When using cement grades 300 and 500, indicated in table. 8, the quantity should be changed using coefficients of 1.2 and 0.9, respectively.

When using slag and ash binders of strength grades 50, 100, 150, their quantity must be increased by 3; 2; 1.5 times compared to the data in table. 6.

Slags, ashes and sludge with an activity of at least 5 MPa at the age of 80 days can be used as an independent binder.

To increase the strength of the treated part of the layer by 10 - 30% or reduce cement consumption by 10 - 20%, it is advisable to introduce SDB into the mixture in an amount of 0.5 - 1% of the cement mass.

5.8. Sand cement of the greatest strength for a given cement content can be obtained by optimal quantity in a mixture of water (approximately 7 - 10% of the mass of the dry mixture), established experimentally when selecting the composition of the mixture.

The amount of water (t) for preparing sand cement when laying the base by mixing or pressing with a pad roller should be calculated using the formulas:

where l, b are the length and width of the section, respectively, m;

h1 - thickness of the upper, processed part of the layer, m;

ρпс - density of the sand-cement mixture, t/m3;

Optimal water content in sand-cement mixture, fractions of a unit;

Qpts - the amount of sand-cement mixture, i.e.

When constructing the base with vibratory rollers or rollers on pneumatic tires, the amount of water in the sand-cement mixture for good penetration into the crushed stone should be 3 - 5% less or more than the optimal one calculated according to formulas (9).

5.9. To obtain maximum strength of a layer of crushed stone treated with sand cement, before spreading the sand cement, the crushed stone should be moistened to create a mixture of optimal moisture (approximately 7 - 9% of the mixture mass).

The approximate amount of water for irrigation of crushed stone (t) when constructing the base using the method of mixing and pressing with pad rollers should be calculated using the formula

where is the optimal water content in a mixture of crushed stone and sand cement, t,

and when constructing the base by impregnation using vibratory rollers or rollers on pneumatic tires - according to the formula

5.10. The amount of sand-cement mixture Qpt or other binders introduced into crushed stone can be determined by the hollowness of crushed stone and the given processing depth (thickness of the treated base layer) approximately using the formulas

where ρ1 is the density (volumetric mass) of crushed stone grains, t/m3;

ρ2 - bulk density(volumetric bulk mass) of crushed stone in a compacted state, t/m3;

Kr - coefficient of expansion of crushed stone grains, Kr = 1 ÷ 1.15;

vпш - voidness of crushed stone, fractions of a unit;

Kp - loss coefficient, Kp = 1.03.

The value of ρ2 can be determined by compacting 10 kg of crushed stone in a steel cylinder with a diameter and height of 234 mm with a load of 10 kg on a vibration table at a vibration frequency of 3000 rpm, an amplitude of 0.4 mm for 30 s.

5.11. When constructing the base using the impregnation-indentation method, taking into account the depth of processing, fractionated crushed stone should be treated with 35 - 40% of the sand-cement mixture, which corresponds to the voidness of the material being laid.

It is advisable to treat crushed stone of a fraction of 5 - 40 mm when constructing the base using the mixing method, taking into account the depth of processing, with a sand-cement mixture in an amount of 20%, which also corresponds to the voidness of the mixture. During a feasibility study, it is allowed to process crushed stone with 35 - 40 and 50% of the sand-cement mixture.

Before starting work, to clarify the consumption of the sand-cement mixture, the voids of the materials used should be determined and formulas (12) should be used.

The approximate consumption of sand-cement mixture for the installation of 100 m2 of base at different depths of crushed stone processing, taking into account a surface layer of sand-cement 1.5 cm thick, is given in Table. 7 of these “Methodological Recommendations”.

Table 7

5.12. After establishing the laboratory composition of sand cement, the need for materials per unit area of ​​the base should be calculated.

The required amount of crushed stone (m3) can be determined using the formulas:

where Kushch is the compaction coefficient of crushed stone.

5.18. The amount of sand (m3) for preparing the sand-cement mixture should be determined using the formulas:

ρnp - bulk density of sand, t/m3.

5.14. The amount of cement Qc (t) for the preparation of sand cement can be determined by the formulas:

5.15. When carrying out work, amendments must be made to the calculated composition of materials, taking into account the actual moisture content of the materials, according to the formulas:

where Wп, Wш - humidity of sand and crushed stone, respectively, fractions of unity;

The amount of water required to prepare a sand-cement mixture on wet sand, t;

Optimal water content in sand-cement mixture, t;

The amount of water required to prepare the mixture on wet crushed stone, i.e.

6. Technology of foundation construction using the mixing method

6.1. When constructing foundations using the mixing method, crushed stone is removed onto the prepared underlying layer, the amount of which should be set taking into account the design thickness of the foundation and the compaction coefficient.

IN winter time crushed stone can be transported to intermediate roadside warehouses in the area of ​​the planned construction.

6.2. The crushed stone is pre-distributed with a bulldozer or motor grader, and finally, to the design thickness of the base, taking into account the compaction coefficient, with a DS-108 type profiler or other distributors in one pass.

When distributing crushed stone with a profiler, the cutter and cutter blade are raised. The auger blade is installed at the design level with a margin for compaction. The auger is raised 2 - 2.5 cm higher cutting edge dump.

6.3. After distribution, crushed stone, if necessary, should be moistened before treatment with sand cement to subsequently obtain a mixture of crushed stone with sand cement of optimal humidity ( estimated consumption water - up to 10 liters per 1 m2) and roll it for the passage of construction vehicles (two or three passes of the roller along one track).

8.4. The sand-cement mixture intended for processing the upper part of the crushed stone layer must be prepared in mixing plants of the SB-78 or DS-50A type. To ensure a high-quality composition of the mixture, an accuracy of sand supply of at least ±5%, cement and water ±2% of the mass of the supplied material is required.

8.5. The mixture should be transported by dump trucks or other vehicles with an appropriate feasibility study.

8.6. The sand-cement mixture must first be distributed with a motor grader, and finally laid over the surface of the distributed crushed stone with a profiler or other spreaders. The consumption of sand cement is determined taking into account the given depth of processing of the crushed stone layer and the ratio between crushed stone and sand cement in the treated part of the layer.

The sand-cement mixture is graded using a profiler in one pass at a working speed of 10 - 15 m/min. When leveling, the auger and blade are raised to the thickness of the layer of the mixture being distributed, and the cutter and cutter blade are raised to the transport position.

8.7. Upon completion of distribution, the sand-cement mixture must be mixed with the laid crushed stone to the calculated (required) depth. The maximum mixing depth for the profiler should not exceed 15 cm. Mixing is carried out at an operating speed of 5 m/min using a cutter at maximum number revolutions and auger; in this case, the blades are raised to the transport position, and the cutter and auger are set to the processing depth mark.

If necessary, the resulting mixture is moistened so that the mixture has optimal humidity, and mixed a second time with one or two passes of the profiler.

After mixing is completed, the base is laid out in one pass of the profiler. The working bodies are installed in the same way as when leveling crushed stone. Working speed 7 - 8 m/min.

6.8. Immediately after mixing, the base should be compacted using 12 to 16 passes of the roller on pneumatic tires along one track. In this case, the compaction coefficient at a depth of 5 - 20 cm must be at least 0.98. Compaction begins from the edges of the base to the middle.

6.9. Compaction must be completed within 3 hours from the moment of preparation of the sand-cement mixture, including the time for transporting the finished sand-cement mixture to the road section under construction, its distribution and compaction.

The technological gap between the preparation and compaction of a sand and slag mixture based on crushed slag or uncrushed slag with the addition of an activator - cement should not exceed 4 - 5 hours. When processing crushed stone with uncrushed granulated blast furnace slag without an activator - cement or bauxite and nepheline sludge, the technological gap can be increased to 6 - 8 hours

6.10. Upon completion of compaction, the base should be finished with a profiler and the surface layer should be finally compacted with a heavy smooth roller in one or two passes along one track.

During finishing leveling, the cutter and cutter blade are raised; The auger blade is set to the design level; the auger is raised 1 - 2 cm above the cutting edge of the blade.

6.11. Upon completion of the final leveling, it is necessary to maintain the base using one of the generally accepted methods used in the care of cement concrete, in accordance with SNiP III-40-78. It is allowed to lay the coating on the day of installation of the base; in this case, maintenance of the base is excluded.

6.12. Traffic on a foundation constructed with cement should be opened after reaching 70% of the design strength of the foundation, but not earlier than 7 days after completion of work.

7. Technology of foundation construction using the impregnation-indentation method

7.1. The essence of treating a crushed stone layer with a sand-cement mixture is to fill the voids of the crushed stone layer with the mixture under the influence of its own weight and indentation during rolling (mechanical action), in several ways:

vibration using vibrating plates of laying machines;

vibration and pressure - vibrating rollers;

deep pressure - cam rollers;

surface pressure - rollers on pneumatic tires.

7.2. Before treatment with sand cement, crushed stone should be carefully leveled with a motor grader and watered with water in an amount of 3 - 10 liters per 1 m2.

If it is necessary to ensure the passage of construction vehicles, crushed stone is rolled with a light roller in two to four passes along one track in accordance with SNiP III-40-78.

7.3. The sand-cement mixture prepared in the installation must be distributed over the surface of the crushed stone layer using a profiler or motor grader.

The consumption of sand cement is determined depending on the hollowness of the crushed stone and the depth of treatment of the layer. It is recommended to take the technological gap time between the preparation of the mixture and the end of compaction in accordance with clause 6.9 of these “Methodological Recommendations”.

7.4. To process crushed stone by vibration, it is recommended to distribute the sand-cement mixture using pavers of the DS-97, DS-108, D-345 types, equipped with vibration compacting elements. In this case, simultaneously, in one pass of the paver, the sand-cement mixture is distributed and penetrates into the crushed stone layer.

7.5. To process the crushed stone layer with vibration and pressure, you should use a vibrating roller of the DU-54 type, the vibrating roller of which promotes the penetration of the distributed sand-cement mixture into the voids of the crushed stone layer in three to four passes along one track.

7.6. To process a layer of crushed stone using the deep pressure method, it is advisable to use a cam roller, which during operation increases the gaps between individual crushed stones, ensuring an increase in the depth of penetration of the sand-cement mixture into the crushed stone layer.

7.7. Depending on the required thickness of the treated monolithic base layer, indentation can be carried out in two ways. If the required thickness of the monolithic layer is no more than 13 cm, it is recommended to press the sand-cement mixture or other binder into the crushed stone by successive passes of a cam roller, and with a thickness of more than 13 cm, alternating passes of a cam and pneumatic or smooth roller roller through each pass. The approximate number of passes of the cam roller can be assigned in accordance with table. 8 of these “Methodological Recommendations” and clarified based on the results of test indentation at the beginning of work.

Inert construction materials include a large number of names, brands and types of materials that are used in various branches of construction. Inert building materials include: sand, gravel, sand-gravel mixture, crushed stone different varieties and other types of products.

Sand is a fine-grained loose sedimentary rock consisting of at least 50% grains of quartz, feldspars and other minerals and rocks measuring 0.052.0 mm or more. Sand can be river, mountain, gully, or sea. The sand may contain impurities of dust and clay particles, rock fragments. River sand is the cleanest, sea sand is contaminated with salts and requires washing clean fresh water. Mountain and ravine areas are often contaminated with clay, which reduces the strength of mortars. River sand, mined in the beds of dried up rivers, combines two properties that are rarely found together: fineness up to 2.6 mm and high purification from foreign inclusions, clay impurities, and organic residues - this makes it a universal building material. The granulometric composition includes four groups of sand depending on the size of individual particles: dusty sand with particles up to 0.05 mm in size; small from 0.05 to 0.25 mm; average 0.250.5 mm; large 0.52.0 mm or more. The flowability of sand depends on humidity. The angle of repose (about 40°) reaches its greatest values ​​when the sand moisture content is 510%. A further increase in humidity reduces the angle of repose to 2025°. The humidity of sand layers of different heights is not the same and increases as the level of the layer decreases from the surface. Resistance to chemical exposure cement alkalis must be taken into account for sand intended as an aggregate in the production of concrete. The durability of sand is determined by its mineral and petrographic composition and the content of harmful components and impurities. Natural construction sand is intended for use as a filler for heavy, fine-grained, cellular and other types of concrete, mortars, and for the preparation of dry mixtures for road surfaces and airfields.

Sand from rock crushing screenings, having true density grains more than 2.8 t/m 3 or containing grains of rocks and minerals classified as harmful components in quantities exceeding their permissible content, or containing several different harmful components, are released for specific types construction work By technical documents, developed in in the prescribed manner and agreed with laboratories specialized in the field of corrosion. Sand is transported in bulk on open rolling stock.

Natural gravel is a loose mixture of grains of various materials (5150 mm in size) formed as a result of the weathering of rocks, which are part of igneous (less often sedimentary) rocks. There is specially manufactured artificial gravel produced by crushing hard rocks. According to the conditions of occurrence, gravel is divided into river, sea and mountain (gully). Grains of river and sea gravel are abraded when transported by water and have a rounded shape. The grains of mountain gravel are acute-angled. River and sea gravel is usually cleaner and contains less clay and organic impurities than gully gravel. The sea gravel contains admixtures of limestone grains and shell fragments. Gravel with a size of 20-40 mm is called pebbles.

The special properties of gravel include strength and frost resistance. Strength is characterized by a grade determined by the crushability of gravel during compression (crushing) during special tests and is characterized by the loss of grain mass as a percentage (dust is screened out). The frost resistance of gravel is characterized by the number of freezing and thawing cycles, at which the percentage loss by weight of gravel or crushed stone does not exceed the established values. Gravel must be resistant to impact environment. The durability of gravel is determined by the mineral and petrographic composition of the original rock and the content of harmful components and impurities that reduce the durability of concrete and cause corrosion of the reinforcement of reinforced concrete products and structures. Gravel is transported on open rolling stock (in gondola cars), with the mandatory use of measures to prevent the loss of these goods from blowing out and spilling into cracks and defects in the car body or in hopper dispensers. Crushed stone is used in construction both in pure form(for example, for filling road surfaces), and as a filler in the production of concrete and asphalt concrete. Crushed rock - inorganic granular bulk material with grains larger than 5 mm, obtained by crushing rocks, gravel and boulders, incidentally mined overburden and host rocks or substandard waste from mining enterprises for processing ores (ferrous, non-ferrous and rare metals of the metallurgical industry) and non-metallic minerals from other industries and subsequent sieving of crushed products.

Crushed stone is one of the main materials used for the construction, reconstruction, repair and maintenance of roads and railways. The quality characteristics of crushed stone largely depend consumer properties(evenness, coefficient of adhesion, etc.) and durability of roads. This especially applies to crushed stone used for the construction of the upper layers of road pavement (cuboidal crushed stone), which directly absorb high mechanical loads from moving vehicles and are exposed to natural factors (variable temperature - humidity conditions, repeated freezing - thawing, exposure to solar radiation, etc.) and anti-icing chemicals. The main properties of crushed stone. like all mineral construction goods discussed above are: strength, frost resistance, abrasion, grain shape, water absorption, radioactivity, adhesion, content of pollutants and chemicals harmful impurities. The strength of crushed stone is characterized by the tensile strength of the original rock during compression, the crushability of crushed stone during compression (crushing) in the cylinder, and wear in the shelf drum. These indicators simulate resistance stone material when exposed to those passing along the road Vehicle and mechanical impacts during the construction of road structures (laying and compaction with rollers). Depending on the strength grade, crushed stone is divided into groups: high-strength Ml, strong M, medium-strength M600800, low-strength M300600, very weak-strength M200. Most in demand granite crushed stone with strength M1200 is used, and high-strength crushed stone from hard rocks (consisting of other structural minerals) is also used, including basalt crushed stone with strength grade M. It is mainly used in the production of heavy high-strength concrete, in load-bearing bridge structures, critical foundations . Frost resistance of crushed stone is characterized by the number of freezing and thawing cycles. It is allowed to evaluate the frost resistance of crushed stone by the number of cycles of saturation in a solution of sodium sulfate and drying. Flakiness. In crushed stone, the content of grains of lamellar (the term comes from the breed of fish bream, i.e. “flaky crushed stone” means “flat like bream”) and needle-shaped forms is normalized. Lamellar and needle-shaped grains include grains whose thickness or width is three times or more less than their length. According to the shape of the grains, crushed stone is divided into four groups (content of grains of lamellar and needle-shaped forms, % by weight): cuboid up to 15%; improved from 15% to 25%; regular from 25% to 35%; usual from 35% to 50%. The presence of lamellar and needle-shaped grains in crushed stone leads to an increase in intergranular voids in the mixture. This in turn leads to an increase in the consumption of the binder component, which entails additional material costs. In addition, cube-shaped grains have greater strength than lamellar and needle-shaped grains. Consequently, the use of cube-shaped crushed stone in production is more economically feasible, for example, in the production of concrete it can significantly reduce cement consumption, and in road construction it can reduce the time and labor costs for laying by 50%. asphalt concrete pavement; brings the compaction factor closer asphalt concrete mixture to one, which ensures not only the durability of the road surface, but also increases its frost resistance. Radioactivity of rubble. When producing crushed stone and gravel, a radiation-hygienic assessment must be carried out, the results of which determine the class of crushed stone in terms of radioactivity and the types of work for which it can be used. The first class of radioactivity is used for newly built residential and industrial buildings and structures. Second class for road construction within the territory of settlements and areas of promising development. Third class for road construction outside populated areas.

Adhesion is one of the specific characteristics of crushed stone. It reflects an assessment of the quality of adhesion of bituminous binders to the surface of crushed stone. Crushed stone is transported in specialized open dump cars, hopper dispensers or gondola cars.

MINISTRY OF TRANSPORT CONSTRUCTION
STATE ALL-UNION ROAD RESEARCH INSTITUTE

allied

Approved by the director of Soyuzdornia, candidate of technical sciences E.M. Dobrov

Approved by Glavdorstroy
(letter No. 5603/501 dated 08/01/83)

Moscow 1985

The designs of crushed stone foundations treated with sand-cement mixture, developed by Soyuzdorniy, Giprodorniy and Gosdorniy, are presented, as well as a method for determining the calculated modulus of elasticity of the layer; requirements for sand-cement mixture and crushed stone treated with sand-cement mixture.

Recommendations are given for the selection of mixture compositions that provide the required strength and frost resistance of the base layer; according to the technology of constructing a crushed stone base, treated in the upper part with a sand-cement mixture by two methods: the mixing method using a profiler and the pressing method using a vibratory roller, a cam roller and a roller on pneumatic tires.

The need for quality control of construction is indicated.

The value of the average elastic modulus of the base layer E avg when calculating according to the "Design Instructions" road pavements non-rigid type" VSN 46-83 (M.. Transport, 1983) for the most common values ​​of the elastic modulus of materials treated and untreated with binders, depending on the depth of impregnation, should be assigned according to Table 1.

2.2. The calculated modulus of elasticity of the lower, untreated part of the base, depending on the properties of the materials used, must be taken according to the “Instructions” VSN 46-83 with the additions given in table. 2 of these “Methodological Recommendations”.

2.3. The calculated modulus of elasticity of the upper, processed part of the base, depending on the strength grade of the sand cement used and its quantity in the crushed stone layer, ensuring the production of different strength grades of the treated material that meets the requirements of GOST 23558-79, should be taken according to.

2.4. The minimum total thickness of the base layer should be at least 10 cm, the maximum - no more than 25 cm. The maximum size of crushed stone grains should not exceed 2/3 of the base thickness.

The maximum depth of processing of crushed stone with sand cement when constructing the base using the mixing method using a profiler and the impregnation method using a cam roller should be no more than 15 cm, and when using rollers on pneumatic tires and vibration - no more than 7 cm.

The surface layer of sand cement in the structure of a crushed stone base treated with a sand cement mixture should not exceed 1 - 2 cm.

3. Requirements for materials used

3.1. The stone materials used to construct the proposed structure must meet requirements for strength, frost resistance and grain composition.

A mixture of sand with cement or other inorganic binders should meet requirements for composition, strength and frost resistance,

3.2. The strength of crushed stone from natural rocks must meet the requirements of GOST 8267-82, the strength of slag crushed stone - GOST 3344-73.

3.3. Frost resistance of crushed stone must meet the requirements given in table. 4 of these “Methodological Recommendations”.

Table 4

3.4. When constructing the base using the mixing method, it is advisable to use crushed stone of a fraction of 5 - 40 (70) mm, by the impregnation-indentation method using rollers on pneumatic tires - crushed stone of a fraction of 40 - 70 or 70 - 120 mm. When using cam and vibrating rollers, it is advisable to also use crushed stone of a fraction of 20 - 40 mm.

3.6. Mass losses when testing crushed slag stone for structural stability should not be more than 7%.

3.7. To process crushed stone, you can use sand-cement, sand-slag (based on crushed ferrous metallurgy slag and activator-cement) and sand-ash mixtures (based on the ashes and slags of thermal power plants), as well as uncrushed granulated blast furnace slag and belite sludge.

3.8. The mixtures listed in clause 3.7 must meet the requirements of GOST 23558-79. Compressive resistance of sand cement at the age of 28 days, and of slag and sludge at the age of 90 days. must be at least 3 MPa. In each specific case, the grade of samples from the mixture should be assigned in such a way as to obtain the required strength (calculated elastic modulus) of the treated part of the layer and the entire base structure as a whole in accordance with.

The composition of the sand-cement mixture is determined in each specific case by laboratory selection.

3.9. The frost resistance of sand cement, determined according to GOST 23558-79, must meet the requirements given in.

3.10. Cement for sand-cement mixture must meet the requirements of GOST 10178-76. The beginning of setting of cement is no earlier than 2 hours after mixing.

3.11. Granulated blast furnace slag or fine slag with an activity according to GOST 3344-73 of more than 5 MPa and a maximum size of 5 mm can be used as a wedging and binding material in the proposed design.

3.12. Instead of a sand-cement mixture, alumina production waste - belite (nepheline or bauxite) sludge with the following characteristics - can be used for processing crushed stone:

Maximum grain size, mm, no more than 5

Size modulus according to GOST 8736-771 - 2.5

Bulk density, kg/m 3 900 - 1200

Natural humidity, %15 - 30

Optimal humidity, %20 - 25

Compressive strength of sludge at the age of 90 days, MPa, not less than 3

3.13. Sand must meet the requirements of GOST 8736-77 with the following additions.

The plasticity number of sand fractions finer than 0.63 mm should not exceed 2.

3.14. When processing crushed stone of a fraction of 70 - 120 mm, it is allowed to use a sand-gravel mixture and crushing screenings with a maximum size of 20 mm. When processing crushed stone of a fraction of 40 - 70 mm, the sand should not contain grains larger than 10 mm; when processing crushed stone of a fraction of 20 - 40 mm - larger than 3 (5) mm.

3.15. When preparing mixtures and watering crushed stone, it is recommended to use water suitable for drinking.

3.16. To reduce cement consumption by 10 - 15% and improve the technological properties of sand cement (increase mobility), SDB should be added to the mixing water in an amount of 0.5 - 1% of the cement mass.

The consumption of SDB is specified during laboratory selection of the composition of the sand-cement mixture from specific materials.

4. Technical and economic choice of pavement base

4.1. Depending on the depth of impregnation, as well as the required average modulus of elasticity of the base layer, you can use the base designs shown in.

4.2. The base design must be selected based on a technical and economic comparison of options, taking into account the cost of materials and mixture composition.

Cost per unit area of ​​the base structure With sppc consists of the cost of crushed stone With sch sand-cement mixture With pts, spent on the construction of this structure:

Rice.2. Examples of structures of crushed stone bases treated with inorganic binders on different depths, E avg - middle module elasticity of the base layer, MPa; h - total base thickness, cm; h 1 - thickness of the upper, processed part of the layer, see Figures for structures - elastic moduli, MPa.

The cost of crushed stone is determined by the formula:

where is the cost of 1 m 3 of crushed stone, rub.;

l, V- length and width of the site, respectively, m;

h 2- thickness of the lower, untreated part of the layer,

To ushch- crushed stone compaction coefficient;

K p- loss coefficient, K p = 1,03;

h 1- thickness of the upper, processed part of the layer. m;

Pressing sand-cement mixture or belite slurry into the crushed stone layer with a pad roller begins from the roadsides with subsequent passes moving to the longitudinal axis highway and overlapping the trace of each previous pass by at least 20 cm.

7.8. To process a layer of crushed stone using the surface pressure method, rollers on pneumatic tires should be used, pressing the sand cement with two or three passes of the roller along one track.

7.9. The final compaction of the layer after processing the crushed stone using one of the previously mentioned methods should be done with rollers on pneumatic tires of the type DU-29, DU-16V, DU-31 in 12 - 16 passes along one track and in accordance with paragraphs. 5.42 - 5.46 "Technical instructions" VSN 184-75.

When using the indentation method by alternating passes of a cam and pneumatic or smooth drum roller, the number of passes of the pneumatic roller can be reduced to five to eight due to the fact that simultaneously with indentation, partial compaction of the base occurs.

The compacted base should be finished using a smooth roller roller.

7.10. After compacting the base, it must be maintained (see these “Methodological Recommendations”).

7.11. The movement of construction vehicles along the base can be opened after it reaches 70% of the design strength when treating crushed stone with a sand-cement mixture or slag binders with a cement activator.

On a base made of crushed stone treated with belite slurry, vehicle traffic can be opened immediately after the device. If the next day after the installation of such a base it is not planned to lay the overlying layer, then the base must be maintained by watering it daily (in dry weather) with water in the amount of 1.5 - 2 liters per 1 m 2 during the entire warm period before laying the overlying layer layer of road pavement.

8. Construction quality control

8.1. All foundation materials should be tested to ensure they meet the requirements of the material standards.

8.2. The composition of the sand-cement or sand-slag mixture and its quantity per 1 m2 of base, ensuring the design strength of the mixture of crushed stone with sand-cement, must be determined by the laboratory before the start of construction by selecting materials.

8.3. The design composition of the sand-cement or sand-slag mixture should be controlled in accordance with SNiP III-40-78 using dispensers at the mixing plant.

8.4. The quality of the prepared sand-cement (sand-slag) mixture should be controlled by making three samples in each shift and testing them for compressive strength at the age of 28 days. in accordance with the requirements and methods of GOST 23558-79 when adding activator-cement to the slag, and at the age of 90 days. when using slag and sludge without additives.

Bending (split) strength, as well as frost resistance, should be determined on samples taken from every 5 thousand m 3 of the prepared mixture, in accordance with the requirements of GOST 23558-79.

8.5. When distributing crushed stone and sand-cement or sand-slag mixture, as well as slag and sludge, the thickness and width of the layer of distributed materials on every 100 m of the base should be controlled with measuring rulers and tapes. The thickness of the layer in each diameter must be measured along the axis of the base and at a distance of 1 - 1.5 m from the edges.

8.6. Quality of mixing crushed stone with sand-cement. or sand and slag mixture, as well as with slag and sludge, or the quality of impregnation should be assessed by the depth of impregnation or by the amount of binder consumed.

The depth of impregnation must be measured with a measuring ruler every 100 m in each diameter along the axis of the base and at a distance of 1 - 1.5 m from the edges.

It is recommended to determine the amount of sand-cement (sand-slag) mixture in the crushed stone layer at least once per shift by taking a sample weighing 10 kg and then sieving it on a sieve with a hole diameter of 5 mm.

8.7. The technological gap between the preparation of the sand-cement mixture and the completion of compaction of the base, as well as the quality of compaction, should be controlled in accordance with SNiP III-40-78.

8.8. The correspondence of the strength of the constructed base to the design strength can be assessed by determining the elastic modulus with a deflector or other device. The elastic modulus must be no less than the calculated (design) one.

8.9. After completion of compaction and finishing, every 100 m of the base should be checked for evenness and transverse slopes with a three-meter metal strip and a template with a level.

8.10. After compacting the base, it is necessary to ensure the timely pouring of film-forming material or water. Lack of maintenance reduces the strength of the base by 50%. Reducing maintenance time (when watering) to 21 days. from the moment the base is compacted, the strength decreases by 8 - 10%, up to 14 days. - by 20 - 25% and up to 7 days. - by 25 - 30%.

I. SCOPE OF APPLICATION

The technological map is intended for use in developing a project for the production of work and the organization of labor at a construction site.

This technological map is used when constructing a sand-cement base using a concrete spreader DS-99 equipped with a vibrating beam. The sand-cement mixture is prepared in high-performance plants. This method makes it possible to construct bases with smooth edges and vertical side edges, which is an indispensable condition for the construction of bases and coverings of airfields.

The technological map assumes the distributor's productivity per shift of 650 m of base with a width of 7.5 m and a thickness of 0.2 m.

Before installing the sand-cement base, the underlying structural layers of the base are accepted by representatives of the technical inspection. In addition, for the distributor, follower strings are installed on both sides of the row in accordance with the instructions of the technological map “Installation of follower strings when constructing bases and coverings of airfields”, M., Orgtransstroy, 1978.

If the conditions accepted in the technological map change, it is necessary to adjust and link the map to the specific conditions of the work.

II. INSTRUCTIONS FOR PRODUCTION PROCESS TECHNOLOGY

The DS-90 distributor is intended for the distribution of concrete, as well as soils strengthened with cement. It has three working parts: a retractable conveyor for receiving the mixture from a dump truck and delivering it to the base; milling-screw working body for distributing the mixture; blade for leveling the mixture into a layer of a given thickness.

In the front part of the distributor frame there is a vibrating beam for collapsing and preliminary leveling of the unloaded mixture. The sides of the machine are equipped with sliding formwork. For preliminary dosing of mixtures, in the front part of the distributor there is a trailed inventory hopper - a pneumatic dispenser, and a vibrating beam is suspended at the back for its compaction (Fig. 1).

Rice. 1. Technological diagram of the sand-cement base:

1 - dump truck; 2 - distributor; 3 - distributor of film-forming materials DS-105; 4 - string; 5 - vibration beam; 6 - hopper - dispenser; 7 - sliding formwork

Technical characteristics of concrete spreader DS-99

Engine power, hp................................................... .................................... 235

Type of drive................................................ ......................................... Hydraulic

Fuel tank capacity, l................................................... ........................... 460

Width of base laying, m................................................... .................... 7.3 - 8.5

Machine weight, t................................................... ................................................... 40

Speed ​​(forward and reverse), m/min.................................... ....................... 0 - 72

Minimum turning radius, m................................................... ............... 45.5

In this regard, the side formwork of the distributor must be extended so that its ends extend beyond the vibrating beam and protect the edges of the laid layer from collapse during vibration compaction.

The sand-cement base is arranged in rows, the lighthouse rows are made first. After the sand cement in these rows has gained strength sufficient for the passage of the distributor, a sand cement base is installed on the intermediate rows. In this case, the distributor tracks pass over the hardened sand concrete of the lighthouse rows (Fig. 2).

Rice. 2. Diagram of operation of the distributor when laying sand-cement mixture on the intermediate row:

1 - distributor; 2 - caterpillar; 3 - vibration beam; 4 - sand-cement base of the intermediate row; 5 - hardened sand-cement base of lighthouse rows

The sand-cement mixture prepared in the installation is delivered to the installation site by dump trucks.

The amount of mixture required to construct the base in each shift is approximately determined by the formula:

Q = lbhk at k P ,

Where Q- amount of mixture in loose state, m3;

l- grip length, m;

b- row width, m;

h- thickness of the base in a dense body, m;

k y is the mixture compaction coefficient;

k n is the loss coefficient during transportation and installation.

Approximate compaction coefficient of sand-cement mixture k y = 1.3 - 1.4, and the mixture loss coefficient k n = 1.03. The value of these coefficients is clarified during the process of laying the mixture.

When installing a sand-cement base, the following work is performed: preparation of the distributor, distribution and compaction of the sand-cement mixture, as well as film-forming materials for maintaining the base. In this case, the sand-cement mixture is unloaded either into a dosing hopper located in front of the distributors, or into the receiving hopper of a retractable conveyor, which is located on the side. The first method is used in cases where dump trucks delivering the mixture are allowed to enter the underlying layers of the row. This makes it possible to significantly increase the pace of work and improve the surface quality of the sand-cement base.

Preparing the distributor for operation

During preparation, the retractable conveyor is removed from it, the machine is installed at the beginning of the row and oriented relative to the longitudinal axis of the row. The milling-screw working body and the blade are aligned along a cord stretched between the lower edges of the side walls of the distributor. In this position, the indicator arrows should show zero.

A trailed receiving hopper - a pneumatic dispenser - is mounted in front of the distributor, and a vibrating beam is hung at the back. The side extended sliding formwork is installed so that the gap between the lower edges of the formwork and the base (the underlying structural layer) is approximately 1 cm.

After this, the working parts of the distributor are installed in the following position (Fig. 3): dump - above the design mark of the top of the sand-cement base by (7 - 8 cm) the amount of reserve for compaction; the milling-screw working body is 5 cm below the cutting edge of the blade; The vibrating beam is raised to the top position by hydraulic cylinders.

Rice. 3. Installation diagram of the working parts of the distributor when laying the sand-cement mixture:

1 - rear wall of the dosing hopper; 2 - cutter - auger; 3 - dump; 4 - vibrobeam; h- thickness of the base in a dense body;h 1 - thickness of the loose mixture layer; δ - margin for compaction

The rear wall of the trailed bunker is raised by hydraulic cylinders to a height at which the cross-sectional area of ​​the prism of the sand-cement mixture laid by the bunker would be equal to the cross-sectional area of ​​the sand-cement base.

Example.

The cross-sectional area of ​​the sand-cement base in the loose layer is 7.5 × 0.28 = 2.10 m 2.

The area of ​​the mixture prism formed by the hopper (Fig. 4) with a lifting height of the rear wall above the base of 0.39 m is equal to

Rice. 4. Cross section of a prism of sand-cement mixture laid with a dosing hopper

Therefore, the rear wall of the hopper must be raised above the base (underlying layer) by 39 cm.

Level and course sensors are installed on the jibs, they are adjusted, and the tracing rods come into contact with the strings.

Distribution and compaction of sand-cement mixture

The distributor is installed so that the rear wall of the receiving hopper is at a distance of a meter from the beginning of the row.

The dump truck is driven in reverse until the wheels stop against the thrust rollers on the hopper and the mixture is unloaded through the hopper onto the base (since the hopper has no bottom).

The distributor is put into operation. The rear wall of the bunker doses the sand-cement mixture by volume, the milling-screw working element distributes the mixture across the entire width of the row, and the blade levels the surface of the layer to the design mark with a reserve for compaction.

When the vibrating beam approaches the beginning of the laid layer, it is lowered and put into operation. The speed of the distributor is set to 1 - 1.5 m/min and at the same time the required degree of compaction of the mixture is achieved (0.98).

First, the mixture is laid over an area of ​​10 - 15 m and the quality of work is checked: the thickness and width of the layer, the evenness of the surface, the transverse slope, the degree of compaction. Based on this check, the position of the working parts of the distributor is finally adjusted and the required operating speed is specified.

If the thickness of the laid layer with good compaction of the mixture turns out to be greater than the design one, lower the rear wall of the hopper and the distributor blade slightly. With a smaller layer thickness, these working bodies are raised.

During operation, maintain a uniform specified speed of movement of the distributor, since violation of this requirement will lead to uneven compaction of the mixture with a vibrating beam and the formation of flat surface sand-cement base. During forced stops, the vibrating beam is turned off and raised.

In some cases, lumps of the mixture get onto the surface of the finished sand-cement base. This indicates excessive high speed rotation of the milling-screw distributor body.

To form a flat surface of the laid layer, a mixture roller continuous along the length of the blade is supported in front of the spreader blade. To do this, make sure that the receiving hopper is constantly filled with the mixture. The driver does not place all the mixture from the bunker, but leaves part of it until the next dump truck with the mixture arrives.

Copying strings are used only when constructing a sand-cement base on lighthouse rows.

When constructing the base on intermediate rows, the side sliding formwork is removed and the guide wires are not installed. Instead, the level indicator is the laid base of the lighthouse rows, and the course indicator is the edges of these rows. Therefore, for level sensors, rods with forks are fixed to the leg forks and tracing rods are connected to them.

To maintain the course, a follower fork is installed on the front track, and a special follower disk is installed on the rear track (Fig. 5).

At the end, a working seam is made. Boards are installed across the row and secured with pins. The mixture is laid down to the board. The vibrating beam is raised in front of the board, and the junction of the laid layer with the board is processed manually. When work on laying the mixture is resumed, the board is removed.

Rice. 5. Installation of tracer sensors on the distributor tracks when laying the mixture on intermediate rows:

a) mounting the sensor on the front track; b) mounting the sensor on the rear track; 1 - sand-cement base of lighthouse rows; 2 - side edges of the base of the lighthouse row; 3 - copy rods; 4 - front track; 5 - rear caterpillar; 6 - disk; 7 - bracket with spring; 8 - bracket for mounting the copier sensor

Distribution of film-forming materials for the care of sand-cement base

Film-forming materials, for example pomarol PM-100AM, are distributed using the DS-105 machine, which is included in the set of concrete-laying machines.

At the beginning of the shift, the machine is prepared for work, installed at the beginning of the site and oriented relative to the axis of the laid base. Then the heading sensors are installed and adjusted and the contact forks (copiers) are brought into contact with inside carbon string.

The tanks are filled with film-forming materials. The nozzles required by the size of the holes are selected and installed, and the frame with the distribution system is lowered so that the distance from the nozzles to the surface of the sand-cement base (torch height) is 45 - 50 cm.

The distribution of film-forming materials begins after the first 30 - 50 m of the base have been laid.

The pressure in the distribution system is raised to 4 - 6 kgf/cm2. The distribution of film-forming materials is carried out in two stages. During the first dose, half the norm is distributed, 0.4 - 0.5 l/m2. The machine is returned to the beginning of the section and, after 30 - 60 minutes, a second distribution is carried out at the same filling rate.

The operating speed of the machine when distributing film-forming materials should be at a filling rate of 0.4 l/m 2 - 14 - 16 m/min; at a filling rate of 0.5 l/m 2 - 9 - 11 m/min.

During operation, the actual filling rate is monitored and, if necessary, the speed of the machine is changed. In the tank, the film-forming materials are periodically mixed.

At the end of the work, the machine is moved beyond the finished base, the nozzles are cleaned and washed with kerosene, the distribution system is cleaned and the machine is washed. The installation of the next structural layer of the base or coating is permitted no earlier than after 14 days.

Carrying out work on the method of unloading the mixture into the hopper of a retractable conveyor

This method is used in cases where the movement of dump trucks along the base of the row is prohibited (weak base, presence of an insulating layer).

To distribute the sand-cement mixture, the distributor is installed at the beginning of the section, it is oriented relative to the longitudinal axis of the row and the working elements are installed in the following position: the blade is at the level of the top of the sand-cement base, taking into account the allowance for compacting the mixture; cutter - auger 5 cm below the cutting edge of the blade (counting relative to the cutter teeth).

The mixture is distributed and compacted with a vibrating beam in the following sequence. The operator extends the conveyor and receives the mixture alternately from two dump trucks, then removes the conveyor, distributes the mixture with a cutter-auger at the operating speed of the distributor 1 - 1.5 m/min and compacts it with a vibrating beam. The driver repeats such work cycles continuously.

Frequent stops of the distributor to receive the mixture reduce the pace of work. To increase the rate of laying the mixture, the following technique is used: in front of the distributor, the mixture is unloaded from an adjacent row onto the base, taking measures to preserve the edges of the adjacent row from destruction by the wheels of dump trucks. A retractable conveyor feeds the mixture to its full volume.

Otherwise, the work of distributing the mixture, compacting it with a vibrating beam and distributing film-forming materials is carried out in the same sequence and using the same techniques as with the method of unloading the mixture in front into the dosing hopper.

Instructions for the quality of work

The quality of work must meet the requirements of the “Instructions for the production and acceptance of airfield construction work”, SN 121-73, M., Stroyizdat, 1974, as well as the requirements of the “Instructions for the use of soils strengthened with binding materials for the construction of foundations and coatings of highways and airfields", SN 25-74, Gosstroy USSR, M., Stroyizdat, 1975.

When performing operational quality control of work, they are guided by the technology map for operational quality control of work ().

Safety instructions

When installing a sand-cement base, the requirements of the “Safety Rules for the Construction, Repair and Maintenance of Highways”, M., “Transport”, 1969, should be met.

When working with film-forming materials, the following safety rules must be observed:

1. During operation, the operator of the distributor of film-forming materials must wear overalls, canvas mittens, hat and safety glasses.

3. In hot weather, drums containing film-forming materials create increased pressure, so care should be taken when opening them.

4. If film-forming materials get on the skin of your hands, you should immediately wash them off with kerosene, and then wash your hands with warm water and soap and wipe dry.

III. GUIDELINES ON LABOR ORGANIZATION

Before starting work on installing a sand-cement base, do the following:

clear the operating area of ​​the distributor from foreign objects and materials;

install carbon strings (for lighthouse rows);

lay temporary culverts in low areas to release water from intermediate rows;

collect the necessary machines, equipment, tools, materials at the work site (see “Material and technical resources”);

fence the area with barriers and signal signs;

prepare and maintain in good condition paths for the supply of sand-cement mixture. In dry and hot weather, they are periodically watered to reduce dust and create safe work motor transport;

The work area is provided with mobile equipment: a carriage - an office, - a pantry, - a shower, a dining room), drinking water and water for technical purposes, mobile bathrooms, and a medical kit.

Work on the installation of a sand-cement base is carried out, as a rule, in two shifts, with a 650 m long gripper assigned to each shift.

To work on each shift, a team of workers is organized, which includes a 6-grade distributor operator. - 1; assistant driver 5 grades - 1; operator DS-105 for distribution of film-forming materials 5 sizes. - 1; road workers: 4 grades - 1, 3 sizes - 2, 2 sizes - 1.

At the beginning of the shift, the distributor operator and his assistant prepare the machine for work, install sensors and place tracing rods on the string.

During operation, the driver controls the distributor, receiving hopper and vibrating beam, and the assistant driver, following the machine, controls the quality of work (flatness of the base surface, transverse slope, layer thickness and, with a laboratory assistant, the quality of compaction).

The DS-105 operator distributes film-forming materials over the finished sand-cement base.

A 3rd grade road worker, moving in front of the distributor, lowers the string for the entry of dump trucks, controls the movement of these vehicles, and keeps track of the incoming mixture. As the distributor approaches, it lifts the string and hangs it on the rack brackets.

Road worker 2 grades takes the mixture into the hopper, cleans the body of the dump truck, and, if necessary, transfers the mixture with a shovel to the vibrating beam.

Road workers 4 and 3 grades. follow the distributor and eliminate minor defects on the base before distributing film-forming materials - correct edge collapses, install temporary formwork, seal seams at the joints of rows.

At the end of the work, road workers participate in cleaning the distributor and its components.

IV. SCHEDULE OF THE PRODUCTION PROCESS FOR CONSTRUCTING A SAND-CEMENT BASE WITH A DS-99 DISTRIBUTOR EQUIPPED WITH A VIBRATING BEAM (SHIFT CAPACITY - 650 m OF BASE, PRODUCTIVITY IN TWO SHIFTS - 1300 m ROW OR 9750 m 2)

Note . The graph shows a fraction: the numerator is the number of workers, the denominator is the duration of the operation in minutes.

V. CALCULATION OF LABOR COSTS FOR CONSTRUCTING A SAND-CEMENT BASE WITH A DS-99 DISTRIBUTOR EQUIPPED WITH A VIBRATING BEAM (PER REPLACEMENT - 650 m OF BASE or 4875 m2)

VI. TECHNICAL AND ECONOMIC INDICATORS

DS-99 distributor utilization coefficient over time during a shift k c = 0.92.

VII. MATERIAL AND TECHNICAL RESOURCES

A. Basic materials

Note . The quantity of materials is determined for the following conditions:

compaction coefficient of the sand-cement mixture - 1.4;

loss of the mixture during transportation and installation - 3%;

the rate of distribution of pomarol is 1 l/m 2, losses 0.5%;

Under other conditions for laying the mixture and caring for the base, the amount of materials should be recalculated.

B. Machinery, equipment, tools, inventory

Note . The inventory requirements do not include tracing strings and accessories for their installation. The quantity of this inventory is determined according to actual needs.

VIII. CARD OF OPERATIONAL QUALITY CONTROL OF WORK DURING THE CONSTRUCTION OF AN AERODROME FOUNDATION FROM SAND-CEMENT MIXTURE USING A DS-99 DISTRIBUTOR EQUIPPED WITH A VIBRATING BEAM

Cross slope

Δ4 = +0.002

Surface evenness (allowable clearance under a 3-meter rail), mm

Δ5 = 5

Base design diagram indicating maximum deviations

Notes . 1. The density coefficient of the base must be at least 0.98 of the maximum standard density.

2. The uniformity of distribution of the film-forming material is controlled by pouring a solution of phenolphthalein or of hydrochloric acid. The number of points of foaming or redness in an area of ​​100 cm2 should be no more than two.

Mass production of sand concrete products requires careful step-by-step organization of the technological process, and compaction is one of these stages.
When producing heavy concrete using traditional molding schemes, compaction quality control is usually not carried out. The manufacturer is content with organoleptic signs of compaction, for example, the appearance of laitance on the surface of the product. Manufacturing practice confirms the sufficiency of these characteristics, primarily due to the workability margins included in the design of the composition to simplify the molding stage. The price for increasing workability is an increase in cement consumption, but enterprise management willingly agrees to this, believing that high-quality compaction when using aggregates with unstable properties is sufficient compensation for excess cement consumption.
When manufacturing structures from sand concrete, where there is always more cement paste than in heavy concrete, the appearance of cement laitance on the surface of the molded product is no longer a sufficient sign of high-quality compaction.
The “Recommendations for the manufacture of structures from sand concrete” states that sufficient indication high-quality compaction of cement- sand mixtures is to obtain a compaction coefficient Ku≥0.97.
Control of the compaction coefficient should accompany both the design of the composition and the manufacture of structures. This is especially important for sand concrete, where undercompaction is the main defect in the mass production of small-piece products from especially and super-hard mixtures.

Application of intensive compaction methods for cement-sand mixtures