Do-it-yourself plasticizers and additives for concrete. What are the additives in concrete and the scope of their application Modern additives in concrete

To improve its preparation, various additives are added. They allow you to increase the strength of structures or increase plasticity. So that the solution does not lose its original qualities, special additives are used in concrete.

What are they used for

When mixed between its fillers, binder and water, hydration occurs - a chemical reaction during which water breaks down into molecules, crystals form and concrete hardens. The more fillers contained in the composition, the greater the number of irreversible reactions will occur at different times. To regulate the rate of hydration substances are added to the mixture, with the help of which the structure of concrete can change.

Additives contribute to the flow of various processes:

lowering the pour point;
increased fluidity;
increase in adhesive properties;
reduction in the volume of concrete and its consumption;
prevention of crack formation;
increase in water-repellent properties;
narrowing of pores, etc.

Besides, concrete additives are used to obtain building material with the required characteristics. Almost all components are based on chemical compounds and are produced in dry and liquid forms.

Types of additives for concrete

All additives can be divided into several groups:

plasticizing and modifying;
moderators and ;
gas-forming and air-entraining;
anti-frost;
waterproofing;
sealing;
pigment dyes.

Pigment dyes for concrete

Each type has its own properties, due to which the concrete mixture acquires certain characteristics for construction.

Modifiers

Modifier additives are designed to improve concrete properties such as long service life, strength of structures, resistance to low temperatures. The addition of modifying additives reduces the permeability of concrete, and also increases the mobility of the solution, contributing to a deeper and more uniform filling of pores and crevices.

The choice of modifier is determined by the scope of concrete. For example, one type of modifying substance is suitable for the construction of sites, and another for the construction of a well or a pool.

plasticizers

This type of admixture is the most demanded, since it can be used to achieve the fluidity and the desired mobility of concrete. The action of plasticizers is to reduce the adhesion force of the particles of the mixture and prevent its delamination.

The main advantage of plasticizers is economy. By adding additives, it is possible to reduce the volume of cement consumed. The second advantage is the ability to quickly fill thin-walled formwork with mortar or cast individual segments of concrete (curbs or tiles for garden paths).

In addition, plasticizing impurities in the composition increase the frost resistance of structures.

Additives-plasticizers can vary in the degree of reduction in the use of liquid (water). The classification looks like this:

Weak (up to 5%).
Average (5%).
Strong (5-10%).
Super strong (over 20%).

Among the shortcomings, there is a decrease in the rate of solidification of concrete due to an increase in the plasticity and mobility of the mortar, therefore it is recommended to use both plasticizers and hardening accelerators.

anti-frost

To improve structures, an antifreeze additive is added to the mixture at the preparation stage. Its action is to lower the pour point of the solution. This means that the concrete mixture can harden even at negative air temperatures.

The main advantage of antifreeze additives is the possibility of carrying out construction work using a concrete composition in the cold season without preheating. At the same time, the cement has time to react with water and not harden at zero air temperature.

Mobility regulators

With their help, the solution retains its plasticity in the most adverse conditions. The best time to use such substances is summer, when concrete floors are poured. Mobility regulators are added to the composition to obtain a homogeneous mass when working with a floor screed.

The main feature of mobility regulators is suitability for work even after long-term transportation.

Additives in concrete for curing

These additives are catalysts for the process of curing concrete and act as plasticizing compounds and hardening accelerators at the same time. They are made up of organic compounds.

In their composition, these additives have chemical compounds:

modifying the mobility and plasticity of concrete;
increasing moisture resistance and retaining moisture inside the solution;
stabilizers against delamination of the cement-sand mixture;
anti-hardeners and hardeners;
air-entraining and gas-forming compounds.

They can also perform anti-corrosion and anti-freeze functions.

Air-forming additives are intended for the formation of micropores in the mixture. Since foam is obtained and pores appear inside the structure, it becomes necessary to waterproof the structure. Therefore, air-entraining compositions are best used in conjunction with waterproofing to increase the frost resistance of concrete.

In addition, substances with an antifungal effect are produced. The presence of such additives reduces the risk of mold and fungal infections at joints that are subject to frequent and forced moisture (for example, at the junction of a foundation with a blind area).

Such additives are purchased for the manufacture of foam and gas blocks.

Anti-corrosion

When these additives are added, the solution acquires such properties of the mixture as resistance to aggressive media that cause corrosion of the concrete structure. Additives protect structures from the destructive ability of sparingly soluble compounds, prevent the washing out of microparticles of concrete hardeners, and prevent the dissolution of substances.

In addition, anti-corrosion components of the mixture are added to the composition to increase moisture resistance and increase the density of concrete.

Additives for self-compacting compounds

Such additives are successfully used in the manufacture of structures with thin walls to increase the strength of the structure and include plasticizers that improve the mobility of the concrete mass. With their help, the density of the composition and the water resistance of finished products increase.

Density regulators help reduce binder consumption while maintaining its quality.

Popular manufacturers and prices

Modern companies offer various supplements, with which you can adjust the technical indicators of the cooked. They also make it possible to reduce the amount of binder used without compromising strength characteristics and to increase the shelf life of the mixture.

These include:

"Technonikol";
"Polyplast";
"Fort";
"Alliance";
Biotech.

Additive brand	Purpose	Cost, rub.*
TECHNONICOL Master		750-850 rubles / 1 l; 500-700 rubles/10 l
Polyplast SP-1	Plasticizer, antifreeze	900 rubles / 10 l; 120 rubles/1 kg or 3000 rubles/25 kg
Polyplast SP-3	Superplasticizer, waterproof, for floor screed	From 70 rubles / 0.4 kg
ArmMix SUPERPLAST	Universal	From 70 rubles / 1 kg
Additive D-5	Waterproofing	From 130 rubles / 1 kg
Fort UP-3	Antifreeze, plasticizer	From 40 rubles / 1 kg
Biotech	Modifier, foaming	From 70 rubles / 1 kg
Fort UP-2M	Integrated to eliminate the delamination of the solution	From 70 rubles / 1 kg

Additives are produced in dry form in bags of 25 kg or liquid, in small containers of 1.5 or 10 liters.

All additives in dry form have a shelf life of up to 12 months, in liquid form - up to 6 months from the date of manufacture.

*The average cost per unit of production is indicated.

A durable monolith is obtained after solidification of a mixture of cement, water and various fillers (sand, lime, crushed stone, slag). Such compositions are widely used in the construction of foundations, cast walls, pools, piers, airfields, roads. With the help of special additives for concrete, you can prepare the perfect mortar for any object, increase the pace of construction and reduce the overall cost of it. Additional components give the finished composite the required properties, allow you to work regardless of the season.

Types of additives, overview of characteristics and properties

The need to change the structure of concrete is determined by various factors:

technological - accelerated concreting, increased plasticity for better laying, the need for a reserve of time for transportation;
operational - increased strength, density, water resistance, resistance to extreme temperatures, thermal insulation properties (for cellular concrete);
climatic - frost resistance and rapid hardening of the composition in winter, and if work is carried out in the heat - delayed setting;
economic - reducing the volume of cement in the solution;
aggressive environment - salty sea water, mineralized ground water, fungal microorganisms.

Classification

Based on each factor, you can choose the appropriate compositions. Classifiers usually distinguish several groups of additives in concrete mixtures, each of which has its own purpose:

plasticizers;
gas and foam-forming;
mobility regulators;
anti-frost;
accelerators (retarders) of hardening and setting (more on);
seals;
increasing the water resistance of concrete structures.

Brief description of the main types of additives

1. Plasticizers.

Builders observe a strict proportion, called the water-cement ratio - it is determined by the purpose of the concrete structure. To obtain a solid wall, no more than 7 liters of water are poured into 10 kg of cement, paving slabs - no more than 4 liters (to resist high loads). Plasticizing additives make it possible to make the solution fluid without pouring water into it and thereby not reducing the strength characteristics of the finished product. The adhesion between the particles of the mixture decreases, but it does not delaminate, there are no voids in it.

The composition becomes more mobile, concreting is facilitated. Without the help of a vibrator, a tile mold or thin-walled formwork is filled to make a foundation. By reducing the weight of cement due to the introduction of additives and without violating its share in relation to water, it is possible to save significant funds. They are divided into super- and hyperplasticizers, the former allow to reduce the amount of cement by 10%, and the latter by 20%.

2. Waterproofing.

Concrete is used for the manufacture of monolithic and block foundations. Gradually, through micropores, it absorbs subsoil or atmospheric moisture. The waterproofing of the structure is provided with the help of rolled materials, bituminous coating, and today additives for waterproofing are used for this purpose. They give the artificial stone hydrophobic properties: its particles begin to repel water molecules.

More recently, waterproofing was achieved by introducing liquid glass (silicate glue). Its price is affordable, but the consumption is too high: 1 liter of material is required for 10 liters of concrete. The purpose is not only waterproofing, but also corrosion protection of reinforcing metal parts. Additives are usually produced on the basis of polymers, the properties of which are to increase their volume in solution and plug microcracks when the mass hardens.

The waterproofing of structures is ensured by Penetron penetrating waterproofing and its analogues. Reacting with cement, they form crystals that fill the air pores.

3. Hardening accelerators and setting retarders.

It is necessary to increase the rate of hydration of cement stone in cold weather, especially if work is carried out in winter. At low temperatures, the setting and hardening of the mixture is inhibited, and at frost, these processes stop. In order to work normally in winter, compounds are introduced for quick setting.

How to perform concreting if transportation takes a long time? Special retardants help to slow down maturation. They are used when pouring large and massive objects so that the concrete remains in a fluid state all this time.

4. Frost-resistant additives.

In winter, concrete hardens at a very low rate - as a result, the product turns out to be loose, and its frost resistance decreases. To avoid this, the solution is heated at the construction site, and in the absence of such an opportunity, special components are used. Their purpose is to ensure filling at sub-zero temperatures (below -5°C). In winter, antifreeze compounds are needed to reduce the freezing point of water in the mixture and stimulate setting in the range from -5 to -25°C.

The following chemical compounds are widely used as winter additives:

potash or potassium carbonate - with its help, concrete sets and hardens even at -30 °;
calcium nitrate - stimulates hardening in winter;
sodium nitrate and nitrite, calcium nitrate - in combination with urea, at low temperatures, they not only contribute to hardening, but also protect the reinforcement from corrosion (sodium nitrite is poisonous and flammable);
calcium chloride;
sodium formate and other salts of organic acids are frost-resistant components that do not have a harmful effect on health (they do not have plasticizing properties).

When these compounds are introduced into the solution, salt deposits do not appear on the structures, they become more durable even with the use of cement of low grades. Additives to improve frost resistance are used when concreting monolithic, as well as prestressed structures - dams, dams, bridges.

Antifreeze mixtures are not recommended to be introduced if it is raining or the air humidity exceeds 60%. The presence of more than 50 mg / mol of reactive silica in the aggregate is also a contraindication - because of this, additional pores appear in the concrete. There is a side effect of calcium chloride: it corrodes the reinforcement.

5. Sealing.

Their purpose is to reduce the percentage of pore content by filling microvoids between molecules. Simultaneously with the compaction of the material, its strength and frost resistance increase, and water absorption decreases. The cost, taking into account the low consumption (approximately 0.5 kg per 100 kg of cement), is low, and the economic effect is significant.

6. Air-entraining.

When water freezes in micropores, it expands, and the concrete is torn like paper. Its strength and frost resistance can be increased by a normalized increase in porosity. For this purpose, concreting is carried out with a minimum amount of air-entraining preparations.

Gas-forming additives also produce the effect of pore formation, but the purpose of the technology is different - to reduce the volumetric weight of the solution, to give it heat-insulating qualities. Blowers are introduced into the mixture in the manufacture of foam and aerated concrete.

7. Complex.

They combine the effect of two or more ingredients. The option is optimal for obtaining the predicted result if the characteristics of the concrete mix should be changed in several directions. Separate components may react incorrectly with each other, so experts advise buying a complex prepared at the factory and balanced in composition. Complex additives simultaneously improve its pore structure and other characteristics - water resistance, frost resistance.

The combined action is performed by the following types:

Modifiers - their purpose in obtaining special concrete with improved technical characteristics. With the help of additives, waterproofing (water permeability grade from W12), corrosion resistance, durability, strength not lower than B125 are provided. Concrete only with additives-modifiers is prepared if it should be expanding, straining, compensating for shrinkage, used for vibrocompression.
Fiber additives. These are fibrous materials based on polymers, glass, steel. They reinforce concrete (increase its resistance to loads and deformations), increase heat resistance, reduce shrinkage, and increase plasticity.

The cost of additives

It is worth paying attention not only to foreign brands, but also to the products of reliable domestic companies. In order to really increase frost resistance, intensify or slow down setting, the proportions of the solutions indicated in the instructions should be strictly observed.

Name	Purpose	Packing volume	Price, rubles
Goodhim InterPlast R	Plasticizer for masonry mortars	1 l	120
Frieze	Increases frost resistance, accelerates setting	10 l	300
C-3	Superplasticizer	1 kg	70
SAZI TIPROM M	Modifier	5 l	1700
NTP acid	Slows down setting	1 kg	130
Fiber FV polypropylene	Micro-reinforcement of the screed	0.6 kg	240

In order for the concrete structure to receive increased strength, it is recommended to use special materials that are added directly to the prepared cement-sand mortar. When hardened, the mixture, to which the concrete hardener was added, acquires many more useful characteristics that contribute to its longer service life. In addition to strength, they can also include water resistance, corrosion resistance, etc.

Application

As a rule, additives in concrete, which are needed to increase its strength, are not always used. The use of such materials is permissible in the case of:

the presence of high requirements for concrete or reinforced concrete structures for water resistance or frost resistance;
application in the solution of non-standard aggregates such as fine sand;
the manufacture of concrete products that will be subject to a high load (for example, paving stones made of heavy or fine-grained concrete);
erection of monolithic structures in which mineral expanding additives are used.

Classification and characteristics of additives

Strengthening mixtures, concrete additives are specially prepared chemical products. They are added to the design or product during preparation and solidify along with the main materials.

The main advantage of additives is the complete protection of the entire concrete by volume. And the disadvantage is the inability to strengthen the already created structure (this function is performed by reinforcing impregnations intended for concrete).

The task of plasticizers, which are part of concrete solutions, is to increase their mobility. At the same time, it is possible both to increase the strength of the resulting concrete by 120-140 percent, and to give it the following properties:

frost resistance increased by 1.5 marks;
water resistance is 3-4 marks higher.

Also, the use of plasticizers reduces cement consumption by up to 25 percent, which saves on construction work.

Strength accelerators are characterized by an increase in the rate of concrete hardening, as well as an increase in its grade strength. One of these substances is granular calcium chloride used in the manufacture of foam concrete, paving slabs, wall stones and polystyrene concrete.

With its help, the production process is accelerated due to less downtime of the product in a special form, and the number of products produced, respectively, increases. At the same time, concrete strengthening by several percent is observed. And on the products, the number of chips that worsen their presentation is reduced.

Among the useful qualities that a concrete hardener with an antifreeze effect adds to the material is not only an increase in strength, but also the elimination of the influence of low (up to minus 25 degrees) temperatures on the solidification process.

One of the most popular substances of this type is a neutralized resin used in conjunction with water repellents (for example, Sofexil-gel and Tiprom-S).

Another advantage of the additive is to improve the ease of handling of the mixture.

In addition, the resulting product becomes waterproof (and thus does not require waterproofing). And when transporting the solution, its stratification noticeably decreases.

Concrete mortar modifiers

Modifiers are an additive to concrete to increase strength, which also increases the frost resistance and mobility of the composition. There are modifiers that can improve the anti-corrosion properties of concrete.

Complex additives

Complex additives to increase the strength of concrete provide additional positive effects. For example, some substances increase the workability of concrete, its construction and technical characteristics (water resistance and frost resistance), reduce the amount of water spent on preparation, and reduce cement consumption. At the same time, all components of the additive perfectly interact with each other.

Nuances of use

Knowing how to increase the strength of concrete, which additive is best suited for the goals, it remains to figure out the correct execution of the work. First of all, the substance is diluted in warm water until it dissolves. If the additive is mixed with a sand-cement mortar in a liquid state, it begins to act immediately. Dry material requires some time for complete dissolution and mixing.

The calculated amount of additive depends on the dosage indicated on the specific material by its manufacturer, as well as on the degree of increase in strength that needs to be obtained. The recommended amount for plasticizers does not exceed 1% by weight of cement.

Other ways to harden concrete

Strengthening materials include not only those materials that are added to concrete during its creation to increase strength. When the design is already ready and cannot be replaced, other substances and other methods are used. The most popular in construction and repair work is the strengthening of concrete using liquid and solid hardeners. They are generally best suited for floors and other horizontal surfaces.

Liquid hardeners or impregnations contain water-soluble inorganic compounds. They are able to penetrate ordinary concrete (which was not previously treated with water repellents) to a depth of 3–5 mm. Inside the material, the liquid reacts with it, forming insoluble compounds that act as hardeners.

Such a hardening impregnation for concrete is applied both to old structures and to new ones, the increase in strength of which was not provided for during the manufacturing process. The disadvantage of impregnation is the impossibility of application in an aggressive environment. The advantage is giving concrete the ability to withstand stronger loads.

To strengthen concrete, you can also use a dry hardener, which contains cement. The structure, the strength of which has been increased in this way, can withstand up to 70 MPa. In addition, the strength of concrete for weak stretching and its wear resistance are increased.

The process of applying a dry hardener is not affected by the aggressiveness of the environment. However, it is applied (in a state diluted with water) only on a smooth and dust-free surface. At the same time, the service life of the structure is increased by at least 10–15 years.

Concrete mortar gradually ceases to be just a mixture of stone and cement laitance. The modern chemical industry offers a number of compounds that can improve the working and operational qualities of concrete, which expands its scope. Which of them can only be purchased, and which ones you can make yourself - you will find out today.

What are concrete additives?

The classification of additives for concrete is quite extensive, but all varieties are divided into two main groups. The first includes additives that improve the working qualities of the mixture: setting time, mobility, tendency to delamination, and others. The second group includes admixtures that help optimize the performance characteristics of concrete: frost resistance, water absorption, strength, and corrosion rate. We note in advance that many supplements have a combined effect.

A distinction can be made according to the nature of the action of the additives. Some of them are chemical, some are mechanical. The first type of additives includes plasticizers, hydration regulators and many others, almost all of their varieties, principle of operation and scope are described in the construction catalog of Gosstroy SK-4.4.3 and GOST 24211-91. Mechanical additives are all kinds of microfibers, porous fillers and fine particles, the effect of which on the structure of concrete is most obvious and predictable.

In this review, we will consider options for replacing popular combined additives with those chemical compounds that are commercially available and are not produced by construction brands. They are quite suitable for improving the most important characteristics of self-prepared concrete, but without overpaying for a big-name product brand.

Means for increasing the mobility of the mixture

The mobility of concrete determines its ability to take the form of formwork without the formation of voids. To improve the mobility of the mixture, surfactants of the hydrophilic type are used. These are mainly sodium oleate and stearate, which form the basis of household detergents, as well as sulfite-yeast mash (lignosulfonate) - a waste product of the cellulose industry, widely used in the production of dry building mixtures.

It is possible to add to concrete both mixtures containing the indicated substances (liquid or laundry soap), and liquid / solid concentrates. In the latter case, the issue of the correct dosage of additives is well resolved. For reference, the content of surfactants in household cleaning chemicals ranges from 35 to 70%, while always proceeding from the calculation of the maximum concentration so as not to exceed the dosage. Both described types of plasticizers are added to concrete in an amount of 0.2-0.35% by weight of cement.

Side effects from the use of plasticizers are mostly positive. This is a slight slowdown in the setting of the mixture, a decrease in the water-cement ratio by 10-15%, a slight increase in porosity. The correct use of lignosulfonate allows, while maintaining the volume of water used, to reduce the content of cement in the mixture by 7-10% while maintaining brand strength.

Lamination Stabilizers

The stratification of the concrete mix consists in the deposition of solid particles of cement and filler with the ascent of water to the surface, resulting in a lack of moisture for hydration. Basically, concrete is stratified due to excessive vibration exposure or when dropped from a great height. Almost all plasticizers based on surfactants improve the uniformity of the colloidal system of the concrete mixture, however, sometimes additional stabilization is required, for example, when casting massive monolithic structures.

One way to protect concrete from segregation is to add ground solids with a high specific surface area, which makes the cement dust better bond with water. Examples of such substances include soot, tripoli, kaolin, and metallurgical ash. It is important that the materials used are exactly fine grinding, otherwise they will not be of much use. Such additives are used in an amount of up to 10-15% of the mass of cement.

Otherwise, it is possible to achieve high-quality stabilization of the concrete mixture by introducing small portions of methylcellulose (MC) - up to 0.5% by weight of cement. When using cement from plasticized clinker, the MC content is halved, and this additive can also be introduced in smaller portions when using a binder of high grades.

Air-entraining agents and sealants

Plasticizers based on surfactants involve the smallest air bubbles in the concrete mixture, thereby increasing the porosity of the concrete. This action is secondary and has a weakly expressed character; if necessary, the porosity of concrete can be significantly increased or, conversely, made more dense.

Silver powder is widely used as a gas-forming agent in very small doses, about 0.02-0.05% by weight of cement. If desired, you can use an organosilicate water repellent called GKZH-94. In order to qualitatively prepare an additive for concrete based on it, the concentrated liquid should be diluted and thoroughly mixed with water in a ratio of 1: 3 until a stable emulsion is formed, and then bring the mixture to the desired consistency with this composition. The final content of concentrated GKZH-94 in concrete is about 2-3% of the volume of water used.

If it is necessary to make concrete more dense, trivalent ferric chloride is added to it during mixing at a concentration of about 0.1% by weight of cement. It is one of the most common and commonly available chemicals used in PCB etching. Otherwise, it is possible to increase the density of concrete using the less common iron sulfate or calcium nitrate, but their content in the mixture is highly dependent on the qualities of cement and mineral filler.

Retarders

Almost all additives that increase the porosity and plasticity of concrete slow down the setting, and sealing additives contribute to a more rapid flow of hydration. The more time the mixture has at the initial stage of hardening, the higher the final strength of the structure. In addition, setting retarders are indicated for the preparation of large portions of the concrete mixture, especially in hot weather, as well as for the phased pouring of volumetric structures to eliminate cold joints.

The main means of slowing down the setting of the mixture are various forms of sugar, however, this additive should be used with extreme caution. Normal setting delay occurs at a concentration of about 0.3-0.5 grams per liter of water used for mixing. In higher doses, sugar can disrupt the course of hydration, or even make the hardening process incomplete. For these reasons, instead of pure sugar, molasses with its content is used, which facilitates the calculation of the dosage.

Sometimes the cumulative effect of multiple additives makes the setting of the mixture too slow, requiring faster hydration. To reduce the setting time, a mixture of potash and sodium aluminate or baking soda is used. These substances should be mixed in a ratio of 4-6: 1, the resulting mixture is added to dry cement in an amount of 0.5-1% by weight. Set accelerators must also be used with care as they can adversely affect the strength of the concrete.

Increased frost resistance and hydrophobicity

It is widely believed that frost-resistant concrete must necessarily be dense, because the destruction of the structure occurs mainly due to the expansion of water in the pores. However, the closed pore structure does not cause such vulnerability, quite the contrary: the presence of microscopic cavities helps to relieve internal stresses caused by linear temperature deformations.

It can be argued that most air-entraining plasticizers and stabilizers have a positive effect on the frost resistance of concrete. Otherwise, the required resistance to low temperatures can be achieved by mixing the mixture on water with a 2-2.5% content of calcium liquid glass. Such an additive reliably closes the pores and prevents the formation of microcracks, due to which the water absorption of the concrete structure is significantly reduced.

In order to be able to carry out concrete work at low temperatures, the cement paste is closed on a mixture of water with calcium nitrite-nitrate-chloride (NNHK). Such a compound cannot be prepared independently, it is toxic and can only be used for non-hydrophobized mixtures. However, there are practically no other alternatives for winter concreting. Concrete with the use of this additive retains increased frost resistance also during operation.

Strength Additives

To strengthen the structure of concrete, it is compacted by the methods described above, or mechanical reinforcing impurities are introduced. The classic material for dispersed reinforcement is mineral, steel or polymer fiber. Its amount in the concrete mixture can be up to 30% of the volume of the filler. Fiber is introduced either by dry mixing with cement before mixing, or in small portions into an already prepared mixture with thorough mechanized mixing.

Also, an increase in strength occurs almost always with the addition of plasticizers and stabilizers. Even air-entraining agents have an increase in compressive strength as a secondary effect, the increased porosity being offset by more optimal cement setting conditions.

Conclusion

The industrial development of concrete modifiers is a rather complex and painstaking process. The ratio of added chemical compounds is not determined by universal rules, but by the type, composition and shelf life of the cement used. Separately, the type of mineral filler and dust-like impurities contained in it are also taken into account.

Collecting a "cocktail" of numerous components, it cannot be guaranteed that their combined effect on concrete will not be negative. Even at enterprises producing precast concrete, the amount and composition of concrete additives are determined empirically through a series of intermediate tests. All this suggests that it is better to use modifiers in quantities that are obviously less than those recommended, not to strive to prepare a universal multicomponent additive, but, on the contrary, to improve only reasonably required qualities.

Although it is said that the best is the enemy of the good, the technologists of our Company do not think so. Virtually no modern enterprise engaged in the production of reinforced concrete, cement or concrete mixtures can do without the use of special additives for concrete, which significantly improve the quality and characteristics of the mixture and regulate the processes of cement setting and hardening.

It would seem, why these additives for concrete, if the concrete mixture is made on modern equipment, and during its production all the norms and requirements for the time and thoroughness of mixing were not violated, the composition of the mixture was observed, high-quality fillers were used: cement, sand, crushed stone, water ? A good concrete mixture is good in itself, but if there is an opportunity to make it better: increase its strength, make it more mobile, increase its moisture resistance, frost resistance, crack resistance, protection from salts, oil products, and so on, then why not do it ?

The modern production of concrete, reinforced concrete products and cement is modern for that, which takes into account all the possibilities and nuances that make it possible to make products "faster, higher, stronger." This is where special additives for concrete come to the aid of factories producing reinforced concrete products and various concrete plants, affecting the behavior of cement at various stages of setting and hardening, and affecting the quality characteristics of the manufactured reinforced concrete products, or monolithic reinforced concrete structures, throughout the entire period of operation.

Let's look at the main types of chemical additives that are used in modern concrete and reinforced concrete production. They can be conditionally divided into groups:

additives in concrete that regulate the main properties of the mixture, such as mobility, plasticity, water retention, pore formation, etc.
types of additives that regulate the preservation and are responsible for the rate of hardening of concrete, the rate of setting of cement, mainly affecting the hydration process in the initial stage of setting, hardening and curing of concrete.
additive for giving reinforced concrete or reinforced concrete special properties: polymeric, biocidal, etc.
antifreeze additives for concrete, allowing concreting at sub-zero temperatures.
additive in concrete that increases its strength, frost resistance, corrosion resistance.
steel corrosion inhibitors, because steel reinforcement, which is part of any reinforced concrete or monolithic reinforced concrete, is subject to the destructive effect of aggressive environments in which many reinforced concrete structures have to work.
expanding additives in cement, reducing shrinkage, increasing crack resistance, creating self-stressing reinforced concrete products and monolithic reinforced concrete structures.
coloring additives - pigments for concrete.
additives in concrete for waterproofing, which include various colmatizing additives, water repellents and other agents that reduce the permeability of a concrete structure.
various types of porous additives for lightweight concrete: gas-forming, air-entraining, foaming, etc.

If we have so many groups, how many supplements will there be? Let me tell you - a lot! To list them all is hardly enough time and effort. We highlight only the main ones that can be useful to a wide range of builders. I’m probably not lying if I say that, or rather, its more advanced successor is the most used concrete additive used today in the production of concrete mixtures. In any case, BESTO Company uses s-3 plasticizer almost always. In general, chemical additives that help reduce the water content in the composition of concrete mixtures are the most in demand. There are a lot of advantages from their use, namely: the fluidity of the concrete mix increases without adding excess water, it becomes more plastic, cement is saved, density, water resistance, frost resistance, etc. increase.

This is where special additives for concrete come to the rescue - plasticizers, which began to be used since the forties of the last century. Today, we mainly deal with their new version, the so-called superplasticizers. They appeared in the USSR in the early eighties. The undisputed leader here - plasticizer s-3. One of the main manufacturers of superplasticizer s-3 is the company "Polyplast". Why plasticizers are so good, let's see:

Saving cement. To obtain equal-strength concrete of the same mobility with and without the use of s-3 plasticizer, 15% less cement is consumed per cubic meter of concrete mix. This magnificence is achieved by reducing the amount of mixing water. But in order to maintain the necessary mobility of the mixture, manufacturers must introduce superplasticizers or plasticizers into concrete. Thus, the water-cement ratio is simultaneously reduced without reducing the mobility.
Without prejudice to the strength of future concrete products and reinforced concrete structures, the mobility of the mixture increases. Which is especially important for monolithic construction, where concrete pumps and concrete pump trucks are used with might and main, requiring p4-p5 concrete for normal operation (cone draft from 16 cm).
Increase in final strength characteristics up to 25%.
Thanks to the improved workability, there is no need to vibrate the fresh mix!
The ability to pour heavily reinforced structures without any problems: columns, narrow wall formwork, and so on.
Obtaining compositions of increased density (high impermeability), which has a positive effect on the water resistance of reinforced concrete products and reinforced concrete structures in general.
Increased frost resistance up to F350 and crack resistance.
Shrinkage of hardening concrete or reinforced concrete products is reduced.
The ability to obtain high-strength reinforced concrete products and concrete, with compressive strengths over 100 MPa! For example: a concrete sample of grade m-350 (B25) 28 days old has a compressive strength of only 25 MPa. That is - four times smaller. Using special modifiers, it is possible to obtain a mixture with a grade strength exceeding the grade of cement used for mixing.
Precast concrete plants benefit from the use of plasticizers by reducing the steaming time or lowering the temperature in the chambers. And this is a significant saving of energy resources, acceleration of mold equipment turnover and, as a result, an increase in production volumes.
The adhesion of reinforcement to concrete increases by as much as 1.5 times (if physicists-chemists do not lie, of course)

It seems to me that the listed advantages are quite enough to understand that producing concrete mixes or reinforced concrete products without plasticizers is not the most profitable measure. However, in our barrel of honey there is also a fly in the ointment. It's small, but it's there. And this tar is a slight delay in the setting and hardening of the concrete structure. You can consider this a negative effect, maybe it will seem positive to someone, but the essence is the same. To compensate for the retarding effect of plasticizers, a special additive for concrete is sometimes introduced - a hardening accelerator. It compensates for everything that the plasticizer spoiled, namely, the schedule of normal hardening of the cast structure.

Today, complex types of additives in concrete are increasingly used. As a rule, they are two-component. For example: based on the plasticizer s-3, and in the appendage a hardening accelerator, or an air-entraining additive, or microsilica, etc. Thanks to such combinations, concrete plants obtain high-strength mixtures with unique characteristics.

Other types of additives for concretes and mortars

Concrete hardening accelerators To compensate for the action of the plasticizer, which slightly slows down the hardening process, special additives are sometimes introduced - hardening accelerators. Also, hardening accelerators can be used for non-standard pours, when a quick setting of the lower layer of the concrete mass is required, so that you can continue pouring further without any problems. A classic example is a monolithic pool bowl, when it is necessary to lay a concrete mixture in the combined formwork of the bottom and walls of the pool so that when it is poured into the walls, it does not squeeze out the newly cast bottom with its mass. Usually this process is stretched in time, but it can be significantly reduced if concrete hardening accelerators are used. Another area of application for accelerators is concreting in cold weather. After all, the lower the ambient temperature, the slower the process of cement hydration, the beginning and end of setting and curing occur at a slower pace. Accelerators also help here.

Concrete hardening retarders By the name it is clear what these types of additives do. They are used to increase the pot life of the concrete mixture. Basically, this may be necessary for transportation over long distances, when it is impossible to quickly fill, and so on. That is, with the use of hardening retarders, we take a time out to have time to do something: eat donuts, drink beer, sleep while the concrete rests in a tub or trough. Moreover, this pleasure stretches for several hours. Something like this. Water reducers can be included in the group of retarders. They also have a retarding effect.

Air-entraining additives As you already understood from the name, they "involve" the air. When mixing the mixture, millions of tiny micro-bubbles of air are created. What is it for. The main task is to create a microporous structure in concrete or reinforced concrete products. Remember aerated chocolate? Here is the same thing, only the pores are microscopic. Due to the presence of these same pores, the frost resistance of a concrete structure or reinforced concrete products increases. Why? Yes, because the water that has soaked the concrete structure, when it freezes, has room to expand. In those very times. Cheap and angry.

However, here is not without tar. They protect cement stone from destruction, but aggregates do not. Rubble also gets from frost and water, as well as without magic bubbles. But this is a completely different song. Of the minuses of such additives is a decrease in the strength of the concrete structure. Slightly, but there is. In any case, you cannot make high-strength concrete with such additives. And frost resistance can be increased in other ways, for example: reduce the water-cement ratio, or introduce fly ash into the mixture, with the same amount of cement. This significantly increases the water resistance (W factor in the labeling of mixtures) and density. Water simply does not enter the concrete structure.

Antifreeze additives for concrete The main purpose of antifreeze additives (PMD) is to provide the possibility of winter concreting at sub-zero temperatures and the absence of additional heating of the poured structure. Certain types of additives allow concreting at temperatures up to -25 degrees. This is "tin" of course, but if there is such a need, then there is no need to choose. So how do antifreeze additives work. For those who are familiar with the "subject" and so it is clear, I will try to explain to everyone else in a few phrases.

The main essence of the solidification of a mortar or concrete mixture is the so-called cement hydration. Simply - the process of crystallization of minerals (silicates, aluminates) present in cement, when it interacts with water. The rate of this process depends significantly on the ambient temperature. At low positive temperatures, the cement setting process stretches in time (several times), at negative temperatures, it stops altogether, due to the banal reason for the freezing of that very water. It is with these two nasty things that the antifreeze additive for concrete fights, by virtue of its capabilities.

The main tasks of modern antifreeze additives are to reduce the setting time of cement and speed up the hardening time of concrete (at low temperatures), to lower the freezing point of water. In Russian, to put it - to make the water freeze not at 0 degrees, but at -10 or -20. You probably remember that salt water is a classic example of lowering the freezing point. There is one more task for modern antifreeze additives - do no harm. Just like in Hippocrates: "... in accordance with my strength and my understanding, refraining from causing any harm ..." But they can do harm. Not all, but they can.

There are quite a few myths about the harmfulness and usefulness of certain antifreeze additives for concrete. All terrible sins are attributed to them: corrosion of reinforcement, and a decrease in strength, and a decrease in frost resistance, and the dog knows what else comes into his head. Unfortunately, I am not a chemist or a naturalist, but I will try to summarize what I once read, heard and tried myself.

Myth one: when using antifreeze additives, reinforcement corrosion occurs in monolithic reinforced concrete or home-made concrete products. This myth came to us from ancient times - "when the trees were big." Take the most common in Russia, sodium nitrite, because on the contrary, it is a corrosion inhibitor. Many antifreeze additives have a positive effect on the adhesion of reinforcement to concrete. I'm not talking about modern complex additives.

Myth two: reduced strength. With a normal % introduction of additives into concrete, there is a slight lag in the rate of strength gain, but upon reaching the classical teenage age of 28 days, the leading laboratory without additive concrete sample (hardening at +20 degrees) disappears, and then a greater increase in grade strength is often observed in concretes. with antifreeze additives. Here's a grandmother and a decrease in strength.

However, do not forget about the abnormal% introduction of additives into concrete. This is where potential troubles lie. Here the conversation can drag on if you start to remember all sorts of early freezing techniques, etc. Therefore, we will manage with two replicas. With insufficient introduction of PMD, the mixture freezes, the cement hydration process stops and resumes only with the arrival of a temperature sufficient to thaw the frozen liquid. In most cases, this is painless. Unless, of course, this is not a bridge and not a load-bearing crossbar, which they managed to load with something heavy during the winter.

In completely free-of-charge concretes, accidentally frozen during a sharp drop in temperature, the situation is somewhat worse, but also quite tolerable, provided that the cast structures are not loaded. However, much depends on the size (volume) of the cast concrete products. Again, it is important - when exactly the concrete froze: at what stage was the cement, whether critical strength was gained; whether water (rain, melting snow) affected the weak concrete surface, etc. Here, perhaps, a loss of strength is possible on average up to 20% and in some cases a decrease in frost resistance up to 50 percent, peeling of the upper layer, erosion, etc. is also observed.

If we consider the results of laboratory and field tests, we can conclude that the antifreeze additive for concrete (especially complex) has a positive effect on the resulting characteristics of a concrete structure, or reinforced concrete. The density (water impermeability) increases, a positive inhibitory effect on the reinforcement is promised, the design strength increases in comparison with concrete without additives.

Again, all this is possible under one condition that the additive is not left. If there is no certainty, then the risk is akin to Russian roulette. There is a time-tested Poliplast, but where is the guarantee that this is Poliplast, and not Ravshanplast spilled in a nearby hangar on the construction market. Counterfeiting is our common misfortune. One thing is Cherkizovsky Gucci and Karden, and quite another - when an ersatz product concerns health and construction. If you think about the possible consequences, it becomes a little uncomfortable.

Of course there are many additions. Listing them and describing them is not an easy task. I have mentioned only the most used ones. To the best of my ability and strength, I will try to supplement this page with a description of the compositions that have now been ignored. In the meantime, what is - is. With superplasticized non-freezing greetings, Eduard Minaev.