Slag concrete: composition and proportions, material density and DIY production, recommendations for selection

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Cinder block

Slag concrete, as well as products made from it, are a budget building material, and at the same time, its performance meets all construction standards. Due to a number of advantages, the material is actively used in private housing construction. The interest of developers is only increasing every year, and in this article we will understand the reasons for this popularity.

Should I choose cinder block? Set of advantages and disadvantages

Positive qualities of the material

Main disadvantages

Manufacturing Process Overview

Equipment and raw materials

Production Process Stages

Is it worth making your own cinder block?

Calculation of mortar composition for masonry work

Finally

Slag concrete and slag-alkaline concrete: composition, use and advantages

Cinder concrete is lighter than regular gravel-fill concrete and is often used in low-rise construction.
It is a mixture of filler - metallurgical and fuel slags - and a binding agent. Walls made of slag concrete are strong, durable, sound insulating and heat resistant. This type of concrete may contain an alkaline component and then it is called slag-alkaline concrete. Alkaline activation of the slags used occurs by adding lime, caustic or soda ash, sodium metasilicate, liquid glass and other alkalis. Slag-alkaline concrete has very high strength, as well as high frost resistance and water resistance.

As a binding agent in the preparation of this type of concrete, you can use a large number of different binding materials - cement, clay, gypsum, lime. Which one will be used depends on the calculated load on the walls. The strongest walls are made from cinder concrete and cement. The next strongest material is lime-based slag concrete.

The choice of binding agent is not the only parameter that should be considered. The size of the slag stone should also be taken into account. As a rule, two types are used - small (fraction less than 0.5–1.5 mm) and large (20–30 mm). The fine fraction produces heavy and durable concrete with a high thermal conductivity coefficient. The inclusion of large fractions, on the contrary, produces lighter but less durable slag concrete with high thermal insulation properties. It is undesirable to use fractions larger than 6 mm - this significantly reduces the strength of slag concrete.

How to obtain different fractions of slag? To do this, it is necessary to use two sieves - one with a cell diameter of 40x40 mm, and the diameter of the other should be 5x5 mm. At the first stage, the filler is sifted through a sieve with large cells. Then through a fine sieve. When preparing concrete for external walls, small and large granules are mixed in a ratio of 3:7. For internal walls, the number of small fractions can be increased by one. To make the strength higher, 20% of the finest fraction should be replaced with sand, completely eliminating granules larger than 10-12 mm.

How to prepare cinder concrete

The sequence of steps for preparing slag concrete with your own hands is the same as when making ordinary concrete with gravel filler.

A few hours before preparing the slag concrete mixture, it is advisable to moisten the slag. This further increases the strength of the product. Cement tends to clog all the roughness and irregularities on the surface of the slag, thereby weakening the binder, and this can ultimately lead to a weakening of the strength of the future product.
Mix slag granules according to the technology indicated above.
It is better to replace too fine, dusty slag that passes through a fine sieve with ordinary sand.
After this, a binder is added. The cost of slag concrete can be reduced if two types of binders are used. For example, combine cement with clay or lime in a 3:1 ratio.
The addition of lime gives the mixture good plasticity and allows it to be mixed properly - until a uniform color is obtained. It must be borne in mind that the process of mixing the slag concrete mass plays a big role in its quality and affects the load-bearing capacity of the product. When making slag concrete yourself at home, mix the mass with a rake.
Typically, medium-grade slag concrete includes from 4 to 5 parts of a mixture of two types of slag and two parts each of sand and a binding agent.
The resulting slag concrete mass should be thoroughly mixed.
Add water and mix thoroughly again. The result should be a homogeneous mass.
After this, the cinder concrete is ready for filling into the formwork. The finished mixture must be worked out within 1 hour, but no later than 1.5 hours after mixing.

The use of slag concrete in the construction of walls

The construction of walls made of slag concrete can be implemented in two ways: to erect monolithic infill walls or to make slag concrete blocks, from which the wall will be later installed.
The first approach is more labor-intensive, but requires less time. With the second approach, there is no need for formwork work, due to which it requires less labor, but is somewhat longer in time. Option 1 – printed walls. They can be made either monolithic or hollow. The use of void formation technology reduces the load on the foundation and reduces the thermal conductivity of the walls.

To make hollow walls, special liners made of wood, hardboard or metal are installed in the space intended for concreting. Before pouring concrete, the liners are lubricated with machine oil, grease, or wrapped in parchment, roofing felt or roofing felt. You can also take thick cardboard and make cone-shaped pipes from it, which you can then use to form voids. In this case, there is no need for subsequent excavation.

When the concrete dries and settles, the resulting voids should be filled with dry slag, sand, foam granules or other insulating material. A cinder concrete wall turns out to be quite heavy and shrinks well, so it must be reinforced with an iron rod 7–10 mm in diameter - at least 3 rods for the width of the wall and 4–5 for the height.

In those places where the project will have to install window and door openings, during the pouring process it is necessary to insert wooden blocks to which windows and doors will be attached in the future.

The slag concrete mixture should be laid in layers, every 15 to a maximum of 20 cm. When the layer is laid, it must be carefully pinned using a metal rod. This is especially important where the concrete comes into contact with the formwork or inlay. In order to ensure proper settlement, the cinder concrete layer is compacted with a special tamper. After this, the next layer is laid. The entire wall is filled in the same way.

When the slag concrete work is completed and the walls have “set”, the concrete, if it was prepared using cement as a binder, should be watered. This will ensure the strength and durability of the future structure. For slag concrete based on other binders, filling with water, on the contrary, is undesirable. To avoid drying out, they only need light moisture.

Fig.1. Formwork for walls made of cinder concrete (can also be used for ordinary concrete)

Elements: 1 – base; 2 – internal covering (roofing felt or other material); 3 – wedges; 4 – spacer; 5 – racks and 6 – side shields.

Option 2 – cinder blocks. To make them, you will need special molds. The dimensions of the block may vary, and the materials used to create liners and shapes can be the same as for pressed walls.

During the molding and pouring process, the mixture must be thoroughly compacted. After about 3-4 hours, when initial setting occurs, the blocks can be released from the mold and laid to dry. Drying should be done in a well-ventilated place that does not allow direct sunlight, for example, in a utility room, or at least in the shade of a tree. During the first week, while the cinder blocks are drying, if the weather is dry, they should be moistened. When the cinder blocks have hardened sufficiently, they can be stacked in layers up to 150 cm. After complete drying, the blocks are ready for use. As for the technology for laying cinder concrete blocks, it is the same as laying other types of concrete blocks. And the solution is suitable from any binders - lime, cement-lime, clay or cement-clay.

Cinder blocks have the following classification:

Hollow cinder blocks are used for the construction of partitions and walls. Blocks with a hollowness of 40% are the least durable, but the most thermally conductive. They are used for insulation together with more durable materials, as well as in the construction of buildings with a metal frame. 30% hollowness gives a good combination of thermal conductivity and strength - such blocks are the most popular in construction.

According to their intended purpose, cinder blocks have the following classification:

Production technology: manufacturing methods

Pressing

To give the material a marketable appearance and cinder concrete to gain specific strength, forms are used that come in two types: blind and through (without a bottom). The product obtains its mechanical features and proportions through specific processing.

This method requires the use of the necessary equipment.
The pressing process consists of compacting the material using special pressing equipment. The already prepared and hardened material (not yet strengthened) is placed in a space-constrained form, where it is subject to the final compaction procedure. Enterprises specializing in the production of slag concrete have automated presses that process several tons of material in one go. The technical organization of a monolithic and hollow block is similar.

Vibrocompression process

Special forms are filled with moving mass. In large-scale and well-equipped workshops, the procedure is mechanized. The essence of vibrocompression is high-quality compaction of products, active adhesion of mass to matrices, until the end of the procedure and release of the finished material. One set of training lasts 1-1.5 minutes. Vibration frequency - 60 Hz. In less developed enterprises, the process is mechanized and the equipment is operated by workers equipped with vibrating tables and hand-held electric vibrators.

Molding: distribution

Forms can be filled in with material manually.
There are two types of disassembly of material into matrices:

Automatic. Using special equipment.
Mechanical. It is carried out manually.

Forms for filling:

wooden;
metal;
polyurethane.

A distinction is made between individual matrices, such as individual elements for a material, and cell matrices. Before distributing the slag concrete mass to the formation sites, each matrix is coated with a special lubricant. If decorative slag concrete is made, the bottom of the mold is covered with plaster mixture. When the cells are prepared, the filling stage begins. The slag concrete mixture is poured only to the middle of the mold, then the mass is compacted. Next comes a series of void formers, and only then the matrix is filled to the brim with the remaining solution. Then the prepared and deformed material is subjected to a pressing or vibration pressing process.

Cinder block strength grades

The strength grade of slag concrete blocks along with density are the main characteristics of the building material. To obtain high load-bearing capacity, it is better to use grades M25 or M35, M10 should be used only as insulation, and grades M50 and higher are already suitable for load-bearing walls.

Composition of slag concrete according to strength grades

Brand of cinder concrete	Material per 1 m3 of slag concrete, kg/l				Volumetric mass of slag concrete, kg/m3
Brand of cinder concrete	cement M400	lime or clay	sand	slag	Volumetric mass of slag concrete, kg/m3
M10	50/45	50/35	100/60	700/1000	900
M25	100/90	50/35	200/125	700/900	1050
M35	150/135	50/35	300/190	700/800	1200
M50	200/180	50/35	400/250	700/700	1350

wall in the ground tender

The process of making cinder blocks with your own hands on video

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Should I choose cinder block? Set of advantages and disadvantages

Are you still in doubt and can’t decide: should you use this particular material when building your own home? Let's analyze the main pros and cons of the material, which will certainly help you make the right choice.

Positive qualities of the material

Let's start with the positive aspects:

The material has a fairly good ability to retain heat, given its density indicators;
The strength of the products allows the blocks to be used in various branches of construction;
Frost resistance of products is usually high;
The range of blocks and other cinder concrete products is very wide;
The durability of the material leaves no doubt;
Cinder blocks are easy to handle and have relatively large dimensions, which simplifies the construction process;
Fire resistance is also an important plus;
Biological resistance;
The low price makes cinder block as affordable as possible;
Ability for sound insulation and vapor permeation;
You can make cinder blocks with your own hands and thereby reduce the cost of materials. Below are instructions containing information on how to make the material at home.

Characteristics of slag concrete in comparison with its main competitors

Main disadvantages

The shrinkage of the material does not allow finishing to begin immediately;
It takes a relatively long time to achieve brand strength of a product;
When making a block, it must be constantly monitored. For example, it is necessary to periodically wet the products to prevent them from cracking;
The external qualities of ordinary products are not entirely good;
Durable products have too much weight and thermal conductivity, which forces developers, when using them, to carry out intensive insulation;
Another disadvantage is that cinder concrete walls are extremely hygroscopic. That is why the finishing must be planned in advance and executed technically correctly, taking into account the fact that the block needs protection.

Cinder concrete walls

Home » Materials » Slag concrete - features and characteristics of the material

October 28, 2014 No comments

The material for forming building structures must be not only durable, but also economical. It is desirable to use recycled materials from other industries for construction needs. For our latitudes with harsh winters, the insulating properties of the material are extremely important. Slag concrete has all of the above features .

Its characteristics allow the products to be used for both load-bearing and enclosing elements. It all depends on the ratio of the proportions of the substances included in it.

Slag concrete - composition and proportions

The name of the material is determined by the presence in its composition of fuel slag or waste from the metallurgical industry. The grain size of the slag ranges from 2.5 mm to 8 mm. Slag dust is also used for better adhesion of materials. The grains are sifted out using a sieve. Dust masses are sifted in the same way.

Thanks to the lightness and porosity of the filler, the structure is lightweight and has increased thermal insulation properties.

Before adding to the solution, the slag must be moistened with water. This is due to the high porosity of the material. If the slag is dry, it will adhere less well to the concrete, leaving pores filled with air. Such design flaws will reduce its strength. It takes almost 80 liters of water to wet 1m3 of slag product. If the slag is wetted by rain, additional wetting is not necessary.

Cinder concrete also contains lime. It can be slaked or not slaked. Slaked lime must be diluted with water to the consistency of milk before adding to the solution. The mass of lime is 1/3 of the volume of slag products. For greater strength, 2/3 clay is added to the solution. This composition takes longer to gain strength, but its strength characteristics increase.

The water used to dilute the mixture must be free of organic impurities. The chemical composition of water, with unacceptable impurities, can react with other components, leading to undesirable consequences. Water consumption per 1m3 of slag concrete is approximately 200 liters. This amount includes the liquid with which the lime is diluted and the water added to the slag.

The grade of cement is determined by the operation of the structure and the requirements for it. The dose of cement in the solution is 2/3 of the volumetric weight of the slag.

Characteristics: pros and cons

Builders consider the low cost to be an undeniable advantage of the material: slag concrete is much cheaper than foam concrete or aerated concrete. For the construction of the foundation and load-bearing walls, professionals recommend using expanded clay concrete blocks or a product with lime admixtures. Positive characteristics of slag concrete:

Convenient proportion. Large sizes ensure quick laying and save time on specified work.
Easy to use. They are attached to ordinary cement mortar and do not require special skills.
Thermal insulation properties. Due to its low thermal conductivity, it ensures the preservation of existing heat.
Environmental friendliness. Does not contain radioactive or toxic substances. Harmless to others.
Fireproof qualities. Cinder concrete does not burn and does not contribute to the spread of fire.

There are also disadvantages of construction with granulated slag:

A building made from this material requires mandatory cladding.

low level of sound insulation;
poor thermal conductivity;
the importance of surface finishing;
low resistance to moisture;
minimum endurance of power loads.

Cinder concrete walls

Cinder concrete walls are erected in formwork. Binding materials can be cement, lime, gypsum or clay. In order to reduce cement consumption, it is better to use a mixed binder (cement with lime or clay). The compositions of slag concrete are given in table. 1.

Table 1. Recommended compositions of cinder concrete mixture (in parts by volume)

The slag must be clean, not contaminated with foreign impurities - rags, wood chips, metal inclusions, etc. The amount of fireproof coal contained in the slag should not exceed 10...20%.

Before preparing concrete, the slags should be sifted, dividing them according to particle size. First, pieces larger than 80 mm are separated from the total mass of slag for subsequent crushing; the remaining slag is scattered on sieves with cells of 40x40, 5x5 and 1x1 mm. Slag grains larger than 1 mm should be mixed with the slag remaining on a sieve with mesh 5x5 mm. Thus, two types of slag are obtained: large (40 mm) and small (1...5 mm). The mixture consists of 60 - 70% coarse and 30...40% fine slag.

The slag concrete mixture is prepared during mass construction in concrete and mortar mixers; during individual construction, it is prepared manually, by shoveling the materials on a plank floor (beater) until a homogeneous composition is obtained.

For ease of installation and to increase the strength of slag concrete, it is recommended to moisten the slag several hours before preparing the concrete mixture. In total, 250...350 liters of water are required to prepare 1 m³ of slag concrete.

Laying the slag concrete mixture into the formwork is carried out immediately after its preparation in horizontal layers no more than 20 cm thick with careful compaction, especially in the corners of the house and in the places where the internal walls adjoin the external ones. The mixture is compacted by tamping or (in the case of mass construction) with special mechanisms - vibrators.

To avoid over-drying of the concrete, it is recommended to water the walls made of cinder concrete for 10 days, cover them with wet matting, straw mats, etc. When using gypsum, lime or clay as a binder, the walls should be covered only in case of strong wind (to slow down drying process of the surface layer). Accelerated drying of the surface of such walls leads to the formation of cracks. Slag-filled walls are erected in adjustable formwork, consisting of horizontal panels and racks (Fig. 1).

Rice. 1. Formwork design for the construction of monolithic walls:

a, b - with horizontal and vertical shields; 1 - twisted wire; 2 — shield; 3 - spacer; 4 - wall filler; 5 - vertical beam; 6 - horizontal contraction; 7 - metal rod (dimensions in cm)

Before installing the formwork, on the outer corners of the house, racks of two thick boards, knocked down at right angles to each other, are installed at the entire height of the future wall. The racks must be installed strictly plumb and securely secured using struts. Shields are installed between the posts around the perimeter of the house, marking their exact position on the edge of the foundation. The distance between the ends of the outer panels and the corners of the future walls is sewn up with scraps of boards of the same thickness as the boards. In order not to spoil the board bars by driving nails and not to make it difficult to remove the boards, additional racks are installed next to the end of the last boards, to which the corner sheathing boards are nailed. On the inside, quarter posts are installed in the corners, sheathing is nailed to them, and the outer posts are tied together with wire ties.

The posts and corner cladding are not removed until concreting is completed to the full height of the wall. The panels can be removed and rearranged only after the laid cinder concrete has been kept in the formwork for 2…3 days. To reduce the number of formwork panels, the house can be divided horizontally into two sections, concreted sequentially. The vertical edge of the wall at the junction of the grips should be made in the form of ledges.

Door frames are installed before the formwork panels are installed; window - as the walls are erected, but not earlier than 3...4 hours after laying the last layer of concrete, which serves as the base of the boxes.

When building an individual house, boards are usually used 2…3 times. In this case, they should be made from boards 1.9 cm thick. When building a village of houses of the same type, concreting the walls can be organized sequentially in order to use the same panels on several houses. In this case, to make boards, you should take boards 2.5...4 cm thick. If handled carefully, such boards can be used more than 5 times, which will significantly reduce the cost of the formwork. It is also possible to use lime-sand concrete, which consists of a mixture of lime, aggregate and water. River, mountain or ravine sand serves as fine aggregate; coarse aggregates are gravel, crushed stone, and broken bricks. Walls made of lime-sand concrete do not need to be plastered on the outside. The inside is grouted for painting or wallpapering.

Slag concrete - technical characteristics

The main difference between cinder concrete and ordinary concrete with sand and gravel aggregate is its lightness. This reduces the load on the building foundation, allowing you to save on materials.

fine for building façade

Cinder blocks are easy to install and come in a variety of sizes and shapes. Since cinder concrete is mainly prepared at the construction site, the formwork for it is made there.

Porous filler allows you to increase the noise absorption of the structure. In addition, hollow blocks for walls and partitions are produced. They provide greater heat retention and keep out noise. The service life of slag concrete structures is 100 years, which is longer than many building materials.

Depending on the grade of cement and the addition of plasticizers, the frost resistance of the structure is determined. For external walls, the number of defrosting cycles is at least 35, for the north - at least 50.

Slag concrete structures are highly hygroscopic. It is necessary to pay close attention to the waterproofing of this product. But walls made of this material “breathe” without creating an obstacle to vapors. Slag concrete produced in a factory has a quality certificate and meets all specifications. Blocks cast on a construction site are cheaper, but determining their performance and shelf life is quite difficult.

Source

Disadvantages of cinder blocks

Like any building material, cinder concrete also has its disadvantages:

reluctant to keep warm;
requires quite a lot of time to harden;
full compliance with the characteristics required for a given brand occurs only after a year - 4 months after production, the finished block has only 50% of the strength of its intended potential;
Compared to heavy types of concrete, slag concrete has a higher hygroscopicity and therefore requires careful care within a few days after production.

On the other hand, if proper production and maintenance are followed, it becomes a durable building material with low cost.

Composition of slag concrete

To make slag concrete, fuel slag is used as a filler, and in the presence of metallurgical production, metallurgical slag is used. Slag, being very light (compared to crushed stone), has quite good strength indicators. Its cost price is approximately two times cheaper than clay brick, and its thermal conductivity is significantly superior to it. If technology is not violated during the work, slag concrete structures can last quite a long time - at least 50 years.

Most often, slag resulting from burning coal is used to make concrete, because They are more often found on the farm than metallurgical ones, but in terms of strength characteristics they are much weaker. The best slags among fuels are those obtained from the combustion of anthracite. They are the most durable and resistant. The slag resulting from the combustion of brown coal and coal near Moscow contains a large amount of impurities, which is why it is better not to use it in construction work. The slag produced during the combustion of other types of coal has intermediate qualities and can be used in construction. When choosing slag for preparing concrete, one should not allow the presence of impurities (clay, garbage, ash, etc.). The presence of unfired clay particles must be minimized. For this purpose, the slag is kept outside for at least one year to be washed with rainwater.

The strength and thermal conductivity of slag concrete are directly affected by the granulometric composition. Concrete must have a certain percentage composition of large and small granules (particles). When the percentage of large particles in concrete is very high, this significantly reduces its strength qualities and thermal conductivity, and the presence of small particles improves these qualities.

For the construction of external walls, slag with a predominance of large particles is always used, and internal walls are built from slag concrete with a predominance of small particles. The size of concrete particles for internal walls should not exceed 10 mm.

Manufacturing Process Overview

How to make cinder block products correctly? Let's look at the technology step by step, and start with a review of the necessary equipment and material.

Equipment and raw materials

To begin the release process, it is recommended to purchase the following equipment:

Vibropress;
Concrete mixer;
Forms for products.

You can also use a mini-installation for the production of slag concrete blocks. With its help, production volume may increase slightly.

Stationary plant lines are the most powerful and automated, however, for a single production of cinder blocks, these are unjustified costs, since even used equipment of this type costs a lot.

Stationary cinder block production line

On a note! Large enterprises even use a conveyor type of equipment, which allows them to produce up to 300 m3 per day. This kit is distinguished by full automation and an extremely high price.

You can make a vibrating press or machine yourself.

When purchasing raw materials, consider the following:

Do not buy expired raw materials or materials with questionable consistency, which primarily concerns cement. There should be no lumps in it.
Try to find suppliers who can offer you everything you need right away. This will help you save on shipping. Additionally, you may be given a significant discount based on the volume of your purchase.

Production Process Stages

The first step is to mix the solution.
You must first prepare the slag. It is sifted, divided into 2 fractions: larger and smaller. As a rule, there should be at least twice as much fine fraction in the composition, this will help increase the strength of future products.
Slag is often soaked in water, which helps increase density. It would also be a good idea to add alkali, which will reduce the level of water absorption.
First, two fractions of slag are mixed, then the remaining components are added.
After obtaining a homogeneous consistency, you can begin molding.
Processing the mixture using a vibrating press will contribute to better compaction of concrete, which will also increase the strength of the future material.
After partial hardening, the block can be removed from the mold.
The last step will be drying the products.

Is it worth making your own cinder block?

Let's analyze:

Factory cinder block, as a rule, has better geometry, since it is cut automatically using a cutting complex. As a result, the masonry will be thinner, and, therefore, the thermal efficiency of the structure will be higher.
Do-it-yourself blocks are of very dubious quality, because the properties of such products are not checked by anyone, and the production process is controlled only by the developer himself.
Factory-produced products, as a rule, undergo testing, after which a quality certificate is issued confirming the product’s compliance with all established standards.
Home release will take a lot of time and effort. The process is labor-intensive.

Example of a block test report

Note! The only advantage of self-production is significant savings, but only if you managed to purchase raw materials and equipment at an affordable price. Moreover, no one is immune from the manufacture of defective products, especially at the initial stages of mastering the technology. And these are additional costs. That is why you first need to carefully weigh the pros and cons.

Slag concrete - composition and proportions

Thanks to the lightness and porosity of the filler, the structure is lightweight and has increased thermal insulation properties.

The grade of cement is determined by the operation of the structure and the requirements for it. The dose of cement in the solution is 2/3 of the volumetric weight of the slag.

Production of slag concrete

When making slag concrete, the binder is traditional cement, to which lime or clay is added. Thanks to the use of additives, cement consumption is reduced and the resulting concrete is more plastic.

The technology for preparing slag concrete is similar to the technology for preparing traditional concrete. First, the dry components are mixed: sand, cement and slag, after achieving a homogeneous composition, lime or clay diluted in water is added, and this mixture is diluted with the required amount of water and mixed. Do not forget that the time of use of such a mixture is limited to two hours.

Slag concrete: types, self-preparation of the solution

Slag concrete is widely used in private buildings due to a number of advantages and ease of working with the material. Due to the fact that the material is much lighter than ordinary concrete, its use reduces the load on the structure of the house while the thermal insulation properties are maintained at a fairly high level. Let's consider the main types of this group of products, their advantages and features of use.

Cinder concrete blocks have high performance properties

Overview of the main features of the material

To decide on the advisability of using such products, you need to know all the information about them in order to compare them with other options and draw the right conclusions (

Main varieties

After carefully studying the composition of slag concrete, proportions and characteristics, you need to understand the existing varieties of material that are available on the market. Cinder blocks can be hollow or solid.

The first type is light in weight because it contains voids. It is distinguished by increased thermal efficiency, but low density. Such blocks are indispensable in the construction of private houses, extensions, garages and other industrial structures.

Full-bodied products demonstrate increased density. However, this affects the weight and structural properties. One of the disadvantages of solid blocks is low thermal efficiency. In most cases, load-bearing structures for various purposes are created from such raw materials.

Depending on the purpose, slag concrete can be face or ordinary. The first type has one or 2 facing surfaces, and ordinary ones are used for basic masonry work.

As mentioned earlier, when choosing a composition, you can use various binder additives. The type of these components determines the brand and properties of the material:

SCC - contains a cement mixture.
SKSH - made from slag.
SKG - created on the basis of gypsum.
SKI - contains lime.

Structures can also be wall or partition. The latter type is characterized by a small diameter and is an indispensable element for arranging partitions. With its help, the foundations of buildings are often created.

Cinder blocks made of heavy and light components are widely used in the construction industry. By the way, lightweight concrete is often called “warm”. It is able to retain heat indoors, weighs relatively little, but cannot boast impressive density. Heavy structures have excellent strength characteristics and high weight. Their resistance to various impacts and loads is at a high level.

In addition to the traditional version, slag concrete can be offered in the form of slabs. Such designs deserve special attention, since they are characterized by many performance properties and advantages. They are created on the basis of slag concrete with a grade of at least M50. A steel mesh with cells of 10 by 10 centimeters is used as a reinforcing element. The role of the binding component is played by a cement mixture of a grade no less than M25.

Filling with slag concrete

To fill the walls of a building with cinder concrete, formwork with a height of no more than sixty centimeters is used. Panel formwork is used. The shields are attached to fixedly installed posts with a diameter of at least fifteen centimeters in increments of one and a half meters.

Pouring of slag concrete is carried out in layers of twenty centimeters with mandatory subsequent bayoneting and tamping. The formwork can be removed no earlier than after three days, but if the weather is dry and hot, then the period can be reduced to a day. Laid concrete needs maintenance. So, for ten days it is strictly forbidden for the concrete body to be exposed to direct rays of the sun, and in dry and hot weather it needs to be moistened from time to time.

Thermal conductivity of slag concrete

To increase thermal conductivity in walls under construction, it is allowed to create voids by filling them with foam pieces, old paper or even lighter concrete.

Do not forget that this method of increasing the thermal conductivity of walls weakens their strength. In this case, it is necessary to increase the strength of slag concrete.

Plastering work can only be carried out after twenty-eight days have passed from the moment the concrete was poured. To give the wall additional strength qualities and a more aesthetic appearance, you can line the walls with brick.

In order to speed up the process of constructing cinder concrete walls, you can use ready-made cinder concrete blocks, either self-made or factory-made. To make blocks, wooden collapsible molds are used. Drying time for blocks is approximately three weeks. Their use will reduce construction time and begin plastering work the next day after the completion of wall laying.

Cinder concrete walls are labor-intensive to construct, but they allow you to save money and remove unnecessary waste.

Light Concrete

The technology for preparing concrete using fuel and metallurgical slags is the same; with equal volumetric mass, their properties are the same.

For the least dense slag concrete (grade M10; 900 kg/m3), coarse slag is used (the ratio of coarse and fine slag is 4:1; the ratio of cement: lime: sand: slag is 1:0.8:1.2:20, this is the ratio according to volume). As the density of slag concrete increases, the ratio of coarse and fine slag falls, and the proportion of slag also decreases. For example, for a slag concrete density of 1350 kg/m3 (grade M50), the ratio of coarse and fine slag is 1:1, and in volumetric parts cement: lime: sand: slag is 1:0.2:1.4:4.

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One of the main conditions for obtaining a durable slag concrete wall with good thermal insulation is the ratio of large (0.5-5 cm) and small (0.01-0.5 cm) slag. If for external walls, where thermal insulation properties are very important, the ratio of fine and coarse slag should be chosen in the range of 3-4/5-7, then for partitions - internal walls made of slag concrete - this ratio changes, it is desirable to increase the content of fine slag. Often up to one quarter of the slag is replaced with sand.

The presence of clay particles, lumps of earth and unburnt coal in the slag negatively affects the quality of the finished concrete. Therefore, the slag must be kept in the open air for a year, ensuring the drainage of rainwater.

Rice. 1. Monolithic slag concrete wall 1. waterproofing layer; 2. gap used for wall settlement; 3. jumper; 4. gasket (tarred board with insulation)

How to prepare cinder concrete for walls? For this, first of all, two sieves are needed (with cells of about 5x5 cm, then 0.5x0.5 cm). The part of the slag that did not pass through the second sieve is coarse slag. Then the slag is moistened (about 300 liters of water per 1m3 of slag concrete). The slag must be placed within an hour from the moment of mixing. Sometimes gypsum is added to the mixture; in this case, lay the solution faster, no more than 10 minutes after its preparation.

As in the preparation of ordinary concrete, cement, sand and slag are mixed dry, then clay or lime dough is added. Sometimes, to reduce the thermal conductivity of walls, cement is not used at all, leaving lime and clay as binders. This composition is: slag - 0.7; lime - 0.1; clay - 0.2. This method must be used in the warm season, and rafters and ceilings on slag concrete walls can be installed 2-3 months after the walls are erected: cementless slag concrete takes a long time to set to the required strength.

Precast walls are made using adjustable formwork, with roofing material or, possibly, plastic film being nailed from the inside to well-fitted formwork boards. Otherwise, cement or lime milk will leak through the walls of the formwork.

Particular attention should be paid to the strength of the formwork for slag concrete and concrete walls (Fig. 2). Racks for fastening boards are installed at least every 1.5 m, they are fastened with struts, spacers are made inside the boards, wedges are made between the racks and boards, burnt wire is stuffed through the entire thickness of the walls, steel ties are used, etc.

Rice. 2. Formwork option for walls made of slag concrete or concrete 1. base; 2. covering made of roofing felt or other material; 3. wedges; 4. the gap between the shields; 5. Stoics; 6. shields

In some cases, cinder concrete walls are made hollow: liners are inserted into the concrete, after the solution has dried, they are removed, and the voids are filled with dry compounds.

What is very important when making slag concrete walls?

1. Cinder concrete must be laid in layers.

2. Tamping is carried out very carefully, bayoneting, etc. for protection against moisture.

3. Water the cement slag concrete with water for ten days and cover it (with roofing felt, burlap).

4. Insert tubes (about 0.5 cm in diameter) into the cinder concrete in several rows from the waterproofing layer (a few cm higher), under and above window openings, etc. to the attic floor beams.

Brick cladding protects cinder concrete well from external influences. Outside, cinder concrete without brick cladding is plastered after 1-1.5 months. Floor beams with slag concrete walls are dry tarred boards (bottom), on which the beams themselves are placed. This is done to better protect the beams from moisture.

Cornices in houses with cinder-concrete walls are best made of brick.

Table 1. Compositions of cement-based slag concrete mixtures (in volumetric parts)

Brand of cinder concrete	Cement brand
Brand of cinder concrete	M200	M300	M400
M15	1:12	—	—
M25	1:10	1:12,5	—
M50	1:5,7	1:7,7	1:9
M75	—	1:5,9	1:6,7

Table 2. Compositions of slag concrete mixtures with different ratios of coarse and fine aggregates

Design grade of slag concrete after 30 days of hardening	Cement: lime: sand: slag		Ratio of coarse and fine slags	Density, kg/m3
	in parts by weight	in volumetric parts	Ratio of coarse and fine slags	Density, kg/m3
M10	1:1:2:14	1:0,8:1,2:20	8:2	900
M25	1:0,5:2:7	1:0,4:1,4:10	7:3	1050
M35	1:0,4:2:4,7	1:0,25:1,4:6	6:4	1200
M50	1:0,25:3:2,5	1:0,2:1,4:4	5:5	1350

Note:

o cement - 1100 kg/m3;

o lime paste - 1400 kg/m3;

o sand - 1600 kg/m3;

o slag - 700...1000 kg/m3 (depending on the ratio of large and small fractions).

2. Cement grade 400.

3. For 1 m3 of the finished mixture you should take 200...250 liters of water. Usually the amount of water in the slag is not known, so water should be added based on the condition that the consistency of the slag concrete mixture should be similar to the consistency of lightly moistened soil.

4. Slag concrete grade 10 is used for thermal insulation, grades 25 and 35 for external walls, and grade 50 for internal load-bearing walls.

Table 3. Recommended slag concrete compositions for external walls (in volumetric parts)

Astringent	Cement M300	Slaked lime	Coarse sand	Slag
Cement+lime	1	5	7	25
Cement+lime	1	2	3	10
Cement+lime	1	4	—	20
Lime	—	1	—	5

Table 4. Compositions of slag concrete (in volumetric parts)

slag concrete

Note. If slaked lime is used, then its amount should be doubled and the amount of water reduced by 10%.

Features of mixtures for domestic use

There are many options for using slag and cement in repair and construction work.

But first, it would be advisable to consider the features of such concrete that are most appropriate for individual cases of its use.

Table of setting times for cement with different types of slag.

As a rule, the features of the mixture produced for exterior and interior decoration differ. If you are going to make a solution based on slag and cement, which you will use to finish the internal surfaces, then you should give preference to coarse-grained slag, of which you need to take about 6 parts. The remaining 4 parts are fine-grained granular slag. Any cement can be used for concrete. For finishing the external facade of a building, it is customary to use the following proportions: approximately 3 parts of fine-grained slag and 7 parts of coarse-grained slag. Cement must be of better quality so that it has sufficient resistance to external atmospheric influences.
If you need to make a high-quality pour and have enough time left, then you should give preference to non-granulated slag. This mixture will harden noticeably slower, but the result will be a much better coating. After all, cracks will not form on it for a long time, the appearance of which is observed after 1-2 years on a poured cement floor.
To finish the outer part of a protruding foundation (basement), experts recommend using cement with granulated slag. Moreover, the larger the surface to be finished, the more granules in the slag can be used. And vice versa.

Construction of a cinder block wall.

So, these were the main features of the use of slag and cement in ordinary domestic construction. By following these simple rules, you can achieve a high-quality finish and not regret anything in the future.

At the same time, you have an excellent opportunity to make, at least insignificant, but still save money through a clear choice of specific proportions.

What is concrete?

Rifey brick presses produced by the Stroytekhnika Plant, the city of Zlatoust, are equipment for the production of concrete, small-piece construction products. All building materials produced on Rifey brickmaking presses are obtained from concrete mixtures.

Concrete mixture is the most common material for construction, in its final form it is an artificial stone, very fluid before hardening (depending on the water content). Preparation of a concrete mixture consists of mixing cement, water, aggregate, and sometimes dye, until it is homogeneous; the recipe is carefully selected. After hardening, the concrete mixture turns into concrete.

Cement and water are the main ingredients of a concrete mixture. Being active participants in the mixture, when they are combined, a chemical reaction occurs, and a sticky compound is obtained, the so-called laitance. It is when this compound hardens that we get concrete.

The filler (in our case it can be expanded clay, sand, screenings, crushed stone of small fractions, sawdust and others) occupies up to 4/5 of the entire solution, interferes with the formation of shrinkage, and by changing the type and amount of filler, we ultimately influence the mass, density and strength of concrete.

Concrete is classified according to density: heavy (from 1780 kg/m3), light (550 – 1780 kg/m3) and especially light (up to 550 kg/m3). Density depends on the type of filler; it is dense (sand, crushed stone, screenings) and light (expanded clay, sawdust, slag).

Cement

Cement is a binder of inorganic origin. A mixture of clinker (a mixture of clay and lime after firing), gypsum. The most common is Portland cement. It gained popularity due to its activity - the ability to turn into stone after reacting with water, while not being inferior in hardness to natural ones. The grade of cement, its main characteristic, is set depending on the experimental data on the tensile strength. Cement hardens quickly, and after hardening it has excellent resistance to water, which allows it to be used in the construction of buildings without additional protection from rain and snow.

Source

Cooking method	Cement M300… M400	Powdered lime	Slag	Water- cement ratio
M25	Manually	1	1	17,5	2,6
M25	Mechanized	1	1	18	2,5
M40	Manually	1	1	12,5	1,85
M40	Mechanized	1	1	13	1,9
M100	Manually	1	0,25	5,5	0,9
M100	Mechanized	1	0,25	5,7	0,95