Recipe for asphalt concrete mix type in grade 2. Selection of asphalt concrete mixes

In Russia, the most widespread selection of the compositions of the mineral part of asphalt concrete mixtures according to the limiting curves of grain compositions. The mixture of crushed stone, sand and mineral powder is selected in such a way that the curve of the grain size composition is located in the zone bounded by the limiting curves and is as smooth as possible. The fractional composition of the mineral mixture is calculated depending on the content of the selected components and their grain composition according to the following relationship:

j - component number;

n is the number of components in the mixture;

When selecting the grain composition of the asphalt concrete mixture, especially when using sand from crushing screenings, it is necessary to take into account the grains contained in the mineral material finer than 0.071 mm, which, when heated in a drying drum, are blown out and settle in the dust collection system.

These dust particles can either be removed from the mixture or dosed into the mixing plant together with the mineral powder. The procedure for the use of collecting dust is stipulated in the technological regulations for the preparation of asphalt concrete mixtures, taking into account the quality of the material and the characteristics of the mixing plant asphalt.

Further, in accordance with GOST 12801-98, the average and true density of asphalt concrete and the mineral part is determined, and the residual porosity and porosity of the mineral part are calculated from their values. If the residual porosity does not correspond to the standardized value, then calculate the new content of bitumen B (% by weight) according to the following relationship:

With the calculated amount of bitumen, the mixture is again prepared, samples are molded from it, and the residual porosity of the asphalt concrete is again determined. If it meets the required one, then the calculated amount of bitumen is taken as a basis. Otherwise, the procedure for selecting the bitumen content based on approaching the normalized pore volume in compacted asphalt concrete is repeated.

A series of samples is formed from an asphalt concrete mixture with a given bitumen content by a standard compaction method and a full range of indicators of physical and mechanical properties provided by GOST 9128-97 is determined. If the asphalt concrete does not meet the requirements of the standard for any indicators, then the composition of the mixture is changed.

If the internal friction coefficient is insufficient, the content of coarse crushed stone or crushed grains in the sandy part of the mixture should be increased.

At low values ​​of shear adhesion and compressive strength at 50 ° C, the content of mineral powder should be increased (within acceptable limits) or more viscous bitumen should be used. At high strength values ​​at 0 ° C, it is recommended to reduce the content of mineral powder, reduce the viscosity of bitumen, use a polymer-bitumen binder or use plasticizing additives.

With insufficient water resistance of asphalt concrete, it is advisable to increase the content of mineral powder or bitumen, but within the limits that provide the required values ​​of residual porosity and porosity of the mineral part. To increase water resistance, it is effective to use surfactants (surfactants), activators and activated mineral powders. The selection of the composition of the asphalt concrete mixture is considered complete if all indicators of physical and mechanical properties obtained during testing of asphalt concrete samples meet the requirements of the standard. However, within the framework of standard requirements for asphalt concrete, the composition of the mixture is recommended to be optimized in the direction of increasing the operational properties and durability of the constructed structural pavement layer.

Until recently, optimization of the composition of the mixture intended for the construction of the upper layers of road surfaces was associated with an increase in the density of asphalt concrete. In this regard, three methods have been formed in road construction, which are used in the selection of grain compositions of dense mixtures. They were originally named as:

• - an experimental (German) method for the selection of dense mixtures, which consists in the gradual filling of one material with another;
• - the method of curves, based on the selection of the grain composition, approaching the mathematically predetermined "ideal" curves of dense mixtures;
• - American method of standard mixtures, based on proven formulations of mixtures of specific materials.

These methods were proposed about 100 years ago and have been further developed.

The essence of the experimental method for the selection of dense mixtures is the gradual filling of the pores of one material with coarser grains with another finer mineral material. In practice, the mixture is selected in the following order.

To 100 parts by weight of the first material, 10, 20, 30, etc., are added successively, parts by weight of the second, determining, after mixing and compaction, the average density and choosing a mixture with a minimum number of voids in a compacted state.

If it is necessary to form a mixture of three components, then a third material is added in gradually increasing portions to a dense mixture of two materials, and the most dense mixture is also selected. Although this selection of a dense mineral framework is laborious and does not take into account the effect of the liquid phase content and the properties of bitumen on the compaction of the mixture, nevertheless it is still used in experimental research work.

In addition, the experimental method for the selection of dense mixtures was used as the basis for computational methods for composing dense concrete mixtures from bulk materials of various sizes and was further developed in methods of experiment planning. The principle of sequential filling of voids is used in the method of designing the optimal compositions of road asphalt concrete, in which crushed stone, gravel and sand with any granulometry are used.

In the opinion of the authors of the work, the proposed computational and experimental technique allows for optimal control of the structure, composition, properties and cost of asphalt concrete. In the role of variable structural and control parameters, the following are used:

• - coefficients of expansion of grains of crushed stone, gravel and sand;
• - volumetric concentration of mineral powder in asphalt binder;
• - the criterion of the optimality of the composition, expressed by the minimum total cost of components per unit of production.

Based on the principle of sequential filling of cavities in crushed stone, sand and mineral powder, the approximate composition of the mixture for high-density asphalt concrete based on liquid bitumen was calculated.

The content of the components in the mixture was calculated based on the results of the preset values ​​of the true and bulk density of mineral materials. The final composition was refined experimentally by jointly varying the content of all components of the mixture by the method of mathematical planning of the experiment on a simplex. The composition of the mixture providing the minimum porosity of the asphalt concrete mineral backbone was considered optimal.

The second method for selecting the grain size composition of asphalt concrete is based on the selection of dense mineral mixtures, the grain composition of which is close to the ideal curves of Fuller, Graf, Hermann, Bolomey, Talbot-Richard, Kitt-Peff and other authors. In most cases, these curves are represented by power-law dependences of the required content of grains in the mixture on their size. For example, a Fuller particle size distribution curve for a dense mixture is given by the following equation:

D is the largest grain size in the mixture, mm.

To standardize the grain size composition of the asphalt concrete mixture in the modern American design method "Superpave", the granulometric curves of maximum density are also taken, corresponding to a power dependence with an exponent of 0.45.

Moreover, in addition to the control points limiting the range of grains content, an internal limitation zone is also provided, which is located along the granulometric curve of maximum density in the interval between grains with a size of 2.36 and 0.3 mm. It is believed that mixtures with particle sizes passing through the confined zone may have problems with compaction and shear stability, as they are more sensitive to the content of bitumen and become ductile when accidentally overdosed with organic binder.

It should be noted that GOST 9128-76 also prescribed for curves of grain size composition of dense mixtures a limiting zone located between the limiting curves of continuous and discontinuous grain size distribution. In fig. 1 this area is shaded.

Rice. one. - Grain composition of the fine-grained mineral part:

However, in 1986, when the standard was reissued, this limitation was canceled as insignificant. Moreover, in the works of the Leningrad branch of Soyuzdorniya (A.O.Sal), it was shown that the so-called "semi-discontinuous" mixture compositions passing through the shaded zone in some cases are preferable to continuous ones due to the lower porosity of the mineral part of the asphalt concrete, and intermittent ones due to greater resistance to delamination.

The basis of the domestic method for constructing curves of the granulometric composition of dense mixtures was the well-known research of V.V. Okhotin, in which it was shown that the most dense mixture can be obtained provided that the diameter of the particles that make up the material decreases in a ratio of 1:16, and their weight amounts - as 1: 0.43. However, given the tendency to segregate mixtures formulated with such a ratio of coarse and fine fractions, it was proposed to add intermediate fractions. At the same time, the weight amount of a fraction with a diameter 16 times smaller will not change at all if the voids are filled not just with these fractions, but, for example, with fractions with a grain diameter 4 times smaller.

If, when filling with fractions 16 times smaller in diameter, their weight content was 0.43, then when filling with fractions with a grain diameter that is 4 times smaller, their content should be equal to k = 0.67. If we introduce another intermediate fraction with a diameter that decreases by 2 times, then the ratio of the fractions should be k = 0.81. Thus, the weight number of fractions, which will constantly decrease by the same amount, can be expressed mathematically as a series of geometric progression:

Y1 - the amount of the first fraction;

k is the coefficient of escape;

n is the number of fractions in the mixture.

From the resulting progression, the quantitative value of the first fraction is deduced:

Thus, the runoff coefficient is usually called the weight ratio of fractions, the particle sizes of which are 1: 2, i.e., as the ratio of the closest mesh sizes in a standard set of sieves.

Although theoretically the densest mixes are calculated with a run-off ratio of 0.81, in practice, discontinuous mixes have proven to be denser.

This is due to the fact that the presented theoretical calculations for the compilation of dense mixtures by the runoff coefficient do not take into account the spreading of large grains of the material by smaller grains. In this regard, even P.V. Sakharov noted that positive results in terms of increasing the density of the mixture are obtained only with a stepwise (intermittent) selection of fractions.

If the ratio of the sizes of the mixed fractions is less than 1: 2 or 1: 3, then small particles do not fill the gap between the coarse grains, but move them apart.

The curves of the granulometric composition of the mineral part of asphalt concrete with different sag coefficients are shown in Fig. 2.

Rice. 2. - Granulometric composition of the mineral part of asphalt concrete mixtures with different runoff coefficients:

Later, the ratio of particle diameters of adjacent fractions was specified, which excludes the spreading of large grains in a multi-fractional mineral mixture. According to P.I. Bozhenov, in order to exclude the spreading of large grains by small ones, the ratio of the diameter of the fine fraction to the diameter of the coarse fraction should be no more than 0.225 (i.e., as 1: 4.44). Considering the compositions of mineral mixtures tested in practice, N.N. Ivanov suggested using particle size distribution curves with a runoff coefficient ranging from 0.65 to 0.90 for the selection of mixtures.

Particle size distributions of dense asphalt concrete mixtures, focused on workability, were standardized in the USSR from 1932 to 1967. In accordance with these standards, asphalt concrete mixtures contained a limited amount of crushed stone (26-45%) and an increased amount of mineral powder (8-23%). The experience of using such mixtures has shown that waves, shears and other plastic deformations are formed in the pavements, especially on roads with heavy and heavy traffic. At the same time, the roughness of the surface of the coatings was also insufficient to ensure high adhesion to the wheels of cars, based on the conditions of traffic safety.

Fundamental changes to the standard for asphalt concrete mixtures were introduced in 1967. GOST 9128-67 included new mixtures for frame asphalt concrete with an increased content of crushed stone (up to 65%), which began to be provided for in projects of roads with high traffic intensity. In asphalt concrete mixes, the amount of mineral powder and bitumen was also reduced, which was justified by the need to switch from plastic to more rigid mixes.

The compositions of the mineral part of many crushed stone mixtures were calculated using the cubic parabola equation tied to four control grain sizes: 20; 5; 1.25 and 0.071 mm.

When researching and introducing frame asphalt concrete, great importance was attached to increasing the roughness of the pavements. Methods for arranging asphalt concrete pavements with a rough surface are reflected in the recommendations developed in the early 60s of the last century and were initially introduced at the facilities of the Glavdorstroy of the USSR Ministry of Transport. According to the developers, the creation of roughness should have been preceded by the formation of a space frame in the asphalt concrete. In practice, this was achieved by reducing the amount of mineral powder in the mixture, increasing the content of coarse crushed grains, and complete compaction of the mixture, in which the grains of crushed stone and coarse sand fractions are in contact with each other. The production of asphalt concrete with a frame structure and a rough surface was ensured at a content of 50-65% by weight of grains larger than 5 (3) mm. in fine-grained mixtures of type A and 33-55% of grains larger than 1.25 mm. in sand mixtures of type G with a limited content of mineral powder (4-8% in fine-grained mixtures and 8-14% in sandy ones).

Recommendations for ensuring the shear stability of asphalt concrete pavements as a result of the use of frame asphalt concrete by increasing the internal friction of the mineral framework are also present in foreign publications.

For example, road companies from Great Britain, in the construction of asphalt concrete pavements in tropical and subtropical countries, specifically use grain compositions selected according to the cubic parabola equation.

The stability of coatings from such mixtures is provided mainly as a result of mechanical jamming of angular particles, which should be either strong crushed stone or crushed gravel. The use of uncrushed gravel in such mixtures is not permitted.

The resistance of the coatings to shear deformations can be increased by increasing the size of the crushed stone. In the US standard ASTM D 3515-96, asphalt mixes were provided, differentiated into nine grades depending on the maximum grain size from 1.18 to 50 mm.

The higher the grade, the larger the crushed stone and the lower the content of mineral powder in the mixture. Curves of grain compositions, built according to a cubic parabola, provide a rigid frame of large grains when compaction of the coating, which provides the main resistance to transport loads.

In most cases, the mineral part of the asphalt concrete mixture is selected from coarse-grained, medium-grained and fine-grained components. If the true density of the constituent mineral materials differs significantly among themselves, then their content in the mixture is recommended to be calculated by volume.

The proven in practice grain compositions of the mineral part of asphalt concrete mixtures are standardized in all technically developed countries, taking into account their field of application. These compositions are usually consistent with each other.

In general, it is generally accepted that the most developed element of designing the composition of asphalt concrete is the selection of the granulometric composition of the mineral part either according to the curves of optimal density, or according to the principle of sequential filling of pores. The situation is more complicated with the choice of a bituminous binder of the required quality and with the justification of its optimal content in the mixture. Until now, there is no consensus on the reliability of the calculation methods for assigning the bitumen content in the asphalt concrete mixture.

The existing experimental methods for the selection of the binder content suggest different methods of manufacturing and testing of asphalt concrete samples in the laboratory and, most importantly, do not allow sufficiently reliably predicting the durability and operational state of road surfaces depending on operating conditions.

P.V. Sakharov proposed to design the composition of asphalt concrete based on a pre-selected composition of asphalt binder. The quantitative ratio of bitumen and mineral powder in the asphalt binder was selected experimentally depending on the plastic deformation index (by the method of water resistance) and on the tensile strength of the figure-eight specimens. The thermal stability of the asphalt binder was also taken into account by comparing the strength indicators at temperatures of 30, 15 and 0 ° C. Based on the experimental data, it was recommended to adhere to the values ​​of the ratio of bitumen to mineral powder by weight (B / MP) in the range from 0.5 to 0.2.

As a result, asphalt concrete compositions were characterized by an increased content of mineral powder. In further research I.A. Ryb'ev showed that the rational values ​​of B / MP can be equal to 0.8 and even higher. Based on the law of strength of optimal structures (alignment rule), a method for designing the composition of asphalt concrete for the given operational conditions of the road surface was recommended. It was stated that the optimal structure of asphalt concrete is achieved by converting bitumen into a film state.

At the same time, it was shown that the optimal content of bitumen in the mixture depends not only on the quantitative and qualitative ratio of the components, but also on technological factors and compaction modes.

Therefore, the scientific substantiation of the required performance indicators of asphalt concrete and rational ways to achieve them continues to be the main task associated with increasing the durability of road surfaces.

There are several calculation methods for assigning the bitumen content in the asphalt concrete mixture both by the thickness of the bitumen film on the surface of the mineral grains and by the number of voids in the compacted mineral mixture.

The first attempts to use them in the design of asphalt concrete mixtures often ended in failure, which forced to improve the calculation methods for determining the content of bitumen in the mixture. N.N. Ivanov proposed to take into account the better compaction of the hot asphalt concrete mixture and a certain margin for the thermal expansion of bitumen, if the calculation of the bitumen content is based on the porosity of the compacted mineral mixture:

B - the amount of bitumen,%;

P is the porosity of the compacted mineral mixture,%;

c6 - true density of bitumen, g / cm. cub.;

с - the average density of the compacted dry mixture, g / cm. cub.;

0.85 is the coefficient of reducing the amount of bitumen due to better compaction of the mixture with bitumen and the coefficient of expansion of bitumen, which is taken equal to 0.0017.

It should be noted that calculations of the volumetric content of components in compacted asphalt concrete, including the volume of air pores or residual porosity, are performed in any design method in the form of normalization of the volume of phases. As an example, Fig. 3 shows the volumetric composition of type A asphalt concrete in the form of a pie chart.

Rice. 3. - Normalization of the volume of phases in asphalt concrete:

According to this diagram, the bitumen content (% by volume) is equal to the difference between the porosity of the mineral core and the residual porosity of the compacted asphalt concrete. Thus, M. Durier recommended a method for calculating the bitumen content in a hot asphalt concrete mixture in terms of saturation modulus. The saturation modulus of asphalt concrete with a binder was established according to experimental and production data and characterizes the percentage of binder in a mineral mixture with a specific surface area of ​​1 sq. M / kg.

This technique is adopted to determine the minimum bituminous binder content depending on the grain size composition of the mineral part in the LCPC asphalt mix design method. developed by the Central Laboratory of Bridges and Roads of France. The weight content of bitumen according to this method is determined by the formula:

k - asphalt concrete saturation module with binder.

• S - partial residue on a sieve with holes 0.315 mm in size,%;
• s - partial residue on a sieve with openings of 0.08 mm,%;

The method for calculating the bitumen content by the thickness of the bitumen film was significantly improved by I.V. Korolyov. On the basis of experimental data, he differentiated the specific surface area of ​​grains of standard fractions, depending on the nature of the rock. The influence of the nature of stone material, grain size and bitumen viscosity on the optimal thickness of the bitumen film in the asphalt concrete mixture was shown.

The next step is a differentiated assessment of the bitumen capacity of mineral particles smaller than 0.071 mm. As a result of the statistical prediction of the grain composition of the mineral powder and the bitumen capacity of fractions from 1 to 71 μm in size, a method was developed at MADI (GTU) that allows obtaining calculated data that satisfactorily coincides with the experimental content of bitumen in the asphalt concrete mixture.

Another approach to assigning the bitumen content in asphalt concrete is based on the relationship between the porosity of the mineral framework and the grain size composition of the mineral part. Based on the study of experimental mixtures of particles of various sizes, Japanese specialists proposed a mathematical model of the porosity of the mineral core (VMA). The values ​​of the coefficients of the established correlation dependence were determined for crushed stone-mastic asphalt concrete, which was compacted in a rotary compactor (gyrator) at 300 revolutions of the mold. An algorithm for calculating the bitumen content based on the correlation of the pore characteristics of asphalt concrete with the grain size composition of the mixture was proposed in the work. Based on the results of processing an array of data obtained during testing of dense asphalt concrete of various types, the following correlation dependences were established for calculating the optimal bitumen content:

K is the granulometry parameter.

Dcr - the minimum grain size of the coarse fraction, finer than which contains 69.1% by weight of the mixture, mm;

D0 - size of grains of the middle fraction, finer than which contains 38.1% by weight of the mixture, mm;

Dfine - the maximum grain size of the fine fraction, finer than which contains 19.1% by weight of the mixture, mm.

However, in any case, the calculated dosage of bitumen should be adjusted when preparing control mixes, depending on the test results of molded asphalt concrete samples.

When selecting the compositions of asphalt concrete mixtures, the following statement of prof. N.N. Ivanova: "Bitumen should be taken no more than is conditioned by obtaining a sufficiently strong and stable mixture, but bitumen should be taken as much as possible, and in no case less is possible." Experimental methods for the selection of asphalt concrete mixtures usually involve the preparation of standard samples by specified compaction methods and testing them in laboratory conditions. For each method, appropriate criteria have been developed that establish, to one degree or another, the relationship between the results of laboratory tests of compacted samples and the performance characteristics of asphalt concrete under operating conditions.

In most cases, these criteria are defined and standardized by national asphalt concrete standards.

The following schemes of mechanical tests of asphalt concrete samples are widespread, shown in Fig. 4.

Rice. 4. - Schemes for testing cylindrical samples when designing the composition of asphalt concrete:

a - according to Duriez;

b - according to Marshall;

c - according to Khvim;

d - according to Hubbard Field.

An analysis of various experimental methods for designing asphalt concrete compositions indicates a similarity in approaches to prescribing a formulation and a difference both in the methods of testing samples and in the criteria for the evaluated properties.

The similarity of design methods for asphalt concrete mixture is based on the selection of such a volumetric ratio of components, which provides the specified values ​​of residual porosity and normalized indicators of the mechanical properties of asphalt concrete.

In Russia, when designing asphalt concrete, standard cylindrical samples are tested for uniaxial compression (according to the Duryez scheme), which are molded in the laboratory in accordance with GOST 12801-98, depending on the content of crushed stone in the mixture, either by a static load of 40 MPa, or by vibration, followed by additional compaction with a load of 20 MPa. In foreign practice, the most widely used method of designing asphalt concrete mixtures according to Marshall.

Until recently, in the USA, methods of designing asphalt concrete mixtures according to Marshall, Hubbard-Field and Khwim have been applied. but recently, a number of states are introducing the Superpave design system.

When developing new methods for designing asphalt concrete mixtures abroad, much attention was paid to improving the methods of compaction of samples. Currently, when designing mixtures according to Marshall, three levels of sample compaction are provided: 35, 50 and 75 impacts on each side, respectively, for conditions of light, medium and heavy vehicle traffic. The United States Corps of Engineers, through extensive research, refined Marshall testing and extended it to airfield pavement mix design.

Marshall asphalt design assumes that:

• - preliminarily established the compliance of the initial mineral materials and bitumen with the requirements of technical specifications;
• - the granulometric composition of the mixture of mineral materials was selected, which meets the design requirements;
• - the values ​​of the true density of viscous bitumen and mineral materials have been determined by appropriate test methods;
• - a sufficient amount of stone material is dried and divided into fractions to prepare laboratory mixes of mixtures with different binder content.

For tests by the Marshall method, standard cylindrical specimens are made with a height of 6.35 cm and a diameter of 10.2 cm when compacted by impacts of a falling weight. Mixtures are prepared with different bitumen content, usually differing from one another by 0.5%. It is recommended to prepare at least two mixtures with a bitumen content above the "optimal" value and two mixtures with a bitumen content below the "optimal" value.

In order to more accurately assign the bitumen content for laboratory tests, it is recommended to first establish an approximate "optimal" bitumen content.

By "optimal" is meant the content of bitumen in the mixture that provides the maximum Marshall stability of the molded samples. Approximately for the selection it is necessary to have 22 south stone materials and about 4 liters. bitumen.

The results of testing asphalt concrete by the Marshall method are shown in Fig. five.

Based on the results of testing samples of asphalt concrete according to the Marshall method, the following conclusions are usually reached:

• - The value of stability increases with an increase in the binder content to a certain maximum, after which the value of stability decreases;
• - The value of the conditional plasticity of asphalt concrete increases with an increase in the binder content;
• - The curve of dependence of density on the content of bitumen is similar to the curve of stability, but for it the maximum is more often observed at a slightly higher content of bitumen;
• - Residual porosity of asphalt concrete decreases with increasing bitumen content, approaching asymptotically to the minimum value;
• - The percentage of pore filling with bitumen increases with increasing bitumen content.

Rice. five. - Results (a, b, c, d) of tests of asphalt concrete by the Marshall method:

It is recommended that the optimum bitumen content be determined as the average of four values ​​plotted for the respective design requirements. An asphalt mix with an optimal bitumen content must meet all the requirements of the technical specifications. When making the final choice of the composition of the asphalt concrete mixture, technical and economic indicators can also be taken into account. It is generally recommended to select the mixture with the highest Marshall stability.

However, it should be borne in mind that mixtures with excessively high values ​​of Marshall stability and low plasticity are undesirable, since coatings from such mixtures will be excessively hard and can crack when driving heavy vehicles, especially with fragile substrates and high deflections of the coating. Marshall's asphalt design method is often criticized in Western Europe and the United States. It is noted that the impact compaction of the samples according to Marshall does not simulate the compaction of the mixture in the pavement, and the stability according to Marshall does not allow satisfactorily assessing the shear strength of asphalt concrete.

Hvim's method is also criticized, the disadvantages of which include rather bulky and expensive test equipment.

In addition, some important volume metric indicators of asphalt concrete related to its durability are not properly disclosed in this method. According to American engineers, the method for choosing the bitumen content according to Khvim is subjective and can lead to the fragility of asphalt concrete due to the appointment of a low binder content in the mixture.

The LCPC method (France) is based on the fact that hot asphalt mix must be designed and compacted to maximum density during construction.

Therefore, special studies were carried out on the calculated compaction performance, which was determined as 16 roller passes with pneumatic tires, with an axle load of 3 tf at a tire pressure of 6 bar. On a full-scale laboratory bench when compaction of hot asphalt concrete mixture, a standard layer thickness equal to 5 maximum sizes of mineral grains was justified. For the appropriate compaction of laboratory samples, the angle of rotation on the laboratory compactor (gyrator), equal to 1 °, and the vertical pressure on the compacted mixture of 600 kPa were standardized. In this case, the standard number of rotations of the gyrator should be equal to the thickness of the layer from the compacted mixture, expressed in millimeters.

In the American method of the Superpave design system, it is customary to compact asphalt concrete samples also in a gyrator, but at an angle of rotation of 1.25 °. The work on compaction of asphalt concrete samples is standardized depending on the calculated value of the total transport load on the pavement, for the device of which the mixture is designed. A diagram of the compaction of samples from an asphalt concrete mixture in a rotary compaction device is shown in Fig. 6.

Rice. 6. - Scheme of compaction of samples from asphalt concrete mixture in a rotary compaction device:

The MTQ (Department of Transportation of Quebec, Canada) asphalt design method adopts a Superpave rotary compactor instead of an LCPC gyrator. The calculated number of compaction rotations is taken for mixtures with a maximum grain size of 10 mm. equal to 80, and for mixtures with a particle size of 14 mm. - 100 revolutions of rotation. The calculated content of air holes in the sample should be in the range from 4 to 7%. The nominal pore volume is usually 5%. The effective bitumen volume is set for each type of mixture, as in the LCPC method.

It is noteworthy that when designing asphalt mixes from the same materials using the Marshall method, the LCPC method (France), the Superpave design system method (USA) and the MTQ method (Canada), approximately the same results were obtained.

Despite the fact that each of the four methods provided for different conditions for compaction of the samples:

• - Marshall - 75 strikes from both sides;
• - "Superpave" - ​​100 revolutions of rotation in the gyrator at an angle of 1.25 °;
• - MTQ - 80 revolutions of rotation in a gyrator at an angle of 1.25 °;
• - LCPC - 60 revolutions of rotation of an effective compactor at an angle of 1 ° С, quite comparable results were obtained for the optimal content of bitumen.

Therefore, the authors of the work came to the conclusion that it is important not to have the "correct" method of compaction of laboratory samples, but to have a system of influence of the compaction force on the structure of asphalt concrete in the sample and its performance in the pavement.

It should be noted that rotary methods of compaction of asphalt concrete samples are also not without drawbacks. A noticeable abrasion of stone material was found during compaction of a hot asphalt concrete mixture in a gyrator.

Therefore, in the case of using stone materials characterized by wear in the Los Angeles drum of more than 30%, the normalized number of revolutions of the compactor of the mixture when receiving samples of crushed stone-mastic asphalt concrete is set equal to 75 instead of 100.

The most used road building material in the 20th century - asphalt - is divided into many types, grades and types. The basis for separation is not only and not so much the list of the initial components included in the asphalt concrete mixture, but the ratio of their mass fractions in the composition, as well as some characteristics of the components - in particular, the size of the fractions of sand and crushed stone, the degree of purification of the mineral powder and all the same sand.

Asphalt composition

Asphalt of any type and brand contains sand, crushed stone or gravel, mineral powder and bitumen. However, as far as crushed stone is concerned, it is not used in the preparation of some types of road surface - but if asphalting of territories is carried out taking into account high traffic and strong short-term loads on the surface, then crushed stone (or gravel) is necessary - as a frame-forming protective element.

Mineral powder- an obligatory initial element for the preparation of asphalt of any brands and types. As a rule, the mass fraction of powder - and it is obtained by crushing rocks in which a high content of carbon compounds (in other words, from limestone and other organic fossilized deposits) - is determined based on the tasks and requirements for the viscosity of the material. A large percentage of mineral powders allows it to be used in such works as asphalting roads and sites: a viscous (that is, durable) material will successfully dampen the internal vibrations of bridge structures without cracking.

Most types and grades of asphalt use sand- the exception, as we said, is the types of road surface where the mass fraction is high gravel... The quality of sand is determined not only by the degree of its purification, but also by the method of production: the sand extracted by the open method, as a rule, needs to be thoroughly cleaned, but the artificial sand obtained by crushing rocks is considered ready “to work”.

Finally, bitumen is the cornerstone of the paving industry. A product of oil refining, bitumen is contained in a mixture of any brand in a very small amount - its mass fraction in most varieties hardly reaches 4-5 percent. Although widely used in applications such as asphalting areas with difficult terrain and road repairs, cast asphalt boasts a bitumen content of 10 percent or more. Bitumen gives such a canvas a fair amount of elasticity after hardening and fluidity, which makes it easy to distribute the finished mixture over the site.

Grades and types of asphalt

Depending on the percentage in the composition of the listed components, there are three brands of asphalt... Technical characteristics, scope and composition of the mixture of various brands are described in GOST 9128-2009, which, among other things, takes into account the possibility of adding additional additives that increase frost resistance, hydrophobicity, flexibility or wear resistance of the coating.

Depending on the percentage of filler in the road-building mixture, it is divided into the following types:

• A - 50-60% of crushed stone;
• B - 40-50% crushed stone or gravel;
• B - 30-40% crushed stone or gravel;
• G - up to 30% of sand from crushing screenings;
• D - up to 70% of sand or a mixture with crushing screenings.

Asphalt grade 1

A wide range of different types of coatings are produced under this brand - from dense to highly porous, with a significant content of crushed stone. Scope of their use- road construction and improvement: only porous materials are not at all suitable for the role of the actual coating, the upper layer of the roadbed. It is much better to use them for arranging bases, leveling the base for laying denser types of material.

Asphalt grade 2

The density range is roughly the same, but the content and percentage of sand and gravel can vary widely. This is the same "average" asphalt, with a very wide range of applications: and the construction of highways, and their repair, and the arrangement of territories for parking lots and squares cannot do without it.

Grade 3 asphalts

Grade 3 coatings are distinguished by the fact that crushed stone or gravel is not used in their manufacture - they are replaced by mineral powders and especially high-quality sand obtained by crushing hard rocks.

The ratio of sand and crushed stone (gravel)

The ratio of sand and gravel content is one of the most important indicators that determines the area of ​​application of a particular type of coating. Depending on the prevalence of a particular material it is designated by letters from A to D: A - more than half consists of fine gravel or gravel, and D - about 70 percent consists of sand (however, sand is used mostly from crushed rocks).

The ratio of bitumen and mineral constituents

No less important - after all, it is it that determines the strength characteristics of the roadway. The high content of mineral powders significantly increases its fragility. therefore sandy asphalt can only be used to a limited extent: landscaping of parks or sidewalks. But coatings with a high content of bitumen are a welcome guest at any work: especially if it is road construction in harsh climatic conditions, at subzero temperatures, if the speed of work is such that a day later, road equipment will go along the new road, and after the finished road is delivered - heavy vehicles will rush.

It largely depends on the properties of the ingredients in the mixture and their ratio.

There are several types of asphalt concrete, the composition of which is markedly different. In some cases, the composition and quality of the original ingredients are associated with the production method.

• So, for 1–3 climatic zones, dense and high-density AB are made from crushed stone, whose frost resistance class is F50. Porous and highly porous - from stone class F 15 and F25.
• For zones 4 and 5, only high-density hot asphalt is made on the basis of crushed stone of class F 50

We will talk about the role of sand in asphalt concrete below.

Sand

It is added to all types of AB, but in some it is sandy asphalt concrete, it acts as the only mineral part. used both natural - from quarries, and obtained by screenings during crushing. Material requirements are dictated by GOST 8736.

• So, for dense and high-density sand with a strength class of 800 and 1000 is suitable. For porous ones, it is reduced to 400.
• The number of clay particles - less than 0.16 mm in diameter, is also adjustable: for dense particles - 0.5%. For porous - 1%.
• increases the ability of AB to swell and reduces frost resistance, therefore, this factor is monitored especially.

Mineral powder

This part forms the binder together with the bitumen. Also, the powder fills the pores between large stone particles, which reduces internal friction. The grain size is extremely small - 0, 074 mm. They are obtained from a dust collector system.

In fact, mineral powder is produced from the waste of cement enterprises and metallurgical enterprises - this is dust-entrainment of cement, ash and slag mixtures, waste from the processing of metallurgical slags. The grain composition, the amount of water-soluble compounds, water resistance, etc. are regulated by GOST 16557.

Additional components

To improve the composition or impart some specific properties, various additives are introduced into the initial mixture. They are divided into 2 main groups:

• components designed and manufactured specifically to improve properties - plasticizers, stabilizers, anti-aging agents, etc.
• waste or secondary raw materials - sulfur, granular rubber and so on. The cost of such supplements is, of course, much less.

The selection and design of the composition of road and airfield asphalt concrete are discussed below.

The video below will tell you about sampling to assess the composition and quality of asphalt concrete:

Design

The composition of the asphalt concrete pavement device is selected based on the purpose: a street in a small town, a high-speed highway and a bicycle path require different asphalt. To get the best coverage, but not to overspend materials, use the following selection principles.

Basic principles

• The grain composition of the mineral ingredient, that is, stone, sand and powder, is the basis for the density and roughness of the coating. The principle of continuous granulometry is most often used, and only in the absence of coarse sand - the method of intermittent granulometry. Grain composition - particle diameters and their correct ratio must fully comply with the specifications.

The mixture is selected in such a way that the curve fits between the limiting values ​​and does not include fractures: the latter means that there is an excess or deficiency of some fraction.

• Different types of asphalt can form the carcass and frameless structure of the mineral constituent. In the first case, there is enough crushed stone for the stones to come into contact with each other and in the finished product form a clearly defined structure of asphalt concrete. In the second case, stones and grains of coarse sand do not touch. A somewhat conditional boundary between the two structures is the content of crushed stone in the range of 40–45%. When choosing, this nuance must be taken into account.
• The maximum strength is guaranteed by cuboid or tetrahedral crushed stone. This stone is the most durable.
• The roughness of the surface is reported by 50-60% of crushed stone from difficult-to-polish rocks or sand from them. Such a stone retains the roughness of natural cleavage, which is important for ensuring the shear stability of the asphalt.
• In general, asphalt based on crushed sand is more shear resistant than on the basis of open-pit sand due to the smooth surface of the latter. For the same reasons, the durability and resistance of gravel-based materials, especially marine ones, is less.
• Excessive grinding of mined powder leads to an increase in porosity, and, therefore, to a consumption of bitumen. And this is the property of most industrial waste. To reduce the parameter, the mineral powder is activated - treated with surfactants and bitumen. This modification not only reduces the bitumen content, but also increases water and frost resistance.
• When selecting bitumen, one should be guided not only by its absolute viscosity - the higher it is, the higher the density of the asphalt, but also by weather conditions. So, in arid regions, a composition is selected that provides the lowest possible porosity. In cold mixes, on the contrary, the volume of bitumen is reduced by 10-15% in order to reduce the level of caking.

Selection of the composition

The selection procedure is generally the same:

• assessment of the properties of mineral ingredients and bitumen. This refers not only to absolute indicators, but their compliance with the ultimate goal;
• calculate such a ratio of stone, sand and powder so that this part of the asphalt acquires the maximum possible density;
• last of all, the amount of bitumen is calculated: sufficient to ensure the required technical properties of the finished product based on the selected materials.

First, theoretical calculations are carried out, and then laboratory tests. First of all, the residual porosity is checked, and then the compliance of all other characteristics with the expected ones. Calculations and tests are carried out until a mixture is obtained that fully satisfies the task.

Like any complex building material, AB does not have unambiguous qualities - density, specific gravity, strength, and so on. Its parameters determine the composition and preparation method.

The following educational video will tell you about how the design of an asphalt concrete composition in the USA is going on:

The calculation consists in the selection of a rational ratio between the materials making up the asphalt concrete mixture.

The method of calculation from curves of dense mixtures has become widespread. The greatest strength of asphalt concrete is achieved at the maximum density of the mineral skeleton, the optimal amount of bitumen and mineral powder.

There is a direct relationship between the grain size composition of a mineral material and density. Optimal will be compositions containing grains of various sizes, the diameters of which are halved.

where d 1 - the largest grain diameter, set depending on the type of mixture;

d 2 - the smallest grain diameter corresponding to the dusty fraction and mineral powder (0.004 ... 0.005 mm).

Grain sizes as per previous level

(6.6.2)

The number of sizes is determined by the formula

(6.6.3)

Number of fractions NS one less than the number of sizes T

(6.6.4)

The ratio of adjacent fractions by weight

(6.6.5)

where TO is the coefficient of escape.

The value that shows how many times the amount of the next fraction is less than the previous one is called the escape coefficient. The densest mixture is obtained with a slip coefficient of 0.8, but such a mixture is difficult to select, therefore, according to N.N. Ivanova, escape coefficient TO adopted from 0.7 to 0.9.

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1 System of regulatory documents in construction COMPANY STANDARD Procedure for selection and approval of recipes for asphalt concrete mixtures STP Directorate of the regional road fund Kemerovo FOREWORD

2 1. DEVELOPED by the Autonomous Non-Commercial Organization "Kuzbassdorcertification" (Candidate of Technical Sciences, Associate Professor OP Afinogenov, engineer VB Sadkov). 2. INTRODUCED by the Autonomous Non-Commercial Organization "Kuzbassdorcertification". 3. APPROVED and put into effect by the State Institution "Kemerovo Directorate of the Regional Road Fund". 4. INTRODUCED FOR THE FIRST TIME. GU "Kemerovo director. region door fund ", 2000 Enterprise standard The procedure for the selection and approval of recipes for asphalt concrete mixtures Introduced for the first time Approved and put into effect by order of March 13, 2001, 31

3 1. SCOPE Date of introduction This standard establishes the basic requirements for the procedure for selecting recipes for asphalt concrete mixtures, the procedure for their approval when performing road works under contracts with the State Institution "Kemerovo Directorate of the Regional Road Fund" (hereinafter the customer, GU "Kemerovo DODF"). 2. REGULATORY REFERENCES This standard uses references to the following regulatory documents: SNiP System of regulatory documents in construction. Basic provisions; SNiP Automobile roads; SNiP *. Organization of construction production; GOST Testing and product quality control. Basic terms and definitions; GOST Road, airfield and asphalt concrete mixtures asphalt concrete; GOST Materials based on organic binders for road and airfield construction. Test methods; STP Preparation of road bitumen modified with atactic polypropylene. Standard regulations; TU Road bitumen modified with atactic polypropylene. 3. DEFINITIONS 3.1. In this standard, terms and their definitions are used that correspond to GOST 9128, GOST 16504, SNiP, SNiP Asphalt concrete mixture rationally selected mixture of mineral materials (crushed stone [gravel] and sand with mineral powder or without it) with bitumen, taken in certain proportions and mixed in heated state. Asphalt concrete is a compacted asphalt concrete mixture. The recipe for asphalt concrete mixture is a document that is part of the technological regulations, containing information characterizing the scope of the mixture, its composition and physical and mechanical properties, material consumption; approved and agreed in accordance with the established procedure. 4. GENERAL PROVISIONS

4 4.1. The contractor does not have the right to perform work using asphalt concrete mixtures at the facilities of the Kemerovo DODF State Institution without recipes for their production, agreed in accordance with the procedure regulated by this standard. The recipe is drawn up for the construction season, for each mixture used at this facility. It is allowed to draw up one recipe for several objects of the same type.In case of adjusting the recipe based on the results of production control, when replacing materials, etc., the recipe is subject to re-approval in the manner prescribed by the section The recipe must comply with the requirements of project documentation, SNiP, GOST, and other regulatory documents ( VSN, OST, STP, etc.) The selection of the composition of the asphalt concrete mixture should be carried out by an organization that has a competent laboratory and guarantees the reliability of the test results and the completeness of the controlled characteristics (characteristics) of the asphalt concrete mixture. ) a laboratory accreditation system recognized in the prescribed manner, or having a certificate of official assessment of the state of measurements according to MI The recipe for an asphalt concrete mixture is drawn up on the basis of a specially performed selection, the purpose of which is to provide a mixture of the target nny properties Selection (design) of a mixture consists of five stages: 1) the establishment of requirements for the mixture; 2) selection of materials and assessment of their suitability; 3) determination of the rational quantitative ratio of the components of the mixture; 4) quality control of the composition; 5) economic assessment of the quality of the composition The assignment for the design of the asphalt concrete mixture is issued by the chief engineer of the contracting organization. The mixture can be selected by the contractor's road building laboratory or a laboratory involved from the outside. The assignment for the design of the mixture should indicate: the type of asphalt concrete mixture (hot, cold, coarse-grained, fine-grained, sandy); type of asphalt concrete (high-density, dense, porous, highly porous); type of mixture and brand of asphalt concrete; Desired Materials Asphalt mix design should strive to obtain the most economical formulation. 5. PURPOSE OF BASIC PARAMETERS OF THE MIXTURE 5.1. The main parameters and type of mixture (asphalt concrete) are assigned according to the design documentation. If, at the same time, deviations from the requirements of the normative documents in force at the time of the selection of the mixture are found, it is necessary to agree on the parameters with the customer. Asphalt concrete mixtures should

5 to be applied in accordance with SNiP, app. And GOST and meet the requirements of GOST The customer has the right to establish higher indicators of asphalt concrete mixture (asphalt concrete) than stipulated by SNiP (with appropriate compensation for the contractor's costs). of reliable adhesion to the top layer) and high shear resistance On highways with heavy traffic, hot high-density mixtures of type A should be used.To repair minor damage to asphalt concrete pavements, use mixtures similar in properties to the mixtures of the repaired layer of the coating layer. 6. SELECTION OF MIXTURE COMPONENTS 6.1. The materials used for the preparation of asphalt concrete mixtures must comply with the requirements of GOST. It is advisable to use crushed stone from igneous or metamorphic basic and carbonate rocks with better adhesion to petroleum bitumen. Crushed stone should be close to a cube in shape and not have flat flaky grains. Gravel is a less desirable component, as it has a smooth surface, inclusions of weak rocks. An increase in the amount of crushed stone increases the crack resistance and shear resistance of the coatings. It is advisable to use sand, consisting of particles of different sizes. Sand of the same size increases the porosity of the mineral part. Sand from crushing screenings contributes to an increase in the internal friction of the mineral part due to the content of acute-angled grains in it. It is not recommended to use river sand. For asphalt concrete mixtures mineral powders obtained by artificial grinding of limestone and dolomite should be used. The presence of very fine clay particles in the mineral powder increases the swelling of asphalt concrete when wetted, and increases the bitumen capacity of the mixture. A large number of particles larger than 0.071 mm increases the consumption of mineral powder and complicates the process of preparing and placing the mixture. The properties of the binder largely determine the quality of asphalt concrete. Excessive viscosity of bitumen leads to cracking at low temperatures, and low viscosity to plastic deformation of coatings in hot weather. In accordance with the requirements of SNiP in the conditions of the Kemerovo region, it is necessary to use polymer-bitumen binders (modified bitumen). For modification use polymer-bitumen binder grades PBV, "Caudest-D", bitumen-rubber binder grades BKV, it is allowed to use atactic polypropylene of APP-G / B grade on territorial roads (the binder must meet the requirements of TU Bitumen preparation,

6 modified with atactic polypropylene, carried out according to STP Polymer additives increase the elasticity of bitumen, its thermal stability in a wide temperature range, strength and corrosion resistance of asphalt concrete. It should be borne in mind that with a lack or excess of bitumen, the mechanical strength of concrete decreases. With an increase in the amount of bitumen, the water resistance of asphalt concrete increases due to a more complete enveloping of stone materials with a bitumen film and filling of pores, and heat resistance decreases. With a decrease in the amount of bitumen, the opposite phenomenon is observed: water saturation increases, water resistance decreases, and heat resistance increases, concrete becomes more rigid and brittle. 7. CALCULATION OF THE MIXTURE COMPOSITION 7.1. The design of the composition of the asphalt concrete mixture (asphalt concrete) can be performed according to any known method. It is recommended to use the SoyuzdorNII method, which is the focus of GOST. The method is based on the assumption that the strength of concrete is determined by its structure and is ensured by the creation of a dense mineral mixture with an optimal amount of bitumen. .e. use mixtures of types A and B Calculation of asphalt concrete includes two stages: calculation of the granulometric (grain size) composition of the mineral part of the mixture from a given set of materials according to tables of granulometric composition (tables 2 and 3 of GOST); experimental determination of physical and mechanical parameters of asphalt concrete, assessment of their compliance with GOST requirements, as well as selection of the optimal amount of bitumen by testing test samples with the same composition of stone materials and different content of bitumen The criterion for determining the optimal amount of bitumen is the best correspondence between water saturation and mechanical compressive strength at temperature 20 С and 50 С of test specimens corresponding to the requirements of GOST EXAMPLE OF CALCULATION OF THE COMPOSITION OF A FINE-GRANULAR MIXTURE 8.1. Task: Calculate the composition of fine-grained hot asphalt concrete type B, grade II. Component materials: Crushed stone of the Mozzhukhinsky quarry, fraction 5-20 mm; Sand of the Yaya Combine of Building Materials;

7 Limestone mineral powder. Calculation procedure. Based on the limits of the required granulometric compositions (Table 3 of GOST) and according to the results of sieving the mineral materials used (Table 1), we determine the approximate percentage of each material (crushed stone, sand, mineral powder). Table 1 Name of material, manufacturer or quarry Particular residues (number of grains,% by weight, less remaining on a sieve with a mesh size, mm), 5 1.25 0.63 0.315 0.14 0.071 less Crushed stone of the Mozzhukhinsky quarry, fr mm Yaysky sand KSM Mineral powder 5.3 33.7 30.2 23.6 3.7 3.5 1.0 18.5 17.0 7.5 12.4 24.6 8.8 4.2 6.0 1, 2 2.0 8.6 16.6 71.6 Content of crushed stone X a 45 = 100 = 100 = 48.49% b 92.8 where a is the average value of total residues on a sieve with a diameter of 5 mm, required by table. 3 GOST; b Content of a fraction larger than 5 mm in crushed stone. Content of mineral powder a1 6 Z = 100 = 100 = 8.4% b 71.6 1 where a1 is the minimum allowable content of fraction "less than 0.071 mm" in the composition of asphalt concrete type B (table 3 GOST); b1 content of fraction finer than 0.071 mm in mineral powder. Taking into account the presence in the sand of grains with a grain size of more than 5 mm and finer than 0.071 mm, we reduce the above values ​​of the content in the mixture of crushed stone and mineral powder to the following values: crushed stone 42.0%, mineral powder 7.0%. Then the content of sand in the mixture. Fill in table 2. Y = 100 (x + z); Y = 100 (42 + 7) = 51%

8 Comparison of the data in column 10 with the data in column 11 indicates that the composition of the designed mineral part of the asphalt concrete mixture corresponds to the required compositions of dense mixtures. Table 2 Calculation table for determining the total residues of the projected mineral mixture Size of the sieve holes in mm Granulometric composition of the constituent materials in% crushed stone sand mineral powder Granulometric composition of materials in the projected mixture in% crushed stone sand mineral powder Particular residues of the projected mineral mixture in% Total residues of the projected mineral mixture in% Full passes Allowable limits of full passes according to GOST, 3 2.2 2.2 2.2 97.7 14.2 14.2 16.4 83.2 1.0 12.6 0.5 13.1 29, 5 70.6 18.5 9.9 9.4 19.3 48.8 51.5 3.7 17.0 1.6 8.7 10.3 59.1 40.25 3.5 7.5 1 .5 3.8 5.3 64.4 36.63 12.4 1.2 6.3 0.1 6.4 70.8 29.315 24.6 2.0 12.5 0.1 12.6 83, 4 16.14 8.8 8.6 4.6 0.6 5.2 88.6 11.071 4.2 16.6 2.1 1.2 3.3 91.9 8, Less than 6.0 71.6 3.1 5.0 8, Determine the percentage of bitumen in accordance with the recommendations of Appendix G GOST, it is 5.0-6.5%. Based on this, we prepare three asphalt concrete mixtures with the same mineral composition and the estimated amount of bitumen (5.0-5.8-6.5%). Test specimens are made from these compositions, which are tested for compression at a temperature of +20 and +50 C and for water saturation. The optimal amount of bitumen is taken to be its content at which the best performance of asphalt concrete was achieved. We make control samples of the designed composition with the optimal amount of bitumen and subject them to a full cycle of tests. The test results are entered in table 3. Table 3 Indicators of the properties of asphalt concrete

9 Indicator name GOST requirements Actual indicators Indicator name GOST requirements Actual indicators Average density, 2.38 Water resistance at g / cm 3 long-term water saturation Porosity of the mineral part by volume,% Residual porosity,% 19 16.3 Adhesion of bitumen to the mineral part 2.5 5.0 3.4 Shear resistance index Water saturation,% 1.5 4.0 2.8 Crack resistance index Compressive strength at temperature, MPa Total specific effective activity of natural radionuclides, Bq / kg 0.75 0.87 Withstands With 2 , 2 2.6 50 С 1.0 1.1 0 С 12.0 10.0 Water resistance 0.85 0.93 Indicators of shear resistance and crack resistance are determined if they are standardized by the design documentation for the construction of asphalt concrete pavement. We calculate the composition of the asphalt concrete mixture for one batch of the mixer. The initial data are the mass of the batch and the dimensions of the screens of the screen of hot materials installed at the ABZ. For ABZ DS, the batch weight is 600 kg, sieves with meshes of 5, 15, 35 mm are installed on the screen. The mass of the material that must come from the hopper for batching is (F1 F2) 600 D i =, 100 B where i is the number of the bunker from which the material is collected for batching; F1 total residue on the underlying sieve in%, taken according to the table. 2; F2 total residue on the overlying sieve in%, taken according to the table. 2; 600 batch weight, kg; B percentage of bitumen in the mixture;

10 (100 48.8) 600 D 0 5 = = 289.8 kg; 100 1.06 (48.8 16.4) 600 D 5 15 = = 183.4 kg 100 1.06 (16.4 0) 600 D = = 92.8 kg, 06; Since the mineral powder is fed through a separate feed line, from the mass of material discharged from the D0-5 hopper, it is necessary to subtract the mass of the mineral powder "289, D 0 5 = = 289.6 39.6 = 250 kg; 100 1.06 Calculation results we enter in table 4. The composition of the asphalt concrete mixture Binder or fractions of stone materials in accordance with Dosage for mixing 600 kg with hot bins ABZ 1 Fraction mm 92.8 2 Fraction 5-15 mm 183.4 3 Fraction 0-5 mm 250.0 4 Mineral powder 39.6 5 Bitumen 34.2 Table 4 We calculate the consumption of asphalt concrete mixture per 1000 m2 of coating and the consumption of constituent materials per 100 tons of the mixture, the results are entered in Table 5. V = HSG = 0.38 = 95.2 tons, where V is the consumption asphalt concrete mix, t; H layer thickness, m; S layer area, equal to 1000 m2; G average density of asphalt concrete, from Table 3, t / m 3. It should be borne in mind that in some cases the customer agrees to pay the contractor irreparable losses, as a rule this is 3% of the volume of asphalt concrete. V "W 100 = P (100 + C),

11 where V is "consumption of inert stone materials, m 3; W is the percentage of this material in the mixture; P is the bulk density of stone materials; C is the percentage of bitumen in the mixture." V 1 = = 28.5 m 1.39 () " V 2 = = 33.0 m 1.46 () Consumption of materials 3 3;; Table 5 Per 100 tonnes of mixture Per 1000 m 2 of coating Name of material Bulk density, t / m 3 Content in the mixture in% T M 3 Crushed stone 1.5 Mozzhukhinsky quarry Sand of Yaysky KSM 1, Mineral powder 7 6.6 Bitumen 6 5.7 Asphalt concrete mixture (t), with a layer thickness of 2 9. REGISTRATION OF MIXTURE RECIPES 9.1 A separate recipe is drawn up for each mixture, which must have an individual number, consisting of from the serial number in the given year and the last two digits of the year for which it was drawn up (for example, 14-00). The serial numbers must correspond to the registration numbers according to the "Journal for determining the physical and mechanical properties of asphalt concrete mixtures during the selection of compositions and periodic quality control of the produced asphalt concrete mixture and "(Form D-7) Prescriptions are drawn up on standard forms, according to the form given in the appendix. All entries must be clear and accurate, strikethrough text, blots are not allowed. The following design options are allowed: using a personal computer; on a letterhead by hand, in black or blue ink (paste). The second and third copies of the recipe may be photocopies. 3 copies of the recipe approved by the chief engineer (technical director) of the organization (indicating the date of approval, surname, initials of the approver, the name of the contractor) are submitted for examination and approval. The signature is certified by a seal.

12 It is forbidden to submit photocopies of recipes where the signature and seal are copied. The organization performing the examination, the customer has the right not to consider recipes issued in violation of the prescription. The prescription indicates the structural element in which the mixture is used (upper, lower coating layer, base), type, type and the brand of the mixture (asphalt concrete), the object, for example: "... for the device of the top layer of the coating (hot, type A, I grade) on the highway" Novosibirsk - Irkutsk ", km 45-60" The recipe should contain: information about the applied mineral materials, grain composition of the mixture (with and without division into constituent materials), binder; production recipe; indicators of the properties of the mixture and asphalt concrete; data on the consumption of materials. The rates of hard-to-remove losses, taken into account in the recipe, should be indicated. For installations of the type DS-117, DS-158, the rate of losses at the ABZ is 1.5%, the rate of losses when laying the mixture is 1.5%. The recipe must be signed by the head of the laboratory that performed the selection. If the selection is made by a third-party organization, the recipe is signed by its technical manager, the signature is certified by a seal. 10. APPROVAL AND APPROVAL OF THE RECIPE The recipe for the asphalt concrete mixture used at the facilities of the Kemerovo DODF State Institution must be approved by the chief engineer (technical director) of the contractor and agreed by the customer's chief engineer (the Kemerovo DODF State Institution). If a contractor purchases a mixture from a third-party organization, it is obliged to ensure that the mixture conforms to the recipe agreed by the State Institution "Kemerovo DODF". Before agreeing on the recipe, the customer must undergo an examination at the Kuzbass Center for Road Research LLC. The examination must be carried out within a period of no more than 5 working days. In the process of examination, the compliance of the recipe with the requirements of SNiP, GOST 9128, the correctness of its design and the calculation of the composition of the mixture are assessed. The compliance of the physicomechanical and other indicators of the mixture specified in the recipe with the actual values ​​is controlled during the technical supervision of the customer.The contractor is responsible for the accuracy of the information provided in the recipe, and the compliance of the mixtures used with the recipes.The customer is obliged to consider the recipe submitted for approval within 5 days. If the recipe has gone through the approval procedure, one copy remains with the customer, one copy is sent to the contractor and the organization exercising independent control. In case of refusal to agree, the customer sends the recipe to the contractor. Refusal must be motivated. After the appropriate adjustment, the prescription again goes through the approval procedure provided for by this standard. Grounds for refusing to approve the prescription: - the prescription has not passed the examination; - non-compliance with the requirements of regulatory documents and (or) the project;

13 - non-compliance with the requirements of this standard. 11. INSPECTION CONTROL OF COMPLIANCE WITH RECIPES OF MIXTURES Inspection control over compliance with recipes for asphalt concrete mixtures is carried out by engineers of the customer's technical supervision service, an independent competent organization (on behalf of the customer), the administration of the organization that produces the mixture or uses it. AGREED Chief Engineer KDODF A.S. Belokobylsky 200 M.P. APPROVED Chief engineer 200 M.P. RECIPE of asphalt concrete mixture for the device (type and type brand) (top / bottom / coating layer, base) on the road from PC (km) to PC (km) Name of material, 1. APPLIED MINERAL MATERIALS Particular residues (number of grains,% by mass remaining on a sieve with mesh size, mm)

14 manufacturer or quarry Name of material, 5 1.25 0.63 0.315 0.14 0.071 less 2. GRAIN COMPOSITION OF ASPHALT CONCRETE MIXTURE 2.1. With division into constituent materials Content Particular residues (number of grains,% by weight, remaining on a sieve with mesh size, mm) in a / b, 5 1.25 0.63 0.315 0.14 0.071 less than the mixture, e% 2.2. Without dividing into constituent materials Particular residues,% Complete residues,% Passages,% Grain composition of the mineral part of the mixture according to GOST,% 3. BINDER,% over 100% of the mineral part 3.1. Bitumen (brand, manufacturer) content in the binder,% 3.2. Modifier (name, brand) content in the binder,% 3.3. Solvent (name, brand,) content in the binder,% Binder or fractions of stone materials in accordance with the hot bins of ABZ 4. COMPOSITION OF ASPHALT CONCRETE MIXTURE Dosage for batching, kg Binder or fractions of stone materials in accordance with hot bins kg Name of indicators 5. INDICATORS OF ASPHALT CONCRETE PROPERTIES According to GOST Actually Name of indicators According to GOST Actually

15 1. Average density, g / cm 3 6. Water resistance at long-term water saturation 2. Porosity of the mineral part,% by volume 3. Water saturation,% by volume 4. Compressive strength (MPa) at: 20 C 50 C 0 C 5 Water resistance 7. Bitumen adhesion with the mineral part of the asphalt mix 8 *. Shear stability index 9 *. Crack resistance index 10. Total specific effective activity of natural radionuclides Test withstands * These indicators are determined if they are standardized by the design documentation for the construction of the pavement 6. CONSUMPTION OF MATERIALS Bulk density, t / m 3 T Content Name of the material in the mixture,% M 3 Per 100 t of the mixture Bq / kg Per 1000 m 2, coatings Asphalt concrete mix (t), with a layer thickness of 4 cm When changing the layer thickness by 0.5 cm, add the Table compiled taking into account the rate of losses% at the ABZ and% when laying the mixture. Head of the SL that performed the selection Agreed by KuzCDI

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