Concrete hardening time m200 in autumn: how long does it take for a concrete foundation to harden

October 31, 2016 Stroyexpert Home page » Foundation » Formwork

To organize and carry out construction, it is important for craftsmen to know exactly how long it takes concrete to dry in the formwork. This indicator largely determines the construction time, future reliability, and strength of the structure. Specialists involved in the development of a concrete mixture must conduct a series of studies and examinations to determine the exact period of time required for the material to gain strength.

Impact factors

To help the cement dry out and avoid various troubles, there are several factors that should be observed:

• protect concrete from direct exposure to sunlight;
• if cement suddenly loses moisture, cracks may form; to avoid this, concrete must be moistened periodically;
• in the event of an unexpected cold snap, the poured concrete needs to be heated, this can be done using special heaters, steam, electricity, etc.;
• special salt-free and salt preparations, sold in construction stores, affect the drying time of cement - they significantly reduce it;
• More expensive brands of concrete harden faster than cheaper ones.

Sometimes it happens that the drying process needs to be slowed down, if, for example, it has already been prepared, but has not been delivered to the construction site. In this case, special surfactants are used.

In this aspect, seasonality, the composition of the solution, the presence of auxiliary additives, and the level of strength of the material are important.

If pouring is done outdoors and the air temperature does not exceed 5°C, the concrete will take 2 times longer to gain strength than at 20°C. If the thermometer drops below zero, the mixture will thicken due to the freezing of water, but will not be able to achieve the desired level of integrity. Also, the hardening time depends on the proportions in which water, gravel or crushed stone filler, cement, and sand were used.

Technological additives are used in cases where it is planned to subject the mixture to long-term transportation: under such conditions, a significant slowdown in the thickening process of the solution is expected. They are also relevant if it is necessary to speed up construction work and achieve faster drying without loss of quality and load-bearing capacity.

Factors related to the strength of concrete certainly affect the speed of formation of structures made from it:

• cement and water used in certain proportions affect the rate of chemical reaction. If there is too much liquid, pores will appear profusely, which will negatively affect the quality of the product;
• The larger the filler present in the mass, the stronger it becomes when dried.

How long concrete dries depends on the coolness of the filler. Over time and as it dries, the strength characteristics of the product increase; stopping this progress is caused by a drop in temperature below zero.
To find out how long concrete takes to dry, it is necessary to take into account a number of conditions that affect the rate of concrete hardening.

Seasonality

The key factors that determine how long concrete hardens are the environment and the period of the year when construction work is carried out. This group includes indicators of outdoor temperature and air humidity.

If in summer the composition can harden in a few days, then in the cold period hardening will take more than a month. The specifics of strength gain under favorable concrete hardening conditions are as follows:

1. 1-3 days - no more than 30% brand strength.
2. 7-14 — 60-80%.
3. 28 — 100%.

If you want to make the foundation mortar quick-hardening, you need to add special additives to its composition.

Tamping

A dense screed does not tolerate cutting and drilling after compaction, so for such work it is necessary to use diamond drills. A simple tip will quickly fail.

Compound

How long the concrete hardening process can take depends on its composition. So, if it contains a large amount of porous additives, such as slag and expanded clay, water will linger in the solution for a long time. If the mixture contains sand or gravel, the liquid will come out faster.

We suggest you familiarize yourself with How to attach a cable duct to a concrete wall

To reduce the intensity of moisture evaporation and increase the strength characteristics of the composition, it is diluted with additional components. It can be bentonite or a soap composition. The introduction of such additives increases the overall cost of the work, but prevents the problem of early drying out of the solution.

Optimal drying conditions

The quality and service life of the screed depend on the conditions under which the screed dries.

It is necessary to ensure constant microclimate conditions in the room:

Lower temperatures and higher humidity levels result in longer drying times. In winter, it is not advisable to carry out the screed installation procedure; the minimum temperature at which work can be done is +5 degrees. An uncured screed should not freeze. Central heating radiators should be turned off: they dry out the air.

The screed in the bathroom requires special attention. As a rule, these rooms in modern block multi-storey buildings have good ventilation. To prevent cracks in the freshly laid composition, you need to create a moist environment.

Sand or sawdust should be poured onto the surface in an even layer, then watered over the next 10 days. Surfaces also need to be moistened in other rooms if the weather is hot outside. To do this, you need to spray water regularly.

Dependence of foundation holding time on its type

Insinuations that the finished foundation, after the concrete components included in it have reached the normalized strength, should stand for a year or winter are absolutely unfounded. A common misconception about the need to withstand the structure until the end of the ongoing sedimentation-shrinkage processes arose as a result of the substitution of concepts. A fully erected building must be conditioned before finishing finishing begins. This is explained simply by the example of existing varieties of structural foundations.

Video on how to speed up concrete hardening

Columnar foundations

A columnar foundation is a series of individual pillars, for the construction of which brick or stone masonry is used; often the foundation pillars are made of concrete or reinforced concrete. To give the foundation elements additional stability, a grillage is installed - a reinforced concrete strip connecting the head of the pillars.

This type of foundation is classified as a light variety, therefore, the foundation base, not loaded with the weight of the building, is subject to increased mobility during soil movements with heterogeneous morphology, and can be easily deformed as a result of frost heaving. By definition, the foundation of a columnar structure cannot stand, and the construction of walls must begin immediately after the masonry mortar has set or the concrete has gained strength.

Strip foundations

Strip reinforced concrete foundations can be constructed in two types:

• shallow foundations are equipped for the construction of light buildings and their soles rest on soil horizons located above the freezing level;
• deeply buried options involve the construction of voluminous structures with a large weight on them; the level of their base exceeds the depth of soil freezing.

A shallow strip foundation experiences loads that are similar in tension and strength to the impact on columnar versions with a grillage. If such a foundation is allowed to stand for a period when active soil heaving occurs under the influence of freezing and thawing of ground moisture, the possibility of its deformation is very likely.

Deep strip foundations rest their base on dense horizons and are not affected by ground shifts. Shrinkage processes in the concrete mass are completely completed after reaching the standard strength, and the settlement of the structure under the influence of its own mass, without taking into account the weight of the building, is completely leveled by expansion joints.

Slab varieties

Monolithic foundations are simply calculated and arranged; they provide a foundation for the building under construction with sufficient strength characteristics. The uniform distribution of the load on the soil base due to the large supporting surface determines the minimum value of the specific pressure on the soil. A properly prepared sand or sand-crushed stone cushion under the foundation slab can prevent its significant sedimentary movements.

The stability of the building being built on a slab foundation directly depends on how carefully the preliminary excavation work was carried out. The amount of time a monolithic foundation must stand is determined, again, only by the period necessary for the concrete to gain strength.

Pile foundations

The foundations of buildings on piles, with any technology of their arrangement, ensure the transfer of load to deep, often bedrock, horizons of soils and rocks. This type of foundation construction completely eliminates the possibility of building deformation, regardless of how much time is allocated for them to stand after installation is completed.

Determining the time for how long the foundation should stand after pouring should be correlated with the time period during which ready-mixed concrete will gain the strength standardized by SP 70.13330.2012. Additional curing is not advisable, and in cases of using columnar structures and shallow strip foundations, it is even contraindicated.

Recommendations for caring for the blind area

Filling the blind area correctly is only part of the work with which you are already very familiar. The thing is that such a structure is constantly exposed to various external factors, and if you do not eliminate small cracks and other defects in a timely manner, then in the near future you will need to build a new blind area.

Small cracks can be opened and then repaired using cement mortar. As a rule, one of the most problematic areas of such a structure is the junction with the foundation or plinth of the building, because about half of all troubles are associated with this zone.

In case of relatively small cracks, waterproofing sealants or foam fillers can be used. If the gap is large, it can be cleaned of soil, debris and sand, and then filled with concrete.

Once you're done sealing cracks and seams, there are a number of important preventive measures you need to take to help prevent these situations from happening again in the future. To prevent the structure from moving away over time, it is necessary to dig a ditch about 30 cm deep on the opposite side and fill it with concrete.

Concrete is called an artificial stone with properties that manifest themselves after reaching the strength declared by the manufacturer. During setting and hardening, strong bonds arise in the solution, providing the strength characteristics of the composition. Working with concrete requires accurately calculating the period of setting and hardening of the solution. A durable structure is a matter of respecting the drying time of the mixture, and minimizing the destruction of the structure depends on this. When calculating how long concrete should dry, you should remember that during the process not only the evaporation of water from the solution occurs, but also the chemical hardening of the mixture of components.

Pressure strength test

Design requirements

The concrete blind area has a fairly simple design, the preparation of which will require the following materials:

1. Bedding (pillow). This is done before pouring the solution. A variety of materials are used as backfill: coarse or medium sand, sand-gravel mixture, crushed stone, fine gravel. The foundation area cannot be laid on fine sand due to the possibility of shrinkage, since in this case there is a risk that the base will crack. It is best to prepare a two-layer cushion: first lay gravel or crushed stone, which will compact the soil, and then sand.
2. Reinforcement. The presence of reinforcing mesh for a concrete blind area will give the structure more strength. The cell size of this product is usually 30 x 30 or 50 x 50 cm. The mesh diameter should be about 6-8 mm, but it all depends on the type of soil.
3. Formwork. Wooden guides located along the perimeter of the coating are required, as they will prevent the concrete mixture from spreading. The width of the formwork boards is usually 20-25 mm.
4. Concrete solution. The blind area is poured using a specific concrete mixture composition.

Concrete classes, depending on the strength of the composition
. To obtain a high-quality coating, it is most profitable to make a concrete mixture on your own.

To fill the blind area of ​​a house with concrete, you need to familiarize yourself with the regulations and recommendations of SNiP:

• The width of the blind area should be 20 cm greater than the roof overhang (SNiP 2.02.01-83). If the structure has a drainage system, then its indicators are also taken into account. The optimal value is 1 meter. In this case, you can lay a tile path around the house.
• The length of the blind area around the house, made with your own hands, must correspond to the perimeter of the building. However, if you plan to install a concrete porch, then a “break” is allowed.
• Depth. The depth of the “tape” is half the calculated freezing depth of the ground.
• The thickness of the concrete blind area is also regulated by SNiP and, according to these requirements, should be at least 7-10 cm for the top layer. However, many people make concrete parking spaces for personal cars along with the blind area. In this case, the operational load increases, and the thickness of the concrete blind area can reach up to 15 cm.

The blind area must be built at a slope of 2-3 degrees

• Slope. According to SNiP III-10-75, the slope should be from 1 to 10 cm for each meter of width. Most often it is 2-3 cm per meter - this is approximately 2-3 degrees. The angle of inclination must be directed in the direction opposite to the foundation. It is not recommended to increase the slope, since in this case it will be difficult to walk along such a path in winter, when ice forms on the surface.
• Border. The installation of a blind area for a house does not include the mandatory production of a border, so in this case the decision is made by the owners of country property. However, experts recommend installing such “limiters” if trees and shrubs with an “aggressive” root system (blackberries, raspberries, plane trees, poplars and others) grow near the foundation.
• Base height. For a hard type covering (concrete), the base must be at least 50 cm.
• The recommended height of the blind area above ground level is 5 cm or more.

There are also several schemes according to which a blind area can be built from crushed stone, in the form of a monolithic concrete covering, both for normal soil types and for “problematic” ones.

Types of blind area, based on soil characteristics

Knowing the requirements of SNiP and the features of a suburban area, you can make a blind area with your own hands using the step-by-step instructions given below.

Pouring a blind area: basic rules

Scheme of the blind area with dimensions.

To properly fill the blind area, remember a few important recommendations. First of all, under no circumstances should you make a blind area of ​​a monolithic structure. Even if the entire process of insulating the structure was carried out according to all the rules, under the influence of temperature changes the soil under it may swell. After some time, this will lead to the formation of cracks on the blind area. To avoid such an unpleasant situation, at the junction of the structure with the surface of the foundation it is necessary to make a horizontal damper or expansion joint, 10-20 mm wide. It is made from polyurethane sealant or from a special damper tape. Ordinary 10-20 mm boards can be used as material for transverse seams. They need to be coated with bitumen and placed on edge. If you are building a foundation, the waterproofing layer must be removed all the way to the blind area.

Some developers who decide to fill the blind area themselves forget that it needs to be reinforced.

Before you start pouring concrete, you need to lay a reinforcement frame made of rods connected with wire, or a special metal mesh with 10x10 cm cells, into the trench.

The metal frame is laid in sections, which were obtained after creating the transverse seams, at an equal distance from the edges of the future structure. In addition, this frame should be raised above the pillow, for which you can use fragments of bricks and other available means.

After the pouring is completed, while the concrete solution has not yet hardened, it must be ironed, i.e. Sprinkle with dry cement in a layer of 3-5 mm and rub in using a trowel. This will make the structure more resistant to moisture and generally durable.

To prevent the concrete from drying out too quickly, it is necessary to cover the blind area with damp rags, which must be periodically soaked in water again. Gradual drying of the concrete will make the blind area more durable.

Return to contents

Impact factors

Before starting construction work, it is necessary to take into account all factors that could in one way or another influence the drying time of concrete.

Seasonality

Of course, the environment has the main influence on the drying process of cement mortar. Depending on the temperature and atmospheric humidity, the period for setting and complete drying may be limited to a couple of days in the summer (but the strength will be low) or the structure will retain a large amount of water for more than 30 days during the cold season.

The strengthening of concrete under normal temperature conditions can be better explained by a special table that indicates how long it will take to achieve the maximum effect.

Tamping

Much also depends on the density of the construction mixture. Naturally, the higher it is, the slower the moisture leaves the structure and the better the cement hydration indicators will be. In industrial construction, this problem is solved with the help of vibration treatment, but at home they usually get by with bayoneting.

It is worth remembering that a dense screed is more difficult to cut and drill after compaction. In such cases, diamond-coated drills are used. Drills with a regular tip instantly fail.

Compound

The presence of various components in the building mixture also affects the setting process. The more porous materials (expanded clay, slag) in the solution, the slower the dehydration of the structure will occur. In the case of sand or gravel, on the contrary, the liquid will come out of solution faster.

To slow down the evaporation of moisture from concrete (especially in high temperature conditions) and improve its strength, they resort to the use of special additives (concrete, soap composition). This will somewhat affect the cost of the filling mixture, but will prevent premature drying.

Why you can't speed up drying

Setting, allowing movement along the screed, occurs on the first or third day after its installation.
The customer often wants to reduce the hardening time, but this is strictly prohibited. If the upper layers dry too quickly, then moisture may remain in the lower ones. It will be sealed from below with waterproofing, and from above with a dense dried crust. Over time, water can not only tear apart the leveling layer, but also lead to mold.

How long does it take to build a strip foundation for a house?

Why do you need to calculate the drying time of concrete when constructing the foundation supports of a residential building? It's simple - if work began at the end of summer, this process (gaining the strength of the support tape) may shift to mid-autumn, which will affect the rate of drying of the structure in the formwork.

Typically, the mixture in the formwork dries in 28 days in the summer, gaining the required strength at an average temperature of 20 C, humidity within 68%. With a decrease in temperature in the autumn, the drying time of concrete in the foundation belt of a house increases from 1.5 to 2 months.

Therefore, for winter work with concrete, special recipes have been developed for the preparation of compositions for pouring building structures. In extreme cold, it may be necessary to install special formwork (warm), otherwise the solution not only will not begin to gain the necessary strength, but will not even set.

The process of drying the mixture in formwork

The initial stage of concrete drying is setting

When filling the foundation formwork for a house with a concrete composition (take a belt belt as an example), two stages of hardening are distinguished:

Setting - the concrete mixture quickly loses its mobility and plasticity, which is why when pouring house structures, it is recommended to carry out all laying work very quickly, avoiding the formation of dried layers in the formwork, in order to avoid the formation of “cold bridges” inside the structure.

Transportation of concrete to the laying site is carried out with constant mixing of the mixture. All technological operations for laying the mixture into the formwork (surface leveling, compaction) should be performed without downtime or accidental interruptions. “Cold bridges” that appear when the layers of the laid mixture dry out can affect the strength and durability of the support of the house.

Properly prepared concrete mix dries in a standard time

But the hardening time of concrete in the foundation depends not only on weather conditions. The quality of the cement binder from which the solution is mixed has a great influence on the hardening time of the mixture.

The ratio of water to cement when mixing the mortar is of no small importance.

It is very important to follow the recommended proportions if the concrete mixture for pouring the foundation of a house is prepared directly at the construction site with your own hands. It is worth noting that the drying time of monolith foundations depends on the composition of the soil at the construction site, because hardening of the mixture during concreting is a chemical process that occurs depending on the combination of components

It is worth noting that the drying time of monolith foundations depends on the composition of the soil at the construction site, because hardening of the mixture during concreting is a chemical process that occurs depending on the combination of components.

How to correctly calculate the drying time of the composition

Whether a monolithic strip foundation is used for a house or a bathhouse, the concrete mixture on average reaches complete hardening in 28 days, but the strength gain does not stop there

For a long time, the foundation will continue to gain strength, so it is very important to follow the technology for laying the concrete mixture into the formwork and caring for it

The drying process of concrete must be carefully controlled, taking all measures to ensure that it is not disrupted ahead of time. The mixture laid in the formwork must be carefully looked after - moisturize the surface of the structure, and protect the surface of the foundation from sunlight.

Watch the video with expert commentary on how to properly care for your poured foundation.

Concreting a blind area with your own hands: step-by-step instructions

Prepare the following tools:

• construction bucket;
• drill;
• mixer attachment;
• putty knife;
• mallet;
• building level;
• a rag.

The work begins with preparing a trench, which must be made along the entire length of the foundation. The blind area must be at least 60 cm long if it is built on normal soil, and at least 1 m if it is built on subsiding soil.

Next, you need to install the underlying layer. Clay is used for this. The clay cushion should have a thickness of 10-15 cm. If the construction is carried out on heaving soil, then a sand layer about 6-8 cm thick is poured on top of the clay, which will ensure complete cushioning of heaving forces. In this case, all layers must be thoroughly compacted.

The last step is to lay crushed stone or gravel. In this case, this building material will serve as a drainage system. This is necessary in case water flows under the blind area if poured incorrectly.

In order to increase strength, the future blind area must be reinforced. To do this, you can use a grid with cells of 10x10 or 15x15 cm.

The final stage of work is pouring the concrete solution. The concrete layer must be at least 100 mm thick. This is the most important and responsible moment.

The reinforcing mesh is laid with an overlap of 11 cm, which will prevent movement when pouring the concrete solution. The solution is poured in a layer 12-16 cm thick directly onto the previously prepared pillow. To create expansion joints, wooden boards carefully treated with an antiseptic are used, which are laid edgewise across the concrete surface. If there is no access to a concrete mixer at the construction site, you can prepare a concrete mix solution for the top layer of the structure yourself. The finished solution must be poured in parts. You can start the next portion only after the previous part has gained hardness. To prevent the coating from cracking under the sun, it should be covered with plastic wrap for 3-4 days. The concrete will finally gain strength after a month. After this period, the formwork boards can be removed and you can walk freely on the blind area.

Concrete hardening time

The vast majority of amateur builders believe, for reasons that are not entirely clear, that the concreting process is completed once the laying of the formwork is completed or the work on leveling the screed is completed. Meanwhile, the setting time of concrete is much longer than the time for laying it. A concrete mixture is a living organism in which, upon completion of laying work, complex and time-consuming physical and chemical processes occur, associated with the transformation of the solution into a reliable basis for building structures.

Before stripping and enjoying the results of the efforts, you need to create the most comfortable conditions for the maturation and optimal hydration of concrete, without which it is impossible to achieve the required brand strength of the monolith. Building codes and regulations contain verified data, which are given in concrete setting time tables.

The data contained in the official tables, of course, should serve as a guide for the independent arrangement of concrete or reinforced concrete structures. But the use of such data should occur in close practical connection with real construction conditions.

Grasping: chemistry and physics

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.

Several factors regarding concrete

To answer this question, we should return again to the correct use of concrete itself.

When concrete is just poured, it is necessary to leave a small distance (about 0.5 m), which is filled with sand - this is what will prevent excess liquid from accumulating and destroying the concrete structure. Plus, in winter, when water turns into ice, the moisture remaining inside the foundation can simply destroy or severely deform the entire structure when it expands. When we are not talking about the construction of a country house or a bathhouse - but about important military-industrial facilities, then the concrete is given an extremely long period of time, during which it must fully gain strength and density

This applies to various bridges, dams, embankments, breakwaters, dams - all of this requires an extremely massive foundation, and rushing in the construction of such objects is simply unacceptable due to their importance. Concrete continues to gain strength even after it has completely hardened and dried - indeed, even after construction work has resumed. Of course, this process proceeds much slower than usual and is no longer taken into account in construction.

However, this provides additional reliability when it comes to reinforced concrete or simply concrete structures. As in many other cases, temperature serves by all accounts as a reliable catalyst for the reactions that take place - that is, at elevated temperatures the reaction proceeds much faster. But under no circumstances should you abuse this knowledge; during the time it takes for the foundation of the house to dry, water and concrete have time to react successfully. When heated, the water simply evaporates - and the mixture dries out, but, nevertheless, does not harden, and the bearing capacity of the entire foundation is strongly questioned. Therefore, you need to let the chemical reaction take its course, without trying to interfere with this natural and entirely natural course of events.

Reaction time

In general, how long it takes concrete to set is clear from the previous table. After 6 hours, its mass ceases to be mobile; after a day it loses its plasticity, but remains fragile. The material gains full grade strength in about a month.

Reference: grade strength corresponds to the maximum compressive force that concrete can withstand without destruction. Force is measured in kilograms per square centimeter. Thus, concrete grade M200 must withstand 200 kgf/cm2, M300 - 300 kgf/cm2, M400 - 400 kgf/cm2, and so on.

However, the above table is correct for so-called normal conditions: +18-22C with a relative humidity of about 60%. What happens if there are deviations in one direction or another?

Strength development at different temperatures.

How to level out deviations from the normal regime?

• In hot and dry weather, the structure in the formwork is covered with wet burlap, wet sawdust, or watered with water two to three times a day.

Watering the slab foundation.

• At temperatures down to -5 C, it is enough to cover and, if possible, insulate the young concrete. The heat generated during hydration will prevent the water from freezing.
• At lower temperatures it requires heating. An alternative is to use winter grades of concrete that, thanks to special additives, can set at subzero temperatures.

Useful: thanks to antifreeze additives, the price per cubic meter increases by only 100-300 rubles per cubic meter. Actually, it is not difficult to prepare winter concrete with your own hands: the instructions boil down to adding special anti-freeze additives (for example, Antifreeze DS) to it in an amount of 1% by weight of cement.

How do you know when the screed is ready?

The screed is the base for the floor. Depending on the different type, it dries in about 27-28 days. After this, they begin laying the flooring. Since the allotted drying time does not always coincide with that specified by the manufacturer, you need to make sure that it is ready. This question is especially relevant if a concrete screed is made in an apartment when the heating season has not yet begun.

If you lay a moisture-proof floor covering on top of a wet base, the remaining moisture will create conditions for the development of fungus and mold. Concrete under its influence will begin to collapse, and thermal insulation will be damaged. In the future, the finishing floor covering will also suffer.

To determine the readiness of the screed, you can use two methods:

• A visual inspection may provide the answer. The screed must be uniform, with uniform color and structure over the entire surface. There should be no cracks on it.
• You can use large size plastic film and attach it to the tie using adhesive tape. After a day, the film must be removed and inspected. If there are no signs of fogging on it, you can continue working on laying the flooring.

What determines the drying speed of a floor screed?

In order for drying to occur as correctly as possible, and for the resulting strength to correspond to that declared by the manufacturer, it is necessary to create ideal conditions for drying. The parameters are usually indicated on the packaging.

Air humidity

It would seem that in order for something to dry faster, you need to place it in dry conditions. This has nothing to do with the screed. If you artificially speed up the drying process, there is a risk of getting a leveling layer with cracks.

Optimal humidity conditions are 60-70%.

If the values ​​are below normal, it is necessary to protect the floor screed from drying out too quickly. To do this, after setting, the composition is covered with plastic film for 7-10 days. Later, they are kept for another 2-3 weeks under sawdust or sand, which is constantly moistened. Further, until complete hardening, protective coatings are not used, but in very dry conditions, spraying the leveling layer is allowed.

Thickness

The key factor influencing the rate of hardening of the screed is its thickness.
This indicator is different for different types of mixtures. The standard calculation value is the drying rate of each centimeter of screed with a total leveling thickness of 40 mm. If the base has many significant defects (chips, deviations from the level and protrusions that cannot be eliminated), a thicker leveling layer may be required. In this situation, every centimeter of excess of the standard thickness requires more drying time.

Hardening time of concrete in formwork

Formwork is a special structure designed for creating various monolithic concrete products, including foundations. During construction, wooden or metal formwork can be used.

Formwork for concrete foundation

When creating the foundation of houses, collapsible wooden formwork is most often used.

After pouring concrete and initial setting, the formwork is not dismantled for at least a week. In rare cases, the formwork remains in place for most of the concrete hardening time. After 7-10 days, the formwork is usually dismantled. Dismantling is carried out in such a way as not to damage the integrity of the structure. If the structure was installed taking into account all the rules and regulations, then there will be no problems with dismantling.

Before assembling the formwork, it is necessary to carry out preparatory work, including digging a trench (if you plan to create a strip foundation). The mixture is prepared immediately before pouring, when the formwork has already been assembled.

How long does it take for a concrete foundation to set and dry?

The strength of concrete increases daily according to the following scheme:

• primary setting (the process begins in 10-20 minutes and is completed within 24 hours);
• hardening (this stage takes about 1 month).

At temperatures above 20 degrees, the strength of the foundation on day 3 is about 50%.

Leveling is carried out while the mixture is still liquid. Builders act quickly, as signs of setting become noticeable within the first hour after pouring.

Strength gain

The structural strength of a floor or any other structure and the time it takes for the cement mortar to harden are directly related. If the water leaves the concrete faster than necessary for setting and the cement does not have time to react, then after a certain period after drying we will encounter loose segments, leading to cracks and deformation of the screed.

These defects can be observed when cutting concrete products with a grinder, when the heterogeneous structure of the slab indicates a violation of the technological process.

According to technological rules, the concrete foundation dries for at least 25 - 28 days. However, for structures that do not perform increased load-bearing functions, this period is allowed to be reduced to five days, after which they can be walked on without fear.

How long does it take for concrete to harden?

In our time, concrete has become the main material for construction. Most often it is used for the construction of residential buildings and industrial facilities, because it is the most affordable and practical. However, when you begin “collaboration” with this material, the hardening time of concrete is a more pressing issue than ever.

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.

Solidification stage (for example, foundation)

Concrete strength table.

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.

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.

Seasonality of work

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.

How long does it take to harden at thirty degrees Celsius? Naturally, due to high temperatures, the cement mixture sets faster, but this can negatively affect its strength. Intense evaporation of moisture from concrete causes hydration to stop and also reduces durability

Basically, at 30 degrees Celsius, cement concrete will harden an hour after it is poured. In hot weather, when the air temperature reaches 30-40 degrees Celsius, builders use special retardant additives. They are necessary to ensure that the mixture dries evenly. Retarders allow the material to reach its highest point of strength.

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.

How long does it take for a floor screed to dry - is it possible to artificially speed up the process?

The subfloor must be durable and meet the quality declared by the manufacturer. To do this, you must strictly follow some rules for laying and preparing the mixture. Usually all recommendations and proportions are given in the instructions and written on the packaging.

The process is not quick, since the screed must dry completely. This may take 10-15 days or 3-4 months. It all depends on the thickness of the layer, the solution used and other factors.

To speed up drying, some unscrupulous specialists resort to various “tricks”:

This cannot be done! Such methods are fraught with irreversible consequences, since all the work will have to be done again. Such a coating will not have strength, and the floor itself will become covered with cracks.

Permitted methods of acceleration include:

Why is it necessary to dry the solution layer completely?

The base must be completely dried to remove any water. Otherwise, moisture will begin to rise and ruin the finish. Regardless of what kind of covering is used (laminate, tiles, parquet flooring, linoleum, etc.), it will have to be removed if the screed is not dried. It is clear that condensation will not destroy the tile or linoleum itself, but it will damage the glue that holds the finishing material in place.

According to the repair technology, before pouring sand concrete, waterproofing material is laid so that the floor is warm. And since the moisture will have nowhere to go, it will soak it, and eventually the top layer will peel off.

The screed must be dry before carrying out the final work.

Concept, types, properties

It is called building alabaster or gypsum, consisting of a dry mixture of components. Gypsum is considered the main substance among them. The elasticity of alabaster and its adhesion are ensured by polymer components. This material is classified as non-flammable, environmentally friendly natural materials. It has excellent soundproofing properties and water resistance.

Advantages and disadvantages

Before you start working with a mixture prepared from alabaster powder, you should study the characteristics of the material used. The powder is inexpensive and is in deserved demand among buyers for its excellent technological performance. In general, building alabaster has the following properties:

• dries quickly upon contact with water (sets in 5 minutes, completely hardens in 30 minutes), which makes the material indispensable when quick and high-quality surface finishing is needed;
• preventing the appearance of cracks;
• an even film is formed on the treated surface;
• good fire-resistant properties (difficult to ignite);
• high sound insulation.

This finishing material is light in weight and does not shrink during the hardening process. If the question arises as to whether alabaster is harmful to human health, then we can absolutely say that it is safe. The powder is predominantly white in color, but it also occurs in other colors: light gray, yellow, and sometimes it has greenish and pink shades.

What temperature can alabaster withstand? It can withstand exposure to significant temperatures. Resists heat up to 700° without destruction. The destructive consequences of interaction with open fire will be visible after 6 hours.

Negative characteristics of the material include its insufficient strength and inability to withstand heavy loads. Due to the fact that alabaster can absorb water when hardening, it should not be used in particularly damp rooms. The frozen alabaster mixture does not like it when the air around is dry and hot, then the material will simply crumble due to loss of moisture reserves and a decrease in viscosity. Such disadvantages are eliminated by introducing various additives into the alabaster solution.

Features of the material

When working, you must remember the features inherent in this substance. In addition to the rapid hardening characteristic of it, it is capable of increasing in volume. A distinctive feature of this material is also that it does not stick to the surface of rubber products. It is even recommended to prepare a solution from it in a regular rubber ball. The material is stored in a dry place with humidity not exceeding 60%.

Types of alabaster

Currently, according to the speed of hardening, the material is divided into the following types:

• with rapid hardening;
• with normal hardening speed;
• with slow hardening.

In the first case, the mixture used will begin to set a few minutes after its preparation, and after a quarter of an hour it will completely harden. The solution of the second type will begin to harden after preparation after 7 minutes, and will finally harden in 35 minutes. For the latter type of mixture, hardening begins after 20 minutes. from the moment of preparation, and the solution will finally harden after 40 minutes.

Controlling the consistency of the concrete mixture

Control is important. It determines how well the solution was made, what materials were used, in what quantities, how much water was used so that there is no delamination in the future. There is a fairly familiar situation in construction when the first mixtures turn out to be either too rigid or mobile. Based on the sediment of the cone, they determine how well the consistency is made and what percentage of moisture is present. This method helps to understand whether there were errors in the dosage of materials.

Concrete delamination is a phenomenon that occurs quite often in the repair and construction industry due to uneven loads. It can be determined both by external defects and by hearing. But the second method is good for small areas.

To do this, use a hammer to gently tap the poured surface. When a dull sound is heard, this indicates that peeling has occurred. If you notice that during the inspection the peeled area occupies more than a third of the filled area, you should dismantle it and refill it.

On larger areas, delamination can already be noticed by errors in the manufacture and installation of the mortar. When the concrete mixture delaminates, it is necessary to correct the situation immediately in order to save money and avoid rework later.