Today the market of insulation materials is filled with a wide variety of materials, from mineral wool to extruded polystyrene foam. However, even expensive materials do not guarantee complete heat retention. Most of the specialists in this field began to return to the long-known, but lost popularity, methods of thermal insulation of buildings. In this article, we will talk about how sawdust warming is carried out.
Sawdust types
Sawdust is small particles of recycled wood that are obtained from sawing. In appearance, they look like fine dust.
Sawdust can be purchased in different fractions from 5 mm to 3 cm. The length depends on the technological process of the woodworking enterprise, namely on what type of tools is used in each particular case.
This material is environmentally friendly. In addition to low cost, sawdust has many other advantages, for example, excellent thermal insulation and sound-absorbing qualities, as well as a small specific gravity of the material. Sawdust is mainly produced from hardwoods such as spruce, pine or ash.
Insulation of the ceiling with sawdust
It is necessary to insulate the ceiling in a private house from any material, both from bricks and from foam blocks. Because it is through the ceiling that significant heat losses occur. Average heat loss through the ceiling is 20%. From an economic point of view, the most advantageous is the insulation of the ceiling with sawdust.
Note that the stacking of wood products is a laborious task. Before starting the installation, it is necessary to carry out a lot of preparatory work. First of all, such work is aimed at protecting against fire, because wood in any form is extremely flammable. It is highly flammable and has a long burning time.
What materials and tools may be needed:
- fine and coarse sawdust
- sand, clay or slag
- lime and copper sulfate (you can take boric acid)
- substrate. For this purpose, you can use corrugated cardboard or any other breathable materials that have good vapor permeability.
- sealant and polyurethane foam
- fire retardant and wood preservative. These compounds are necessary if the ceiling boards are not covered with a protective material against mold and mildew, fire
- construction stapler and staples to it.
The work must begin by protecting the ceiling beams and planks from possible adverse factors. More often than not, quality buildings are already built from processed timber. However, if this procedure was missed for some reason, then it is imperative to carry it out now.
Wooden elements must be protected comprehensively, and the following sequence must be observed:
- antiseptic is applied first, which prevents rot and protects from insects
- then there are fire-retardant agents that increase resistance to fire and high temperatures
- the third use water repellents to prevent moisture from entering the wood structure. In addition, such products protect the wood from washing out the previously applied solutions.
To achieve higher efficiency, it is worth purchasing all drugs from the same manufacturer.
After carrying out the protective work, all seams and joints must be sealed with foam and sealant. In addition to the cracks in the ceiling, any other holes that may be present in the roof structure must be repaired. This is necessary so that the insulation material does not come into contact with precipitation or strong wind, which can raise the insulation layer. Do not forget to trim the protruding parts of the foam at the same level as the ceiling beams, otherwise there will be voids in these places through which heat will escape.
Next, you can lay the substrate, which is needed to prevent fine dust from shedding from the sawdust from the ceiling. This dust can create additional dust in your home. The substrate must be vapor permeable. If there are no such qualities, then warm air and steam, rising up, will remain between the boards and materials, and will cause additional condensation. This can result in mold formation due to excessive moisture. Any cardboard can be used as a substrate, for example, from old boxes, packaging. The main thing is that it must be absolutely dry.
Clean the ceiling boards from dirt and dust and put cardboard sheets on them in several layers. Overlap the underlay 15-30 cm so that sawdust does not get into the seams. Now you need a stapler, with which you need to fasten all the joints of the material.
Sawdust needs to be bought dry, without foreign odors. In advance, they should be treated with compositions of fire retardants and antiseptics. After the mass has dried, you can add 10% lime (fluff) and a small amount of copper sulfate (or borax) to it. All this needs to be mixed well.
Several basic methods of installing sawdust thermal insulation are possible. They can be filled up dry or mixed with cement and diluted with water. Sawdust can be poured both in a clean dry form, and mixed with cement and diluted with water.
With the dry method, sawdust is poured into two layers:
- coarse fraction or shavings. This layer should have a thickness of 10-15 cm. It must be well tamped.
- the smallest fraction. The second layer should be the same thickness as the first. And it also needs to be tamped well.
In addition, slag, sand or clay can be placed on top of the sawdust. These materials will save your sawdust from rodents and mold growth.
In order to insulate the ceiling with the wet method, you need to buy sawdust, which was made at least a year ago. These sawdust will be slightly damp. However, make sure they are free of mold.
The ratio of shavings, water and cement: 20: 3: 2. The mixture must be made in small volumes, because it dries quickly. The resulting solution must be poured between the floor beams on a substrate or a layer of sand and tamped. The thickness of the layer should be 5-10 cm. The mortar completely hardens and you can move around it.
Sawdust, as insulation, is great for floor insulation. As in the case of the ceiling, sawdust for floor insulation must be pretreated from rodents, insects and microorganisms. For this, it is better to use special ready-made solutions.
The difference between floor insulation and ceiling insulation is that it is very difficult to fill up the insulator, which shrinks in the floor structure. Therefore, you need to choose in advance a method in which the mass will not dry out over time. In practice, this means that when dealing with thermal insulation of the floor, it is worth using not dry sawdust, but mixed with different components and subsequently hardening.
To prepare this mixture, you need to add gypsum or cement to the sawdust. Observe the following proportions: 85% sawdust, 5% gypsum and 10% fluff or lime dough, which should be taken twice as much as dry lime. Do not forget that gypsum hardens very quickly, faster than cement.
It makes no sense to dry the sawdust before mixing. On the contrary, if the sawdust is dry, it is worth adding a little water. The degree of readiness of the mixture is checked in the hands - if the lump does not crumble and does not spread, then the composition is ready.
If the insulation is carried out in a building that has already been operated, then the existing floor covering will have to be dismantled, the floors will have to be re-treated with an antiseptic with moisture-resistant mastic, and then a substrate made of vapor barrier material or film should be mounted.
The created mixture of sawdust is placed on the substrate and compacted well. The thickness of the layer should be about 10 cm. After tamping, the mass should be left to harden, about 2-3 weeks.
When using dry sawdust, create a raised floor. All wooden parts must be covered with protective agents. Next, a rough floor is mounted on the base from the boards, on which the waterproofing is spread. Sawdust is poured on top of the hydro-barrier. The layer should be 10 cm or more. Note that sawdust insulation is not suitable if you are going to make a screed. Sawdust is of low strength and shrinks significantly. Before installing the topcoat, leave the floor for 2-4 days. During these few days, the sawdust will shrink by 2-3 cm and you will need to add an additional amount.
Be sure to keep in mind that if the sawdust is not made good waterproofing and ventilation (the gap between the finished floor and the layer of insulation material), then they may lose their heat-shielding qualities.
The most difficult task can be called wall insulation, because this will require creating a frame. The frame must be filled with sawdust and tamped by hand. Coarse sawdust is suitable for laying in a frame wall. With a dry version of the bookmark, you should take care of thoroughly drying the sawdust so that there is no moisture left in them.
With the wet method, the mixture is prepared from wood chips, lime, gypsum or cement, with the obligatory addition of antiseptics. The thoroughly mixed mass is moistened, poured into the prepared frame and tamped tightly so that the material does not sag. Gypsum, like cement, after a while draws out all the available moisture, and makes the mass monolithic.
Between the wall and the insulation material, it is imperative to lay a waterproofing material that has vapor-permeable qualities. The effectiveness of the insulation and the level of shrinkage depend on the quality of the ramming and the density of the filling. If not tamped tightly, voids will appear and heat loss will begin.
The mixture is placed in layers 20-30 cm high and tamped. After that, a second layer of the same is poured. And so the actions are repeated at the entire height. The thickness of the insulation depends on the climatic conditions. For example, in a house with seasonal residence, a thickness of 15 cm is enough, but in a capital structure, a thickness of 25-30 cm is needed. The frame is created from wooden boards with a section of 100x50 mm.
The mass hardens in about 1-2 weeks, and finally sets in about a month. All this time it is worth monitoring so that the air humidity does not exceed 60-70%, and the temperature does not rise above 20-25 degrees. In addition, you need to regularly ventilate the room. After that, you can start finishing work.
Houses insulated with sawdust are an excellent option. They combine high heat retention rates with low work costs.
Sawdust house
In addition to insulation, sawdust is used for the full-fledged construction of buildings. However, buildings made of sawdust concrete are rare today. Nevertheless, experts assure that sawdust concrete is a very promising material that allows you to build economical housing with decent performance.
The manufacturing technology of such a material involves the addition of binders, for example, clay, lime, water glass. These additives reduce shrinkage and reduce the cost of the modules. By adjusting the proportions of individual components in relation to the total weight, you can change the density, porosity and strength of the final product.
Practice shows that optimal protection is achieved after cladding, however, for example, a sawdust bath can be used without finishing.
The advantages of sawdust concrete include:
- thermal conductivity 0.20-0.30 W / m ° С. Wall, 40.00 cm thick, similar in warmth to a brick wall 90 cm
- strength 20.0-50.0 kg / cm². This material perfectly resists deformation and shock loads, so it can be used for construction in areas with probable seismic activity.
- easy handling. Modules can be milled, nailed, drilled, hacked and sawed. Consequently, material consumption is reduced, there is almost no waste
- shrinkage 0.50 - 1.00% mm / m
- frost resistance - 25 cycles
- density 300-1200 kg / m³.
Of the shortcomings, we note:
- moisture absorption. This disadvantage can be combated by processing blocks with special compounds.
- impossibility of building multi-storey buildings
- not very attractive appearance without finishing.
Material calculation
Let's look at an example to find out the average number of blocks required to construct a building. For example, you need to build a house with dimensions of 15x10 m, with a wall height of 3.00 m. The perimeter of the building will be the sum of the lengths of all sides = 15 + 15 + 10 + 10 = 50 m. The area of the building is the perimeter multiplied by the height = 50 * 3 = 150 m². It is worth considering both the thickness of the masonry and the number of blocks in 1 m2.
Building wall blocks made of cement and wood chips, according to GOST 19222-84, are called "wood concrete products" and, if necessary, can be made at home on their own.
Wall blocks made of shavings and cement
The technology for manufacturing building blocks from wood concrete was developed in the USSR back in the 60s of the last century. A number of factories were built and launched. However, due to the "victory" of the panel construction technology, they forgot about the arbolite and returned to it quite recently. It is a unique building material that combines excellent thermal insulation properties, low cost and ease of manufacture.
Chip and cement blocks on their own - recommendations of specialists:
- A mixture of wood shavings and wood chips should be used as raw material. At the same time, the content of harmful impurities is regulated: needles and leaves no more than 5%, bark no more than 10%. It is allowed to use shavings and chips with a particle fraction of 40x10x5 millimeters and a chip: chips ratio - from 1: 1 to 2: 1;
- Fresh shavings and wood chips contain sugar, therefore, in order to avoid rotting and destruction of the block, it needs special preparation before use. There are two options - exposure in the open air for 4 months with regular shoveling, or treatment with a special solution: 200 liters of 1.5% lime solution per 1 m3 of sawdust. Process sawdust and leave for several days with regular shoveling;
- Quality blocks can be obtained using a mechanical concrete mixer;
- As a binder, you should use ordinary Portland cement of grade not lower than M400, and use as additives: liquid glass, fluff lime, calcium sulfate and aluminum sulfate. In this case, the total amount of additives should not exceed 4% by weight of the cement;
- The proven and best combination of additives for the production of wood concrete blocks: a mixture of aluminum sulphate and potassium sulphate in a ratio of 50:50, or a mixture of calcium oxide and water glass in a ratio of 50: 50%.
Features of the production of blocks from shavings and cement
- Before use, shavings and chips must be passed through a chipper and a hammer crusher, and also sorted on a vibrating screen or through a hand sieve;
- The finished mass with additives should be thoroughly mixed with cement in a mechanical concrete mixer and only then fed into the prepared forms. The proportions of the components are different. In general, a recipe is recommended: 1 part of Portland cement, 6 parts of a mixture of shavings and chips, 2 parts of sand + additives;
- Manufacturing technology of a form or several forms. From edged boards and wooden blocks, a frame measuring 600x300x240 millimeters is knocked off or twisted (with self-tapping screws). Handles are nailed on opposite sides of the frame (bars 250x50x50 mm). To each form, from boards and bars, a pallet is knocked down or twisted. For the convenience of removing the block, the inner surface of the frame and pallet is upholstered with galvanized steel or linoleum.
Product forming technology
Before pouring, the inner surfaces of the mold are lubricated with grease, machine oil or a special separating solution. Next, a mixture of cement with sawdust and additives is loaded into the mold, layer by layer. Each next layer is rammed with a piece of a bar covered with galvanized steel or a mechanical vibratory rammer.
The filled and tamped forms are left for a day, after which the blocks are carefully removed, placed in a cool place and covered with plastic wrap. On hot days, to avoid drying out, the blocks are sprayed with water. After 14-20 days (subject to an ambient temperature of 20 degrees Celsius or more), the blocks are ready for use.
Application features
- When erecting external walls of buildings from wood concrete blocks, to prevent moisture ingress, it is recommended to equip a brick or concrete base, at least 0.5 meters high from the level of the blind area. For this reason, the overhang of the roof eaves beyond the outer surface of the walls should also be at least 0.5-0.6 meters with the mandatory installation of a rain and melt water drainage system;
- For laying blocks, cement mortar with a grade of at least 10 is used;
- Interblock seams should be 10-15 mm;
- Blocks of shavings and cement can be used as an internal insulating layer by analogy with adobe (blocks of a mixture of clay, straw and sawdust);
- Arbolite blocks or wood concrete mass can be used as a filler for well brickwork. Installation is allowed to the full height of the floor without bricking or reinforcement;
- If necessary, it is possible to build lintels of window and door openings from wood concrete. Mandatory reinforcement is required.
Sawdust and cement blocks
Now in construction you will not surprise anyone with composite materials. What only yesterday coexisted peacefully, today, with new technologies, complements each other, mixes up. And as a result, materials are obtained that have acquired better quality characteristics from the components being mixed, or even new properties in general. These materials include wood-cement. After all, we know that when mixing solutions, fillers are needed. So why not wood waste as a filler? The benefit is twofold: both the waste will go to work, solving the problem of their disposal, and the concrete will become much lighter.
Types of wood-cement materials
Since wood materials of different size and structure can be added as a filler, and the addition of cement and other components can be in different proportions, there can be several wood-cement materials. Here are the main ones:
- - wood concrete;
- - fibrolite;
- - sawdust concrete;
- - DSP (cement-bonded particle boards);
- - xylolite.
And since the difference in composition leads to a difference in properties, materials with different performance characteristics are obtained. This allows the use of wood-cement materials in construction quite widely.
Arbolit
This is a lightweight concrete made from wood chips, water, chemical additives and a mineral binder, most often Portland cement. Crushed is obtained from both deciduous and coniferous species, it is even possible to fill concrete with flax or hemp fire, chopped straw, and crushed cotton stalks.
Wood concrete production technology is as follows:
- 1. Wood waste is transported by conveyors to the chipper.
- 2. The resulting chips are sent to a hammer mill.
- 3. The pneumatic conveyor feeds the resultant to a vibrating screen, from where dust and fine crushed particles go to the waste bin, the coarse crushed material is sent for re-crushing.
- 4. The required crushed fraction enters the soaking bath, from there through the batcher to the mixer.
- 5. Through other different dispensers, cement, water and chemical additives are supplied to the mixer.
- 6. The resulting mixture in molds is compacted with presses or vibrocompressors.
- 7. Forms with wood concrete are supplied by heat treatment and drying.
The use of wood concrete: partitions, slabs for floors, ceilings and coverings, large-format wall panels, wall blocks, etc.
Fibrolite
It is a board made from wood chips and mineral binder. Chips over 35 cm and width 5-10 mm is ground to a state of wool. Further, the technological process looks like this: the shavings are mineralized with potassium chloride, moistened and mixed with cement paste, plates are pressed at 0.4 MPa. This is followed by heat treatment in hardening chambers and drying.
Fibrolite is used both for the construction of walls and as a filler and insulating material in frame structures. It should be noted that when using fiberboard as a wall material, it should be plastered, and where the humidity is increased, it cannot be used at all.
Sawdust concrete
It is a lightweight concrete made from sand, Portland cement and sawdust. The technology is as follows: sawdust and small shavings are poured into the mixer, water with mineral additives and Portland cement are also fed there. All this is mixed, decomposed into forms and compacted. In order for sawdust concrete to harden faster, it is kept in thermal chambers at a temperature of 40-60 ° C for 24 hours.
Sawdust concrete is used for the production of panels and wall blocks, used for the manufacture of clean floors.
Cement particle boards
They are the most commonly used wood-cement materials. For their manufacturecomes wood shavings, then a cement-bonded mixture is prepared from it, by mixing the shavings with water, cement and mineral additives, followed by dosing, molding, pressing and heat treatment.
Cement particle boards are frost-resistant, fire-resistant and bio-resistant. this justifies their application in prefabricated housing construction. Moreover, they can be used for facade work and for interior decoration. They are not afraid of high humidity, they have proven themselves well in restoration work.
Cement particle boards also have disadvantages. High density (up to 1.4 t / m³) makes it difficult to lift slabs for facing the last floors of houses without winches andforests. They also have low bending strength, the plates can break. At the same time, they are very resistant to longitudinal deformation, for this reason they are used to strengthen the frames of houses.
Xylolite
It consists of a magnesian binder, alkali-resistant pigments and sawdust, to which finely dispersed minerals are added: asbestos, marble flour, talc.
During production, sawdust is sieved through two sieves (the remaining on 1 sieve and sifted through the second does not participate in the technological process). A binder is prepared in mixers: first magnesite is fed, then coloring pigments, then magnesium chloride (as a hardener). This mixture is fed into another mixer, where it is mixed with sawdust for about 5 minutes.
Further, the plates are formed under significant pressure (up to 10 MPa), at a high temperature (up to 95 ° C) they solidify in the curing chambers. Then, for full condition, the slabs are dried in warehouses for two weeks. In order to increase the water resistance, the slabs are impregnated with hydrophobic compounds. Most often, these boards are used for the production of floors.
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Sawdust concrete and wood concrete blocks are a lightweight building material with good thermal insulation characteristics. They are used for the construction of private houses, outbuildings and fences. Sawdust concrete and wood concrete can be bought ready-made or made by hand. For manufacturing, you will need the same components as for standard concrete blocks, but with the addition of sawdust or chips. They can be both structural and heat-insulating.
For blocks of sawdust concrete, you will need cement, sawdust, sand, quicklime and water. Portland cement is taken at a grade not lower than M300. It is better to use sawdust from conifers, as they are less prone to decay. If they are old or obtained from other wood, then they need to be prepared. Treat with antiseptic agents such as calcium chloride solution and dry.
The density of sawdust and cement blocks depends on the proportions of the components. The more Portland cement, the stronger the material, but the worse the thermal insulation properties. At the same time, resistance to low temperatures, moisture increases and the likelihood of corrosion in reinforced blocks decreases.
If you add more sawdust, wood concrete blocks will retain heat better, but it cannot be used for the construction of load-bearing structures. Due to the small amount of cement in the composition, it will have poor strength. Therefore, it can only be used as thermal insulation for a finished structure. At the same time, no additional foundation is required for masonry, since it is light in weight.
Blocks made of a mixture of cement and sawdust are used for the construction of load-bearing and internal walls of buildings, enclosing structures, for the reconstruction of already rebuilt structures, as well as for the insulation of houses and basements.
Positive and negative characteristics
The advantages of block material made of sawdust (they are confirmed by numerous reviews given in the material about):
- easy to process - sawdust concrete can be cut with an ordinary hacksaw and drilled, just like aerated concrete or foam concrete;
- has good adhesion characteristics - when processing with adhesives, the topcoat is reliably fixed to it;
- good thermal insulation properties;
- low-combustible - with the correct manufacturing technology, sawdust concrete can withstand direct exposure to fire for about three hours (if the amount of sawdust does not exceed 50% of the total volume);
- environmentally friendly;
- soundproof;
- simple masonry;
- long service life.
Sawdust concrete acquires the property of fire resistance as a result of enveloping the sawdust with a cement-sand mixture. Compared to concrete with expanded polystyrene granules, sawdust blocks are more fireproof.
The disadvantages include a long curing time. After manufacturing, building blocks with a thickness of 20 cm are left for 3 months to fully harden. Only after this period you can start laying them. Sawdust concrete has poor water resistance. Therefore, after the construction of the house, a vapor barrier should be installed to protect it both from the inside and outside of the building.
How to do it yourself?
There are many technologies for making sawdust blocks. Not only cement, but also gypsum or clay can be selected as a binder. But if the block material will be used for the construction of loaded structures (walls), then Portland cement is taken. To prepare the solution on your own, it is recommended to use a concrete mixer, since a completely homogeneous consistency is required.
According to the technology established in accordance with GOST, in order to make high-quality blocks, it will be necessary to mix the components in the following proportions - 1 part of cement, 1 sawdust, 3 sand and 50% of the volume of binder water. Calcium chloride is taken 40 times less than the amount of cement powder. That is, 20 kg of M400 Portland cement will require 20 kg of sawdust, 59-60 kg of sand and 10 liters of water. Additionally, 0.5 kg of calcium chloride is poured. In percentage terms, sawdust should make up almost 55% of the total solution volume, sand - 26%, cement - about 12%, water - 7%.
Sand is used in medium or coarse size. At the same time, about 10% of fine fraction is added. Only clean water is poured in. Drinking or rainwater is best, the main thing is without impurities and dirt.
To make the blocks yourself, you will need forms in which the mixture will fit. It is recommended to make them collapsible, so that it is more convenient to pull out the finished material. It can be built from boards 20 mm thick. Inside, they are covered with sheets of steel so that moisture from the solution is not absorbed into the wooden case. In addition, thanks to the metal, the block material can be easily separated from the mold.
When assembling a box for sawdust concrete or wood concrete blocks, it should be borne in mind that after drying, they decrease in size. Therefore, the mold must be made 10% larger than the required material size. If there are blocks with voids, for example, round, then only rolled into a tube is placed in the box in advance.
Manufacturing technology: sawdust is sieved through a sieve and mixed with Portland cement and sand. Water is gradually poured in. To check the quality, the solution is squeezed in a fist. It should crumple into a lump, water should not flow out. If drops are visible, then it is not mixed correctly. After preparation, the composition must be wasted within an hour and a half. The mixture is placed in a mold. Every 20 cm, it is rammed to compact and remove air. After filling, everything is left for 4 days. After that, it can be disassembled and folded block building material in a dry and ventilated room for further hardening.
Peculiarities
For wood concrete blocks, not sawdust with sand, but only chips are used; cement and various additives are also needed that improve other characteristics. Compared to sawdust concrete, this material has even better thermal insulation properties. It is just as light, frost-resistant and non-combustible. The blocks are environmentally friendly, they are easy to cut and handle.
For self-production of such blocks, you will need forms. The solution is mixed in a concrete mixer. To make wood concrete blocks, the components are mixed in the following proportions: 3 parts of cement, 3 parts of wood chips and 4 parts of water. First, chips are poured into the concrete mixer and water is poured in (not all at once, only to a semi-liquid state). Liquid glass is added (1% of the total volume). After the consistency has become homogeneous, Portland cement M400 is poured in and the rest of the water is poured in.
Once the solution is thoroughly mixed, it is placed in a mold for wood concrete blocks. Every 15-20 cm the mixture is tamped. A day later, if the material has hardened, it is removed from the molds and left to cure. After 2-3 weeks, the blocks can be used.