use of high-PerforManCe PlastiCiZers to ProVide design and oPerational requireMents for the ConCrete CoMPosition for the ConstruCtion of floating CoMPosite doCKs

The object of research is plasticizers, which are the most popular additives for improving the quality properties of concrete, is used to build high-strength reinforced concrete products for hydrotechnical purposes. One of the most problematic places is the strength of concrete. This is due to extreme operating conditions and loads that survive the construction of the floating dock. Methods of analysis and generalization of scientific literature on design and operational requirements for concrete of hydraulic structures were used during the research. Data have been obtained that make it possible to compact the concrete mixture, reduce the consumption of cement, increase the frost resistance and waterproofness of concrete. This is due to the fact that the superplasticizers are introduced into the concrete mixture in an amount of 0.15...1.2 % of the cement mass, dilute the concrete mixture to a greater extent than conventional plasticizers. Superplasticizers have a number of features, in particular, the plasticizing effect persists for 1.0...1.5 hours after the addition, and after 2...3 hours it almost disappears. Thanks to the use of plasticizers it is possible to increase the mobility of the concrete mix without reducing the strength of the concrete. The combination of plasticizers with other types of additives (hardening accelerator, microsilica, air entraining admixtures) for concretes and mortars allows plants to produce high strength mixtures with unique properties.


introduction
The working conditions of marine reinforced concrete structures (especially floating docks) are largely extreme.Reinforced concrete structures of floating docks are ex posed to all known environmental influences due to the fact that they are operated in all climatic zones of the globe.At the same time, the structures of the floating dock experience the following loads: -permanent (cargo on the deck, water pressure, etc.); -static variables (forces of water ejection during de flection and bending of the shell); -dynamic variables (impacts, invasions), as a result of which stresses of different magnitude and variable direction arise in the concrete.The advantage of reinforced concrete is that concrete itself works well for compression, and tensile work is pro vided by reinforcing steel, which is protected from aggressive Технологічний аудиТ Та резерви виробницТва -№ 1/1(39), 2018 ISSN 2226-3780 seawater by concrete.In this case, much less steel is con sumed than the steel hull, as the thickness of the structures is ruled out for corrosion.Rebar is cheaper than profile and sheet.Since reinforced concrete does not corrode in water, the pontoon body does not require painting and docking.Metal towers can be painted and repaired with out docking and the conclusion of the operation dock, in parallel with the repair of the ship in it [1].
Concrete blocks of ferroconcrete floating docks in all climatic zones alternately moisturized and dried, exposed to salts of sea water -chemical corrosion as a result of the reaction between cement stone and salts dissolved in sea water.In addition, in the southern, subtropical and tropical seas, the effect of chemical corrosion is enhanced by high temperature, humidity with repeated and alternat ing moistening and drying.In the northern and eastern seas, shipbuilding concrete in winter is repeatedly frozen and thawed alternately.
According to climatic conditions and degree of ag gressiveness of the sea water, where floating docks are operated, can be divided into seas: -with particularly strict (the Barents Sea, the White Sea, the seas of the Pacific basin); -with severe (the Black Sea, the Caspian Sea); -with moderate climatic conditions (the Baltic Sea).
In connection with such multifactor operating condi tions of reinforced concrete vessels, as well as the develop ment of directions for the use of reinforced concrete floating facilities, development of new types of plasticizers in order to improve the quality properties of concrete is relevant.

the object of research and its technological audit
The object of this research is plasticizers, which are the most popular additives to improve the quality properties of concrete, is used to build highstrength reinforced concrete products for hydraulic engineering purposes.
The production of highstrength reinforced concrete products of hydraulic engineering purpose is connected, first of all, with the maximum use of cement binding capacity, which determines the modification degree of the cement system, which provides for the absence of excess mixing water, as well as for the entrained air [2].
The thickness of the hull of the reinforced concrete vessel is sufficiently small (in places up to 4...8 cm).In order to ensure the overall and local strength of the hull, the percentage of saturation with steel reinforcement is quite large (250...600 kg/m 3 ).Fat compounds of concrete are used (cement consumption of 450...800 kg/m 3 ), mo bility of 2...18 cm with a small filler and small values of watercement ratio of 0.32...0.45.Taking into account the above data, it can be concluded that shipbuilding concretes differ from concretes used in other industries and have their own specific features.
Shipbuilding concrete should also have sufficient cor rosion resistance and density.It must reliably protect the reinforcement from corrosion with a protective layer thick ness of 0.5 cm for internal dry and surfaces, periodically moisturized, and 1.0...1.15cm for the outer surfaces of the reinforced concrete vessels.
One of the most problematic places is the strength of concrete.This is due to extreme operating conditions and loads that survive the construction of the floating dock.

the aim and objectives of research
The aim of research is the selection of highly effective plasticizers in order to provide design and operational requirements for the concrete composition for the con struction of floating composite docks.This will increase the strength of pontoons of floating composite docks.
To achieve this aim it is necessary to: 1.Consider the special requirements for shipbuilding concrete and concrete mix in connection with the extreme working conditions of marine reinforced concrete structures.
2. Classify plasticizing additives on the effectiveness of plasticizing action.
3. Consider the permissible content of harmful impuri ties in aggregates for heavy concrete.

research of existing solutions of the problem
The complex of design requirements for hydraulic con crete is provided by the choice of source materials and additives, the design of warehouses of concrete mixtures in accordance with the operating conditions, taking into account the recommended restrictions (Table 1).The ex perience of the construction of hydrotechnical structures and the research of scientists [4,5] indicate that in dense concrete, the permeability of concrete is determined, mainly, by watercement ratio (W/C).At high W/C values the structure of concrete is characterized by large capillary pores and sedimentation voids below the surface of a mas sive filler, which is the reason for the high permeability of such concrete.Modified concrete of semidry forma tion is characterized by low W/C values, lack of large capillaries and sedimentation voids, which ensures their high impenetrability.As for other types of heavy concrete for hydraulic concrete, the strength at the design age is normalized in accordance with GOST BV.2.74396 for classes of com pressive strength, axial tension and bending tensile.
For the concrete of structures subjected to alternating freezing and thawing during operation, the following frost resistance grades (F) are assigned: 50, 75, 100, 150, 200, 300, 400, 500, 600, 800, 1000 With permeability restriction, increased density and corrosion resistance designate brands for water tightness (W): 2; 4, 6; 8; 10, 12; 14; 16; 18; 20.Technology audiT and producTion reserves -№ 1/1(39), 2018 ISSN 2226-3780 In the freshly prepared concrete mixture, chemical and physical processes occur simultaneously, related to the hydration of cement grains, water separation, compaction and delamination of the mixture [6].The increase in the strength of concrete with the additive as a whole is de creased with the increase in the duration of heat treatment, especially the isothermal warmup stage.However, based on the increase in strength of concrete with additive, it seems possible to reduce the time of heat treatment of concrete consumption of cement [7].The consistency of the concrete mix must ensure the reliability of transporta tion and the possibility of its enclosure in the formwork of the underwater structure.Therefore, the consistency should be assigned taking into account the conditions of concreting and the shape of the construction [8][9][10][11][12].To solve the problem of increasing the operational charac teristics of efficient hydraulic finegrained concrete, it is necessary to optimize the compositions of such concretes and the technologies for their preparation, as well as the use of various organic and mineral modifying additives.
One of the main types that reduce the strength of concrete defects is increased porosity.The porosity arises from the concrete destruction during operation and is expressed in the loosening of its structure, weakening the bond between the crystalline new formations in the cement stone, as well as the cement stone and the ag gregate particles.This leads to a decrease in the strength of concrete, and also facilitates the filtration of water and aggressive liquids into the volume of concrete, frost and abrasive destruction [13].The solution to this problem can be a significant compaction of the concrete structure.According to the research results in the scientific and technical literature [14][15][16][17][18][19], it is known that metakaolin is introduced as a fine mineral admixture into a concrete mixture in order to reduce cement consumption and also compact the structure of concrete.Moreover, its quantity should not exceed 15 % of the mass of cement, since it contains active silica and alumina in approximately equal proportions.And for this reason, stronger than microsilica, binds free calcium hydroxide, which leads to a decrease in the alkalinity of the medium in concrete and can cause corrosion of steel reinforcement.In connection with the need to ensure the strength of concrete is a promising improvement in the composition of concretes [20][21][22][23][24][25].
Plasticizers are the most popular additives to improve the quality properties of concrete [26].At present, plasticizer is an indispensable element of any concrete solution in construction, which is explained by a number of advantages: increasing the plasticity of the finished solution, saving the cost of cement mortar, improving the crack resistance of concrete [27].Plasticizers are divided into 4 classifica tions: strong, weak, medium and superplasticizers [28].Plasticizers began to be used in the 1940s, and due to the rapid pace of development of construction technolo gies they reached a qualitatively high level and are able to increase the composition of the concrete mixture [29].According to the principle of action, plasticizers are di vided into 2 types: hydrophilic and hydrophobic [30].The main function of additives of the first kind is in creasing the plastic and flowing properties of concrete [31].Plasticizers of the second kind saturate the concrete mix ture with oxygen, which in turn reduces the tension of water in the solution [32].The hydrophobic solution is applied to the surface of the building structure.The depth of penetration is greater, the lower its surface tension and viscosity and the higher the porosity of the building ma terial.The walls of the pores and all the particles of the material that come in contact with the solution are covered with a water repellent film of the hydrophobic agent.In this case, neither the pore size nor the texture of the solid surface changes.When hydrophobizing the solution, all times are kept open, the ability to wet with water loses their walls, while the material loses the ability to capillary absorb water [33][34][35][36][37].The paper [38] also deals with the use of various activated and plasticizing additives in a con crete mix.The main drawback of plasticizers is the increa se in the time of hardening of the concrete mixture [39], which affects the timing, and later the cost of construction.In modern construction, the implementation of complex projects requires the development of efficient and high quality concretes that can't be solved without the use of plasticizing additives in concrete technology [40].
Plasticizing additives are characterized by high efficiency and no negative impact on concrete and reinforcement.Of greatest interest are plasticizing additives from the family of super and hyperplasticizers [41].It is known [42,43] that plasticizer additives, which allow to reduce the wa ter requirement of the concrete mixture at the working concentrations corresponding to the maximum functional action (plasticization and water reduction).Additivesplasti cizers give a sufficiently long blocking effect on the kinetics of hardening of most cements and the strength of concrete.

Methods of research
Methods of analysis and generalization of scientific lite rature on design and operational requirements for concrete of hydraulic structures were used during the research.
The choice of the type and brand (or class) of cement, its mineralogical and material composition is due to the necessary strength properties of concrete and the kinetics of the increase in strength in time.For hydrotechnical concrete of massive structures, the use of moderately and lowthermal cements with normalized chemicalmineralogi cal composition and an increased content of active mineral additives is common.For concrete, which operates under conditions of alternating freezing and thawing under the action of a mineralized aqueous medium, sulfateresistant lowaluminate cements are used.
In addition to the design requirements for strength, frost resistance and waterproofness for hydraulic concrete in accordance with working conditions and design standards, a number of additional requirements may be presented.The design age in which technical requirements are to be provided is indicated in the design documentation.It is assigned in accordance with the design standards, depending on the conditions, requirements for concrete, methods of erection and the timing of the actual loading of structures.If the project age is not specified, the technical requirements for concrete should be provided in 28 days.
If fast reinforcement of sufficient strength of concrete is required, especially in the manufacture of prefabricated reinforced concrete elements, quicksetting cements are also used.To the fillers for hydraulic concrete as well as for cements, the requirements are determined differen tially, depending on the operating conditions of structures.The most stringent requirements are imposed on concrete, working under conditions of variable water level.Технологічний аудиТ Та резерви виробницТва -№ 1/1(39), 2018 ISSN 2226-3780

research results
General requirements for fillers for hydraulic concrete are similar to the requirements for fillers for other types of heavy concrete (DSTU B V.2.74396).Large aggre gate -crushed stone or gravel is chosen, taking into ac count its grain composition, the largest size, the content of clay and dust particles, other harmful impurities, grain size, strength and content of grains of weak rocks, petro graphic composition and radiationhygienic characteristics.When selecting the composition of concrete, also take into account the density, porosity, water absorption and emptiness of the aggregate grains.
For concrete in the zone of variable water level, rubble or gravel with an average grain density of at least 2.5 g/cm 3  and water absorption of no more than 0.5 % for aggre gates of igneous and metamorphic rocks and 1 % for sedimentary rocks are used.For concrete inside, under water and abovewater zones, the density of grains of coarse aggregate should not be lower than 2.3 g/cm 3 , and water absorption is not more than 0.8 % for aggre gate from igneous and metamorphic rocks, and 2 % for sedimentary rocks.
The quality of aggregates is significantly affected by the content of pulverized, clayey and silty impurities, which is usually determined by the soaking method.Dust particles include particles ranging in size from 0.005 to 0.05 mm, in clay and silty up to 0.005 mm.Restriction of the content of silty admixtures in the aggregates is caused by the negative influence of the films formed by them on the bonding of cement stone with aggregate, and as a result, on strength, frost resistance and other properties of concrete, water demand of concrete mixes.For concrete of hydraulic structures, the content of clay and dust particles in a large aggregate (regardless of the type of rock) should not exceed 1 % for concrete of the zone of variable water level and 2 % for the underwater and inner zones.In this case, the presence of clay in the form of individual lumps is not allowed for concrete used in a variablelevel zone.
Frost resistance of large aggregates for all types of heavy concrete can't be lower than the normalized con crete grade for frost resistance.For hydraulic concrete, which is demanded for frost resistance and cavitation resistance, crushed stone is used from igneous rocks of the brand for strength not lowers than 1000.The frost resistance of crushed stone and gravel is normalized tak ing into account the average monthly temperature of the coldest month of the year.If the latter ranges from 0 to minus 10 °C, the mark for frost resistance of crushed stone and gravel should not be lower than F100, below minus 10 °C -F200.
In the manufacture of wearresistant hydrotechnical concrete for crushed stone and gravel, a mark on wear in the shelf drum is defined, which should be not lower than СтІ for aggregates from igneous and metamorphic rocks and СтІI -sedimentary rocks.
For hydrotechnical concrete, rubble of natural stone with a grade of not less than 600 is used for classes of strength to C15 inclusive, not lower than 800 for classes from C20 to C30 and 1200 for classes above C30.In crushed stone and gravel for concrete in the zone of vari able level, the content of grains of weak rocks is not allowed more than 5 %.
For concrete hydraulic structures it is allowed to use sand with a size modulus from 1.5 to 3.5.The total resi due on the sieve with the hole size: -2.5 mm from 0 to 30 %; -1.25 mm -from 0 to 55 %; -0.63 mm -from 20 to 75 %; -0.315 mm -from 40 to 90 %; -0.16 mm -from 85 to 100 %.In this case, fine sand with a size module equal to or smaller than 2.0 is used with the obligatory application of plasticizing surfaceactive additives.
The content of clay and dust particles, as well as mica particles, which are often encountered when sand is used for concrete of hydraulic structures, is established taking into account its location with respect to water.For the concrete of the zone of variable water level, the content of clay and dust particles in the sand, as well as mica, must be respectively not more than 2 and 1 %, the sur face zone -3 and 2 %, the submarine and internal -5 and 3 %.The admissible content of harmful impurities in aggregates is given in Table 2 [3].With additives regulating the properties of concrete mixtures, plasticizing additives have been used most in the technology of hydraulic concrete.
In accordance with the effective plasticizing effect, that is, an increase in the mobility of the concrete mixture without reducing the strength of concrete, the plasticizers are divided into 4 categories (Table 3) [3].ISSN 2226-3780 Airentraining additives, depending on the chemical nature, are divided into six groups: 1) salts derived from wood tar; 2) synthetic detergents; 3) salts of lignosulfonic acids; 4) salts of petroleum acids; 5) salts derived from proteins; 6) salts of organic sulfonic acids.
The considerable experience of application in the hyd raulic technical concrete of the additives of the first group, obtained during neutralization by caustic soda of wood tar after extraction of turpentine from it, is accumulated.This additive, which is predominantly sodium acetate, known as neutralized vinsol or neutralized airentraining resin.
The main purpose of airentraining additives is a radical increase in frost resistance of concrete as a result of the creation of a rational system of air bubbles to squeeze out part of the water during freezing.
Along with plasticizing and airentraining or gasreleasing additives in modern technology of hydraulic concrete, other additivesmodifiers are increasingly being used.The desire to universalize the effect of additives and enhance their technical effect is due to the use of complex (composite) additivesmodifiers.
To ensure the fracture toughness of concrete, it is neces sary to fulfill the condition [3]: where σ t -the tensile stress; E e -modulus of concrete elasticity; K s -safety factor (K s ≈ 1,2...2); e u -the ultimate extensibility of concrete.The ultimate extensibility of concrete improves with increasing strength of concrete when using cement without mineral additives, introducing surfactants and polymer additives into the concrete mixture.
To ensure the necessary crack resistance of massive concrete, its shrinkage deformations are also limited.For hydraulic concrete with a relative humidity of 60 % and a temperature of 18 °C at the age of 28 days, linear shrinkage is usually not more than 0.3 mm/m (0.3•10 -3 ), and at 180 days -0.7 mm/m (0.7•10 -3 ).
Depending on the operating conditions for concrete, hydraulic structures are assigned appropriate brands for frost resistance and water tightness.According to DSTU BV.2.74396, the volume of entrained air in the case of frost resistance of concrete F 200 and above must meet the requirements given in Table 4 [3].
The waterproof concrete grade is assigned depending on the magnitude of the pressure gradient, that is, the ratio of the maximum head of water to the thickness of the corresponding zone of the structure.With a pres sure gradient of up to 5 and the temperature of the water in contact with the construction of up to 10 °C, a concrete grade of water resistance W2 is assigned; 5...10 °C -W4; 10...15 °C -W<6; 15...20 °C -W8 and 20...30 °C -W10.At a water temperature of more than 10 to 30 °C, concrete grades for water tightness are intended to be increased by one step with corresponding values of pressure gradients.One more step (from W6 to W12) marks concrete waterproofness at a water tem perature above 3 °C.In nonpressure structures of marine structures, the design brand of waterproof concrete must be at least W4.For designs with a pressure gradient of more than 30, concrete grades are assigned for water resistance W16 and above.The composition is determined by sifting samples of sand and crushed stone through a standard set of sieves.As a result, the limiting curves of the granulometric composition [44] are determined, which are enclosed in the shaded area: for sand -Fig. 1, for crushed stone -Fig.2.
For parts and elements of the dam, which are perio dically washed by water, the concrete grade for water tightness is adopted not less than W4.When exposed to concrete flow of water with mobile sediments, as well as in the case of cavitation action of water, the concrete grade for water tightness should not be lower than W8.
Additives improve the quality of concrete and add to it special properties, which allows to accelerate the pace of production, as well as significantly cheaper it.Special properties of concrete are necessary both for the construction of pontoons, piers, basins and special struc tures, and for monolithic industrial construction.To improve the convenience of laying concrete, plas ticizers and superplasticizers are used.For the construc tion of pools and reservoirs of various kinds, additives are used that increase the water resistance of concrete several times.Superplasticizers in most cases are synthetic polymers: melamine resin or naphthalenesulfonic acid derivatives (C3), other additives (СПД, ОП7, etc.) are obtained on the basis of secondary products of chemical synthesis.Super plasticizers, introduced into the concrete mixture in an amount of 0.15...1.2% of the weight of cement, dilute the concrete mixture to a greater extent than conventional plasticizers.The plasticizing effect persists for 1.0...1.5hours after the addition, and after 2...3 hours it almost disap pears.In an alkaline environment, these additives pass into other substances, are not harmful to concrete and do not reduce its strength.
Superplasticizers allow to use spray method of manu facturing reinforced concrete products and concreting of structures using concrete pumps and pipe transportation of concrete mixture.On the other hand, these additives make it possible to significantly reduce the W/C, while maintaining the mobility of the mixture, and to produce highstrength concretes.
State standards «Additives for concrete.Classification» define the class of additives -plasticizers.In practice this class is divided into four categories.The most significant feature in the distribution of plasticizers into individual categories is the magnitude of the plasticizing effect, that is, the change in the mobility of the concrete mixture when an additive is added to it.
A number of plasticizers significantly increases the mo bility of the concrete mix, but slows down at an early age, the increase in strength of concrete causes increased air entrainment.To maintain the strength of concrete of this composition with an additive at a level not lower than the strength of the initial concrete without the ad ditive, it is necessary to reduce the watercement ratio in the concrete mixture and, therefore, to a certain ex tent reduce its mobility.The real technical effect of using such additives can be small.To evaluate it, it is proposed to introduce the concept of an effective plasticizing ac tion, which also means the amount of plasticizing effect achieved from the use of the additive without reducing the strength of concrete.
So, for example, to the first category of plasticizerssuperplasticizers -it is possible to attribute additives, the use of which in optimal dosages allows one to obtain from highly inactive concrete mixtures with a cone slump of 2...3 cm highmobility concrete mixes.In these mixtures, the cone sediments are 20 cm or more without reducing the strength of concrete at the age of 28 days of normal hardening compared to the strength of concrete of the same composition, but without additives.
Classification of additives by effective plasticizing ef fect is given in Table 5 [3].It should be borne in mind that for concretes manufac tured using a specific technology, including those subjected to thermal treatment processing, the effective plasticiz ing action of the additive may be slightly different.The choice of plasticizer of a certain category is carried out by calculating the technical and economic efficiency of its application in a specific technological process.Superplasticizer C3.Organic synthetic substance based on the condensation product of naphthalenesulfonic acid and formaldehyde with a specific ratio of fractions with different average molecular weight.According to the clas sification C3 refers to the plasticizingwaterreducing typesuperplasticizers.Superplasticizer C3 is intended for: -a sharp increase in the convenience of laying and the formation of concrete mixtures without reducing the strength and of concrete durability indices (with a constant watercement ratio); -a significant increase in physical and mechanical properties and construction and technical properties of concrete (with a reduction in water consumption and unchanged ease of installation); -improvement of the convenience of laying concrete mixes and increase of physical and mechanical properties and construction and technical properties of concretes; -reduction of the cement consumption without re ducing the convenience of laying a concrete mixture, physical and mechanical properties and the construc tion and technical properties of concrete.Superplasticizer C3 is also the basis for the production of complex additives of various types.Superplasticizer C3 is recommended for use: Technology audiT and producTion reserves -№ 1/1(39), 2018 ISSN 2226-3780 -for the production of all types of structures from monolithic heavy concrete classes (by compressive strength) B15 and above; -in the manufacture of all types of prefabricated rein forced concrete structures and concrete products from heavy concrete classes (by compressive strength) B15 and above; -for the production of all types of structures from monolithic finegrained concrete classes (by compres sive strength) B10 and higher; -in the manufacture of all types of prefabricated re inforced concrete structures and concrete products on porous aggregates of classes (by compressive strength) of B7.5 and higher.Plasticized concrete mixes with high convenience of laying are recommended to be used in thickreinforced structures, thinwalled structures, complex configuration constructions, etc.
Concrete mixtures with a lower watercement ratio (wa ter reduction) are recommended for the production of monolithic and prefabricated reinforced concrete structures, to which high demands are placed on strength, waterproof ness, frost resistance, corrosion resistance, Superplasticizer C3 is produced in the form of a powder (microgranules) or in the form of an aqueous solution.

swot analysis of research results
Strengths.All superplasticizers significantly increase frost resistance and waterproofness of concrete.In addi tion to superplasticizers, there are plasticizers of different categories, they do not exclude vibratory compaction of solutions, but allow to some extent to compact the con crete mixture, reduce cement consumption, increase frost resistance and water resistance.They all have one very important feature -they greatly facilitate the mixing of the concrete mix.
Weaknesses.Plasticizers slow down the setting and hardening of the concrete mix.
Opportunities.Use of plasticizers will give the fol lowing opportunities: -plants producing reinforced concrete products benefit from the use of plasticizers by reducing the time of steaming or reducing the temperature in the chambers.
There will be a significant saving in energy resources, accelerating the turnover of form equipment and as a consequence -an increase in production volumes; -for obtaining equal strength concrete with the same mobility using plasticizer C3 and without it, one cubic meter of concrete mix consumes 15 % less cement.Using this additive can reduce the amount of mixing water; -mobility of the concrete mix increases without the effect of reducing the strength of reinforced concrete products and structures; -strength characteristics are increased by up to 25 %; -preparation of highdensity concretes (high imperme ability), which positively affects the waterproofness of reinforced concrete products and reinforced concrete structures; -frost resistance increases to F350, crack resistance also increases; -production of highstrength reinforced concrete products of high strength (compressive strength over 100 MPa).For example, a concrete sample of brand m 350 (B25) at the age of 28 days has a compressive strength of 25 MPa; -coupling of reinforcement with concrete is increased by 1.5 times.
Threats.When choosing plasticizing additives, it is necessary to pay great attention to the choice of plasti cizer manufacturers, since the quality of plasticizers can differ significantly.
When using modifiers, the concrete structure hardens more slowly.In order to compensate for the slowing effect of the use of plasticizers, a hardening accelerator can be introduced into the concrete solution, which compensates for this disadvantage.As a result, the construction har dening schedule will be aligned.
There are other types of additives for concrete and mortars, which include the following.
Hardening accelerators, which are introduced to compen sate the action of the plasticizer, inhibiting the hardening process.Also, accelerators are used for concreting in cold weather.Since, the lower the ambient temperature, the slower the process of hydration of cement, the strength set occurs at a slowed pace.
Hardening retardants, which are used to increase the lifetime of the concrete mixture.In the group of retarders can be attributed douche, which also provide a slowing effect.
Airentraining additives are used mainly to increase the frost resistance of concretes and solutions.These ad ditives reduce the strength of concrete (1 % of the en trained air reduces the compressive strength of concrete by 3 %), therefore, it is not necessary to introduce a large amount of airentraining additive into the concrete mix for its plasticization.The content of the entrained air is 4...5 %.In this case, the strength of the concrete is practically not reduced, since the negative influence of the entrained air is neutralized by an increase in the strength of the cement stone due to a reduction in the water cement ratio due to the plasticizing effect of the additive.The airentraining additive hydrophobizes the pores and capillaries of concrete, and air bubbles serve as a reserve volume for freezing water without the occurrence of large internal stresses.As a result, water resistance and frost resistance of concrete significantly increase.
Antifreeze additives for concrete provide the possibi lity of winter concreting at negative temperatures and the absence of additional heating of the filled structure.Some types of additives allow concreting at a tempera ture of -25 °C.
In modern production complex twocomponent addi tives are used.For example, the plasticizer C3 and the hardening accelerator, microsilica, and airentraining ad ditives are immediately mixed.The use of such additives allows plants to produce mixtures of high strength with unique properties.Karakurkchi a., sakhnenko n., Ved M., Parsadanov i.

introduction
The internal combustion engine (ICE) piston is one of the most important details of a modern car that ope rates under severe conditions with significant thermal and mechanical loads.Therefore, the following requirements are put forward to piston alloys' properties: lightness, strength, low friction coefficient, high thermal conductivity, wear and corrosion resistance, economic accessibility and simp licity of technological treatment [1].
Alloys of aluminum with silicon (silumines) fully meet these requirements.The high content of silicon gives

table 4
The volume of entrained air is recommended for hydraulic concrete with increased frost resistance (F > 200)*