How to make your own mortar for masonry
If you are going to build an oven with your own hands, you need to think about the right materials for it. Many people know that masonry requires refractory bricks. But it is not enough to purchase this material, it is also necessary to correctly select and prepare the mortar for laying a brick oven.
The mortar on which you can put refractory bricks in the construction of the furnace, necessarily include clay. There are two ways to prepare the “right” mortar for masonry brick stove:
- Purchase ready-made clay or ready-made mix in a construction store;
- Prepare the mixture with your own hands, carefully observing the proportions.
How to make a mortar for masonry brick oven with your own hands? You should start with the preparation of clay. This advice applies to areas where you can get clay yourself. If this is not possible, you will have to buy it in the store.
If you have clay, you will have an oven
As a rule, clay is almost everywhere. Especially often you can find good clay on the slopes of ravines or on the banks of rivers. When laying underground utilities in cities you can also find clay. If there is a similar kind of work in your neighborhood, take advantage of it. The clay lies just under the top layer of soil. It is enough to dig the top layer to a depth of only 0.5 m. It is necessary to know that in different places there are different types and composition of clay. There are greasy and lean clays. Using them in the mortar for masonry furnace is possible only in a certain proportion.
Our note: there is no specific proportion for furnace mortar. The ratio of clay. sand. water is selected experimentally.
Fat or thin?
Using a fat solution in masonry furnace with their own hands will lead to the fact that, drying out, it will significantly decrease in volume and cracking will occur. Thin mortar after drying will begin to crumble. In both cases the penetration of carbon monoxide into the room is ensured. Thus, the “correct” composition of the mortar for masonry brick oven directly depends on the fat content of clay.
Clay for mortar. determine the fatness
If you are not a professional stovemaker, able to determine the greasiness of clay by touch, you will benefit from ways to determine its greasiness:
- Take a small amount of clay, a liter jar will be enough, and cleared of large particles.
- Divide the clay into five equal parts. No sand is added to the first part. In the second part they add a quarter of the sand. In the third one, half of the sand, in the fourth one, a whole part, and in the fifth one, one and a half parts.
- After that each part is mixed with water until a plastic mass is formed. The clay should knead well, but should not stick to your fingers.
- After that, balls are formed of all parts and pressed into small cakes. The tortillas are left to dry. The most important thing is that you know exactly how much sand is in each piece.
- After the tortillas have dried, you can easily determine the optimal proportions of clay. sand. If the composition does not contain enough sand, the cakes will crack. If there is a lot of sand, no cracks will be formed, but such tortilla will crumble.
- The most normal ratio will be that composition, in which the scone will be dense and without cracks, that is how a quality mortar for the oven should be.
- Prepare the balls as in the first variant.
- Take two well-sawn boards, and between them put a ball of clay mortar.
- After that it is necessary to press on the upper board.
- If the mortar is greasy, the ball will only crack at half the compression of the outside diameter.
- At normal composition cracking will occur at one-third of the diameter of the crumpling.
- A ball of lean mortar crumbles almost immediately after being pressed.
Clean clay. successful work
To prepare a quality mortar for the stove, the clay must necessarily be sifted to remove large impurities. A sieve with a mesh of 3X3 mm is used for this. Why this size? As you know, when masonry brick oven, the smaller the thickness of the joint, the better. The seam thickness of 3 mm is considered optimal. Therefore, a larger sieve will leave larger particles that will interfere with bricklaying. But the best option for cleaning clay with your own hands is the lathering method. The mortar thus obtained does not have large foreign particles, and the masonry is much better and more pleasant. How to prepare such a mortar for masonry with your own hands? This is done as follows:
- Take an oblong container. You can use an old child’s trough.
- A trough should be placed with a 5-7º slope.
- Pour the clay into the upper part, and water into the lower part. The amount of clay and water should be such that they do not touch each other.
- Use an ordinary trowel or a small trowel to begin pushing the water onto the clay. This continues until the clay is mixed with the water.
- The clay thus obtained shall be strained into a separate container.
- The operation is repeated until the required quantity of clay is obtained.
If you do not soak it, you will not work
Dry purified clay should be soaked before use.
The clay is poured into the container with a thickness of 100. 200 mm, the surface is smoothed and poured with water. Make sure that the water level covers the clay. Another layer is poured on top and again poured with water. And in this way all the necessary clay is soaked. After one day the clay should be well mixed with a shovel and, if necessary, adding water, leave it for another day.
How to Lay Bricks Part 2: Mixing The Mortar
Lime and cement mortar for the stove
This mixture for masonry furnace is widely used in the construction process with their own hands. It consists of cement, sand and water. This composition is used in the manufacture of foundations (especially in places with high humidity). It is used in masonry chimney pipes over the roof of the building. This composition tends to harden in the air and in the water. It sets after 30 minutes and becomes fully cured after 12 hours. The mixture for the furnace is easy to prepare with their own hands, by mixing sand and cement in the proportion from 1:1 to 1:6. It should be used within one hour, in which case the quality of strength is preserved. You can buy ready-made dry mixes to perform the above work.
Lime mixture is easy to make, it is not difficult to prepare your own hands. The quality of the prepared mixture depends on how the lime is extinguished. Pour water into the preparation tank, and then wait until it stops boiling (this passes the process of quenching). Preparation of the mortar with their own hands includes several steps:
- Determine the required volume of the product, excess product is not stored for a long time.
- Sift the lime thoroughly. Take out all the stones, you should get a fine fraction. Wear rubber gloves (corrodes hands).
Attention: the lime must be completely fine. Keep coarse particles out of mixtures. In the process of drying, it will start to “shoot” and thus spoil all the work done.
- Mix the mixture with a trowel or drill with a nozzle until it becomes a thick sour cream. If the mixture is too viscous, add some dry mass.
- When plastering stoves, you can add a little gypsum or cement, this will increase the strength of the attachment. The same mixture is used for stove plastering.
- Prepared stove masonry mixes should be stirred in the process, otherwise they will harden quickly.
Dry mixes for stoves are used at all stages of the work, from the initial stage to the lining of the stove.
Water. Must be perfectly clean, with no musty odors, and, importantly, it must contain a minimum amount of mineral salts. If you have problems with clean water, the column does not work or well water contains a lot of dirt, take care of the stock of water in advance. The calculation is simple: on average, a little more than a bucket and a half of water will be needed for laying 100 bricks. (15 to 20 liters).
Sand. Work only with fine sand, which should be carefully sifted. For that we need a sieve. It is convenient to sift fine and clean sand through a fine mesh sieve (one and a half millimeters).
Main component. clay. First of all, we are interested in its adhesive properties, its fatness. From this will depend on the amount of sand, which we will add to the mortar, in detail, we will consider it in the next paragraph.
Source materials for kiln mortar
A few words should be said about the materials that are used to make masonry mortars for stoves, because they, too, must be chosen with knowledge. These materials include chamotte and quartz sand, clay, lime and cement.
Chamotte is a refractory clay that has undergone a high-temperature firing process in which the moisture has been completely removed from it and the material has been brought to a sintering state.
Chamotte sand is made from burnt fireclay bricks crushed by crushing. This material makes the mortar more resistant to high temperatures, so it is often used instead of sand or as an additive to the mixture intended for the furnace chamber, which, accordingly, is lined with heat-resistant fireclay bricks.
Chamotte sand will not need too much, so do not save on it. It can be purchased in ready-made form in specialized stores.
Clay is a microgranular mineral that has a number of advantages, such as plasticity, strength, water resistance, high adhesion, gas tightness. All of these properties can be reduced to one quality: fat content, since it is by that quality that the material is selected. For making stove masonry mortar, clay of medium fatness is ideal. If the mineral is too greasy, when the moisture evaporates from it, the surface will crack to a fine grid. Well, when using lean clay, the solution will not have the proper plasticity and reliability.
How to Prepare Mortar | Masonry
You can look for quality clay in open pits or on steep riverbanks
Clay can easily be found around the countryside, as it is usually widespread in any area. The good material usually lies at a fairly great depth, so it is better to look for it on the steep riverbanks or in quarries, where you can see her numerous bare layers.
Choice of clay by fatness
In layers of clay, which has different compositions, so in the same quarry or on the precipice can be a mineral with different fatness. In this regard, when selecting material for making masonry mortar, it is necessary to take samples from several layers, guided by the fact that the higher the layer is, the fatter the clay in it.
Nevertheless, if too fat or lean clay has been found or purchased, its composition can be adjusted. For example, a greasy mineral can be brought to the desired condition by adding a little more sand, and the leaner one is mixed with greasier clay, bought in small quantities especially for this purpose.
The fatness of the clay can be determined immediately in the place where it is found. To do this, take a handful of dry minerals, soaked in water and kneaded to a plastic state. Already in your hand, you can feel how greasy the material is, so if the clay takes the consistency of plasticine, this means that the material is greasy. If after wetting and kneading the lump continues to crumble, it means that the clay is lean, and it will have to be heated.
You can check the quality of clay at home, and these results will be more reliable than the findings after conventional compression of the lump of mineral in your hand. For such a control there are several ways:
- Take 0,5 l of clay and add 100÷150 ml of water. Then the mass is carefully kneaded with your hands until it becomes homogenous and does not stick to your hands. From the resulting “dough” roll two balls with a diameter of 45÷50 mm, and one of them is crumpled into a cake. Then they are dried in room conditions for two to three days.
If after this time, cracks appear on the experimental samples, it means that the clay is too greasy and it is necessary to add a little more sand than indicated in the recipe for making mortar.
If no cracks are found, and the ball thrown to the floor from a height of one meter does not break into pieces, then the clay is suitable for masonry mortar.
- The second method of checking consists in kneading 2÷3 liters of clay with water with an oar. If the mass almost all its volume sticks to the tool, it means that the clay is greasy and requires an additional portion of sand, greater than that specified in the recipe.
Suitable for masonry mortar is considered to be clay, which when kneaded remains on the paddle in separate clots.
- The third method of checking can be called the most accurate. It consists of mixing 0.5 liters of clay with water to a dough. Then, from this mass rolls a ball, size 45÷50 mm. Then it is placed between two smooth planks and gently squeezed until it, which has turned into a tortilla, does not begin to form cracks.
Testing samples of clay mortar for fatness
When using this method of testing, the fatness of the raw material is determined by observing at what thickness on the pellet cracks have formed, and what kind they take.
Conducting such tests, it is possible to immediately bring the experimental mass to the desired condition by adding sand or fatter clay to it. It is recommended to write down the proportions of the best options. When the optimum ratio of materials is determined, it will be much easier to make any amount of mortar.
Cleaning the clay
After the clay has been selected, it must be cleaned, because after this process, the physical and mechanical properties of the raw material will improve, and therefore the masonry itself will be of higher quality, both technically and aesthetically. The cleaning process can be carried out in two ways:
Masonry mortar is a mixture of powdered materials (filler and binder), shuttered with water and/or liquid glass (orthophosphoric acid) to increase plasticity, reduce mortar moisture and internal cracks of the joint, reduce shrinkage of bricks after drying. Some mixtures are supplemented with plasticizers to obtain a thin, durable joint.
Mortar composition and density should be consistent with the type of bricks and the place of installation (the temperature of the furnace, ash pan, chimney. different, wood, coal, gas furnace. different). In the furnace of a wood-burning stove, the temperature is usually not raised to fully sinter the mortar on pure chamotte mortar. In furnaces, which are heated with anthracite, also not all places are heated by flue gases to the firing temperature.
Stove built in the bath, a room fireplace, a Russian stove for cooking or a barbecue in the yard are in different operating and climatic conditions, and therefore, the solution must be selected based on the characteristics of the environment. for high humidity, frostproof, environmentally sound.
The more precisely the geometry of each item, the thinner the joint can be. Some masters are of the opinion that a joint of 3-4 mm is an indicator of a quality lining. Others argue that too thin joints as a result of frequent heat changes do not sufficiently compensate for the thermal expansion of the masonry of domestic stoves. They recommend an average thickness of 6-9 mm. The thickness of a masonry unit and the way the bricks are tied together become a decisive factor in the thermal expansion of the stove.
At the same time the mortar should not be liquid (0.6 liter per 1 liter of dry mixture), but semi-dense (0.5-0.55 liter / L) or thick (0.35-0.4 liter / L), for ready-made mixtures you usually need less water. The thicker the mortar, the thicker the joint can be made. The amount of water also depends on the water absorption capacity of bricks: e.g. in case of masonry with clinker bricks, the mortar must contain less water.
It is better to put up, dry and light the kiln in dry and warm weather. The kiln must not be clad until the mortar has dried and a test firing has been performed.
Tip! When masonry individual parts of the furnace, try to take bricks of the same brand (dynamite, chamotte, ceramic) and from the same batch. Thus, the rate of filling of open pores with mortar, adhesion, drying time, volumetric and linear expansion will be the same for all bricks of the same section of the kiln.
about the properties of mortars
For the sake of clarity, we will further summarize the above mentioned properties of mortars, on the basis of which their place in the body of the stove is determined:
- Clay mortar is the cheapest, it can cost you nothing at all, see. below. Preparation of the component requires more labor and time. Medium strength and heat resistance, up to 1,100 degrees. Absolute fire resistance: can be dissolved only in hydrofluoric and antimony-fluoride acids. Maximum gas tightness. Does not set, but dries. Melted again when wet, so the stove can be reworked if necessary, but not suitable for outdoor masonry. Kneading requires certain skills, see “Lime Kneading”. video below. Suitable for use indefinitely: covered with a damp cloth, it does not dry for months, and completely dried after soaking, it fully restores the properties.
- Lime dough is more expensive, t.к. You can’t do without buying lime dough or at least a lump of quicklime. Kipelka is much cheaper than dough, but requires a lot of work and time for preparation: it is necessary to extinguish all lime to the last particle, otherwise the un-extinguished particles then tear the joints of masonry. The strength is slightly higher than that of clay dough. Heat resistance and refractoriness are below average: can withstand common flue gases at temperatures up to 450-500 degrees. Gas tightness is lower than that of clay bricks. Not hygroscopic, can be used in the open air. The suitability of the batch to work. 1-3 days, depending on the weather.
- The cement-lime one is more expensive and durable than the lime one, but the thermal chemistry is up to 200-250 degrees. Gas tightness low. Mainly used for furnace foundations. Suitability to work. 1 hour from the beginning of batch. Labor intensity. as at lime sand.
- Clay fireclay. all parameters as clay, but the heat resistance to 1200-1300 degrees. expensive than clay, t.к. it is necessary to buy expensive fireclay sand. Suitable for masonry fireboxes.
- Cement-lime-sandy. expensive, t.к. You need high-quality materials. Same strength as cement-lime, heat resistance as clay fireclay, medium refractoriness, sufficient for the furnace part. Gas tightness is high, almost the same as with the clay one. Labor intensity is not high, as in the construction cement-sandy. Not to be kneaded by hand. Working time is 40 minutes from the moment of mixing.
The term “gas tightness” means that relatively dense flue gases cannot pass through the mortar layer by diffusion. Gas tightness does not exclude hygroscopicity: molecules of water vapor are smaller and more mobile than those of flue gases, so the stove can breathe. Cement-sand mortar is not gas-tight and does not breathe: smoke fumes will gradually leak through it, and it does not absorb water vapors. The stove must be laid on a mortar that, in addition to strength, provides an optimum combination of gas density and water absorption for a given section of the structure of the stove. The formulation of traditional oven mortars was developed with this requirement in mind.
Note: Gypsum-lime mortar, which is used for stove plastering instead of conventional plaster, is not discussed here. It is a finishing material, not flame-retardant and not fireproof.
Mortar for masonry according to all the rules
As already noted, its ideal consistency should correspond to the thickness of sour cream. If fat clay is taken for it, then 2 parts of sand should be added to 1 part, if normal. the proportion should be equal.
Before proceeding to masonry furnace, it is necessary to check the quality of the resulting furnace mixture. To do this, you will need to fasten the solution 2 bricks, wait about 5 minutes, and then raise the top brick. If the design does not disintegrate in a few lifts, the mortar for masonry furnace brick is perfectly matched. If this does not happen and the bond quickly fell apart, it is likely that lean (nonfat) clay was taken for the preparation of the mortar.
Experienced furnaces also advise to increase the strength of the solution by adding table salt to it (150 g is enough for 10 kg of clay). Here you can also add cement M400: 1 kg for the same volume of clay.
When the stage of work on the chimney begins, it will be better to replace the clay mortar with a lime-sand one: it is more resistant to moisture. To prepare it, take 3 parts sand and 1 part lime dough. As an option. 1 part quicklime and 3 parts water.
What deviations are within the norm?
Immediately stipulate that it is desirable not to make mistakes, but even if this happens, some of them can be corrected. Not subject to adjustments a large amount of sand. with this component should be very careful. Pre-check the condition of the mass in 1-2 ways, so that later you do not have to rearrange individual rows.
It is allowed to violate the quality or quantity of clay. If too greasy is chosen and the plaster gives cracks visible even to the naked eye, they are smeared with a solution of whitewash and sand in several stages as it dries up. Usually this is done within a month, grouting 3-4 times the joints.
How to prepare the mortar for laying the stove in the bath
Before preparing the lime mortar for masonry furnace, the lime dough must be strained through a sieve, mixed with sand sifted through a fine mesh in advance, then add some water, without ceasing to stir the mixture. Thus, the mortar should be brought to the necessary thickness.
For 1 part of the lime dough you will need 2-3 parts of the sand. Freshly prepared lime mortars, unlike cement mortars, retain their properties for several days. For greater strength, it is recommended to add cement to the mortar, but to reduce the setting time (for example, when plastering) it is better to add gypsum.
There are also differences in the degree of fatness of lime mortar. To determine it correctly, it is necessary to stir the already prepared mortar with a wooden spatula for a few minutes, then look at the degree of adhesion. Thin mortar does not stick to the blade, while fat mortar coats its surface in a thick layer, and normal mortar lies in a thin layer or remains on it in places.
A lime mortar of normal fat content is ideal for laying. In order to change the degree of fatness of the solution, it is recommended to add the missing components to it. For example, to increase the fatness of lean mortar, it is necessary to add lime dough, and to reduce the fatness, sand is used as an additive.