Fine-grained concrete: specifications, GOST

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Fine-grained concrete is a building material for special purposes. It is used in cases where the use of conventional heavy concrete is not possible. This should include the sealing of joints, the pouring of heavily reinforced structures and the arrangement of waterproofing. But before preparing the mixture, you must familiarize yourself with its technical characteristics, as well as features.

Specifications

The concrete described above is a structural material based on cement. The main ingredients are sand and water of different fractions. This type of concrete is also called sandy, and its main difference is that the fraction of particles of materials in the composition should not be more than 2.5 mm.

The density of heavy and extra heavy concrete can vary from 2200 to 2500 kg/m³. Curing temperature can be equal to the limit from +5 to +30 °C. Abilityendure pressure is kept at 25 MPa. The compressive strength is 18.5 MPa, as for the design resistance, it is equivalent to 14.5 MPa.

Frost resistance may vary depending on the ingredients used and is limited to 50 to 1000 freeze and thaw cycles. Fine-grained concrete has a certain level of water resistance. This parameter is indicated by the letter "W" and can correspond to a limit of 2 to 20.

Additional Features

Heavy and fine-grained concretes have the ability to take a given shape for a certain time, it is affected by the ratio of cement and sand, as well as the amount of water. If we are talking about fatty mixtures, then they can be prepared in a ratio of 1 to 1 or 1 to 1.5. In such solutions, the grains are located at some distance from each other.

If the volume of the binder is reduced, this will lead to a decrease in water consumption and mobility. Fine-grained concrete for structural purposes can be prepared in the following ratios: 1:3, 5 and 1:4. The concrete will become more viscous if the sand content is increased. Plasticity will improve with the addition of water and plasticizers. If you reduce the amount of cement, it may cause delamination.

For reference

Using optimal proportions when mixing concrete, you will ensure normal density with working mobility. If the work was carried out correctly, then fine-grainedconcrete will have a fairly high density, good uniformity, moisture resistance and axial bending strength. The frost resistance of such a material is increased, and with the right composition, the mobility is normal in order to distribute the mixture as quickly as possible. Among the positive features of the material is its low cost, which is affected by the absence of large aggregates. This makes transport easier. Among other things, concrete is versatile.

Use area

Concrete heavy and fine-grained can be used in those regions where there is a shortage of coarse aggregate. When mixing, an increased volume of cement is used, which may be accompanied by difficulties in selecting the ratio of ingredients. But the disadvantages are offset by savings on the transportation of crushed stone and gravel.

The characteristics of the monolith can be improved by using a plasticizer, reducing the final cost. The polymer filler makes the material more resistant to aggressive environments, frost and water. Heavy and fine-grained concretes, the specifications of which were mentioned above, are used in monolithic and complex reinforced structures, for example:

• thin-walled partitions;
• vaults and domes;
• when making park sculptures;
• when forming channels, tanks and pipes;
• in the production of paving stones,
• paving slabs and curbs;
• in the manufacture of hinged siding for facades and plinth;
• during the construction of hydraulic structures;
• when forming arched ceilings.

In the field of construction, this composition can be used to level surfaces. If you use concrete grade B25, then with its help you can iron the concrete floor, seal the seams and cracks in the walls.

Main advantages and disadvantages

Fine-grained concrete, the composition of which is mentioned in the article, has many advantages, among them should be highlighted:

• high strength factor;
• ability to form materials with special properties;
• high vibration resistance;
• homogeneous structure;
• ability to transform mixture.

However, the material has its drawbacks, they are increased consumption of cement, high hardness and shrinkage during casting. When it comes to hardness, it can make processing difficult.

Composition and state standards

In the manufacture of the described material, GOST is used, heavy and fine-grained concrete, the technical conditions of which are mentioned in the article, are made using the basic components of cement and water. But the fillers can be river sand and gravel. In the first case, the fraction should not exceed 2.5 mm. Crushed stone can be added if its particle size does not exceed 10 mm. Also, in addition, the ingredient composition cansuggest the need for plasticizers. This allows you to achieve a homogeneous structure.

By adding more cement than required, you run the risk of getting a mortar that will be inconvenient in masonry. If this ingredient is added in insufficient volume, then after solidification the material will have low strength. Heavy and fine-grained concrete (GOST 7473-2010) can be produced by casting. This technology applies to the formation of curbs, arches, and paving slabs. In the case of thin-walled structures, dense reinforcement technology is used. This material often forms the basis of road surfaces, because it has high frost resistance and water resistance.

Features of preparation of aggregate

The components of fine-grained concrete must be selected according to standards. The solution must contain components that have different technical characteristics. Regulations regulate the use of sand split into sizes. First, the sand is sifted through a mesh whose side is 2.5 mm. This allows you to get the first fraction. Then a grid with a mesh size of 1.2 mm is used.

After the cells are reduced, they should fit the size of 0.135mm. Whatever passes through the mesh the last time will be used as the placeholder. Fine-grained concretes should be prepared using sand of the first group in a volume of 20 to 50% of the total mass. The remaining volume will be a fine second fraction.