Sealing additives for soil in road construction. Strengthening and stabilization of soils

Soil stabilization technology turns virtually any soil into a solid foundation.

National Resources offers soil stabilization services (GOST 23558-94) using inorganic binders. Soil stabilization is an effective way to create bases for various coatings.

The company "National Resources" has been working in the field of construction and equipment of the road base for more than 10 years.

It is engaged in a full range of works on the construction of pavement and road foundations, as well as industrial and storage sites, the method of strengthening and stabilizing the soil using various materials.

A guarantee of a well-designed and executed project is the long-term experience of the company - one of our main advantages.

A team of professionals is ready to work in the most difficult weather conditions with almost any type of soil. Thanks to extensive practical experience and the accumulated knowledge base on soil analysis, using modern equipment, the company "NR" provides the selection optimal composition stabilizing mixture, which is a guarantee and guarantee of the quality of the road base for up to 15 years.

Behind the quality of projects, works and materials is close scientific cooperation with specialized institutes in Russia and the CIS countries, which gives us even more confidence both in the technologies used and in their high performance. Each sample of soil and pavement is subjected to laboratory tests under specially simulated conditions, which makes it possible to avoid mistakes during road construction.

Feedback on completed orders and professional as well as scientific cooperation, summary completed projects and our warranty provide you with confidence in the construction or repair of roads by National Resources.

The company "NR" has efficient and productive equipment to perform a full range of services for road stabilization and recycling.

The company's fleet uses the largest and most productive Wirtgen WR250 recyclers. The capacity of one recycler is 8000 m2 per shift. Compaction depth reaches 560mm.

Fleet of 10 Wirtgen WR250 recyclers. allows you to perform the most complex work in the shortest possible time.

Also, in the presence of the company are used: cement spreaders, rollers, motor graders and mounted stabilizers (for use in small areas).

About technology

soil stabilization is a process of thorough grinding and mixing of the soil with the appropriate inorganic binders (cement or lime), they are added in a proportion of 5-10% by weight, followed by compaction.

When using this technology with inorganic binders, there is no need for a significant amount of transport, since absolutely any local soil can be strengthened, be it loam, sandy loam or sandy soil, which is nearby, and only binder materials remain to be delivered to the work site.

The presented technology is a durable wear-resistant construction of roads and sites with high quality characteristics for any extreme loads and climatic conditions Russia.

Road construction by soil stabilization

Soil stabilization technology is used in the following construction:

• repair and reconstruction of existing roads;
• during the construction of highways IV–V categories;
• temporary, technological, auxiliary and dirt roads;
• sidewalks, park, pedestrian and bicycle paths;
• car parks, parking lots, storage and shopping centers and terminals when creating solid foundations for the construction of objects of various categories;
• landfills for solid waste and hazardous substances;
• grounds for industrial flooring and laying of paving slabs;
• foundations for railroad tracks.

Ground stabilization video

Advantages: COST / WORK TIME / STRENGTH OF THE FOUNDATION / WARRANTY

This method has a number of advantages over traditional methods of building road foundations.

COST 50% reduction in the cost of construction work.

SPEED OF WORKS from 3,000 m2 to 8,000 m2 per shift.

STRENGTH OF THE BASE the ultimate compressive strength during soil stabilization using inorganic binders reaches 500 MPa.

WARRANTY The warranty period of the road base with soil stabilization technology reaches 15 years.

The presented advantages became possible due to the following factors:

• complete rejection of the use of non-metallic materials (crushed stone, sand),
• absence earthworks on the excavation of soil for the road structure, and, accordingly, the lack of disposal of this soil,
• complete mechanization of the process,
• modern technology that allows you to accelerate the speed of work.

Soil stabilization
The resulting base can be used both independently, without applying a layer of asphalt, and together with it.

It is also important that the method does not have a harmful effect on the environment, and also implies complete autonomy and freedom in the choice of material. Modern equipment makes it possible to efficiently carry out soil stabilization directly on site to a depth of up to 50 cm in one working pass with high accuracy in the dosage of binders.

Know-how of National Resources

The use of Hint's disintegration technology made it possible to obtain a stabilized base using cement in an amount of 2%.

This technology makes it possible to increase the strength characteristics of the stabilized base.

Soil stabilization is the possibility of building a road from the ground, without the imposition of an expensive asphalt concrete base.

There is a flexible system of discounts! Individual approach in the formation of a pricing policy for each client!

Soil stabilization

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About road construction machines

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Soil stabilization

The soils used in road construction have certain limiting strength indicators, i.e., they are able to carry a certain amount of load from moving vehicles.

AT last years was developed new method increasing the strength of soils by adding additives of binders - cement, lime, bitumen, tar. This method is called soil stabilization with binders. The soils strengthened by this method are used for the construction of road foundations under capital coverings from asphalt concrete and for the construction of lightweight pavements instead of asphalt concrete. The cost of building bases and pavements from stabilized soil is 3.5-5 times cheaper than the construction of crushed stone bases or asphalt concrete pavements. A base layer of stabilized soil 30 cm thick is equal in strength to a layer of crushed stone 18-20 cm thick; a light pavement of stabilized soil 15-20 cm thick is equal to the strength of an asphalt concrete pavement 6-10 cm thick.

Previously, road surfaces were constructed in the form of a cobblestone pavement (cobblestone highway) or by laying a layer of crushed stone 6-15 cm thick, rolled by carriage wheels or road rollers (graveled stone or "white" highway). With the development of automobile traffic, the strength of these highways turned out to be insufficient.

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The main reason for the rapid destruction of white highways by car wheels is the weak connection of individual gravel with each other.

In addition, in connection with high speeds road traffic, new requirements are imposed on the roads - evenness of the surface, dustlessness and good grip with tires.

The increase in the cohesion of crushed stone in the coating is achieved by introducing organic binders into the thickness of the coating - bitumen or tar, which increases the strength and durability of the road. The presence of binder materials in the coating allows you to evenly roll its surface with rollers, bind dust and thus remove dust from the road and improve tire grip. The organic binder coats the mineral particles with a thin film and binds them together.

A white highway treated with bitumen or tar becomes black and therefore such coatings are called "black".

Soil stabilization can be carried out both on local and imported soils. For stabilization, sandy loam and loam are the most suitable. When stabilizing soils, the upper plant layer (sod) with the roots of grasses and shrubs must be removed, since voids form when the vegetation particles rot.

Soil stabilization consists of the following main operations: - preparation of a strip of soil; – loosening and grinding of soil; - distribution of binder material; - mixing of crushed soil with a binder material; - watering and final mixing with water of crushed soil, mixed with a powdered binder when stabilized with cement or lime; – strip compaction, stabilized soil.

Strip preparation consists in removing the turf layer and roots of stumps and shrubs and in planning the strip with backfilling of local depressions and cutting off mounds and bumps.

At the same time, the subgrade is profiled and side ditches are cut. Strip preparation work is carried out by bulldozers and, if necessary, rooters, as well as graders or motor graders.

If local soils are stabilized, then the corresponding subgrade strip is subjected to loosening and grinding. If stabilization is not carried out on local soil, then the necessary soil is brought from the near-traoss quarry by scrapers, tractor trailers or dump trucks, the brought soil is distributed and planned on the subgrade and then it is loosened and crushed.

It is advisable to loosen dense, heavy sandy loam and loam with trailed tractor plows and harrows.

Light soils are loosened by trailed tractor cutters, which then crush the loosened soil. Loosening and grinding are carried out by several passes of machines along the processed strip.

The more intensively the soil is crushed, the better and more evenly it mixes with the binder and the stronger the stabilized layer is obtained. In normally crushed soil, the number of particles 3-5 mm in size should not exceed 3-5% by weight, which is checked by special samples.

cement stabilization

Cement or lime is brought to the job site in cement trucks or dump trucks and manually spread with shovels evenly over the treated strip immediately before dry mixing. Special machines for the distribution of cement and lime are not yet manufactured.

The soil is dry mixed with a binder, then watered with water from an asphalt distributor, after which it is finally mixed with several passes of a trailed cutter and compacted with rolling.

Stabilization with bitumen or tar

Bitumen or tar is brought and poured with an asphalt distributor immediately before mixing so that the binder does not cool down.

The soil with the binder is mixed with several passes of the trailed cutter and compacted with rolling.

The stabilized layer is compacted with a D-219 pneumatic tire roller on a trailer to a car or a wheeled tractor. Towing the roller by a caterpillar tractor is unacceptable due to damage to the strip surface by caterpillar spurs.

The technology of soil strengthening/stabilization using inorganic binders has been used in construction for more than 60 years, both in our country and in many foreign countries.

When using this technology, depending on the final result, soil stabilization and soil strengthening are separated.

When stabilizing soils, it is possible to improve the conditions for compaction of local soils, including waterlogged and heaving ones. This method allows you to arrange frost-protective layers, as well as increase the bearing capacity of foundation soils.

When strengthening soils, there is a significant increase in the physical and mechanical characteristics of local soils. The method is used for the installation of both frost-protective layers and bearing layers of bases.

Regulatory documents: GOST 30491-97. Organo-mineral mixtures and soils reinforced with organic binders for road and airfield construction. Specifications". GOST 23558-94. “Mixes of crushed stone-gravel-sand and soils treated with inorganic binders for road and airfield construction. Specifications".

Application area

In the absence of strong stone materials in the construction area, as well as sandy soils suitable for the construction of foundations, as domestic experience shows, it is possible to effectively use the available local soils, improved or strengthened with various binders.

Soil stabilization/reinforcement technology using the mixing-in-situ method can be used in the construction of structural base layers: top and bottom layers.

Description

The use of binders in the stabilization/strengthening of local soils can increase density, increase water resistance and frost resistance.

Modern equipment makes it possible to effectively improve/strengthen local soils directly on site to a great depth (up to 40 cm) in one working pass with high accuracy in the dosage of binders.

The existing single-pass mixing equipment makes it possible to obtain a homogeneous mixture even when working with high-moisture soils.

Binders and additives

The main and available mineral binders are cement and lime. Usually, the dosage is from 3 to 10% (? 6%) of the mass of the soil to be reinforced.

When using lime or cement to stabilize or strengthen soils, it is almost always possible to provide the required soil compaction coefficient based on laboratory selections of the dosage of binders.

Silty sandy loams and sandy-argillaceous soils of optimal composition are most suitable for strengthening with cement.

Work production technology

During the work, the following technological operations are performed:

• Base surface layout
• Dosage of organic binders and distribution
• Mixing with a milling machine to a predetermined depth, if necessary, the dosage of organic binders (bitumen emulsion) and chemical additives directly into the mixer.
• Layout and compaction of the base to the specified indicators.

A special set of mechanisms can have a capacity of 5,000 to 15,000 m3 per shift, depending on the depth of reinforcement and the possibility of delivering the required amount of binder materials to the site.

Features of the vertical layout of sites with the use of soil stabilization / strengthening technology

When designing the vertical planning of territories, the general principle of planning earthworks is usually used, taking into account the so-called " zero balance earthen masses. This principle makes it possible to reduce the costs associated with the movement of earthen masses across the territory, and also eliminates the transportation of both missing and excess materials and the removal of soil.

The traditional method of excavation has the following disadvantages:

• There is a need to remove unsuitable (waterlogged, heaving) soils
• During the construction of open areas (internal roads, parking lots), there is a problem of designing pavement structures to ensure frost resistance requirements; in the Central region of the Russian Federation, to meet this requirement, the total thickness of structures requires the installation of structures with a total thickness of about 1.0 m. coincides with the level of "zero balance of earthworks", which means that the installation of foundations requires the delivery of a significant amount of imported materials (sand, crushed stone, etc.). Accordingly, additional costs.
• road construction. Processing quicklime of the soil intended for the construction of the roadway makes it possible to obtain a solid base with good bearing characteristics. Lime modifies fine-grained and wet clay soils, and also stabilizes chemically active soil due to the pozzolanic reaction.

When using the technology of soil stabilization / strengthening, it is possible to apply a more optimal solution in the construction of objects for various purposes.

The use of soil stabilization / strengthening technology allows you to get up to 20% savings compared to the traditional method.

For the installation of concrete industrial floors, it is recommended to stabilize the base for two reasons.

First, a high-quality solid foundation.

Art. scientific employee T.T. Abramova
(Moscow State University named after M.V. Lomonosov),
A.I. Bosov
(FSUE "ROSDORNII"),
K.E. Valieva
(Moscow State University named after M.V. Lomonosov)
________________________________________

Introduction

At present, there is a rapid growth in the volume of construction of various objects of transport infrastructure. In most of the territory of Russia, there are no traditional road construction materials, which predetermines their shortage and causes an increase in the total cost of the construction project. In this regard, it is advisable to use local soils for the construction of pavements. In order to be able to use, for example, the most common clay soils in the Russian Federation, which are known to have high cohesion and strength in the dry and negligible in the water-saturated state and are heaving, it is necessary to ensure their durability and stability, regardless from changes in humidity, weather conditions and variable loads during traffic. This can be achieved only if there is a fundamental qualitative change natural properties such soils.
The development of soil-based compositions with inorganic (cement, lime, fly ash, etc.) and organic (bitumen, bitumen emulsions, tar, polymer resins, etc.) binders was carried out by many scientific schools since the 20s of the last century. An analysis of the results of their work showed that cement-based compositions are characterized by high rigidity and, accordingly, crack formation. In addition, cement soils have increased abrasion, which does not allow them to be used for paving without a protective wear layer. Liming soils does not give them frost resistance. Organic binders contribute to the development of rutting, as well as plastic deformations of the base layer.
Years of research in various countries The world have shown that an increase in the water resistance of clay soils can be achieved using surface-active substances (surfactants), which make it possible to stabilize such soils with a small consumption of surfactants. The introduction of active reagents can reduce the need for binders, significantly improve the physical and mechanical characteristics of clay soils and make them suitable for use in construction work.
Modern road construction equipment (ground milling machines, recyclers, mobile soil mixing plants) makes it possible to effectively stabilize and strengthen soils directly on site to a great depth (up to 50 cm) in one working pass with great accuracy in the dosage of materials introduced into the soil. High-performance soil mixing equipment, which is produced by such well-known companies as Bomag, Caterpillar, FAE, Wirtgen and others, makes it possible to obtain a homogeneous mixture even when working with waterlogged soils. In this regard, in recent years, the interest of road specialists in soil stabilizers has noticeably increased both in our country and abroad.
Stabilizers are a very wide class of substances of different composition and origin, which in small doses have a positive effect on the formation of the properties of road building materials, both due to the activation of physical and chemical processes, and due to optimization technological processes. These substances can be used at almost all technological stages in road and airfield construction, from the construction of subgrade to the construction of hard surfaces, artificial engineering structures and road improvement.
Stabilizers can be of different origin, differing in properties, but they all have in common that they increase the density, moisture resistance and frost resistance of soils, reducing their heaving.
Each specific stabilizer has its own individual name, reflecting the specifics of the country of origin and application features. Among the most famous are the following clay soil stabilizers: EH-1 (USA), SPP (South Africa), Roadbond (USA), RRP-235 Special (Germany), Perma-Zume (USA), Terrastone (Germany), Dorzin "(Ukraine) and LBS (USA), Dortekh (RF), ECOroads (USA), М10+50 (USA).

1. Theoretical basis hydrophobization of cohesive soils

A distinctive feature of stabilizers is the change in the hydrophilic nature of clay soil to hydrophobic. Therefore, to ensure the stabilization of cohesive soils, it is necessary to know the basics of hydrophobization processes.
Hydrophobization is a change in the nature of the surface of mineral particles by exposing the soil to small doses of surfactants. Its physical essence lies in the fact that the wettability or non-wetting of the soil depends on the crystal structure of its minerals, the nature of their interpacket and intermolecular bonds. The main reason for wetting is the presence of uncompensated energetically active centers on the surface of minerals. Surfactant molecules contain a polar (hydrophilic) group and a hydrocarbon (hydrophobic) radical. Complete or partial elimination of wetting of soil minerals with water can be achieved by balancing the energetically active centers of the surface of soil minerals with surfactants that have this ability, and at the same time, due to their molecular nature, are not wetted by water. Large organic cations have a large volume and molecular weight, as a result of which they are vigorously and strongly sorbed by the soil, displacing inorganic cations from their exchange positions.
The second way to balance uncompensated bonds on the surface of mineral systems is based on the adsorption of dipole organic molecules by surface ions on the basal planes. crystal lattice clay minerals.
The third way is the sorption of negatively charged polar anions of the reagent by the cations of the mineral surface (Ca2+, Al3+, Si4+, etc.). This way of balancing the uncompensated bonds of soil systems can only be of particular importance, mainly for carbonate soils.
Giving clearly defined hydrophobic properties to the soil causes certain difficulties, which is due to its complexity as a colloidal-dispersed, polymineral system, containing a certain amount of adsorbed water. It is easier to achieve partial hydrophobization of the soil, which in many cases leads to changes in the structure and properties of the treated soils. Already in the early stages of research (in the 50s of the last century) on the hydrophobization of dispersed soils for engineering purposes, it was found that their treatment with cationic surfactants leads to an increase in the values ​​of the wetting angle up to 90° or more (for bentonite - from 15° to about 103° ). Such a significant change in the properties of the surface of the solid phases of the soil is accompanied by the phenomenon of flocculation and aggregation of soil systems. This mechanism can be described as a result of the interaction of the colloidal surfactant cation with the colloidal anion of the soil system. In this case, the hydrophilic part of the cation is adsorbed by soil particles, and hydrocarbon chains, connecting with each other, form aggregates of particles, which leads to coarsening of the system as a whole in terms of particle size distribution. The variables that affect the flocculating ability of surfactants are often: a) the dosage of the reagent; b) soil pH; and c) the concentration and type of inorganic salts in the soil.
Due to the decrease in the ability of the hydrophobized soil to adsorb water and the associated structural transformations, changes occur. physical properties soils, namely: a) a decrease in the ability of soil to move water under the action of capillary and gravitational forces; b) a decrease in the tendency of the soil to volumetric changes (swelling and shrinkage) during moistening and drying; c) increasing the strength of the soil system in a water-saturated state and maintaining it for a long time.
It is known that the reason for improving the rheological properties of dispersed clay soils due to the addition of small amounts of surfactants is a change in the nature of the hydrated shells of clay particles and adsorption of surfactants on the surface of clay minerals. Any interaction between molecules or ions leads to a change in their interatomic distances. I.S. Choborovskaya, studying the adsorption of SSB (high molecular weight surfactant) on various monominerals, believes that it is selective. Changes in the properties of clay soils of various compositions and states upon interaction with surfactant solutions are presented in the work of Yu.K. Egorova. The influence of three types of surfactants was studied: nonionic (OS-20, slovatone), cationic (synthegal, transferrin) and anionic (votamol, sulfanol) with a concentration of 0.1 to 10 g/l. The author found that clays of kaolinite composition adsorb surfactants less than clays of montmorillonite composition. Cationic surfactants (SAS) are adsorbed better than non-ionic surfactants (NSA). The interaction of surfactants with clays leads to coagulation of clay particles, which increases the permeability of clays for solutions. Surfactants are practically not sorbed, since the charge of their active groups coincides with the charge of clay particles. The study of the adsorption of surfactants and surfactants showed that great importance has their critical micellization concentration (CMC). When surfactant adsorption is below this value, the adsorption layer approximately corresponds to a monomolecular structure with a horizontal orientation of the main axis of the molecule relative to the interface. A more complex structure of the adsorption layer arises when the surfactant concentration is greater than the CMC, that is, when the molecules are associated. In this case, the isotherm sharply increases, which probably occurs as a result of the formation of a polymolecular adsorption layer.
Thus, it can be noted that the adsorption of different surfactants on the surface of the same mineral proceeds differently. According to the sorption activity, they can be put in the following series: surfactants → nonionic surfactants → surfactants. Consequently, the strength characteristics of various stabilized clay soils will differ sharply from each other.

2. Stabilization of cohesive soils

Major scientific studies on water repellency, carried out in the 20th century both in the USSR and abroad, showed that the issue of the duration of the water repellency process with constant moistening and water saturation of soils throughout their service life in pavement structures remains quite important.
Modern stabilizers have been successfully used for many years in the USA, Germany, South Africa, Canada and many other countries, and recently in Russia for the construction of pavements and foundations for highways, airfields, parking lots, etc. Among the stabilizers of foreign and domestic production, the following can be distinguished, known under the trade names: Roadbond, Status, Dortekh, ANT, ECOroads, Mag-GF, RRP-235-Special, Perma-Zume, Dorzin, Top Force ”, LBS, М10+50, LDC+12, Nanostab. They can be acidic, basic or neutral. The chemical composition of modern stabilizers is either patented or, being the property of authors or firms, is not fully disclosed.
Modern stabilizers have complex, multicomponent compositions, including:
sour organic products, superplasticizers and other substances;
liquid silicate, acrylic, vinyl acetate, styrene-butadiene polymer emulsions;
low molecular weight organic complexes.
Stabilizers can be cationic, anionic and non-ionic. In this regard, their interaction with the same clay mineral will not proceed in the same way.
Stabilizers of the first type have a complex composition, including acidic organic products, superplasticizers and other additives. All of them are characterized by an acid reaction of the medium with a pH in the range of 1.72 - 2.65. Water with the introduction of such stabilizers is activated due to ionization (H+, OH¯ and H3O+). The stabilizer solution, in turn, changes the charge on the surface of clay particles due to the energy exchange of electric charges between ionized water and mineral soil particles. By exchanging charges with ionized water, soil particles break natural bonds with capillary and film water. When compacting soil treated with a stabilizer solution, capillary and film water easily separates, creating conditions for high compactibility of the mixture. Thus, the stabilizer plays the role of a plasticizing additive, which allows, at a lower optimum soil moisture, to achieve more high performance its density. For acidic soils, cationic surfactants are used. For carbonate soils, it is advisable to use anionic surfactants. According to the authors, the developers of the surfactant material "Status-3", microsections of the clay soil surface, carrying a certain charge, adsorb oppositely charged ions, but at the same time, surfactant ions that are similarly charged with the surface are not directly adsorbed by it, but under the action of electrostatic forces near the adsorbed ions form together with them on the surface of the adsorbent a double electric layer (EDL). In the presence of DES surface density of a negative charge forms, as it were, an inner lining, and soil particles (anions, cations) located at the phase boundary form an outer lining of the opposite sign (respectively, the adsorption and diffuse parts of the DES), and in general the system is electrically neutral .
Studies conducted at MADI showed that after the interaction of the soil with the “Status”, its structure changes. A hydrophobic film forms on the surface of mineral grains. In soils treated with the Status stabilizer, there is a significant reduction in pores with a diameter of 0.0741-0.1480 microns compared to soils without a stabilizer (negative photometry method). At the same time, there is an increase in the pore orientation coefficient Ka in the chosen direction, which is 11.26 and 10.57%, respectively, for treated and untreated soils. The foregoing indicates directed patterns of change in the treated soil and the formation of a more stable structure of the material. It was possible to achieve a decrease in the optimal moisture content of clay soils, an increase in their water resistance, as well as a decrease in soakability, water absorption, and swelling. The rate of soaking of untreated soil is 1.5-2 times higher than that of soil treated with a stabilizer. At the same time, the stabilized soil does not acquire water resistance.
Loss of strength after water saturation can be avoided by using other soils to transform modern materials- polymer emulsions (the second type of stabilizers), with a wide range of properties. A typical polymer emulsion contains approximately 40-60% polymer, 1-2% emulsifier, and the remainder is natural water. The polymer can also vary greatly in its chemical composition, molecular weight, degree of branching, side chain size, composition, and so on. Most polymeric products used for soil stabilization and stabilization are vinyl acetate or acrylic based copolymers.
Studies conducted in the USA have shown that polymer emulsions do provide a significant increase in strength, in particular additionally in wet conditions. The process of curing the emulsion consists of "separation" and subsequent release from water by evaporation. Emulsion separation occurs when individual emulsion droplets suspended in an aqueous phase come together. On the emulsion-wetted surface of a soil particle, a polymer is deposited, the amount of which depends on the concentration of the polymer added to the mixture and on the mixing ratio with the soil.
One of such polymeric materials is LBS - liquid silicate-polymer soil stabilizer - surfactant. When an aqueous solution of LBS is introduced into the soil, an irreversible change in the physical and mechanical properties of the soil is ensured due to chemical action, by ionic replacement of film water on the surface of dusty particles with stabilizer molecules that have a water-repellent effect. Film water as a result of compaction of the treated clay soil is easily removed from it. The soil improved in this way becomes more durable and practically impermeable, which makes it resistant to all climatic conditions and capable of absorbing an increased payload even in conditions of prolonged heavy rainfall. The modulus of elasticity for soils (from sandy loam to heavy loam) stabilized with LBS reaches 160-180 MPa. Such soils also have higher (~ 50%) compared to unstabilized soils in a dry state, shear stability indicators. The effectiveness of using the LBS polymer stabilizer is most noticeable when working with highly plastic heaving clay soils. After processing, such soils pass into the category of weakly porous and non-porous. This result is achieved due to the transfer of film water, which was previously on the surface of clay particles, to a free state. Soils stabilized with LBS have high deformation characteristics. For example, samples of silty sandy loam with a plasticity number of 12 and a moisture content of 14.4% (humidity at the rolling boundary - 18%, at the yield point - 30%) after stabilization with a polymer emulsion and prolonged (28 days) capillary water saturation (samples density - 2, 26 g/cm2, skeletal - 1.98 g/cm2) were subjected to laboratory tests with a rigid die. The modulus of elasticity for them was 179-182 MPa. The degree of heaving of stabilized soils was determined in accordance with GOST 28622-90 using a specially designed installation. The results of the research showed that clay soils after exposure to LBS go into the category of non-rocky or weakly heaving and non-swelling or weakly swelling.
Innovative developments for soil stabilization and road construction are materials such as LDC+12 (liquid acrylic polymer product) and Enviro Solution JS (liquid vinyl acetate compound), as well as M10+50, a liquid polymer emulsion on acrylic base, which is a binder. The latter was specifically designed to significantly improve the characteristics of the soil, such as: adhesion, abrasion resistance, bending force, as well as to increase the durability of the pavement layer. Soils treated with M10 + 50 material are used in the construction and repair of transport infrastructure facilities, they have a number of advantages compared to other stabilizers produced at present stage. M10 + 50 is used in soils with a plasticity number of up to 12. The emulsion dissolves well in fresh and salt water. Stabilized soil acquires water resistance. The soil layer, treated with M10+50 emulsion, can be used for the passage of vehicles already 2 hours after the work. Such a layer does not require special care, unlike a layer reinforced with cement or lime. Soil treated with M10 + 50 composition has the highest ability to resist destruction from atmospheric influences and ultraviolet radiation. More than 20 years of experience with this polymer stabilizer shows significantly better results with acrylic stabilizers compared to non-acrylic polymers.
Clay soils can be transformed using other ion-active modern materials (Perma-Zume, Dorzin) - third-type stabilizers based on enzymes. Such enzymes are a composition of substances, mainly formed in the process of cultivating organisms on a complex nutrient medium with some additives. Perma-Zume 11X reduces the surface tension of water, which promotes rapid and uniform penetration and absorption of moisture into clay soil. Clay particles saturated with moisture are pressed into the voids of the soil and completely fill them, thus forming a dense, hard and long-term layer. Due to the increased lubricity of the soil particles, the required soil density is achieved with a lower compression force. The results of a study by scientists at the IPC SB RAS (Tomsk) showed that "Dorzin" is a product of microbial fermentation of sugar-containing products such as molasses (molasses). It has been established that the organic part of the preparation is mainly represented by the following compounds: oligosaccharides (from monosaccharides to pentasaccharides), amino compounds of the arginine type, mannitol (D-mannitol), hydroxy compounds of the trehalose type, nitrogen-containing derivatives of lactic acid.
T.V. Dmitrieva managed to determine that the effectiveness of the impact of organic complexes on rock-forming minerals is directly dependent on the structural and chemical nature of layered aluminosilicates and decreases in the series: X-ray amorphous phases → smectite → mixed-layer formations → illite → chlorite → kaolinite. At the same time, the cationic capacity is an integral characteristic, the use of which makes it possible to reveal the degree of effectiveness of the structure formation of stabilized soil during express assessment. When an additive is introduced into the system, a decrease in the specific surface area of ​​the studied samples is observed (Table 1). The obtained data testify to the "gluing" of microsized individuals of clay minerals by organic complexes of the stabilizer. The degree of influence of the additive is most pronounced in samples of monomineral smectite clay.

Table 1

Active specific surface of clay rocks

Note: active specific surface is an average characteristic of porosity or dispersion, taking into account the morphological features of the substance under study.

After the interaction of enzyme-based preparations with clay soils, they acquire the following characteristics: high physical and mechanical properties, temperature resistance, water resistance, corrosion resistance.
It follows from the foregoing that the structure formation of the clay component of cohesive soils when interacting with a stabilizer is due to the blocking of active hydrophilic centers of dispersed minerals, which leads to a decrease in the specific surface of the soil, cationic capacity and an increase in hydrophobicity.
The impact of surfactants on cohesive soils leads to a complete exchange of cations. The decrease in the ability of the stabilized soil to adsorb water and the structural transformations associated with this cause a change in the physical properties of soils.
For surfactants, it is better to use carbonate soils, in which the interaction of negatively charged organic anions of the stabilizer with cations of the mineral surface of the soil (Ca2+, Al3+, Si4+, etc.) can be more noticeable.
Organic ions in polymer emulsions are held together by molecular and hydrogen forces in addition to electrostatic forces. They are adsorbed more strongly, forming complex organomineral complexes. In this regard, it is possible that the reaction of the soil environment (pH) and its salt composition do not have a significant effect on soil stabilization with polymer emulsions.
When compacting soil treated with a stabilizer, capillary and film water are easily separated, creating conditions for high compactibility of the soil mixture. It has now been established that soils treated with stabilizers must have a hydrophobicity coefficient of at least 0.45, and the value of the maximum density is higher than that of the original by more than 0.02%. The content of dusty and clay particles in the used soils should be at least 15% by weight of the soil. It is allowed to use soils for stabilization with a content of silt and clay particles less than the specified limit, provided that the grain composition is improved by clays, loams and the amount of silt and clay particles is brought to the required level. Clay soils with a plasticity number of more than 12 must be crushed to the degree of crushing required by SP 34.13330 before introducing stabilizing and binding materials into the soil. The relative humidity of clay soils in this case should be 0.3-0.4 moisture at the yield line.

3. Complex methods for the transformation of cohesive soils

To enhance the processes of interaction of cohesive soils with a stabilizer, binders (cement, lime, organic binders) can be additionally introduced into the system in a small amount. As a result of this, we can expect an improvement in all characteristics of artificially transformed soils. To determine what processes take place in a complex system "soil-stabilizer-binder", consider the results obtained by Yu.M. Vasiliev for clay soils after interaction with various amounts of binder using cement as an example. It is usually believed that when soil is treated with cement, structural bonds of only a crystallization type develop. Experimentally, he found that with the introduction of cement, not only bonds of the crystallization type develop, but also bonds that are of a water-colloidal nature are strengthened. The strength of coagulation bonds and the intensity of strength growth increase with increasing soil dispersion, which indicates the influence of the active surface of soil particles on the physicochemical processes of interaction between cement and soil. With a cement content of up to 2% - for heavy loams, 4% - for sandy loams, the strength of coagulation bonds exceeds the strength of crystallization ones. The ratio of rigid (crystallization) and flexible (coagulation) bonds in cement soils determines their deformation properties. Consequently, the deformation properties in a soil system with a small introduction of cement will be determined by the strength of the coagulation bonds. Data obtained by A.A. Fedulov when introducing 2% cement into the "soil-stabilizer" ("Status") system, also indicate changes not only in water-colloidal properties, but also in strength characteristics. For example, the water-colloidal forces ∑w at the shear resistance of su-clay converted with the help of a stabilizer and cement (2%) are 0.084 MPa and, accordingly, without cement - 0.078 MPa, with water - 0.051 MPa (Table 2).

table 2

Results of determination of loam strength parameters

Thus, it can be noted that the addition of binders (Portland cement and / or lime) to the soil in relatively small dosages improves some of its physical and mechanical properties: a decrease in plasticity, an increase in bearing capacity. The amount of cement and/or lime introduced in this case is sufficient to ensure the loss of their hydrophilic properties as a result of their interaction with silty and clay fractions of the soil, but not enough to keep the entire mass of soil particles in a coherent system. The result is an improved soil due to the strengthening of coagulation bonds.
By adding surfactant stabilizers, it is possible to regulate the hardening time of cement and soil-cement mixtures, to control the processes of structure formation during soil strengthening. The action of a surfactant depends on its composition and concentration in the mixture. In the work of O.I. Lukyanova, P.A. Rebinder shows a change in the phase composition of the products of C3A hydration in the presence of increasing additions of surfactants - PRS concentrate. Surfactants, being adsorbed on the mineral particles of soil and cement, block potential centers of coagulation and crystallization structure formation in the first phase of hardening of the binder, which contributes to the convergence of the hardening phases and, as a result, leads to a decrease in microfracturing of the material structure and to an increase in its strength.
It has been established that the mineral composition of the clay fraction in the "soil - cement - surfactant" system has a significant effect on the density and hardening of the soil. The resulting clay microcomposites, together with framework minerals, act as filler and microfiller in the formation of soil cement. Cryptocrystalline (X-ray amorphous) aluminosilicate phases are an active pozzolanic component that binds free portlandite over long periods of hardening.
To strengthen clay waterlogged soils, the moisture content of which is 4-6% higher than the optimum, the use of quicklime is effective. When lime is introduced into the “soil-stabilizer” system, in addition to its main function as a binder, it performs the function of a granulometric additive carrier, which allows the stabilizer to be evenly distributed in the soil. All this creates conditions for high-quality laying of the mixture and its compaction. So the greatest effect can be achieved by strengthening heavy loams and clays. In the complex system "soil - stabilizer - lime", crystallization and coagulation structures are formed simultaneously. The presence of a stabilizer in such a system makes it possible to control the rate of crystallization and the rate of formation of nuclei of crystals of hydrosilicates of the tobermorite group, since the components of the stabilizer - surfactant, due to adsorption on the surface of the nuclei, can prevent their growth.
The action of surfactants is always associated with the formation of structures in the surface layers of clay particles and the volumes of the dispersed medium adjacent to them. A consequence arising from thermodynamics is that it is surfactants that have the ability to accumulate in excess at the interface and thus, as it were, condense into thin layer. The surfactant adsorption layer has an extremely small thickness; therefore, even very small additions of surfactant can drastically change the conditions of molecular interaction at the interface. A rational technology for the use of stabilizers is one in which the conditions necessary to achieve the surfactant of the corresponding surfaces are created. To obtain the desired result, the amount of surfactant must be optimal. If the amount of stabilizer is more than optimal, then the adsorption of surfactant leads to a decrease in the strength of the relationship between the particles. In addition, as F.D. Ovcharenko, the same concentration of surfactants in an aqueous solution for clay soils of different mineral composition can also have the opposite effect.
Study work analysis various kinds construction allows us to note that the introduction of stabilizers into clay soils improves their density, compressive and tensile strength, elasticity modulus, frost resistance, reduces the optimum humidity, capillary dewatering, heaving and swelling. Thus, it has been established that the soaking rate of untreated loam is 1.5-2 times higher than that of treated with Status and Roadbond stabilizers. The total value of the deformation of frost heaving of the clay soil treated by them is respectively 15% and 35% less than that of the untreated soil. Consequently, the processing of clay soils during their compaction leads to a decrease in the total deformation of frost heaving.
An experiment on the construction of experimental sections of roads with foundations made of heavy loams with organic binders (7-8%), treated with the Status stabilizer and cement (6%), showed that the total deformation modulus, determined by the dynamic stamp method, doubles . In clay soils treated with the Status stabilizer, the specific cohesion Cw increases due to a significant increase in water-colloidal forces ∑w (5 times in a sandy loam sample and almost 2 times in a loam sample) (Table 2). The introduction of a stabilizer together with a binder makes it possible to increase both the friction angle φw and the adhesion force Cw.
Due to the fact that many modern stabilizers have an acid reaction due to the content of sulfuric and sulfonic acids in their composition, it is advisable to introduce organic binders in the form of carbamide resin with a hardener. This, in turn, provides a significant increase in the water resistance and strength of the treated soil, as well as an increase in the number of soil varieties to be processed.
Lime used together with surfactants can be considered as a promising complex additive. The introduction of a small amount of lime or cement (up to 2%) into the “soil-stabilizer” system improves all the acquired soil properties by more than 2 times. For example, the strength of samples of capillary-water-saturated stabilized sandy loam (LBS - 0.01%) increases from 4.5 to 15.5-18.8 kg / cm2, depending on the binder, and after 10 freeze-thaw cycles - up to 14 .7-22.0 kg/cm2. For waterlogged soils, quicklime is most effective.
The use of complex methods for strengthening soils with a high content of binders shows their high efficiency (Table 3). For example, the strength after 10 freeze-thaw cycles of capillary-water-saturated samples can reach high values ​​in the range of 22.6-30 kg / cm2, depending on the composition of the soil and the amount of binder (4-8%). The use of complex methods makes it possible to strengthen heavy loams and clays.
Studies conducted by SoyuzdorNII specialists to study the effect of complex binders (M10 + 50 and cement in an amount of 6 to 10%) on the properties of sandy loamy soils showed the following results. The tensile strength of specimens in bending increases by 36.3-40.8%, the values ​​of the stiffness coefficient decrease by 27.5-36.5%. The introduction of surfactants into a complex system improves the physical and mechanical characteristics of soils in comparison with samples strengthened only with cement (Fig. 1).
At the same time, the shear resistance of the reinforced soil increases several times, which makes such soil optimal for the construction of temporary runways and highways, both in the construction of the base and as a coating. This is most relevant when performing road repair work using the “cold recycling” method when constructing the top layer of the base of the pavement or the bottom layer of the pavement. The results of such soil stabilization are significantly superior to bitumen emulsions or cements commonly used for this technology.

Table 3

Physical and mechanical properties of soils,
strengthened through the application of integrated methods

Note: * mixtures are prepared at a natural soil moisture content below the optimum;
** mixtures were prepared at natural soil moisture above the optimum (for waterlogged soil conditions);
n.p. is the plasticity number;
Shchurovsky cement brand M400.

Stabilization of clay soils with Dorzin showed very good results. For a wide range of loams (from light silty to heavy silt) and clays (light silt), the compressive strength corresponds to 4.0-4.3 MPa, and in bending - 0.9-1.4 MPa. Stabilized soils acquire water and frost resistance (F5). The use of stabilization for such soils with the introduction of 2% cement into the system only slightly improves the strength characteristics, on average 4.3-4.6 MPa, but sharply increases water and frost resistance (F10). This, in turn, makes it possible to reduce the amount of cement in cement soils without changing the strength characteristics.

The optimal amount of cement when it is introduced into the clay soil stabilized by Dorzin is 6-8%. This makes it possible to obtain strength indicators for the studied clay soils, corresponding to the strength grades M40-M60 and frost resistance - F10-F25, determined in accordance with. The combined use of surfactants and inorganic binders in the performance of road construction works to strengthen the soil of pavement bases makes it possible to reduce the amount of binder by 30-40% compared to additive-free compositions without changing their strength characteristics. different effect from the introduction of stabilizers into cohesive soils is determined both by the composition of soils, stabilizers, binders (when using complex methods), and their quantity.
The use of complex methods for the transformation of cohesive soils can significantly improve their physical, mechanical and water-physical characteristics compared to conventional stabilization.
Thus, when a stabilizer and a binder are introduced into clay soil, physicochemical and colloidal processes begin to proceed already at the first stages with weak mechanical influences (soil mixing). Ion exchange, adsorption, coagulation of the finely dispersed part of the soil are supplemented by chemical processes (pozzolanic reactions), as a result of which calcium hydrosilicates and other compounds are formed, which additionally cause a change in soil properties. Therefore, surfactants, which are part of the stabilizers, make it possible to regulate the processes of structure formation in complex systems.
Structure formation in such systems depends on the following parameters:

• composition and properties of cohesive soils;
• quantity and concentration of binder;
• composition and properties of the stabilizer;
• the amount and concentration of the stabilizer.

4. Technologies for stabilization and strengthening of soils

The classification of stabilizers developed for road construction takes into account the accumulated domestic and foreign experience in the use of chemical additives (stabilizers) and binders. It is noted that in relation to the domestic practice of road construction, the following existing technologies should be distinguished: stabilization, integrated stabilization and integrated soil strengthening.
Soil stabilization technology is recommended for use for soils laid in the working layer of the subgrade, since the most intensive processes of the water-thermal regime (WTR) and moisture transfer mainly affect upper part earthen bed of the road structure. At the same time, the stabilization of soils in the working layer not only favorably affects the WTR, but also makes it possible to use local clayey soils that were not previously suitable for these purposes (Fig. 2). This becomes possible by improving their water-physical characteristics in terms of water permeability (GOST 25584-90), heaving (GOST 28622-90), swelling (GOST 24143-80) and soaking (GOST 5180-84) to the required values. The main function of this technology is the hydrophobization of soils in the working layer or lower layers of pavement bases.

The technology of integrated soil stabilization differs from the technology of soil stabilization in that clay soils are treated with stabilizers and inorganic binders in an amount not exceeding 2% by weight of the soil. The use of this technology makes it possible to improve the water-physical and physical-mechanical properties of the treated soils by strengthening bonds that have a water-colloidal nature. An increase in the strength and deformation characteristics of complexly stabilized clay soils makes it possible to use them not only for the working layer, but also for roadsides, as well as soil bases for pavements and coatings of local (rural) roads. The main function of this technology is the structuring and hydrophobization of soils in pavement bases.
The technology of integrated soil strengthening is a technology in which a small amount (up to 0.1%) of surfactants and binders are introduced into the soil - more than 2% (by weight of the soil). The presence of stabilizers in the reinforced clay soil leads to a decrease in the required binder consumption and makes it possible to increase the frost resistance and crack resistance of the reinforced soils (Fig. 3). The main function of this technology is to increase the frost resistance and crack resistance of reinforced soils in the structural layers of pavements.

FINDINGS

Structurization of the clay component of cohesive soils when interacting with stabilizers is due to the blocking of active hydrophilic centers of dispersed minerals, which leads to a decrease in the specific surface area, cationic capacity and an increase in soil hydrophobicity.
The impact of surfactants on cohesive soils leads to a complete exchange of cations. For surfactants, it is better to use carbonate soils, in which the interaction of negatively charged organic stabilizer anions with cations of the mineral soil surface (Ca2+, Al3+, Si4+, etc.) can be more noticeable.
When stabilizing soils, the amount of stabilizer introduced into the soil should be optimal to obtain the desired result.
According to their effect on clay soils, stabilizers can be divided into “stabilizers-water repellents” and “stabilizers-strengtheners”.
The introduction of "stabilizers-water repellents" into cohesive soils improves their water-physical properties. The expediency and efficiency of their use are determined mainly by the reduction of heaving processes during soil freezing.
The transformation of clay soils with the help of "stabilizers-strengtheners" contributes to a significant change in their physical, mechanical and water-physical parameters. The ultimate strength in compression can reach 4.3 MPa, in bending - 1.4 MPa. Stabilized soils are water and frost resistant.
The introduction of mineral binders in small dosages (up to 2% for heavy loams, 4% for sandy loams) into the “soil-stabilizer” system improves its physical, mechanical and water-physical characteristics compared to conventional stabilization.
The main difference between the two types of stabilizers is the instability of soils treated with "water repellent stabilizers" in the aquatic environment. Such an amount (2-4%) of cement or lime introduced into the system is sufficient to ensure that, as a result of interaction with silty and clay fractions of the soil, they lose their hydrophilic properties, but not enough to keep the entire mass of soil particles in a coherent system for by strengthening coagulation bonds.
In the complex system "soil-stabilizer-binder" all components take part in structure formation. Physical, chemical and chemical processes during the mixing of binder with water are of significant importance, since the process of creating the crystalline structure of neoplasms occurs in parallel with the formation of the structure of the complexly transformed soil.
The different effect of surfactant stabilizers in a complex system is due to their chemical composition and different selective adsorption in relation to the clinker minerals of the binder and soil minerals.
Complex methods of strengthening soils make it possible to ensure their strength in compression up to 7.0 MPa, in bending - up to 2.0 MPa, which corresponds to the strength grade M60, the frost resistance grade - up to F25.
In a complex system, the screening role of stabilizers on the rate of crystallization of mineral binders contributes to the formation of an organo-clay composite, which imparts elastic properties to the transformed soils.

L I T E R A T U R A

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2. Kulchitsky L.I., Usyarov O.G. Physico-chemical bases for the formation of the properties of clayey rocks / L.I. Kulchitsky, O.G. Usyarov. – M.: Nedra, 1981. – 178 p.
3. Kruglitsky N.N. Physico-chemical bases for regulating the properties of dispersions of clay soils / N.N. Kruglitsky. - Kyiv: Naukova Dumka, 1968. - 320 p.
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Soil stabilization is the process of creating the base of the roadway, which includes thorough grinding of the soil, mixing it with organic and inorganic binders and subsequent compaction. This is a modern, relatively new method of preparing the road base. Such strengthening of the soil has its advantages over the classic (sand-gravel cushion). Stabilized soil is more frost and water resistant, as well as more durable and resilient.

Service	Type of equipment	Characteristics		Price for 1m2 (including VAT), rub.
		depth/volume	width, mm	up to 3 thousand m2	up to 5 thousand m2	5-10 thousand m2	10-20 thousand m2	20-30 thousand m2
Recycling	Recycler Wirtgen WR 2000	up to 500 mm	2000	120	110	100	90	80
Recycling	Regenerator Mixer Caterpillar RM300	up to 500 mm	2400	120	110	100	90	80
Recycling	Stabilization cutter SBF 24 L	up to 400 mm	2400	80	70	60	50	50
	Dry mix spreader SW 10 TA	10 m3	2450	10	10	10	10	10
Distribution of binders	Dry mix distributor SBS 3000	3 m3	2400	5	5	5	5	5
Distribution of binders	Dry mix distributor SBS 6000	6 m3	2400	5	5	5	5	5

Thanks to the possibilities modern equipment the binder is dosed very precisely and injected to a depth of 50 cm in one pass. The most accessible materials today are lime and cement. The optimal amount of these substances is determined by laboratory methods, usually it is 3 - 10% of each material by weight of the earth to be strengthened. The first stage of stabilization is the introduction of lime into the soil and mixing with it, the second - cement.

Soil stabilization followed by the use of existing pavement materials is cold recycling. With it, you can restore the entire depth of both country roads and city streets. In other words, in one pass, pulverizing the existing pavement and mixing it with the underlying base material and restorative binders. All this became possible due to the appearance on the market of new high-performance machines.

Stabilization technology is widely used today, for example, on small territorial roads, where lightweight or transitional pavements are supposed to be installed (for example, in the construction of cottage settlements). In such cases, the construction of a solid, durable base using a minimum of imported materials is the best solution. In addition, high-performance equipment can produce tens of kilometers of roads during the construction season. Also, compaction (recycling) is successfully used in the construction of logistics complexes, industrial buildings. Here, this technology is used to lay foundations for concrete floors and cover production sites.

Stabilization works cannot be performed efficiently without the use of special equipment. For the dosed introduction of a binder (dry or in the form of an emulsion), a hopper-distributor is needed, for thorough mixing it into the soil - hinged cutters.

In order for our specialists to calculate the cost of the recycling service and to be able to choose the right necessary equipment for you, you need to have the following information: what object and where it is located, its area in sq. m, the timing of work, as well as what soils prevail on the ground, what depth of distribution is needed and what binders are desirable.