Fine-grained concrete is a buildingspecial purpose material. It is used in cases where the use of ordinary heavy concrete is impossible. This includes the sealing of joints, the filling of thick-reinforced structures and the arrangement of waterproofing. But before preparing the mixture it is necessary to familiarize yourself with its technical characteristics and features.
The concrete described above is a structuralmaterial, created on the basis of cement. As the main ingredients are different sand and water. This type of concrete is also called sandy, and its main difference lies in the fact that the fraction of material particles in the composition should not be more than 2.5 mm.
The density of heavy and particularly heavy concrete canvary between 2200 and 2500 kg / m³. The curing temperature can be the limit from +5 to +30 ° C. The ability to undergo 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 can vary depending onused ingredients and is equal to the limit of 50 to 1000 cycles of freezing and thawing. Fine-grained concrete has a certain level of watertightness. This parameter is indicated by the letter "W" and can correspond to the limit from 2 to 20.
Heavy and fine-grained concretes have the abilityto occupy the given shape for a certain time, it is affected by the ratio of cement and sand, as well as the amount of water. If it is a question of fatty mixtures, they can be prepared in a ratio of 1 to 1 or 1 to 1.5. In such solutions, grains are located at a certain distance from each other.
If the amount of binder is reduced, this will entaildecrease in water consumption and mobility. Fine-grained concrete of constructive purpose can be prepared in the following ratios: 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 you reduce the amount of cement, this can cause stratification.
Using the optimum proportions when closingconcrete, you will ensure a normal density with working mobility. If the works were carried out correctly, the fine-grained concrete will have rather high density, good uniformity, moisture resistance and strength on axial bending. The frost resistance of such a material is increased, and with the right composition, the mobility is normal to distribute the mixture as quickly as possible. Among the positive features of the material is the low cost, which is affected by the absence of a large aggregate. This facilitates transportation. Among other things, concrete is versatile.
Scope of use
Concretes heavy and fine-grained can be appliedin those regions where there is a shortage of large aggregate. When closing, an increased volume of cement is used, which can be accompanied by difficulties in selecting in the ratio of ingredients. But the minuses are compensated by the savings in the transportation of crushed stone and gravel.
Characteristics of the monolith can be improved byuse of plasticizer, reducing the final cost. Polymer filler makes the material more resistant to aggressive environment, frost and water. Concretes heavy and fine-grained, the technical conditions of which were mentioned above, are used in monolithic and complex reinforced structures, for example:
- thin-walled partitions;
- vaults and domes;
- when manufacturing park sculptures;
- when forming channels, reservoirs and pipes;
- in the production of pavers,
- paving slabs and curbs;
- in the manufacture of hinged siding for facades and socle;
- when erecting hydraulic structures;
- when forming arch roofs.
In the field of construction such a composition canalign the surfaces. If you use concrete grade B25, then with it you can glaze the concrete floor, seal 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 it should be noted:
- high coefficient of strength;
- 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, theyconsist in increased consumption of cement, high hardness and shrinkage in the casting of products. When it comes to hardness, it can make processing difficult.
Composition and state standards
When manufacturing the described materialGOST, 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 fillers can become river sand and crushed stone. In the first case, the fraction should not exceed a mark of 2.5 mm. Crushed stone can be added if its particle size does not exceed 10 mm. Also, in addition, the ingredient composition may assume the need for plasticizers. This allows obtaining a homogeneous structure.
Adding more cement thanyou need to risk getting a solution that will be uncomfortable in the masonry. If this ingredient is added in insufficient volume, then after hardening the material will have low strength. Concretes heavy and fine-grained (GOST 7473-2010) can be manufactured by casting. This technology refers to the molding of curbs, arches, and paving slabs. In the case of thin-walled structures, thick reinforcement technology is used. This material often falls in the basis of road surfaces, because it has high frost resistance and water resistance.
Features of aggregate preparation
Components of fine-grained concrete should betailored to standards. The solution must contain components that have different technical characteristics. The regulations regulate the use of sand, split into sizes. First, the sand is sieved through a mesh, the side of which is 2.5 mm. This makes it possible to obtain the first fraction. Then a grid with a mesh size of 1.2 mm is used.
After the cell is reduced, they mustmatch the size of 0.135 mm. Anything that passes through the grid 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 small second fraction.