Thixotropic repair of concrete. Thixotropy In what mode is it better to study thixotropic phenomena?

(from Greek thixis - touch and trope - turn, change * a. thixotropy of rocks; n. Thixotropie der Gesteine; f. thixotropie des roches; i. capacidad tixotropica de rocas, tixtropia de rocas) - a physical and chemical phenomenon occurring in some colloidal disperse systems, for example in cohesive rocks ah, and consists in their spontaneous liquefaction under the influence of mechanical influence (shaking, stirring, vibration, ultrasound, etc.) and the subsequent restoration of the structure when these influences are eliminated. Thixotropy is explained by the reversible softening of structural bonds between mineral particles of cohesive rock. Under a certain mechanical influence, bound and immobilized water transitions into free water, which leads to a decrease in the strength of structural bonds and liquefaction of the rock. Cessation of the impact leads to a reverse transition of water from a free to a bound state and strengthening of the rock (thixotropic strengthening).

An indicator characterizing the tendency of rocks to thixotropic softening is instability. It is usually measured by the average radius of the base of a cylindrical sample (mm) after its vibration at a vibration frequency of 67 Hz and an amplitude of 1 mm. The initial radius of the sample is 8 mm, and the height of the cylinder is 20 mm. The value of the instability index varies from 8-9 for non-thixotropic rocks to 15 or more for highly thixotropic rocks. A more general indicator is the limit structural strength under dynamic influence, defined as the maximum alternating acceleration at which the strength of the rock does not decrease. It is measured in m/s2. Thixotropic hardening is characterized by the recovery time (s) during which the maximum strength of the rock is achieved during recovery.

Thixotropy is determined by the qualitative and quantitative composition of their dispersed phase, the shape of particles and their hydrophilicity, the composition and concentration of pore moisture, etc. The main influence is exerted by the granulometric composition of the rock. Thixotropic phenomena are typical for rocks with a content of clay particles of at least 1.5-2%.

Thixotropy is widespread in nature and has both negative and positive influence on technological processes when mining wet cohesive rocks. For example, when transporting such rocks, thixotropic liquefaction causes intense adhesion to the working surfaces of transport equipment, reducing its productivity by 1.5 times. On the other hand, thixotropy is used when conducting drilling operations and driving piles. Thixotropy is the cause of landslide phenomena.

Thixotropy

Rocks (from the Greek thixis - touch and trope - turn, change * a. thixotropy of rocks; n. Thixotropie der Gesteine; f. thixotropie des roches; And. capacidad tixotropica de rocas, tixtropia de rocas) - physico-chemical.
a phenomenon occurring in certain colloidal disperse systems, for example. in coherent g.p., and consisting in their spontaneous liquefaction under the influence of mechanical. influences (shaking, stirring, vibration, ultrasound, etc.) and subsequent restoration of the structure when these influences are eliminated. T. is explained by the reversible softening of structural bonds between mineral particles of cohesive rock. With a certain mechanical exposure, a transition of bound and immobilized water into free water occurs, which leads to a decrease in the strength of structural bonds and liquefaction of the rock. Cessation of the impact leads to a reverse transition of water from a free to a bound state and strengthening of the rock (thixotropic strengthening).
T. is determined by qualities. and quantities. the composition of their dispersed phase, the shape of particles and their hydrophilicity, the composition and concentration of pore moisture, etc. Main. influence is exerted by granulometric. rock composition. Thixotropic phenomena are typical for rocks with a content of clay particles of at least 1.5-2%.
T. is widespread in nature and has both negative and positive effects. influence on technology processes in the development of wet cohesive rocks. For example, when transporting such rocks, thixotropic liquefaction causes their intense adhesion to the working surfaces of the transport. equipment, reducing its productivity by 1.5 times. On the other hand, T. is used in drilling operations and driving piles. T. is the cause of landslide phenomena. A. V. Dugartsyrenov.

Mountain encyclopedia. - M.: Soviet Encyclopedia. Edited by E. A. Kozlovsky. 1984-1991 .

See what “Thixotropy” is in other dictionaries:

Thixotropy Dictionary of Russian synonyms. thixotropy noun, number of synonyms: 1 thixotropy (1) ASIS Dictionary of Synonyms. V.N. Trishin... Synonym dictionary

Thixotropy- – the ability of paint to reduce viscosity (liquefy) under mechanical stress and increase viscosity (thicken) at rest... Builder's Dictionary

thixotropy- The property of some materials, glue, latexes, etc., to restore their structure destroyed by mechanical action [Terminological dictionary of construction in 12 languages ​​(VNIIIS Gosstroy USSR)] EN thixotropy DE Thixotropie FR thixotropie ...

thixotropy- 3.5 thixotropy: The ability of a solution to thicken at rest, forming a gelatinous gel mass, and to liquefy under mechanical action, turning into a viscous liquid sol. The process can be repeated many times. Source …

The property of some materials, glue, latexes, etc., to restore their structure destroyed by mechanical action (Bulgarian language; Български) thixotropy (Czech language; Čeština) thixotropie; tixotropie ( German; Deutsch)… … Construction dictionary

thixotropy of the petroleum product- Physics chemical property, which determines the change in rheological characteristics at a constant temperature as a result of the destruction of the structural frame of a plastic petroleum product during deformation, as well as further changes in these characteristics... ... Technical Translator's Guide

soil thixotropy- The ability of some soils and soils in a waterlogged state to acquire fluidity under the influence of mechanical influences (shaking, stirring) and again turn into a solid state at rest... Dictionary of Geography

Soil thixotropy- the ability of some soils and soils in a waterlogged state to liquefy (acquire fluidity) under the influence of mechanical influences (shaking, stirring) and again turn into a solid state when left at rest... Dictionary in soil science

STO-GK Transstroy 014-2007: Trench wall in the ground. Design and construction technology for transport construction projects- Terminology STO GC Transstroy 014 2007: Trench wall in the ground. Design and construction technology for transport construction projects: 3.15 VPT: Method of laying concrete using a vertically moved concrete pipe.… … Dictionary-reference book of terms of normative and technical documentation

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

Thixotropic liquids

Thixotropy should not be confused with pseudoplasticity. Pseudoplastic liquids have a viscosity decreases with increasing shear stress, while thixotropic liquids have a viscosity decreases over time at constant shear stress.

Thixotropic liquids are liquids in which, when constant speed deformation, shear stress decreases with time.

The viscosity of some liquids, under constant ambient conditions and shear rate, changes with time. If the viscosity of a liquid decreases over time, then the liquid is called thixotropic, if it increases, it is called rheopex.

Both behaviors can occur both together with the types of fluid flow described above, 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 several days. Reopex materials are quite rare, unlike thixotropic materials, which include lubricants, viscous printing inks, and paints.

Thixotropy is a concept that may not be widely known, but is found everywhere. paints and varnishes, printing ink, bearing grease, many food products– all 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, which means the viscosity increases. The first phenomenon is called thixotropy, the second - rheopexy. Thixotropy is characteristic of polymer and dispersed systems under mechanical action under isothermal conditions. Scientifically speaking, this is the ability of a substance to restore its yield strength after 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 the coagulation of colloidal particles within a disperse system.

What determines thixotropic properties

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

Thixotropy of colloidal systems has great importance and is widely used in industry, production and everyday life. Thus, lubricants, paint, washing solutions for drilling wells, and many food products should have thixotropic properties to a greater or lesser extent.

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

Bearing grease and its thixotropic properties

Bearing grease is one example of a dispersed system characterized by high thixotropic properties, which, together with viscosity and shear strength parameters, determine the rheological properties of lubricating greases. Rheology is the science of flow and 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 vertical and inclined friction units without loss. After all, if the bearing is lubricated with liquid oil, you need to constantly monitor its quantity: it can leak out, evaporate and requires frequent application. Grease fills the bearing cavity, seals the assembly and prevents abrasive particles from entering the bearing, which can cause the mechanism to seize. Thixotropic properties provide stable protective film between working surfaces, which softens shock from vibration and reduces the effects of wear from sliding friction.

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