Concrete is widely used in construction due to its operational characteristics: it is hard, wear-resistant and durable. To obtain these qualities, structures must be cast using a special technology. If the rules for laying the solution are violated, the element will not acquire the expected characteristics. How to use concrete correctly, how long does this material dry and what does this parameter depend on?
Material Composition
Any concrete mortar consists of a mixture of sand, cement and water. Depending on the type of solution, various fillers are added to the main components:
- Crushed stone, gravel.
- Expanded clay.
- Slag.
- Polystyrene.
- Wood chips or sawdust.
The solidification time of the mass depends on the type of binder from which the concrete is made. How long the mixture dries is determined by laboratory tests, then the period obtained as a result of the test is used in practice in the construction of facilities.
Varieties of binders
How long the concrete dries depends on the characteristics of the main component. There are several typesbinders that make up the basis of the solution:
- Cement mixes. Solutions are prepared from them for the manufacture of load-bearing and critical structures. The mixture hardening time to working condition is from 7 to 14 days.
- Gypsum. Concrete based on this binder is used for the construction of less critical parts of the building, for example, interior partitions and self-supporting walls. The composition of the solution includes a mixture of pozzolanic cement and powdered gypsum. The design becomes operational after 2 days.
- Silicates significantly reduce the cost of concrete, while the strength characteristics remain at a high level. The term for reaching the working state of the material depends on the proportions of the mass and the method of hardening. Autoclaved reactions take up to 2 days.
- Polymer-cement binder is used for mixing decorative mortars with the inclusion of marble, granite chips, natural and artificial pigments. The solution hardens in an hour, it is possible to subject the surface to a load in 3-4 days.
Determining Factors
In addition to the established average hardening time of the concrete mix, the hardening time is affected by:
- Humidity. The hardening process is a chemical reaction between the binder and water. Accordingly, as soon as the liquid runs out in the body of the structure, this action will stop. To avoid dehydration and cracking of the concrete volume, it is necessary to create a condition of sufficient humidity of at least 75%.
- Ambient temperatureenvironment. Since water is involved in the reaction, it must be prevented from freezing during the cold season. During the hardening process, heat is released from the structure; at elevated temperatures, the interaction of the components occurs much faster.
- The type of binder and the amount of water in the mortar also determine how long the concrete has to dry. Gypsum powder, with a sufficient amount of liquid, acquires a solid structure after a couple of hours, Portland cement needs about 12-16, depending on the listed conditions.
- The thickness of the structure affects the overall hardening of the mortar.
These factors must be taken into account when designing construction works in which concrete is used. How long the construction dries depends on the environment and proper care of the laid volume.
Average terms
Most often, classic cement concrete is used for the construction of critical structures. How long the structure dries out of it was determined by research in the conditions of a construction site and laboratory:
- In 3 days, the solution acquires about 30% of the strength laid down in the brand, subject to high humidity and air temperature not lower than 150С.
- From 7 to 14 days, concrete acquires a hardness sufficient for human movement up to 80% of the characteristics laid down.
- 28 days - a fixed period of full set of embedded strength. During this period, the facility can be operated at full speed.
- Concrete is distinguished from other materials by its ability toincrease its characteristics during the period of operation. It is noted that after 90 days the stone exceeds the set parameters by 20%.
Formwork influence: yes or no
When building any objects, the method of monolithic construction is often used. The question arises: how long does concrete dry in the formwork, does it affect the hardening time of the structure?
The solidification process is nothing but a chemical reaction. Only external conditions can affect its speed: the temperature and humidity of the environment and some catalysts - additives that are introduced into the mixture in production to obtain and enhance certain qualities of the material.
For formwork, wooden boards, metal sheets and construction plywood are used. These materials are designed to fix the shape of the future design. They are able to partially retain heat in the solidifying volume, but not in such quantity that a significant acceleration of processes occurs.
With proper care, the concrete in the formwork hardens at the time determined by the temperature regime:
| Temperature conditions, 0C | Setting time, days |
| 0…5 | 14 |
| 5…10 | 10 |
| 10…15 | 7 |
| 15…20 | 5 |
| 20…25 | 4 |
| 25…30 and up | 2-3 |
After the specified deadlines, the formwork is removed, the structure continues to harden on its own, at this time, installation work on the construction of the object continues.
Time versus volume
Monolithic concrete structures have different dimensions. Foundations for buildings and structures are carried out in several configurations: tape, pile, slab. Their bodies are different volumes.
To find out how long the concrete foundation dries, you should focus on the thickness of the structure. Since hardening and solidification is a chemical reaction, it must proceed evenly throughout the volume. When petrified, heat is released. Accordingly, the inner part of the element comes to the final state more slowly. In addition, excess liquid evaporates faster in the upper layers, and the material acquires sufficient structure to continue installation work.
Especially thick structures, such as slab foundations for large structures, swimming pools, shopping centers, can withstand from three months, until the entire volume of the poured base comes to the design state.
How to increase curing speed
How much concrete dries outside under normal conditions, we have determined. Now consider what methods this process can be accelerated:
- Maintenance of a constant level of humidity should be carried out immediately after laying the concrete mixture in the formwork. To do this, the completed forms are coveredwaterproof material (film or tarpaulin) and constantly sprinkled with water.
- Creation of working temperature conditions is relevant for winter construction. As you know, during frost, water crystallizes and expands, which is unacceptable in a hardening structure. To prevent this, in winter, the structure in the formwork is artificially heated to speed up chemical processes. In addition, special catalysts are added to the mixture during production, which contribute to uniform and rapid setting of the components.
- The correct calculation of the ratio of water and cement ensures timely solidification of the mixture without the need for additional expulsion of excess water.
