Bitumen penetration index formula. Viscous bitumen penetration index. Varieties of road bitumen

Federal agency by education Moscow State Academy of Fine Chemical

technology them. M.V. Lomonosov

Department of Technology of Petrochemical Synthesis and Artificial liquid fuel them. A.N. Bashkirova

Likhterova N.M., Nikolaev A.I.

PROPERTIES AND METHODS FOR DETERMINING THEIR CHARACTERISTICS.

Methodical instructions for implementation laboratory work

Moscow, 2008

BBK 35.514я73 UDC 541.127: 665.642

Likhterova N.M., Nikolaev A.I.

BITUMENS. PROPERTIES AND METHODS FOR DETERMINING THEIR CHARACTERISTICS.

Methodical instructions for laboratory work M, MITHT im. M.V. Lomonosov, 2008, 35s.

The manual contains a section dedicated to the properties of bitumen, as well as a section that presents methods for determining the physical and mechanical characteristics that determine these properties.

Designed for 4 - 6 year students studying in the areas of higher engineering school 072000 "Standardization and certification", 250400 - " Chemical Technology natural energy carriers and carbon materials ”, as well as in the direction of magistracy 550808 -“ Chemical technology of natural energy carriers and carbon materials ”.

Reviewer: senior researcher TsKP MITHT them. M.V. Lomonosov, Ph.D. Gorodsky S.N.

© MITHT im. M.V. Lomonosov, 2008

1. Petroleum bitumen.

Natural bitumens have been known to mankind for many thousands of years. Besides natural origin bitumen can be obtained from the processing of oil, shale, peat and coal. In the 20th century, with the development of the oil-extracting and oil-refining industries, the production and consumption of bitumen obtained from petroleum raw materials increased. The scope of their application is wide enough. So they are used as building and waterproofing materials in the construction of foundations of buildings and roofs (insulating and roofing bitumen), a binder for road construction (road bitumen), etc. It should be noted that for the successful application of bitumen, they must have a certain set of properties.

1.1. Bitumen properties. 1.1.1. Viscosity.

At high temperatures, bitumens approach in their properties to a liquid, and at low temperatures they acquire the properties of a solid. For road bitumen, viscosity as a performance indicator is important in two cases. During the mixing of bitumen with mineral materials, they must have a sufficiently low viscosity to ensure ease and efficiency of mixing and laying the mixture into the coating. During the operation of the road surface, bitumen must have a very high viscosity at elevated temperatures, providing it with the necessary strength. Therefore, viscosity is one of the main characteristics of the structural and mechanical properties of bitumen. The viscosity of bitumen varies widely depending on the chemical composition and temperature. The quantitative ratio of asphaltenes and oils has a significant effect on the viscosity of bitumen. With an increase in the amount of asphaltenes, the viscosity increases. To increase the durability of the pavement, it is important that the viscosity of the bitumen changes to a lesser extent in the temperature range at which the pavement is used.

The marker of viscous road bitumen, which indirectly determines their viscosity, is the indicator of the depth of needle penetration (penetration) into the bitumen at temperatures of 25 and 0 ° C. The higher the asphaltene content in the bitumen, the lower the needle penetration depth. The penetration depth of the needle indirectly characterizes such performance qualities of bitumen as hardness, strength and heat resistance.

A marker of liquid road bitumen is the conditional viscosity index, characterized by the expiration time in

seconds 50 ml of bitumen through a 5 mm hole at 60 ° C and determined using a standard viscometer.

1.1.2. Softening point.

The temperature at which bitumens from a relatively solid state pass into a liquid state is conventionally called the softening temperature. The softening point is also a conditional indicator of the viscosity of bitumen at higher temperatures. The more viscous bitumen has a higher softening point. With the same depth of needle penetration, bitumen with a higher softening point is also more heat resistant. Bitumen with a low softening point have low strength at elevated temperatures.

The softening point depends on the composition of the bitumen. The higher the ratio of the asphaltene content to the content of the liquid components of bitumen - resins and oils.

For the quality of bitumen, the ratio between the needle penetration depth and the softening temperature is of great importance. More valuable are bitumens, which at a given softening point have a higher index of the penetration depth of the needle. This means relatively less susceptibility of bitumen to temperature changes.

Thus, the viscosity of bitumen has a significant effect on the properties of the asphalt concrete mixture during mixing, laying and compaction, as well as on construction and technical properties of asphalt concrete. The high viscosity of bitumen increases the strength, water resistance and heat resistance of asphalt concrete, but bitumens with increased viscosity less envelop the surface of mineral materials, so bitumen should be used with a certain viscosity and at certain heating temperatures, taking into account climatic conditions construction area, type, brand and type of asphalt concrete, road category.

This indicator serves for the operational assessment of bitumen and links the softening temperature and the penetration depth of the needle. Penetration index (I.P.) is expressed as an abstract number, determined by the formula:

And. P. \u003d 1 + 30 50 A - 10

A \u003d 2.9031 - logP

T - 25

where P is the depth of penetration of the needle at 25 ° C, 0.1 mm;

Т - softening temperature, ° С.

The peneration index characterizes the coloidal properties of bitumen, their plastic properties and their dependence on temperature.

According to the index of penetration, bitumen is divided into three groups:

1. bitumens and IP 2 (sol), which do not have a dispersed phase or contain highly pentatized asphaltenes (bitumen from cracked residues or pitches from coal tar). The elasticity of such bitumen (ductility at 25 ° C) is close to zero;

2. bitumen and PI from -2 to +2 (sol-gel) there are elements for the formation of a spatial coagulation framework with interlayers of a dispersed medium that prevents the aging of bitumen (bitumen for road construction);

3. bitumens with PI 2 are gels and are prone to aging. Requirements of modern GOST 22245-90 for viscous road

bitumen provides for a change in IP from -1 to +1.

1.1.4. Extensibility.

The extensibility of bitumen is assessed by their ability to stretch into a thread of a certain length under the influence of load.

The extensibility of bitumen depends on their temperature, group composition and structure. Bitumen with a high resin content with an optimal oil and asphaltene content have a high plasticity. As the temperature rises, the extensibility of bitumen increases. Bitumen with a large depth of needle penetration also have a high elongation. With an increase in the content of solid paraffins in the bitumen, the extensibility of the bitumen decreases.

The extensibility of bitumen indirectly characterizes their adhesion to mineral materials. With increasing extensibility, the adhesion of bitumen to mineral materials increases, which is explained by the significant content of aromatic compounds and resins in the bitumen. The extensibility of bitumen at 25 ° C also characterizes the degree of structuring of bitumen and the type of its dispersed structure.

One of the following is closely related to the elasticity of bitumen at low temperatures essential properties asphalt concrete - its deformability at low operating temperatures. Insufficient deformability leads to rapid destruction of asphalt concrete cracks appear in the pavement. Increasing the extensibility of bitumen at low temperatures is the most important task for researchers and engineers.

1.1.5. Brittleness temperature.

The lowest temperature at which bitumen under given test conditions loses its viscoplastic properties and becomes brittle is called the brittleness temperature.

Brittleness temperature is one of the critical indicators quality of road, roofing and a number of other bitumen, which characterize the operation of bitumen-containing materials at low temperatures. The lowest possible brittleness temperature of bitumen is desirable, since such bitumen has better plastic properties, and road or roof coatings work better in harsh climates and cold weather. Bitumen coatings with a high brittle temperature at low temperatures crumble, crack and quickly break down.

The presence of paraffin-naphthenic and monocyclic aromatic compounds causes a low temperature of brittleness, bitumen.

The magnitude of the temperature interval between the softening temperature and the brittleness temperature is called the plasticity interval. Bitumen with a wide plasticity range (more than 70 ° C) have an increased deformation capacity, resistance to cracking at low temperatures and shear resistance at three elevated summer temperatures. The greater the value of the temperature range in which the bitumen is in the viscoelastic state, the better its operational properties. Such bitumen usually also exhibits good adhesion to the surface of the mineral material.

1.1.6. Adhesion to the surface of mineral materials

(adhesion).

The ability of bitumen to firmly adhere to the surface of mineral particles prevents the crumbling of mineral material from the monolith of the road surface and ensures its frost and water resistance.

The adhesion of bitumen to mineral material depends on the properties of the bitumen and mineral materials, as well as on the external conditions in which the mixing is carried out and the road surface works.

The cohesion of bitumen is determined by the polarity of the molecules of the mixture components. In bitumen, molecules of asphaltenes and asphaltotene acids and their anhydrides have significant polarity.

Bitumen adhere well to the surface of mineral materials of carbonate and basic rocks and poorly - to the surface of acidic (SiO2 content more than 65%) rocks (granite).

The cohesion of bitumen increases with increasing temperature, and the presence of moisture on the surface of the mineral material sharply reduces the cohesion of bitumen.

Water-soluble compounds include compounds that are extracted with water in the form of a solution or released from bitumen in the form of emulsions. As a rule, these are low molecular weight compounds (acids or alkalis) and some salts of organic acids.

The presence of water-soluble compounds in bitumen leads to the fact that upon contact of bitumen with water, these substances are extracted. The process of washing out individual components from the composition of the bitumen binder contributes to the formation of microcracks (voids) in the road surface, which in turn leads to its destruction in winter due to the wedging effect of water in the crystalline state. In this case, the mineral material can be exposed and then crumble from the road surface.

1.1.8. Aging.

It is customary to call aging a set of irreversible changes in the chemical composition, structure and properties of bitumen occurring when the bitumen is exposed to various factors - temperature, light, air, water, mineral materials and mechanical stress.

As a result of aging, bitumens increase their viscosity and brittleness. An increase in viscosity occurs due to a change in the group composition of bitumen - resins are converted into asphaltenes, asphaltenes are partially converted into carbenes and carboids, and the content of aromatic compounds decreases. With long-term storage of bitumen in the open air, cracks, peeling appear on its surface as a result of oxidation, and adhesion to mineral materials deteriorates. Such changes physical properties and the chemical composition of bitumen are mainly associated with the processes of oxidation and polymerization occurring in bitumen and are less dependent on the evaporation of light fractions.

The characteristic of the resistance of bitumen against aging (stability) under conditions of prolonged storage at elevated temperatures is an increase in the softening temperature after heating.

Bitumen with a higher initial viscosity are subject to less changes from atmospheric factors than bitumen with a lower initial viscosity. The intensity of aging increases in bitumen when it is heated in the presence of mineral materials that act as catalysts. Also, the intensity of aging of bitumen in asphalt concrete pavement is significantly influenced by the volume and structure of the pores of asphalt concrete. Large volume of open

9 (communicating) pores, contributing to enhanced air and water circulation, intensifies the aging process of bitumen. In dense asphalt concrete, characterized by closed pores, the aging of bitumen is less intense. The intensity of aging of bitumen is the greater, the thinner the layer of asphalt concrete.

1.1.9. Fire safety of bitumen.

When bitumen is heated, gaseous products are released, which can ignite in the presence of an open flame. To protect bitumen from ignition during their manufacture and use, it is necessary to take into account the flash and autoignition points.

Flash point is the temperature at which the gaseous products of heated bitumen form a mixture with the surrounding air, which flares up when a flame is brought to it.

Autoignition temperature is the temperature of gaseous products released from heated bitumen, which, when mixed with air after ignition, burn for at least 5 s.

In practice, the magnitude of the flash point and self-ignition is judged on the fire hazard and expected losses from the evaporation of bitumen.

1.2. Raw materials for the production of petroleum bitumen.

The main raw materials for the production of bitumen are residues of vacuum distillation of oil - tar, as well as by-products of oil production - deasphalting asphalts, that is, asphalt-resinous substances precipitated from tar, as a rule, with liquid propane. They are also called precipitated bitumen. In some cases, cracked residues from a thermal cracking unit are used to produce bitumen.

It should be noted that in order to obtain high-quality bitumen with high thermal stability, good binding properties, it is advisable to use tars of heavy oils of naphthenic aromatic base, containing many asphalt-resinous substances. However, for the production of bitumen on a large scale, it is necessary to use oil of mass production. For example, the possibility of obtaining bitumen from oils was studied, the characteristics of which are presented in table 1, 22 fields of Turkmenistan.

Table 1 Composition of oil fields in Turkmenistan.

Using the classification of oils developed by the BashNIINP Institute (classification 1), the results presented in it were obtained by the content of asphaltenes (A), resins (C) and paraffins (P).

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BITUMENS OIL ROAD VISCOUS

Technical conditions

GOST
22245-90

INDUSTRIAL STANDARDS

Moscow

1996

STATE STANDARD OF THE UNION OF SSR

Date of introduction 01.01.91

This standard applies to viscous road petroleum bitumen intended as a binder for the construction and repair of road and airfield pavements. Mandatory requirements for the quality of petroleum road viscous bitumen are set out in clause 5.

1. TECHNICAL REQUIREMENTS

1.1. Viscous oil road bitumen is produced by oxidation of products of direct distillation of oil and selective separation of oil products (deasphalting asphalts, extracts of selective purification), as well as compounding of the indicated oxidized and non-oxidized products or in the form of a residue of direct distillation of oil in accordance with the requirements of this standard according to the technological regulations approved in the prescribed manner. It is allowed to use the cracked residue as a component of the oxidation feedstock.

1.2. Characteristics

1.2.1. Depending on the penetration depth of the needle at 25 ° C, viscous road oil bitumens are produced of the following grades: BND 200/300, BND 130/200, BND 90/130, BND 60/90, BND 40/60, BN200 / 300, BN 130/200, BN 90/130, BN 60/90.

Scope of bitumen in road construction - in accordance with.

-1.0 to +1.0

-1.5 to + 1.0

8. (Deleted, Amendment No. 1).

(Modified edition, Amendment No. 1).

1.2.2. In terms of physical and chemical parameters, bitumen must meet the requirements and standards specified in Art.

1.2.3. Safety requirements

1.2.3.1. Viscous road oil bitumens are flammable substances with a flash point above 220 ° C and a minimum autoignition temperature of 368 ° C in accordance with GOST 12.1.044-89.

1.2.3.2. Maximum permissible concentration of bitumen hydrocarbon vapors in the air working area 300mg / m 3 - in accordance with GOST 12.1.005. The content of hydrocarbon vapors in the air is determined in accordance with GOST 12.1.014-84.

1.2.3.1, 1.2.3.2. (Modified edition, Amendment No. 1) .

1.2.3.3. Bitumen are low-hazard substances and the gradual impact on the human body belongs to the 4th hazard class according to GOST 12.1.007.

1.2.3.4. When working with bitumens, personal protective equipment should be used in accordance with the standard industry standards approved in the prescribed manner.

1.2.3.5. The room in which the bitumen is handled must be equipped with supply and exhaust ventilation.

1.2.3.6. If small amounts of bitumen are ignited, it should be extinguished with sand, felt mat or a foam extinguisher. Developed bitumen fires should be extinguished with a foam stream.

1.3. Environmental requirements

1.3.1. Sealing equipment and preventing bitumen spills are effective measures to protect the natural environment.

1.3.2. Waste from bitumen production (oxidation gases) is rendered harmless by incineration in an afterburner.

2. ACCEPTANCE

2.1. Viscous road oil bitumen is accepted in batches.

A batch is considered any amount of bitumen, homogeneous in terms of quality and accompanied by a single quality document.

2.2. Sample size - according to GOST 2517.

2.3. When unsatisfactory test results are obtained for at least one of the indicators, by definition, repeated tests of a newly selected sample taken from the same batch are carried out.

Retest results apply to the entire batch.

2.4. Elongation at 0° The manufacturer determines the change in the softening temperature after heating periodically at least once every 10 days, the flash point - at least once a month.

2.5. If unsatisfactory results of periodic tests are obtained, the manufacturer transfers tests for this indicator to the category of acceptance tests until positive results are obtained in at least three batches in a row.

3. CONTROL METHODS

3.1. Samples of viscous road bitumen - in accordance with GOST 2517. The mass of the combined sample of each grade of bitumen must be at least 0.5 kg.

3.3 ... The change in the softening temperature after heating is calculated as the difference between the softening temperatures determined according to GOST 11506 before and after the heating test according to GOST 18180.

4. MARKING, TRANSPORTATION AND STORAGE

4.1. Marking, transportation and storage of bitumen - according to GOST 1510.

4.2. Viscous road bitumen belongs to the 9th class of transport hazard according to GOST 19433-88 (subclass 9.1, category 9.13, classification code 9133).

(Introduced additionally, Amendment No. 1).

5. MANUFACTURER'S WARRANTIES

5.1. The manufacturer guarantees that the quality of bitumen meets the requirements of this standard, provided that the conditions of transportation and storage are observed.

The production technology guarantees the adhesion of BND bitumen with reference marble according to sample No. 2 according to GOST 11508-74 by method A.

(Modified edition, Amendment No. 1).

5.2. The guaranteed shelf life of bitumen is one year from the date of manufacture.

ATTACHMENT 1

APPLICATION OF BITUMENS IN ROAD CONSTRUCTION

Table 2

APPENDIX 2

Bitumen penetration index determination table

Table 3

Petroleum Road Bitumen- irreplaceable materials that are part of asphalt concrete mixtures, and are also used in the processing of the roadway and its impregnation. They are produced by processing petroleum products with the addition of various compounds and solvents. Depending on the purposes for which the bitumen will be used, it can be both liquid and viscous.

Varieties of road bitumen

Viscous road bitumen is used in the repair and laying of road surfaces and airfield strips. Its technical characteristics depend on the type: BN or BND.

Road petroleum bitumens (BND) have a higher softening point and a lower brittleness temperature. In addition, penetration at 0 ° is more important than with BN. And the requirements for BND in terms of thermal stability are put forward more stringent.

Oil road bitumen marking

BND are marked depending on their technical characteristics... Depending on the climatic zone in which the men at work, certain types of bitumen are used:

• In areas where the average monthly temperature in the coldest season does not rise above -20 o, BND grades are used: 200 \\ 300, 130 \\ 200 or 90 \\ 130;
• In a warmer climatic zone, where the average monthly temperature of the cold season does not fall below -20 °, in addition to those listed above, bitumen of grade 60 \\ 90 can be used;
• At an average monthly temperature from -5 o to -10 o, not only BND brands, but also BN from 200 \\ 300 to 90 \\ 130 can be used;
• In the warmest climatic zones, where the average monthly temperature in winter does not fall below 0 o, grades BN 90/130 and 60/90 are used, as well as BND 90/130, 60/90 and 40/60.

Liquid bitumens, in turn, are produced by thinning viscous ones using special solvents. The scope of their application is the production of cold asphalt concrete and road repair work. After laying the liquid bitumen, the thinner gradually evaporates and the coating acquires the required hardness. However, this type of material is flammable due to its low flash point.

Coverage of the application of oil road bitumen at the exhibition

The annual Neftegaz exhibition, which takes place at the Expocentre Fairgrounds, covers issues related to the leading industry in our country. The exhibition is one of the five largest industrial exhibitions in the world, which attracts special attention to it. This event provides a meeting place not only for largest companies the oil and gas industry, but also for service providers and equipment, as well as specialists in this field.

The "Neftegaz" exhibition provides an opportunity to assess the state of the industry, study new technologies and trends, and also use this platform for effective solution tasks of the industry. Since petroleum road bitumen is a product of the oil refining industry, the issue of their use is also discussed at the exhibition. Everything related to production and use different types bitumen, can be found at this event.

It is attended not only by the production flagships of our country, but also by the largest foreign companies. Traditionally, exhibitors from China, USA, Norway, Germany, Sweden, South Korea, France, Taiwan, Italy and Finland.

Popularity of oil road bitumen

Oil road bitumens do not lose their popularity and demand even in the difficult situation on the market. They are irreplaceable in many areas: road, construction, industrial and others. And given the constantly developing infrastructure of our country, as well as the construction of a new Trans-Siberian Railway, their importance can hardly be underestimated.

Read our other articles.

BITUMENS OIL ROAD VISCOUS

Technical conditions

GOST
22245-90

IPK PUBLISHING STANDARDS

Moscow

STATE STANDARD OF THE UNION OF SSR

Date of introduction 01.01.91

This standard applies to viscous road petroleum bitumen intended as a binder in the construction and repair of road and airfield pavements. Mandatory requirements for the quality of oil road viscous bitumen are set out in paragraph 5 of Table 1.

1. TECHNICAL REQUIREMENTS

1.1. Viscous road petroleum bitumens are produced by oxidation of products of direct distillation of oil and selective separation of petroleum products (deasphalting asphalts, extracts of selective purification), as well as compounding these oxidized and unoxidized products or in the form of a residue from direct distillation of oil in accordance with the requirements of this standard according to the technological regulations approved in established order. It is allowed to use the cracked residue as a component of the oxidation feedstock.

1.2. Characteristics

1.2.1. Depending on the penetration depth of the needle at 25 ° C, viscous road petroleum bitumens are produced in the following grades: BND 200/300, BND 130/200, BND 90/130, BND 60/90, BND 40/60, BN 200/300, BN 130 / 200, BN 90/130, BN 60/90.

The area of \u200b\u200bapplication of bitumen in road construction is in accordance with Appendix 1.

Table 1

Petroleum road bitumen are divided into viscous and liquid. Viscous bitumen differ: BND ( road petroleum bitumens) and BN ( petroleum bitumens).

Five brands are produced: BND 40/60, BND 60/90, BND 90/130, BND 130/200, BND 130/200 ; petroleum bitumens (BN) - four brands: BN 60/90, BN 90/130, BN 130/200, BN 200/300 (Table 1).

The letters BND mean “ road oil bitumen", Numbers-fractions 40/60, 60/90, etc. indicate the permissible limits of the penetration depth of a standard needle at 25 ° C for the brand, indirectly characterizing bitumen viscosity. Bitumen BND grades are distinguished by good adhesion to stone materials and have a sufficiently high plasticity at low temperatures, resistant to climatic influences. Specifications for viscous petroleum bitumenstandardized by GOST 22245-90.

Viscous petroleum road bitumen used for the preparation of hot, warm and cold asphalt concrete mixtures, for surface treatment, impregnation, and also for liquefaction in order to obtain liquid bitumen used for the preparation of cold asphalt concrete, surface treatment and for mixing on the road, etc.

Viscous bitumen refer to a particular brand based on three main indicators: the depth of penetration of the needle, the softening temperature and the extensibility. The needle penetration depth and extensibility are standardized at two temperatures: 25 ° C and 0 ° C. According to physical and mechanical indicators viscous bitumen must comply with the requirements and standards specified in table. one.

Table 2 shows the definition bitumen penetration indices by the depth of needle penetration at 25 ° C and softening temperature.

At intermediate values \u200b\u200bof the penetration depth of the needle at 25 ° C, the penetration index is determined by interpolation or by the formula

I.P. \u003d -10,

where A \u003d (2.9031 - log P) / (T - 25),

where P is the depth of penetration of the needle at 25 ° C, 0.1 mm;

Т - softening temperature, ° С.

Brittleness temperature of bitumen BN grades are allowed to be determined by the nomogram (Fig. 1).

Scope of bitumen in road construction must comply with the recommendations given in table. 3.

Viscous road petroleum bitumen are flammable substances with a minimum flash point of 368 ° C. The maximum permissible concentration of bitumen hydrocarbon vapors in the air of the working area is 300 mg / m3.

By the degree of impact on the body, bitumens are low-hazard substances and belong to the 4th hazard class.

When working with bitumen the room must be equipped and personal protective equipment must be used. When small amounts of bitumen ignite, it should be extinguished with sand, a felt mat or a foam fire extinguisher; the developed fire should be extinguished with a foam stream.

Waste from bitumen production (oxidation gases) is neutralized by incineration in an afterburner.

Figure: 1. Nomogram for determining the brittleness temperature of road bitumen grades BN

Notes:

1) numbers on straight lines - depth of needle penetration at 25 ° С;

2) when P 0 / P 25 - equal to or greater than 0.27, its value must be taken with the correction according to the graph (a).

Table 1. Technical requirements for road oil bitumen (BND) and oil bitumen (BN)

Table 2. Table for determination of bitumen penetration indices

Table 3. Scope of application of bitumen in road construction

Guaranteed shelf life of bitumen - one year from the date of manufacture.

Important indicators bitumen of BND grades are the adhesion index and the brittleness temperature. Unfortunately, the adhesion index characterizing the adhesion properties of bitumen to acidic and basic rocks has not been reflected in the existing GOST, which is certainly its disadvantage.

If available bitumens do not satisfy necessary requirements, it is necessary to select the composition of bitumen mixtures of petroleum bitumen of two different brands or mixtures of petroleum bitumen with natural. Most often, bitumen is improved by adding modifying additives, such as surfactants, etc.

Improved bitumen and their mixtures, the properties of which are optimized by special chemical treatment and the addition of plasticizers, are used mainly for the device of the upper layers of coatings in order to provide increased heat resistance and dynamic strength.

Before the publication of GOST 22245-90 for viscous oil road bitumen requirements for road bitumen were standardized by GOST 11954, which included requirements for bitumens grades BND and BN.

The developers of this GOST were guided by the oxidized bitumen III structural type according to the classification of A.S. Kolbanovskaya. This type of bitumen differs in intermediate properties from bitumen types I and II, i.e. incorporates both the advantages and disadvantages of bitumen of extreme structural types. Bitumen of BND grades have wider plasticity intervals in relation to bitumen of BN grades, but they have less elasticity.

With regard to residual bitumen grades BN some sources question their recommended scope and believe that these bitumens should be excluded from the existing GOST for viscous road bitumen... However, this point of view raises very weighty objections and disagreement, which are well substantiated by G.N. Kiryukhin. The author notes that in most developed countries in road construction, residual bitumens, which belong to the II structural type, are widely used in road construction. These bitumens are distinguished by high tensile properties, but at the same time they are characterized by narrow plasticity intervals (the difference between the softening temperature and the brittleness temperature). In domestic and foreign publications, great stability is noted bitumen II structural type ("sol") to aging compared to bitumen type III ("sol-gel") and especially bitumen type I ("gel").