Concrete hydraulic: GOST, composition, technical characteristics, properties, application

For structures and structures that come into contact with the water in different degrees, a special material is required that can withstand the corrosive effects of the liquid medium. For construction in such conditions, use concrete hydraulic engineering. It has the necessary characteristics for safe operation of the erected object.

Definition

Concrete hydraulic engineering refers to the category of heavy, it is used for the construction of embankments, bridges and other structures, some of the structures of which are partially or completely submerged in water, or have contact with it.

Feature of the material is its ability to maintain its original characteristics in an aggressive environment without reducing the quality and bearing capacity of the element. Some functions, for example strength, in the environment with time increase with the condition of preserving the integrity and structure of the stone.

Classification

There is a certain set of requirements that must be met by concrete hydraulic engineering. GOST 26633-2012 "Concrete is heavy and fine-grained. Specifications »regulates the quality of the components of the mixture and the properties of the finished solution. The document has an international character, it was adopted by 8 countries.

According to GOST, hydrotechnical concrete is divided into several groups according to the degree of immersion and impact of the aquatic environment:

1. Surface.
2. Underwater.
3. For the unstable water level.

According to the volume of the created structure, the material is divided into:

1. Massive - complex shapes and large dimensions of the element, accompanied by uneven hardening with the release of heat.
2. Nonmassive - simple designs with small dimensions.

As the force affects the hardened object:

1. For pressure systems.
2. For non-pressure elements.

Additional classification of the place of use of concrete:

1. For internal structures (they are less prone to washing out, water pressure, but must withstand static effects).
2. For external elements and surfaces (such are affected by the active movement of water and unstable chemical background).

Mixture composition

The mortar must meet the requirements of GOST for obtaining a stone of sufficient hardness, strength and safety. Quality control is carried out by all components included in hydraulic concrete. Composition of the mixture:

1. The main component - an astringent. For resistant to aggressive waters, sulfate-resistant cement is used. For a variable level of immersion take a hydrophobic or with the inclusion of plasticizing additives. In other cases, use pozzolanic, slag or Portland cement.
2. A fine aggregate is quartz sand, it increases the resistance of concrete to water. It should not contain small impurities and debris - in wet conditions, inclusions can significantly weaken the material.
3. A large aggregate is gravel and crushed stone from sedimentary and igneous rocks. This is characterized by high hydrophobicity, frost resistance. The stone fraction depends on the technical characteristics of the concrete solution required for operation under specific conditions. The shape of the aggregate should be volumetric and convex, crushed stone or gravel has less strength.
4. Additives - improvers solution properties. They increase the resistance of the stone to temperature changes, aggressive effects of water, reduce heat generation as necessary, prevent the occurrence of cracks.

The properties of all components, their parameters, the exact formulation of the solution are prescribed in GOST 26633-2012 item 3. Compliance with the standards should be carried out in any production, the finished mixture receives a document on compliance with the standard.

Specifications

The material has many varieties. They are distinguished by the composition and properties that the hydrotechnical concrete must possess. Technical characteristics depend on the brand and type of composition. The main ones include compressive strength, axial bending, stretching, frost resistance and hydrophobicity. The working solution is selected based on the combination of these indicators, since each lot of properties may differ, which is unacceptable for this material.

Strength

The first and most important indicator is the magnitude of the compression resistance, since most structures experience a vertical force load from the building above the building.

Strength of concrete is determined by creating a cube for testing and then checking it under the press. The prototype is aged from 28 to 180 days for recruitment strength. In the case of hydrotechnical material, the cube is placed in water for the time of hardening.

Tests are carried out under the action of forces before the appearance of cracks.

According to the results of the study, concrete is awarded a class from B3.5 to B60. The most common types are B10-B40.

Tensile and bending strength

Constructions that are not affected by the vertical load are subject to other influences - axial stretching and bending. To understand if concrete will withstand such deformations, it is checked in the laboratory. The tensile strength grade is Bt0.4 ... 4.0.

Water Resistance

It is determined in laboratory conditions on cubes-samples of the same age as in the first case. The essence of the test consists in a gradual increase in the pressure of water before it percolates through the body of concrete. By the result, the stone is appropriated for water resistance W2-20.

For aggressive conditions of sea water, high pressure use concrete hydraulic engineering not lower than W4.

Frost resistance

In conditions of high humidity, special attention is paid to temperature changes with the possibility of water hardening. As is known, upon expansion, the liquid crystallizes and damages the building materials that it has penetrated. To prevent this from occurring with a responsible design, special hydraulic additives and plasticizers are added to the solution in the production, increasing the resistance of the concrete to hardening.

Frost resistance grade F shows how many cycles of full alternate freezing and thawing withstand a sample of concrete with a loss of strength of not more than 15%. For a hydrotechnical mixture, the tests are carried out with water with its heating and turning into ice.

According to the results of the study, hydrophobic concrete is given the F50-300 frost resistance grade.

Mix improvers

Indicators of strength, water resistance and frost resistance are laid during the mixing of the solution at the plant. Special properties of hydraulic concrete are determined by salts of different metals and composite compounds.

Additives-modifiers are divided into 2 groups.

I group reduces water absorption up to 5 times to the duration of the design strength set of 28 days. Among the most used are:

• Phenylethoxysiloxane 113-63 (formerly FES-50).
• Aluminomethylsiliconate sodium AMCP-3 (Russia).
• "Plastil" (Russia).
• Hydroconcrete (EC).
• Addiment DM 2 (Germany).
• Liga Natriumoleat 90 (Russia).
• Sikagard-702 W-Aquahod (Switzerland).

Group II is less powerful (decrease to 2-4.8 times). Its application is possible for the mixing of surface concrete:

• Polyhydrosiloxanes 136-157M (formerly GCG-94M) and 136-41 (formerly GCG-94).
• "COMD-C".
• Stavinor Zn Ei Stavinor Ca PSE.
• HIDROFOB E (Slovenia).
• Cementol E (Slovenia).
• Sikalite (Switzerland).
• Sikagard-700S (Switzerland).

III group for the creation of hydraulic concrete is not applied. Additives reduce water absorption up to 2 times.

Other properties

When choosing a working mixture, not only the main characteristics of hydraulic concrete are taken into account, but also its other parameters:

• Shrinkage value.
• Resistance to deformation.
• Degree of resistance to water flow and pump pressure.

There is no single recipe for hydraulic concrete: in each case, the chemical composition of water, the amount of pressure and other loads are taken into account. In accordance with the requirements, fillers and additives are used that can ensure reliable operation of the future stone.

Application

Stacking the solution under the water layer is a responsible and difficult task. It is filled with large volumes to prevent uneven congealing and erosion. Due to the specifics of the installation in the body of the congealing structure, thermal stresses and differences arise which need to be regulated. To avoid overheating and premature deformation of the mold, plasticizers and special types of cement are added to the solution:

• Pozzolanic.
• Slag.
• Hydrophobic.

For the construction of coastal structures use concrete hydraulic engineering. Its application is widespread:

• Bridges, their supports and purlins.
• Arrangement of embankments and fortifying banks of walls, ports.

• Pools, their bowls and surrounding zones.
• Walls of sewerage wells and mines.
• Subway tunnels.
• Technical facilities: dams, hydropower plants, breakwaters.

In house building, low-grade hydraulic engineering concrete is used for pouring a foundation with a high level of groundwater or its significant differences during the melting of snow and heavy rains.