Clay for laying ovens

Qualitative clay for laying furnaces is one of the most important conditions for the reliability and durability of a future heating plant. Clay can be purchased in a specialized store or produced by hand. But in any case, it is necessary not only to be able to select it correctly, but also to prepare appropriately for masonry work.

There are many different types of clay, and not all of them are suitable for masonry stoves. Therefore, it is worthwhile to understand what this substance consists of, what qualities it should possess, so that it can be used for construction of this kind.

What is clay?

It would seem a ridiculous question - each of us has known this natural fossil since childhood. Nevertheless, not everyone knows the component composition of clay and its specific properties used in construction practice.

Composition of clay

Mineral constituents of clay may vary in their percentage composition, but in all its types, substances from such groups as montmorillonites and kaolinites or other layered aluminosilicates are necessarily present. This kind of natural material contains various impurities in the form of sand and carbonate particles, but its main composition is aluminum oxide - up to 39%, kaolinite - about 47% and water 14%.

In many ways the composition of clay depends on the method and place of its formation. So, residual and sedimentary clays are allocated.

• Residual clays are formed by weathering of mountain non-plastic rocks and converting them into plastic kaolins.
• Sedimentary clays are formed as a result of the transfer of the weathered natural products and their settling in a certain place. These can be clays formed on the oceanic, sea or river bottom, as well as on the continental part. Sea rocks are divided, in turn, into coastal, lagoonal and shelf.

Clay is not a rare mineral substance, and is widely distributed around the planet. You can find it almost everywhere, so clay can not be called an expensive material.

Basic properties of clay

Clay is a microgranular substance, and irrespective of the place of its formation, it differs in its characteristics from other natural minerals. Due to its properties, it can be used not only in construction, but also in other areas of human life.

• Clay quickly absorbs moisture and under its influence swells, while acquiring water resistance, that is, the ability not to let water pass.
• The second, no less important positive quality of the mineral is its plasticity, due to which it can take any forms.
• Upon drying, the clay acquires high strength. Due to this quality and water resistance, it is often used to equip the floors in basements or locks around such as wells or the foundation of a house.
• In addition, very important qualities of this material are high adhesion of the solution and its gas density.

Depending on the proportions of ingredients in the composition of clay, it may have a different degree of fatness. Or rather, it is skinny, normal fat and very oily.

Clay for masonry

Clay for stove laying, already cleaned and shredded can be purchased at a specialized store, and used for mortar preparation. In this case, it should be borne in mind that for the masonry of a total of 100 bricks having a standard size of 250 × 120 × 65 mm and laid flat or on a "bed", 20 liters of solution will be needed, which is placed in two buckets.

The construction of the entire furnace, depending on its size and model, may require from 550 to 2500 pieces of bricks, not taking into account the masonry of the chimney and the foundation. Therefore, by calculating the cost of the required amount of all materials, it is possible to think about how to save at least on clay and sand for mortar, especially since they can be found literally under your feet when you leave the country.

If it is decided to conduct this simple process of preparing such materials on its own, then certainly some questions arise:

• Where can one dig up clay and find sand, thereby saving a fairly significant amount?
• How can I determine the quality of the material and its suitability for the furnace solution?
• How correctly to make a solution, proceeding from that fat content of clay which it was possible to find?
• How to prepare the constituents for the solution?
• How to make the right kneading?
• What components are needed for a solution other than clay?

These questions can easily be found uncomplicated answers. And start standing in order.

How to find and pick up clay?

Clay is usually easy to find near any suburban area. The layers of this mineral are not too deep, but each of them can have different composition. Such layers can be well seen on the steep banks of rivers or the sea, as well as on career developments. It is there that you can see that numerous layers have different shades and density.

It should be noted that even in one place each of the layers, depending on the composition, can have different fat content, therefore, when selecting the right material, it is recommended to take samples from several layers. It should be borne in mind that the higher the layer lies to the surface, the clay is fatter. Therefore, it makes sense to immediately check the middle layers, because in them the mineral should have the most optimal fat content.

In the lower layers usually there is a thin clay, and if you dig it, the solution will have to be "burned", adding a very greasy clay. It is much easier to correct a very greasy composition - it can be brought to a normal state by adding sand.

Mortar with normal fat clay has good plasticity, since the balance of its constituents is observed in it. When the masonry dries, these mixtures practically do not crack and do not shrink. Well, and that's also very important - it's much easier to work with them.

Fatty solutions in the wet form are very plastic, and they are also convenient to work with, but when moisture evaporates from them, they begin to crack and disintegrate into large fragments. Therefore, such clay does not give clutch reliability and durability.

Lean clay rocks are not recommended for stove solutions, they are not plastic and do not give a masonry of the fortress.

Video: Experienced stoveman shares the secrets of mining quality clay

Determination of the fat content of clay by the skilled way

If the clay is mined independently, its fat content can be determined immediately at the site of the excavation. To do this, you need to take a handful of mineral in your hand, moisten it with water and mash it to a uniform state. Organoleptically, by touch, you can feel how fat the clay is high. If it becomes sticky and plastic, like plasticine, then it's a fatty breed. The same clay, crushed into a ball and moistened with water, will still crumble. This version of the material will have to be "burned".

There are several more accurate tests of fatness of this material, and they must be used to select the optimal version of clay.

First method

It is necessary to take about 0.5 kg of clay, which is diluted with 100 ÷ 130 ml.water. The mass is mixed until uniform. It is better to carry out this procedure manually, so that, as they say, it is tactile to feel the uniformity of the composition, which at the end of mixing should not stick to the hands and have the consistency of plasticine.

From the resulting mass you need to roll two balls, having a diameter of 40 ÷ 50 mm. One of them remains intact, the other - crumples into a flat cake. These prototypes are allowed to dry for two to three days at room temperature.

If cracks appear on the prepared parts after curing, this indicates that the clay is very greasy, and it is necessary to add a little more sand to it when kneading the solution than indicated in the recipe.

If the cracks are insignificant, and the ball, thrown on the table from a height of 800 ÷ 1000 mm, is not split into parts, the clay has a normal fat content, this sort is excellent for masonry mortar.

Second method

For testing the clay in the second way, 2 ÷ 2.5 kg of clay is required, which is kneaded with a vat, adding water. To bring the mass to the consistency of plasticine, and if it still continues to stick to the wooden veselka, then the clay is very fatty. When kneading a solution, more sand is added to it than required according to the recipe.

Clay, which has a normal fat content, remains on the vesel with separate clots, but does not adhere to it completely.

The third way

This way to check the clay for fat content is considered the most accurate. To carry out the test, take 0.5 kg of clay, which is kneaded with water until the state of a thick dough. Further, a ball is rolled from the resulting mass, with a diameter of 40 ÷ 50 mm. Then, the ball is compressed between two smooth planks until clays appear on the clay. In this case, the fat content is determined by the thickness of the flat cake and the appearance of the cracks.

• If the clay is low in fat or lean, then even with a slight compression, the ball will break apart.
• If the clay is very greasy, then when compressed at half the original diameter, narrow cracks are formed.
• If, when the ball is squeezed by ⅓ from its original diameter, cracks appear on the clay, it has a normal fat content, and is well suited for masonry work.

In this figure, you can see the ways of testing clay for fat content:

1 - Determination of the plasticity of the mineral:

a) lean clay with low ductility;

b) Normal clay has an average plasticity;

c) greasy clay, plasticity is high.

2 - Determination of plasticity by the "ball" method:

a) the thin clay ball is compressed 1/5 ÷ 1/4 of the diameter;

b) a ball of normal clay is compressed to ½ of its original size.

3 - Determination of fatiness by the "flagellum" method:

on the left, the tensile tensile method -

a) lean;B) the normal;C) fatty.

4 - Right - the method of bending around the rolling pin:

a) lean;B) the normal;C) fatty.

During the tests, you can immediately adjust the resulting mass, adding to the lean solution of fatty clay, and in the greasy mixture - sand. If the correction will occur in small portions, then the proportions should be immediately recorded, and then, selecting the best option, use the data to mix a large amount of material for masonry work.

Cleaning clay

After carrying out the experimental measures and leaving the clay elements to dry, you can proceed to cleaning the clay from the pebbles, plant roots and other impregnations that will interfere with normal work and reduce the quality of the joints of the masonry.

Cleaning of clay can take place in two ways:

1. Grinding and sifting of clay through a metal sieve, which must have cells no larger than 3 mm. Dry clay is poorly crushed, so the whole process will take quite a long time.

2. If another cleaning method is chosen - "wet", then before it is carried out, the clay should be soaked and wait until it swells and becomes soft. Then, the resulting solution is wiped through a sieve with a 3-mm-thick mesh net, through which it is convenient to wipe a clay mortar of medium density.

Soaking clay

Before cleaning with a "wet" method, the clay should be soaked. It should be noted immediately that the dry-cleaned clay is soaked in exactly the same way before kneading the solution.

Dry cleaned or unpurified clay is poured into the container. Usually, old baths are used for this, or wooden boxes are made, then they are clamped with metal roofing sheets. In order for the clay to blend well, and it was easier to mix, it is covered with layers of 120-150 mm, each of which is spilled with water and mixed. The top layer is poured with water so that it covers the mixed clay.

The soaked clay is left in this form to swell for a period of 14 hours to 24 hours. During this time, it can be periodically mixed with a shovel, adding water if necessary.

Then, the whole mass is mixed, water is added to it, and it is left again for 14 ÷ 24 hours. At the end of this period, the composition is once again mixed, and if it is made of mashed clay, it can immediately be used to prepare a masonry mortar. If the unrefined clay was soaked, it is passed through a sieve into the prepared container.

Chamotte clay

For some sections of the furnace, which will be discussed below, chamotte clay is used for masonry. This clay in the finished form is unlikely to be found independently, as it is produced using a special technology consisting of several stages:

• The usual soaked clay enriched with various additives is briquetted and dried.
• Next, the firing phase is taking place - this process takes place at a temperature of 1200 ÷ 1500 ° C.
• The burnt briquettes are ground to a state of flour for the production of chamotte clay, and to a coarse-grained fraction - to produce sand.

Due to the fact that the fireclay material undergoes high-temperature firing, it is refractory and capable of withstanding temperatures over 1800 ° C.

Chamotte clay has highly dispersed hydroaluminosilicates. During the manufacturing process, this material, due to sintering and firing, acquires the following characteristics:

• Hygroscopicity is an average of no more than 7.8% of the total volume of clay.
• Humidity content - not more than 5%.
• Refractoriness reaches 1530 ÷ 1830 ° C.
• The size of the fraction is from 0.005 ÷ 0.01 mm.

Special qualities of chamotte clay give the solution on its basis a high plasticity, and when dried, it acquires the strength of the stone.

The manufacture of a mortar made of this material will not cause any difficulties, since in its dry state it is, in fact, ordinary clay, but already ground and purified. Therefore, it is pleasant to work with such clay, and the kneading process consists of the following steps:

• Clay powder is poured into a prepared container, for example, a 10 liter bucket. Then a small amount of water is poured into the clay and mixed well to a uniform state. If necessary, a little more water can be added to the solution, and then it should be left for 2.5 ÷ 3 days for swelling.
• After this period, water is added to the solution, and it is well mixed, the mass should have a consistency of thick sour cream. It should be noted that when making this solution, it is not terrible to pour water into it, since it is easily corrected by falling asleep into the resulting mass of a small amount of dry clay.

In addition to the usual chamotte clay, in specialized stores you can find ready-made instant preparations that are kneaded just before the work of masonry. Using such construction mixtures, you do not have to wait for three days until the clay swells.

What solutions are needed for the furnace?

Not all starters know that not one, but several solutions are used for laying the furnace, because different sections of the furnace have different heating temperatures.

are required for laying individual sections of the furnace. In the attached diagram, separate zones of the stove construction are defined, in which a different clay solution can be applied for masonry.

1 - The foundation of the furnace is arranged on the basis of a cement-sand mortar, but around it you can make a waterproofing layer, a kind of "lock" with a width of 100 ÷ 150 mm from clay, which must be well tampered.

2 - The foundation is covered with waterproofing from sheets of roofing material.

3 - The first two brick rows of the furnace are usually deposited on a cement-sand mortar. Sometimes a bit of lime is added to it for greater plasticity.

4 - Further, a sheet of asbestos or other heat resistant material is arranged with a heat insulation. The material is spread on a clay solution.

5 - The heat storage zone of the furnace is laid out on a clay-sand mortar, capable of withstanding a temperature of 500-600 degrees - this is precisely how this zone can be heated.

6 - The furnace furnace chamber is made of fireclay bricks, and a mudclay mortar is used for its laying, since the temperature in this area of ​​the heating plant can reach 1 thousand degrees.

7 - The masonry of the source of the chimney is made on clay-sand mortar. In this area, the furnace heats up to 300 ÷ 400 degrees.

8 - The flue of the chimney, located under the ceiling of the room, is laid out on a clay-sandy mortar.

9 - A metal box, arranged for fire safety around the pipe, can be filled with sand, expanded clay, vermiculite or the same clay-sand mortar.

10 - The neck of the chimney is laid out on a cement-sand mortar with the addition of clay.

11 - The pipe head exposed to atmospheric precipitation is usually laid out on a cement-sand mortar.

If solutions are manufactured independently and used in a complex, then you can save on their purchase up to 12-15%.

Making solutions using clay

In addition to the fact that it will be necessary to find, dig out and clean clay from impurities, it is necessary to know how to make furnace solutions correctly.

This table represents the materials that are used for laying ovens and the proportion of solutions.

solutions	Clay Types solution	mortar	Cement Materials used
solution	consumption of ingredients in parts by volume sand
	4	2,5	3-4
chamotte	1	-	-
usual clay	1	-	-
Lime	-	1	-
Cement M400	-	0,5	1

We will not dwell on cement-sand and lime mortar - they are not included in the contents of this publication. We are only interested in compositions based on clay.

Clay-sand mortar

As already clear from the above scheme, the "lion's share" of the heating plant areas is laid out on clay-sand mortar, which is why it can be called the main one in the construction of the furnace. The materials from which this mixture is made have a reasonably affordable price in specialized stores, but they can be mined on their own - in this case they will cost almost free.

is the most "hot" in the laying of the furnace. Despite the low cost, the clay-sand mortar has surprising properties, ideal for the construction of furnaces:

• Average density, which is very important for expanding it with heating.
• Heat resistance up to 400 degrees.
• Maximum gas density.
• High fire resistance.
• Clay mortar can be used for a second time, if it was not used for laying the combustion chamber.
• The mixture can be cooked with a margin, since its shelf life is unlimited. If moisture evaporates with time, it only needs to be diluted with water and mixed well.
• Environmental cleanliness of the material, which is important for use inside living quarters.

The disadvantages of clay-sand mortar can be attributed to its hygroscopicity, which means that it can not be used to fill the foundation and masonry of the upper part of the chimney located on the street.

As mentioned above, for the solution to be plastic, it served for a long time, and it was comfortable to work with it, it is necessary to choose the proportions of its components, which will depend on the fat content of the clay.

• In order to make the mass homogeneous, without lumps and impregnations, the clay swollen after soaking is well mixed with a construction mixer, shovel, or trampling.
• Stirring clay, injected sifted sand into it in previously defined proportions, and, if necessary, water is added.
• Readiness and plasticity of the solution is checked with a clean metal spatula, through which the captured mass should easily slide.
• It is also very important to ensure that the mixture has maximum adhesion. To test this quality, the mortar, a layer of 7 ÷ 8 mm, is applied to the brick on which the second brick is placed and pinned. At the same time, excess solution is squeezed out, which is immediately removed, and the seam should be about 5 mm.

Bricks are allowed to dry for 30 ÷ 40 minutes, after which it will be possible to check the quality of their adhesion. To do this, take the resulting "construction2 for the upper brick and raise it, that is, create conditions for the lower brick to be on weight. If the bottom brick is retained in the solution, the adhesion of the materials is considered optimal, that is, the solution has turned out to be of high quality and suitable for laying the furnace.

The consistency of the finished mortar can be checked by performing the following manipulations:

• In the prepared mass of the solution you need to lower the spatula soaked in water or a trowel. If the solution adheres to it, the mixture is very greasy, and it should be "sifted" by adding a small amount of sand. After this, all components are again mixed, and again the test is carried out. This is done until the desired consistency of the solution is reached.
• If water appears on the surface of the finished solution, manufactured in an ideal consistency and standing for some time without mixing, this means that the clay used in it has insufficient fat content. In this case, a small amount of clay having a high fat content should be added to the solution, and the resulting mixture should be well mixed again. In this case, the proportions used in the ingredients change, that is, the amount of sand decreases, and the solution becomes more greasy.
• If a spatula is lowered in a normal fat content and the mixture does not stick to it at all - this indicates that it lacks ductility, which means that you need to add some more fat clay to the mass.

Video: example of clay oven solution preparation

Clay-chamotte solution

As mentioned above, fireclay material has increased resistance to high temperatures reaching up to 1800 degrees, so solutions made with its use are used for laying a furnace where its permanentcontact with an open flame. In a solution mixed with chamotte sand, the main component is still clay, so its shelf life is also unlimited. Even a completely dried solution will "come alive" with the addition of water, and it will be ready for use.

The following materials can be used to mix the solution on which the walls of the combustion chamber will be laid:

• This can be chamotte clay, applied in pure form or with a small addition of sand.
• Normal white or gray clay of normal fat content.
• Too greasy ordinary clay can be "stuck", adding to it chamotte or quartz sand in proportions of 1: 1, or by matching the parts of the ingredients.
• If a model of a heating structure with a moderate heat load, such as, for example, a conventional cooker, a "Dutch" or a Russian stove, is chosen for the erection, then a conventional clay-sand mortar with a small addition of fireclay sand can be used for laying the furnace.
• For a furnace with increased heat load, the solution is made up of two components. It uses 70 ÷ 75% chamotte sand and 25 ÷ 30% of ordinary clay. Mix this mixture in the same way as the usual clay-sand mortar:

- The usual clay is cleaned and soaked for 2.5 ÷ 3 days.

- After that, the mixture is thoroughly mixed.

- Sand is gradually added to the agitated clay, and the mixture is brought to a homogeneous state and the desired consistency.

- When evaporation from any clay solution of moisture, it is updated by adding water.

When the furnace is built entirely of fireclay refractory brick, the best solution for its laying will be a mixture of chamotte sand and clay, or completely made of chamotte clay.

From all of the above we can conclude that with a "modest" budget, you can find the opportunity to save on the ingredients of the solution for the construction of the furnace. Of course, it will be easier to go to the store and buy everything you need in the finished form, but if you want to refrain from unnecessary costs, you can always find such an opportunity.