The bulk density of concrete: the characteristics of light

In paragraphs GOST 25192-82, building mixtures obtained by mixing the binder with various aggregates are primarily divided by purpose, structure, and hardening conditions. However, along with this, classification can be made by weight category. With this option, the mass of concrete in a cube is taken into account, due to which it is possible to determine the scope of the composition.

The main types of mixtures

The weight of the composition can act as one of the characteristics, as it provides an opportunity to assess the mechanical and physical properties. If the structure maintains strength and durability, the use of lighter solutions significantly reduces the cost of the construction process.

Particularly lightweight concrete

This category includes mixtures whose density does not exceed 500 kg / m3, therefore, they are mainly used for the formation of thermal insulation layers and enclosing structures. It is possible to reduce the weight of the material due to the porous structure, which also allows to improve the thermal insulation qualities.

As for strength, it decreases markedly. Due to the presence of voids in the finished products, the deformation properties change and, therefore, the elastic modulus also decreases.

The main representative of this category is cellular concrete, consisting of 85 percent of air bubbles.

• Mechanical way obtaining such products consists in mixing the finished mass with pre-prepared foam. After curing, an artificial stone is formed with air inclusions, which are evenly distributed throughout the product.
• Chemical method involves the addition of special gas additives, creating the effect of expansion solution. The main disadvantage is the presence of through pores, which leads to a decrease in resistance to moisture.

Addition! The active use of modern additives makes it possible to improve the strength indices of extremely light mixtures several times, but in this case the final price of the product increases.

Lungs растворы

Such mixtures have a porous aggregate such as expanded clay and perlite, so they are used more often to create a heat-insulating layer than for the manufacture of full-fledged structures. Usually a mass of 1 m3 of concrete ranges from 500-1800 kg. As for the structure, it can be large-pore, porous or dense.

Due to their versatility, light compositions are used in many building elements of structures and buildings. In terms of frost resistance, they are inferior to heavy mixtures, but can be used in wall structures if they contain aggregate with low water absorption. These include, for example, expanded clay.

Heavy mixes

If the mass of 1 cube of concrete is 1800-2500 kg, then it falls into the category of heavy compounds. Such solutions are actively used for the construction of walls and load-bearing elements of individual buildings and industrial facilities.

The main technical requirements are referred to in paragraphs of GOST 26633-91.

• In manufacturing, Portland cements, pozzolanic and sulphate-resistant cements, as well as other technical specifications, must be used as binders.
• As a aggregate for heavy concrete most often used gravel from dense rocks or crushed stone from ferroalloy and blast furnace slags, which are waste of ferrous metallurgy.
• Fine aggregate can serve as natural sand or screenings, resulting from the crushing of rocks. The average density of grains should be 200-2800 g / cm3.
• The brand of binder is selected depending on the purpose of the structure and operating conditions on the basis of technical requirements, as reflected in paragraphs of GOST 30515-2013.

Note! If it is necessary to use placeholders with characteristics below the requirements of official standards, a preliminary study should be carried out.

Particularly heavy formulations

Mixtures of this category have found their use in special structures to protect against radiation from nuclear power plants and other potentially dangerous objects. The mass of the cube of concrete in this case may exceed 2500 kg. High-density materials are commonly used as a filler: magnetite, barite, and hematite.

During the work it is necessary to adhere to certain requirements. Mixing components should be carried out for more than two minutes, otherwise the quality of the composition will noticeably decrease. Vibration equipment should be used without fail to consolidate the solution.

To increase the protective characteristics, special additives are added to very heavy concrete, including light components like cadmium, lithium and boron. The composition of the mixture, as a rule, is determined by the same method as for ordinary solutions, but experimental mixes are carried out. The main problem is the tendency of the prepared mixture to delaminate during transportation, compaction and packing.

As a conclusion

The presented instruction, considering the weight categories of concrete solutions, will help individual developers in choosing a building mixture for products and structures created by their own hands. During the work it is necessary to understand that the mass of reinforced concrete will always be higher than the usual composition, since it contains a metal frame inside.

For more information, see the video in this article.