Using refractory mortar for laying stoves and fireplaces

The selection of materials is essential for longevity and safety when constructing or maintaining stoves and fireplaces. Refractory mortar, which is made especially to withstand the high temperatures these structures face, is one of the most crucial components in this process.

The stove or fireplace will last longer and perform better if the proper mortar is used, too. Refractory mortar is designed to withstand repeated exposure to high heat without crumbling or cracking.

This post will discuss the advantages of refractory mortar, its differences from ordinary mortar, and application techniques to help you get the best results.

What is fireclay mortar

This substance is a mixture of aluminosilicates with refractory qualities, which enable it to tolerate temperatures as high as 1750 degrees. This product’s precise specifications are outlined in GOST number 6137-2015 (previously GOST 6137-97).

The mixture is primarily composed of refractory clay and fireclay in powder form. The material is mixed in equal parts, dried, and then crushed. The following fractions of powder are available for the products:

• Fine-grained (from 0.24 to 1 mm). The basis of such material is fireclay powder – 80-85% and clay – 15-20%.
• Medium-grained (from 1 to 2 mm). This composition contains 75–80% chamotte and 20–25% clay.
• Coarse-grained (from 2 mm to 2.8 mm). Such a mixture includes 70–75% powder and 25–30% additive.

The solution is a great choice for installing stoves, fireplaces, and their internal coating because of its fire and heat resistance as well as its ease of use. In the industrial sector, varieties that are especially resistant are used. The mortar is easier to transport and store thanks to its convenient release form and packaging, which comes in bags with varying capacities. The composition may lose its fundamental properties, so the primary need is that there be no excessive moisture present.

The dry material is diluted with the necessary amount of water and mixed to the desired consistency in order to prepare the mixture. A high-quality outcome depends on the technology being used correctly.

Both air-hardening and heat-hardening materials are possible. The latter option frequently calls for the addition of 8–10% liquid glass, which has already been diluted with water to a density of 1.36–1.40 g/cm 2. When a low-temperature mortar is being used and the furnace’s operating temperature is not higher than 1000 degrees, this additive is utilized.

Be aware of this! In order to ensure that the liquid glass solidifies before the heating structure ignites, a number of stove manufacturers claim that it should only be used with subpar mixtures. If such an ingredient is used in a composition with good properties and high furnace temperatures, bricks and masonry may burst.

Marking

Depending on the physical and chemical characteristics of the material, products are marked differently. For example, numbers indicate the percentage of aluminum oxide (Al2O3), while letters (MSh) indicate the name of the composition.

The most well-liked brands are:

The bauxite-based MShB-35 composition is particularly notable.

The amount of aluminum oxide in a solution determines the temperature it can withstand, so knowing its composition is essential. The mixture’s fire resistance increases with an increased indicator.

General technical characteristics and indicators

Technical specifications and broad indicators:

GOST 2211-65 is used to calculate the average density of Mortel.

It should be noted that choosing the "Terracotta" refractory mortar is a wise choice. This mixture is extremely plastic and heat-resistant, withstanding temperatures as high as 1780 degrees, because of special additives.

Instructions for using the mortar

This type of mortar blend is applied in accordance with the guidelines. Preparation is the first step in the process:

1. The work site is cleaned, all unnecessary things are removed.
2. The material and containers for mixing are prepared. The availability of the necessary inventory and tools is checked in advance.
3. The brick for masonry is cleaned of dust and dirt. If it has already been used, then the remains of old glue are carefully removed. It is recommended to clean off soot and carbon deposits.

It is important to take safety precautions before mixing the solution. Because the dry material suspension contains potentially harmful components, protective goggles, gloves, and a respirator are provided. Though drafts are not allowed, the space should have adequate ventilation.

How to prepare a mixture

It is important to understand that all mortar-related solutions fall into one of two categories before diluting the material with water:

• liquid – 13.5 liters of liquid per 20 kg of dry matter;
• semi-thick – 11.8 liters of purified water per 20 kg of powder;
• thick – no more than 8.5 liters per 20 kg of material.

Seams up to 3 mm thick can be created with the first two options, and seams thicker than 3 mm with the third.

There are two simple methods for preparing the solution using the technology.

Mixing a clean mixture

Foreign additives are not used in this instance. Work process:

1. Dry matter is poured into a container of the required size.
2. Pre-prepared water is poured in stages. It should not contain foreign inclusions.
3. A special mixer or drill with an attachment is used to mix the material. It is important to achieve homogeneity and the absence of lumps.
4. The mixture is left for 20–30 minutes, after which its consistency is determined. If necessary, the composition should be diluted to the desired state.
5. Everything is thoroughly mixed.

The process of mixing the mortar is far faster than with clay mortar.

Use of additives

A methylcellulose solution is added to the composition to create a mixture that solidifies in the air without the need for heat treatment. Another addition that keeps the seams from cracking is chamotte sand. One part mortar to two parts sand is the ratio used to prepare the composition. Using even tiny amounts of construction cement is a mistaken recommendation.

Similar to the previous iteration, the solution is prepared by thoroughly mixing all of the ingredients. There should be a creamy consistency to the composition.

Work procedure

Masonry is completed in accordance with the plan:

1. A drawing and a work plan are prepared. It is necessary to decide on the dimensions and shape in advance and purchase the necessary material. When choosing a fireclay mortar, take into account that the pure mixture can be used for a long period of time, and in the presence of additives this period is significantly reduced and can often be no more than 45 minutes.
2. The layout is done “dry”. The procedure is that the brick is laid without a binder material. This is necessary for grinding in, as well as determining the location of each element and the thickness of the seams.
3. Laying starts from the corner. It is very important that the brick is thoroughly wetted before applying the mortar. It must be sufficiently saturated with liquid, otherwise it will quickly take water out of the solution, which will lead to a violation of the seal and the appearance of cracks. The mixture is applied with a trowel and distributed evenly. It should fill the entire space after laying “brick on brick”.
4. The furnace is formed according to plan. The thickness of the seams depends on the future temperature: at high rates they should be the thinnest.

Refractory mortar is essential to the building of fireplaces and stoves. Your heating structures will continue to be secure and effective over time thanks to its resistance to high temperatures.

When used appropriately, this specialty mortar helps to preserve the overall heat efficiency of the stove or fireplace while also improving the brickwork’s durability. That’s why it’s a prudent investment for any high-heat installation project.

A fireplace that deteriorates quickly or one that lasts for years can be determined by the type of refractory mortar used. To guarantee the best outcomes, it is imperative to adhere to the proper preparation and application procedures.

Because refractory mortar can withstand the high temperatures produced by stoves and fireplaces, it helps to prevent cracks and damage over time, ensuring durability and safety. Because of its unique ability to withstand heat, this kind of mortar is essential to preserving the structural integrity of fireplaces and stoves as well as guaranteeing their safe and effective operation.

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