Concrete: how much it dries, hardens and sets according to temperature

Concrete is widely distributed in construction due to its operational characteristics: it is solid, wear-resistant and durable. To obtain these qualities, structures must be cast using special technology. If you violate the rules for laying the solution, the element will not acquire the expected characteristics. How to use concrete, how much 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 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 types of binders that make up the basis of the solution:

1. Cement mixes. Of these, solutions are prepared for the manufacture of supporting and critical structures. The pour time of the mixture to the working state is from 7 to 14 days.
2. 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 solution includes a mixture of pozzolanic cement and gypsum powder. The design becomes operational after 2 days.
   
3. Silicates significantly reduce the cost of concrete, while the strength characteristics remain at a high level. The time to achieve the working condition of the material depends on the proportions of the mass and method of solidification. In an autoclave, reactions occur up to 2 days.
4. Polymer cement binder is used for kneading decorative solutions with the inclusion of crumbs of marble, granite, natural and artificial pigments. The solution hardens after an hour, you can expose the surface to stress after 3-4 days.

Determining factors

In addition to the established average hardening time of the concrete mixture, the duration of hardening is affected by:

1. Air humidity. The hardening process is a chemical reaction between an astringent and water. Accordingly, as soon as the fluid ends in the body of the structure, this action will cease. To avoid dehydration and cracking of the concrete volume, it is necessary to create a condition of sufficient humidity of at least 75%.
2. Ambient temperature. Since water is involved in the reaction, it is necessary to prevent its solidification in the cold season. In the process of hardening, heat is generated from the structure, at an elevated temperature the interaction of the components occurs much faster.
3. The type of binder and the amount of water in the solution also determine how much concrete should dry. Gypsum powder with a sufficient amount of liquid acquires a solid structure in a couple of hours, Portland cement requires about 12-16, depending on the conditions listed.
4. The thickness of the structure affects the overall solidification of the solution.

These factors must be taken into account when designing construction works in which concrete is used. How long the structure dries depends on the environment and proper maintenance of the laid volume.

Average terms

Most often, classic cement concrete is used for the construction of critical structures. How much the structure dries from it, was determined by research in a building site and laboratory:

• For 3 days, the solution acquires about 30% of the strength inherent in the brand, subject to high humidity and air temperature not lower than 15 ⁰ C.
• From 7 to 14 days, concrete acquires a hardness sufficient for human movement up to 80% of the inherent characteristics.
• 28 days - a fixed period of a full set of mortgaged strength. During this period, the object can be operated in full swing.
• Concrete is distinguished from other materials by the ability to increase its characteristics during the period of operation. It is noted that after 90 days the stone exceeds the inherent parameters by 20%.

Formwork effect: whether or not

In the construction of any objects often use the method of monolithic construction. The question arises: how much concrete in the formwork dries, does it affect the hardening time of the structure?

The solidification process is nothing more than a chemical reaction. Only external conditions can influence its speed: ambient temperature and humidity and some catalysts - additives that are introduced into the mixture at the factory to obtain and enhance certain qualities of the material.

For formwork, wooden boards, metal sheets and building plywood are used. These materials are designed to fix the shape of the future design. They are able to partially retain heat in a hardening volume, but not in such quantities that there is a significant acceleration of processes.

With proper care, the concrete in the formwork solidifies in the time determined by the temperature regime:

After the specified periods, the formwork is removed, the structure continues to harden on its own, at this time, installation work continues on the construction of the object.

Time versus volume

Monolithic concrete structures have different dimensions. Foundations for buildings and structures are performed in several configurations: tape, pile, plate. Their bodies make up different volumes.

To find out how much the concrete foundation dries, you should focus on the thickness of the structure. Since hardening and solidification is a chemical reaction, it should go evenly throughout the volume. During petrification, heat is released. Accordingly, the inner part of the element slowly comes to the final state. In addition, in the upper layers the evaporation of excess fluid occurs faster, and the material acquires a sufficient structure to continue installation work.

Particularly 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 foundation comes into design condition.

How to increase hardening speed

How much concrete dries on the street under normal conditions, we determined. Now consider what methods this process can be accelerated:

1. Maintaining a constant level of humidity should be carried out immediately after laying the concrete mixture in the formwork. For this, the filled forms are covered with a waterproof material (film or tarpaulin) and constantly watered.
2. Creating 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 the winter period the structure in the formwork is artificially heated to accelerate chemical processes. In addition, at the production site special catalysts are added to the mixture, which contribute to the uniform and quick setting of the components.
3. The correct calculation of the ratio of water to cement ensures timely solidification of the mixture without the need for additional expulsion of excess water.