Thixotropic transformations are physical and chemical phenomena associated with mechanical effects on soils. As a result of such influences - shaking, crumpling, vibrations, etc. - two successive processes arise - softening and hardening. The processes of softening are the result of mechanical influences and proceed very quickly. Upon the termination of the external influence, the reverse process immediately begins - the strengthening of the soil. Hardening is a slower process and proceeds at an unequal rate. At first, this recovery is relatively fast, and then slows down. To take into account the phenomena of thixotropy when designing a subgrade, it is necessary to know under what soils, their conditions and the nature of mechanical influences, thixotropic softening becomes especially dangerous, and also whether the hardening process is completely reversible, i.e. whether it goes to the end, and if it does , then after what time it is possible to count on the complete restoration of the initial properties of soils. Unfortunately, at the present stage of research, it is still impossible to give an exhaustive answer to the questions posed; nevertheless, the available material allows us to give some recommendations.
G. Freindlich found that thixotropy manifests itself in soils in which the content of clay particles exceeds 2%. An opinion is expressed that all clay soils are potentially thixotropic, but certain conditions are necessary for a specific manifestation of thixotropy, and, first of all, rather intense external influences. Obviously, not only the tendency of soils to thixotropic transformations, but also the size of these transformations, should be taken into account. In this case, such transformations should not be allowed, in which the decrease in strength and resistance to deformation becomes already dangerous.
Studies suggest that the tendency of soils to thixotropy is determined by its nature, condition, as well as the intensity and nature of external influences. The nature of soils, first of all, is understood as their granulometric composition and the mineralogical composition of the clay fraction.
Most researchers believe that the tendency of soils to thixotropy depends on the content of clay particles in them. Moreover, the greater the amount of these particles the soil contains, the less its tendency to thixotropic decrease in strength. AI Lagoisky explains this by the fact that with a low content of clay particles there is a relatively small number of bonds between soil particles and aggregates. With a large number of clay particles, a rigid framework is formed, which is more difficult to destroy, although the potential for this increases.

To determine not only the qualitative, but also the quantitative side of the influence of the content of clay particles in soils on thixotropic transformations, experiments were carried out. Thixotropic softening was studied under single impact shaking of the soil and under vibration loads (Fig. 17). The thixotropic softening under a single impact was estimated from the change in the ultrasonic wave propagation velocity. In doing so, the following indicator was adopted:

where v1 and v2 are the ultrasonic wave propagation velocities measured before and after the impact, respectively.
Under vibration exposure, for this purpose, the indicator was adopted

where E01 and E02 are soil deformation moduli measured before vibration and during vibration exposure.
From fig. 17, it can be concluded that sandy loamy soils with a content of clay particles of 3-7%, as well as silty soils, are subject to the greatest thixotropic transformations. Under vibrational influences, the resistance of the soil to external loads can be lost by 60 and even 90%. Thus, under unfavorable conditions, an almost complete loss of resistance of these soils to external loads can occur. The given data refer to soils, the moisture content of which exceeds the optimal values ​​(W=1.2/1.3W0).
With an increase in the content of clay particles in soils, their tendency to thixotropic transformations, in general, decreases. However, with a certain amount of clay particles, the intensity of thixotropic transformations increases again. In this case, this refers to clay soil containing 26% clay particles; a similar phenomenon was observed in experiments conducted by G. I. Zhinkin and L. P. Zarubina, where heavy loam with a content of clay particles of 20% turned out to be such a soil.
From fig. 17 shows that vibration impacts are more dangerous than single impacts. During impacts, with an increase in the content of clay particles in soils, thixotropic softening decreases monotonously and, therefore, for loams and especially heavy ones, it is practically no longer dangerous. Vibration effects can also be dangerous for heavy soils.
Apparently, the mineralogical composition of the clay fraction of soils does not have a decisive influence on the degree of thixotropic softening of soils. Some researchers believe that the ability of montmorillonite to undergo thixotropic transformations is more pronounced than that of kaolinite and hydromicas. There is also an opinion according to which the largest thixotropic transformations correspond to kaolinite soils, and the smallest to montmorillonite. Hydromica occupies an intermediate position.
Thixotropic transformations are influenced by the density of soils. The experiments made it possible to conclude that soils whose density is in the range (0.85-0.93)δmax are subject to the greatest thixotropic transformations. In looser and denser soils, the tendency to thixotropic transformations is markedly reduced. Soil moisture has a great influence on thixotropic transformations (Fig. 18). When the humidity is less than optimal and equal to it, thixotropic transformations are observed only in sandy loams. With an increase in humidity above its optimal value, the intensity of thixotropic transformations noticeably and continuously increases.

With vibration loads, the oscillation frequency is of great importance. By gradually changing the oscillation frequency from zero to several hundred hertz and keeping the intensity of soil shaking unchanged, which is generally characterized by the amplitude values ​​of the acceleration of its particles, we can distinguish two values ​​of the oscillation frequencies at which anomalous phenomena are observed.
When an oscillation exciter with a mass of 2 tons is placed on an embankment at some oscillation frequency determined for the given conditions, which is usually in the range of 12-28 Hz, the exciter oscillation amplitude increases and, in addition, noticeable shaking of the entire soil is observed with the transmission of these shaking to significant distances. Thus, at these frequencies, a phenomenon similar to that which occurs during resonant vibrations of elastic systems is observed. Due to the fact that the soil is a system with high resistance, where vibrations decay very quickly, this phenomenon, in contrast to resonant elastic systems, can be called quasi-resonant. It is interesting to note that at quasi-resonant frequencies there are no large changes in the state and properties of the soil. Thixotropic soil changes also practically do not occur. With such vibrations, the ground is a system with a relatively small attenuation of vibrations, as a result of which they are transmitted over long distances.
The second frequency, characteristic for the given type and condition of the soil, determines the localization of oscillatory movements in a relatively small zone, but, on the other hand, the volume of soil located in this zone undergoes intense thixotropic transformations, which are accompanied by abundant moisture release and, in fact, spontaneous compaction of the soil, which occurs at a very small load, measured in tenths, and sometimes in. hundredths of kgf/cm2. This phenomenon, like the previous one, is observed only with soils whose density is in the range (0.85-0.93) δmax.
Intense thixotropic transformations are observed not at any specific oscillation frequency, but over a wide range of frequencies. This interval turned out to be equal to 175-300 Hz. It refers to soil moisture (1.0-1.3)W0. He also found no clear dependence of this interval on the granulometric composition of soils. Maybe it depends on the load.
The most dangerous for the stability of the subgrade are the frequencies at which intense thixotropic soil transformations occur. However, these frequencies are high and occur very rarely. Obviously, it is advisable to create them during soil compaction, which will lead to obtaining the required density at the lowest cost of mechanical work.
During the period of road operation, the frequency of application of an external load close to quasi-resonant one can occur only by chance, therefore, in most cases, one has to deal with loads at which oscillation frequencies occur, which are less than quasi-resonant ones in their numerical value, or somewhat exceed them.
The impact on the subgrade soils of dynamic loads that cause oscillatory movements of the soil has not been studied. There are some data related to railways on this subject. If the subgrade is built from moistened clay soils, during the passage of a loaded train with a total mass of 4500-4800 tons, the resulting vibrations can reduce soil shear moduli by 45-48%. When passing at the same speed (70 km / h) of an empty train, the module decreases by 15-20%, and with a passenger, i.e., lighter train, by 8-16%. Thus, there is a dependence of thixotropic transformations of soils on the intensity of the impact, which in this case is determined by the mass of the moving train. Apparently, the same phenomenon occurs on highways when cars are moving. Obviously, the occurrence of vibrations in soils is facilitated by the oscillatory movements of the sprung masses and the total mass of the vehicle as a result of the elasticity of the springs and tires. The unevenness of the road surface contributes to the occurrence of such vibrations.
Of great practical interest is the restoration of the initial state of the soil, i.e., the process of thixotropic hardening. It turned out that after the passage of the train, this process goes to the end, i.e., the initial properties of the soil are completely restored. Recovery occurs quickly at first, and then slowly. The initial value of the shear modulus is restored in 60-70 minutes. If the frequency of train movement is less than this time, then residual deformations may occur.
There is heavy traffic on the main roads, so thixotropic soil changes lead to residual deformations of the soil, and, consequently, to deformations of road surfaces. When driving cars, thixotropic soil transformations are always observed. However, it is important that they do not go beyond acceptable limits. In practice, they no longer affect the stability of soils in cases where soils are compacted to a density exceeding 0.93δmax, and when their moisture content is not higher than the optimum value. Therefore, thorough compaction of soils and prevention of moisture in them is a very effective means of reducing thixotropic softening. When at least one of these conditions is not met, in order to avoid the destruction of road surfaces associated with intense soil moisture, it is necessary to limit or completely close the movement of cars.

Thixotropy (thixotropy) (from the Greek. θίξις - touch and τροπή - change) - the ability of a substance to reduce viscosity (thinn) from mechanical action and increase viscosity (thicken) at rest.

Thixotropic liquids

Thixotropy should not be confused with pseudoplasticity. For pseudoplastic liquids, the viscosity decreases with increasing shear stress, while for thixotropic liquids the viscosity decreases with time at constant shear stress.

Thixotropic fluids are fluids in which, at a constant strain rate, the shear stress decreases with time.

The viscosity of some fluids under constant ambient conditions and shear rate changes with time. If the viscosity of the liquid decreases with time, then the liquid is called thixotropic, if it increases - reopex.

Both behaviors can occur both together with the above types of fluid flow, and only at certain shear rates. The time interval can vary greatly for different substances: some materials reach a constant value in a matter of seconds, others in a few days. Reopex materials are quite rare, unlike thixotropic materials, which include lubricants, viscous printing inks, and paints.

Special purpose mortars are often used to repair concrete. They are characterized by high weather resistance and can be used on artificial stone operating under harsh conditions (facades, tunnels, parking lots). One of these solutions are thixotropic mixtures, the characteristics and principle of use of which will be discussed below.

Artificial stone can be affected by mechanical loads (vibration, shock, etc.), physical (wear, shrinkage, freezing and thawing, temperature fluctuations, salt crystallization).

Strongly weaken the structure of chemical loads. Due to the capillary-porous structure, alkalis and sulfates, salt solutions are able to penetrate into the thickness of the concrete and ultimately affect its bearing capacity. If the structure could not withstand the loads and requires repair, the choice of the working composition is based on an assessment of its condition and the causes of damage.

The reasons for the destruction of concrete are very diverse, but they all inevitably lead to the need for repair.

Thixotropic mixtures - what is it

Thixotropic repair mortar for concrete is a dry mix based on high-strength cement, mineral aggregate, modifying additives. Unlike other cement analogues, the mixture contains a reinforcing fiber. When mixed with water, the material forms a high-strength solution that does not shrink. It is effective in repairing and restoring horizontal and vertical surfaces of damaged concrete structures.

Scope of application

The material is intended for professional and non-professional use.

In professional repairs, thixotropic compounds are used in the following cases:

• structural repair and restoration destroyed concrete structures, including due to corrosion of reinforcement (beams, edges, columns). Elimination of defects made during construction or those that arose during operation;
• protective layer repair, filling of hard joints, elimination of surface defects (new pouring joints, gravel pockets, open reinforcement, traces of formwork removal);
• wall alignment, building envelopes;
• foundation repair, under strong abrasive loads, reinforced concrete structures of hydraulic structures;
• waterproofing works on the roof, in basements, concrete tanks and trays;
• foundation pouring and monolithic housing construction, monolithic prefabricated concrete structures;
• flooring repair industrial structures under heavy mechanical loads and under the influence of aggressive environments;
• boiler repair, CHP, chimneys, bridges, viaducts.

In the private sector, thixotropic mixtures are used to repair concrete screeds, floors, paths, wells, stairs, steps, basements, vegetable pits. The material is successfully used for sealing strobes, cracks, repairing garages, concrete slabs for various purposes.

In general, the solution is effective in the repair and restoration of any concrete or reinforced concrete structures subject to static and dynamic loads. They work at civil and transport construction sites, at hydraulic structures.

Specifications

Repair thixotropic mixture is a ready-to-cook powder with a specially developed recipe. When mixed with water, it turns into a working solution with high thixotropy. This allows it to be used on vertical surfaces without slipping without formwork. The material can be applied in thick layers.

After curing, the composition is characterized by the following properties:

• water resistance;
• high compressive and flexural strength;
• good adhesion to old concrete, rebar;
• thermal expansion, vapor permeability, modulus of elasticity almost completely correspond to those of high-quality concrete;
• abrasion resistance.

However, thixotropic mixtures have a number of limitations in their use. They do not work on smooth surfaces (roughness should be provided), if necessary, reinforcement is introduced. The material cannot be used for anchoring and pouring into formwork.

The application of thixotropic mixtures is realized only at t above 5 degrees.

The disadvantages include such a property of thixotropic solutions as the need for care. The material exhibits all the declared characteristics only when applied in conditions of humidity or when sprayed with water. This ensures that all product properties are revealed correctly. This is not easy to achieve in a construction site environment.

Typical technical data

Consistency and color	gray powder
Volume weight	1250 kg/cu.m.
Maximum filler multiplicity	2.5mm
Dry residue	100%
Blending options	100 parts dry powder to 16-17 parts water
Plastic deformation	70%
Density	2150 kg/cu.m.
pH	12.5
Working temperature	+5 +35 degrees
Viability	60 minutes
Layered exposure	4 hours
Maximum thickness of one layer	30-35mm
Compressive strength	60 N/mm2 after 28 days
Bending strength	8.5 N/mm2 after 28 days
Peel strength	2 N/mm2 after 28 days
Elastic coefficient	25,000 N/mm2

Tools, equipment and fixtures for thixotropic concrete repair

For the implementation of repair work, electrical professional equipment and hand tools will be required.

The following set of equipment must be present on the site:

• surface preparation equipment: grinders, grinders, construction vacuum cleaners, compressors, high-pressure cleaners, sandblasters, perforators, jackhammers;
• tool: trowels, shovels, spatulas, chisels, drills with mixing nozzles, brushes, metal brushes;
• measuring instruments: to determine the strength of concrete, the viscosity of working solutions, to search for reinforcement, thermometers;
• polyethylene film to protect the finished layer;
• overalls, personal protective equipment.

Foundation preparation

Thixotropic mixtures are most often used for structural repairs of concrete, that is, to restore its bearing capacity.

In view of this, special requirements are imposed on concrete and reinforced concrete surfaces:

• strength, ability to bear the load (bearing capacity);
• absence of exfoliating, destroyed layers;
• absence of contaminants that adversely affect adhesion (fats, oils, dirt, dust, rust, paint);
• rough texture.

All weak parts of the base are removed flesh down to solid structural concrete. Any compositions left over from previous work must also be removed. Reinforcing rods and the concrete itself are processed. The work is carried out until the elements are freed from cement laitance, dirt, oils, fats, paints and varnishes.

The hydraulic cleaning method is unsuitable where an increase in air humidity is unacceptable.

Base cleaning methods:

• mechanical- for jointing cracks, defects, jackhammers, perforators, picks, pneumatic hammers are used. Cleaning is carried out by sandblasting, shot-blasting installations, grinders and high-pressure apparatuses. This is a universal method of preparation, which is advisable to use in all cases, regardless of how much and how the concrete is damaged. However, the technique is not applied where dustiness is unacceptable;
• thermal- is realized with the help of special burners. For concrete, heating is allowed no higher than 90 degrees. The thermal method is effective with a slight depth of damage - up to 5 mm. High temperature allows you to remove traces of oils, rubber, organic compounds. Such processing is always followed by mechanical or hydraulic;
• hydraulic- use hydraulic installations and high-pressure apparatuses. It is a one-stop solution for efficient and fast concrete cleaning;
• chemical- for the preparation of concrete using special chemical compositions. The method can help out where it is impossible to carry out mechanical cleaning. After pickling, substrates are always rinsed with water.

If defective concrete is found at the work site, it must be cut down with concrete breakers, chippers or perforators. All loose layers with insufficient thickness, structural damage, peeling coatings are subject to removal.

Before applying the thixotropic mortar, the substrate is saturated with water.. The surface should be damp, but without puddles. If accumulations of liquid are found, they are removed with a sponge or compressed air. In some cases, the working solution is applied to a dry primer layer.

Application of adhesive primer

The material is also applied to a moist base. If the concrete absorbs moisture well, wetting is implemented repeatedly. A well-prepared surface should be damp but not glossy.

Application principle:

• the soil is spread by the method of wet shotting or brushes of medium hardness;
• during operation, the filling of pores and irregularities of the base is controlled;
• a thixotropic repair compound is applied to a wet primer. But, if the surface has had time to dry, another fresh layer of soil is implemented.

If corrosion protection is required

In accordance with GOST 31384-2008, GOST 32016-2012, it is necessary to provide long-term anti-corrosion and passivation (inactivity) of steel reinforcement. At the first stage of protection, the reinforcing bars are cleaned. According to GOST RISO 8501-1-2014, newly installed or old fittings must be cleaned to Sa 2 ½. Works are carried out manually or with metal brushes. A mechanized method can be used by means of sandblasting machines.

Ideally, the depth of the joint should be 3-4 times the width of the joint.

If there is damaged concrete in the work area, it is removed along with the rebar. The use of perforators and jackhammers is unacceptable, as this may lead to a decrease in the adhesion of concrete and reinforcement. Opened reinforcing bars are completely exposed. The gap between steel and concrete must be at least 20 mm. If the diameter of the rods is small (up to 5 mm), a smaller gap of 10 mm is acceptable.

Applying protection:

• an anti-corrosion compound is applied to the cleaned fittings in two passes. When working, use a brush of medium hardness or the method of shotting (wet). The thickness of the first layer should be 1 mm. When the first layer begins to set, immediately implement a second identical thickness;
• edges, reinforcement-concrete transition zones, wire fastenings are especially carefully processed;
• if the first layer had time to fully seize before applying the second, arrange another fresh layer.

Liquidation of active leaks

At this stage, the task is to waterproof the structure and eliminate active leaks. If pressure leaks are found on the surface, they are eliminated with hydraulic seals (quick-setting waterproofing compounds). Such materials are capable of hardening under liquid pressure for 1 min.

Additional surface preparation is required here:

• areas of active leaks are embroidered. During operation, the gap is expanded inside the structure to a depth of at least 3 cm, a width of 2 cm. The cavity is washed with water;
• the base is cleaned by sandblasting or high-pressure cleaners.

When liquidating a leak, a hydraulic seal is formed on the basis of a fast-hardening mixture. The material should take the form of a truncated cone or ball. After that, it is pressed with force into the zone of active leakage for 3-5 minutes. If the waterproofing area is large, they work with it in several steps.

If the leak is characterized by high intensity, a drainage polyethylene tube is inserted into the repaired area, which will allow localizing water drainage. The area around the pipe is treated with a hydraulic seal. When the material has hardened, the tube is removed by caulking the hole with a quick setting compound.

Application of thixotropic mortar

If the surface is well prepared, characterized by a rough texture, and does not require a primer, it is pre-moistened. In all other cases, a range of operations discussed above is carried out. In any case, the concrete must be damp but free of gloss before applying the base mortar.

The thickness of the applied solution can vary from 6 to 35 mm

Proper preparation of the solution:

• the required number of bags is opened immediately before mixing;
• a small amount of water is poured into the mixer. For 25 kg of dry mix, 3.9-4.0 liters of water are required;
• the equipment is turned on, after which dry powder is continuously poured into the mixer;
• the composition is mixed for 1-2 minutes until it becomes homogeneous;
• if required, a small amount of water is added, the solution is re-mixed for 2-3 minutes;
• to reduce the risk of shrinkage, it is recommended to use a moisture-retaining additive during mixing;
• for mixing a small amount of mortar, it is permissible to use not a concrete mixer, but a clean container and a drill with a paddle nozzle. With this method, mixing is implemented for 5-6 minutes;
• the viability of the solution, regardless of the preparation method, is 60 minutes. To prepare 1 m3 of the working mixture, 1800 kg of dry thixotropic powder will be required.

The need for a solution in water is indicated in the table.

Manufacturing jobs

The solution is spread on horizontal and vertical surfaces manually using a spatula, trowel or trowel or using the wet shotting technique. In this case, the layer is smoothed.

If the working conditions are such that it is required to realize a layer over 35 mm in thickness, the thixotropic mortar is applied in two approaches. The second and all subsequent layers are realized when the previous one has seized, but has not completely hardened..

When applying a layer with a thickness of more than 50 mm, reinforcement is necessary.

The network is set up like this:

• the gap between the reinforcement and the base should be 10 mm;
• the thickness of the protective layer above the mesh cannot be less than 10 mm.

If a mechanized method (spraying) is used, special equipment is used. After completion of work, both equipment and tools are washed with water.

Surface care

When thixotropic repairs are completed, surfaces must be protected from premature moisture loss for 24 hours. If the weather is dry and windy, the protection period is extended to two days.

Care is implemented in several ways:

• water is sprayed onto the repaired base;
• the surface is covered with wet burlap or plastic wrap;
• a film-forming composition is applied to the concrete.

Quality control

Control is carried out by external inspection

After three days after the repair, the quality of the work performed is checked. There should be no visible peeling or cracks on the surface. If such defects are found, this indicates errors in the application of the material. It is necessary to carry out repeated repairs.

If a deeper check is required, a method is used to assess the adhesion strength, compressive strength, and the concrete water resistance grades are also determined.

Safety

Dry thixotropic compounds contain cement. The material may cause irritation to mucous membranes and skin. Avoid contact with eyes and skin contact. If this happens, the affected areas are thoroughly washed with water, then consult a doctor.

Persons under the age of 18 are allowed to work. All personnel must undergo a medical examination, training, safety briefing. If work at height is expected, ladders and scaffolds are used.

Cost of thixotropic concrete repair

Thixotropic mixtures are offered by manufacturers such as BASF, MAPEI. The average cost of a bag weighing 30 kg starts from 1.9 thousand rubles. The cost of concrete repair works starts from 2.5 thousand rubles per m3.

conclusions

Modern thixotropic mixtures can be confidently used for repairing and leveling concrete structures. The material is easy to use, presented at an affordable cost, easy to apply even on vertical surfaces. The only limitation you may encounter is work is possible at temperatures above +5 degrees. If you want to eliminate the defect in the winter, it is better to turn to polymer compositions.

Details of concrete repair with Profscreen thixotropic composition are shown in the video:

Thixotropy is a concept, perhaps not widely known, but found everywhere. Paints, printing inks, bearing grease, many foodstuffs - all of these substances have certain viscous properties that change over time. There can be two options: either the substance begins to flow, that is, the viscosity decreases, or it solidifies - the viscosity increases. The first phenomenon is called thixotropy, the second is called rheopexy. Thixotropy is characteristic of polymer and disperse systems under mechanical action under isothermal conditions. Scientifically speaking, this is the ability of a substance to restore its yield strength after the cessation of exposure (shaking, stirring, vibration, etc.). The phenomenon of thixotropy is explained by the possibility of reversible changes within the structure of the material, for example, during the destruction of the supramolecular structure in polymers or coagulation of colloidal particles inside the disperse system.

What determines thixotropic properties

Thixotropic properties are determined by the qualitative and quantitative composition of the dispersed phase of the substance (thickener in grease) and are characterized by the values ​​of three parameters: the highest effective viscosity, the lowest effective viscosity, and the ultimate shear stress.

The thixotropy of colloidal systems is of great importance and is widely used in industry, in production and in everyday life. So thixotropic properties to a greater or lesser extent must have greases, paint, flushing solutions for drilling wells, many food products.

Thixotropy should not be confused with the concept of pseudoplasticity. Pseudoplastic substances lose their viscosity under temporary shear stress, thixotropic substances are constantly affected and lose their viscous properties over time.

Bearing grease and its thixotropic properties

Bearing grease is one example of a dispersion system characterized by high thixotropic properties, which, together with the viscosity and shear strength parameters, determine the rheological properties of lubricating greases. Rheology - the science of flow, studies the ability of liquid and plastic materials to flow and deform. The fact that greases can change their structure reversibly is decisive for their use in lossless vertical and inclined friction units. After all, if the bearing is lubricated with liquid oil, you need to constantly monitor its amount: it can leak, evaporate and requires frequent application. Grease fills the bearing cavity, seals the assembly and prevents the penetration of abrasive particles into the bearing, which can lead to seizing of the mechanism. The thixotropic properties provide a stable protective film between work surfaces that cushions vibration shocks and reduces the effects of wear from sliding friction.

Bearing grease is used in more than 90% of rolling bearings. When stuffing grease into the cavity of a part operating at high speeds, the necessary proportions must be observed. Bearings with a speed of up to 1500 rpm are filled to 2/3, over 1500 rpm - to 1/3 of the free volume. If excess grease is visible, it must be removed.

THIXOTROPY

THIXOTROPY

The ability of certain dispersed systems to reversibly liquefy with sufficiently intense mechanical influences (mixing, shaking) and harden (lose) when at rest. T. is a characteristic property of coagulation. structures that can be destroyed an unlimited number of times, and each time their properties are completely restored. Examples of typical thixotropic structures are systems formed during the coagulation of aqueous colloidal dispersions of iron hydroxide, aluminum hydroxide, vanadium pentoxide, suspensions of bentonite, kaolin.

Mechanical the properties of thixotropic structures are characterized by the values ​​of three parameters (P. A. Rebinder): the highest eff. viscosity h 0 practically intact structure, the smallest eff. viscosity h m ultimate fracture structure and ultimate shear stress P 0 . Dependence eff. viscosity h on the applied shear stress P can be described by equation

For small values P, which do not disturb the rest or cause a very slow flow, the structure has the properties of a solid body, since its recovery under these conditions exceeds the rate of destruction. At R>>R 0, the system turns out to be extremely destroyed and represents itself with a low viscosity h m. Value P 0 characterizes the undestroyed structure. The process of restoring a destroyed structure at rest can be characterized by an increase in strength over time.

In some cases, the application of small P and deformation at low speed accelerate the increase in strength and structuring of disperse systems; this phenomenon is called r e o p e x and e y. Sometimes in concentrated dispersed systems (pastes) dilatation is found - an increase in h with an increase in the rate of deformation, accompanied by a certain increase in the volume occupied by the system: during deformation, solid particles form a looser frame and the existing liquid medium turns out to be not enough to provide the system with .

T. disperse systems has a large practical. meaning. Thixotropic properties must have greases, paints, ceramics. masses, flushing, used in drilling wells, pl. food products. I. H. Vlodavets.

Physical encyclopedia. In 5 volumes. - M.: Soviet Encyclopedia. Editor-in-Chief A. M. Prokhorov. 1988 .

Synonyms:

See what "THIXOTROPY" is in other dictionaries:

Thixotropy ... Spelling Dictionary

Thixotropy- - the ability of dispersed systems to restore the original structure destroyed by mechanical action. [Terminological dictionary for concrete and reinforced concrete. Federal State Unitary Enterprise "NRC "Construction" NIIZHB and M. A. A. Gvozdev, Moscow, 2007 110 pages] ... Encyclopedia of terms, definitions and explanations of building materials

- (from the Greek thixis touch and trope turn change), the ability of dispersed systems to restore the original structure destroyed by mechanical action. Thixotropy is an important technological property of flushing fluids used in… Big Encyclopedic Dictionary

Exist., number of synonyms: 1 thixotropy (1) ASIS Synonym Dictionary. V.N. Trishin. 2013 ... Synonym dictionary

The ability (property) of some jellies and gels (gelatin, agar agar, iron hydrate) under mechanical action (shaking, stirring) to liquefy and turn into sols, which in a calm state become gel again. These… … Geological Encyclopedia

thixotropy- The phenomenon of the reversible process of the transition of jellies and gels into a liquid state under mechanical action Topics oil and gas industry EN thixotropy … Technical Translator's Handbook

thixotropy- - the ability to spontaneously restore the structure of gel-like systems after their mechanical destruction. General chemistry: textbook / A. V. Zholnin ... Chemical terms

- (from the Greek thíxis touch and tropē turn, change), the ability of dispersed systems to restore the original structure destroyed by mechanical action. Thixotropy is an important technological property of flushing fluids used ... encyclopedic Dictionary

thixotropy- Thixotropy Thixotropy A reversible change in the physico-mechanical properties of polymer and disperse systems under mechanical action under isothermal conditions. For liquid media, it manifests itself in a decrease in viscosity during flow and its gradual ... ... Explanatory English-Russian Dictionary of Nanotechnology. - M.

It is necessary to transfer the contents of the article Thixotropic liquid to this article and put a redirect from there. You can help the project by merging articles (see merging instructions). If it is necessary to discuss the feasibility ... ... Wikipedia