1 possesses the best thixotropic properties. Thixotropy (rocks)

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

Mechanical loads (vibration, shock, etc.), physical (wear, shrinkage, freezing and thawing, temperature fluctuations, salt crystallization) can act on an artificial stone.

Structures are strongly weakened by chemical loads. Due to the capillary-porous structure, alkalis and sulphates, salt solutions are able to penetrate into the thickness of concrete and ultimately affect its bearing capacity. If the structure did not withstand the loads and requires repair, the choice of the working staff 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 filler, modifying additives. Unlike other cement analogs, the mixture contains reinforcing fiber. When mixed with water, the material forms a high-strength mortar that does not shrink. It is effective in the repair and restoration of 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 mixtures 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 the operation;
• repair of the protective layer, filling of rigid joints, elimination of surface defects (new filling joints, gravel nests, open reinforcement, traces of formwork removal);
• alignment of walls, enclosing structures;
• repair of foundations under strong abrasive loads, reinforced concrete structures of hydraulic structures;
• waterproofing works on the roof, in basements, concrete tanks and trays;
• pouring foundations and monolithic housing construction, monolithing of prefabricated concrete structures;
• repair of floor coverings industrial structures under heavy mechanical stress and under the influence of aggressive media;
• repair of boiler rooms, CHP, chimneys, bridges, viaducts.

In the private sector, thixotropic mixtures are used to repair concrete screeds, floors, paths, wells, stairs, steps, cellars, vegetable pits. The material is successfully used for sealing grooves, 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

The Thixotropic Repair Mix is ​​a specially formulated, ready-to-mix powder. When mixed with water, it turns into a highly thixotropic working solution. 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 specified properties:

• waterproofness;
• high compressive and flexural strength;
• good adhesion to old concrete, reinforcement;
• 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 for their use. They do not work on smooth surfaces (roughness should be ensured), reinforcement is introduced if necessary. The material cannot be used for anchoring and when pouring into formwork.

The application of thixotropic mixtures is realized only at t over 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 used in humid conditions or when sprayed with water. This ensures that all the properties of the product are revealed correctly. This is not easy to achieve on a construction site.

Typical technical data

Tools, equipment and accessories for thixotropic concrete repair

To carry out the repair work, you will need professional electrical equipment and hand tools.

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

• equipment for surface preparation: grinders, grinders, construction vacuum cleaners, compressors, high pressure washers, sandblasting machines, perforators, jackhammers;
• tool: trowels, shovels, spatulas, chisels, drills with mixing attachments, 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.

Preparation of the base

Thixotropic mixtures are most often used for structural repair 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 a load (bearing capacity);
• lack of exfoliating, destroyed layers;
• absence of contamination that negatively affects adhesion (fats, oils, dirt, dust, rust, paint);
• rough texture.

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

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

Methods for cleaning bases:

• mechanical- jackhammers, perforators, picks, pneumatic chippers are used to open cracks and defects. Cleaning is carried out with sandblasting machines, shot blasting machines, grinders and high pressure washers. This is a universal preparation method that should be used in all cases, regardless of how much or how damaged the concrete is. However, the technique is not applied where dustiness is unacceptable;
• thermal- realized with the help of special burners. For concrete, heating is permissible no higher than 90 degrees. The thermal method is effective for insignificant damage depth - up to 5 mm. The high temperature removes traces of oils, rubber, organic compounds. Such processing is always followed by mechanical or hydraulic;
• hydraulic- use hydraulic units and high-pressure apparatus. It is a universal solution for efficient and fast concrete cleaning;
• chemical- for the preparation of concrete, special chemical compositions are used. The method can help out where mechanical cleaning is impossible. After etching, the bases are always rinsed with water.

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

Before applying the thixotropic solution, the base is saturated with water... The surface should be damp but free of 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 the wet primer layer.

Applying an adhesive primer

The material is also applied to a moistened substrate. If the concrete absorbs moisture well, moistening is realized repeatedly. A properly prepared surface should be damp, but not shiny.

Application principle:

• the soil is spread by wet torqueting or medium-hard brushes;
• during operation, control the filling of pores and irregularities of the base;
• a thixotropic repair compound is applied to a wet primer. But, if the surface has time to dry, another fresh layer of soil is applied.

If reinforcement 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 by hand or with metal brushes. A mechanized method can be used by means of sandblasting machines.

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

If there is damaged concrete in the work area, it is removed along with the reinforcing bar.... The use of rotary hammers and jackhammers is unacceptable, as this may lead to a decrease in the adhesion of concrete and reinforcement. The exposed 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 permissible.

Application of protection:

• an anti-corrosion compound is applied to the cleaned reinforcement in two approaches. When working, use a brush of medium hardness or the method of torquetting (wet). The first layer should be 1 mm thick. When the first layer begins to set, a second of identical thickness is immediately realized;
• edges, reinforcement-concrete transition zones, wire fastenings are especially thoroughly processed;
• if the first layer has completely set before the second is applied, arrange another fresh layer.

Elimination 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.

This requires additional surface preparation:

• areas of active leaks are sewn up. During operation, the expansion of the gap inside the structure is provided 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 washers.

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

If the leak is of high intensity, a polyethylene drainage tube is inserted into the repaired area, which will make it possible to localize the drainage of water. 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.

Thixotropic mortar application

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, the range of operations discussed above is carried out. In any case, the concrete must be damp but not shiny before applying the base mortar.

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

Correct 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 l of water is 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;
• in order to reduce the risk of shrinkage deformations, it is recommended to use a moisture-retaining additive when 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, stirring is carried out 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 are required.

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

Manufacturing jobs

The mortar is spread on horizontal and vertical surfaces by hand using a spatula, trowel or trowel, or using a wet trowelling 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 solution is applied in two approaches. The second and all subsequent layers are realized when the previous one grasps, but does not harden to the end.

When applying a layer over 50 mm thick, reinforcement is required.

The grid is set up like this:

• the gap between the reinforcement and the base must be 10 mm;
• the thickness of the protective layer above the mesh must not be lower than 10 mm.

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

Surface care

When the thixotropic repair work is completed, the 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 on the repaired base;
• the surface is covered with damp burlap or plastic wrap;
• a film-forming composition is applied to the concrete.

Quality control

Control is carried out by external examination

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

If a deeper check is required, the method for assessing the adhesion strength, compressive strength is used, and the grade of water resistance of concrete is also determined.

Safety engineering

Dry thixotropic formulations contain cement. Material may irritate mucous membranes and skin. Avoid eye contact and skin contact. If this happens, the affected areas are thoroughly washed with water, then consult a doctor.

Persons at least 18 years of age are allowed to work... All personnel must undergo a medical examination, training, instruction in safety. If work is supposed to be carried out at a height, 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 used with confidence for repair and leveling of concrete structures. The material is convenient to work with, presented at an affordable cost, it is easy to apply even on vertical surfaces. The only limitation one can face is work is possible at temperatures above +5 degrees... If you need to eliminate the defect in the winter, it is better to turn to polymer compositions.

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

Thixotropy

Thixotropy

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

Mechanic the properties of thixotropic structures are characterized by the values ​​of three parameters (P. A. Rebinder): the greatest eff. viscosity h 0 practically intact structure, the smallest eff. viscosity h m maximum fractured structure and ultimate shear stress P 0 . Dependence eff. viscosity h on the applied shear stress P can be described by ur-niy

For small values P that do not violate rest or cause a very slow flow, the structure has the properties of a solid, since its recovery under these conditions exceeds the rate of destruction. At R>>R 0, the system turns out to be extremely destroyed and has a low viscosity h m... The magnitude P 0 characterizes an unbroken 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 a low rate accelerates the growth of strength and structuring of dispersed systems; this phenomenon is called. reopex and e y. Sometimes concentrated dispersed systems (pastes) exhibit dylatans and I - an increase in h with an increase in the deformation rate, accompanied by a certain increase in the volume occupied by the system: upon deformation, solid particles form a looser framework and the existing liquid medium turns out to be not enough to provide the system.

T. dispersed systems has a great practical. meaning. Thixotropic properties must be possessed by greases, paints and varnishes, ceramic. masses, flushing, used when drilling wells, pl. food products. I. H. Vlodavets.

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

See what "THYXOTROPY" is in other dictionaries:

Thixotropy ... Spelling dictionary-reference

Thixotropy- - the ability of dispersed systems to restore the original structure destroyed by mechanical action. [Terminological dictionary for concrete and reinforced concrete. FSUE "Research Center" 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 stress. Thixotropy is an important technological property of flushing fluids used in ... Big Encyclopedic Dictionary

Noun., 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 hydroxide) under mechanical action (shaking, stirring) to liquefy and turn into sols, which in a calm state again gell. These… … Geological encyclopedia

thixotropy- The phenomenon of a reversible process of transition of jellies and gels into a liquid state under mechanical action Topics oil and gas industry EN thixotropy ... Technical translator's guide

thixotropy- - the ability to spontaneously restore the structuring 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 stress. Thixotropy is an important technological property of flushing fluids used ... encyclopedic Dictionary

thixotropy- Thixotropy Thixotropy Reversible change in the physical and mechanical properties of polymer and dispersed 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 necessary, discuss the feasibility ... ... Wikipedia

(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) - a physicochemical phenomenon that occurs in some colloidal dispersed systems, for example, in cohesive rocks, and consisting in their spontaneous liquefaction under the influence of mechanical action (shaking, stirring, vibration, exposure to ultrasound, etc.) and the subsequent restoration of the structure while eliminating these influences. Thixotropy is explained by the reversible weakening of the structural bonds between the mineral particles of the cohesive rock. Under a certain mechanical action, bound and immobilized water passes into free water, which leads to a decrease in the strength of structural bonds and liquefaction of the rock. Termination of exposure leads to the reverse transition of water from a free to a bound state and hardening of the rock (thixotropic hardening).

Fragility is an indicator characterizing the tendency of rocks to thixotropic softening. It is customary to measure it with the average radius of the base of a cylindrical sample (mm) after 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 fluctuation index varies from 8-9 for non-thixotropic rocks to 15 or more for highly thixotropic rocks. A more general indicator is the structural strength limit under dynamic action, defined as the limiting alternating acceleration at which the rock strength does not decrease. It is measured in m / s 2. 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 clay particle content of at least 1.5-2%.

Thixotropy is widespread in nature and has both a negative and a positive effect on technological processes in the development of wet cohesive rocks. For example, when transporting such rocks, thixotropic liquefaction causes their intensive adhesion to the working surfaces of the transport equipment, reducing its productivity by 1.5 times. On the other hand, thixotropy is used in drilling and pile driving. Thixotropy is the cause of landslides.

Thixotropy is a concept that may not be widely known, but it is found everywhere. Paints and varnishes, printing inks, bearing grease, and many foods all have certain viscosity properties that change over time. There can be two options: either the substance begins to flow, that is, the viscosity decreases, or solidifies - the viscosity increases. The first phenomenon is called thixotropia, the second is rheopexy. Thixotropy is characteristic of polymer and dispersed systems under mechanical action under isothermal conditions. Scientifically speaking, it is the ability of a substance to restore its yield point 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, upon destruction of the supramolecular structure in polymers or coagulation of colloidal particles within a dispersed system.

What determines the thixotropic properties

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

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

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

Bearing grease and its thixotropic properties

Bearing grease is one example of a highly thixotropic disperse system that, together with viscosity and shear strength parameters, determine the rheological properties of greases. Rheology is the science of flow that 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 losses. After all, if a bearing is lubricated with liquid oil, you need to constantly monitor its amount: it can leak out, evaporate and requires frequent application. The grease fills the bearing cavity, seals the assembly and prevents abrasive particles from entering the bearing, which can cause the mechanism to jam. Thixotropic properties provide a stable protective film between the working surfaces, which softens vibration shock and reduces the effects of sliding friction wear.

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

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

Thixotropic liquids

Thixotropy should not be confused with pseudoplasticity. For pseudoplastic fluids, the viscosity decreases with increasing shear stress, while thixotropic fluids have a viscosity decreases over time at constant shear stress.

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

The viscosity of some fluids at constant ambient conditions and shear rates change over 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 a few days. Rheopex materials are quite rare, in contrast to thixotropic materials, which include lubricants, viscous printing inks, and paints.