The construction of facilities for various purposes quite often requires the use of refractory materials. With their help, you can protect people and structures. Refractory concrete acts as one of these materials. Some of its varieties are able to undergo temperatures up to 1000 ° C, while the shape and useful properties are preserved.
Basic properties
Among the main features of such concrete should be highlighted:
- high fire resistance;
- increased operational properties;
- strength;
- no need to use an expensive firing process in production.
Today, refractory concrete can be classified by weight. You can make it yourself or order the following varieties of the described material:
- especially severe;
- light
- cellular;
- heavy.
As a result, it is possible to obtain a material that can perform a structural or heat-insulating function, which depends on the ingredient composition.
Manufacturing Features
If you decide to make refractory concrete, then you should familiarize yourself with its composition. The material is based on basic components and some additives, among which are:
- fireclay sand;
- magnesite;
- different types of rubble ;
- alumina cement.
Among the additives, it is worth highlighting still finely ground and mineral substances that give the material strength. Among these additives are:
- pumice;
- finely chopped 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 the factory, but in some cases refractory rocks and fired bricks can be used. To obtain different grades of concrete, aggregates of different fractions are added. If we are talking about coarse-grained substance, then its elements can have a diameter in the range 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;
- fireclay bricks;
- ordinary brick battle;
- alumina slag;
- diabase;
- basalt;
- dump blast furnace slag.
The most common among consumers is refractory concrete, which is made using fireclay, because it meets all the needs of construction. Alumophosphate ingredients and liquid glass act as a link. Portland cement, periclase and alumina cements also act as binders. If liquid glass is added to the ingredients, then it can improve performance. This is especially true if concrete mortar is used to form the 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 plasticizer, magnesite powders and ferrochrome slag. If there is a goal to prepare lightweight concrete, then expanded materials should be used according to the type:
- vermiculite;
- expanded clay;
- perlite.
If you decide to order the production of a mixture from a professional, then they will choose the ratio of the components themselves, in accordance with your project. The composition is selected according to operating temperature and service conditions.
Additionally, composition by type of aggregate
If you decide to make refractory concrete with your own hands, then you can use different aggregates, namely:
- dinas;
- corundum;
- quartz;
- ready mixes.
Considering the concrete composition, it is necessary to highlight the brand. For example, ASBG is a refractory dry aluminum-containing mixture that is used in non-ferrous and ferrous metallurgy, as well as in power engineering. High-alumina concrete mix with refractory characteristics is designated by the abbreviation VGBS and is intended to create a monolithic lining of steel pouring ladles, walls and when installing the bottom.
Such a composition can be operated at temperatures up to 1800 ° C. Reinforcing dry high alumina mixture is indicated by the letters SSBA. It is intended for thermal units, furnaces, as well as the device of the reinforcing layer. Exposed temperature can reach 750 ° C.
Concrete drying
Refractory concrete can be dried after the completion of the curing step. It uses air, and the ambient temperature should not be lower than +10 ° C. Before the initial heating, the concrete should be aged for a day or more to achieve a steady state. The drying operation reduces the amount of free water in the concrete, which could cause a chemical reaction between the atmosphere and the surface of the lining.
After curing, the lining is left in moist air without drying. After curing is complete, the lining should be dried. If this is not possible, then the concrete is left in a closed, humid environment. It is important to provide good ventilation or to 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 that will supply hot air.
Kneading Features
Before you make refractory concrete with your own hands, the composition of the solution must be very carefully selected. This was stated above. As for the features of kneading, it is recommended to use a paddle mixer for this . It is preferable for heat-insulating concrete, but for solid solutions it is absolutely 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, it will be very difficult to achieve this effect.
This recommendation is also valid for the reason that for dense concrete, the moisture content may be critical. Indeed, for the described materials, maximum strength is required along with optimal density. By their nature, heat-insulating concrete is softer than dense, so it is important that they are mixed using the required amount of water. Its excess can cause a decrease in strength and density, while a lack will result in a decrease in fluidity.
Proportions of Refractory Concrete
The preparation of refractory concrete must be carried out in compliance with certain proportions. If using a material it is planned to erect a fireplace, then the solution after hardening will have to withstand temperatures within 1200 ° C. From the mixture you can make a fireplace and firebox. For work, you will need 1 part of concrete of the M-400 brand, 2 parts of sand from refractory bricks, the same number of pieces of crumb from brick bricks, as well as 0.33 parts of a dusty fireclay additive.
If you plan to build a monolithic hearth, then during the operation of heating equipment an open flame will constantly affect it. To do this, you need 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 brick, as an alternative solution thin-ground red brick is sometimes used.
Conclusion
Features of the preparation of the mortar for creating refractory concrete are similar to those used in the mixing of ordinary cement mortar. If it is intended to be cast into the formwork, then the movement should be clockwise. Sometimes for the formation of products used forms of plywood.
In order to prevent the evaporation of water during the hardening process, the molds after manufacturing should be sealed. This contributes to easier extraction of castings. The easiest way to seal is polyethylene, but in order to achieve a better result, you should use silicone, which is pre-lubricated with vegetable fat.