Is it possible to make a foundation from slag. Features of the construction of the foundation from dump slag

Slag-concrete mixes enjoy well-deserved popularity not only in industrial, but also in private low-rise construction. This is due to the characteristics of this material. Slags added to the composition of concrete are obtained as a secondary material in the metallurgical industry.

For a long time, granular material was considered just waste, but world practice has proven its expediency for use in construction. Slag concrete is lighter than sand and gravel, it is distinguished by its durability, resistance to temperature fluctuations, and soundproofing properties.

It is the metallurgical material mixed with cement that has the greatest strength. Lime, gypsum or even clay can also act as a binding agent. Two types of granulated slag are actively used:

• with fine grains (0.5-1.5 mm) - rather heavy concrete of high strength with good thermal conductivity is obtained;
• with large grains (20-30 mm) - concrete is lighter, provides good thermal insulation, but is slightly less durable.

The use of varieties larger than 6 mm is not recommended, since the durability of such concrete will be unsatisfactory. Smaller fractions are preferably replaced by sand. for construction should be as clean as possible, without impurities of clay, soil, organic elements.

Given the properties of concrete with different fractions, to create exterior walls, large and small grains are often mixed in a ratio of 7: 3, respectively. For internal partitions, you can take one more fine slag. If you want to get the most durable mixture after solidification, it is advisable to completely remove the 12 mm fraction, and replace 20% of the finest slag with sand.

How to prepare cinder block

Prior to the preparation of the mixture (about a few hours), it is necessary to moisten the slag with water in order to improve the durability of the future concrete. Next, you need to mix the components in one of the above proportions, mix well. After adding water, the solution should be kneaded until smooth. To obtain an average brand of concrete, you can use 4-5 parts of slag (fractional mixture), 2 parts of cement and 2 parts of sand.

It is desirable to use the finished mass within an hour, the maximum processing time is 1.5 hours. A cheaper solution can be made by mixing cement with lime in a 3: 1 ratio. The walls of the house can be erected by the stuffing method (monolithic construction) or from prepared cinder blocks.

The content of the article

The cinder block foundation is perhaps the cheapest type of tape-type foundation. After all, the price of a cinder block is minimal, and any novice builder can master the technology of building a foundation from this material. In addition, not only the base can be built from the cinder block, but also the load-bearing walls, as well as interior partitions.

Therefore, in this article we will talk about how to build a foundation from slag, introducing our readers to the most common technology for using recycled materials.

Cinder block production method

A typical slag block is made by casting a special solution standardized form followed by vibrocompression of the semi-finished product. As a solution, a mix is ​​used, consisting of a dry part (sand, cement, waste slag or brick slag) and water.

Moreover, by making a foundation from waste slag, or rather a foundation block, the consumer of such products solves two problems at once: it helps to dispose of secondary raw materials (in fact, non-toxic waste from some kind of production) and reduces the cost of building material. In the end, both people and nature win.

Assortment and sizes of cinder block

The assortment of slag foundation blocks consists of monolithic and hollow products. Moreover, blocks with internal voids are made in the form of cast "shells" with voids from 28 to 40 percent. Well, the shape of the hollow cells divides the assortment of such blocks into five varieties.

Monolithic products are used only for the construction of the foundation, and from hollow structures it is possible to build both a load-bearing and an interior wall. The reason for this selectivity is the insufficient heat resistance of monolithic blocks. And an empty product filled with foam concrete or loose insulation keeps heat no worse than an ordinary foam block.

Moreover, the foundation for a wall-type cinder block can be equipped from the same material - a monolithic block of slag. After all, the total weight of a structure built from a hollow block will be significantly less than the mass of a brick or monolithic house.

The dimensions of the foundation block (length, width, height) are standard - 390 by 190 by 188 millimeters.

Advantages and disadvantages of cinder block

The list of advantages of slag blocks should include such properties as:

• Cheapness - this building material consists of waste almost half.
• Strength - the base of the blocks is able to withstand a structure weighing up to 100 tons.
• Frost resistance - a hollow block holds the body no worse than a foam concrete product.

In addition, due to the relatively small mass and rather large dimensions of the cinder block, the construction of a foundation or walls from such material is faster than similar work based on laying bricks or installing reinforced concrete products.

The disadvantages of the cinder block include the following characteristics:

• Insufficient hydrophobicity. Such a block absorbs moisture from the soil and the atmosphere. And this property affects the durability of the product not in the best way.
• High thermal conductivity of monolithic products. A whole block, without voids, cannot prevent unwanted heat transfer between the heated room and the street.
• Insufficient strength in the transverse direction. The foundation wall of such blocks cannot contain the transverse load. Therefore, such foundations are not mounted in seismically hazardous areas or places where there is a risk of movement of soil layers.

However, some of the shortcomings of the cinder block can be eliminated using long-established technologies for these purposes. For example, low heat resistance is leveled by the installation of insulating panels. And the tendency to absorb moisture is eliminated with the help of reliable waterproofing of the walls and the base of the foundation.

How to build a foundation for a cinder block house?

The construction of a foundation from slag blocks is possible only on relatively dry soils with a low level of groundwater and a shallow depth of soil freezing. In addition, such a foundation cannot be built on clay (or similar) soils. The reason for this selectivity is insufficient lateral stability.

What exactly is slag?

If, after this question, medical associations begin to flash in your head, then this is not a problem: this term is also used in the medical field. But now we are talking about construction. And from the point of view of construction, slag is a solid residue that appears after the end of the process of smelting metal from ore. Well, or after the coal is burned. There are other options, but in this case we will not dwell on them. If we talk about what building materials are made from slag, then this is usually tiles and bricks.

Also, you are probably familiar (well, or I will introduce you now) with such a building stone as a cinder block. This is such a small, let's say, slab, which is prepared using cinder-concrete mortar. The binder in cinder blocks is cement.

So, a small educational program passed. Now that we have a general idea of ​​the subject, we can move on to the more practical part. The point is this: sometimes, already in the process of building a house, developers turn a blind eye to the quality of the slag that is chosen for the walls. Like, there is cement, it will bind everything. This is where the error lies. Slag is not just a filler. It affects both the properties of lime and the properties of cement. Hence, as one well-known Duchess said, morality: it is a high-flying bird (in the sense, the slag must be of high quality).

Now here's what. Cinder block walls and other slag walls can behave differently over the years, that is, damage over time can be of varying degrees of complexity and severity. Therefore, before doing slag wall repair, you need to carefully evaluate how worn the material is. Then it will be easy to pick up repair options.

What can happen to cinder-block walls?

Let's start with a simpler and less capital one. Let's say you have a house, slag walls, and over time, the plaster began to peel off, which will require repair. We have already discussed how to perform it once in the article - repairing wall plaster in separate places, I advise you to familiarize yourself. This can happen both outside and inside. What to do? For external repairs, work may be recommended not to restore, but to strengthen. The principle of siding is quite suitable for such a case. But indoors it would be nice to use the plasterboard sheathing method. This will hide defects, and the walls will become smoother. At your discretion and taste, you can apply other types of plates for interior decoration. Here it's up to you to choose.

So, now about the cracks. The case in this situation will be somewhat more complicated and painstaking. If you still do not want to change housing, build a new one and do similar pirouettes, then we take up the tool (not the head) and proceed to decisive action. You can start repairing the walls with repairing the foundation. Longer, but more serious. You can arrange reinforced belts (they must be reinforced) around the entire perimeter of the house and then plaster them over a metal mesh. And if you still carry out this procedure in combination with strengthening the foundation, then the result will be doubly reliable: “cinder-block palaces” will last for many, many more years.

I almost got out of my head: there are also structures made of bulk slag! They differ from those already listed in that they do not have the usual seams. What to do if they are repaired? For example, when plaster crumbles and cracks appear, you can pierce the plaster with nails, then pump a cement mortar into the cracks under pressure. Next, create a kind of timber formwork, and then cement it.

Repair of walls in the apartment "overtakes" almost everyone. And how could it be otherwise: cracks in the walls, falling off plaster and other “little things” not only testify to the dilapidation of the living quarters, but also simply depress their appearance. Therefore, combat readiness number one is the first thing you need for a fearless start to this exciting process. And the result will surely please you. Imagine, the walls will become even, you will pick up the finish - as you entered a new house! In addition, they could and did everything with their own hands. Double respect (respect, of course). Now you can rest and enjoy. Remember, the hobbits said: "We sit on the field of victory and eat its well-deserved fruits!" Although you can not remember the quotes. It is important that you really succeed in the planned serious business. Good luck!

Repair of cinder walls in the house outside and inside - what can happen to cinder concrete walls?

Slag wall repair. Detailed instructions for repairing slag walls, the necessary tools, skills, useful tips and secrets..

A country house starts with a foundation
First of all, I had to dig a trench under the foundation. The soil was clay, and the dimensions of the trench turned out to be small: 50 cm wide and 50 cm deep.

The foundation decided to make a tape filling of brick fragments up to 7 cm in size (note that the brick rubble must be clean, without dust and fine crumbs). The entire country house was built on clean water.

River sand was poured into the bottom of the trench in an even layer (layer thickness 15-20 mm). He laid brick halves on the sand with gaps of 3-5 mm, and poured prepared brick rubble on top with a layer 10 cm thick (Fig. 2).

In an oblong box, I prepared a dry mixture of cement and sand in a ratio of 1:5 (by volume). Before preparing the mortar, cement and sand were always thoroughly mixed in dry form until a homogeneous mixture was formed.

Since sand and cement in the solution quickly settle, the foundation was poured from a bucket. That is, first, a dry solution (1/2 bucket) was poured into the bucket, and at the edge of the trench, while stirring the mixture, water was added to the bucket to the top. Having prepared the solution, immediately poured the entire bucket onto the rubble. In this case, the entire solution must pass through the rubble. If a slide is formed from the top of the solution, then the solution is thick. It is necessary to pour the mortar from the bucket not in one place, but along the perimeter of the entire foundation after 30-40 cm to ensure uniformity of pouring. After the first layer is completely poured, it would be nice to put at least one thread of thick wire in the middle of the trench around the entire perimeter. I myself laid thin heating pipes as reinforcement.

It would be nice to pour the entire foundation flush with the ground in one day. When filling the trench with mortar, I laid it in three layers. In the upper layer, 5-10 cm from the surface, one more reinforcement was provided. Do not forget, of course, to check the “horizontality” of the foundation in terms of level, spirit level, etc.
On the outside of the house, he made an overlap with two whole bricks, thereby expanding the foundation by 10 cm. That is, now its width has become 60 cm, and the height of the foundation is increased by 2 brick thicknesses. Now, from the inside of the foundation, we will strengthen the formwork board and fill the gap between the bricks and the formwork with slag-sand-cement concrete. Concrete components (slag, sand, cement) are taken in the ratio 6:1:1. I recommend dosing the components of the solution in buckets.

First, cement should be well mixed with sand, and then this mixture should be mixed with slag. Water is added to the concrete depending on the moisture content of the sand and slag, but keep in mind that the solution (do not forget to do the latter!) Should not be liquid and could be rammed.
Having poured concrete into the foundation formwork flush with the upper overlap brick, from above we make an even screed of cement mortar 10-15 mm thick. When preparing a mortar for screed, 4-5 parts of sand are taken for 1 part of cement.

After 2-3 days, waterproofing can be laid on top of the screed, for example, from roofing material (preferably with one continuous tape without breaks). If you still have to join the ends, you need to do this with an overlap so that the ends of the roofing material overlap each other by at least 50-60 cm. The best waterproofing is obtained from roofing material or roofing felt laid on hot bitumen, that is, a layer of heated bitumen is applied to the concrete screed , and roofing material is laid on the bitumen. It is more reliable, of course, to stick another one on the first layer of roofing material using the same bitumen. The sides of the roofing material must necessarily hang from the sides of the foundation by at least 5 cm.

plinth
So the foundation is complete. Now the plinth part is next (Fig. 3). Like the above-ground part of the foundation, we make the outer side of the basement with brick lining, which can be folded from uneven halves, of course, laying them with irregularities inward, which will improve their bonding with concrete. The height of the base is usually made 60-75 cm.

Note that the higher the base, the better the underground will be ventilated. Of course, before starting the construction of the basement, it is necessary to lay a cement screed 5-10 cm thick on the waterproofing of the foundation. Be sure to provide windows in the basement to ventilate the underground. During concreting, meshes (wire or made of reinforcement) can be fixed in the windows. At the top of the basement, as well as on the foundation, a cement screed is made, waterproofing is laid with skillful hands and again a cement screed, which is carefully leveled with a trowel. The composition of cinder concrete for the basement is the same as for the upper part of the foundation.

Walls
First of all, for future walls, it is necessary to build a formwork from wooden panels 40-45 cm high (Fig. 4). Racks holding shields, it is better to dig into the ground. The distance between the posts, of course, depends on the thickness of the boards in the formwork panels and on the width of the walls (do not forget 5 cm for the gap). The main requirement for the formwork is that when tamping its boards do not bend, which will become clear during the first tamping together with the backfill.

Racks from above are knocked down with planks, but shields can also be fastened. The sides are fixed with wedges driven between the shields and racks into the gap, which is also necessary for more convenient removal and installation of the shields in another place.

As a rule, the walls of houses are usually made of monolithic concrete, but due to the lack of cement, the author decided to experiment and built walls of slag-cement concrete not solid, but with channels.

But it is better, in general, country houses made of slag-lime-cement concrete. Lime does not dampen the walls, and they will be warmer. If there is not enough lime, you can limit yourself to lime concrete from waterproofing to windows. In principle, slag-lime-cement concrete can be made up of components taken in a ratio of 10:1:1 (by volume).

Slaked lime should be filtered through a metal fine mesh so that there are no lumps, and diluted with water so that the concrete composition is better mixed. It is more convenient to add water little by little with a watering can.

But back to the walls. The author concreted the country house with just two shields, so a lot of formwork material was not required, and it is easy to work with such shields. After the formwork (shields) is installed, the concrete is first spread in a continuous layer 10-12 cm thick over the cement screed and compacted. Then, on this layer at a distance of 10-15 cm from the shield, a piece of plywood or thick rigid tin 35-40 cm high, 50 cm long is placed (Fig. 5). The gap between the shield and plywood is carefully filled with concrete. The layer should be of such a height that, neatly compacted, it does not collapse if the plywood is removed. You can fill the free space between the plywood and the shield with backfill, and then, carefully removing the plywood, repeat the operation at the opposite shield, but the backfill should already be done flush with the layer of already laid concrete. During work, make sure that the backfill does not fall into the concrete.

In the walls, every 30-50 cm, transverse partitions 10-15 cm wide are made. The coincidence of the partitions is not necessary. The resulting square voids are covered with fine slag, preferably from non-coking coals, expanded clay.

To form voids, it is convenient to use a special plywood box with slightly sloping walls, so that the box can be easily removed from the wall after pouring concrete (Fig. 6).

The corners of the house are monolithic - 50X50 cm. In the doorway, the thickness of the walls is 25 cm, in the windows - like the walls.
To decorate windows with platbands, you will need additional formwork (Fig. 7), consisting of two vertical boards (a distance equal to the width of the brick is provided between the boards). With the help of this formwork, bricks were strengthened in the sides of the platbands, which, protruding from the wall, form a kind of platband, giving the window an elegant look. So, a spacer 65 mm high and equal to the thickness of the formwork board is placed on a brick window sill in the gap between the formwork boards.

Two halves of bricks are installed on the spacer in the space between the boards (dry), then the spacer and the whole brick are placed on them again. There is again a spacer on it, halves of a brick, etc.

The bricks are inserted during the concreting process, whereby the mortar being laid presses them against the board, which is nailed to the outer sides of the supplementary formwork boards.

The bottom of the window sill is made like the basement of the house.

The overlapping of window and door openings is carried out with monolithic lintels, for which formwork is made in the form of a box. At the bottom of the formwork, so that water does not flow out of it, a plastic film, roofing material, glassine is underlain. It is necessary to lay wire reinforcement in the lintels (5-6 pieces), the ends of the reinforcement should be bent and go into the piers by at least 25-30 cm. The height of the lintels is 12-15 cm. Concrete is prepared on sand.

The cornice is laid with brick lining, like a plinth.

Under the ceiling beams - matrices, a platform of slag-sand-cement concrete (6: 1: 1) with a thickness of 10-12 cm is laid out (Fig. 8). A strapping of logs is placed on the beams, into which the rafters are cut.

The use of slag in the construction of the foundation is due to the savings in material resources. But it must be remembered that such a design, due to its features, may not meet expectations. As a result, the cost of restoring the house will significantly exceed the amount needed to build a quality foundation. Experts do not recommend the use of slag in the construction of the underground part of residential buildings. It is allowed to resort to such a method as a last resort or when constructing insignificant objects, such as sheds, garages, summer kitchens and other outbuildings. Although one should not ignore the fact that many owners of houses built on slag during a period of general shortage 20-25 years ago claim that they have not encountered problems over the years.

Material specificity

It is quite difficult to predict what strength the slag foundation will have, since no one determines the exact proportions of the components found in the waste of metallurgical enterprises. In one brought batch of bulk material, there may be heterogeneity associated with an unequal amount of metal and cement crumb residues, or other inclusions. This fact affects the fact that under the same operating conditions, and even under the same house, the erected foundation can behave in completely different ways.

In addition, the regulations do not describe the algorithm for calculating the slag foundation, as well as a clear technology for its laying. Masters are guided by their own experience or tips from friends. But this does not always lead to positive results.

Slag from exposure to water can be destroyed, so it should not be used on a building site with a high level of groundwater. For the same reason, a foundation erected on dry ground requires enhanced waterproofing, but already to protect it from rain and melt water. In addition, care should be taken in advance about the drainage system that removes moisture from the underground structure in order to avoid the formation of stagnant processes.

The bearing capacity of the slag foundation has an insufficient indicator required to hold capital houses, although there are many cases of its successful construction under summer cottages and relatively light residential buildings.

The use of slag in the construction of foundations is strictly not allowed in seismically active regions. There is no doubt that the underground structure will not withstand the jerky movements of the soil and will collapse. For territories included in the risk zone due to possible earthquakes, specific constructive construction schemes are provided.

Which slag to choose

Single types of slags are suitable for building foundations. Their properties are determined depending on several components, the main of which are:

• chemical composition;
• cooling mode;
• primary processing;
• grain size.

Slags are formed during the smelting of ferrous or non-ferrous metals, as a result of fuel combustion at thermal power plants, in the production of fertilizers, in particular phosphate fertilizers, etc. From the specifics of the production in which the material was obtained, its chemical composition and the proportions of the components are formed. Foundations are laid from heavy dump slag A formed in metallurgical or steel mills.

Industrial waste generated at thermal power plants or chemical industry enterprises is not allowed to be used.

The approximate composition of the slag can be judged by its color. For example, a gray tint indicates the presence of cement, greenish or black is obtained during the smelting of non-ferrous metals, and bluish indicates the presence of manganese inclusions. The external assessment of slag is also made according to the size of the grains and the number of large pieces. The structure of the material should be crumbly, and the fraction should be less than 5 mm. When pouring water, small particles contribute to a better compaction of the slag, which reduces the porosity of the future construction of the foundation block.

Slag with an admixture of cement, subjected to repeated processing, loses the ability to set and solidify due to the maximum loss of the binder component. For this reason, a monolith will never work out of it. Ideally, the slag should contain about a third of the cement dust, which is important for the correct hardening of the compacted mass.

When constructing foundations, it is recommended to use hot slag, or rather warm, but still smoking. It is from such material that structures with good bearing capacity are obtained. "Fresh" slag has a crumbly structure without the presence of lumps, which is the best solution.

If it is necessary to store the slag outdoors, it must be remembered that under the influence of rain or high humidity, the material begins to harden. The top crust can be quite strong, and it will require a lot of force to break it up in order to release some of the usable material. Therefore, the slag brought and poured for the time being should be protected from moisture before the start of the working process.

Slag foundation device

Based on the foregoing, it can be noted that:

• heavy structures should not be erected on a slag foundation;
• the structure of the hardened slag along the perimeter of the tape may be inhomogeneous;
• the material must not be soaked before the start of work;
• picking up high-quality waste from metallurgical production, relying on external signs, is quite difficult;
• the finished structure is afraid of water, therefore it requires good waterproofing.

All these factors should be taken into account when building a slag foundation. But first of all, it is necessary to perform preparatory work, which consists in cleaning the site of foreign objects, removing the fertile layer and moving it to another place, marking, and digging a trench. For formwork, you will need to stock up on solid boards and nails, and to remove communications, cut pipes.

The depth of laying the foundation tape is taken depending on the freezing index of the soil. And they dig a trench, taking into account the device of a crushed stone pillow 30 cm thick. To ensure better stability of the underground structure, it is laid with mandatory compaction of the bottom of the excavation and layer-by-layer ramming of crushed stone.

To reduce the risk of destruction of the foundation due to soil movements, its deepening by at least 1.2 m will help. The height of the trench, in this case, will be at least 1.5 m.

The formwork box is knocked down on the basis that the width of the slag foundation should be at least 60 cm. In this case, the need to raise the shields above ground level by at least 25 cm should be taken into account. To strengthen the structure, internal and external spacers are installed on the box, and pieces of pipes are mounted at the outlets of communications.

An important point is the correct determination of the position of metal casings in a wooden box relative to sewer and water outlets. Failure to comply with this condition will subsequently lead to the need to punch the foundation tape, which is not permissible for a slag monolith.

At the bottom of the foundation, it is recommended to lay a knitted reinforcing mesh. It will allow the base to become a single whole and help to distribute the loads more evenly. For its manufacture, reinforcing bars with a variable cross section are used, treated with an anti-corrosion compound to avoid the appearance of metal rusting processes. In the body of the slag foundation, the frame is not installed in order to improve the compaction of bulk material.

Ribbon Formation

The most important stage in the construction of the foundation is the correct backfilling of the slag into the trench and careful compaction of the laid layers.

• The first condition is that the thickness of the lower and middle layers should be 20-25 cm, and the upper ones can be increased by 5 cm.
• The second condition is a plentiful spillage of water or cement milk of each layer. The liquid is selected depending on the content of binder components in the slag.
• The third condition is conscientious ramming of all layers without exception.
• The fourth condition is the installation of an upper reinforced belt, which ensures a strong connection between the underground and ground parts of the structure.

Impregnation of the slag with water guarantees the best quality of the rammer, which contributes to the compaction of the porous structure of the material. The result is a fairly strong adhesion of the particles. Some craftsmen suggest, in the case of a low cement content in the slag, pour the binder component directly into the trench, mixed with waste from metallurgical production. Others advise using cement milk instead of water. Surely both methods have the right to exist.

After laying and compacting each layer, a break is taken for about an hour in order for the process of cement setting to begin. Then proceed to backfill the next layer.

Without waiting for the last layer of slag to set, a reinforcing mesh is laid on it with the lower rods buried in the backfilled foundation. After that, the structure is left for about 12-16 hours. At the last stage, an upper concrete belt with a thickness of at least 20-30 cm is performed. To do this, the concrete mixture is poured into the formwork to the design mark with mandatory tamping.

Protection device

At the end of the curing process of the underground structure, they proceed to its waterproofing. It should be understood that the durability and reliability of the slag foundation will depend on the quality of protection. It has a porous structure and is quickly saturated with moisture, so insulation work must be approached responsibly.

For accurate removal of the formwork and obtaining free access to the surface of the structure, it is required to clear the area around its perimeter. This is done when the slopes are too close to the foundation. If there is enough space, you can skip this preparatory step.

• plasters - helps to compensate for the porosity of surfaces, closes microcracks and closes sinks;
• liquid rubber - creates an impervious, water-repellent layer, evenly distributed by spraying.

Without additional protection, plaster will not be able to guarantee complete water tightness, as it has the ability to crack.

In addition to vertical protection, two horizontal layers of waterproofing should be provided. The first of them is carried out before filling the slag, and the second is placed between the upper concrete belt and the wall. For their device, in both cases, rolled materials are used, the reliability of which is ensured by bituminous mastic. It must be remembered that the joining of vertical and horizontal waterproofing must be airtight.

After the construction of the foundation part, it should not be immediately loaded with a ground superstructure. The optimal period of "rest" of the structure is at least six months.