Vladivostok became the first Russian city to launch the production of concrete products from industrial and household waste. The enterprise will begin to produce 48 tons of products from plastic, food waste, textiles, broken bricks and concrete per day. The plant will produce up to 5 million tons of blocks per year, processed from ordinary household waste.
The first plant in Russia that distills waste into building materials - concrete products - began operating in Vladivostok. The first blocks for the construction of low-rise buildings have already been created and left the assembly line.
This is the first plant in Russia, the products of which partly consist of construction and household waste, and it was installed at the solid waste processing complex on Russky Island. Implementation new technology production building materials will significantly reduce the volume of waste disposal at the landfill, will reduce the cost of building materials necessary for the improvement of the city - paving stones, tiles, storm drains, blocks for low-rise construction.
The equipment for production was purchased by the city administration. Now a molding line has been installed for the production of building blocks (400x200x200 cm), but it is possible to connect any other mold for production: paving stones, storm gutters, tiles, tiles, curbs, etc.
This plant has no analogues in Russia. Here the production of concrete blocks, storm drains, and paving stones from waste is carried out using American technologies. The plant will produce 4–5 million tons of blocks per year. The price for the products of this plant will be 10–15% lower than the competitive price.
The idea of building a plant arose among officials when the problem of waste processing arose.
The equipment was purchased several years ago. On Russky Island, on the territory of the complex, there is a hangar in which all the equipment was placed (that is, the costs of building the premises were avoided), in addition, the logistics work out successfully: there is no need to transport the waste generated on the island to the mainland and construction waste can be brought from the mainland. Conventional materials are suitable for the manufacture of building materials. household waste(waste paper, plastic, food waste, textiles and others), belonging to the fourth hazard class according to the all-Russian classifier. In addition, you can use construction waste: broken bricks, concrete and others.
Up to 50% waste is used in the production of building materials. Chemical treatment of waste makes it possible to make the further product moisture-resistant, frost-resistant and well compatible with cement.
Experts believe that production from waste is safe for nature.
This is a proven and proven technology in civilized countries for the disinfection and recycling of waste, which, after processing, becomes one of the ingredients of building materials. The waste is fed onto a conveyor and then goes into a shredder, which crushes it into small particles. Next, it is mixed into a homogeneous mass and in the next container is mixed with chemical components that completely disinfect the garbage. After processing, this consistency is used as a filler in building materials, mixed with sand and cement and fed to a block-producing plant. Thanks to the mayor of Vladivostok, such a plant appeared in Vladivostok - this is the first and so far unique experience for our country. The technology allows you to reduce the cost of materials used annually for landscaping and direct funds to other needs.
EXPERT OPINION
Head of the Department for Organizing Environmental Measures at the Vladivostok City Hall, SmartNews
The uniqueness of the technology is that the facility has virtually no industrial wastewater, since the water supply system is closed; equipment is installed to purify emissions, but the amount of emissions is insignificant compared to other technologies. Waste from operation is typical, as for any other production associated with the operation of machines and mechanisms. The approximate sanitary protection zone is 300 meters (standardization for the production of building materials).
After graduating from university in 2003, Volgograd resident Roman Sebekin got the idea of building houses from recycled plastic. He traveled half the country in search of suitable technologies, purchased used equipment and registered
company "Southern Federal District-Pererabotka". During the crisis, his blocks, which cost half as much as regular ones, began to be popular among builders of private houses. Now the company's monthly turnover is 350,000 rubles.
Roman SEBEKIN
Founder of the company "Southern Federal District-Pererabotka"
How it all began
Even as a child, I saw two ways: either work for the state or for myself. At first I chose the first path. After school, I entered the economics department of the Volgograd branch of the Academy of Civil Service, I wanted to work in the tax crimes department. It seemed to me that this was a very interesting and promising direction. But after several internships with the tax police, disappointment set in. I didn't like it there at all. As a result, I abandoned my dream and decided to get a second higher education - I entered the law school. But by the end of my studies I realized that I would not be a lawyer. I was captivated by the idea of building a house from recycled plastic.
I read a lot about such technologies, I saw programs about foreign companies that specialize in waste processing and subsequent construction. The year was 2003. There were no ready-made technologies at that time, and I had frankly little money. But Volgograd is an industrial city. Here you can even build a tank, you just need to know how to assemble it. I began to think through technology and equipment, began to travel around Russia in search of materials and developments, and studied production. Often I had to act by trial and error. Start-up capital was very small. I earned some money myself, and my mother helped me in some ways. I spent about $1,000 on used equipment, which I then completely rebuilt. As a result, I invested approximately 100,000 rubles in the business. It took a lot of time and effort to launch the company, but it was still possible. In 2004 I registered a company.
How does recycling work?
The plastic is crushed, mixed with sand and water and pressed. This is a very simplified description of the process. All the equipment I use is domestic, but there is little left of the previous models; I completely rebuilt them. Processing is done quite quickly. After two to three hours, the finished product is obtained - a tile or building block. Not all types of plastic are suitable for recycling, but in most cases plastic waste can be used to create building materials. From 10 cubic meters of plastic you can make 300 building blocks. Our processing capacity, 10,000 m 3 per month, is approximately three one-story houses of 100 m 2 each. We presented the technology to various departments, underwent examination by Rospotrebnadzor and received a quality certificate. There is a GOST for polystyrene products, which any material must comply with. The flammability of the material is checked to see if the material is harmful to the environment. This is exactly the kind of examination our blocks passed.
I found the production premises through friends. I am renting a hangar in the city of Dubovka, which is located 50 km from Volgograd. Its area is 3,000 sq.m. Sorting takes place in the city, which is cheaper. The company collects plastic from everyone possible ways. Sometimes residents themselves bring plastic waste, and some are collected using containers placed around the city. I have tried to negotiate with local companies to provide their plastic waste, but they either refuse or ask for money for their waste.
In terms of its aesthetic characteristics, a house made of plastic blocks is in no way inferior to an ordinary house. And in terms of energy saving it is even superior. Polystyrene blocks retain heat. It turns out that the house is insulated. In addition, they are cheaper: they cost 30 rubles apiece, while standard blocks cost 60 rubles.
Money
The company became self-sufficient in August last year. Since then, we have taken on additional social responsibilities - we placed waste collection containers throughout the city - and now the company is breaking even. Now “Southern Federal District-processing” lives with a monthly turnover of 350,000 rubles.
Clients
Our services are used by private individuals. It would be profitable to enter the corporate segment; orders from companies are larger. But with private clients, we calmly survived the 2008 crisis. Everyone was looking for an opportunity to save money, and our blocks and tiles are an excellent alternative to conventional building materials. We have been on the market for several years now, so we have regular customers.
Gradually the effect of word of mouth began to kick in. Someone builds a house using our materials and is satisfied, and then recommends them to their neighbors. This happens very often. Many clients come to me based on recommendations. However, this was not always the case. It happened that we encountered mistrust. People were skeptical about the new recycled material, although we have all the quality certificates. I remember one incident when a person first bought polymer tiles from us, and after some time returned them, saying that he still preferred classic ceramic ones. There are practically no such cases now. When purchasing, we immediately explain to our customers how and from what our building materials are made. The advantage of plastic tiles and building blocks is their price and durability. In 2011, a private kindergarten was built from our blocks.
Our business is hampered by two factors: low environmental awareness of the population and lack of production space for waste disposal
Principles
When I first started in this business, I didn't think so much about the environmental component. At first, it was necessary to solve clear problems - to build a house and create high-quality material, for which one would not have to blush later. But now my main principles lie in the field of ecology. We are fighting environmental illiteracy. Recently, thanks to a loan provided by the Our Future Foundation, we were able to place containers for separate waste collection in different areas of the city. Unfortunately, not all of them remained in their places; some were taken away. Our company has placed containers in kindergartens and parks. It seems to me that people from childhood should be taught to separate waste collection and respect for nature.
Problems
Our business is greatly hampered by the low environmental awareness of the population. There was a case when a resident of Volgograd cut off one of our containers and threw it in the trash. When I asked why she did this, the woman replied that she was annoyed by the appearance of the container, which was constantly filled with plastic: “I don’t give a damn about your ecology! The main thing is that it is beautiful under my windows.”
The state also helps little and sometimes gets in the way. There are two main environmental departments in our city. The first is the Department of Environment and Natural Resources, and the second is the Environmental Prosecutor's Office. The first department is very interested in the development of our enterprise. They help us in every possible way, advise us, organize PR campaigns. The environmental prosecutor's office behaves completely differently. If they find even the slightest violation, they immediately impose fines and threaten to close the production. As for the regional authorities, in principle they are not interested in what we are doing, although they are in favor of the environment. No matter how much we tried to cooperate with them, nothing worked.
Now our main limiting factor is that we do not have enough production space where we could process everything. If they were, we could recycle 90% of the plastic in the city.
Plans
Our main task is to establish the production of polymer sleepers. The equipment is almost ready. All that remains is to manufacture the product itself and send it for testing to the Russian Railways Research Institute. Many people already understand that plastic is the future. Concrete and other materials are a thing of the past. We place a big bet on eco sleepers.
Another project is related to the organization of an environmental fund. I recently submitted documents to register it. He will have to help environmental enterprises not only here in Volgograd, but throughout Russia. The main assistance will be in the provision of grants - we have already found sponsors who will provide the material component. In addition, the foundation will help collect and disseminate recycling technologies.
Text: Diana Kulchitskaya
*information is posted for informational purposes; to thank us, share the link to the page with your friends. You can send material interesting to our readers. We will be happy to answer all your questions and suggestions, as well as hear criticism and suggestions at [email protected]Today, rational use natural resources plays a special role. Solving this urgent problem involves the development and implementation of effective waste-free technologies. Some of them are actively used, others are just starting to be used. The article discusses the main building materials that are produced from waste, gives a brief description of them, scope of application, and estimated cost. As a supplement to the material, find out more about prefabricated buildings by Joris Ide, because construction can really be easy, details on the website http://joriside.ru/.
Wood waste materials
The volume of construction work is constantly increasing, much faster than the amount of timber harvested. Therefore, the market experiences a shortage of this material. The solution is to use waste from wood harvesting and processing. After all, such residues are obtained at every stage of working with wood.
Lump waste, sawdust and shavings are widely used for the production of building materials:
- sawdust is one of the most common waste from wood processing, the average cost is 150 rubles/m3. The scope of their application is extensive: insulation, chipboard production. If you combine sawdust with cement, you get sawdust concrete, suitable for the construction of houses, outbuildings, and non-residential buildings. One more is enough interesting solution use of such waste - production of wood blocks. They are produced using sawdust, copper sulfate, cement;
- The shavings are used to produce a durable building material called wood concrete. It is resistant to low temperatures, has good thermal insulation properties, does not rot. The average price for shavings is 150 rub.m.
- lump waste is used for the production of glued construction products. In addition, such material can be recycled. The result is industrial chips, fibrous mass, crushed wood, shavings and much more. The cost of the material starts from 100 rubles/cub.m.
For the production of building materials, waste from deciduous and coniferous trees is used. It is preferable to use coniferous species, since they contain fewer substances that subsequently affect the cement hardening processes. In addition, higher-quality fibrous mass can be obtained from coniferous tree waste.
The use of wood processing and sawmill waste can reduce the volume of forests cut down, improve the situation with the supply of forest resources, and affect the cost of products.
Materials from industrial waste
Effective development of the construction sector is impossible without the creation of new building materials, the production of which involves industrial waste. Most of the remains in their own technical parameters and chemical composition are similar or have advantages over natural raw materials. In addition to these advantages, the use of industrial waste has important economic and environmental significance and affects the reduction of material consumption.
Among the many types of waste from industrial enterprises, the following can be distinguished:
- The leader in terms of use is blast furnace slag. Such a resource is formed as a result of the smelting of steel and cast iron. The slag is used to produce Portland cement, allowing its output to be significantly increased. It not only improves the construction and technical properties of the material, but also helps reduce consumption energy resources. A relatively new building material based on blast furnace slag is slag crystallites. This material has excellent strength indicators, and is produced by the method of catalytic crystallization of slag glass. The average price for blast furnace slag is 290 rubles/m3;
- solid fuel combustion waste - ash and slag mixture, dry ash. These are also important raw materials for the production of a variety of building materials. They are used in the production of cellular and cementitious concrete, road construction, production of wall materials, and concrete production. The average cost of ash and slag per ton is 1,400 rubles;
- The raw materials for construction materials are chemical waste. For example, phosphogypsum and phosphorus slag. Their scope of application is the production of wall ceramics, brick production. Industry needs for gypsum raw materials can be fully satisfied through gypsum-containing waste, such as phosphogypsum;
- waste from coal mining and coal preparation is used as a fuel additive in the production of ceramic products;
- non-ferrous metallurgy slags and steelmaking slags are used for the production of mineral wool, building crushed stone, and various binding materials;
- waste from mining enterprises has also found its application for the production of glass, ceramics, and autoclave materials.
Waste use industrial enterprises for obtaining a variety of building materials has a significant economic and environmental effect.
Conclusion
Creation waste-free production- not such a distant future. Enterprises need to develop waste-free technologies, change technological processes, and implement closed-cycle systems that can ensure the repeated use of raw materials. With proper organization of all processes, it is possible to ensure that waste from industrial or wood processing enterprises becomes raw materials for other companies.
This way, several problems can be solved. Firstly, significantly reduce the needs of organizations for natural raw materials. Secondly, reduce production costs and their payback period. Thirdly, proper use of waste will reduce harmful emissions into the environment, to solve environmental problems. All this can only be made a reality together: at the level of government and representatives of commercial structures.
All civilized countries annually increase the percentage of recycling of recyclable materials, improve technologies and legislative framework. Organizing the sorting, reception and processing of recyclable materials is not an easy task, requiring considerable capital investments and changes in legislation on a state scale. But as a result, we get savings in natural resources, a reduction in the cost of finished products, and a reduction in the level of environmental pollution.
This issue is extremely relevant for the construction industry. After the construction of any facility is completed, tons of waste remain. As a rule, they are simply taken to unauthorized landfills, in best case scenario, to landfills. Disposing of construction waste for disposal or recycling is still not popular.
Construction companies are not interested in removing waste for recycling. Architects are in no hurry to use building materials made from recycled materials, since they cannot be sure of the environmental friendliness of these products. Certification and sanitary system epidemiological control recyclable materials leave much to be desired, and this is often taken advantage of by unscrupulous recycling companies.
Although the construction industry is suspicious of the use of recycled materials, there is waste, the use of which no one doubts. Recycled crushed stone and asphalt chips are successfully used for road construction, broken bricks are used to construct temporary access roads, and slag is used in the production of concrete. A boon for an eco-friendly home is siding made from waste wood and fiber insulation material.
Recycling of scrap metal and waste paper is a profitable, well-functioning industry. The situation is more complicated with the processing of plastic, rubber and glass. But recent developments by scientists make it possible to effectively solve this problem.
Rubber products are processed into rubber granulate, crumb rubber and dust. The resulting raw materials are used to make floor coverings, insulating materials, drainage mats, and soundproofing materials.
Silicate conglomerate is produced from cullet. Glass concrete is a durable, acid-resistant and bio-resistant material. An activator is needed to transform the cullet into a homogeneous mass. An alkali metal is used as an activator, which reacts with cullet. As a result, silicic acid is formed, which turns into a gel bonding filler.
Roof tiles, curb stones, paving slabs, hatches and garbage bins It is advantageous to make it from polymer sand mass. The advantage of this processing method is that there is no need to sort and wash the raw materials. It is enough to adhere to the proportion: 40 parts of soft plastic, 60 parts of hard. The plastic is crushed, heated and mixed in an extrusion machine, the finished mass is taken out with mittens and thrown into water to cool. The agglomerate prepared in this way is re-crushed and used to make polymer sand mass.
The problem of waste recycling is relevant not only during the construction of new buildings and structures, but also during the demolition of existing ones. Disposal of waste from destroyed buildings has two directions: reuse of finished products and structures and recycling of raw materials. The biggest problem when demolishing buildings is reinforced concrete structures, but with the help of a crushing and screening complex, it is easy to obtain secondary crushed stone and reinforcement. This leaves a very small amount of waste that needs to be removed.
The use of recycled materials is the need of tomorrow.
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Ministry of Science and Education of Ukraine
Kyiv National University of Construction and Architecture
Department of Construction Materials Science
Abstract on the topic: “The use of secondary products in the manufacture of building materials”
PLAN:
1. The problem of industrial waste and the main directions for solving it
c) Fused and artificial stone materials based on slagand angry
c) Materials from forest chemical waste and wood processing
4. References
1. The problem of industrial waste and the main directions for solving it.
a) Industrial development and waste accumulation
A characteristic feature of the scientific and technical process is an increase in the volume of social production. The rapid development of productive forces causes the rapid involvement of more and more natural resources into economic circulation. The degree of their rational use, however, remains, in general, very low. Every year, humanity uses approximately 10 billion tons of mineral and almost the same amount of organic raw materials. The development of most of the world's most important minerals is proceeding faster than their proven reserves are increasing. About 70% of industrial costs come from raw materials, supplies, fuel and energy. At the same time, 10...99% of the feedstock turns into waste, discharged into the atmosphere and water bodies, polluting the earth. In the coal industry, for example, approximately 1.3 billion tons of overburden and mine rocks and about 80 million tons of coal processing waste are generated annually. The annual output of ferrous metallurgy slag is about 80 million tons, non-ferrous 2.5, thermal power plant ash and slag is 60...70 million tons, wood waste is about 40 million m³.
Industrial waste actively influences environmental factors, i.e. have a significant impact on living organisms. First of all, this relates to the composition of atmospheric air. Gaseous and solid wastes enter the atmosphere as a result of fuel combustion and various technological processes. Industrial waste actively affects not only the atmosphere, but also the hydrosphere, i.e. aquatic environment. Under the influence of industrial waste concentrated in dumps, slag dumps, tailings dumps, etc., surface runoff in the area where industrial enterprises are located is polluted. The dumping of industrial waste ultimately leads to pollution of the waters of the World Ocean, which leads to a sharp decrease in its biological productivity and negatively affects the planet's climate. The generation of waste as a result of the activities of industrial enterprises negatively affects the quality of the soil. Excessive amounts of compounds that have a detrimental effect on living organisms, including carcinogenic substances, accumulate in the soil. In contaminated “sick” soil, degradation processes occur and life activity is disrupted soil organisms.
A rational solution to the problem of industrial waste depends on a number of factors: the material composition of the waste, its aggregate state, quantity, technological features, etc. The most effective solution to the problem of industrial waste is the introduction of waste-free technology. The creation of waste-free production is carried out through a fundamental change in technological processes, the development of closed-cycle systems that ensure the repeated use of raw materials. With the integrated use of raw materials, industrial waste from some industries are the starting raw materials of others. The importance of integrated use of raw materials can be viewed from several aspects. Firstly, waste disposal makes it possible to solve environmental protection problems, free up valuable land occupied by dumps and sludge storage facilities, and eliminate harmful emissions into the environment. Secondly, waste largely covers the raw material needs of a number of processing industries. Thirdly, with the integrated use of raw materials, specific capital expenditures per unit of production and their payback period decreases.
Of the industries that consume industrial waste, the most capacious is the construction materials industry. It has been established that the use of industrial waste can cover up to 40% of construction needs for raw materials. The use of industrial waste makes it possible to reduce the cost of producing building materials by 10...30% compared to their production from natural raw materials, savings capital investments reaches 35..50%.
b) Classification of industrial waste
To date, there is no comprehensive classification of industrial waste. This is due to the extreme diversity of their chemical composition, properties, technological features, and conditions of formation.
All industrial waste can be divided into two large groups: mineral (inorganic) and organic. Highest value mineral waste is used for the production of building materials. They account for the predominant share of all waste produced by the mining and processing industries. These wastes have been studied to a greater extent than organic ones.
Bazhenov P.I. it is proposed to classify industrial waste at the time of its separation from the main technological process into three classes: A; B; IN.
Class A products (quarry residues and residues after enrichment for minerals) have the chemical and mineralogical composition and properties of the corresponding rocks. The scope of their application is determined state of aggregation, fractional and chemical composition, physical and mechanical properties.
Class B products are artificial substances. They are obtained as by-products as a result of physical and chemical processes occurring during normal or more frequent high temperatures. Range possible application of these industrial wastes are wider than class A products.
Class B products are formed as a result of physical and chemical processes occurring in dumps. Such processes can be spontaneous combustion, decomposition of slags and the formation of powder. Typical representatives of this class of waste are burnt rocks.
2. Experience in the use of waste from metallurgy, fuel industry and energy
a) Cementing materials based on slag and ashes
The bulk of waste from the production of metals and the combustion of solid fuels is formed in the form of slags and ash. In addition to slags and ashes, during metal production large quantities of waste are generated in the form of aqueous suspensions of dispersed particles - sludge.
Valuable and very common mineral raw materials for the production of building materials are burnt rocks and coal processing waste, as well as overburden rocks and ore processing waste.
The production of binding materials is one of the most effective areas of application of slag. Slag binders can be divided into the following main groups: slag Portland cement, sulfate-slag, lime-slag, slag-alkaline binders.
Slags and ashes can be considered as largely prepared raw materials. In their composition, calcium oxide (CaO) is bound in various chemical compounds, including in the form of dicalcium silicate - one of the minerals of cement clinker. A high level of preparation of the raw material mixture when using slags and ashes ensures increased furnace productivity and fuel economy. Replacing clay with blast furnace slag makes it possible to reduce the content of the lime component by 20%, reduce the specific consumption of raw materials and fuel during dry clinker production by 10...15%, and also increase the productivity of furnaces by 15%.
By using low-iron slags - blast furnace and ferrochrome - and creating reducing smelting conditions, white cements are produced in electric furnaces. Based on ferrochrome slags, by oxidizing chromium metal in the melt, clinkers can be obtained, which can be used to produce cements with an even and durable color.
Sulphate-slag cements – These are hydraulic binders obtained by joint fine grinding of granulated blast furnace slag and a sulfate hardening agent - gypsum or anhydride with a small addition of an alkaline activator: lime, Portland cement or burnt dolomite. The most widely used of the sulfate-slag group is gypsum slag cement, containing 75...85% slag, 10...15% gypsum dihydrate or anhydride, up to 2% calcium oxide or 5% Portland cement clinker. High activation is ensured by using anhydrite, calcined at a temperature of about 700º C, and high-alumina basic slags. The activity of sulfate-slag cement significantly depends on the fineness of grinding. A high specific surface area (4000...5000 cm²/g) of the binder is achieved using wet grinding. With a sufficiently high fineness of grinding in a rational composition, the strength of sulfate-slag cement is not inferior to the strength of Portland cement. Like other slag binders, sulfate-slag cement has a low heat of hydration - up to 7 days, which makes it possible to use it in the construction of massive hydraulic structures. This is also facilitated by its high resistance to soft sulfate waters. The chemical resistance of sulfate slag cement is higher than that of Portland slag cement, which makes its use especially appropriate in various aggressive conditions.
Lime-slag and lime-ash cements – These are hydraulic binders obtained by joint grinding of granulated blast furnace slag or fly ash from thermal power plants and lime. They are used for the preparation of mortars of grades no more than M 200. To regulate the setting time and improve other properties of these binders, up to 5% of gypsum stone is added during their manufacture. The lime content is 10%...30%.
Lime-slag and ash cements are inferior in strength to sulfate-slag cements. Their brands are: 50, 100, 150 and 200. The beginning of setting should occur no earlier than 25 minutes, and the end should occur no later than 24 hours after the start of mixing. When the temperature decreases, especially after 10º C, the increase in strength slows down sharply and, conversely, an increase in temperature with sufficient environmental humidity promotes intensive hardening. Hardening in air is possible only after sufficiently long hardening (15...30 days) in humid conditions. These cements are characterized by low frost resistance, high resistance to aggressive waters and low exotherm.
Slag-alkali binders consist of finely ground granulated slag (specific surface area≥3000 cm²/g) and an alkaline component - compounds of alkali metals sodium or potassium.
To obtain slag-alkaline binder, granulated slags with different mineralogical compositions are acceptable. The decisive condition for their activity is the content of a glassy phase capable of interacting with alkalis.
The properties of the slag-alkaline binder depend on the type, mineralogical composition of the slag, the fineness of its grinding, the type and concentration of its solution of the alkaline component. With a specific surface area of slag of 3000...3500 cm²/g, the amount of water to form a dough of normal density is 20...30% of the binder mass. The strength of the slag-alkaline binder when testing samples from dough of normal density is 30...150 MPa. They are characterized by an intensive increase in strength both during the first month and during subsequent hardening periods. So, if the strength of Portland cement after 3 months. hardening under optimal conditions exceeds the brand name by about 1.2 times, then the slag-alkaline binder by 1.5 times. During heat and moisture treatment, the hardening process is also accelerated more intensively than during hardening of Portland cement. Under normal steaming conditions adopted in precast concrete technology, for 28 days. 90...120% of brand strength is achieved.
The alkaline components included in the binder act as an anti-frost additive, therefore slag-alkaline binders harden quite intensively when negative temperatures.
b) Fillers from slag ash waste
Slag and ash waste represent a rich raw material base for the production of both heavy and light porous concrete aggregates. The main types of aggregates based on metallurgical slag are slag crushed stone and slag pumice.
Porous aggregates are made from fuel slags and ashes, including agloporite, ash gravel, and alumina-sol expanded clay.
To effective types of heavy concrete aggregates that are not inferior in physical mechanical properties The product of crushing dense natural stone materials is cast slag crushed stone. In the production of this material, cast fire-liquid slag from slag ladles is poured in layers 200...500 mm thick onto special casting platforms or into tarpezoidal pit-trenches. When kept in open air for 2...3 hours, the temperature of the melt in the layer decreases to 800° C, and the slag crystallizes. It is then cooled with water, which leads to the development of numerous cracks in the slag layer. Slag masses at foundry sites or in trenches are mined by excavators and then crushed.
Cast slag crushed stone is characterized by high frost and heat resistance, as well as abrasion resistance. Its cost is 3...4 times lower than crushed stone made from natural stone.
Slag pumice (slows down)– one of the most effective types of artificial porous aggregates. It is obtained by porous slag melts as a result of their rapid cooling with water, air or steam, as well as exposure to mineral gas-forming agents. Of the technological methods for producing slag pumice, the most commonly used are pool, jet and hydroscreen methods.
Fuel slags and ash are the best raw materials for the production of artificial porous aggregate - agloporite. This is due, firstly, to the ability of ash and slag raw materials, as well as clayey rocks and other aluminosilicate materials, to sinter on the gratings of sintering machines, and secondly, the content of residual fuel in it, sufficient for the sintering process. Using conventional technology, agloporite is obtained in the form of crushed sand. From the ashes of thermal power plants it is possible to obtain agloporite gravel, having high technical and economic indicators.
The main feature of agloporite gravel technology is that as a result of agglomeration of raw materials, not a sintered cake is formed, but burnt granules. The essence of the technology for the production of agloporite gravel is to obtain raw ash granules with a particle size of 10...20 mm, laying them on the grates of a belt sintering machine in a layer 200...300 mm thick and heat treatment.
The production of agloprite compared to conventional agloporite production is characterized by a 20...30% reduction in process fuel consumption, lower air rarefaction in vacuum chambers and an increase in specific productivity by 1.5...3 times. Agloporite gravel has a dense surface shell and therefore, with an almost equal volumetric mass with crushed stone, differs from it in higher strength and lower water absorption. It is estimated that replacing 1 million m³ of imported natural crushed stone with Agdoport gravel from the ash of thermal power plants, only by reducing transportation costs when transporting over a distance of 500...1000 km, saves 2 million rubles. The use of agloporite based on the ashes and slags of thermal power plants makes it possible to obtain lightweight concrete grades 50...4000 with a bulk weight from 900 to 1800 kg/m³ with a cement consumption of 200 to 400 kg/m³.
Ash gravel is obtained by granulating a prepared ash and slag mixture or fly ash from thermal power plants, followed by sintering and swelling in a rotary kiln at a temperature of 1150...1250 ° C. Light concrete with approximately the same characteristics as when using aggloporite gravel is obtained using ash gravel. In the production of ash gravel, only expanding ash from thermal power plants with a fuel residue content of no more than 10% is effective.
Clay expanded clay – a product of swelling and sintering in a rotating kiln of granules formed from a mixture of clays and ash and slag waste from thermal power plants. Ash can make up from 30 to 80% of the total mass of raw materials. The introduction of a clay component improves the molding properties of the charge and promotes the burning of coal residues in the ash, which makes it possible to use ash with a high content of unburned fuel.
The volumetric mass of alumina-sol expanded clay is 400..6000 kg/m³, and the compressive strength in a steel cylinder is 3.4...5 MPa. The main advantages of the production of alumina-ash expanded clay compared to agloporite and ash gravel are the possibility of using thermal power plant ash from dumps in a wet state without the use of drying and grinding units and a simpler method of forming granules.
c) Fused and artificial stone materials based on slag and ashes
The main areas of processing metallurgical and fuel slags, as well as ashes, along with the production of binders, fillers and concrete based on them, include the production of slag wool, cast materials and slag stones, ash ceramics and sand-lime bricks.
Slag wool- a type of mineral wool that occupies a leading place among thermal insulation materials, both in terms of production volume and in terms of construction and technical properties. Blast furnace slag has found the greatest use in the production of mineral wool. Using slag instead of natural raw materials here results in savings of up to 150 UAH. per 1 ton. To produce mineral wool, along with blast furnace, cupola, open-hearth slag and non-ferrous metallurgy slag are also used.
The required ratio of acidic and basic oxides in the charge is ensured by the use of acidic slags. In addition, acidic slags are more resistant to decay, which is unacceptable in mineral wool. An increase in silica content expands the temperature range of viscosity, i.e. temperature difference within which fiber formation is possible. The acidity modulus of slag is adjusted by introducing acidic or basic additives into the mixture.
A variety of products are cast from the melt of metallurgical and fuel slag: stones for paving roads and floors of industrial buildings, tubing, curb stones, anti-corrosion tiles, pipes. The production of slag casting began simultaneously with the introduction of the blast furnace process into metallurgy. Cast products from molten slag are more economically advantageous compared to stone casting, approaching it in mechanical properties. The volumetric mass of dense cast slag products reaches 3000 kg/m³, the compressive strength is 500 MPa.
Slag crystals– a type of glass-crystalline materials obtained by directional crystallization of glasses. Unlike other glass-ceramics, the raw materials for them are slags from ferrous and non-ferrous metallurgy, as well as coal combustion ash. Slag ceramics were developed for the first time in the USSR. They are widely used in construction as structural and finishing materials with high strength. The production of slag glass consists of melting slag glasses, forming products from them and their subsequent crystallization. The charge for glass production consists of slag, sand, alkali-containing and other additives. The most efficient use of fiery liquid metallurgical slags, which saves up to 30...40% of all heat spent on cooking.
Slag ceramics are increasingly used in construction. Sheet slag slag slabs are used to cover plinths and facades of buildings, to finish internal walls and partitions, and to make fencing for balconies and roofs. Slagwood is an effective material for steps, window sills and other structural elements of buildings. High wear resistance and chemical resistance make it possible to successfully use slag ceramics to protect building structures and equipment in the chemical, mining and other industries.
Ash and slag waste from thermal power plants can serve as depleting fuel-containing additives in the production of ceramic products based on clay rocks, as well as the main raw material for the production of ash ceramics. Fuel ashes and slags are most widely used as additives in the production of wall ceramic products. For the manufacture of solid and hollow bricks and ceramic stones, it is primarily recommended to use low-melting ash with a softening point of up to 1200 ° C. Ash and slag containing up to 10% of fuel are used as waste, and 10% or more are used as fuel-containing additives. In the latter case, it is possible to significantly reduce or eliminate the introduction of process fuel into the charge.
A number of technological methods have been developed for producing ash ceramics, where ash and slag waste from thermal power plants is no longer an additional material, but the main raw material component. Thus, with conventional equipment in brick factories, ash bricks can be made from a mass including ash, slag and sodium liquid glass in an amount of 3% by volume. The latter acts as a plasticizer, ensuring the production of products with minimal moisture, which eliminates the need for drying the raw material.
Ash ceramics are produced in the form of pressed products from a mass containing 60...80% fly ash, 10...20% clay and other additives. The products are sent for drying and firing. Ash ceramics can serve not only as a wall material with stable strength and high frost resistance. It is characterized by high acid resistance and low abrasion, which makes it possible to produce paving and road slabs and products with high durability from it.
In the production of sand-lime bricks, thermal power plant ash is used as a component of the binder or filler. In the first case, its consumption reaches 500 kg, in the second - 1.5...3.5 tons per 1 thousand pieces. bricks When introducing coal ash, lime consumption is reduced by 10...50%, and shale ash with a CaO+MgO content of up to 40...50% can completely replace lime in the silicate mass. Ash in lime-ash binder is not only an active siliceous additive, but also contributes to the plasticization of the mixture and increases the strength of the raw material by 1.3...1.5 times, which is especially important for ensuring the normal operation of automatic stackers.
d) Ashes and slags in road construction and insulating materials
A large-scale consumer of fuel ash and slag is road construction, where ash and ash and slag mixtures are used for the construction of underlying and lower layers of foundations, partial replacement of binders when stabilizing soils with cement and lime, as mineral powder in asphalt concretes and mortars, as additives in road cement concrete.
Ashes obtained from the combustion of coal and oil shale are used as fillers for roofing and waterproofing mastics. Ash and slag mixtures are used in road construction either unstrengthened or reinforced. Unreinforced ash and slag mixtures are used mainly as a material for the construction of underlying and lower layers of the foundations of roads of regional and local importance. With a content of no more than 16% pulverized ash, they are used to improve soil coatings subjected to surface treatment with bitumen or tar emulsion. Structural layers of roads can be made from ash and slag mixtures with an ash content of no more than 25...30%. In gravel-crushed stone bases, it is advisable to use an ash and slag mixture with a pulverized ash content of up to 50% as a compacting additive. The content of unburned coal in fuel waste from thermal power plants used for road construction should not exceed 10%.
Just like natural stone materials of relatively high strength, ash and slag waste from thermal power plants are used for the production of bitumen-mineral mixtures used to create structural layers of roads of categories 3-5. Black crushed stone is obtained from fuel slag treated with bitumen or tar (up to 2% by weight). By mixing ash heated to 170...200°C with a 0.3...2% solution of bitumen in green oil, a hydrophobic powder with a volumetric mass of 450...6000 kg/m³ is obtained. Hydrophobic powder can simultaneously perform the functions of a hydro- and heat-insulating material. The use of ashes as a filler in mastics is widespread.
e) Materials based on metallurgical sludge
Nepheline, bauxite, sulfate, white and multi-calcium sludges are of industrial importance for the production of building materials. The volume of nepheline sludge alone, suitable for use, is annually over 7 million tons.
The main application of sludge waste from the metallurgical industry is the production of clinker-free binders and materials based on them, the production of Portland cement and mixed cements. Nepheline (belite) sludge, obtained by extracting alumina from nepheline rocks, is especially widely used in industry.
Under the leadership of P.I. Bazhenov developed a technology for the production of nepheline cement and materials based on it. Nepheline cement is a product of co-grinding or thorough mixing of pre-crushed nepheline sludge (80...85%), lime or other activator, such as Portland cement (15...20%) and gypsum (4...7%). The beginning of setting of nepheline cement should occur no earlier than after 45 minutes, the end - no later than after 6 hours. after its confinement, His marks are 100, 150, 200 and 250.
Nepheline cement is effective for masonry and plaster mortars, as well as for normal and especially autoclaved concrete. In terms of plasticity and setting time, solutions based on nepheline cement are close to lime-gypsum solutions. In normal-hardening concrete, nepheline cement provides grades 100...200, in autoclaved concrete - grades 300...500 at a consumption of 250...300 kg/m³. The peculiarities of concrete based on nepheline cement are low exometry, which is important to take into account when constructing massive hydraulic structures, high adhesion to steel reinforcement after autoclave treatment, and increased durability in mineralized waters.
Close in composition to nepheline cement are binders based on bauxite, sulfate and other metallurgical sludges. If a significant part of these minerals is hydrated, in order for the astringent properties of the sludge to manifest, it is necessary to dry them in the range of 300...700° C. To activate these binders, it is advisable to introduce lime and gypsum additives.
Slurry binders belong to the category of local materials. It is most rational to use them for the manufacture of autoclave-hardening products. However, they can and will be used in mortars, finishing works, and the production of materials with organic fillers, such as fiberboard. The chemical composition of a number of metallurgical slurries allows them to be used as the main raw material component of Portland cement clinker, as well as an active additive in the production of Portland cement and mixed cements.
f) Use of burnt rocks, coal preparation waste, ore mining and beneficiation
The bulk of burnt rocks are a product of burning waste rocks accompanying coal deposits. Varieties of burnt rocks are gliezh - gilin and clay-sand rocks, burned in the bowels of the earth during underground fires in coal seams, and waste, burnt-out mine rocks.
The possibilities for using burnt rocks and coal processing waste in the production of building materials are very diverse. Burnt rocks, like other calcined clay materials, are active in relation to lime and are used as hydraulic additives in lime-pozzolanic type binders, Portland cement, pozzolanic Portland cement and autoclave materials. High adsorption activity and adhesion to organic binders allow their use in asphalt and polymer compositions. Naturally, burnt rocks burned in the bowels of the earth or in waste heaps of coal mines - mudstones, siltstones and sandstones - are of a ceramic nature and can be used in the production of heat-resistant concrete and porous aggregates. Some burnt rocks are light non-metallic materials, which leads to their use as fillers for lightweight mortars and concretes.
Coal preparation waste is a valuable type of mineralogy raw material, mainly used in the production of ceramic wall materials and porous aggregates. The chemical composition of coal enrichment waste is close to traditional clayey raw materials. The role of a harmful impurity in them is sulfur contained in sulfate and sulfide compounds. Their calorific value varies widely - from 3360 to 12600 kJ/kg and more.
In the production of wall ceramic products, coal enrichment waste is used as a lean or burnable fuel additive. Before being introduced into the ceramic charge, the lump waste is crushed. Pre-crushing is not required for sludge with particle sizes less than 1mm. The sludge is pre-dried to a moisture content of 5...6%. The addition of waste when producing bricks using the plastic method should be 10...30%. The introduction of the optimal amount of fuel-containing additive as a result of more uniform firing significantly improves the strength characteristics of products (up to 30...40%), saves fuel (up to 30%), eliminates the need to introduce coal into the charge, and increases the productivity of furnaces.
It is possible to use coal enrichment sludge with a relatively high calorific value (18900...21000 kJ/kg) as a process fuel. It does not require additional crushing, is well distributed throughout the charge when poured through the fuel holes, which promotes uniform firing of products, and most importantly, it is much cheaper than coal.
From some types of coal enrichment waste it is possible to produce not only agloporite, but also expanded clay. A valuable source of non-metallic materials are associated rocks from mining industries. The main direction of recycling of this group of waste is the production, first of all, of concrete and mortar aggregates, road building materials, and rubble stone.
Construction crushed stone is obtained from associated rocks during the extraction of iron and other ores. High-quality raw materials for the production of crushed stone are barren ferruginous quartzites: hornfels, quartzite and crystalline schists. Crushed stone from associated rocks during iron ore mining is obtained at crushing and screening plants, as well as through dry magnetic separation.
3. Experience in the use of waste from chemical-technological production and wood processing
a) Application of slags from electrothermal phosphorus production
Agricultural waste of plant origin is also an important source of construction raw materials. The annual output, for example, of cotton stem waste is about 5 million tons per year, and flax kernels is more than 1 million tons.
Wood waste is generated at all stages of its harvesting and processing. These include branches, twigs, tops, branches, canopies, sawdust, stumps, roots, bark and brushwood, which together make up about 21% of the total mass of wood. When processing wood into lumber, the product yield reaches 65%, the rest forms waste in the form of slabs (14%), sawdust (12%), cuttings and small items (9%). When manufacturing construction parts, furniture and other products from lumber, waste arises in the form of shavings, sawdust and individual pieces of wood - cuttings, which make up up to 40% of the mass of processed lumber.
Sawdust, shavings and lump waste are of greatest importance for the production of building materials and products. The latter are used both directly for the production of glued building products and for processing into industrial chips, and then shavings, crushed wood, and fibrous mass. A technology has been developed for obtaining building materials from bark and dun, a waste product from the production of tanning extracts.
Phosphorus slag - It is a by-product of phosphorus produced thermally in electric furnaces. At a temperature of 1300...1500°C, calcium phosphate interacts with coke carbon and silica, resulting in the formation of phosphorus and molten slag. The slag is drained from the furnaces in a fiery liquid state and granulated using the wet method. For 1 ton of phosphorus there are 10...12 tons of slag. On large chemical plants receive up to two million tons of slag per year. The chemical composition of phosphorus slag is close to the composition of blast furnace slag.
From phosphorus-slag melts it is possible to obtain slag pumice, cotton wool and cast products. Slag pumice is produced using conventional technology without changing the composition of phosphorus slag. It has a bulk bulk mass of 600...800 kg/m³ and a glassy, finely porous structure. Phosphorus slag wool is characterized by long thin fibers and a bulk density of 80...200 kg/m³. Phosphorus-slag melts can be processed into cast crushed stone using trench technology used in metallurgical enterprises.
b) Materials based on gypsum-containing and ferrous waste
The building materials industry's demand for gypsum stone currently exceeds 40 million tons. At the same time, the need for gypsum raw materials can be mainly satisfied by gypsum-containing waste from the chemical, food, and forestry industries. chemical industry. In 1980, in our country, the output of waste and by-products containing calcium sulfates reached approximately 20 million tons per year, including phosphogypsum - 15.6 million tons.
Phosphogypsum - waste sulfuric acid treatment of apatites or phosphorites into phosphoric acid or concentrated phosphorus fertilizers. It contains 92...95% gypsum dihydrate with a mechanical admixture of 1...1.5% phosphorus pentoxide and a certain amount of other impurities. Phosphogypsum has the form of sludge with a moisture content of 20...30% with a high content of soluble impurities. The solid phase of the sludge is finely dispersed and more than 50% consists of particles less than 10 microns in size. The cost of transporting and storing phosphogypsum in dumps is up to 30% of the total cost of structures and operation of the main production.
In the production of phosphoric acid using the hemihydrate extraction method, the waste product is calcium sulfate phosphohemihydrate, containing 92...95% - the main component of high-strength gypsum. However, the presence of passivating films on the surface of the hemihydrate crystals significantly inhibits the manifestation of the astringent properties of this product without special technological treatment.
With conventional technology, gypsum binders based on phosphogypsum are of low quality, which is explained by the high water demand of phosphogypsum due to the high porosity of the hemihydrate as a result of the presence of large crystals in the feedstock. If the water requirement of ordinary building gypsum is 50...70%, then to obtain a test of normal density from phosphogypsum binder without additional processing, 120...130% of water is required. The construction properties of phosphogypsum and the impurities contained in it have a negative effect. This influence is somewhat reduced by grinding phosphogypsum and forming products using the vibration laying method. In this case, the quality of phosphogypsum binder increases, although it remains lower than that of building gypsum from natural raw materials.
At MISS, based on phosphogypsum, a composite binder with increased water resistance was obtained, containing 70...90% α-hemihydrate, 5...20% Portland cement and 3...10% pozzolanic additives. With a specific surface of 3000...4500 cm²/g, the water requirement of the binder is 35...45%, setting begins in 20...30 minutes, ends in 30...60 minutes, the compressive strength is 30...35 MPa, the softening coefficient is 0.6...0 ,7. waterproof binder is obtained by hydrothermal treatment in an autoclave of a mixture of phosphogypsum, Portland cement and additives containing active silica.
In the cement industry, Phosphogypsum is used as a mineralizer during clinker firing and instead of natural gypsum as an additive to regulate the setting of cement. The addition of 3...4% to the sludge allows you to increase the clinker saturation coefficient from 0.89...0.9 to 0.94...0.96 without reducing the productivity of the furnaces, increase the durability of the lining in the sintering zone due to the uniform formation of a stable coating and obtain easily grindable clinker. The suitability of phosphogypsum for replacing gypsum when grinding cement clinker has been established.
The widespread use of phosphogypsum as an additive in cement production is possible only when it is dried and granulated. The moisture content of granulated phosphogypsum should not exceed 10...12%. The essence of the basic phosphogypsum granulation scheme is to dehydrate part of the original phosphogypsum sludge at a temperature of 220...250 ° C to the state of soluble anhydride, followed by mixing it with the rest of the phosphogypsum. When phosphoanhydride is mixed with phosphogypsum in a rotating drum, the dehydrated product is hydrated by the free moisture of the starting material, resulting in solid granules of phosphogypsum dihydrate. Another method of granulating phosphogypsum is also possible - with the strengthening additive of pyrite cinders.
In addition to the production of binders and products based on them, other ways of recycling gypsum-containing waste are known. Experiments have shown that adding up to 5% phosphogypsum to the charge during brick production intensifies the drying process and helps improve the quality of products. This is explained by the improvement of the ceramic-technological properties of clay raw materials due to the presence of the main component of phosphogypsum - calcium sulfate dihydrate.
The most widely used of ferrous wastes is pyrite cinders. In particular, in the production of Portland cement clinker they are used as a corrective additive. However, cinders consumed in the cement industry constitute only a small part of their total output in sulfuric acid plants that consume sulfur pyrites as the main feedstock.
A technology for the production of high-iron cements has been developed. The starting components for the production of such cements are chalk (60%) and pyrite cinders (40%). The raw material mixture is fired at a temperature of 1220…1250º C. High-iron cements are characterized by normal setting times when up to 3% gypsum is added to the raw material mixture. Their compressive strength under conditions of water and air-moist hardening for 28 days. corresponds to grades 150 and 200, and when steamed in an autoclave it increases by 2...2.5 times. High-iron cements are non-shrinking.
Pyrite cinders in the production of artificial concrete aggregates can serve as both an additive and the main raw material. The addition of pyrite cinders in an amount of 2...4% of the total mass is introduced to increase the gas-forming ability of clays when producing expanded clay. This is facilitated by the decomposition of pyrite residues in cinders at 700...800º C with the formation of sulfur dioxide and the reduction of iron oxides under the influence of organic impurities present in clay raw materials, with the release of gases. Ferrous compounds, especially in ferrous form, act as fluxes, causing liquefaction of the melt and a decrease in the temperature range of changes in its viscosity.
Iron-containing additives are used in the production of ceramic wall materials to reduce the firing temperature, improve quality and improve color characteristics. Positive results are obtained by preliminary calcination of cinders to decompose impurities of sulfides and sulfates, which form gaseous products during firing, the presence of which reduces the mechanical strength of products. It is effective to introduce 5...10% cinders into the charge, especially in raw materials with a low amount of flux and insufficient sintering.
In the production of facade tiles using semi-dry and shlinker methods, calcined cinders can be added to the mixture in an amount of 5 to 50% by weight. The use of cinders makes it possible to produce colored ceramic facade tiles without additionally introducing chamotte into the clay. At the same time, the firing temperature of tiles made of refractory and refractory clays is reduced by 50...100° C.
c) Materials from forest chemical waste and wood processing
For the production of building materials, the most valuable raw materials from chemical industry waste are slag from the electrothermal production of phosphorus, gypsum-containing and lime waste.
Waste from chemical-technological production includes: worn tires and secondary polymer raw materials, as well as a number of by-products of construction materials enterprises: cement dust, sediments in water purification devices of asbestos-cement enterprises, broken glass and ceramics. Waste accounts for up to 50% of the total mass of processed wood, most of it is currently burned or disposed of.
Construction materials enterprises located near hydrolysis plants can successfully utilize lignin, one of the most capacious wood chemical wastes. The experience of a number of brick factories allows us to consider lignin an effective burn-out additive. It mixes well with other components of the charge, does not impair its forming properties and does not complicate cutting the timber. The greatest effect of its use occurs when the quarry moisture content of the clay is relatively low. Lignin pressed into raw materials does not burn when dried. The combustible part of lignin completely evaporates at a temperature of 350...400º C, its ash content is 4...7%. To ensure the standard mechanical strength of ordinary clay bricks, lignin should be introduced into the forming charge in an amount of up to 20...25% of its volume.
In the production of cement, lignin can be used as a plasticizer of raw sludge and an intensifier for grinding the raw mixture and cement. The dosage of lignin in this case is 0.2…0.3%. The liquefying effect of hydrolytic lignin is explained by the presence of phenolic substances in it, which effectively reduce the viscosity of limestone-clay suspensions. The effect of lignin during grinding is mainly to reduce the adhesion of small fractions of the material and their adhesion to the grinding media.
Wood waste without preliminary processing (sawdust, shavings) or after grinding (chips, crushed wood, wood wool) they can serve as fillers in building materials based on mineral and organic binders; these materials are characterized by low bulk density and thermal conductivity, as well as good workability. Impregnation of wood fillers with mineralizers and subsequent mixing with mineral binders ensures the biostability and fire resistance of materials based on them. General disadvantages of wood-filled materials are high water absorption and relatively low water resistance. According to their purpose, these materials are divided into thermal insulation and structural and thermal insulation.
The main representatives of the group of materials based on wood fillers and mineral binders are wood concrete, fiberboard and sawdust concrete.
Arbolit - lightweight concrete on aggregates of plant origin, pre-treated with a mineralizer solution. It is used in industrial, civil and agricultural construction in the form of panels and blocks for the construction of walls and partitions, floor slabs and building coverings, heat-insulating and sound-proofing slabs. The cost of buildings made of wood concrete is 20...30% lower than those made of brick. Arbolite structures can be operated at a relative indoor air humidity of no more than 75%. At high humidity, a vapor barrier layer is required.
Fibrolite unlike wood concrete, it includes wood wool as a filler and at the same time a reinforcing component - shavings from 200 to 500 mm long, 4...7 mm wide. and thickness 0.25...0.5 mm. Wood wool is obtained from non-commercial wood of coniferous, less commonly, deciduous trees. Fiberboard is characterized by high sound absorption, easy workability, nailability, and good adhesion to the plaster layer and concrete. The technology for the production of fiberboard includes the preparation of wood wool, its treatment with a mineralizer, mixing with cement, pressing of the boards and their heat treatment.
Sawdust concrete – This is a material based on mineral binders and sawdust. These include xylolite, xyloconcrete and some other materials similar to them in composition and technology.
Xylolite is an artificial building material obtained by hardening a mixture of magnesium binder and sawdust, mixed with a solution of magnesium chloride or sulfate. Xylolite is mainly used for installing monolithic or prefabricated floor coverings. The advantages of xylolite floors are a relatively low heat absorption coefficient, hygiene, sufficient hardness, low abrasion, and the possibility of a variety of colors.
Xyloconcrete - a type of lightweight concrete, the filler of which is sawdust, and the binder is cement or lime and gypsum; xyloconcrete with a volumetric mass of 300...700 kg/m³ and a compressive strength of 0.4...3 MPa is used as thermal insulation, and with a volumetric mass of 700...1200 kg /m³ and compressive strength up to 10 MPa - as a structural and thermal insulation material.
Laminated wood is one of the most effective building materials. It can be layered or made from veneer (plywood, laminated plastic); massive from lump waste from sawmilling and woodworking (panels, panels, beams, boards) and combined (joint slabs). The advantages of laminated wood are low bulk density, water resistance, and the ability to produce complex-shaped products and large structural elements from small-sized materials. In glued structures, the influence of anisotropy of wood and its defects is weakened, they are characterized by increased clay resistance and low flammability, and are not subject to shrinkage and warping. Glued laminated wood structures often successfully compete with steel and reinforced concrete structures in terms of time and labor costs during the construction of buildings, and resistance during the construction of an aggressive air environment. Their use is effective in the construction of agricultural and industrial enterprises, exhibition and trade pavilions, sports complexes, prefabricated buildings and structures.
Chipboards – This is a material obtained by hot pressing of crushed wood mixed with binders - synthetic polymers. The advantages of this material are the uniformity of physical and mechanical properties in various directions, relatively small linear changes at variable humidity, and the possibility of high mechanization and automation of production.
Building materials based on some wood waste can be produced without the use of special binders. Wood particles in such materials are bonded as a result of the convergence and interweaving of fibers, their cohesive ability and physicochemical bonds that arise during the processing of the press mass at high pressure and temperature.
Fiberboards are produced without the use of special binders.
Fiberboards – a material formed from a fibrous mass followed by heat treatment. Approximately 90% of all fibreboards are made from wood. The raw materials are non-commercial wood and waste from sawmills and woodworking industries. Boards can be obtained from the fibers of bast plants and from other fibrous raw materials that have sufficient strength and flexibility.
The group of wood plastics includes: Wood laminates– a material made from veneer sheets impregnated with a resole-type synthetic polymer and glued together as a result of thermal pressure treatment, lignocarbohydrate and piezothermoplastics produced from sawdust by high-temperature processing of the press mass without the introduction of special binders. The technology of lignocarbohydrate plastics consists of preparing, drying and dosing wood particles, molding the carpet, and cold pressing it , hot pressing and cooling without releasing pressure. The scope of application of lignocarbohydrate plastics is the same as that of wood fiber and particle boards.
Piezothermoplastics can be made from sawdust in two ways - without pre-treatment and with hydrothermal treatment of the raw materials. According to the second method, conditioned sawdust is processed in autoclaves with steam at a temperature of 170...180º C and a pressure of 0.8...1 MPa for 2 hours. The hydrolyzed press mass is partially dried and, at a certain humidity, is successively subjected to cold and hot pressing.
Floor tiles with a thickness of 12 mm are produced from piezothermoplastics. The starting raw materials can be sawdust or crushed coniferous and deciduous wood, flax or hemp fire, reeds, hydrolyzed lignin, and dun.
d) Disposal of own waste in the production of building materials
The experience of enterprises in the Crimean Autonomous Republic that develop limestone-shell rock to produce wall piece stone shows the effectiveness of producing shell-concrete blocks from stone sawing waste. The blocks are formed in horizontal metal molds with hinged sides. The bottom of the mold is covered with a shell rock solution 12..15 mm thick to create an internal textured layer. The form is filled with coarse-pored or fine-grained shell concrete. The texture of the outer surface of the blocks can be created with a special solution. Shell-concrete blocks are used for laying foundations and walls in the construction of industrial and residential buildings.
In cement production, as a result of processing finely dispersed mineral materials, significant amount dust, Total Collected dust at cement plants can account for up to 30% of the total volume of products produced. Up to 80% of the total amount of dust is emitted with gases from clinker kilns. The dust removed from the furnaces is a polydisperse powder, containing 40...70 in the wet production method, and up to 80% in the dry production method, of fractions with a size of less than 20 microns. Mineralogical studies have established that the dust contains up to 20% clinker minerals, 2...14% free calcium oxide and from 1 to 8% alkalis. The bulk of the dust consists of a mixture of baked clay and undecomposed limestone. The composition of dust depends significantly on the type of furnace, the type and properties of the raw materials used, and the method of collection.
The main direction of dust disposal at cement plants is its use in the cement production process itself. Dust from the dust settling chambers is returned to the rotary kiln along with the sludge. The main amount of free calcium oxide, alkalis and sulfuric anhydride. The addition of 5...15% of such dust to the raw sludge causes its coagulation and a decrease in fluidity. With an increased content of alkali oxides in the dust, the quality of the clinker also decreases.
Asbestos-cement waste contains large amounts of hydrated cement minerals and asbestos. When fired, as a result of dehydration of the hydrate components of cement and asbestos, they acquire astringent properties. Optimal temperature firing is in the range of 600…700º C. In this temperature range, the dehydration of hydrosilicates is completed, asbestos decomposes and a number of minerals capable of hydraulic hardening are formed. Binders with pronounced activity can be obtained by mixing thermally treated asbestos-cement waste with metallurgical slag and gypsum. Cladding tiles and floor tiles are made from asbestos-cement waste.
An effective type of binder in compositions made from asbestos-cement waste is liquid glass. Facing slabs from a mixture of dried and powdered asbestos-cement waste and liquid glass solution with a density of 1.1...1.15 kg/cm³ are produced at a specific pressing pressure of 40...50 MPa. In a dry state, these slabs have a bulk density of 1380...1410 kg/m³, a bending strength of 6.5...7 MPa, and a compressive strength of 12...16 MPa.
Thermal insulation materials can be made from asbestos-cement waste. Products in the form of slabs, segments and shells are obtained from burnt and crushed waste with the addition of lime, sand and gas-forming agents. Aerated concrete based on binders made from asbestos-cement waste has a compressive strength of 1.9...2.4 MPa and a volumetric mass of 370...420 kg/m³. Waste from the asbestos-cement industry can serve as fillers for warm plasters, asphalt mastics and asphalt concretes, as well as fillers for concrete with high impact strength.
Glass waste is generated both during glass production and when glass products are used at construction sites and in everyday life. The return of cullet to the main technological process of glass production is the main direction of its recycling.
One of the most effective thermal insulation materials - foam glass - is obtained from cullet powder with gas generators by sintering at 800...900°. Foam glass slabs and blocks have a volumetric mass of 100...300 kg/m³, thermal conductivity of 0.09...0.1 W and compressive strength of 0.5...3 MPa.
When mixed with plastic clays, broken glass can serve as the main component of ceramic masses. Products from such masses are made using semi-dry technology and are distinguished by high mechanical strength. The introduction of broken glass into the ceramic mass reduces the firing temperature and increases the productivity of kilns. Glass-ceramic tiles are produced from a charge containing from 10 to 70% broken glass, crushed in a ball mill. The mass is moistened to 5...7%. The tiles are pressed, dried and fired at 750...1000º C. Water absorption of the tiles is no more than 6%. frost resistance more than 50 cycles.
Broken glass is also used as a decorative material in colored plasters, ground glass waste can be used as a powder for oil paint, an abrasive for making sandpaper and as a component of glaze.
In ceramic production, waste arises at various stages of the technological process. Drying waste after the necessary grinding serves as an additive to reduce the moisture content of the initial charge. Broken clay bricks are used after crushing as crushed stone in general construction work and in the production of concrete. Crushed brick has a volumetric bulk mass of 800...900 kg/m³; it can be used to produce concrete with a bulk mass of 1800...2000 kg/m³, i.e. 20% lighter than conventional heavy aggregates. The use of crushed brick is effective for the production of coarsely porous concrete blocks with a volumetric mass of up to 1400 kg/m³. The amount of broken bricks has sharply decreased due to containerization and comprehensive mechanization of loading and unloading bricks.
4. References:
Bozhenov P.I. Integrated use of mineral raw materials for the production of building materials. – L.-M.: Stroyizdat, 1963.
Gladkikh K.V. Slags are not waste, but valuable raw materials. – M.: Stroyizdat, 1966.
Popov L.N. Construction materials from industrial waste. – M.: Knowledge, 1978.
Bazhenov Yu.M., Shubenkin P.F., Dvorkin L.I. Use of industrial waste in the production of building materials. – M.: Stroyizdat, 1986.
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