Refractory concrete: independent production of

Refractory concrete, as the name implies, is used where a structure can experience significant temperature loads. The properties of this material allow it to withstand heating to high temperatures without loss of strength, and therefore it is indispensable for arranging chimneys, laying furnaces, etc. And for conventional structures, fire resistance will not be superfluous.

Which groups are divided refractory concretes, what is included in their composition and how to prepare such a solution independently - we will tell in our article.

Material overview

Concrete and reinforced concrete in themselves are sufficiently durable and fire-resistant materials. This can be confirmed by a process such as diamond drilling of holes in concrete: even with considerable heating from friction, the frozen solution does not melt and does not lose its properties.

However, the low thermal conductivity of concrete "works" only during short-term heating. If by prolonged exposure to bring the design to 250 ⁰With, it will begin to collapse, and at 200 ⁰C - lose its strength by 25-30%. This can lead to the saddest consequences, and therefore in some cases it is recommended to use fire-resistant and heat-resistant compounds.

By their properties, concretes are divided into several groups. Their brief characteristics can be seen in the table:

Note! Heat-resistant and fire-resistant compositions with a density of less than 1500 kg / m³ attributed to the category of lightweight concrete.

The instruction recommends the use of such materials wherever the structure is subjected to periodic or permanent exposure to high temperatures. Also, the use of heat-resistant mixtures is justified if the destruction of the supporting elements in a fire can lead to tragic consequences (bearing bases of workshops, residential and public buildings, etc.).

Manufacturing method

Features of the composition

For laying stoves and fireplaces, arranging chimneys and solving similar problems, we may need a material that can withstand heating up to 1000 - 1200 without loss of strength ⁰C. The price of ready-made factory mixes is quite high, so you can try to make the solution yourself.

To understand what substances should be added as modifiers, it is worth figuring out what happens to hardened cement during combustion:

• As you know, for the hardening of cement in concrete is largely responsible water, which reacts with the granules of the material.
• When the temperature rises, most of the liquid evaporates, dehydration of the cement occurs, and it loses its strength.
• This process is irreversible, because to restore the properties of the material at least partially fail.

Therefore, to avoid the destruction of concrete, we need to keep water inside by adding binders.

In this role usually act:

• Portlandcement / Slipboat cement.
• Periclase cement.
• High alumina cement.
• Liquid glass.

In addition, to improve the heat resistance of the material injected finely ground additives:

• Combat brick (magnesite, dolomite, fireclay).
• Pemzz
• Chromite ores.
• Blast furnace slag (ground and granulated).
• Керемзит.
• Золу.

As a filler, fragments of refractory brick, blast furnace slag and fragments of solid rocks are also used: diabase, basalt, tuff, etc. Light fire resistant solutions are made on perlite or vermiculite.

Note! The filling of crushed gravel from dense rocks makes it almost impossible to process frozen solution. So, if necessary, cutting of reinforced concrete with diamond wheels or drilling using similar tools is used.

Independent production

To make fireproof concrete mixes yourself is quite possible.

To ensure acceptable quality, it is worthwhile to act according to the following algorithm:

• In a concrete mixer we mix three parts of gravel (crushed basalt or tuff), two parts of sand, two parts of refractory cement and half a part of lime.

• To improve the heat resistance, you can make 0.25 parts of finely ground substances - ash, blast furnace slag or pumice.
• Add water in small portions, bringing the solution to the optimum consistency.

Next we need to perform the fill. Concrete intended for use at high temperatures can either be poured directly into the formwork at the facility, or molded into separate blocks.

In any case, we act like this:

• From plywood, plastic or metal, we make sufficiently solid formwork.
• Fill the formwork solution, trying not to make passes and voids.
• Thoroughly seal the material, removing all air bubbles.

Note! Prolonged vibration treatment leads to the fact that the gravel aggregate settles to the bottom of the formwork. That is why it is necessary to condense the solution for a very short time.

Remove excess mortar with a trowel.

After that go to the drying of the material:

• Fire-resistant concretes are more sensitive to the hydration regime. The presence in their composition of lime allows for a long time to maintain a high temperature inside the mixture, which ensures effective curing of concrete products.
• So that this process does not slow down, it is necessary to carefully cover the formwork, minimizing heat loss and reducing the rate of evaporation of water.

In principle, the technology allows you to dismantle the formwork immediately after cooling the mixture. However, to ensure maximum mechanical characteristics, experts recommend keeping the solution in the form of at least three days, and after dismantling it, moisten all surfaces for another three or four days in a row.

Conclusion

If we are talking about small volumes (for example, for erecting a chimney or laying a fireplace), then everyone can do fire-resistant concrete with their own hands. To master the technique it will be enough to purchase the necessary components, as well as follow the tips given in the video in this article.