substances, %, no more GOST 22898 p.4.9 7.8 Ash content, %, no more GOST 22692 0.15 Mass fraction of sulfur, %, no more GOST 1437 1.40 Mass fraction of fines with a size of pieces less than * mm,%, no more GOST 22898 p.4.3 51.4 Mass fraction, % no more:
silicon;
gland;
vanadium GOST 22898 p.4.6 0.005
0.007
0.0214

The moisture content of petroleum coke was brought to a value of not more than 1%, and then the coke was crushed to a fine state.

The influence of the addition of finely dispersed coke on the properties of the bituminous binder was studied. Bitumen BND 70/100 was used as bitumen.

Research data are shown in Table 2.

table 2
Properties of bituminous binder obtained on the basis of BND 70/100 bitumen with the addition of coke Qty
introduced
additives Properties of modified bitumen T size, °С
according to kish penetration
at 25°C,
units ductility,
cm adhesion, in
points* BND 70/100 46 86 78 2 +7 48.6 79 75 4 +10 50.15 76 62 5 +14 63.4 57 60 4

* Explanation of scores when bonding a binder to the surface of a mineral material to assess adhesion:

2 - "unsatisfactory", less than 75% of the surface of the gravel particles is covered with a binder film;

3 - “satisfactory”, 75% of the surface of gravel particles is covered with a binder film;

4 - “good”, 90% of the surface of gravel particles is covered with a binder film;

5 - 95% of the surface of the gravel particles is covered with a binder film.

The choice of the percentage of coke is due to the following reasons.

With an increase in the amount of additive, there is an increase in the softening temperature according to R&S, which characterizes the transition of bitumen from an elastic-plastic state to a viscous one.

This is due to the fact that when the additive is introduced into bitumen, the resins are adsorbed on the surface of the particles of the solid additive, as a result of which the volume of the dispersed phase increases and the system thickens. To characterize the viscosity, more precisely, the magnitude of the reverse viscosity, that is, the fluidity of bitumen, a conditional indicator is adopted - the depth of penetration of the needle into bitumen (penetration). The higher the viscosity, the less penetration of the needle into the bitumen.

In our case, the bituminous binder medium is depleted of oils used for additional solvation bonds with the introduced solid additives, therefore, penetration, being a viscosity parameter, begins to decrease due to an increase in the viscosity of the entire system. Ductility at 25°C characterizes the degree of structure of the binder.

An important operational property of bituminous binders is adhesion to mineral materials. Adhesion is an interfacial interaction, the result of the system's desire to reduce the surface energy. The results of determining the adhesion of the bituminous binder to the mineral material indicate that when coke is added to the bituminous binder up to 14 wt.%, its adhesion to the mineral part of asphalt concrete increases.

This can be explained by the fact that there are various functional groups on the surface of coke particles, such as hydroxyl, carbonyl, and quinoid groups, which can improve the adhesive properties of the material.

The use of coke powder in an amount of up to 5 wt.% does not give a visible effect. The amount of coke more than 14 wt.% is not cost-effective from an economic point of view, and may also lead to deterioration of some indicators of the binder.

The polarity of asphaltenes decreases, intramolecular hydrogen bonds are weakened, which violates the heterogeneous structure of the binder, and the density of intermolecular hydrogen (associative) bonds decreases, which in this case are responsible for adhesion to the mineral material. Ultimately, it contributes to an increase in plastic deformations and a decrease in the water resistance coefficient, including during long-term water saturation of asphalt concrete.

Coke powder has a high structuring effect on bitumen. After interaction with coke powder in bitumen, the amount of oils decreases, the amount of asphaltenes increases, i.e. bitumen passes into the state of thin films, characterized by increased viscosity and strength of the binder. In the process of this interaction, the formation of chemisorption compounds occurs, which positively affect the strength characteristics of asphalt binders.

It has been established that binders obtained using petroleum coke powder have a developed surface relief with high microroughness. Due to this, there is an increase not only in the strength characteristics of asphalt concrete samples, but also an increase in corrosion resistance - water resistance during prolonged water saturation and frost resistance of asphalt concrete, which will positively affect the durability of asphalt concrete pavements during operation.

It was found that as a result of the adsorption of the low molecular weight part of bitumen by coke carbon grains and its subsequent "sweating" on the surface of the grains, there is a slowdown in the aging of the binder in asphalt concrete, due to which it is expected to extend the life of road pavements without the need for repairs.

Claims (5)

1. The use of petroleum coke powder with a particle size of 0.055-0.075 mm as a bitumen modifier in an amount of 5-15% of the total mass of petroleum coke powder and bitumen in the composition of the asphalt concrete mixture. 2. Use according to claim 1, characterized in that petroleum coke powder is used in an amount of 6-12% of the total mass of petroleum coke powder and bitumen in the composition of the asphalt concrete mixture. 3. The use according to claim 1, characterized in that the powder of petroleum coke is used in an amount of 10% of the total mass of powder of petroleum coke and bitumen in the composition of the asphalt mixture. 4. Application according to claim 1, characterized in that the petroleum coke is preliminarily subjected to heat treatment at a temperature of 250-1550°C until it reaches a moisture content of not more than 1 wt.%. 5. Use according to claim 4, characterized in that petroleum coke with a moisture content of not more than 1 wt.% is crushed to a particle size of 0.055-0.075 mm.