Calculation and preparation of a recipe for a mixture of cold asphalt. An example of selecting the composition of an asphalt concrete mixture. Brands and types of asphalt

Asphalt composition concrete mixture selected according to a specification drawn up on the basis of a highway project. The assignment specifies the type, type and grade of the asphalt concrete mixture, as well as the structural layer of the road pavement for which it is intended. The selection of the composition of an asphalt concrete mixture includes testing and, based on its results, the selection of component materials, and then the establishment of a rational relationship between them, ensuring the production of asphalt concrete with properties that meet the requirements of the standard. Mineral materials and bitumen are tested in accordance with current standards, and after carrying out the entire set of tests, the suitability of the materials for an asphalt concrete mixture of a given type and grade is established, guided by the provisions of GOST. The choice of a rational relationship between the constituent materials begins with the calculation of the grain composition. The mineral part of coarse and fine-grained asphalt concrete mixtures in the presence of coarse or medium sand, as well as crushing screenings, is recommended to be selected according to continuous grain compositions, in the presence of fine natural sand - according to intermittent compositions, where the frame of crushed stone or gravel is filled with a mixture that practically does not contain grains of size 5-0.63 mm.

The mineral part of hot and warm sand and all types of cold asphalt concrete mixtures is selected only according to continuous grain compositions. For the convenience of calculations, it is advisable to use the curves of the maximum values of grain compositions, constructed in accordance with the requirements of GOST (Fig. 1). A mixture of crushed stone (gravel), sand and mineral powder is selected in such a way that the grain composition curve is located in the area limited by the limit curves and is as smooth as possible. When selecting the grain composition of mixtures based on crushed sand and crushed gravel, as well as on materials from rock crushing screenings, which are characterized by a high content of fine grains (finer than 0.071 mm), it is necessary to take into account the amount of the latter in the total content of mineral powder. When using materials from screenings of crushing igneous rocks, complete replacement of mineral powder with their finely dispersed part is allowed in mixtures for dense hot asphalt concrete grades III, as well as in mixtures for porous and highly porous asphalt concrete grades I and II. In mixtures for hot, warm and cold asphalt concrete grades I and II, only partial replacement of mineral powder is allowed; at the same time, the mass of grains finer than 0.071 mm included in the mixture must contain at least 50% limestone mineral powder that meets the requirements of GOST

When using materials from crushing screenings of carbonate rocks in the composition of hot and warm mixtures for dense asphalt concrete grades II and III, as well as cold mixtures of grades I and II and mixtures for porous and highly porous asphalt concrete grades I and II, mineral powder can be omitted if the content grains finer than 0.071 mm in screenings ensure compliance of grain compositions with GOST requirements, and the properties of grains finer than 0.315 mm in screenings meet GOST requirements for mineral powder. Rice. Continuous grain compositions of the mineral part of hot and warm fine-grained (a) and sand (b) mixtures for dense asphalt concrete used in the upper layers of pavements.

When using polymineral gravel crushing products in asphalt concrete in road-climatic zones IV-V, it is also allowed not to introduce mineral powder into asphalt concrete mixtures of grade II if the mass of grains finer than 0.071 mm contains at least 40% calcium and magnesium carbonates (CaCO3 + MgCO3). As a result of selecting the grain composition, the percentage ratio by weight between the mineral components of asphalt concrete is established: crushed stone (gravel), sand and mineral powder. The bitumen content in the mixture is pre-selected in accordance with the recommendations of Appendix 1 of GOST and taking into account the standard requirements for the residual porosity of asphalt concrete for a specific climatic region. Thus, in road climatic zones IV-V, the use of asphalt concrete with higher residual porosity than in I-II is allowed, therefore the bitumen content in asphalt concrete for these zones is prescribed closer to the lower recommended limits, and in I-II - to the upper.

In the laboratory, three samples are prepared from an asphalt concrete mixture with a pre-selected amount of bitumen and the following are determined: the average density of asphalt concrete, the average and true density of the mineral part, the porosity of the mineral part and the residual porosity of asphalt concrete according to GOST. If the residual porosity does not correspond to the selected one, then the required content is calculated from the obtained characteristics bitumen B (%) according to the formula: B where V°pop is the porosity of the mineral part, % volume; Vpor - selected residual porosity, % volume, is accepted in accordance with GOST for a given road-climatic zone; gb - true density of bitumen, g/cm 3; gb = 1 g/cm 3; r°m - average density of the mineral part, g/cm3.

Having calculated the required amount of bitumen, the mixture is prepared again, three samples are formed from it and the residual porosity of the asphalt concrete is determined. If the residual porosity coincides with the selected one, then the calculated amount of bitumen is accepted. An asphalt concrete mixture of selected composition is prepared in the laboratory: coarse-grained kg, fine-grained kg and sand mixture kg. Samples are made from the mixture and their compliance with the physical mechanical properties GOST If asphalt concrete of the selected composition does not meet the standard requirements for some indicators, for example, strength at 50 ° C, then it is recommended to increase (within acceptable limits) the content of mineral powder or use more viscous bitumen; if strength values at 0°C are unsatisfactory, the content of mineral powder should be reduced, the viscosity of bitumen should be reduced, or a polymer additive should be added.

If the water resistance of asphalt concrete is insufficient, it is advisable to increase the content of either mineral powder or bitumen; however, the residual porosity and the porosity of the mineral matrix must remain within the limits provided for by the above-mentioned standard. To increase water resistance, surfactants and activated mineral powders are most effective. When assigning bitumen content to cold asphalt concrete mixtures, additional measures should be taken to ensure that the mixture does not caking during storage. To do this, after determining the required amount of bitumen, samples are prepared for caking testing. If the caking indicator exceeds the GOST requirements, then the bitumen content is reduced by 0.5% and the test is repeated. The amount of bitumen should be reduced until satisfactory caking results are obtained, however, it is necessary to ensure that the residual porosity of cold asphalt concrete does not exceed the requirements of GOST. After adjusting the composition of the asphalt concrete mixture, the selected mixture should be tested again. The selection of the composition of the asphalt concrete mixture can be considered complete if all indicators of the properties of asphalt concrete samples meet the requirements of the above-mentioned GOST.

An example of selecting the composition of an asphalt concrete mixture. It is necessary to select the composition of a fine-grained hot asphalt concrete mixture of type B, grade II, for dense asphalt concrete intended for the installation of a top layer of pavement in the III road climate zone. The following materials are available: - crushed granite stone fraction 5-20 mm; - crushed limestone fraction 5-20 mm; - river sand; - material from granite crushing screenings; - material from limestone crushing screenings; - non-activated mineral powder; - oil grade bitumen BND 90/130 (according to the passport). The characteristics of the tested materials are given below. Crushed granite: grade for strength when crushed in a cylinder, grade for wear - I-I, grade for frost resistance - Mrz 25, true density - 2.70 g/cm 3; crushed limestone: grade for strength when crushed in a cylinder - 400, grade for wear - I-IV, grade for frost resistance - Mrz 15, true density - 2.76 g/cm 3; river sand: content of dust and clay particles - 1.8%, clay - 0.2% of mass, true density - 2.68 g/cm 3; material from granite crushing screenings grade 1000:

The content of dust and clay particles is 5%, clay is 0.4% of the mass, the true density is 2.70 g/cm 3; material from screenings of crushing limestone grade 400: content of dust and clay particles - 12%, clay - 0.5% of mass, true density - 2.76 g/cm 3; non-activated mineral powder: porosity - 33% of the volume, swelling of samples from a mixture of powder with bitumen - 2% of the volume, true density - 2.74 g/cm 3, bitumen capacity - 59 g, humidity - 0.3% of the mass; bitumen: needle penetration depth at 25°C - 94×0.1 mm, at 0°C - 31×0.1 mm, softening temperature - 45°C, elongation at 25°C - 80 cm, at 0°C - 6 cm, Fraas brittleness temperature - minus 18°C, flash point - 240°C, withstands adhesion to the mineral part of the asphalt concrete mixture, penetration index - minus 1. According to test results, crushed granite stone can be considered suitable for preparing mixtures of type B, grade II, river sand, material from granite crushing screenings, mineral powder and bitumen grade BND 90/130.

Crushed limestone and material from limestone crushing screenings do not meet the requirements of Table. 10 and 11 GOST for strength indicators. The grain compositions of the selected mineral materials are given in Table. Calculation of the composition of the mineral part of the asphalt concrete mixture begins with determining such a ratio of the masses of crushed stone, sand and mineral powder at which the grain composition of the mixture of these materials satisfies the requirements of Table. 6 GOST Table

Calculation of the amount of crushed stone In accordance with GOST and Fig. 2, and the content of crushed stone particles larger than 5 mm in type B asphalt concrete mixture is 35-50%. For this case We accept the crushed stone content Sh = 48%. Since crushed stone contains 95% of grains larger than 5 mm, crushed stone will be required = The resulting value is entered in the table. 7 and calculate the content of each fraction in the crushed stone mixture (take 50% of the amount of each crushed stone fraction). Calculation of the amount of mineral powder In accordance with GOST and Fig. 2, and the content of particles finer than 0.071 mm in the mineral part of the asphalt concrete mixture of type B should be in the range of 6-12%. For calculation, we take the particle content, for example, closer to the lower limit of the requirements, i.e. 7%. If the number of these particles in the mineral powder is 74%, then the content of the mineral powder in the MP mixture =

However, for our conditions, 8% mineral powder should be taken, since sand and material from granite crushing screenings already contain a small amount of particles smaller than 0.071 mm. The data obtained are entered into Table 7 and the content of mineral powder of each fraction is calculated (take 8%). Calculation of the amount of sand The amount of sand P in the mixture will be: P = 100 - (Sh + MP) = (50 + 8) = 42% Since in this example two types of sand were used (river and materials from granite crushing screenings), it is necessary to determine the amount each of them separately. The relationship between river sand Pr and material from granite crushing screenings can be established by the content of grains finer than 1.25 mm, which, according to GOST and Fig. 2, and in type B asphalt concrete mixture it should be 28-39%. We accept 34%; of which 8%, as calculated above, is the share of mineral powder. Then the share of sand remains 34-8 = 26% of grains finer than 1.25 mm. Considering that the mass fraction of such grains in river sand is 73%, and in the material from granite crushing screenings - 49%, we draw up a proportion to determine the mass fraction of river sand in the mineral part of the asphalt concrete mixture:

For calculation we take Pr = 22%; then the amount of material from granite crushing screenings will be = 20%. Having calculated, similarly to crushed stone and mineral powder, the amount of each fraction in sand and material from granite crushing screenings, we record the obtained data in table. 7. By summing up the number of particles smaller than a given size in each vertical column, we obtain the overall grain composition of the mixture of mineral materials. Comparison of the resulting composition with the requirements of GOST shows that it satisfies them. Similarly, we calculate the mineral part of an asphalt concrete mixture of discontinuous grain composition. Determination of bitumen content Crushed stone, sand, material from granite crushing screenings and mineral powder are mixed with 6% bitumen. This amount of bitumen is the average value recommended in adj. 1. GOST for all road climatic zones. Three samples with a diameter and height of 71.4 mm are prepared from the resulting mixture.

Since the asphalt concrete mixture contains 50% crushed stone, the mixture is compacted using a combined method: vibrating on a vibrating platform for 3 minutes under a load of 0.03 MPa (0.3 kgf/cm 2) and additional compaction on a press for 3 minutes under a load of 20 MPa (200 kgf/cm 2). After an hour, the average density (volumetric mass) of asphalt concrete (samples) and the true density of the mineral part of asphalt concrete r° are determined and, based on these data, the average density and porosity of the mineral part of the samples are calculated. Knowing the true density of all materials and choosing the residual porosity of asphalt concrete Vpor = 4% according to GOST, the approximate amount of bitumen is calculated. The average density of test asphalt concrete samples with a bitumen content of 6.0% (over 100% of the mineral part) is 2.35 g/cm3. In this case

G/cm 3 ; Three samples are made from a control mixture with 6.2% bitumen and the residual porosity is determined. If it is within 4.0 ± 0.5% (as was customary for fine-grained asphalt concrete from type B mixtures), then a new mixture is prepared with the same amount of bitumen, 15 samples are formed and tested in accordance with GOST requirements (three sample for each type of test). If the properties of samples prepared from the selected mixture deviate from GOST requirements, then it is necessary to adjust the composition of the mixture and test it again.

The grain compositions of the mineral part of mixtures and asphalt concretes must correspond to those indicated in the table. Indicators of the physical and mechanical properties of asphalt concrete used in specific road and climatic zones must correspond to those indicated in the table.

Components, formulation and properties The suitability of a powder for use in cast asphalt concrete can be objectively assessed only by testing the asphalt concrete samples produced with it. Taking into account this important circumstance makes it possible to use in some types of cast asphalt concrete even such powders that are of little use at first glance, such as loess powder, ground marl, gypsum stone or gypsum, filter press waste from the sugar industry, waste from soda factories, ferrochrome slag, etc. Sand plays important technological and economic role in the production of cast asphalt concrete mixtures. When choosing sand, preference is given to natural sand. The denser and larger the grain, the more mobile and dense the mineral mixture and the less bitumen it requires. Unlike mineral powder, most natural sea, river and lake quartz sands in chemical reaction does not interact with bitumen. For most cast mixtures, we can recommend sands that meet the requirements of the standard and table.

Components, formulation and properties For mixtures of types I and II, the use of crushing screenings containing an increased amount of dust particles is not recommended in order to avoid deterioration in the mobility of the mixtures and an increase in bitumen consumption. It is advisable to use crushed sand only as an additive to natural rounded sand in the preparation of mixtures of types I and II. V pure form they can only be used in mixtures of types III, IV and V. Almost all properties of cast asphalt concrete are significantly improved when a 3-5 mm fraction of hard-to-polish rocks is added to the mixture. The ratio of the 3-5 mm fraction and the 5-10 fraction in the mixture should be taken as 2:1 or 1.5:1. Crushed stone (gravel) for crushed stone (gravel) cast mixtures must meet the requirements and table. 3. It is not recommended to use crushed stone obtained by crushing weak (breakability grade below 600) and porous rocks. Porous crushed stone quickly absorbs bitumen, and to ensure the necessary mobility of the mixture, the bitumen content must be increased.

Components, formulation and properties In mixtures for the top layer, it is necessary to use crushed stone from dense and difficult to polish rocks, cubic in shape with a maximum size of up to 15 (20) mm. Moreover, for mixtures of type I crushed stone, fractions of 3-15 with a grain ratio of 3-5, 5-10 and mm in size as 2.5: 1.5: 1.0 are recommended. For V type mixtures maximum size grains can reach 20 mm, and for III - 40 mm. In the latter case, the strength of the original rock can be reduced by %.

Components, formulation and properties Without much damage to asphalt concrete from mixtures of types II, III and V, but with great benefits for production, the requirement for crushability of crushed stone grains can be reduced. Crushing of grains in these asphalt concrete mixtures is unlikely, since the formation of the structure into a monolith occurs under the influence of gravity or vibration and without the participation of heavy rollers. In cast mixtures of type II, III and V, gravel can be successfully used. Due to the rounded shape and ultra-acidic nature of the surface of the grains, the mixture has increased mobility with less bitumen consumption. Bitumen determines the phase composition of the asphalt binder in asphalt concrete, is subject to the greatest changes compared to other components of the mixture and affects the heat resistance of the coating. Therefore, they focus mainly on viscous grades having the properties indicated in table. 4.

Components, formulation and properties If bitumen does not have the complex of specified properties, it is improved by adding natural bitumen, bituminous rocks, elastomers, etc. Very effective additives include natural bitumen, which are well compatible with petroleum bitumen and are easy to use. Natural bitumens were formed from oil in the upper layers earth's crust as a result of the loss of light and medium fractions - natural deasphalting of oil, as well as the processes of interaction of its components with oxygen or sulfur. On the territory of our country, natural bitumen is found in various bituminous rocks and is rarely found in its pure form. Components, formulation and properties Bitumen deposits occur in the form of layers, lenses, veins and on the surface. The largest amount of bitumen is contained in reservoir and lens deposits. Vein deposits are rare in our country. A significant amount of natural bitumen is found in surface deposits. In my own way chemical composition these bitumens are similar to petroleum ones. Natural bitumens are hard, viscous and liquid. Hard bitumen (asphaltite). Density of asphaltites kg/m3, softening temperature °C. On average, asphaltite contains 25% oils, 20% resins and 55% asphaltenes. Asphaltites have increased adhesive properties due to the high content of natural surfactants in their composition - asphaltogenic acids and their anhydrides. Asphaltites are resistant to aging when exposed to solar radiation and air oxygen.

Components, formulation and properties Positive results were obtained by introducing crushed polyethylene into the cast mixture, as well as finely ground rubber powder (TIRP) in an amount of 1.5% by weight of mineral materials. As an additive that increases the heat resistance of cast asphalt concrete, it is recommended to use degassed sulfur in lump, granular (granule size up to 6 mm) or liquid form. Sulfur is introduced into the mixer on hot mineral materials, i.e. before feeding bitumen. The amount of sulfur is prescribed within 0.25-0.65 of the bitumen content. In this case, the amount of bitumen with sulfur is 0.4-0.6 of the content of mineral powder.

Components, formulation and properties To summarize the above, you need to keep in mind that most of the listed “know-how” require overcoming serious technical and technological problems, as well as additional financial costs, which not all organizations can solve. By increasing production costs, they do not always contribute to improving the technological properties of mixtures and performance characteristics coatings, as well as human health and the environment. It is recommended to select the mixture recipe using a special technique. The calculation of the component content begins after determining the grain (granulometric) composition of all mineral materials and constructing a sieving curve. The curve must fit within the recommended limits for a particular type of mixture 53 Components, formulation and properties If the sieving curve does not fit within the recommended limits, adjust the content of individual grains by changing their quantity in the mineral mixture. When calculating the amount of mineral powder, it is necessary to make an adjustment for the content of dust from sand and crushed stone in the mineral mixture. Further, guided by numerical values phase composition of the asphalt binder (B/MP) and its quantity (B+MP) for the corresponding type of cast mixture, a dose of bitumen (polymer bitumen or other bitumen binder) is introduced and the property indicators are determined. The main indicators of the properties of cast mixture and asphalt concrete samples, for the given values of which the composition is selected, are for types: I and V - mobility, depth of stamp indentation and water saturation; II - mobility, compressive strength at +50 °C and depth of indentation of the stamp; III - mobility and water saturation; IV - water saturation and compressive strength at +50 °C.

Components, formulation and properties The tensile strength in bending and the elastic modulus at 0 °C are optionally determined, as well as the crack resistance coefficient as the ratio of the values of these indicators. If the properties of the mixture and asphalt concrete fully comply with the required ones (table), the selection is considered successful. Table - Physical and mechanical properties of cast asphalt concrete

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1 System of regulatory documents in construction ENTERPRISE STANDARD The procedure for selecting and approving recipes for asphalt concrete mixtures STP Directorate of the Kemerovo Regional Road Fund PREFACE

2 1. DESIGNED TO stand alone non-profit organization“Kuzbassdorcertification” (candidate of technical sciences, associate professor O.P. Afinogenov, engineer V.B. Sadkov). 2. INTRODUCED by the Autonomous Non-Profit Organization “Kuzbassdorcertification”. 3. APPROVED and put into effect Government agency"Kemerovo Directorate of the Regional Road Fund." 4. INTRODUCED FOR THE FIRST TIME. State Institution "Kemerovo dir. regional road fund", 2000 Enterprise standard The procedure for selecting and approving 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 work under contracts with the State Institution “Kemerovo Directorate of the Regional Road Fund” (hereinafter referred to as the customer, the State Institution “Kemerovo DODF”). 2. REGULATORY REFERENCES This standard uses references to the following regulatory documents: SNiP System of regulatory documents in construction. Basic provisions; SNiP Highways; SNiP *. Organization construction production; GOST Testing and quality control of products. Basic terms and definitions; GOST Mixtures of asphalt concrete for road, airfield and asphalt concrete; GOST Materials based on organic binders for road and airfield construction. Test methods; STP Preparation of road bitumens modified with atactic polypropylene. Model regulations; TU Road bitumens modified with atactic polypropylene. 3. DEFINITIONS 3.1. This standard uses terms and their definitions corresponding to GOST 9128, GOST 16504, SNiP, SNiP Asphalt concrete mixture is a rationally selected mixture of mineral materials (crushed stone [gravel] and sand with or without mineral powder) with bitumen, taken in certain proportions and mixed in heated state. Asphalt concrete is a compacted asphalt concrete mixture. An asphalt concrete mixture recipe is a document that is part of the technological regulations, containing information characterizing the scope of application of the mixture, its composition and physical and mechanical properties, material consumption; approved and agreed upon in the prescribed manner. 4. GENERAL PROVISIONS

4 4.1. The Contractor does not have the right to carry out work using asphalt concrete mixtures at the facilities of the Kemerovo DODF State Institution without recipes for their production, agreed upon in the manner regulated by this standard. The recipe is drawn up for the construction season, for each mixture used at this facility. It is allowed to issue one recipe for several objects of the same type. In case of adjustment of the recipe based on the results of production control, when replacing materials, etc., the recipe is subject to re-approval in the manner prescribed in 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 must be carried out by an organization that has a competent laboratory and guarantees the reliability of test results and the completeness of the controlled signs (characteristics) of the asphalt concrete mixture. A laboratory accredited for the relevant types of tests in a registered and (or ) duly recognized by the laboratory accreditation system, or having a certificate of official assessment of the state of measurements according to MI. The recipe for an asphalt concrete mixture is compiled on the basis of a specially made selection, the purpose of which is to provide the mixture with the specified properties. The selection (design) of the mixture consists of five stages: 1) establishing requirements to the mixture; 2) selection of materials and assessment of their suitability; 3) determination of a rational quantitative ratio of mixture components; 4) quality control of the composition; 5) economic assessment of the quality of the composition. The task for designing an asphalt concrete mixture is issued by the chief engineer of the contracting organization. The mixture can be selected by the contractor's road construction laboratory or an external laboratory. The assignment for designing the mixture must indicate: the type of asphalt concrete mixture (hot, cold, coarse-grained, fine-grained, sand); type of asphalt concrete (high-density, dense, porous, highly porous); type of mixture and brand of asphalt concrete; Desirable materials When designing asphalt concrete mixtures, the most economical composition should be sought. 5. DESIGNATION OF THE MAIN PARAMETERS OF THE MIXTURE 5.1. The main parameters and type of mixture (asphalt concrete) are assigned according to the design documentation. If deviations from the requirements of the regulatory documents in force at the time of selection of the mixture are found, it is necessary to agree on the parameters with the customer. Asphalt concrete mixtures must

5 apply in accordance with p SNiP, adj. A GOST and meet the requirements of GOST The customer has the right to establish higher rates of asphalt concrete mixture (asphalt concrete) than provided for by SNiP (with appropriate compensation for the contractor’s costs). For the installation of the bottom layer of coating, leveling layers, predominantly coarse-grained mixtures with a rough surface should be used (to ensure reliable grip with top layer) and high shear resistance highways with heavy traffic, hot, high-density mixtures of type A should be used. To repair minor damage to asphalt concrete pavements, mixtures are used that are similar in properties to the mixtures of the coating layer being repaired. 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, which have better adhesion to petroleum bitumen. The shape of the crushed stone should be close to a cube and not have flat flaky grains. Gravel is a less desirable component as it has smooth surface, inclusions of weak rocks. Increasing the amount of crushed stone increases the crack resistance and shear resistance of coatings. It is advisable to use sand consisting of particles different sizes. Uniform sand increases the porosity of the mineral part. Sand from crushing screenings increases the internal friction of the mineral part due to the content of acute-angled grains in it. River sand is not recommended for use. Mineral powders obtained by artificial grinding of limestone and dolomite should be used for asphalt concrete mixtures. The presence of very fine clay particles in the mineral powder increases the swelling of asphalt concrete when moistened 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 laying the mixture. The properties of the binder largely determine the quality of asphalt concrete. Excessive viscosity of bitumen leads to the formation of cracks at low temperatures, and low viscosity leads 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 bitumens). For modification, polymer-bitumen binders of the PBB and Kaudest-D brands are used, bitumen-rubber binders of the BKV brands; it is allowed to use atactic polypropylene of the APP-G/B brand on territorial roads (the binder must meet the requirements of the Technical Specifications for Preparation of Bitumen,

6 modified with atactic polypropylene, carried out using FSW. Polymer additives increase the elasticity of bitumen, its thermal stability over a wide temperature range, the 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 the more complete enveloping of stone materials with a bitumen film and filling of pores, and the 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. Design of the composition of an asphalt concrete mixture (asphalt concrete) can be carried out according to any known method. It is recommended to use the SoyuzdorNII method, which GOST is focused on. The basis of the method is 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. In the conditions of the Kemerovo region, it is advisable to strive for the use of a smaller amount of sand and mineral powder, which have a higher moisture capacity, i.e. .e. use mixtures of types A and B Calculation of asphalt concrete includes two stages: calculation of the granulometric (grain) composition of the mineral part of the mixture from a given set of materials according to the granulometric composition tables (Tables 2 and 3 GOST); experimental determination of the physical and mechanical properties 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 bitumen contents. The criterion for determining the optimal amount of bitumen is the best correspondence between water saturation and mechanical compressive strength at temperature 20 C and 50 C test samples that meet the requirements of GOST EXAMPLE OF CALCULATION OF THE COMPOSITION OF A FINE-GRAIN MIXTURE 8.1. Task: Calculate the composition of fine-grained hot asphalt concrete type B, grade II. Components: Crushed stone from the Mozzhukhinsky quarry, fractions 5-20 mm; Sand from the Yaya plant building materials;

7 Limestone mineral powder. Calculation procedure. Based on the limits of the required particle size distributions (Table 3 GOST) and based on the results of sifting the mineral materials used (Table 1), we determine the approximate percentage content of each material (crushed stone, sand, mineral powder). Table 1 Name of material, manufacturer or quarry Partial residues (number of grains, % by weight, less remaining on a sieve with mesh size, mm) .5 1.25 0.63 0.315 0.14 0.071 less Mozzhukhinsky quarry crushed stone, fr mm Yaisky 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 Crushed stone content 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 fraction content larger than 5 mm in crushed stone. Mineral powder content a1 6 Z = 100 = 100 = 8.4% b 71.6 1 where a1 is the minimum permissible content of the fraction “less than 0.071 mm” in the composition of type B asphalt concrete (Table 3 GOST); b1 content of fractions finer than 0.071 mm in mineral powder. Taking into account the presence of grains in the sand with a particle size of more than 5 mm and finer than 0.071 mm, we reduce the above values of the content of crushed stone and mineral powder in the mixture to the following values: crushed stone 42.0%, mineral powder 7.0%. Then the sand content in the mixture Fill out 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 designed mineral mixture Size of the sieve openings in mm Particle size distribution of the constituent materials in % crushed stone sand mineral powder Particle size distribution of materials in the designed mixture in % crushed sand mineral powder Partial residues of the designed mineral mixture in % Total residues of the designed mineral mixture in % Full passes Permissible 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, We determine the percentage of bitumen in accordance with the recommendations of GOST Appendix G, it is 5.0-6.5%. Based on this, we prepare three asphalt concrete mixtures with the same mineral composition and the calculated amount of bitumen (5.0-5.8-6.5%). Test samples are made from these compositions and tested for compression at temperatures of +20 and +50 C and for water saturation. The optimal amount of bitumen is taken to be the content at which the best performance of asphalt concrete was achieved. We produce control samples of the designed composition with the optimal amount of bitumen and subject them to full cycle tests. The test results are recorded in Table 3. Table 3 Indicators of asphalt concrete properties

9 Name of indicator GOST Requirements Actual indicators Name of indicator 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 Passes Passes C 2 .2 2.6 50 C 1.0 1.1 0 C 12.0 10.0 Water resistance 0.85 0.93 Indicators of shear resistance and crack resistance are determined if they are standardized project documentation for construction asphalt concrete pavement. We calculate the composition of the asphalt concrete mixture for one mixer batch. The initial data are the mass of the batch and the mesh sizes of the screens of the hot materials screen installed at the asphalt plant. For ABZ DS, the mass of the batch is 600 kg; sieves with cells of 5, 15, 35 mm are installed on the screen. The mass of material that must come from the hopper for batching is equal to (F1 F2) 600 D i =, 100 B where i is the number of the hopper from which material is collected for batching; F1 is the total residue on the underlying sieve in %, taken according to the data in table. 2; F2 is the total residue on the overlying sieve in %, taken according to the data in 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 mineral powder is supplied through a separate supply line, it is necessary to subtract the mass of mineral powder from the mass of material shipped from bunker D0-5 "289, D 0 5 = = 289.6 39.6 = 250 kg; 100 1.06 Calculation results enter in table 4. Composition of the asphalt concrete mixture Binder or fractions of stone materials in accordance with Dosage per batch 600 kg 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 pavement and the consumption of constituent materials per 100 tons of mixture, the results are entered in Table 5. V = H S G = 0.38 = 95.2 t, where V consumption asphalt concrete mixture, 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 must be taken into account that in some cases the customer agrees to pay the contractor for irreparable losses, as a rule this is 3% of the volume of asphalt concrete. V "W 100 = P (100 + C),

11 where V" consumption of inert stone materials, m 3; W percentage of this material in the mixture; P volumetric bulk mass of stone materials; C percentage of bitumen in the mixture. "V 1 = = 28.5 m 1.39 () " V 2 = = 33.0 m 1.46 () Material consumption 3 3 ; ; Table 5 Per 100 tm 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 Yaisky KSM 1, Mineral powder 7 6.6 Bitumen 6 5.7 Asphalt concrete mixture (t), with a layer thickness of 2 9. DESIGN OF RECIPES MIXTURES 9.1. A separate recipe is compiled for each mixture, which must have an individual number, consisting of a serial number in a given year and the last two digits of the year for which it was compiled (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” (form D-7). Recipes are drawn up on standard forms, according to the form given in the appendix. All entries must be clear and neat; crossing out text and blots are not allowed. The following design options are allowed: using a personal computer; on a form by hand, with ink (paste) black or of blue color. The second and third copies of the recipe may be photocopies. Three copies of the recipe approved by the chief engineer are submitted for examination and approval ( technical director) organization (indicating the date of approval, surname, initials of the approver, name of the contractor. The signature is certified by a seal.

12 It is prohibited to submit photocopies of recipes where the signature and seal have been copied. The organization performing the examination and the customer have the right not to consider recipes drawn up in violation of p. The recipe indicates the structural element in which the mixture is used (top, bottom layer of coating, base), type, type and brand of mixture (asphalt concrete), object, for example: "... for the installation of a top layer of coating (hot, type A, grade I) on the Novosibirsk - Irkutsk highway, km 45-60" The recipe must contain: information about the materials used mineral materials, grain composition of the mixture (with and without division into component materials), binder; production recipe; indicators of properties of the mixture and asphalt concrete; data on material consumption. The norms for hard-to-remove losses taken into account in the recipe must be indicated. For installations of type DS-117, DS-158, the loss rate at the asphalt plant is 1.5%, the loss rate 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 director, and the signature is certified by a seal. 10. APPROVAL AND AGREEMENT 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 contracting organization and agreed upon by the chief engineer of the customer (Kemerovo DODF State Institution). If a contracting organization purchases a mixture from a third-party organization, it is obliged to ensure that the mixture complies with the recipe agreed upon by the Kemerovo DODF State Institution. Before the recipe is approved by the customer, it must undergo an examination at Kuzbass Road Research Center LLC. The examination must be carried out within no more than 5 working days. During the examination, the compliance of the recipe with the requirements of SNiP, GOST 9128, the correctness of its design and calculation of the composition of the mixture are assessed. The compliance of the physical-mechanical and other indicators of the mixture specified in the recipe with the actual values is monitored during the technical supervision of the customer. The Contractor is responsible for the accuracy of the information presented in the recipe and the compliance of the mixtures used with the recipes. The customer is obliged to review 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 each is sent to the contractor and the organization exercising independent control. If approval is refused, the customer sends the recipe to the contractor. The refusal must be motivated. After appropriate adjustment, the recipe again goes through the approval procedure provided for by this standard. Grounds for refusal to approve a recipe: - the recipe 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 OVER COMPLIANCE WITH MIXTURE RECIPES Inspection control over compliance with asphalt concrete mixture recipes is carried out by engineers of the customer's technical supervision service, an independent competent organization (on behalf of the customer), and the administration of the organization that produces the mixture or uses it. AGREED Chief Engineer KDODF A.S. Belokobylsky 200 M.P. I APPROVED Chief Engineer 200 M.P. RECIPE for asphalt concrete mixture for installation (type and brand type) (top/bottom/layer of coating, base) on a highway from PC (km) to PC (km) Name of material, 1. APPLIED MINERAL MATERIALS Partial 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 than 2. GRAIN COMPOSITION OF ASPHALT CONCRETE MIXTURE 2.1. Divided into component materials Contents Partial 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 mixture, e % 2.2. Without dividing into component materials Partial residues, % Total residues, % Passes, % Grain composition of the mineral part of the mixture according to GOST, % 3. BINDER, % in excess of 100% of the mineral part 3.1. Bitumen (brand, manufacturer) content in binder, % 3.2. Modifier (name, brand) content in binder, % 3.3. Solvent (name, brand,) content in the binder, % Binder or fractions of stone materials in accordance with the hot bunkers of the asphalt concrete plant 4. COMPOSITION OF ASPHALT CONCRETE MIXTURE Dosage per batch weighing, kg Binder or fractions of stone materials in accordance with the hot bunkers of the asphalt concrete plant Dosage per batch weighing, kg Name of indicators 5. INDICATORS OF ASPHALT CONCRETE PROPERTIES According to GOST Actually Name of indicators According to GOST Actually

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GOST 9128-2013 INTERSTATE STANDARD FOR ASPHALT CONCRETE MIXTURES, POLYMERSAPHALT CONCRETE, ASPHALT CONCRETE, POLYMERSAPHALT CONCRETE FOR HIGHWAYS AND AIRDROMES Technical specifications Asphaltic concrete

The calculation consists of selecting a rational ratio between the materials that make up the asphalt concrete mixture.

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

Between grain composition mineral material and density there is a direct relationship. The optimal compositions will be those containing grains of various sizes, the diameters of which are halved.

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

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

Grain sizes according to previous level

(6.6.2)

The number of sizes is determined by the formula

(6.6.3)

Number of factions P per unit less number sizes T

(6.6.4)

Ratio of adjacent fractions by mass

(6.6.5)

Where TO- escape coefficient.

The value showing how many times the amount of the subsequent fraction is less than the previous one is called the escape coefficient. The most dense mixture is obtained with a runoff coefficient of 0.8, but such a mixture is difficult to select, therefore, according to the suggestion of N.N. Ivanova, escape coefficient TO accepted from 0.7 to 0.9.

Knowing the size of the fractions, their number and the accepted runoff coefficient (for example, 0.7), equations of the following form are drawn up:

The sum of all fractions (by weight) is equal to 100%, that is:

at 1 + at 1 To + at 1 To 2 + at 1 To 3 +...+ at 1 To n -1 = 100 (6.6.6)

at 1 (1 + To + To 2 + To 3 +... + To n -1) = 100 (6.6.7)

The sum of the geometric progression and, therefore, the amount of the first fraction in the mixture is indicated in parentheses

(6.6.8)

Similarly, we determine the percentage of the first fraction at 1, for the runoff coefficient To= 0.9. Knowing the amount of the first fraction at 1, easy to identify at 2 , at 3 and so on.

Based on the data obtained, limit curves are constructed that correspond to the accepted runoff coefficients. Compositions calculated using a runoff coefficient of 0.9 contain an increased amount of mineral powder, and when To < 0,7 - уменьшенное количество минерального порошка.

The grain composition curve of the mixture being calculated should be located between the limit curves (Fig. 6.6.1).

Rice. 6.6.1. Grain compositions:
A - fine-grained asphalt concrete mixture with continuous granulometry of types A, B, C; B - mineral part of sand mixtures of types D and D

High performance indicators are achieved by mixtures with a high content of crushed stone and a reduced content of mineral powder. Preference should be given to mixtures with a runoff coefficient of 0.70...0.80.

If it is impossible to calculate a dense mineral mixture using limit curves (the absence of coarse-grained sands and the impossibility of replacing them with seed), the required density can be selected according to the principle of intermittent granulometry. Mixtures with discontinuous granulometry are more resistant to shear due to their rigid frame.

To determine the bitumen consumption, test samples are formed from a mixture with a known low bitumen content, then the volume of voids in the mineral core is determined

(6.6.9)

Where g- volumetric mass of the asphalt concrete sample;

B pr- bitumen content in the test mixture, %;

r m- average density of mineral material:

(6.6.10)

Where y,y n , at mp- content of crushed stone, sand, mineral powder in % by weight;

r,r p , r mp- density of crushed stone, sand, mineral powder.

Calculation formula to determine the optimal bitumen content will have the form

(6.6.11)

Where r b- bitumen density;

j- coefficient of filling voids of the mineral mixture with bitumen, depending on the specified residual porosity

Where By- porosity of the mineral core of asphalt concrete, % volume;

P- specified residual porosity of asphalt concrete at 20°C, % volume.

Cold asphalt concrete

The composition of cold asphalt concrete can be calculated by standard compositions or according to the methodology used for calculating hot mixtures, with mandatory testing of physical and mechanical properties in the laboratory. The amount of liquid bitumen is reduced by 10...15% against the optimum in order to reduce caking.

A characteristic feature of cold asphalt concrete, which distinguishes it from hot asphalt, is the ability to remain in a loose state for a long time after preparation. This ability of cold asphalt concrete mixtures is explained by the presence of a thin bitumen film on mineral grains, as a result of which the microstructural bonds in the mixture are so weak that a small force leads to their destruction. Therefore, the prepared mixtures do not cake under the influence of their own weight during storage in stacks and transportation. The mixtures remain in a loose state for a long time (up to 12 months). They can be relatively easily loaded into vehicles and distributed in a thin layer when constructing road surfaces.

The grain compositions of cold asphalt concrete mixtures differ from the compositions of hot mixtures in the direction of a higher content of mineral powder (up to 20%) - particles smaller than 0.071 mm and a reduced content of crushed stone (up to 50%). An increased amount of mineral powder is caused by the use of liquid bitumen, which requires more powder, and when the crushed stone content is more than 50%, the conditions for coating formation worsen. The largest grain size in cold asphalt concrete is 20 mm. Larger crushed stone worsens the conditions for coating formation.

Crushed stone obtained by crushing rocks and metallurgical slag is used as a large component for cold asphalt concrete. These materials must have a compressive strength of at least 80 MPa, and for grade II asphalt concrete - at least 60 MPa.

To prepare cold asphalt concrete, the same mineral powder and sand are used as for hot mixes.

Liquid bitumens must have a viscosity within which corresponds to the brands SG 70/130, MG 70/130. The viscosity and class of bitumen are selected taking into account the expected shelf life of the mixture in warehouses, air temperature during storage and use, as well as the quality of mineral materials. Cold asphalt concrete mixtures are used to construct road surfaces with traffic intensity of up to 2000 cars per day.

Cast asphalt concrete

Cast asphalt concrete is a specially engineered mixture of crushed stone, sand, mineral powder and viscous bitumen, prepared and placed while hot without additional compaction. Cast asphalt concrete differs from hot asphalt concrete in its higher content of mineral powder and bitumen, preparation technology and laying method. Cast asphalt concrete is used as a road surface on highways, on the roadway of bridges, as well as for constructing floors in industrial buildings. Repair work using cast mixtures can be performed at air temperatures down to -10°C. A special feature of the work is the need for continuous mixing of the cast mixture during its transportation to the installation site.

To prepare cast asphalt concrete, crushed stone (up to 40 mm in size), natural or crushed sand is used. Crushed stone, seedings and sand must be high-grade, as for conventional hot-melt asphalt concrete. BND 40/60 bitumen is used as a binder. In accordance with TU 400-24-158-89, cast mixtures are divided into five types (Table 6.6.11).

Table 6.6.11

Classification of cast asphalt concrete mixtures

TO positive properties Cast asphalt concrete features include durability, low compaction costs, and water resistance. When reconstructing a road, the existing mastic asphalt pavement can be reused to in full and almost no new materials added.

Tar concrete

Depending on the viscosity of the tar and the temperature of the mixtures during laying, tar concrete is divided into hot and cold. By physical and mechanical properties tar concrete is inferior to asphalt concrete, as it has less strength and heat resistance.

Depending on the type of stone material, tar concrete is divided into crushed stone, gravel and sand. To prepare tar concrete, the same mineral materials are used as for asphalt concrete, the requirements for them are similar. Road coal tar is used as a binder: for hot tar concrete - D-6, for cold tar - D-4 and D-5. Tars are used as industrial production, and prepared directly at an asphalt concrete plant by oxidizing or mixing sand with a thinner (anthracene oil, coal tar, etc.).

Calculation of the composition of tar concrete can be done in the same way as asphalt concrete, while the main attention should be paid to careful selection of the amount of tar, since a slight deviation in its content in the mixture significantly affects the properties of tar concrete.

To prepare hot tar concrete, tars with a viscosity significantly lower than the viscosity of bitumen for the corresponding type of asphalt concrete are used. The reduced viscosity of tar causes a weakening of internal structural bonds, which can be compensated by an increase in internal friction of the mineral part. To do this, it is necessary to use stone materials with angular grains and a rough surface, and also to replace part or all of the natural sand with rounded grains with seedings. To prepare tar and concrete mixtures, you can use crushed stone from more acidic rocks (quartz sandstones, quartz-rich granites, etc.).

Dense tar concrete is used for making surfaces on roads of II...IV categories. Due to sanitary and hygienic conditions, the installation of top layers of tar concrete coatings is permitted only outside populated areas. When preparing tar and concrete mixtures, special safety regulations must be observed.

The tar and concrete mixture is prepared in asphalt concrete plants with forced mixers. Due to the reduced viscosity of tar, its envelopment of grains of mineral material proceeds better than when using bitumen, resulting in a shorter time for mixing materials. For the same reason, it is easier to compact mixtures when constructing coatings. The compaction coefficient, which is the ratio of the thickness of the laid mixture layer before compaction to the thickness of the compacted coating, can be equal to 1.3...1.4.

When producing a tar concrete mixture, it is necessary to strictly observe the established temperature regime, since tar is more sensitive to temperature changes than bitumen (Table 6.6.12).

Table 6.6.12

Temperature when preparing and laying tar concrete

In terms of physical and mechanical properties, tar concrete is inferior to asphalt concrete: it has less strength and heat resistance. But at the same time it has increased wear resistance. Tar concrete coating has increased roughness, a higher coefficient of wheel-road adhesion, and increased traffic safety. This is due to the lower viscosity of tars, weaker cohesive forces of intermolecular interaction, and the presence of volatile components. Volatile substances in the composition of tar accelerate the formation of the structure of tar concrete in the coating, and also contribute to a more intensive change in its properties. Tar concrete is less plastic in comparison with asphalt concrete, which is also due to the composition and structure of tars, which consist mainly of aromatic hydrocarbons, which form more rigid structural bonds in binder materials and are poorly deformed at low temperatures, as a result of which cracks form in coatings.

Control over the production of tar concrete mixture at the plant and during installation of tar concrete pavement, as well as testing methods for tar concrete are the same as for asphalt concrete.

3.8. It is necessary to select the composition of a fine-grained hot asphalt concrete mixture of type B, grade II, for dense asphalt concrete intended for the installation of the top layer of pavement in road-climatic zone III.

The following materials are available:

crushed granite stone fraction 5-20 mm;

crushed limestone fraction 5-20 mm;

river sand;

material from granite crushing screenings;

material from limestone crushing screenings;

non-activated mineral powder;

oil grade bitumen BND 90/130 (according to the passport).

The characteristics of the tested materials are given below.

Crushed granite: grade for crushing strength in a cylinder - 1000, grade for wear - I-I, grade for frost resistance - Mrz25, true density - 2.70 g/cm 3 ;

crushed limestone: grade for crushing strength in a cylinder - 400, grade for wear - I-IV, grade for frost resistance - Mrz15, true density - 2.76 g/cm 3 ;

river sand: content of dust and clay particles - 1.8%, clay - 0.2% of mass, true density - 2.68 g/cm 3 ;

material from granite crushing screenings grade 1000:

material from crushing screenings of grade 400 limestone: content of dust and clay particles - 12%, clay - 0.5% of mass, true density - 2.76 g/cm 3 ;

non-activated mineral powder: porosity - 33% of the volume, swelling of samples from a mixture of powder with bitumen - 2% of the volume, true density - 2.74 g/cm 3, bitumen capacity - 59 g, humidity - 0.3% of the mass;

bitumen: needle penetration depth at 25°C - 94×0.1 mm, at 0°C - 31×0.1 mm, softening temperature - 45°C, elongation at 25°C - 80 cm, at 0°C - 6 cm, Fraas brittleness point - minus 18°C, flash point - 240°C, adhesion to the mineral part of the asphalt concrete mixture is maintained, penetration index - minus 1.

According to the test results, crushed granite stone, river sand, material from granite crushing screenings, mineral powder and bitumen grade BND 90/130 can be considered suitable for preparing mixtures of type B grade II.

Table 7

Mineral material	Mass fraction, %, of grains smaller than a given size, mm
Mineral material
Initial data
Crushed granite
River sand
Materials from granite crushing screenings
Mineral powder
Calculated data
Crushed granite (50%)
River sand (22%)
Materials from granite crushing screenings (20%)
Mineral powder (8%)

Requirements GOST 9128-84 for mixtures type B

Crushed limestone and material from limestone crushing screenings do not meet the requirements of Table. 10 and 11 GOST 9128-84 in terms of strength.

The grain compositions of selected mineral materials are given in table 7.

Calculation of the composition of the mineral part of the asphalt concrete mixture begins with determining such a ratio of the masses of crushed stone, sand and mineral powder at which the grain composition of the mixture of these materials satisfies the requirements of Table. 6 GOST 9128-84.

The calculation consists of selecting a rational ratio between the materials that make up the asphalt concrete mixture.

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

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

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

Grain sizes according to previous level

(6.6.2)