Fine concrete is a special-purpose building material. It is used in cases where the use of ordinary heavy concrete is not possible. This includes the sealing of joints, the filling of heavily reinforced structures and the arrangement of waterproofing. But before preparing the mixture, it is necessary to familiarize yourself with its technical characteristics, as well as features.
Specifications
The concrete described above is a structural material created on the basis of cement. The main ingredients are mixed sand and water. This type of concrete is also called sand, and its main difference is that the fraction of particles of materials in the composition should not be more than 2.5 mm.
Density of heavy and especially heavy concrete can vary from 2200 to 2500 kg / m³. The curing temperature may be in the range of +5 to +30 ° C. The ability to undergo pressure is maintained at 25 MPa. The compressive strength is 18.5 MPa, with regard to the design resistance, it is equivalent to 14.5 MPa.
Frost resistance can vary depending on the ingredients used and is equal to the limit of 50 to 1000 freezing and thawing cycles. Fine concrete has a certain level of water resistance. This parameter is indicated by the letter “W” and may correspond to a limit of 2 to 20.
additional characteristics
Heavy and fine-grained concrete has 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, grains are located at some distance from each other.
If the volume of the binder is reduced, then this will lead to a decrease in water consumption and mobility. Fine-grained concrete for structural purposes can be prepared in the following respects: 1: 3,5 and 1: 4. Concrete will become more viscous if the sand content is increased. Plasticity will improve with the addition of water and plasticizers. If the amount of cement is reduced, this can cause delamination.
For reference
Using the optimum proportions when mixing concrete, you will ensure normal density with working mobility. If the work was carried out correctly, then fine-grained concrete 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 correct composition, 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 aggregate. This facilitates transportation. Among other things, concrete is versatile.
Area of use
Heavy and fine-grained concrete 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 in the transportation of gravel and gravel.
The characteristics of the monolith can be improved by using a plasticizer, reducing the final cost. Polymer filler makes the material more resistant to aggressive environment, frost and water. Heavy and fine-grained concrete, the technical conditions of which were mentioned above, are used in monolithic and complex reinforced structures, for example:
- thin-walled partitions;
- arches and domes;
- in the manufacture of park sculptures;
- in the formation of channels, reservoirs and pipes;
- in the production of pavers ,
- paving slabs and borders;
- in the manufacture of hinged siding for facades and basement;
- in the construction of hydraulic structures;
- when forming arched ceilings.
In the field of construction, such a composition can level surfaces. If you use concrete grade B25, then with its help you can iron the concrete floor, close up joints and cracks in the walls.
The main advantages and disadvantages
Fine-grained concrete, the composition of which is mentioned in the article, has many advantages, among them are:
- high strength factor;
- the ability to form materials with special properties;
- high resistance to vibration loads;
- homogeneous structure;
- the possibility of transformation of the mixture.
However, the material has its drawbacks, they are increased cement consumption, 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 concrete, the technical conditions of which are mentioned in the article, are made using the basic components of cement and water. But fillers can become river sand and gravel. In the first case, the fraction should not exceed the mark of 2.5 mm. Crushed stone can be added if its particle size does not exceed 10 mm. Also, in addition to this, the ingredient composition may suggest the need for plasticizers. This allows you to achieve a homogeneous structure.
Adding cement in larger quantities than required, you risk getting a solution that will be uncomfortable in the masonry. If this ingredient is not added in sufficient volume, then after solidification the material will have low strength. Concrete heavy and fine-grained (GOST 7473-2010) can be made by casting. This technology relates to the formation of borders, arches, as well as paving slabs. In the case of thin-walled structures, the technology of dense reinforcement is used. This material quite often forms the basis of road surfaces, because it has high frost resistance and water resistance.
Aggregate Preparation Features
The components of fine-grained concrete should be selected taking into account the standards. The solution should contain components that have different technical characteristics. Standards regulate the use of sand, split into sizes. First, the sand is sifted through a grid, the side of which is 2.5 mm. This allows you to get the first fraction. Then a mesh with a mesh size of 1.2 mm is used.
After the cells are reduced, they should correspond to a size of 0.135 mm. Everything that passes through the grid for the last time will be used as a placeholder. Fine-grained concrete 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 shallow second fraction.