Construction of facilities for various purposes often requires the use of refractory materials. With their help, you can protect people and structures. One such material is refractory concrete. Some of its varieties are able to withstand temperatures up to 1000 ° C, while maintaining the shape and useful properties.
Basic Features
Among the main features of such concretes should be highlighted:
- high refractoriness;
- enhanced performance;
- strength;
- no need for an expensive firing process in production.
Today, refractory concrete can be classified by weight. You can make your own or order the following varieties of the described material:
- especially heavy;
- light;
- cellular;
- heavy.
As a result, it is possible to obtain a material that can perform a structural or thermal insulation function, depending on the ingredient composition.
Production Features
If you decide to make refractory concrete, you should become more familiar with its composition. The material is made on the basis of basic components and some additives, among which are:
- chamotte sand;
- magnesite;
- different types of rubble;
- aluminous cement.
Among the additives, finely ground and mineral substances should be distinguished, which give the material strength. These additives include:
- pumice;
- finely ground chromite ore;
- blast furnace slag.
These components are added to increase the density of not only the finished product, but also the dry composition. Sometimes aggregates for production are made in a factory, but in some cases refractory rocks and fired refractory bricks may be used. To obtain different grades of concrete, aggregates of different fractions are added. If we are talking about a coarse-grained substance, then its elements can have a diameter ranging from 5 to 25 mm. When it comes to the fine fraction, it is equal to the limit of 0, 15 and 5 mm. Among these ingredients should be highlighted:
- magnesite brick;
- chamotte brick;
- combat of an ordinary brick;
- aluminous slag;
- diabase;
- bas alt;
- blast furnace slag.
The most common among consumers is refractory concrete, which is made using fireclay, because it meets all building needs. As a linkaluminophosphate ingredients and liquid glass act. Portland cements, periclase and aluminous cements act as binders. If liquid glass is added to the ingredients, then it allows you to increase performance. This is especially true if a concrete mortar is used to form a plaster layer.
Additional technology recommendations
Refractory concrete, the composition of which is described in the article, may have a certain brand. Each variety involves the addition of its own plasticizer, magnesite powders and ferrochrome slags. If there is a goal to prepare lightweight concrete, then expanded materials should be used by type:
- vermiculite;
- expanded clay;
- perlite.
If you decide to order the manufacture of the mixture from a professional, then they will select the ratio of the components themselves, in accordance with your project. The composition is selected according to the operating temperature and service conditions.
Additionally about the composition by type of filler
If you decide to make refractory concrete with your own hands, then you can use different aggregates, namely:
- dinas;
- corundum;
- quartz;
- ready mixes.
Considering concretes by composition, grades should be distinguished. For example, ASBG is a refractory dry aluminum-containing mixture, which is used in non-ferrous and ferrous metallurgy, andas well as thermal power. High-alumina concrete mix with refractory characteristics is abbreviated as VGBS and is intended to create a monolithic lining of steel-pouring ladles, walls and when constructing a bottom.
Such a composition can be operated at temperatures up to 1800 ° C. Reinforcing dry high-alumina mixture is designated by the letters SSBA. It is intended for thermal units, furnaces, as well as for the installation of a reinforcing layer. The operating temperature can reach up to 750 °C.
Concrete drying
Drying of refractory concrete can be carried out after completion of the curing step. Air is used here, and the ambient temperature must not fall below +10 °C. Before initial heating, the concrete should be cured for a day or more to achieve a stable state. The drying operation reduces the amount of free water in the concrete that could cause a chemical reaction between the atmosphere and the surface of the lining.
After hardening, the lining is left in moist air without drying. After curing is complete, dry the lining. If this is not possible, then the concrete is left in a closed damp environment. It is important to ensure good ventilation or leave the lining in a well ventilated area. If you wondered how to make refractory concrete, then you should also be familiar with the features of its preparation for operation. For example, the drying step may be carried out using a suitable fan or blower whichwill blow hot air.
Features of kneading
Before you make refractory concrete with your own hands, the composition of the solution must be very carefully selected. This was mentioned above. As for the features of mixing, it is recommended to use a paddle mixer for this. It is preferable for heat-insulating concretes, but for dense mortars it is completely necessary, as it allows you to evenly and correctly mix the material with the addition of a smaller volume of water. As for the concrete mixer, this effect will be very difficult to achieve.
This recommendation is also relevant for the reason that for dense concrete, the moisture content may be critical. Indeed, for the materials described, maximum strength is required along with optimal density. By their nature, insulating concretes are softer than dense ones, so it is important that they are mixed using the correct amount of water. Its excess can cause a decrease in strength and density, while a lack of it will lead to a decrease in fluidity.
Proportions of refractory concrete
Preparation of refractory concrete must be carried out in compliance with certain proportions. If it is planned to build a fireplace using the material, then the mortar after hardening will have to withstand temperatures in the range of 1200 ° C. From the mixture you can make a fireplace and a firebox. To carry out the work, you will need 1 part of concrete grade M-400, 2 parts of sand fromrefractory bricks, the same number of pieces of crushed brick, as well as 0.33 parts of powdered fireclay additives.
If you plan to build a monolithic hearth, then during the operation of the heating equipment it will constantly be exposed to an open flame. To do this, it is required to prepare a solution with the following proportions: 2.5 parts of crushed stone, part of concrete, 0.33 parts of fireclay sand. As for crushed stone, it can be made of quartz or red bricks, as an alternative solution, finely ground red bricks are sometimes used.
Conclusion
Features of preparing a mortar for creating refractory concrete are similar to those used when mixing conventional cement mortar. If it is supposed to carry out pouring into the formwork, then the movement should be directed clockwise. Sometimes plywood molds are used to form products.
In order to prevent water evaporation during the hardening process, molds should be compacted after production. This contributes to easier extraction of castings. The easiest way to seal is polyethylene, but in order to achieve the best result, silicone should be used, which is pre-lubricated with vegetable fat.
