High-strength concrete is one of the modern building artificial materials. It differs from the classic version in operational properties and technical indicators.
Products containing high-strength concrete are much more reliable than conventional mortars. Structures made of this material will be of high quality and durable.
Features and classification
High-strength types of concrete include fine-grained and heavy compositions that have different grades. Let's consider each of them in more detail.
M600, M700 and M750
These grades of high-strength concrete have good density and strength, as well as a high degree of water resistance. Such concrete is used in the construction of stairs, bridges, pools, basements, various load-bearing structures.
M800
It has not only high strength, but also resistance to aggressive environments. That is why such concrete is often used during the construction of objects with a specific specific purpose.
M900
Concrete of this type has an increased parameterstrength. Such material is used in those areas where it is required to build especially reliable structures.
M1100
This is a special purpose concrete. It is distinguished not only by its extremely high strength, but also by its resistance to moisture and the effects of aggressive environmental factors. Typically, this material of this grade is used during the construction of hydraulic and military facilities, bridges, mines.
As for the minimum value of compressive strength, this is class B60. Values above are allowed.
A feature of high-strength concretes is that they harden quickly. Due to this, their strength characteristics increase.
Composition
Substances that are part of the building mixture affect the resulting product.
The following components are the basis:
- Astringents. Usually their role is played by the most active Portland cements with a certain consistency index. Experts advise using components with a density of 25%. The minimum activity indicator should be approximately 500-600. Since the resulting concrete acquires strength at an accelerated pace, it is not necessary to use various additives that will speed up the setting of the composition.
- Sand. The production of building mixtures with high strength cannot be carried out without the use of feldspar-type quartz sands with a fine or coarse fraction. For fine-grained varieties, particles ranging in size from 0.14 to 0.63 mm are suitable, and for coarse-grained varieties, from 1.25 to 5 mm. In order for the building composition to fit better during its application, more of the first components are used. In some cases, the ratio of large and small particles is equalized. In some grades (up to M800), only medium or coarse sand is used. State standards are always taken into account.
- Large filler. In such compositions, gravel plays a similar role. Its compressive strength at high humidity should be 1.5 times greater than that of the solution. Before adding such a filler, it is sorted and cleaned. The particles are divided into fractions of 0.5-1 cm, 1-2 cm, and 2-4 cm. The type of crushed stone is chosen depending on the reinforcement used and the planned width of the future product. If the structure has weak reinforcement and the walls are thick, then particles up to 7 cm in size are used. For concrete with increased strength, only dry aggregate is used, which meets the requirements in GOST.
- Fine additives. Silica-type dust is poured into concretes with increased strength. But this is not always practiced. For example, if the strength index is C 55/67 or C 60/77, then you can not use such an additive. Silica dust is obtained during production using flint. It performs several main tasks. First, it enters the empty space between the particles of the main components. Due to this, the density of the concrete product increases. Secondly, it interacts with slaked lime, due to which the strength index increases even more. Third, the reaction between cement and sandgetting better too.
In addition to the listed components, additional artificial plasticizers can be used in concretes of this type.
Key Features
High-strength, fine-grained concretes have many advantages, due to which the service life of the resulting products increases.
A solution of concrete in liquid form has the following characteristics:
- Delamination is minimal.
- The amount of oxygen in the mixture is not more than 1%.
- The density of the structure varies between 1-1, 4.
- Rheological properties maintained up to 4 hours.
A distinctive feature of high-strength concrete is that it retains its working properties for a long time. This is important, since the material can be transported within two hours to the place where all the work is carried out. But the indicator of the density of the mixture also affects. It must be homogeneous, otherwise the likelihood of its delamination in the future increases.
High-strength cured concrete monoliths have the following properties:
- Curvature is minimal.
- Wear resistance is high.
- Strength when pressed - from 50 to 100 MPa.
But you need to remember that there is a possibility of microscopic cracks in high-density concrete when squeezed and in contact with water at the same time.
Use of high-strength concretes
Such materials are used during the construction of facilities where it is required to reduce the weight of the building and reduce the dimensions. They are used when you need to create a reliable, high-quality product.
Usually high-strength concretes are recommended in the following cases:
- Filling floors in industrial buildings.
- Establishment of warehouses for the placement of radioactive components.
- Construction of bridges, other similar structures.
- Creating multi-level buildings.
High strength concrete is quite popular among all building materials.
Production
The main feature of the production process for creating high-strength concrete is the realization of the natural workability of the material during all construction works.
This can be achieved by following these rules:
- Special high-speed mixers are used to create the mixture.
- It is required to constantly monitor the moisture content in the fillers.
- It is important to compare the setting time and transport time.
- Always observe proportions, dosages.
- Always add the ingredients in the correct order as shown in the recipe.
The quality of high-strength concrete also depends on the proper care of the resulting product. The material must be covered with a wet composition in the first 3 days. This will ensureincreased resistance of the resulting product to the destructive factors of the external environment.
Specialists to maintain the high quality of concrete always monitor the components of the mixture. They check the performance of equipment, the characteristics of fillers, various components, and monitor workers. If necessary, determine non-compliance factors.
Conclusion
High-strength lightweight concretes are used in various industries. This material ensures the reliability and durability of the building under construction. Before choosing a particular option, it is recommended that you first consult with an experienced builder.
