Fillers for concrete - features of porous, heat-insulating

As you know, concretes are different in composition and structure, and their components can also be different. These variable components include aggregates for concrete - they can be porous, dense, or have some special properties, such as heat resistance or acid resistance. Next, we take a closer look at the main types of fillers and their features.

General information

What is a placeholder? As a rule, it is a small crushed stone, the choice of which, most often, depends on the nearest deposits.

Traditional fillers for concrete are the following components:

• Crushed stone;
• Sand;
• Gravel;
• Puma, а также многое другое.

Often, as fillers use all sorts of waste like slags. Their use is due to savings, since the price of concrete in this case is significantly reduced.

Typically, in the concrete dissolved aggregates account for 80-85% of the total mass. It follows that the importance of choosing this component is difficult to overestimate, since it constitutes the bulk of the material.

Types of fillers

Aggregates for mortars and concretes can be classified by purpose:

• For heavy or light concrete;
• Decorative;
• Thermal insulation;
• Acid-resistant and other types of special materials.

In addition, all existing types of aggregate can be divided into two types:

• Large;
• Small.

Now take a closer look at the purpose of each.

Small

The use of fine filler is necessary to reduce the voids between the coarse aggregate particles. It depends on how well the particles are located, how strong the concrete will be.

Small заполнитель для бетона состоит из мельчайших частиц. Преимущественно, в качестве мелкого заполнителя используют песок. Основным его достоинством является минимальный размер крупиц, который составляет 0,16-5 мм, а также высокая плотность - 1,8 г/см3.

There are two types of sand:

• Natural - obtained as a result of the destruction of rocks by natural means;
• Artificial - obtained as a result of special processing of rock.

The most commonly used natural sand of the following types:

• Mica;
• Quartz sand;
• Calcite;
• Feldspar.

To determine the quality of sand, it is necessary to pay attention to such moments as:

• Mineral and grain composition;
• The presence of harmful impurities.

The grain composition of the aggregate is determined using a set of sieves with different cell sizes. Of course, it is not necessary to sift all the sand, one or two kilograms will be quite enough. Large grains in its composition should be no more than 5 percent, in addition, it should not contain particles greater than 10 mm.

Experts even came up with a special term - “module size”. This term refers to the ratio of the remaining large particles in the sieve to the rest of the sand taken for the sample.

As a result, it can be said that the size of the aggregate of concrete is an important point that affects the quality of concrete. Therefore, when using it, it is necessary to monitor the percentage ratio of particle sizes. The smallest grains like dust should be no more than three percent, and fractions of 0.16 - no more than 10 percent.

Note! The clay content in the sand can reduce the frost resistance of the concrete structure. Therefore, it is customary to clean the sand before use by washing.

When using natural sand it is also necessary to pay attention to the content of impurities in the composition. Sometimes there is a filler with organic additives, the use of which leads to the destruction of cement in the future. The presence of such impurities is determined by the color method.

I must say that there are non-shrinkage concrete on the fine aggregate, to which special mixtures and polymer fibers are added. The material receives special properties through the use of the smallest fractions of the filler. Fiber in this case increases the strength of concrete.

Coarse aggregate

The most common large aggregates are gravel and crushed stone. Their particles should be in the range of 5-70 mm. However, the dimensions largely depend on the type of concrete. For example, the aggregate size for heavy concrete used for massive structures can be up to 150 mm.

If you choose between rubble and gravel, it is better to give preference to rubble, since different impurities are more often found in gravel. Crushed stone is obtained by artificial means, due to the crushing of rocks, so it is devoid of such disadvantages.

Tip! As a rule, in the construction used so strong concrete that its processing becomes a challenge. To solve it, diamond tools are used, in particular, cutting of reinforced concrete with diamond circles or grinding with diamond cups is often used.

Unlike gravel, grains of crushed stone have an angular shape, close to cubic. Thanks to roughness, such particles better adhere to cement. Therefore, to obtain high-strength concrete, only crushed stone is used.

To analyze the quality of coarse filler, it is necessary to determine its mineral and grain composition. In addition, attention should be paid to the degree of strength of the original rock. It must be 2 or at least 1.5 times the strength of concrete of the corresponding grade.

Note! The frost resistance of the entire concrete mass will depend on the frost resistance of the filler.

Special Fillers

As already mentioned above, some special aggregates of concrete are sometimes used, which allow to endow the material with certain properties. Next, take a look at the main types of such fillers.

Porous

Porous заполнители для легких бетонов по происхождению условно делятся на три вида:

• Natural (natural) origin;
• Artificially produced;
• By-products (industrial waste).

Natural materials include the following fillers:

• Puma - is a porous rock fibrous or spongy structure, which consists of volcanic sour glass;
• Volcanic slag - a large pore rock of a spongy or spongy structure.
• Volcanic tuff - is a finely porous rock consisting of ash and cemented volcanic glass.
• Carbonate rocks - These include shell limestone, porous limestone, calcareous tuffs, etc.

The following materials belong to artificial porous aggregates:

• Керемзит and its various varieties, such as shungizite, alumina clay, ash gravel, expanded thistle and argillite. It is produced by roasting with swelling of special granules from the ash-and-slag mixture, sandy-clay and clay rocks or fly ash.
• Agloporit - I get by firing with sintering the mixture of sandy-clay rocks, as well as processing and burning solid fuel (waste coal, ash TPP).
• Granulated slag - obtained by rapid cooling of slag melts.
• Вспученный перлит - formed as a result of burning and swelling of water-containing volcanic glasses, such as obsidian and perlite.
• Вспученный вермикулит, obtained by roasting and swelling of hydrated natural micas.

As for aggregates from industrial waste, these include:

• Fuel waste - obtained by chemical processing or combustion of anthracite, lignite and hard coal.
• Waste metallurgical slag - formed as a result of cooling molten metallurgical slags.
• Coarse fly ash and ash mixtures - obtained by burning solid fuels in a pulverized state.

Note! Lightweight concrete on porous aggregates according to GOST 32496-2013 must contain fractions of at least 5 mm in size and not more than 40 mm.

Thermal insulating fillers

In some cases, it is necessary to endow the concrete with thermal insulation properties, for example, when performing “warm” screeds.

In this case, ultra-light fillers are used, which include:

• Polystyrene - this component is a foam granules, which are added to the solution in the manufacture of concrete. I must say that this material is used even in the construction of supporting structures. Their insulating properties reduce the thickness of the walls.
• Sawdust - also have good thermal insulation properties and can significantly reduce the weight of the material.

Tip! Often, after pouring concrete, it becomes necessary to make holes in it. In this case, the most effective method of processing is diamond drilling of holes in concrete.

Additives

In addition to fillers, there are many additives in concrete, which are also able to give it certain properties or even change the structure.

These include:

• Flame retardants (borax, antimony, diammonium phosphate and others) - these substances under the influence of temperature melt and release gases that can resist burning. Such additives are used when it is necessary to endow the material with fire-fighting properties.
• Porozapolnitel for concrete - allows you to hide the pores of the concrete and thereby make it more moisture-resistant and durable. After processing the concrete surface with this composition, the properties of concrete become similar to granite. True, the sealer is not added to the solution, but applied to the frozen surface of concrete.
• Gas generators - allow you to change the structure of concrete and make it porous. As a rule, aluminum powder is used as a blowing agent, which reacts with alkali and releases gas, making the structure of concrete porous. Such additives are used in the manufacture of aerated concrete. I must say that the instructions for the manufacture of non-autoclaved aerated concrete is quite simple, so it can be made directly on the construction site.

Tip! You can use additives in the manufacture of concrete with your own hands, however, there are also ready-made mixtures for sale for certain purposes.

There are also additives that accelerate the hardening of the solution, make it more malleable, or provide some other features.

Conclusion

Fillers are an important component of concrete that can drastically change the properties of a material. Therefore, their choice must be approached very responsibly, given the properties that are required of concrete in a particular case.

From the video in this article, you can get more information on this topic.