When can you walk on a heated floor screed after pouring?

First, let's find out what this process is - the setting of concrete, how it proceeds from the point of view of chemical reactions and a physical model (see also the article “Concrete columns - an important element of construction”).

Let us clarify: strictly speaking, all processes in concrete are more correctly called cement hydration. For obvious reasons, much more chemically resistant quartz sand and crushed stone are not involved in the reaction.

Chemical model

When Portland cement comes into contact with water, several chemical processes are simultaneously launched, which boil down to the transformation of oxides and salts of aluminum and calcium into, respectively, hydroaluminates and hydrosilicates.

The main reactions are as follows:

• 3CaO*Al2O3+6H2O -> 3CaO*Al2O3*6H2O.
• Ca2SiO4+H2O -> Ca2SiO4*H2O.
• 3CaO*SiO2+H2O -> 3Ca2SiO4*H2O+Ca(OH)2.

All three reactions occur with the release of a small amount of heat. Complete hydration of cement requires mixing it with water in a ratio of 1:0.4; in this case, approximately 60% of the total amount of water is involved in the chemical processes themselves. The rest of the liquid remains locked in the cells of the future concrete, forming its porous structure; it will evaporate over several weeks or even months.

In parallel with the hydration of the minerals that make up cement, several slower reactions occur in the concrete mass, which gradually lead to the concrete gaining grade strength:

• Slaked lime Ca(OH)2 in combination with carbon dioxide gradually turns into strong and slightly soluble calcium carbonate CaCO3.

Several minerals, mostly consisting of calcium carbonate.

• The addition of silicon dioxide to this reaction produces equally strong and stable calcium silicates.

Physical model

What does the process look like from the point of view of the physical processes occurring in the concrete mass?

Schematic representation of the different stages of cement hydration.

Construction myth No. 2. Do I need to wait 28 days after pouring concrete?

Question: How long does it take for concrete to harden?
How and over what time does concrete gain strength? Is it really necessary to wait 28 days after concrete is poured? When can concrete structures be loaded? It is more profitable for every developer or builder to construct a structure, building or structure in the shortest possible time. But there are a number of opinions that it is necessary, after completing concreting work on structures, to wait until the structure “hardens” in order to then proceed to the next stage of construction.

How and over what time does concrete gain strength?

Do I need to wait 28 days after pouring concrete?

For a correct conclusion, it is necessary to analyze regulatory documents and determine the mode, stages and timing of construction.

When performing concrete work, they are faced with two pressing issues:

Let us consider these questions one by one.

For precast concrete products, it is very important to determine the tempering strength .

Tempering strength is the accumulated strength of concrete, established by standards, at which a reinforced concrete product can be delivered from the factory to the construction site.

The value of tempering strength is established in accordance with GOSTs or other regulatory documents depending on:

Below, in Table 1, depending on the type and class of concrete, the average values ​​of tempering strength are given as a percentage of the design strength.

So, the tempering strength of prefabricated reinforced concrete products, depending on a number of factors, is 50÷100% of the design value. Conclusion No. 1: when the tempering strength is achieved, it is possible to install and then load reinforced concrete structures, with the expectation that full loading (100%) will occur no later than 28 days from the date of manufacture of the products. A more specific procedure and timing of loading prefabricated structures is stipulated in the PPR (work execution plan).

Also in construction there is such a thing as stripping strength .

Stripping strength is the minimum accumulated strength of concrete at which it is possible to remove the formwork without damaging the concrete. For precast concrete products, the formwork strength must be sufficient for safe transportation. The conditions and rate of strength gain for each product or structure are determined by the manufacturer.

Under construction site conditions, when manufacturing monolithic structures, formwork is usually removed immediately before loading the structure.

SNiP 3.03.01-87 establishes the following conditions for stripping reinforced concrete structures (see table 2).

Russian regulatory document TR 80-98 “Technical recommendations for the technology of concreting monolithic structures using a non-heating method using a thermos and an accelerated thermos” provides the following permits for stripping and loading of structures, Table 3.

Required concrete strength for stripping and structural loading:

Notes:

Further measures to carry out formwork work and the movement of workers on reinforced concrete structures are allowed when the strength of the concrete is 1.5 MPa or more. (SNiP 3.03.01-87 , clause 2.17). Also, in this regulatory document there is an indication (clause 2.110) that when using intermediate supports (props) to cover spans, with partial or sequential removal of formwork, the permissible stripping strength can be reduced, which means a greater turnover of formwork and a reduction in construction time . More specific measures for early removal of formwork should be determined based on specific construction conditions and covered in the PPR.

Some literature sources indicate the following values ​​for stripping reinforced concrete structures, table. 4:

Conclusion No. 2: based on all of the above and analyzing all the tables on the stripping strength of concrete and its loading, the stripping strength is within 50...80% of the design. Then:

How long does it take for concrete to gain stripping strength, at which point it can also load the structure?

As mentioned above, under different conditions (temperature, humidity, precipitation, etc.), different concrete gains strength in different ways. In Fig. Figure 2 shows a graph of the rate of strength gain depending on the temperature of HTW (heat of moisture treatment).

The graph shows that in laboratory conditions at a constant temperature of 60°C, concrete acquires average stripping strength (70%) in 32 hours (1.3 days), and at a temperature of 30°C it acquires in approximately 4 days.

Since at construction sites the ambient temperature fluctuates throughout the day, take into account the average daily temperature, which in summer is 18...28°C, and in autumn reaches 5...10°C. At these temperatures, concrete will gain strength much more slowly.

Rice. 1. Graph of the speed of concrete strength development depending on the temperature of the HTW (heat of moisture treatment) [1]

At enterprises producing concrete and structures from it, there must be schedules for the strength gain of concrete of a certain composition. To roughly determine the strength of a particular concrete, you can use graphs of strength gain depending on the type of cement, temperature and class of concrete (Fig. 2) from regulatory documents [2, 3].

Below is the increase in concrete strength depending on the ambient temperature or HME, (in% of R28):

a) class C15–C25 based on Portland cement grade M400

b) class C30 based on Portland cement brand M500

c) class C15–C25 based on Portland slag cement grade M400

d) class C40 based on Portland cement brand M600

e) fast-hardening highly active Portland cement (BTC)

Strength development schedules (Table 5-9)

Strength gain of concrete class C15 - C25 on Portland cement grade M400 (% of R28):

Strength gain of concrete class C30 on Portland cement grade M500 (% of R28):

Strength gain of concrete class C15 - C25 on Portland slag cement grade M400 (% of R28):

Strength gain of concrete class C40 on Portland cement grade M600 (% of R28):

Strengthening concrete using antifreeze additives:

Conclusion No. 3: from the graphs and tables it is clear that concrete based on Portland cement at an average daily temperature of 10 and above gains 50% of the design strength in 5...7 days, and concrete based on Portland slag cement gains under the same conditions - in 14 or more days. In winter, at sub-zero temperatures, even with the use of anti-frost additives (Table 9), concrete gains design strength in 90 days or more. To speed up the time required to gain the required strength during winter concreting, it is necessary to use electric heating.

For rapid strength gain, according to SNiP 3.03.01-87 “Load-bearing and enclosing structures . 2 . Concrete work" (clause 2.15) concrete requires appropriate care. Caring for concrete begins immediately after placing it in the formwork and continues until the formwork is removed. Concrete should be stored from direct sunlight, precipitation, wind, and heat and humidity conditions should be created for it to harden (cover with film). It is recommended that concrete made with Portland cement be watered for 7 days, and concrete made with low-active Portland cement and slag cement be watered for at least 14 days. At an air temperature of 15°C, it is recommended to water the concrete every 3 hours during the first 3 days. At an average air temperature of +5 to 0°C, watering and wetting of concrete is not carried out. Full load (calculated) of reinforced concrete structures is allowed only after the concrete has its design strength.

Recommendations for making foundations

I would especially like to focus on the foundation, since there are some features of its operation:

For a more accurate safety net to control the strength of foundations or other reinforced concrete structures, a series of standard cube samples 150x150x150 or 100x100x100 mm are made, which are then tested for compression.

Literature:

Source

How quickly does concrete mix dry?

The use of concrete in many construction processes is an incentive that forces craftsmen to study the characteristics and properties of this material. Without knowledge of the theory, it is impossible to determine the correct proportions of the solution, as well as the time required for the concrete structure to initially set or completely harden. Hardening time is an important indicator for a specialist, since on their basis it is possible to draw up a schedule for further work.

The hardening of a concrete solution is a rather complex chemical reaction. It is called hydration, and its essence is that the original composition in the presence of water molecules is converted into calcium hydrate. The binder component is mineralized, thereby binding the mixture into a monolith.

Concrete poured into formwork goes through two main stages:

The first stage does not last long. It begins shortly after mixing (approximately 2 hours). The setting time of concrete of the most popular grades M 200 and M 300 in private construction at 20°C is 60 minutes. If the air temperature outside is low, but not below zero, then the mixture will begin to set in about 5 hours, and if it is high, then very quickly - in just 15-20 minutes.

Concrete at a temperature of 0 degrees begins to set only after 6-10 hours. This “delay” is due to the weak progress of chemical processes. The setting itself lasts from 15 to 20 hours. At subzero temperatures, the reaction of water and cement stops, which causes irreparable damage to the structure. The mixture does not actually dry, but remains in an inert state until the outside temperature rises to 0°C or higher.

Modern supplements solve the problem of hydration in cold conditions. At the mixing stage, special components are introduced into the solution to stimulate hydration and the occurrence of chemical processes, as well as prevent water crystallization. The product label always indicates the proportions so that the specialist can accurately calculate how much additive is needed at a certain temperature.

The second way to continue hardening at sub-zero temperatures outside is warm formwork. It provides normal conditions for hardening of the mixture, but does not accelerate natural hardening.

If poured concrete outside needs special care during the cold season, then using warm formwork in the summer to speed up hydration is tantamount to deliberate damage to the pour. Hardening will take place 2 times faster, but the solution will be dehydrated, the hydration process will stop, and the structure will not achieve the required quality and strength.

After the first stage, the second begins - hardening. During this stage, the concrete in the formwork dries and gains strength. The control period for hardening is 28 days (at a temperature of 20-22 °C and a humidity of 68%). But it takes months and even years for a concrete structure to reach its maximum strength characteristics.

Construction formulas and existing charts allow you to quickly and accurately determine the percentage of strength. You can calculate the Rn index for concrete whose age is n days (n≥3) using the formula:

Rn = R28(lgn/lg28), where:

• R28 - brand (for example, M 200 or M 300);
• n is the number of days that have passed since the mixture was poured into the formwork.

In this case, the first two days are skipped. For them, strength is not determined. Important control points are the 3rd, 7th and 28th days. It is also known that after 2 weeks the indicator averages 70%.

Freezing on the street

There is no specific answer. Any specialist can only approximately determine the time. The indicator depends on where the structure is created and what its purpose is. Some situations can be considered as examples.

1. Strip foundation for a light fence. The formwork can be removed and construction can begin in 4-7 days.

2. Private house. The grade of concrete for individual construction can be M200 or M300. The strip foundation must gain strength in at least 28 days, and the hardening time of concrete in a monolithic slab will last 1.5-2 months.

3. Dams, bridges and other reinforced structures.

In such cases, the M400 concrete mixture dries for at least 90 days. The hardening process is controlled by specialists. They have instruments that allow you to determine the strength coefficient at any time. Experts calculate the time after which the formwork can be removed without compromising quality.

How long does it take for a concrete screed to dry indoors?

Internal concreting work also requires the implementation of certain recommendations. First of all, it is compliance with temperature indicators. Conditions of 20-23°C are considered ideal. It is imperative to maintain high humidity. As a rule, forced moistening of the screed is carried out. Water is sprayed over its surface.

In a house or other room, a concrete floor takes the same 28 days to dry. But finishing work can be carried out starting from the 4th day.

From sand concrete

When a floor is formed using sand concrete, grade 300 cement is used. It is this composition that is considered the most universal. This material is actively used to produce a solution that can serve as a floor leveler.

To accurately determine the readiness of a screed made of M300 sand concrete, it is necessary to focus on the recommendations for cement compositions. All time parameters are almost the same. You can read about floor screed made of sand and cement.

Acceptable dimensions for different types of screed

Based on the thickness of the screed, rough coatings are conventionally divided into:

1. Thin - from 2 to 7 cm.
2. Thick – from 7 to 15 cm.

Layers less than 2 centimeters are usually made from self-leveling compounds and are not classified as screeds, but as self-leveling floors. And a thickness of more than 15 centimeters is more of a concrete floor with reinforcement.

Design features of screeds for heated floors

Features of arranging a thin floor screed

Thin screeds are used in rooms where there will not be strong point loads when using the floor. Usually these are kitchens, living rooms, bedrooms and other living rooms. Here a layer of 20–50 mm will be sufficient. For corridors and bathrooms, 50–70 mm are already recommended.

Cement

As a rule, the drying time of the cement screed can be determined on the packaging. However, in addition to this, there are many parameters that influence how quickly a floor made of cement will harden. To calculate the time of full readiness, it is necessary to include in the calculation such parameters as the thickness of the coating layer. The duration of readiness is directly dependent on the atmospheric conditions in the room or outside.

After just a few hours, you can walk on the completed screed without causing any harm. However, it is not recommended to carry out cladding measures in this case. The duration of readiness will depend on the temperature, thickness and type of material. The cement screed sets after 10-12 hours.

What does it depend on?

The concrete hardening process lasts from one to twenty-eight calendar days. Much depends on the cement used in the work. The chemical process goes like this: the minerals in the concrete are converted into hydrous potassium silicate. In order for the material to be durable, not to crumble, not to break, it must be systematically soaked with water. Hardening concrete is “capricious”. Rapid setting is determined by several components: temperature, humidity, layer thickness (tamping), etc.

Two main stages of hardening

To achieve the declared qualities, it is necessary to maintain the correct proportions when mixing the solution. Only in this case will the desired strength be achieved. About an hour after pouring the mixture, the process of changing its structure begins. This stage is called setting. How long does it take for the cement mortar to harden before further work is continued?

After a day, the mass becomes so strong that you can walk on it. But it is still far from the declared brand strength. This was only the first stage, called grasping. Next, the hardening process begins. After two days, the mixture gains about 50% strength in the warm season.

It is recommended to begin full operational load and operations for the further construction of the next floor no earlier than 28 days, when the concrete strength approaches 90% as stated. Particular importance is attached to time during the construction of load-bearing structures. If possible, it is better to pour strong foundations a year before the start of main construction. During this time, almost all processes of structure change occur. There will be no significant changes to the geometry of the structure. It is difficult to determine the exact time for complete hardening of a particular cement mortar. It can last for years, but after 12 months these changes do not affect the quality of the building.

Currently reading: Concrete M100: main characteristics and composition

Hardening of concrete at subzero temperatures

In winter, work with concrete is carried out when it is possible to provide hydro- and thermal insulation after pouring the mixture. Due to negative temperatures, hydration slows down significantly, as a result, concrete slowly gains strength. To obtain strength at a temperature of -5°C, it takes 6-8 times more time, compared to a temperature of +20°C.

When working in autumn and winter conditions, it is necessary to strictly observe the curing time. The lower the temperature, the longer it will take to completely harden. Additional mixtures designed for cold weather can speed up the situation.

Source: bibliostroy.ru

Under laminate

Taking into account all the standards, the surface for installing the laminate should not have differences of more than 3 m by 1 m. If you are performing a wet screed under the laminate, then you must use special mixtures that are capable of self-leveling. Thanks to them, it is possible to facilitate the process of preparing the base. You can also use reinforcing fiberglass mesh for leveling. The floor must be poured in small sections and leveled using a special device.

When the screed has dried, you can proceed to sanding. The screed under the laminate takes about 2 weeks to dry. But here everything depends on the layer being laid. The process of installing the laminate is carried out after it has gained 50% strength.

When to start the next stage of work

After erecting the foundation, it is necessary to proceed to the construction of walls and ceilings. It is important to determine whether the structure should stand for a sufficient time so that problems do not arise after commissioning; this depends only on the curing time of the concrete.

To summarize all of the above, the following can be argued against stopping work after a “below zero” cycle:

• increase in construction time;
• the pointlessness of the event if the base is sufficiently compacted;
• the likelihood of cracks and deformations appearing when construction is stopped for the winter.

Under tiles

Most often, a cement mixture is used to level the floor under the tiles. You can walk on this floor within the next 24 hours, but here’s what to do with the finishing. Based on the experience of already experienced people, we can say that the process of installing tiles can be carried out the next day. This is completely harmless, although not entirely advisable. If you entrusted the process of performing the work to strangers, then it is very important to check whether reinforcement was done.

The thickness of the screed to be poured must be at least 4.5 cm. If the required thickness cannot be achieved, then the following measures must be taken: lay a plastic mesh with small cells on the screed. It is sold in rolls at any hardware store. After this, be sure to secure it with nails and cover it with a dry adhesive mixture, which will be used when laying the tiles.

The video shows how long it takes for a floor screed to dry:

One of the questions that arises among builders after pouring floors is how long it takes M300 sand concrete to dry. In other words, how long after pouring should you not enter the room in which the fresh screed was made?

Garage floor

depending on WHAT you will do on this floor. Personally, only concrete suits me. You can do ANYTHING on it, including welding. A simplified option is concrete paving slabs. (Level the surface - not by loosening it, but only by cutting off the bumps so that the soil remains dense, add a little sand and lay the tiles)

The remaining options are not without important drawbacks. Asphalt crumbs really do not like spilled fuel and oils. Boards retain moisture, absorb dirt, are flammable, and small parts can easily fall into the cracks between them. Cast iron stoves are expensive and do not promote electrical safety.

If you don’t care about the environment, then there’s nothing better than asphalt chips, it allows water to pass through itself into the ground and over time it gets compacted like asphalt becomes. For a 3x6 garage, 2.5 cubic meters was enough for me, three is better, of course, and it costs a ridiculous amount of money, but it’s very difficult to spread, for the caretakers trust this highly intelligent matter for a couple of bottles of vodka. Thank you, question: Can you tell me how much land to rent for this business? I poured it directly onto the top, although I had a pencil case, but IMHO there is no difference with a garage, it turned out to be 15-20 cm, but in the end it compacted down to 10 somewhere, maybe it just went into the ground, it’s always dry (this probably depends more on the place) and purely.

In my garage, a wet spot has formed around the perimeter of the car, and it is unknown whether it will dry out in the summer :-). It turns out that you drive into the garage, and all night long dirt and snow fall off from below and fall on the floor. It’s just too lazy to get out every time and clean the bottom before going into the garage. Otherwise there are no problems.

Drying time for concrete bases

Everything is clear with gypsum compounds, now let’s figure out how long it takes for a concrete floor screed to dry. Compared to the previous option, this process will take longer.

Here, for each 4 cm layer, experts recommend setting aside a week and only then starting subsequent finishing. If you decide to use a thicker layer of solution, then add another week for every centimeter.

Based on this information, making simple calculations, you can understand that a screed 8 cm thick will require 12 weeks (until it dries completely).

At home, you can check how well the surface has dried. To do this, take a small piece of thick oilcloth, lay it on the floor and secure it on all sides with tape. After 12 hours, the film is removed and its inside is inspected. If there is no condensation on it, it means that the solution is completely dry and ready for further work.

Seasonality of work

1. A new method of thermal influence in construction in winter is the use of thermomats.

How long does it take to dry at low temperatures? During cold weather, when working with concrete, the possibility of insulating the cement concrete structure from water and low temperature must be taken into account. Negative conditions, like retarders, affect how long the hydration period lasts, create problems with drying, thereby reducing the durability of structures. It is important to observe the time required for the material to reach safe stability. At five degrees of heat, the quality of concrete strength increases five or even seven times compared to twenty degrees of heat.

Concrete is the most affordable and practical material. Setting will take place quickly and efficiently, depending on weather conditions. Novice specialists need to know the answers to two questions: how long does it take for the cement mixture to dry; how much and what additives should be used to make the material last longer.

Source: kladembeton.ru

Optimal conditions

Not only the “drying” period, but also the quality of installation, which affects the further operation of the coating, depends on the creation of optimal conditions for carrying out work on installing screeds under tiles or any other material. To maintain the necessary microclimate, the temperature should not be less than 20 degrees and no more than 26. In winter, the minimum level at which work is possible is 5 degrees above zero. Optimal air humidity is in the range from 58 to 72%.

Drafts, direct exposure to sunlight, and sudden changes in temperature are not allowed. If all conditions are met, then the screed should quickly “set”, and all terms should correspond to the information specified by the manufacturer. The following should be avoided:

It is recommended to spray the screed with plain water at room temperature during the first few days. This creates a "greenhouse effect". Artificial dehumidification is permissible only 3 weeks after installation, provided that the room temperature should not be higher than 27 degrees.

Why does the foundation take time?

The foundation needs a certain amount of time for the cement to hydrate. When mixing the concrete mixture, the binder particles are surrounded by water and a chemical reaction is started, during which needle-shaped crystals begin to form. After about six hours, their number becomes sufficient for spatial connections to begin to form. Visually, this process looks like thickening of the mixture (coagulation).

It sets unevenly, which is due to the selective hydration of clinker minerals and the development of shells around the cement particles. After about 9-10 hours, the cement mixture already has a skeleton formed by calcium aluminates, and an active increase in strength begins, during which a silicate structure begins to form.

Silicates react to the presence of water by forming small crystals, which first combine into a porous structure, which determines the specified strength of the cement stone. Within a day, this structure begins to displace the aluminate structure, and does this for an average of 28 days, during which at a temperature of +20 degrees the concrete gains 100% strength.

The screed is ready for use - how to determine?

The readiness of the coating is determined by two points:

The first stages of processing are carried out almost immediately – within a day. It is important that the entire area is uniform in color and has no deviations.

However, avoid placing large objects with enormous weight on the surface.

An experiment to determine whether the treated surface can be loaded can be carried out at least after a week. If you start doing this earlier, the mixture will begin to collapse, and the work will be pointless.

Recommendations for caring for semi-dry screed:

After completing the work, the screed needs to be covered with polyethylene film 80 - 100 microns thick; a thinner film will also work, but it will be difficult to lay it since it is very light.

not to create drafts in the room during , otherwise this will create premature evaporation of moisture from the screed.

It is recommended to lift the film after 3-4 days and evenly moisten the top layer of the screed , for example, using a watering can. Do not pour water so that puddles form! The main thing is to moisturize, not flood! After the screed is moistened, you should cover it back with film, it is advisable that the film at the joints should be laid with an overlap of 30 - 40 cm.

During the period of work and maturation of the screed at the site, the temperature in the premises should be from +5 degrees Celsius, otherwise the screed assembly process will be stopped and it will be loose.

* If the screed was carried out using underfloor heating systems, they should not be turned on for 28 days , after this time, ventilation should first be arranged in the rooms where the screed was made to remove residual moisture, after which you can systematically increase the temperature of the heated floor system.

When continuing finishing work in rooms where semi-dry screed is applied, the following rules should be observed:

• The next day, do not load the screed with more than 100 kg, free walking is possible;
• The screed can be loaded with more than 100 kg after five days at the earliest;
• You should not throw heavy objects onto a semi-dry screed during the ripening period;
• There is no need to store various types of moisture-absorbing building materials indoors for the first 28 days - dry mixes, gypsum board, wood and similar materials;
• In the first 10 days, you should not install scaffolding, stepladders, or tours on the screed, which can pinpoint the screed during the period of strength gain.

So, we can summarize the recommendations for caring for floor screed:

1. Immediately cover the entire surface of the screed with polyethylene;
2. After 3-4 days, moisten and cover with film;
3. If the heating is turned on in the room, humidify again after 4 days;
4. For the first 10 days, do not load the screed more than 100 kg;
5. For the first 28 days, do not turn on the floor heating system.
6. After the semi-dry screed has hardened and gained strength, it is recommended to apply a layer of strengthening primer to prevent dusting of the screed.

Good afternoon We made a semi-dry screed and covered it with film. Is it possible to leave the film for the entire curing period or remove it after a week? How long can you not ventilate? Electricians are also planning to work in a week, is it possible to stand on a stepladder if you put a 5 eps down. Thank you!

Answers: Administrator “Screed Floor”

Hello. It is better to leave the film for 2-3 weeks; a week after installing the screed, it is advisable to moisten it a little additionally, and also leave it under the film. After a week, electricians can move freely. It is not advisable to ventilate the room for the first week. The screed gains strength in the first 28 days, the curing processes and the formation of cement stone occur only with the required moisture content of the screed.

Please tell me! 19.05 made a semi-dry screed. After a day, we easily moistened it and covered it with film (the windows are closed) After 4 days, we removed the film, moistened it and covered it again (the windows are closed) There is no one at the site (we are not loading it) How many days after moistening (on the 4th day) should we keep the screed under the film? When should you start ventilating (from what day should you not be afraid of drafts)? And is it necessary to further moisten it after removing the film?

Answers: Administrator “Screed Floor”

Hello. It is better not to remove the film for the first 2 weeks; it is advisable to moisten the screed on the 7th day after completing the work; it is not advisable to ventilate it in the first week; the screed gains strength within 28 days.

On Saturday we made a semi-dry screed. On Sunday I watered it and covered it with film. When can you open windows?

Answers: Administrator “Screed Floor”

Hello. If the screed is under film, you can already ventilate the room, but you need to make sure that the screed is moistened during the week.

First week of drying

Having completed the installation, the entire floor should be covered with a thick film.

Immediately after completion of all filling work, the entire surface is tightly covered with plastic film, without leaving any gaps. This is necessary to ensure that the concrete does not dry too quickly, otherwise it will inevitably crack due to uneven drying. With a good polyethylene coating, all the moisture that evaporates will not escape into the atmosphere, but will remain in the floor. This is one of the guarantees that the surface will dry evenly and not become cracked.

If, according to all parameters, it is necessary to make a thick screed in the room, it is advisable to use light mixtures for this. This is necessary in order to remove excess load from floors and other load-bearing structures. But due to the specificity of the composition, the drying process can take a long time. If necessary, a thick screed can be laid in several layers, but it must be taken into account that this method will take even more time. There is an opinion that the thicker the concrete floor, the stronger it is, but this is not true.

Foundation conservation

The ideal season for starting construction is mid or late spring, when the air temperature is already consistently above zero. This makes it possible to build the frame of the house over the summer and autumn, and in the winter or next spring do interior and exterior finishing work. But it doesn't always work out that way. It happens that it was not possible to continue construction immediately, for example, due to lack of finance, and it has to be postponed to a later date, and therefore the foundation has to be preserved.

Expert opinion Vitaly Kudryashov builder, aspiring author

Ask a Question

Some developers believe that the foundation needs time to settle, so they deliberately pour it in the fall in order to continue construction in the spring. This is a wrong opinion, since an unloaded and uninsulated foundation is less resistant to the forces of frost heaving and can become deformed over the winter, losing its exact geometric shape.

• Foundation conservation is a set of measures that protect the structure from atmospheric influences: soaking under the sole, freezing, sudden temperature changes. There is nothing complicated about it, but you will have to make some effort.
• If there is a close location of groundwater on the site, you need to make a drainage that allows deep and surface water to be drained away from the structure. When there is no danger from groundwater, it is necessary to perform a blind area, at least temporarily.
• To do this, 20-30 centimeters of soil are removed along the perimeter of the foundation, and a plastic film or any other waterproofing material is laid approximately one and a half meters away from the structure at a slope. The film, sprinkled with the excavated soil, will not allow the natural base in the perimeter of the foundation to get wet, and water will not flow to its base.
• If the foundation is strip, such a branch must be made not only along the outer perimeter, but also along the inner. You also need to cover the edge of the tape with film so that the insulation on both sides covers the junction of the soil and the foundation.
• For a slab foundation preserved for the winter, you need to create some kind of gable roof by laying timber in the center and sewing a flooring of boards on them, on which you can lay a film. Such protection is especially important for a slab-grillage foundation, since the sides of a monolithic base prevent precipitation from draining from the slab, and during the winter its concrete bowl will be full of water, which will have to be pumped out.
• It is advisable to also insulate these two foundations: strip and slab around the perimeter. The pile field does not need such measures, since the bases of the piles are always below the freezing level. If there is a grillage, it only needs to be insulated from getting wet - there is no need to insulate it if it does not come into contact with the ground. For temporary thermal protection, you do not need to buy expensive insulation materials, but you can use sawdust or straw bales, which are laid out on top of the protective film layer.

Expert opinion Vitaly Kudryashov builder, aspiring author

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You don’t need to do all this only if you managed to fully waterproof the foundation before conservation.

The presence of permanent waterproofing allows you to do without temporary protection

Time calculations

Let us consider separately how much time it will take for each type of screed. In particular, we will discuss materials such as:

It takes about a week for 4 centimeters to dry, then 15 days are added for each centimeter.

For sand concrete, the drying time is the same. To reduce drying time, use all kinds of additives.

Thanks to them, the time is reduced significantly. For example, thanks to a proprietary screed, a cement floor can be ready within a few hours.

There are several factors that speed up this process:

Thanks to these features, it will take just a few days – 3-7 – for the screed to dry completely.

More information can be found on the manufacturer's packaging.

Strength of concrete

Compressive strength is the main characteristic of each concrete mixture. Due to this parameter, concrete grades differ. The mixture can gain the required strength within 25-30 days, regardless of its brand. This feature forces workers to wait a certain time. During the first week, concrete gains strength more actively than in subsequent days - it is during this period that concrete gains about 60% of the strength indicated in the brand.

Full strength is formed after 28 days of maturation of the mixture. Some workers, to save time, decide to load the structure ahead of time. And as a rule, this leads to a deterioration in the quality of the entire building. That is why, for the reliability of the entire structure, it is necessary to wait the full time. It makes sense to dismantle the formwork only after 7-8 days.

Composition of cement and its hydration

The reaction of converting a dry mixture into a solid mass starts after introducing water into its composition. Clinker minerals, being silicates, actively begin to form spatial bonds. The process is irreversible, since coagulation of particles leads to a complete change in the structure of the material. How long an ordinary cement mortar with sand dries depends on the chemical composition of the dry mixture. The high silicate content speeds up the process.

High-strength grades, such as M 400, M 500, have a small amount of impurities, and the setting time of the cement mortar is faster than when using less durable materials.

The mixture first becomes plastic, which makes it possible to form an element of the required shape from it, and then it hardens, acquiring the necessary strength. It is recommended to use the liquid solution within the period indicated on the package. Typically it ranges from 30 minutes to 4 hours. Then it is possible to restore the plasticity of the hardening solution without loss of quality. At low temperatures, minor adjustments are allowed in the direction of increasing the period. Then the manufacturer guarantees the declared qualities and hardening time of the cement mortar in standard values.

The reaction is called hydration, where the first part of the word means water. The process is unique and differs fundamentally from the setting and hardening of gypsum-based mixtures, where air is needed for a full reaction, which proceeds many times faster and gains the declared qualities in the very first hours. The time required for cement to dry depends only on the brand and ambient temperature with sufficient moisture in the mass.

Solidification stages

Hardening includes two stages.

Solidification stage (for example, foundation)

The period of complete hardening and setting of cement is not that long. One day after pouring is enough for the material to completely harden. However, the main role is still played by the air temperature at which the foundation is poured. After two hours, the concrete hardens after mixing the cement mixture with water at a temperature of twenty degrees Celsius. The end of drying occurs after three hours. Special additives will help reduce the setting by fifteen or twenty minutes.

Hardening period for several grades of concrete:

• Hardening time M 200 = two to two and a half hours.
• Hardening time M 300 = one and a half to two hours.
• Hardening time M 400 = one to two hours.

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Solidification stage

In other words, the hydration stage during the period when the setting of the foundation is active (evaporation of moisture from cement concrete). The hydration process ends prematurely when moisture evaporates too actively, which, in turn, negatively affects the quality and strength of the material. The ideal time interval for the foundation to harden with the required volume of water will be one and a half to two weeks.

The period for complete hardening of some grades of concrete:

• M 200 = fourteen to eighteen days.
• M 400 = seven to fourteen days.

It is important to know that the concrete in the formwork must harden for at least a week before it can be removed without damaging the structure. But do not forget that the drying period depends on the brand of cement. A graph or table will help you figure out how long it will take for concrete to set (taking into account the temperature). The graph and table clearly describe the temperature, brand of material and drying time. A table or graph will become an indispensable assistant in this difficult task.

Drying Features

It is worth determining how long it takes for an expanded clay floor screed to dry. This material is used quite often. The reason is that it is different:

It is developed at high temperatures, and therefore it is quite durable.

The use of expanded clay is relevant in cases where the goal is to raise the floor to a greater height. The peculiarity of this material is that it is capable of moving vapors and air through itself.

It will take about 4 weeks to dry. In some cases, 2 weeks is enough.

Humidity measurement

In order to find out what the moisture content of the finished screed is, there is one simple folk method. It is enough to take a napkin and place it on the “sub-floor”, covering it with tiles for example. A day later, look at her condition. When the napkin remains dry, it is safe to say that you can begin laying the flooring.

There are also special devices that allow such manipulations to measure humidity levels.

They will help you answer the question of how long it takes for a dry screed to dry. Among the equipment, a carbide hygrometer is distinguished. The accuracy of its results is very high. True, there is no point in purchasing it when the screed is being installed in one room. The price doesn't justify the results. In addition, when using it, the integrity of the poured screed is violated.

Among the devices we can highlight an electronic moisture meter. This is where the integrity of the screed remains in place and there is no need to commit any violations to determine the moisture content. True, the accuracy of this device is somewhat less than that of a carbide hygrometer. Before purchasing this or that equipment, you need to think about whether it is worth it. One room definitely doesn’t require this. According to instrument readings, they should not be more than 2 CM-% or 3.4% mass humidity.

conclusions

As you can see, there are certain features that will directly affect how quickly the screed dries. Including pay attention to the moisture level in the room. Also remember about the temperature. Under no circumstances should you neglect the thickness and number of layers in the solution.

After all, this directly affects time. It is also worth remembering about fillers that affect drying. The waterproofing base can have different levels of quality.

At first, you may be confused about how much time is needed to set and how much time is needed to dry. Interestingly, within 24 hours you can start walking on the flooring without leaving marks. After a week it may seem that the surface is very durable. However, this is deceptive.

After all, for example, cement has pores that contain water. It takes enough time to let it come out. Due to the fact that waterproofing has been laid under the bond layer, it is important to allow water to escape to the top. Otherwise, damage may occur - the coating will begin to become damp and deform.

Therefore, even when a week or two has passed, there is no need to rush, because there is enough moisture inside that needs to come out.

If you add a little filler to a solution that takes a long time to dry, you can greatly reduce the drying time.

For this you can use:

This method is called semi-dry screed. After all, in this case there is very little water in it. And it will take about a week for it to dry. But if you need to lay parquet or parquet boards, then you should allow about 3 weeks for drying.

It is also worth first familiarizing yourself with the methods of how to determine what the moisture content of the screed is. There are special devices for this. You can find out about them from specialists. In addition, there are methods that allow you to make such determinations without additional tools.

Taking into account the above points, you can achieve noticeable success in your repair.

If construction companies promise a finished floor in 2-3 weeks, you should think about whether this is an advertising gimmick. It is important to know how long it takes for the screed to dry in order to understand how much time you really need to expect before the completion of the repair and subsequent occupancy.

Rushing in this matter can lead to cracks, subsidence and, ultimately, damage to the coating. And who is interested in experiencing such inconveniences after a major renovation and investing money again?

At the same time, some types of floors can actually be done in the shortest possible time and it is useful to know when delaying construction work is unjustified.

What determines the curing time of the screed?

Do not confuse the setting period of the solution and the stage of its drying. In the first case, you can already walk on the surface without bending it or leaving marks. This often happens quite quickly - from several hours to a week, depending on the type of screed. Hardening involves the complete removal of moisture from the mixture. Only at this stage do they most often begin to lay the covering or install a warm floor.

Drying time depends on:

Traditionally, the technology of use and complete drying time are indicated on the packaging. If not, it is appropriate to use the following recommendations.

The recommended layer height is usually 40-50 mm. Under these conditions, every 10 mm dries in about a week (depending on the material). At the same time, thickening the layer by 2 times doubles the hardening time. Based on this, you can calculate how many days a screed 10 cm thick should dry: the first 50 mm will take a month, multiply by 2 - you get 60 days and add the same amount for the second 50 mm. That's a total of about 17 weeks!

By the way, if you really need such a wide screed, it is possible to reduce its maturation time if you lay it in 2 stages. Thus, it will take half as much time to harden. The use of lighter components, such as gypsum, also significantly speeds up the process.

Considering how long it takes for a 4-5 cm thick cement screed to dry, it is not difficult to calculate that further work can begin no earlier than in a month.

How to speed up the hardening of concrete

The hardening speed varies depending on the brand of cement. Various chemical additives and plasticizers that affect the hardening process of the concrete mixture are of great importance. Temperature is an important factor for mixing concrete. The table above clearly confirms this.

Sometimes craftsmen need to simultaneously arrange joints in prefabricated structures and carry out repair work, in which case the hardening speed is the most important factor. Rapid hardening is ensured due to the growth rate in the initial period. Certain types of concrete can achieve 70% of their full 28-day strength in just 1 to 3 days. Experience shows that structures with quick-hardening concrete are less durable than those in which the material hardens completely.

Table of accelerators and retarders of concrete mixture hardening.

To speed up the process, builders add special mixtures. Here are the rules that must be followed:

• calcium chloride should be about 3% in standard structures, and 2% in reinforced ones;
• cement should not contain more than 2% sulfate, regardless of the type of structure;
• the maximum value for nitrite nitrate, calcium nitrate and sodium is 4%.

Of course, there are also technical methods for reducing curing time. For this purpose, heat treatment by electric heating is used. If the structure is small, then contact heating with thermal formwork will be effective. In temperate or hot climates, the effect of electric heating should last from 3 to 8 hours. After the time has elapsed, the device is disconnected from the network; at the next stage, the structure will be able to independently gain the necessary strength.

Useful tips

In order to correctly carry out the work of laying floor screed under the tiles and not waste building materials, it is necessary to correctly calculate the drying time of the layer and carry out additional actions to speed up the process and minimize the risks of stains and cracks.

Reducing the drying time and failure to comply with the required microclimate will inevitably lead to unusability of not only the screed itself, but also the selected coating. Delaminations, chips, subsidence, and deflections are possible. If the flooring is wooden, noticeable stains may appear that cannot be removed. The desire to quickly cope with repairs can lead to a complete reconstruction of both decorative surfaces and the screed itself, which in itself is labor-intensive and costly.

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GARAGE. Chapter 3 - “Floors - the whole truth is in concrete”

Once the drinking started, as they say...)) Quite a lot has been done, but there is still something left. No, of course, there is still a lot left, in general, I personally realized that a garage is such a thing where you can constantly do something) And yet, there was one more very important, and to some extent the main issue that remained to be resolved - the floors. Whatever decision is made, working with floors seems to me to be an expensive and time-consuming process. Damn, I was just planning to lay roofing felt on the roof! At that time, there was no floor in my garage. Once upon a time, most likely, a solution was thrown haphazardly onto the ground. There were noticeable depressions in places. There was always dirt or dust in the garage ((There is no hole in the garage (apparently due to the presence of the same underground water). This, to some extent, seems to simplify the task.

You could just lay some used linoleum. I monitored the market - there is commercial linoleum on sale, which, according to reviews, is very durable. Price 3000.00 rubles per lin. m. Garage area 24 sq.m. A bit expensive though.

You can make a wooden floor. This option does not inspire confidence.

The use of various tiles such as tiles, ceramics, etc. for the floor is also cut off. Dropped a hammer or something heavier and a crack/chip is very likely. Skolzskie. For installation, the surface must be smooth and durable, i.e. there must be a concrete screed.

After surfing the Internet I discovered a lot of interesting, beautiful and expensive things)

POLYMER LEVEL FLOORS. Beauty! A wide variety of execution options. Very strong, almost durable (which, by the way, is considered both a plus and a minus)), perfectly smooth. I suspect they may turn out to be slippery, but this can also be easily solved by adding special “chips”. Very cool option, I really liked it. Price from RUB 1,500.00 per sq.m. provided the thickness of the applied layer is no more than 150mm if I'm not mistaken. 36-40 thousand rubles. The price of the issue is obtained only according to the most conservative estimates. Of course, such a floor should ideally be applied to a durable concrete screed.

Full size

PVC TILES. Also a great option. Durable, reliable, non-slip. It is possible to play with colors, for example, highlight a space for a car or a work area with a different color. A big plus is that it does not require a perfectly flat surface during installation. Very easy to install. They are joined to each other using T-locks using a mallet. Price from 1100.00 rubles per sq.m. Total approximately 26-30 thousand rubles. But again, ideally, of course, lay it on a concrete base - a concrete screed.

tile laying options

As a result, it turns out that one way or another we need a concrete floor in the garage. It can be left for the first time in its original form, so to speak. It will be possible to paint it, which by the way is a good and budget option. When using special paint, the concrete floor will acquire additional protection, waterproofing, will not accumulate dust, and will also look like polymer floors.

Concrete required. I really didn’t want to make the batches myself. Carrying sand, cement, crushed stone... Lately, so many unplanned things have been done...((It’s definitely not possible to do it yourself. I monitored the companies that stock concrete. On average, 13 thousand rubles per cubic meter. According to estimates, at least 2 cubic meters will be needed. It’s good when there are good ones acquaintances who are engaged in construction, who have a concrete mixer, grade 300 cement, sifted sand, and who are tired of your whining and are ready to organize the delivery of concrete at half the price, literally to pay for fuel and other associated costs, namely 15,000.00 rubles.

With a faithful ally and, most importantly, a dear friend to me, we began to set up the formwork. It was decided not to do the slope. The thickness of the concrete floor was planned to be approximately 7cm. Let's be honest - when setting up the formwork, we of course slightly bent it, and of course we "hand-assed it") Ideally, a strong formwork is made from, for example, iron rods, reinforcement, which are simply fastened together. It should be possible to walk on the formwork, at least so that when the concrete is laid, it will be possible to make reinforcement. We used a laser level to attach ceiling profiles to the back and side walls. They also ran the profile level in the center of the floor. Plus, banal pieces of mesh and iron rods were laid on the floor. The day has come for our concrete to be delivered. A Kamaz truck arrived, they brought the supply chute into the garage, and the supply of concrete began. The three of us worked. The concrete was unloaded almost at the very beginning of the garage, i.e. started throwing and carrying concrete with shovels from the beginning to the end of the garage. After the first 10-15 minutes of work, everyone stood leaning on their shovels and breathing heavily, thinking)))) Really hard work, especially for an unprepared nerd like me. Anyway, about 2.4 cubic meters of good concrete was evenly distributed on the garage floor. Then the leveling and smoothing and everything else began. I admit honestly - if it were possible to return that moment back, I certainly would not have been stingy and hired workers who were more or less experienced in this matter... Not counting the fact that the delivery of concrete itself was exhausting, which was simply terrible, plus taking into account all the tight “hand-cuffing” they laid the concrete of course, unevenly, in places with shoals in the form of waves and other “man-made” small shoals. In the end, even seeing the existing jamb where the thread was closer to the center, I simply didn’t want to go there again to fix the defect on the more or less leveled concrete. Of course, you can’t do that, but God knows - you’re very fucked up)) So the gates were closed, the job was done. The next day, at lunchtime, I was already kneeling on the new hardening floor and rubbing the surface, pouring water on it and sprinkling it with cement. Later I spilled water on the floor again. That's it, let the dear one dry. According to the technology, it seems like it takes 28 days for the concrete to last, after which it can be used. For an ordinary garage, this is of course overkill, but I waited for this period, patiently counting down the days.

How long does it take for cement-based floor screed to dry?

Cement-sand screeds dry much longer than gypsum screeds, but in general, the formula for them is almost the same.
And the calculations are based on the same thickness of 40 mm. So, for a thickness of up to 40 mm, the drying formula is correct: and for a screed thicker than 40 mm, 14-15 days should be added for every additional 10 mm. And for a screed 80 mm thick to dry, it will take not 28 days, but 2-3 months.

When laying very thick layers of screed, experts recommend using special light mixtures. Such a screed will reduce the load on supporting structures and floors, but will take even longer to dry.

Source

How many days later can a car be placed on concrete?

Now, if the concrete has been hardening for 8 days (the area is 15 cm thick of concrete), is it already possible to drive onto it with a passenger car (a la a jeep)? Or let it still stand without load?

as soon as it cracks, you can install it)

I made a stop at the garage, didn’t skimp on cement - I added half a bag of cement to the DSP bag - I stopped by in about 10 hours. It held up with a bang and then withstood the use and frost just as well.

you can drive in if you compacted the cushion before concreting

Yes, everything was compacted. Let's just say - I walked along it carefully on the 2nd day on foot (with my feet) :-)). The neighbor's cat walked on fresh concrete on the day of pouring and left marks :-))

then why are you asking?

So I don’t know how strong it has already become :-)) They’ve already reassured me that it’s possible - thank you. It’s just one thing - I walked on foot (stepped a couple of times), another thing - the whole weight of the car will drive over. This “60% strength” is an ephemeral thing for me, who knows what that means. What load can already be placed on this concrete? In general, I understand - you can stop by carefully :-))

Overview of types of floor subfloors

The general procedure for laying the screed mixture is as follows:

But the solution itself can consist of various materials. Drying technology can be accelerated using gypsum, sand-concrete and semi-dry mixtures. They dry faster than cement. You can use various types of fillers to speed up the drying process. These are expanded clay or polystyrene foam in granules, fiberglass, basalt. They allow you to reduce the amount of water in the solution. This mixture is often called a semi-dry solution.

When installing a floor in a wooden house or any building standing in a low area, waterproofing protection is needed. It is made from roofing felt or from a special vapor-waterproofing film. Coating materials are also used for this purpose. Roofing felt is laid overlapping on the cleaned surface. The edges are lifted onto the wall to a height of 20 cm and secured with a construction stapler. The seams are sealed with bitumen mastic.

When using coating materials, waterproofing is applied in a continuous layer, which extends to the wall. After it dries, the next layer is applied. After complete drying, screeding is performed. Its humidity is checked with special devices. For parquet it should not be higher than 2%, for linoleum - 3%, for carpet - 2.5%.

But you can also use traditional methods in the form of a napkin. A paper napkin is placed on the dried solution and covered with polyethylene. She needs to be checked in a day. If it remains dry, the screed is dry. If moisture appears in the napkin, you need to give the solution another week to dry. In this case, the minimum layer thickness should be about 4 cm.

The gypsum-based screed solution sets quickly. This takes 4 hours. But you can lay parquet or laminate flooring, as well as carpet and linoleum only after a week. The floor can be covered with tiles after 4 days. These calculations are correct for a layer up to 4 cm thick.

Wet cement mixtures

Most often during construction there are cases of using wet screed. A cement-based solution is mixed with the addition of sand and fillers. It is applied in several layers to the base. The concrete screed takes a long time to dry, but after complete hardening, which may take several months, the quality of the screed is distinguished by its strength and reliability. If you tap it with a hammer, it should produce subtle sounds in response.

There are cases when the solution is made only on the basis of cement. In this case, the cement screed takes a long time to dry. It is better to use a solution with added sand. It's somewhere between concrete and cement. When laying, the solution must be constantly compacted so that there are no air bubbles left in it. A 5 cm thick layer of this solution takes about 30 days to dry. But you can purchase a ready-made dry mixture, which is diluted with water before use. This sand concrete mixture dries faster than a homemade composition.

The dried composition is suitable for laying the final floor covering. It fits well on parquet and laminate, linoleum and carpet. Sometimes a quick-drying self-leveling mixture is laid on the screed. It is better to do this when the solution is completely dry. It is not necessary to wait until the tiles are completely dry to lay the tiles. It is enough to wait until the moment when walking on the solution leaves no traces. Floor tiles fit well on this floor.

Semi-dry

If you decide to use a semi-dry mixture, it is important to remember its drying time. This takes approximately 2 weeks. In winter, the timing increases. A semi-dry screed, laid in a layer up to 50 mm thick, takes 15 days to dry. It takes 21 days to dry 7cm. 10 cm to the finishing stage is reached in 28 days. You can walk on the screed 12 hours after laying the mortar. For proper drying, you need to ensure the ambient temperature is within 22...25˚C and the humidity is not higher than 65%.

The work is carried out according to plan:

How long does it take for self-leveling floors to dry?

Drying time of the self-leveling floor or when the floor covering can be laid On the packaging of self-leveling

mixtures for rough work.

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