Features of the use of plasticizing additives in concrete and masonry mortars

To change the properties of the concrete and mortar mixture, as well as to influence the final product (concrete stone), various additives are used in modern construction, namely plasticizers for concrete.

They can be natural, chemical, in liquid form, dry powder or in the form of a concentrated mixture. There are a great many of them today. In this article we will talk about additives called plasticizers.

By and large, three main indicators that supplements are designed to change are:

1. Workability of a concrete or mortar mixture.
2. Water permeability of hardened concrete stone.
3. Strength characteristics of concrete.

The struggle to improve these properties has been going on for more than 50 years with the help of additives, namely plasticizers.

Why do you need a plasticizer?

Plasticizing additives are organic or inorganic substances that, when added to concrete or mortar mixtures, significantly increase its mobility.

The mobility of the mixture is measured using an Abrams cone and is designated by the letter P with numbers from 1 to 5. This device is exactly 100 years old.

It is a hollow metal cone with a diameter of 20 cm at the bottom, 10 cm at the top and a height of 30 cm, into which a concrete or mortar mixture is compacted with a special rod and, when removed, the settlement of this cone is measured in cm.

Based on the settlement indicators, there is a gradation of the mixture mobility scale, or there is another term - workability.

The P1 value is assigned when the cone draft is 1-4 cm, and P5 is more than 21 cm. Why am I going into such detail with this technical term, and here’s why - if there is a low mobility indicator, the mixture cannot be supplied through the hoses of a concrete truck and it will not be possible to fill complexly reinforced structures

It should be noted that when adding plasticizers, there is regulatory documentation that controls the loss of concrete strength from their use.

Namely, no more than 5% loss of strength when adding a plasticizer, which is determined in laboratory conditions by the strength of concrete or mortar cubes (100x100x100 cm) after 28 days of hardening at a temperature of (20±2) C and a relative humidity of at least 95%.

Types of additives

Additives are products that, after being introduced into concrete mixtures or treating the surface of finished concrete, improve their technical and construction characteristics.

• Additives for concrete, depending on the type of effect on its structure, can be chemical and mechanical, which include all types of reinforcing fibers, as well as finely ground fillers.
• Additives vary in release form into liquid, powder, paste and granular.
• Methods of using additives: introducing into the mixture or applying to the surface of hardened ready-mixed concrete.
• An additive to concrete and mortar can be of directed action or complex, combining several types of effects on concrete.

All additives (according to GOST 24211-2008 “Additives for concrete and mortars”) are divided into 4 groups:

1. Products for adjusting the characteristics of concrete mixtures. These include: plasticizing, water-reducing, stabilizing, increasing the air (gas) content and regulating the mobility of solutions additives.
2. Products for adjusting the characteristics of concrete. These include: increasing strength, frost resistance, protective properties, corrosion resistance, regulating the rate of solidification, reducing permeability and expanding additives.
3. Additives that give concrete additional properties: frost resistance, moisture resistance.
4. Mineral supplements.

Let's take a closer look at what additives are used to correct the characteristics of concrete mixtures and ready-mixed concrete.

Plasticizers

To increase the plasticity of the concrete mixture and improve the performance characteristics of concrete, plasticizers are used. These products have taken the first place in popularity among supplements due to their effectiveness. In addition, the price of the compositions is quite budget-friendly.

What effect does the use of plasticizers have:

• It becomes possible to reduce cement consumption (up to 15%).
• The strength of concrete increases.
• Adhesive characteristics are improved.
• The concrete mass becomes more fluid and plastic, easier to fill hard-to-reach places.
• Improves water resistance and resistance to low temperatures.

Popular plasticizers:

1. Plasticizer C3: improves the homogeneity of the mixture, its mobility, resistance to moisture and frost, increases strength characteristics, reduces cracking and shrinkage of concrete.

Plasticizer C3

1. Relaxol.

Relaxol additive for concrete

"Relaxol" is a complex additive for concrete solutions. It increases the mobility of the mixture, increases its workability and frost resistance, reduces the time to gain stripping strength and cement consumption.

Available in liquid, paste and dry form. Before use, paste and powder are diluted in water (in proportions as prescribed by the manufacturer's instructions).

Additives for adjusting hardening time

When carrying out work on the production of monolithic concrete structures, it is important to ensure continuity of the process, since otherwise, it is necessary to process the joints of old and fresh concrete, which leads to additional labor costs.

The way out of the situation is to use additives to slow down the hardening of the solution. Another area where it is necessary to slow down the setting process is long-term transportation of the prepared mixture to the work site.

The introduction of additives that retard setting makes it possible to slow down the hydrolysis and hydration of the clinker components, and increase the hardening time of the solution, or quickly bind the free lime present in the composition.

Popular retarders:

• One of the actively used moderators is nitrilotrimethylenephosphonic acid, as well as the additive RSB-500 (ISB-500), which is based on this acid. The additive does not contain alkali, the presence of which leads to corrosion of the reinforcement. It is introduced in the amount of 0.02...0.15% by weight of cement.
• Addition VZ 6. These additives for foam concrete and light mortars have a powerful retarding effect. Consumption: 0.2...0.7% by weight of cement.
• Sodium gluconate, molasses, whey.

The opposite situation may arise when it is necessary to reduce the time of the technological process when curing concrete in natural conditions. For these purposes, setting accelerators are used to activate hydration.

Typically these foods are electrolytes. They are added to concrete mixtures in an amount of 0.5-3% by weight of cement.

Concrete additive to accelerate hardening

Brands of accelerators used: Addiment BE 2, BE5, BE6, potassium carbonate, calcium chloride and nitrate, Cementol Omega P.

Seals

Sealing additives (also called sealants) fill the pores of concrete with elements that do not dissolve in water. They increase the density of concrete, its durability, resistance to water and aggressive environments.

Such additives can be finely dispersed mineral fillers (iron sulfate, chloride and nitrate, calcium nitrate - their dosage should not exceed 3%), as well as water-soluble resins: diethylene glycol resin DEG-1, polyamine resin S-89, triethylene glycol resin TEG-1 ( dosage 1-1.6%).

Strength Additives

The strength of concrete can be increased by using plasticizers and stabilizers. Also, reinforcing additives, which are fibers made from steel, basalt, cellulose, polypropylene and other materials, are effective in strengthening the structure of concrete.

Concrete reinforced with microfiber becomes more elastic, resistant to mechanical damage and wear. The service life of such structures increases significantly.

Fiber reinforced concrete

Stabilizers

The introduction of stabilizers into concrete mixtures helps reduce the stratification of the mixture, achieve optimal viscosity, increases its homogeneity, and prevents dye from leaking out. Such compositions include: Sika Stabilizer 100, Alphalith Stabilisierer F1 (ST), MPD-10.

Additives to increase the protective properties of concrete

The reinforcement used in the production of concrete structures corrodes over time. Additives are produced that increase the protective qualities of concrete in relation to reinforcement and prevent reactions of the metal and the environment: sodium nitrite, calcium nitrite-nitrate, potassium dichromate, etc.

Potassium dichromate

Additives for gas formation, foam formation and air entrainment

To create closed air pores in the concrete body, which must be evenly distributed throughout the entire volume, air-entraining additives are used. Such additives are: salts of organic, petroleum, lignosulfonic acids, tree resin, detergents (synthetic).

Air entrainment can be accomplished using: saponified wood pitch (introduced in an amount of 0.005...0.035% of the cement mass), saponified wood resin (0.01...0.08%), neutralized air-entraining resin (0.005...0.05%), etc.

Saponified tree resin

Additives that involve air in concrete are actively used to increase the frost resistance of the material, resistance to cracking, tensile strength and to reduce the density of expanded clay concrete.

By using gas-forming additives, a microporous structure of concrete is obtained. Gas formation occurs when aluminum powder and organosilicon additives (GKZh-94) are added to the concrete mixture. The rate of introduction of such additives varies from 0.03 to 0.08% of the weight of cement.

Gas-forming additive for concrete

Concrete with gas-forming additives has increased durability, water resistance, resistance to salts, and tensile strength. Protein and synthetic foaming agents are used to produce foam concrete.

Additives to concrete for foaming

Additives introduced into foam concrete allow you to “foam” the concrete mixture and create closed cells. Unlike aerated concrete with unclogged pores, foam concrete has greater frost resistance.

Additives for gas and foam formation can be made with your own hands, but it is better to turn to products tested and certified by manufacturers.

Pigments

Concrete structures have little aesthetic appeal. If necessary (for the production of building materials and small architectural forms), you can use pigments to color concrete and obtain a product of the required color.

Dyes are available in powder, paste and liquid form.

Concrete dyes

The following types of pigments are distinguished:

• natural (obtained after mechanical processing of raw materials);
• artificial (heat treatment is used in their production);

When choosing pigments, you should pay attention to the following characteristics:

• degree of grinding of the powder (the size of the particles most directly affects the uniformity of color);
• oil absorption (paint durability depends on it);
• resistance to ultraviolet radiation (the higher it is, the less likely it is that the aesthetic qualities of painted materials will change under the influence of sunlight);
• resistance to alkalis (characterizes the dependence of the pigment on the action of alkali in the concrete composition);
• hiding power (the ability of a pigment to cover the base color of concrete).

Important! If it is necessary to obtain a bright color of the product, white cement should be used in the production of concrete.

There are two methods used to color concrete:

• Coloring is still done at the stage of preparing the mixture. In this case, the product will be painted completely, throughout its entire volume. Its appearance will not change during operation, despite possible damage and abrasion. The cost of such processing is significant, since a lot of pigment is required.
• Applying dye to the finished concrete product. Products are used that can penetrate 0.5...2 mm into concrete. Such materials are applied with a roller or spray, and also rubbed in with a spatula.

Two methods of staining concrete

A special feature is the coloring of concrete products with acid pigments. This is one of the most popular products. Coloring occurs after the dye reacts with cement. By using an acidic material, you can achieve an antique effect on concrete.

Acid dyed concrete

Hydrophobizing additives

These compounds are introduced to impart water-repellent qualities to the mortar and concrete.

There are two types of product:

1. Siliconates that dissolve in water. They are used in the form of water-based solutions.

Such products include:

• GKZh-11 (introduced into concrete in an amount of 0.02% of the weight of cement);
• GKZh-10;
• "Siakor" (powdered analogue of the first two liquids).

Water repellent GKZh-11

1. Siloxanes, silanes, silicones, insoluble in water. They are used in the form of emulsions or solvent-based formulations.

The most popular product in this segment is water-repellent liquid 136-41 (GOST 10834-76). It can be used both for surface treatment of concrete and for introducing an additive into the solution. Dosage: 0.02…0.1% by weight of cement.

In addition to water-repellent properties, this hydrophobic additive increases the frost resistance of concrete and its plasticity.

Water permeability of concrete

This is a very important indicator that affects the strength characteristics of concrete, since, having a porous structure, water penetrates into these voids and, at subzero temperatures, expands and breaks the cement stone.

This process is directly related to the durability of structures. And voids are formed after water evaporates, that is, the higher the water content in the concrete mixture, the more porous the structure the structure will eventually have.

Here we come to such an indicator as the water-cement ratio - this is the ratio of the mass of water to the mass of cement per cubic meter of mixture.

There is a certain value for this indicator - 0.4, which is considered sufficient for complete hydration of cement in the body of the stone. But working with such a consistency is very difficult, but you have to strive for it.

The smaller this value, the less porosity of the cement stone will be, the more durable our structure will last.

So, this indicator can be reduced by using plasticizing additives. It is they that make it possible to reduce the water permeability of concrete for the reason that less water is required to obtain the required strength.

By increasing the fluidity of the concrete mixture, we improve its ability to fit into the required form or formwork, eliminating the formation of voids with dense reinforcement. In this case, plasticizing additives play a crucial role.

For this most important property of concrete to resist water permeability, there is a separate GOST 12730.5-84, which actually normalizes and is designed to control the water resistance of concrete.

This GOST describes in detail the tests of hardened concrete and mortar samples and, depending on the results, they are assigned a water resistance class from W2 to W20. Water resistance increases with increasing digital value.

We will not consider test methods; this is a rather complicated procedure. Let's just say that the most popular indicator for water resistance of all produced concrete is W6.

Need for use

The feasibility of using a plasticizing additive is explained by the required results that need to be obtained in the production of reinforced concrete products, as well as to increase economic efficiency during their operation.

The need to use a superplasticizer is indicated in the following situations:

1. In the case of obtaining concrete grade M600 using Portland cement grades 400-500 (technological requirements of the project, etc.).
2. To reduce cement consumption.
3. When replacing coarse-grained aggregate in mixtures with a less durable fine-grained one.
4. To increase the stability of structures under axial tension and compression without increasing the consumption of binders.

Positive characteristics of the supplement

The substance has the following advantages:

Characteristics of plasticizer for concrete mixture.

• increases concrete mobility indicators up to P5;
• improves the plasticity of the solution (workability) by 1.5 times;
• reduces the W/C ratio by 25%;
• increases the strength parameters of products by 25%;
• hydrophobic properties - W10 and higher;
• frost resistance value - F300;
• the adhesion of mixtures to steel reinforcement increases by 1.7 times.

Negative effects of using C 3

Disadvantages of the modifier:

1. When the additive is introduced into concrete solutions, the mobility of the mixtures increases, but the rate of their hardening decreases. To stabilize this indicator, you need to use an additive together with a setting accelerator.
2. The superplasticizer is toxic and according to its characteristics is classified as hazard class 3. The substance may have an irritating effect on the respiratory system, mucous membranes of the eyes, and unprotected skin.
3. Due to the presence of sodium sulfate in the additive, there is a risk of efflorescence on the surface of the products.

Workability

This indicator is also of paramount importance for concrete mixtures. Scientists have figured out that for complete hydration of cement, that is, for its complete hardening, a water-cement ratio of 0.25 is sufficient, but such a mixture cannot be placed normally in a mold or formwork.

Therefore, the amount of water is increased to a value of 0.5, in other words, the strength characteristics of the final product are deliberately worsened in pursuit of workability. But if you add a plasticizing additive, you can reduce the water-cement ratio to 0.4, which will give a 20% effect.

At the same time, the number of voids and capillary networks in the cement stone will be reduced. The workability or mobility of the mixture, which I wrote about in detail above, will be controlled using plasticizing additives.

Purpose and application

Superplasticizers are universal additives that provide good workability and positive dynamics of hardening of mixtures.

Using a plasticizer for concrete floors.

Modifiers of this group are used to produce plastic, highly mobile concrete mortars (P1-P5) without weakening the strength characteristics, as well as to improve the following properties of reinforced concrete structures:

• waterproof;
• frost resistance;
• wear resistance;
• resistance to chemical influences;
• heat resistance.

In fact, this list can be continued. The number of additives with different principles of action is incalculable. The most popular of them is superplasticizer C3. It is available in the form of brown powders or liquids.

Has proven itself in the manufacture of the following products:

• concrete floors;
• paving slabs;
• garden paths, etc.

The volume of consumption and consumption of the product is determined by the operational requirements for finished concrete structures.

Types of plasticizers and their characteristics

In accordance with GOST, plasticizers are divided into plasticizers and superplasticizers. As the name suggests, the plasticizer affects the plasticity of the concrete mixture and this is its main purpose.

By improving plasticity, it affects water demand, and we have already discussed this effect earlier.

Plasticizers are surfactants that belong to the class of lignosulfonates.

The chemistry of the interaction of these substances with clinker cement particles is quite complex; it consists in lowering the surface tension of water and entraining air into the solution.

The most famous plasticizer is simple soap.

Plasticizers are produced in the following states:

• liquid, ready-made solution;
• pasty, concentrated solution;
• powder.

Superplasticizers are substances that not only have a great effect on the plasticity of concrete and mortars, but also contain components that further improve its properties such as:

• air entrainment;
• hydrophobization;
• frost resistance;
• hardening accelerators;
• hardening retarders;
• corrosion resistance of reinforcement and concrete.

This complex use of surfactants in modern construction allows us to talk about a hyperplasticizing effect.

They increase strength, improve the spreadability of the mixture, which makes it possible to pour densely reinforced structures, and increase the corrosion resistance of both the reinforcement and the concrete itself.

One may wonder why such mutually exclusive properties as accelerating hardening and retarding hardening are needed.

This will depend on the pouring conditions and the distance from the concrete manufacturer's plant to the site. If the distance is long, then a retarder is needed, and if you need to quickly disassemble the formwork according to the project conditions, then an accelerator must be used.

Material characteristics

Plasticizers have a low degree of volatility and are highly compatible with materials. The additive has no odor, the chemical composition does not affect the color of the material. This applies only to high quality raw materials, which do not release alkali during the mixing process.

Characteristics of certain types of plasticizers:

• can help improve fire resistance;
• resistance to ultraviolet radiation;
• improving heat resistance.

Some of the products may be highly specialized, but each of them increases the strength properties.

Review of plasticizer manufacturers

On the market of chemical plasticizing additives for concrete and mortars there is a multiple offer from both foreign and domestic manufacturers. But first things first.

Sika Sikament BV-3M (Switzerland)

• The plasticizer is used for concrete grades M50 to M400. The scope of application of concrete is quite wide - foundations, grillages, self-leveling floors, floors and much more.
• Does not contain toxic substances. If it gets on a worker’s body, it is enough to wash it off with soap and water without fear.
• Allows you to reduce cement consumption by up to 15%. You can add other additives to it; it interacts well with them without harming the concrete mixture.
• It does not cause corrosion of reinforcement, since it does not contain chlorides, which is very important for densely reinforced structures.
• Consumption from 0.4 to 1% by weight of cement.
• Cost of 5 liters – from 528 rubles.

Cemmix CemPlast (Russia)

• Superplasticizer has all the same advantages as the previous position, but it is necessary to note this feature of this additive - it has biocidal properties. This is the ability of a substance to prevent biological organisms from developing. This quality is necessary for concretes that are used in the construction of structures in humid environments, such as sea piers and jetties.
• Consumption up to 1% by weight of cement.
• Cost 5 liters – from 474 rubles.

Isomat Plastiproof (Greece)

• Waterproofing additive with plasticizer properties.
• Excellent for concrete that is used for structures such as underground passages and foundations where water pressure is present.
• Does not contain chlorides, consumption 0.2 – 0.5 kg per 100 kg of cement.
• Cost 5 liters – from 1140 rubles.

Material consumption

The consumption of plasticizer for concrete depends on its release form. For example, a liquid additive must be measured in a ratio of 0.5-1 liter per 100 kilograms of cement used for the construction of walls, floor screeds, and ceilings. 1-2 liters are needed per 100 kilograms of cement for self-compacting concrete, used for pouring foundations and forms for complex reinforced concrete load-bearing structures.

Dry plasticizer is presented in the form of a powder, which must be added to the source material, after diluting it with water. The solution should have a concentration of 15-35%.

To determine how much plasticizer to add to concrete, you must use the dosage indicated on the packaging, since manufacturers may indicate different proportions of additive use.

To finally determine the concentration of the plasticizing additive, it is necessary to find out how much cement will be used to prepare the mixture. Household concrete mixers are designed for 10-15 kg of cement, so it is more convenient to use a standard container, for example, a liter jar. If the packaging indicates from 0.5 to 1%, the optimal proportion of plasticizer for concrete will be approximately 0.7%.

S – 3 (Russia)

• The famous superplasticizer, which appeared back in 1980 in the Soviet Union based on naphthalene sulfonic acid and formaldehyde.
• Allows you to obtain cast mixtures with mobility P4, P5.
• It makes it possible to reduce cement consumption by up to 25%, and also change the brand of Portland cement from M500 to M400.
• Sold in liquid and powder form.
• Compatible with all types of additives.
• When freezing, the solution does not lose its original properties.
• Mixed into the mixing water of the second addition.
• The powder must first be dissolved in water.
• Consumption: for mobile concrete and mortar mixtures – 0.2-0.8% by weight of cement; for self-compacting mixtures - 0.8-1.2% by weight of the binder.
• The cost of a 25 kg bag is from 2400 rubles.

Tips for use

The method of application of additives is determined by the form of release. Plasticizers are dry and liquid. The second option is divided into ready-to-use solutions and concentrates. The product must be diluted in warm water so that the chemicals are activated more quickly. Next, the mixture is poured into water, which is intended for mixing the solution.

How to mix the right concrete. Is a plasticizer needed?

To prepare the solution, choose a grade of cement that is twice the grade of concrete.

Manual mixing can be performed when working with cement grades up to M350. In other cases, it is necessary to use a concrete mixer or other equipment.

The process of preparing the solution manually consists of the following steps:

1. Dilute the plasticizer in a small container, following the instructions. To obtain a homogeneous liquid, it is recommended to use a construction mixer. They are diluted with active chemical compounds for 15 minutes.
2. Mix the aggregate with cement in a large container.
3. Pour the diluted plasticizer into the water and mix everything.
4. Add liquid to the cement mixture in portions until you reach the desired consistency.

You can make the batch in a spacious container and directly on a metal sheet that has small sides.

When kneading in a container, we adhere to the following sequence:

• Place sand in a heap along the center of the sheet;
• make a depression in the middle;
• fill the resulting hole with cement;
• using a shovel, mix the dry ingredients;
• Dilute plasticizer in water;
• using a watering can, add liquid while constantly stirring the components of the composition;
• add crushed stone, mix;
• add the required amount of water, thoroughly mixing the solution.

A certain amount of water is used to prepare the solution. It is prohibited to add liquid to the prepared mixture.

Proportions of the components of the solution, taking into account its purpose
Purpose	Water	Crushed stone	Sand	Cement
For floors, paths	0,5	5,7	3,5	1
For strip foundation/walls	0,5	3,7	1,9	1
For fences/garages/foundations	0,5	4,8	2,8	1
Preparation of a quickly hardening mixture of increased strength	0,5	2,7	1,2	1

Clean water is used for mixing. Ideally, it will not contain any third-party impurities or fillers. Sand is chosen from large and medium fractions, crushed stone – fine. The cement must have an appropriate shelf life. An expired product should not be used to prepare the solution.

Self-preparation of superplasticizer S-3

We weigh 366 g of plasticizer in brown powder on a scale. We also measure out 634 g of clean water. The water should be hot up to 90 C.

Gradually adding the powder to the water, you must constantly stir so that it does not have time to crystallize.

It is better to use a mixer or a drill with an attachment.

The proportion to the concrete mixer will depend on its capacity and, most importantly, the weight of the cement. Approximately 1% of the mass of cement is suitable for pouring the foundation of a house with M200 concrete.

Features of the use of additives during masonry work

When carrying out construction work, it is important to separate additives depending on the structures where they are to be used. For example, during monolithic work, pouring foundations, floors, and load-bearing columns, it is important to achieve the design structural strength. While masonry mortar does not need excess strength.

Kirill Lebedev

There are a large number of different plasticizers. You cannot thoughtlessly use the same additives for masonry and concrete work, because... they differ from each other in chemical composition. Also, additives differ in the “power” of their action and their effect on the viability of the solution and mixture. The similarity of all plasticizers is that they reduce the amount of mixing water, but completely different requirements are imposed on concrete for the foundation and on the masonry mixture. If you neglect this rule, you can get a negative result, which will lead to big problems.

When doing masonry work, the mason needs the mortar to be easy to work with. The solution should be light and airy, as they say “reach for a trowel.”

For this purpose, additives are used that provide not only plasticity, but also increased air entrainment. This leads to a decrease in the strength of the mortar, which is not needed by builders when laying facing bricks.

The usual strength limit for mortar when laying facing bricks is up to M150.

Special additives for masonry increase the yield of the finished mortar. For example, without an additive you can get 200 liters of solution from an equal volume of components, and with an additive it is already 230-240 liters.

Important: If you use an additive for masonry mortar when concreting a foundation, where the density of concrete is important, this can lead to a significant decrease in the strength of the structure. Those. instead of the planned M350, you can get concrete M100-M50. As a result: the foundation will not be able to withstand and redistribute the load on the ground from the overlying structures and will have to be dismantled.

Conversely, additives for concreting should not be used when carrying out masonry work, because they will not ensure lightness, airiness of the mixture and long life of the mortar, which is important for masons.

Briefly about the main thing

1. The most important formula for a concrete and mortar mixture will be the water-cement ratio (W/C). The lower this indicator, the stronger the structure will be after hardening. You need to strive for an indicator of 0.5.
2. An ideal W/C can be achieved by using plasticizers and superplasticizers. Plasticizers will also help reduce cement consumption, and, consequently, the cost of construction work.
3. When preparing mixtures using chemical additives, you must use protective equipment to protect yourself from damage and toxic substances getting into the respiratory tract and eyes. In case of contact with skin, wash off with soap.
4. Stir the plasticizer first in water, and only then add it to the concrete mixer. Water for diluting powder or paste plasticizer should be heated to 60-90 C.

As always, we look forward to your questions and advice.

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What problems can be caused by using liquid soap as a plasticizer?

Detergents, indeed, make the concrete mixture more plastic and prevent its delamination and sedimentation of aggregates (sand and crushed stone), but this occurs with the entrainment of air into the solution. The result is less dense concrete with reduced strength, as a laboratory experiment clearly demonstrates.

Compressive strength of concrete. Laboratory experiment

4 samples were made with the expected concrete class B15, of which:

1. the solution is made according to GOST;
2. 25% more water was added than required by GOST;
3. 50% more water was added than required by GOST;
4. water was added according to GOST, liquid soap was used as a plasticizer.

After production, the samples were matured in a chamber for 3 months, then they were weighed and tested.

It turned out that the sample with detergent is the lightest (with the same sample volume), which means its density is reduced. In addition, even an increase in water by 50% did not result in such a critical reduction in strength.

Important!

Problems caused by the use of liquid soap will not appear at the stage of mixing and laying concrete, but much later. Wet, crumbling concrete and rusty reinforcement will attract attention when it is no longer possible to change anything. Are the small savings worth the hassle?

Additional recommendations

Experienced professionals suggest listening to the following recommendations:

• Surfactants are introduced into the working mixture after preliminary dissolution in water;
• It is better to use components that do not produce a lot of foam. Otherwise, you need to wait for it to shrink;
• Lime mortars are recommended for use in places with high humidity. They have waterproofing properties, as a result of which the base and foundation of the house are protected, wear resistance and resistance to temperature changes are improved;

How does a plasticizer affect the operational strength of concrete mortar?

When pouring a floor, laying ceramic tiles or forming a screed, provided that the proportions are observed and the optimal composition is selected, a plasticizer for cement mortar will increase the operational strength of the monolith.

This task is achieved by undergoing a chemical reaction as follows:

• the density of the mixture increases (while the formation of air pores becomes significantly more difficult);
• water content is reduced for higher resistance to mechanical damage;
• the elasticity of concrete increases, simplifying the pouring process (while the likelihood of voids forming is minimized).

The additive allows you to achieve optimal viscosity by introducing a smaller volume of water. The concentration of superplasticizer for concrete is 1-1.5%.

DIY making

Soap can be replaced with lime.
To reduce construction costs, it is permissible to make plasticizers yourself. You can easily make a plasticizer for concrete at home with your own hands. The simplest way to improve the properties of a masonry composition is to add liquid soap or washing powder, slaked lime or liquid glass. Only the builder can determine how much of this or that component is required. Everything is strictly individual.

Soap gives the necessary plasticity and uniformity, increases the hardening time. Do-it-yourself plasticizer is the most economical and easily accessible. You can replace soap with slaked lime. It gives elasticity and stickiness to the solution, which is important when working in difficult areas. When using lime, masonry is smoother and more uniform.

Liquid glass helps to increase the stability and waterproofing of finished structures. To do this, liquid glass is mixed with water in equal proportions and then added to the concrete. However, this composition is destroyed when exposed to carbon dioxide, so it is better to apply at least two layers of plaster. Approximate addition instructions: before mixing, add 200 ml of liquid soap to a bag of cement with expanded clay. This proportion is sufficient to increase the hardening time to three hours.