Stone materials used in construction. Coursework: Natural and building materials
The use of natural building materials reduces the need to use artificial materials, which require more energy to produce and transport. Construction technologies using natural building materials are based on simple methods constructions that minimize environmental damage by reducing dependence on non-renewable resources.
Adobe or Adobe– one of the oldest building materials. Used for the construction of walls and fences in dry climates. Adobe is made from clay soil mixed with straw or other fibers, sand and water to strengthen it. The mixture is formed as necessary and dried in the sun. Most often, adobe comes in the form of bricks, which are then laid using the same mixture from which they are made. It is a cheap and fire-resistant environmentally friendly building material. Adobe buildings can be found in Asian countries. In Russia, similar houses are found in rural areas in the North Caucasus and in the steppes of the Altai Territory.
Cob
Cob is a building material consisting of clay, sand, straw, water and earth, similar to adobe. But, unlike adobe, pieces of clay are immediately laid into the wall on stone or concrete foundations, without forming blocks. Buildings made from this building material are fire-resistant, resistant to seismic activity and inexpensive. Cob has been used since ancient times and has recently gained popularity in green building. In addition, it can be used to create sculptures.
Bamboo
Bamboo is a durable and lightweight building material that, due to its rapid growth, is a rapidly renewable resource. In construction, bamboo is used for different purposes: for interior decoration; as reinforcement for concrete; in thatched houses, straw bales can be mounted on bamboo bases; walls and ceilings are also made from thick bamboo stems.
Straw bales
Straw is a renewable resource that has excellent thermal and sound insulation properties. Bales are formed from agricultural waste, straw remaining in the fields after harvesting. This is a lightweight and therefore easy to install material. Straw bales can be used as filling for a wood or metal frame that provides the “skeleton” and as load-bearing structures to support a roof.
Wood and logs
Tree is one of the most common building materials. Wood is a renewable resource and has good thermal insulation properties, strength and relative durability. Logs or what is considered firewood can also be used as a building material. When erecting buildings, they can be laid in such a way that their length equals the thickness of the wall. The logs can be fastened with a solution based on a mixture of cement, lime, clay, sand or sawdust.
Masonry
Ancient building material. Stones are used for a wide variety of purposes. Foundations, floors, walls, sidewalks, etc. are made from them. Natural stone can be laid on regular cement mortar or on a mixture of clay, sand and lime. It is best to build houses from natural stone in places with a hot climate, since the stone has a heat-accumulating effect. Those. During the day, the stone wall absorbs heat coming from outside, and at night it radiates it, maintaining the temperature in the rooms.
Bags of earth or sand
Bags of earth They are used for military purposes and are used to make defensive structures. They are also used for flood control. Bags of earth and sand have also found their use in the construction of houses. They can be used to create massive, durable walls that can withstand harsh weather. Bag houses are seismically resistant, so they can be built in places where earthquakes occur frequently.
Earth
Earth used for the construction of various types of housing. The rammed earth construction technique has been used since ancient times. This material is fireproof, durable and reliable. It is used mostly in hot and dry places, in Australia and the American southwest. Portland cement is used as a binder that is added to the soil to increase strength. To build the wall, blocks of pressed wet earth are stacked like bricks. It should be noted that not every land can be suitable for such construction; it must meet certain requirements.
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Ministry of Education and Science of the Republic of Kazakhstan
East Kazakhstan State Technical University named after. D. Serikbaeva
Department of Theory of Architecture and Engineering Graphics
in the discipline "Engineering Graphics"
Topic: Natural and building materials
Completed by: student of group 09-BZ-1
Abraimova A.S.
Accepted by: Associate Professor Tsymbal N.T.
Ust-Kamenogorsk
INTRODUCTION
1.1 Natural stone building materials: basalt, granite
1.2Non-metallic natural building materials: crushed stone, sand
INTRODUCTION
Natural building materials, obtained as a result of relatively simple mechanical processing of monolithic rocks while preserving their physical, mechanical and technological properties, are used in the form of slabs, blocks, side and facing stones, road paving stones, rubble stone, crushed stone, crushed sand, etc. Natural loose rocks are also used in huge quantities: boulders, gravel, sand, clay, etc. In addition, rocks are the most important raw materials for the production of artificial building materials (building ceramics, refractories, glass, cement, lime, etc.). Why are they subjected to complex types of mechanical and chemical processing?
The widespread use of natural raw materials is associated with the presence of favorable physical and chemical properties of numerous rocks. Already in the early period of his existence, man discovered on the surface of the earth and in its depths a multitude of natural materials, which fully satisfied his relatively limited needs. At subsequent stages of the development of human society, increased requirements for the quality of building stone appear and at the same time, methods of processing and processing natural raw materials to obtain materials of a different quality and properties, for example, turning ordinary clay into stone when firing it and obtaining stable properties of the finished product.
Rocks are simple and complex natural mineral aggregates that occupy large areas of the earth's crust and are distinguished by greater or lesser constancy of the chemical and mineral composition, structure, as well as certain conditions of occurrence. They make up the surface layers of the earth's crust with a thickness of about 15...60 km and form natural accumulations of valuable mineral raw materials.
1 NATURAL BUILDING MATERIALS: CONCEPTS AND ROLE IN SOCIAL PRODUCTION
1.1 Definition of “natural building materials”
During the construction, operation and repair of buildings and structures construction products and the structures from which they are erected are subject to various physical, mechanical, physical and technological influences.
Construction materials and products used in the construction, reconstruction and repair of various buildings and structures are divided into
1. natural
2. artificial
which in turn are divided into two main categories:
The main types of building materials and products are stone natural building materials and products made from them, binding materials, inorganic and organic forest materials and products from them, metal products. Depending on the purpose, conditions of construction and operation of buildings and structures, appropriate building materials are selected that have certain qualities and protective properties from exposure to various external environments. Taking these features into account, any building material must have certain construction and technical properties. For example, the material for the external walls of buildings must have the lowest thermal conductivity with sufficient strength to protect the room from the external cold; material for drainage and drainage structures - waterproof and resistant to alternating wetting and drying; The road surface material (asphalt, concrete) must have sufficient strength and low abrasion to withstand the loads from transport.
When classifying materials and products, it is necessary to remember that they must have good properties and qualities.
1.2Properties and qualities of natural building materials
Property is a characteristic of a material that manifests itself during its processing, application or operation.
Quality is a set of properties of a material that determine its ability to satisfy certain requirements in accordance with its purpose.
The properties of building materials and products are classified into four main groups:
· physical,
· mechanical,
· chemical,
· technological, etc.
Chemical materials include the ability of materials to resist the action of a chemically aggressive environment, causing exchange reactions in them leading to the destruction of materials, a change in their original properties: solubility, corrosion resistance, resistance to rotting, hardening.
Physical properties: average, bulk, true and relative density; porosity, humidity, moisture transfer, thermal conductivity.
Mechanical properties: strength limits in compression, tension, bending, shear, elasticity, plasticity, rigidity, hardness.
Technological properties: workability, heat resistance, melting, speed of hardening and drying.
Physical properties of building materials.
True density ρ is the mass of a unit volume of material in an absolutely dense state. ρ =m/Va, where Va is the volume in a dense state. [ρ] = g/cm³; kg/m³; t/m³. For example, granite, glass and other silicates are almost completely dense materials. Determination of true density: a pre-dried sample is crushed into powder, the volume is determined in a pycnometer (it is equal to the volume of the displaced liquid).
Average density ρm=m/Ve is the mass of a unit volume in its natural state. The average density depends on temperature and humidity: ρm=ρв/(1+W), where W is relative humidity, and ρв is the wet density.
Bulk Density(for bulk materials) - the mass per unit volume of loosely poured granular or fibrous materials.
Porosity P is the degree of filling of the material volume with pores. P=Vp/Ve, where Vp is the pore volume, Ve is the volume of material. Porosity can be open or closed.
Open porosity Po - pores communicate with environment and each other, are filled with water under normal saturation conditions (immersion in a bath of water). Open pores increase the permeability and water absorption of the material and reduce frost resistance.
Closed porosity Pz=P-Po. Increasing closed porosity increases the durability of the material and reduces sound absorption.
Porous material contains both open and closed pores
Hydro physical properties building materials. Water absorption of porous materials is determined using a standard method by keeping samples in water at a temperature of 20±2 °C. In this case, water does not penetrate into closed pores, that is, water absorption characterizes only open porosity. When removing samples from the bath, water partially flows out of large pores, so water absorption is always less than porosity. Water absorption by volume Wo(%) - the degree of filling the volume of the material with water: Wo=(mв-mc)/Ve*100, where mв is the mass of the material sample saturated with water; mc is the dry mass of the sample. Water absorption by mass Wm(%) is determined in relation to the mass of dry material Wm=(mw-mc)/mc*100. Wo=Wм*γ, γ is the volumetric mass of dry material, expressed in relation to the density of water (dimensionless value). Water absorption is used to evaluate the structure of the material using the saturation coefficient: kн = Wo/P. It can vary from 0 (all pores in the material are closed) to 1 (all pores are open). A decrease in kn indicates an increase in frost resistance.
Water permeability is the property of a material to allow water to pass under pressure. The filtration coefficient kf (m/h is the speed dimension) characterizes water permeability: kf = Vv*a/, where kf = Vv is the amount of water, m³, passing through a wall of area S = 1 m², thickness a = 1 m during time t = 1 hour with a difference in hydrostatic pressure at the wall boundaries p1 - p2 = 1 m of water. Art.
The water resistance of the material is characterized by grade W2; W4; W8; W10; W12, denoting one-sided hydrostatic pressure in kgf/cm², at which a concrete cylinder sample does not allow water to pass through under standard test conditions. The lower the kf, the higher the waterproof grade.
Water resistance is characterized by the softening coefficient kp = Rв/Rс, where Rв is the strength of the material saturated with water, and Rс is the strength of the dry material. kp varies from 0 (wetting clays) to 1 (metals). If kp is less than 0.8, then such material is not used in building structures located in water.
Hygroscopicity is the property of a capillary-porous material to absorb water vapor from the air. The process of absorbing moisture from the air is called sorption, it is caused by polymolecular adsorption of water vapor on the inner surface of the pores and capillary condensation. With an increase in water vapor pressure (that is, an increase in the relative humidity of the air at a constant temperature), the sorption moisture content of the material increases.
Capillary suction is characterized by the height of water rising in the material, the amount of absorbed water and the intensity of suction. A decrease in these indicators reflects an improvement in the structure of the material and an increase in its frost resistance.
Humidity deformations. Porous materials change their volume and size when humidity changes. Shrinkage is a reduction in the size of a material as it dries. Swelling occurs when the material is saturated with water. Thermophysical properties of the structure of materials.
Thermal conductivity is the property of a material to transfer heat from one surface to another. Nekrasov’s formula connects thermal conductivity λ [W/(m*C)] with the volumetric mass of the material, expressed in relation to water: λ=1.16√(0.0196 + 0.22γ2)-0.16. As temperature increases, the thermal conductivity of most materials increases. R - thermal resistance, R = 1/λ.
Heat capacity c [kcal/(kg*C)] is the amount of heat that must be imparted to 1 kg of material in order to increase its temperature by 1C. For stone materials, the heat capacity varies from 0.75 to 0.92 kJ/(kg*C). As humidity increases, the heat capacity of materials increases.
Fire resistance is the ability of a material to withstand prolonged exposure to high temperatures (from 1580 °C and above) without softening or deforming. Refractory materials are used for the internal lining of industrial furnaces. Refractory materials soften at temperatures above 1350 °C.
Fire resistance is the property of a material to resist the action of fire during a fire for a certain time. It depends on the combustibility of the material, that is, on its ability to ignite and burn. Fireproof materials - concrete, brick, steel, etc. But at temperatures above 600 °C, some fireproof materials crack (granite) or become severely deformed (metals). Refractory materials smolder under the influence of fire or high temperature, but after the fire ceases, their combustion and smoldering stops (asphalt concrete, wood impregnated with fire retardants, fiberboard, some foam plastics). Combustible materials burn with an open flame, they must be protected from fire by structural and other measures, and treated with fire retardants.
Linear thermal expansion. With a seasonal change in the ambient temperature and material by 50 °C, the relative temperature deformation reaches 0.5-1 mm/m. To avoid cracking, long-term structures are cut with expansion joints.
Frost resistance of building materials.
Frost resistance is the ability of a material saturated with water to withstand alternate freezing and thawing. Frost resistance is quantitatively assessed by the brand. The grade is taken to be the greatest number of cycles of alternating freezing to −20 °C and thawing at a temperature of 12-20 °C, which the material samples can withstand without reducing the compressive strength by more than 15%; after testing, the samples should not have visible damage - cracks, chipping (mass loss no more than 5%).
Mechanical properties of building materials
Elasticity is the ability to spontaneously restore its original shape and size after the cessation of external force.
Plasticity is the ability to change shape and size under the influence of external forces without collapsing, and after the cessation of external forces, the body cannot spontaneously recover. shape and size.
Permanent deformation is plastic deformation.
Relative deformation is the ratio of absolute deformation to the initial linear size (ε=Δl/l).
Elastic modulus - the ratio of stress to rel. deformations (E=σ/ε).
Strength - the property of a material to resist destruction under the influence of internal influences. stresses caused by external forces or others. Strength is assessed by tensile strength - temporary resistance R, determined for a given type of deformation. For fragile materials (brick, concrete), the main strength characteristic is the compressive strength. For metals. Steel - compressive strength is the same as tensile and bending. Since building materials are heterogeneous, the tensile strength is determined as the average result of a series of samples. The test results are influenced by the shape, dimensions of the samples, the state of the supporting surfaces, and the loading speed. Depending on their strength, materials are divided into brands and classes. Brands are written in kgf/cm², and classes in MPa. The class characterizes guaranteed strength. Strength class B is called the temporary compressive strength of standard samples (concrete cubes with an edge size of 150 mm), tested at the age of 28 days of storage at 20±2°C, taking into account the static variability of strength.
Structural quality coefficient: KKK = R/γ (strength per relative density), for the 3rd steel KKK = 51 MPa, for high-strength steel KKK = 127 MPa, heavy concrete KKK = 12.6 MPa, wood KKK = 200 MPa.
Hardness is an indicator characterizing the ability of materials to resist the penetration of another, more dense material into it. Hardness index: HB=P/F (F is the area of the imprint, P is the force), [HB]=MPa. Mohs scale: talc, gypsum, lime...diamond.
Abrasion is the loss of the initial mass of a sample when this sample passes a certain path along an abrasive surface. Abrasion: И=(m1-m2)/F, where F is the area of the abraded surface.
Wear - the ability of a material to resist both abrasive and impact loads. Wear is determined in a drum with or without steel balls.
2.TYPES OF NATURAL BUILDING MATERIALS
2.1Stone natural building materials
Stone natural building materials are building materials obtained as a result of mechanical processing of rocks: facing slabs, wall stones, crushed stone, gravel, rubble stone, etc.
Stone natural building materials are divided into:
-igneous rocks, as the name implies, were formed as a result of the cooling and crystallization of magma - a molten mass of predominantly silicate composition located in the depths of the earth's crust. Depending on the cooling conditions of the magma, igneous rocks are divided into deep rocks - granite, diorite, gabbro, labradorite; erupted - porphyry, diabase, basalt.
Sedimentary rocks were formed as a result of the destruction of rocks under the influence of external conditions or as a result of the precipitation of substances from any environment. By the nature of formation and composition, sedimentary rocks are clastic - mechanical deposits, which include sand, gravel, as well as clayey, chemo- and organogenic - these are dolomite, gypsum, magnesite, limestone, chalk, diatomite, tripoli.
-metamorphic rocks - gneisses, marble, quartzite, shales - were formed in the thickness of the earth's crust as a result of modification of sedimentary or igneous rocks under the influence of temperatures, pressure and other factors.
Natural stone materials are classified according to the following criteria:
Dry density - heavy (density more than 1800 kg/m3) and light (density less than 1800 kg/m3);
Compressive strength (MPa) - for grades 10-100 (heavy stone materials) and 11-20 (light);
Frost resistance (softening coefficient) - into groups 0.6; 0.75; 0.9 and 1.
Products made from natural stone are divided into sawn (protrusions up to 10 mm), rough hewn (protrusions up to 20 mm), roughly chipped (have two approximately parallel edges) and torn rubble stone.
Sawn facing slabs from natural stone (dense limestone, marble, granite, syenite, gabbro, labradorite, etc.) by sawing them with subsequent mechanical processing. The front surface of the slabs has a different texture - “rock”, lumpy, grooved, dotted, grooved, sawn, ground, polished, polished. They are used for cladding columns, individual sections of facades and plinths and interior cladding of monumental buildings, and for installing decorative floors in public buildings.
Chipped and hewn slabs no less than 100 mm thick are used to clad unique buildings, monuments and hydraulic structures.
Rubble stone is mined from dense sedimentary rocks and, less commonly, from igneous rocks. Tensile strength - no less than 0.75, stone weight - up to 40 kg. Rubble stone is used for laying the foundations of low-rise buildings.
Basalt is the most common extruded igneous rock on Earth. The texture of basalt is mostly dense, porous, the crystals are not visible to the naked eye, the color is dark, almost black. Basalt:
It has columnar separation in the form of multifaceted pillars closely adjacent to each other;
Occurs in the form of streams or covers;
Forms extensive basalt plateaus;
Makes up huge areas of the ocean floor;
It is used in construction as rubble stone, filler for concrete, for paving streets and in the production of cast stone products.
Granite (Italian granito, from Latin granum - grain) is an acidic igneous intrusive rock. It consists of quartz, plagioclase, potassium feldspar and micas - biotite and/or muscovite. Granites are very widespread in the continental crust. Effusive analogues of granites are rhyolites.
Application of granite:
In modern construction, granite is used so widely that, without exaggeration, it can be called a universal material. An experienced designer, using granite, will be able to completely transform your home, giving it additional elegance and respectability, or simply “shade off” certain features of your interior, adding some “zest” to it.
Granite can be used in construction as:
Floors, stairs. Granite is a material with a very low level of abrasion. Even if 1 million people walk along the stairs in your personal apartment in a year, they will be able to erase its steps by no more than 0.12 mm;
Various interior details. Window sills, cornices, baseboards, railings, furniture tabletops, coffee tables, bar counters, balusters, columns - the high strength of granite will allow these items to remain intact and unharmed for many years, and avoid mechanical damage from exposure to temperature and humidity;
Facade and interior finishing. Granite is a very ergonomic material that can provide you with a comfortable stay in the building;
Landscape design elements. Alpine hill, rock garden, Japanese gardens, decorative ponds - made of granite, these fashionable compositions will give your garden naturalness and originality.
Curbs, steps, paving stones. Granite is successfully used in places where greater “endurance” is required. It is resistant to mechanical stress, chemical contamination and temperature changes - it does not change its properties over hundreds of freezing and thawing cycles.
Facing embankments. Granite practically does not absorb moisture - accordingly, when the temperature drops, additional internal pressure from frozen water does not form in the pores of the stone, which can lead to the formation of cracks and destruction of the rock.
2.2 Non-metallic natural building materials
Non-metallic materials are sedimentary rocks, which are mined by open-pit mining in quarries. These include: clay, soil, concrete, sand, crushed stone, expanded clay, building stone, granite, limestone and other substances and minerals. Non-metallic materials are classified according to several indicators: dense and porous materials, natural, and these are gravel, sand, crushed stone.
Gravel, loose rock consisting of rolled rock fragments and minerals ranging in size from 1 to 10 mm in diameter. Based on their origin, gravel is divided into river, lake, sea and glacial. Gravel is used as a building material, as a coarse aggregate for concrete, and in road construction. Cemented gravel is called gravelite and has textures similar to sandy rocks. It is widespread among sedimentary formations.
The presence of gravel indicates intensive erosion of ancient strata and indicates the proximity of land, shallow water or uplifts, for example, positive forms of relief of the bottom of the basin. Crushed stone is an acute-angled fragment of rocks up to 100 mm in size, formed during their weathering and occurring in the form of loose or weakly cemented accumulations.
Crushed stone is a product of crushing rocks and artificial stone materials. For example, metallurgical slag, brick, in the form of angular pieces measuring 5-150 mm. Depending on their properties, they are used as concrete fillers, for ballasting railway tracks, in the construction of highways, hydraulic structures, etc.
Specifications non-metallic materials are a unique and irreplaceable natural component in any construction. High-quality construction sand, river sand, quarry sand, limestone crushed stone, granite crushed stone allow us to carry out construction work of excellent quality and at the highest level.
Sand is a sedimentary rock, as well as an artificial material consisting of rock grains. Very often it consists of almost pure quartz mineral (the substance is silicon dioxide). Widely used in building materials, for the reclamation of construction sites, for sandblasting, in the construction of roads, embankments, in residential construction for backfilling, in the improvement of courtyard areas, in the production of mortar for masonry, plastering and foundation work, used for concrete production , in road construction. In the production of reinforced concrete products, high-strength concrete, as well as in the production paving slabs, curbs, well rings use coarse sand (Mk 2.2 - 2.5). Fine construction sand is used to prepare covering mortars. River construction sand is quite widely used in various decorative (mixed with various dyes to obtain special structural coatings) and finishing works of the finished premises. Construction river sand is a component of asphalt concrete mixtures that are used in the construction and laying of roads (including for the construction of airfields). Medium coarse sand can be added as a filler for concrete or mortar.
Construction coarse sand is often used for the construction of bases and coatings for roads and airfields. Coarse sand is used in the construction of drainages and septic tanks, as sand filters large particles contained in the water mixture.
Construction sand does not form mixtures and does not enter into chemical reactions with water or binders, therefore it is used in mortars and concretes, since a skeleton is formed, which reduces hardening during shrinkage of concrete or mortars.
Among other things, the sand used in construction work, also differs in size. So, there are large sand grains, medium and small ones, which have their own specific meaning.
CONCLUSION
Having considered natural building materials in the course work. We came to the conclusion that there are a large number of them and they have been used by humans since ancient times and have a number of advantages: high strength and lightness, hygroscopicity, frost resistance, etc.
The course work examines the basic properties of building materials, the advantages and disadvantages of their use in construction. During the study, the following were studied:
1 NATURAL BUILDING MATERIALS: CONCEPTS AND ROLE IN SOCIAL PRODUCTION
1.1 Definition of “natural building materials”
1.2Properties and qualities of natural building materials
2.TYPES OF NATURAL BUILDING MATERIALS
2.1 Natural stone building materials: basalt, granite
2.2Non-metallic natural building materials: crushed stone, sand
REFERENCES
1. Davydenko O. B., Burov V. G., Volkhin K. A., Ivantsivskaya N. G., Burova V. G., Zakharova I. V., Ivantsivskoy N. G., eds., Ivantsivskaya N. G. - ed.
ENGINEERING GRAPHICS General course + CD Textbook 2nd ed., revised and additional.
2. Alexander Georgievich Domokeev. Publishing house " graduate School» 1988
3. Tutorial- Moscow: MIKHIS, 2006.- 173 p. Rybyev I.A.
4.Komar A.G.5 edition of the classic textbook on construction materials science. Construction materials and products.
5. http://www.glossary.ru
6. http://www.materialsworld.ru
7. http://www.gravel.ru
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Introduction
Materials are much deeper into our culture than many people realize. Necessary elements of our everyday life are transport, housing, communications, recreation, food production, and all of them depend to one degree or another on the choice of suitable materials.
From a historical point of view, the development and success of the social order are inextricably linked with the ability of people to produce and process materials to satisfy existing needs. Early civilizations were even identified by the names of the materials that people learned to use - Stone Age, Bronze Age, Iron Age.
In the early stages human existence people used an extremely limited number of materials (those that were available in nature - stones, wood, clay, animal skins, etc.). Over time, people learned to produce materials with properties superior to natural products (ceramics, metals, etc.). Later it was discovered that the properties of materials can be modified as a result of heat treatment or the addition of various substances to them.
It was only relatively recently (about 100 years ago) that scientists realized that there was a correspondence between the structural elements that make up the material and the material itself. All this led to the emergence of tens of thousands of different materials with very specific properties, which made it possible to satisfy the most complex needs modern society(polymers, glasses, fibers, etc.).
The advances of modern technology have made our existence more comfortable! This is because suitable materials have become available. Often the development of new technologies is preceded by an understanding of what determines the type of material. For example, the development of the automobile industry would have been impossible without the development of inexpensive steels and other suitable materials.
Nowadays, the development of numerous complex electronic devices is based on the use of components made from so-called semiconductor materials.
The more familiar a scientist or engineer is with the various characteristics of a material and the relationship between its structure and properties, as well as with the production technology of products, the more skillful and reliable his or her choice of material will be based on these criteria.
This work will help us understand what types of materials exist and where they are currently used. Let's consider their types and classification.
1. Types and classification of materials
material ceramics composite nanotechnology
Solid materials are generally classified into three main groups. These are metals, ceramics and polymers. This division is based primarily on the characteristics of the chemical structure and atomic structure of the substance. Most materials can be quite unambiguously classified into one group or another, although intermediate cases are also possible. In addition, it should be noted that there are composites that combine materials belonging to two or three of the listed groups. Below will be given brief description various types of materials and their comparative characteristics are given.
Another type of materials are advanced specialty materials intended for use in high-tech fields, such as semiconductors, biological materials, smart materials, and substances used in nanotechnology.
1.1 Metals
Metals (from Latin metallum - mine, mine) are a group of elements with characteristic metallic properties, such as high thermal and electrical conductivity, positive temperature coefficient of resistance, high ductility and metallic luster.
Of the 118 chemical elements discovered in at the moment(not all of them are officially recognized), metals include: 6 elements in the group of alkali metals (lithium, sodium, potassium, rubidium, cesium, francium, ununenium), 6 in the group of alkaline earth metals (beryllium, magnesium, calcium, strontium, barium and radium), 38 in the group of transition metals (see Table 1), 11 in the group of light metals (aluminum, gallium, indium, tin, thallium, lead, bismuth, germanium, antimony, polonium, flerovium), 7 in the group of semimetals (bismuth, antimony, polonium, arsenic, tellurium, tin), 14 in the lanthanide group (cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, dysprosium, herbium, erbium, thulium, ytterbium, lutetium) + lanthanum, 14 V group actinides (physical properties have not been studied for all elements) + actinium, outside certain groups beryllium and magnesium.
Thus, 96 of all discovered elements may be metals.
Most metals are present in nature in the form of ores and compounds. They form oxides, sulfides, carbonates and other chemical compounds. To obtain pure metals and their further use, it is necessary to isolate them from ores and carry out purification. If necessary, alloying and other processing of metals is carried out.
The science of metallurgy studies this. Metallurgy distinguishes ores of ferrous metals (based on iron) and non-ferrous (they do not contain iron, there are about 70 elements in total). Gold, silver and platinum are also precious (noble) metals. In addition, they are present in small quantities in sea water, plants, and living organisms (playing an important role).
It is known that the human body consists of 3% metals. Most of our cells contain calcium and sodium, concentrated in the lymphatic systems. Magnesium accumulates in muscles and nervous system, copper - in the liver, iron - in the blood.
Characteristic properties of metals
* Metallic luster (characteristic not only of metals: non-metals iodine and carbon in the form of graphite also have it)
*Good electrical conductivity
* Can be easily machined (ductility; however, some metals, such as germanium and bismuth, are not ductile)
* High density (usually metals are heavier than non-metals)
* High melting point, (exceptions: mercury, gallium, alkaline materials)
* Great thermal conductivity
* In reactions they are most often reducing agents
Physical properties of metals.
All metals (except mercury and, conditionally, francium) are in a solid state under normal conditions, but have different hardnesses. The hardness of metals can be determined using the Mohs scale (see Table 2).
Melting points range from -39°C (mercury) to 3410°C (tungsten). The melting point of most metals (except alkali metals) is high, but some metals, such as tin and lead, can be melted on a regular electric or gas stove.
Depending on their density, metals are divided into light (density 0.53 h 5 g/cm³) and heavy (5 h 22.5 g/cm³). The lightest metal is lithium (density 0.53 g/cm). It is currently impossible to name the heaviest metal, since the densities of osmium and iridium - the two heaviest metals - are almost equal (about 22.6 g / cm - exactly twice the density of lead), and it is extremely difficult to calculate their exact density: for this It is necessary to completely clean the metals, because any impurities reduce their density.
Most metals plastic, that is, the metal wire can be bent without breaking. This occurs due to the displacement of layers of metal atoms without breaking the bond between them. The most ductile are gold, silver and copper. Gold can be used to make foil 0.003 mm thick, which is used for gilding products. However, not all metals are ductile. Wire made of zinc or tin crunches when bent; When deformed, manganese and bismuth hardly bend at all, but immediately break. Plasticity also depends on the purity of the metal; Thus, very pure chromium is very ductile, but, contaminated with even minor impurities, it becomes brittle and harder.
All metals conduct electricity well; this is due to the presence in their crystal lattices of mobile electrons moving under the influence electric field. Silver, copper and aluminum have the highest electrical conductivity; for this reason, the latter two metals are most often used as wire materials. Sodium also has very high electrical conductivity; in experimental equipment, attempts are known to use sodium conductors in the form of thin-walled stainless steel pipes filled with sodium. Thanks to little specific gravity sodium, with equal resistance, sodium “wires” are much lighter than copper and even somewhat lighter than aluminum.
High thermal conductivity metals also depends on the mobility of free electrons. Therefore, the series of thermal conductivities is similar to the series of electrical conductivities, and the best conductor of heat, as well as electricity, is silver. Sodium also finds use as a good conductor of heat; It is widely known, for example, that sodium is used in valves of automobile engines to improve their cooling.
The smooth surface of metals reflects a large percentage of light - this phenomenon is called metallic shine. However, when in powder form, most metals lose their luster; aluminum and magnesium, however, retain their shine even in powder. Aluminum, silver and palladium reflect light most well - mirrors are made from these metals. Rhodium is sometimes used to make mirrors, despite its extremely high price: due to its much greater hardness and chemical resistance than silver or even palladium, the rhodium layer can be much thinner than the silver one.
The color of most metals is approximately the same - light gray with a bluish tint. Gold, copper and cesium are yellow, red and light yellow, respectively.
Metal classification
Black. These are metals that contain iron. They may have small amounts of other metals or other elements added to give the required properties (chromium, manganese, vanadium, etc.).
Non-ferrous metals- metals that do not contain iron. They do not have magnetic properties and, as a rule, are more resistant to corrosion than ferrous metals (aluminum, copper, tin, etc.).
All non-ferrous metals have magnetic properties and offer little resistance to corrosion
Pure metals- consists of only one element. This means that it only has one type of atom in it. Common pure metals: aluminum, copper, iron, lead, zinc, tin, silver and gold.
Alloys. Materials belonging to this group include one or more metals (such as iron, aluminum, copper, titanium, gold, nickel), and often also some non-metallic elements (such as carbon, nitrogen or oxygen) in relatively small quantities. quantities.
Alloys consist of a base (one or several metals), small additives of alloying and modifying elements specially introduced into the alloy, as well as impurities that have not been removed (natural, technological and accidental).
Alloys are one of the main structural materials. Among them, alloys based on iron and aluminum are of greatest importance. More than 5 thousand alloys are used in technology.
The atoms in metals and alloys are arranged in a very perfect order. Moreover, compared to ceramics and polymer materials The density of metals is relatively high.
In terms of mechanical properties, all these materials are relatively rigid and durable. In addition, they have a certain ductility (i.e., the ability to undergo large deformations without destruction) and resistance to destruction, which has ensured their widespread use in a variety of structures.
1 .2 Ceramics
Ceramics (ancient Greek kEsbmpt - clay) - products from inorganic materials(for example, clay) and their mixtures with mineral additives, manufactured under high temperature followed by cooling. In the narrow sense, the word ceramics means clay that has been fired.
Ceramics have become widespread in all areas of life - in everyday life (various dishes), construction (bricks, tiles, pipes, tiles, tiles, sculptural parts), in technology, in railway, water and air transport, in sculpture and applied art.
Depending on the structure there are thin ceramics (vitreous or fine-grained shard) and rude (coarse-grained shard). The main types of fine ceramics are porcelain, semi-porcelain, faience, majolica. The main type of coarse ceramics is pottery ceramics. In addition, there are carbide, boride, silicide, etc. ceramics.
Porcelain has a dense sintered shard white(sometimes with a bluish tint) with low water absorption (up to 0.2%), when tapped, it produces a high-pitched melodic sound, and can be translucent in thin layers. The glaze does not cover the edge of the bead or the base of the porcelain piece. The raw materials for porcelain are kaolin, sand, feldspar and other additives.
Depending on the composition of the porcelain mass, porcelain is divided into soft And solid. Soft Porcelain differs from hard porcelain not in hardness, but in the fact that when firing soft porcelain, more liquid phase is formed than when firing hard porcelain, and therefore there is a higher risk of deformation of the workpiece during firing.
Hard porcelain, which contains 47-66% kaolin, 25% quartz and 25% feldspar, is richer in kaolin (alumina) and poorer in fluxes. To obtain the required translucency and density, it requires a higher firing temperature (from 1400°C to 1460°C).
Soft porcelain more diverse in chemical composition and consists of 25-40% kaolin, 45% quartz and 30% feldspar. The firing temperature does not exceed 1300-1350°C. Soft porcelain is used primarily for the manufacture of artistic products, and hard porcelain is usually used in technology (electrical insulators) and in everyday use (dishes).
One type of soft porcelain is bone china, which contains up to 50% bone ash, as well as kaolin, quartz, etc., and is particularly white and thin-walled. and translucency.
Porcelain is usually glazed. White, matte, unglazed porcelain is called bisque. In the era of classicism
biscuit was used as inserts in furniture products.
Faience has a porous white shard with a yellowish tint, the porosity of the shard is 9 - 12%. Due to the high porosity, earthenware products are completely covered with a colorless glaze of low heat resistance. Earthenware is used to produce tableware for everyday use. The raw materials for the production of earthenware are white-burning clays with the addition of chalk and quartz sand.
Opak is considered the highest grade of earthenware.
Semi-porcelain in terms of properties it occupies an intermediate position between porcelain and earthenware, the shard is white, water absorption is 3 - 5%, it is used in the production of tableware.
Majolica(from Italian Maiolica - Mallorca) - a type of ceramic made from fired clay using painted glaze. Using the majolica technique, decorative panels, frames, tiles, etc., as well as tableware and even monumental sculptures are made.
Majolica has a porous shard, water absorption is about 15%, the products have a smooth surface, shine, thin walls, are covered with colored glazes and can have decorative relief decorations. Casting is used to make majolica. Raw materials - white-burning clays (faience majolica) or red-burning clays (pottery majolica), flux, chalk, quartz sand.
Pottery ceramics have a red-brown shard (red-burning clays are used), high porosity, water absorption up to 18%. Products can be covered with colorless glazes or painted with colored clay paints - engobes.
Transparent ceramics. Historically, ceramic materials are opaque due to the nature of their structure. However, sintering nanometer-sized particles has made it possible to create transparent ceramic materials with properties (range of operating wavelengths, dispersion, refractive index) that lie outside the standard range of values for optical glasses.
Nanoceramics - ceramic nanostructured material (eng. nanoceramics) - a compact material based on oxides, carbides, nitrides, borides and other inorganic compounds, consisting of crystallites (grains) with an average size of up to 100 nm. Nanoceramics are used for the production of armored ceramics, microwave generator lamps, substrates for semiconductor devices, insulators for vacuum arc extinguishing chambers, power semiconductor devices and electron-optical converters in night vision devices.
Ceramics are a group of materials that occupy an intermediate position between metals and non-metallic elements. How general rule, the class of ceramics includes oxides, nitrides and carbides. For example, some of the most popular types of ceramics consist of aluminum oxide (Al2O3), silicon dioxide (SiO2), silicon nitride (Si3N4). In addition, substances that many call traditional ceramic materials include various clays (in particular those used to make porcelain), as well as concrete and glass. As for mechanical properties, ceramics are relatively hard and durable materials, comparable in these characteristics to metals. In addition, typical types of ceramics are very hard. However, ceramics are exclusively brittle material(almost complete lack of ductility) and has poor resistance to destruction. All typical types of ceramics do not conduct heat And electric current(i.e. their electrical conductivity is very low).
Ceramics are characterized by higher high temperature resistance and harmful environmental influences. In terms of their optical properties, ceramics can be transparent, translucent or completely opaque, and some oxides, such as iron oxide (Fe2O3), have magnetic properties.
1 .3 Compositetion materials
Composite material is an artificially created heterogeneous continuous material consisting of two or more components with a clear interface between them. In most composites (with the exception of layered ones), the components can be divided into matrix and included in it reinforcing elements. In composites for structural purposes, reinforcing elements usually provide the necessary mechanical characteristics of the material (strength, stiffness, etc.), and the matrix (or binder) ensures the joint operation of the reinforcing elements and their protection from mechanical damage and aggressive chemical environments.
The mechanical behavior of the composition is determined by the relationship between the properties of the reinforcing elements and the matrix, as well as the strength of the bond between them. The effectiveness and performance of the material depend on the right choice the original components and the technology of their combination, designed to ensure a strong connection between the components while maintaining their original characteristics.
As a result of the combination of reinforcing elements and the matrix, a complex of properties of the composition is formed, which not only reflects the initial characteristics of its components, but also includes properties that the isolated components do not possess. In particular, the presence of interfaces between the reinforcing elements and the matrix significantly increases the crack resistance of the material, and in compositions, unlike homogeneous metals, an increase in static strength does not lead to a decrease, but, as a rule, to an increase in fracture toughness characteristics.
To create the composition, a variety of reinforcing fillers and matrices are used. These are getinax and textolite (laminated plastics made of paper or fabric glued with thermosetting glue), glass and graphite plastic (fabric or wound fiber made of glass or graphite, impregnated with epoxy adhesives), plywood, etc. There are materials in which thin fibers are made of high-strength alloys are filled with aluminum mass. Damask steel is one of the oldest composite materials. In it, thin layers (sometimes threads) of high-carbon steel are “glued” together with soft low-carbon iron.
Recently, materials scientists have been experimenting with the goal of creating materials that are more convenient to manufacture, and therefore more efficient. cheap materials. Self-growing crystalline structures glued into a single mass with polymer glue (cements with the addition of water-soluble adhesives), thermoplastic compositions with short reinforcing fibers, etc. are being studied.
One of the most popular and familiar composite materials is fiberglass. This material consists of short glass fibers embedded in a polymer matrix, usually epoxy or polyester resin. Glass fibers have high strength and rigidity, but they are brittle. At the same time, the polymer matrix is plastic, but its strength is low. The combination of these substances leads to the production of a relatively rigid and high-strength material, which, nevertheless, has sufficient ductility and flexibility.
Another example of a technologically important composite is carbon fiber reinforced plastics- carbon fiber reinforced polymers (CFRP). In these materials, carbon fibers are placed in a polymer matrix.
Materials of this type are stiffer and more durable compared to fiberglass, but at the same time more expensive. CFRPs are used in aerospace engineering and in high-quality sports equipment such as bicycles, golf clubs, tennis rackets, skis and snowboards.
Advantages of composite materials.
The main advantage of a composite is that the material and structure are created simultaneously. The exception is prepregs, which are semi-finished products for the manufacture of structures. It’s worth mentioning right away that composites are created to perform these tasks, and therefore cannot accommodate everything possible benefits, but when designing a new composite, the engineer is free to give it characteristics that are significantly superior to those of traditional materials in fulfilling a given purpose in a given mechanism, but inferior to them in some other aspects. This means that a composite cannot be better than a traditional material in everything, that is, for each product the engineer carries out all the necessary calculations and only then chooses the optimum between materials for production.
§ high specific strength (strength 3500 MPa)
§ high rigidity (elastic modulus 130…140 - 240 GPa)
§ high wear resistance
§ high fatigue strength
§ It is possible to produce dimensionally stable structures from CM
§ lightness
Moreover, different classes of composites may have one or more advantages. Some benefits cannot be achieved simultaneously.
Disadvantages of composite materials.
* High cost. It is determined by the need for high science-intensive production, the need for special expensive equipment and raw materials, and therefore developed industrial production and the country’s scientific base.
* Anisotropy of properties - variability of properties from sample to sample. To compensate for anisotropy, the safety factor is increased, which can offset the advantage of CM in specific strength. An example of this is the composite keel fighter MiG-29, designed with a safety factor that is a multiple of the standard aviation coefficient of 1.5. As a result, this led to the fact that the composite keel of the Mig-29 turned out to be equal in weight to the design of a classic keel made of duralumin.
* Low operational manufacturability. Composite materials have low manufacturability, maintainability and high operating costs. This is due to the need to use special labor-intensive methods and special tools for the modification and repair of objects made of CM. Often, objects made from CM are not subject to any modification or repair at all.
* High specific volume is a significant drawback when using CM in areas with strict restrictions on the occupied volume. This applies, for example, to fighter aircraft, where the placement of equipment and fuel is limited by the extremely small available volumes.
* Toxicity. When operating CMs, vapors are released that are often toxic. If CM is used to make products that will be located in close proximity to humans (the composite fuselage of the Boeing 787 Dreamliner may serve as such an example), then additional research into the effects of CM components on humans is required to approve the materials used in the manufacture of CM.
* Low impact strength forces to increase the safety factor. It also poses a serious danger due to the fact that significant damage caused to an object made from CM can often be detected only by instrumental control methods.
* Hygroscopicity- tendency to absorb moisture. With long-term operation and repeated temperature transitions through 0 Celsius, this leads to the destruction of the internal structure of the CM (the effect is similar in nature to the destruction of highways in the off-season). So one of possible reasons The plane crash en: American Airlines Flight 587, in which the composite keel was torn from the fuselage, is called the destruction of the structure of the composite keel from the effects of freezing cycles of water that penetrated into the structure of the CM. Similar examples separation of the composite fin from the fuselage took place in Russia.
Applications
Consumer goods (reinforced concrete, car tires, fishing rods), metal composites (skis, poles, hockey sticks, skates, canoes, oars), mechanical engineering (pistons, connecting rods, etc.), aviation (aircraft, artificial satellites), astronautics ( heat-insulating coatings, space probes), military equipment (armor, body armor).
2 . Progressive materials
Materials that are intended for use in high-tech products (“high-tech”) are sometimes conventionally defined by the term “progressive” materials. By high technology we usually mean devices or products whose operation is based on the use of complex modern principles. These products include various electronic equipment, in particular digital video-audio cameras, CD/DVD players, computers, fiber optic systems, as well as space satellites, aerospace and rocket technology products.
Advanced materials are essentially the typical substances discussed above, but with improved properties, but also new materials with outstanding characteristics. These materials can be metals, ceramics or polymers, but their cost is usually very high. Advanced materials also include semiconductors, biomaterials, and what we call “materials of the future.” These are so-called “smart” materials and nanotechnology products, which are intended, for example, for the manufacture of lasers, integrated circuits, magnetic information storage, liquid crystal displays and optical fibers.
2 . 1 Semiconductornew materials
Semiconductor materials are substances that noticeably change their electrical properties under the influence of various external influences - temperature, lighting, electric and magnetic fields, external pressure.
Substances with clearly defined semiconductor properties in a wide temperature range, including room temperature (~ 300 K), are the basis for the creation of semiconductor devices. The specific electrical conductivity y at 300 K is 104?10~10 Ohm?1 cm?1 and increases with increasing temperature. Semiconductor materials are characterized by high sensitivity of electrical properties to external influences (heating, irradiation, deformation, etc.), as well as to the content of structural defects and impurities.
They differ from metals in that the carriers of electric current in them are created by thermal motion, light, electron flow, etc. source of energy. Without thermal motion (near absolute zero), semiconductors are insulators. With increasing temperature, the electrical conductivity of semiconductors increases and, when melted, has a metallic character.
Semiconductors are new materials with which, throughout last decades manages to solve a number of extremely important electrical problems. There are currently over twenty various areas, in which, with the help of semiconductors, the most important issues of operating machines and mechanisms, controlling production processes, obtaining electrical energy, amplifying high-frequency oscillations and generating radio waves, creating heat or cold using electric current, and for carrying out many other processes are resolved.
Semiconductor materials according to their structure are divided into crystalline, solid, amorphous and liquid.
Crystalline semiconductor materials According to their chemical composition, they are divided into the following main groups: uhelementary semiconductors(carbon, diamond, graphite, gray tin) have a diamond-type crystal lattice, compounds of type AIIIBV of elements of group III and V periodic table have a mainly crystalline structure of the sphalerite type (direct gap - GaAs, InP, InAs, InSb, GaN, indirect gap - GaP, AlAs, series of complex solid melts - GaxAl1-xAs, GaAsxP1-x, etc.), With combinations of elements of group VI(O, S, Se, Te) with elements Groups I-V periodic system, as well as with transition metals and rare earth elements (CdTe, CdS, ZnTe, ZnSe, ZnO, ZnS, solid melts - CdxHg1-xTe, CdxHg1-xSe, CdTexSe1-x), TSwarm joints type AIIBIVCV2 crystallize mainly in the chalcopyrite lattice (CuInSe2, CdSnAs2, CdGeAs2, ZnSnAs2), Tosilicon arbide SiC- the only chemical compound formed by elements of group IV. It has semiconductor properties in all structural modifications: β-SiC (sphalerite structure); b-SiC (hexagonal structure), having about 15 varieties. One of the most refractory and wide-gap among widely used semiconductor materials.
Non-crystalline semiconductor materials.
Typical representatives of this group are glassy semiconductor materials - chalcogenide ( alloys Tl, P, As, Sb, Bi with S, Se, Te - As2Se3-As2Te3, Tl2Se-As2Se3) , And oxide(composition of the V2O5-P2O5-ROx type (R-metal I-IV gr.) and are characterized by a specific electrical conductivity of 10? 4? 10? 5 Ohm? 1 cm? 1. All glassy semiconductor materials have electronic conductivity, exhibit photoconductivity and thermopower. When cooled slowly, they usually turn into crystalline semiconductor materials. Another important class of non-crystalline semiconductor materials are solid melts of a number of amorphous semiconductors with hydrogen, the so-called. hydrogenated non-crystalline semiconductor materials: a-Si:H, a-Si1-xCx:H, a-Si1-xGex:H, a-Si1-xNx:H, a-Si1-xSnx:H. Hydrogen is highly soluble in these semiconductor materials and makes a significant number of dangling bonds characteristic of amorphous semiconductors. As a result, the density of energy states in the band gap sharply decreases and the possibility of creating p-n junctions becomes possible. Semiconductor materials also include ferrites, ferroelectrics and piezoelectrics.
Application. The most important area of application of semiconductor materials is microelectronics, power semiconductor devices(valves, thyristors, transistors), solar energy (solar batteries), lasers and LEDs, optical radiation receivers (photodetectors), microwave devices, nuclear radiation detectors, thermal refrigerators, strain gauges, highly sensitive thermometers, magnetic field sensors, etc.
2.2 Biomaterials
Biomaterials are used to create implants for the human body, which are designed to replace diseased or destroyed organs or tissues. For example, a fracture or injury to a bone leads to the need to replace the damaged area with an artificial implant. If the hearing is impaired, the patient needs a hearing aid. Plastic surgery, when people want to somehow change their facial features, also resorts to the help of biomaterials (breast/dental implants, contact lenses, prostheses, bone plates, etc.).
Biomaterials can be divided into two groups: transplants And implants. A special place is occupied by biomaterials constructed from cells or being their carriers. The first group is organs and tissues transplanted from the patient himself or his close relatives (for example, a kidney, a piece of bone, skin). In this case, the problem of material compatibility either does not arise, or, on the contrary, the organ is rejected, but if the outcome is successful, it fully ensures the necessary functioning. However, the impossibility of predicting the outcome of a transplant, as well as the more than limited number of transplants, imposes its own limitations on this type of biomaterial.
The second group represents "non-living" materials, not directly related to the body: polymers, ceramic blocks, coral skeletons and the like. In the case of implants, the problem of genetic incompatibility of the material does not arise; here the question arises about its fundamental toxicity or biocompatibility. Implants can be produced in any quantity to meet the required demand, which is their undoubted advantage, but they are not able to completely restore the functions of the replaced organ.
Completely new horizons are opening up using the latest advances in genetic engineering and cell culture operations. It seems possible to “populate” the implanted biomaterial with cells (for example, when replacing bone, which is a rather porous material) so that the material gradually dissolves in the body’s environment, and the cells build natural biological bone tissue on its basis - biomineralization occurs. A special role is given to stem cells, which can potentially restore any damaged tissue. In this case, the organization of the material at the nanolevel is also extremely important, allowing the material, on the one hand, to be quite “friendly” to the stem cell, and on the other hand, to quickly dissolve in the body.
Work is being carried out in the field of creating tissues grown in a nutrient medium based on human cells in need of help. Such tissues not only do not cause complications when they replace damaged areas (after all, they are identical to the tissues of a particular patient), but also replicate lost or damaged organs in all their properties.
It is the success in the field of creating biomaterials that opens the way to increasing human life expectancy, and nanotechnologies and, especially, the recently developing bionanotechnologies occupy not the last place here.
2 . 3 Materials of the future
“Smart” (or intelligent) materials are a group of new artificially developed substances that have a significant impact on many modern technologies. The definition of "smart" means that these materials are able to sense changes in the environment and respond to these changes in a predetermined way - a quality inherent in living organisms. The concept of smart materials has also been extended to complex systems built from both smart and traditional substances.
Some types of sensors (recognizing incoming signals), as well as executive systems (activators) playing the role of responding and adaptive devices can be used as components of smart materials (or systems). The latter can be used to change shape, position, natural frequencies or mechanical characteristics as a response to changes in temperature, light intensity, electric or magnetic field strength.
Four types of materials are usually used as activators: shape memory alloys, piezoelectric ceramics, magnetostrictive materials and electrorheological electromagnetic fluids.
Alloys with memory- these are metals that, after deformation, return to their original shape if the temperature changes.
Piezoelectric ceramics expand and contract in response to changes in the electric field (or voltage); if their sizes change, this leads to the excitation of an electrical signal. The behavior of magnetostrictive materials is similar to the reaction of piezoelectrics, but only as a response to a change in the magnetic field. In the case of electro- and magnetorheological fluids, these are media that undergo enormous changes in viscosity in response to changes in the electric or magnetic field, respectively.
Materials/devices, used as sensors, can be optical fibers, piezoelectrics (including some polymers) and microelectromechanical devices, abbreviated MEMS.
An example of a smart device is a system used in helicopters to reduce cabin noise generated by rotating blades. Piezoelectric sensors built into the blades monitor stress and strain; the signal is transmitted from these sensors to actuator, which, using a computer, generates “anti-noise” that dampens the sound from the operation of helicopter rotors.
2 . 4 Nanotechnological materials
Until very recently, the generally accepted procedure for work in the chemistry and physics of materials was to first study very large and complex structures, and then move on to analyze the smaller fundamental blocks that make up these structures. This approach was sometimes called "top-down". However, with the development of scanning microscopy technology, which made it possible to observe individual atoms and molecules, it became possible to manipulate atoms and molecules in order to create new structures, and thereby obtain new materials that are built on the basis of atomic-scale elements (the so-called “materials design”) "). These abilities to carefully assemble atoms have opened up the prospect of creating materials with mechanical, electrical, magnetic and other properties that would be unattainable using other methods. We will call this approach “bottom-up”, and the study of the properties of such new materials is carried out by nanotechnology, where the prefix “nano” means that the dimensions of the structural elements are on the order of a nanometer (i.e. 10-9 m). As a rule, we are talking about structural elements with sizes less than 100 nm, which is equivalent to approximately 500 atomic diameters.
One example of this type of material is carbon nanotubes. In the future, we will undoubtedly be able to find more and more areas in which the advantages of nanotechnological materials will manifest themselves.
Conclusion
Although enormous progress has been made in the field of materials science and application technology over the past few years, the need to create even more advanced and specialized materials, as well as to evaluate the relationships between the production of such materials and its impact on the environment, still remains. . It is necessary to make some comments on this issue in order to outline possible prospects in this area.
There is a recognized need for new economically viable energy sources, as well as for more efficient use of existing sources (the ability to directly convert solar energy into electrical current). Currently solar panels They are quite complex and expensive devices. There is no doubt that new, relatively cheap technological materials must be created that are more efficient in using solar energy.
Another very attractive example in energy conversion technology is hydrogen fuel cells, no pollutiontionsenvironment. Currently, the use of this technology in electronic devices is just beginning; In the future, such elements can be used as power plants in cars. New materials are needed to create more efficient fuel cells, and new catalysts are needed to produce hydrogen.
To maintain environmental quality at the required level, we need to implement control of air and water composition. Various materials are used to control pollution. In addition, it is necessary to improve methods of processing and purification of materials in order to reduce environmental pollution, i.e. The goal is to create less waste and harm the environment around us less. It should also be taken into account that the production of some materials produces toxic substances, so the possible environmental damage from the discharge of such waste should be taken into account.
Many of the materials we use come from irreplaceable resources those. sources that cannot be regenerated (oil, metals). Resources are gradually being exhausted, hence the need arises: 1) discovering new sources of resources; 2) creation of new materials with similar properties that cause less damage to the environment; 3) development of new technologies that allow recycling.
As a consequence of all this, there is a need for an economic assessment not only of production, but also of environmental factors, so that it becomes necessary to analyze the entire life cycle of the material - “from cradle to grave” - and the production process as a whole.
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Construction materials
By purpose:
By type of material:
By method of obtaining: natural and artificial.
Natural
Artificial
Raw materials used, advantages of waste-free technology in the production of building materials.
The theory of waste-free technological processes within the framework of the basic laws of environmental management is based on two premises:
Initial natural resources must be extracted once for all possible products, and not every time for individual ones;
The created products, after being used for their intended purpose, should be relatively easily converted into the starting elements of a new production.
The scheme of such a process is “demand - finished product - raw materials”. But each stage of this scheme requires energy consumption, the production of which is associated with the consumption of natural resources outside the closed system
The concept of waste-free technology is relative. It is understood as a theoretical limit or to the full extent, but only partially (hence – low-waste technology – ILO). But with the development of modern high-tech technologies, BOT should be implemented increasingly closer to the ideal model.
Generally integrated approach to assess the degree of waste-free production should be based on:
Taking into account not so much wastelessness as the degree of use of natural resources;
Estimation of production based on the most common material balance, i.e., on the ratio of the yield of final products to the mass of incoming raw materials and semi-finished products;
Determining the degree of non-waste by the amount of waste generated per unit of production.
For example, in non-ferrous metallurgy, the degree of non-waste is judged by the coefficient of comprehensiveness of the use of raw materials (in many cases it exceeds 80%). In the coal mining industry, an enterprise is considered waste-free (low-waste) if this coefficient does not exceed 75%.
Properties, quality assessment and durability of building materials.
All properties building materials can be divided into physical, chemical, mechanical And technological.
Physical properties in turn divided into general physical, characterizing the structure of the material, hydrophysical, thermophysical and acoustic. General physical properties include: true density, average density and porosity of the material. Hydrophysical properties - hygroscopicity, water absorption, water resistance, water resistance, vapor permeability, frost resistance, air resistance. The main thermophysical properties are thermal conductivity, heat capacity, heat resistance, heat resistance, fire resistance, fire resistance. Acoustic properties: sound-absorbing, sound-insulating, vibration-insulating and vibration-absorbing. Chemical properties characterize the ability of a material to react chemically with other substances - chemical activity, solubility, ability to crystallize and adhesion. Mechanical properties characterize the behavior of materials under the action of loads of various types. Technological properties characterize the ability of a material to be subjected to one or another type of processing.
Quality assessment methods:- by changes in properties, - by deviation of structural parameters from optimal
Under quality building materials are understood as a set of properties that determine their suitability for their intended use. Quality is formed at all stages of material production and is determined by many factors: properties of raw materials and semi-finished products, features of the technological process and equipment, qualifications of workers, level of production organization.
Durability- a complex property, quantitatively expressed by the duration of the effective resistance of the material to the entire complex of influences during the operational period of operation to the corresponding critical level.
The entire period of durability can be divided into three time stages. The first stage of operation is characterized by strengthening the structure or improving properties; the second is their relative stability; the third - destruction, i.e. slow or rapid disruption of the structure up to its critical state or even complete destruction.
Hydrophysical properties of building materials.
Hydrophysical properties develop materials and products upon contact with water. The most important of them are hygroscopicity, water absorption, water resistance, water resistance, vapor permeability, frost resistance, air resistance.
Hygroscopicity– the property of a material to absorb water vapor from the air and retain it on its surface. The smaller the pores, the greater the total surface area (assuming equal total porosity and the same material composition), therefore, the hygroscopicity is higher.
Water absorption– the ability of a material to absorb and retain water.
Moisture release– the ability of a material to release moisture when air humidity decreases.
Water permeability– the property of a material to allow water to pass under pressure.
Frost resistance– the ability of a material to maintain its strength during repeated alternate freezing in a water-saturated state and thawing in water.
Air resistance– the ability of the material to withstand repeated moistening and drying for a long time without deformation or loss of mechanical strength.
Structure, chemical composition wood
Wood structure
Wood consists of cells, which are basically hollow tubes of different sections. The structure of wood is studied in three main sections - transverse, radial and tangential.
Core located in the central part of the trunk, in the form of a round or bright star-shaped spot. The core wood is loose and rots easily, so the presence of the core is considered a defect in the material. Behind the core is located wood- the most valuable part of the trunk. Edges wood bark consisting of two parts: external and internal. Outer crust- this is a layer of dead tissue that protects wood from mechanical damage and changes in ambient temperature. Inner bark - bast- is a narrow layer through which a downward flow of organic substances occurs from the crown to the roots.
All tree species are usually divided into sound and sapwood. Core rocks in the center of the trunk have a brightly colored part - the core. The peripheral light part of the trunk around the core is called sapwood. Along the sapwood there is an upward flow of water and solutions of mineral salts from the roots to the crown.
As a result of the annual increase in trunk diameter, annual layers, which consist of two zones: early and late.
Vessels meet only for deciduous trees. Depending on their location along the annual layer, they are divided into ring-vascular and diffuse-vascular. Resin passages found only in coniferous species. They are intercellular channels filled with resin.
Chemical composition of wood
Wood consists predominantly of organic substances (99% of the total mass). The main chemical elements are carbon (about 50%), hydrogen (about 6%), oxygen (about 44%) and nitrogen (up to 0.25%). The elemental chemical composition of wood of different species is almost the same. The main components of wood are cellulose (between 42 and 51%), hemicellulose (between 24 and 40%), lignin (18 to 30%). Wood also contains impurities, so-called extractives, such as resin, turpentine, fat, wax and dyes (from 1 to 10%), and ash, that is, non-combustible components, such as potassium, sodium, magnesium, phosphorus and iron oxide (0.2 to 0.8%). Listed chemical elements form the main organic substances: cellulose, lignin and hemicelluloses.
11 Basic properties of wood.
Color Wood is determined by the tanning, resinous and coloring substances found in the cavities of the cells. It can be white, red, orange, pink, yellow, purple, brown, black, gray with many shades depending on the species, age of the tree, place and conditions of its growth, and storage conditions of the wood.
Texture- natural pattern on the wood cut. It depends on the type of wood and the direction of the cut: end-cut produces concentric circles, radial - longitudinal stripes, tangential - winding lines. Texture affects the decorative qualities of the material.
Density wood, that is, the ratio of its mass to volume, depends on the species, humidity (directly proportional), and growing conditions of the tree. Even in different sections of the same trunk, it may not coincide. Rocks are conventionally divided into three groups: low density (up to 540 kg/cubic m), medium density (550-740 kg/cubic m), high density (750 kg/cubic m and above)
Humidity(absolute) wood is the ratio of the mass of water located in a given volume to the mass of absolutely dry wood, expressed as a percentage. There are wet (humidity over 100%), freshly cut (50-100%), air-dry (15-20%, depending on climatic conditions and time of year), chamber drying (8-12%) and absolutely dry (O% ) wood.
Hardness- this is the ability of wood to resist the penetration of harder bodies into it. It depends on the density of the wood and is not the same in different directions.
Durability call the ability of a material to resist destruction, as well as irreversible changes in shape under the influence of external loads. There are strength limits (moments of failure of the sample) in compression, tension, bending, torsion, and shear. Their values largely depend on the direction of the fibers in the part under load.
Cleavability- this is the ability of wood to separate (split) along the grain under the action of a wedge and load.
Defects and vices of wood
These are any violations of the integrity of the solid wood tissue, deterioration of its physical and mechanical properties, changes in appearance. Any blemish or defect limits the use of a particular wood to a greater or lesser extent. To put the question briefly, then any vice is a deviation from the norm. The reasons for the occurrence of defects lie in the evolution of the development and growth of the tree, the adverse effects of climatic conditions, and natural aging. The causes of defects are external mechanical influences. We list some characteristic defects and defects: Growths. This is nothing more than a local thickening of the tree trunk. Growths can be of two types - nodules and burls. Surges represent consequences internal diseases tree. Most often they occur on the lower (butt) part of the tree. Burls look like tubercles on the trunk. These are germinating buds that seem to have awakened from hibernation. Both burls and burls appear most often on deciduous trees - oak, maple, alder, birch. 3comely. Any increase (thickening) in the diameter of the lower part of the trunk (butt) falls under this definition. Hardness deteriorates the quality of lumber made from this section, because the wood contained a large number of cut fibers. Knotiness. This is the presence of a large number of knots on the trunk. In itself, this is an inevitable defect of wood in general, but the whole point is in their quantity on a specific given section of the tree. Knotiness worsens how appearance wood, as well as its consumer qualities, because makes processing very difficult due to the fact that the knots have increased hardness compared to the tree itself. Curlyness is a complexly intertwined arrangement of tree trunk fibers. The presence of twist has both positive and negative consequences for the use of wood from this part of the tree. The positive point is that the grain increases the strength characteristics of the wood and at the same time improves the texture pattern. Negative point - difficulty in processing Germination. This defect is a consequence of damage to the wood fiber. Resin forms around the sprout and rotting of the affected area begins. Germination can be either open or closed. The wood from such areas is not suitable for making lumber at all.
15Purpose of building materials based on wood and plant raw materials: structural and finishing, thermal insulation and acoustic, moldings and carpentry.
Lumber obtained by longitudinal cutting of logs. Materials with sawn edges are called edged, while materials with unsawed edges are called unedged. Fibrolite- a slab material obtained by hardening an inorganic binder with a filler of wood shavings. Arbolit- made from cement and sawdust. Plywood and plywood boards, which have good strength properties, are traditionally used in the construction and furniture industry as a structural material. Decorative: Lining– decorative facing board, which is made from solid wood. Eurolining, unlike ordinary lining, is made from higher quality wood. Wood for eurolining, after sawing, is tested for the presence of fungi, knots, worms and resin. Block house– a type of decorative finishing board (lining) that imitates timber or logs Natural wood wallpaper- veneer rolls from valuable wood species. Decorative wood panels– wooden wall panels are usually made from solid wood, such as oak, cedar, maple, alder.
Thermal insulation:
Wood fiber thermal insulation products(GOST 4598) are made in the form of large-sized slabs or sheets from wood raw materials, which are successively crushed into a fibrous mass, shaped and subjected to heat treatment. Wood boards have increased hygroscopicity and water absorption. They are flammable and can smolder for a long time.
Wood-based thermal insulation boards made by hot pressing of a mass containing about 90% organic fibrous raw materials (most often specially prepared wood chips) and 8-10% synthetic resins (phenol-formaldehyde or urea-formaldehyde). To improve the properties of the boards, water-repellent substances, antiseptics and fire retardants are added to the raw material. The slabs are single- and multi-layer, solid and multi-hollow. The strength of particle boards is much higher than similar fibreboards.
Cobblestone
Paving stone. Side stones from rocks. Gravel. Sand
TO stone materials and products for foundations and walls include rubble stone, rock wall stones, and large wall blocks.
Rubble stone is a piece stone measuring 150-500 mm and weighing 20-40 kg. Based on their shape, they are divided into torn, bedded and flagstone.
Ragged Stone It consists of irregularly shaped pieces with a bumpy surface. Postleaf has at least one non-lumpy edge, flagstone has two parallel edges. Rubble stone is obtained from igneous, sedimentary and metamorphic rocks. Used for constructing rubble and rubble concrete foundations, underground walls, and walls of unheated buildings.
Rock wall stones- material in the form of a rectangular parallelepiped with dimensions of 390x190x188, 490x240x188 and 390x190x288 mm. They are made from rocks with medium density up to 2200 kg/m 3 mainly from limestone and tuff. Used for laying walls, partitions and other parts of buildings and structures.
Large wall blocks made by sawing from rocks with an average density of up to 2200 kg/m 3. These are volcanic tuffs, limestone, dolomites. They are used for laying external walls.
For facing materials and products made of natural stone include sawn facing slabs, architectural and construction products, and decorative slabs.
WALL MATERIALS
The main ones in this group are: ordinary clay brick and the so-called effective brick - hollow and porous clay brick of plastic molding, semi-dry pressed hollow clay brick and lightweight construction brick. Hollow ceramic stones of plastic molding are also used as wall material.
FACING PRODUCTS
Ceramic products used for cladding buildings are divided into two groups - for cladding building facades and for interior cladding of premises.
Currently, the main types of ceramic facing materials for building facades are facing bricks, stones, slabs and tiles. Bricks and stones are made solid and hollow. Depending on the design, manufacturing methods and fastening, slabs are divided into embedded slabs, installed simultaneously with the laying of walls, and leaning slabs, installed on mortar after the walls have been erected and settled. Facade slabs are made in various shapes: flat - for cladding the plane of walls, corner slabs - for cladding external corners, slopes and openings, and lintels - for cladding lintels over window and door openings. Small-sized facade tiles are produced with an outer smooth and textured surface, and on the back side there are recesses for better adhesion to cement mortar. To speed up finishing work, thin facade tiles are glued onto a paper base in the form of carpets with different patterns. Such tiles are called carpet ceramics.
Ceramic materials for interior cladding are not exposed to negative temperatures and sudden changes in weather, so they do not have to meet all the requirements for materials for the external cladding of buildings. However, dimensional accuracy, correct shape and uniform coloring become particularly important. Ceramic floor tiles are used to lay floors in the lobbies of public buildings, baths, laundries, sanitary facilities, medical rooms and chemical industry enterprises. These tiles are practically waterproof, i.e. they reliably protect load-bearing structures ceilings from moisture, firmly resist abrasive influences, do not produce dust, are easy to clean, do not absorb liquids and are well resistant to acids and alkalis.
OTHER CERAMIC PRODUCTS
Here it should be said about clay tiles, which are a sintered product in the form of rectangular tiles or gutters and are widely (especially in the south and west of the country) used as roofing material. Four types of tiles are produced: stamped groove and strip, flat strip and ridge. Diatomaceous earth (Trepel), foam Trepel products and expanded clay gravel are known as thermal insulation materials. Of the special ceramic products that are used in the construction and equipment of chemical and other plants, fire-resistant and acid-resistant products are used. It should also be mentioned various types special brick - high-strength road brick, obtained by firing clay until completely sintered, but without vitrifying the surface; patterning, fireproof, lining, acid-resistant, etc.
Additives to clays
To impart different properties to both clays and the ceramic products obtained from them, various additives are introduced into the clay. Let's briefly look at the additives that are most often used.
Leaning Supplements
In highly plastic clays, which require a large amount of water for mixing (up to 28%) and therefore give a large linear shrinkage during drying and firing (up to 15%), it is necessary to introduce leaning additives, i.e., non-plastic substances. At the same time, the amount of water required to mix the clay dough is significantly reduced, which reduces the amount of shrinkage (up to 2-6%).
VB as depleting additives, substances of inorganic origin are most often used - quartz sand, fireclay (burnt and crushed clay) and waste products, ground slag and ash. These additives not only reduce product shrinkage, but also improve the molding properties of the mass, facilitate the production process and eliminate defects. In some cases, they improve the physical properties of products, such as heat resistance and thermal conductivity.
Burn-out additives
To obtain products with lower volumetric weight and increased porosity, organic burn-out additives are used. The most commonly used are sawdust, coal fines and coal powder, peat dust, etc. Substances that release carbon dioxide at high firing temperatures are also used, which leads to the formation of pores - chalk, dolomite and clay marl (in ground form). All of these supplements also have the properties of leaning supplements.
Special Additives
To impart special properties to ceramic products, appropriate additives can be used. For example, in the manufacture of acid-resistant products and facing tiles, additives to clays are sand mixtures sealed with liquid glass or alkalis. If it is necessary to lower the firing temperature of some products, fluxes (fluxes) are introduced into the clay - ground feldspar, ores containing iron, sandstone, etc. As additives that increase the plasticity of the molding mass, they are used in small doses (0.1-0.3% ) surface-active substances, for example sulfite-alcohol stillage. To improve the quality of bricks, sodium pyrophosphates and sodium polyphosphates are used as additives.
Oxides of certain metals added to the mass of white-burning clays to color it a certain color can also be considered as special additives.
Classification of building materials by purpose, type of material, method of production.
Construction materials and products are classified according to purpose, type of material and method of production:
By purpose: structural, finishing, waterproofing, thermal insulation, acoustic, anti-corrosion, sealing;
By type of material: natural stone, forest, polymer, metal, ceramic, glass, artificial stone, etc.;
By method of obtaining: natural and artificial.
Natural building materials are mined from places where they are naturally formed (rocks), usually in the upper layers of the earth's crust, or grown (wood). They are used in construction, using mainly mechanical processing (crushing, sawing). The composition and properties of these materials mainly depend on the origin of the source rocks and the method of their processing and processing.
Artificial building materials are made from natural mineral and organic raw materials (clay, sand, limestone, oil, gas, etc.), industrial waste (slag, ash) using special proven technology. The resulting artificial materials acquire new properties that differ from the properties of the original raw materials.
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Home > Coursework >Construction
Ministry of Education and Science of the Republic of Kazakhstan
East Kazakhstan State Technical University named after. D. Serikbaeva
Department of Theory of Architecture and Engineering Graphics
Coursework
in the discipline "Engineering Graphics"
Topic: Natural and building materials
Completed by: student of group 09-BZ-1
Abraimova A.S.
Accepted by: Associate Professor Tsymbal N.T.
Ust-Kamenogorsk
INTRODUCTION
2.TYPES OF NATURAL BUILDING MATERIALS
1.1 Natural stone building materials: basalt, granite
1.2Non-metallic natural building materials: crushed stone, sand
INTRODUCTION
Natural building materials, obtained as a result of relatively simple mechanical processing of monolithic rocks while preserving their physical, mechanical and technological properties, are used in the form of slabs, blocks, side and facing stones, road paving stones, rubble stone, crushed stone, crushed sand, etc. Natural loose rocks are also used in huge quantities: boulders, gravel, sand, clay, etc. In addition, rocks are the most important raw materials for the production of artificial building materials (building ceramics, refractories, glass, cement, lime, etc.). Why are they subjected to complex types of mechanical and chemical processing?
The widespread use of natural raw materials is associated with the presence of favorable physical and chemical properties of numerous rocks. Already in the early period of his existence, man discovered on the surface of the earth and in its depths a variety of natural materials that fully satisfied his relatively limited needs. At subsequent stages of the development of human society, increased requirements for the quality of building stone appear and at the same time, methods of processing and processing natural raw materials to obtain materials of a different quality and properties, for example, turning ordinary clay into stone when firing it and obtaining stable properties of the finished product.
Rocks are simple and complex natural mineral aggregates that occupy large areas of the earth's crust and are distinguished by greater or lesser constancy of the chemical and mineral composition, structure, as well as certain conditions of occurrence. They make up the surface layers of the earth's crust with a thickness of about 15...60 km and form natural accumulations of valuable mineral raw materials.
1 NATURAL BUILDING MATERIALS: CONCEPTS AND ROLE IN SOCIAL PRODUCTION
1.1 Definition of “natural building materials”
During the construction, operation and repair of buildings and structures, building products and structures from which they are erected are subject to various physical, mechanical, physical and technological influences.
Construction materials and products used in the construction, reconstruction and repair of various buildings and structures are divided into
natural
artificial
which in turn are divided into two main categories:
The main types of building materials and products are stone natural building materials and products made from them, binding materials, inorganic and organic forest materials and products from them, metal products. Depending on the purpose, conditions of construction and operation of buildings and structures, appropriate building materials are selected that have certain qualities and protective properties from exposure to various external environments. Taking these features into account, any building material must have certain construction and technical properties. For example, the material for the external walls of buildings must have the lowest thermal conductivity with sufficient strength to protect the room from the external cold; material for drainage and drainage structures - waterproof and resistant to alternating wetting and drying; The road surface material (asphalt, concrete) must have sufficient strength and low abrasion to withstand the loads from transport.
When classifying materials and products, it is necessary to remember that they must have good properties and qualities.
1.2Properties and qualities of natural building materials
Property is a characteristic of a material that manifests itself during its processing, application or operation.
Quality is a set of properties of a material that determine its ability to satisfy certain requirements in accordance with its purpose.
The properties of building materials and products are classified into four main groups:
physical,
mechanical,
chemical,
technological, etc.
Chemical materials include the ability of materials to resist the action of a chemically aggressive environment, causing exchange reactions in them leading to the destruction of materials, a change in their original properties: solubility, corrosion resistance, resistance to rotting, hardening.
Physical properties: average, bulk, true and relative density; porosity, humidity, moisture transfer, thermal conductivity.
Mechanical properties: compressive strength, tensile strength, bending strength, shear strength, elasticity, plasticity, rigidity, hardness.
Technological properties: workability, heat resistance, melting, speed of hardening and drying.
Physical properties of building materials.
True density ρ is the mass of a unit volume of material in an absolutely dense state. ρ =m/Va, where Va is the volume in a dense state. [ρ] = g/cm³; kg/m³; t/m³. For example, granite, glass and other silicates are almost completely dense materials. Determination of true density: a pre-dried sample is crushed into powder, the volume is determined in a pycnometer (it is equal to the volume of the displaced liquid).
Average density ρm=m/Ve is the mass of a unit volume in its natural state. The average density depends on temperature and humidity: ρm=ρв/(1+W), where W is relative humidity, and ρв is the wet density.
Bulk density (for bulk materials) - the mass per unit volume of loosely poured granular or fibrous materials.
Porosity P is the degree of filling of the material volume with pores. P=Vp/Ve, where Vp is the pore volume, Ve is the volume of material. Porosity can be open or closed.
Open porosity Pores communicate with the environment and with each other, and are filled with water under normal saturation conditions (immersion in a bath of water). Open pores increase the permeability and water absorption of the material and reduce frost resistance.
Closed porosity Pz=P-Po. Increasing closed porosity increases the durability of the material and reduces sound absorption.
Porous material contains both open and closed pores
Hydrophysical properties of building materials. Water absorption of porous materials is determined using a standard method by keeping samples in water at a temperature of 20±2 °C. In this case, water does not penetrate into closed pores, that is, water absorption characterizes only open porosity. When removing samples from the bath, water partially flows out of large pores, so water absorption is always less than porosity. Water absorption by volume Wo(%) - the degree of filling the volume of the material with water: Wo=(mв-mc)/Ve*100, where mв is the mass of the material sample saturated with water; mc is the dry mass of the sample. Water absorption by mass Wm(%) is determined in relation to the mass of dry material Wm=(mw-mc)/mc*100. Wo=Wм*γ, γ is the volumetric mass of dry material, expressed in relation to the density of water (dimensionless value). Water absorption is used to evaluate the structure of the material using the saturation coefficient: kн = Wo/P. It can vary from 0 (all pores in the material are closed) to 1 (all pores are open). A decrease in kn indicates an increase in frost resistance.
Water permeability is the property of a material to allow water to pass under pressure. The filtration coefficient kf (m/h is the speed dimension) characterizes water permeability: kf = Vv*a/, where kf = Vv is the amount of water, m³, passing through a wall of area S = 1 m², thickness a = 1 m during time t = 1 hour with a difference in hydrostatic pressure at the wall boundaries p1 - p2 = 1 m of water. Art.
The water resistance of the material is characterized by grade W2; W4; W8; W10; W12, denoting one-sided hydrostatic pressure in kgf/cm², at which a concrete cylinder sample does not allow water to pass through under standard test conditions. The lower the kf, the higher the waterproof grade.
Water resistance is characterized by the softening coefficient kp = Rв/Rс, where Rв is the strength of the material saturated with water, and Rс is the strength of the dry material. kp varies from 0 (wetting clays) to 1 (metals). If kp is less than 0.8, then such material is not used in building structures located in water.
Hygroscopicity is the property of a capillary-porous material to absorb water vapor from the air. The process of absorbing moisture from the air is called sorption, it is caused by polymolecular adsorption of water vapor on the inner surface of the pores and capillary condensation. With an increase in water vapor pressure (that is, an increase in the relative humidity of the air at a constant temperature), the sorption moisture content of the material increases.
Capillary suction is characterized by the height of water rising in the material, the amount of absorbed water and the intensity of suction. A decrease in these indicators reflects an improvement in the structure of the material and an increase in its frost resistance.
Humidity deformations. Porous materials change their volume and size when humidity changes. Shrinkage is a reduction in the size of a material as it dries. Swelling occurs when the material is saturated with water. Thermophysical properties of the structure of materials.
Thermal conductivity is the property of a material to transfer heat from one surface to another. Nekrasov’s formula connects thermal conductivity λ [W/(m*C)] with the volumetric mass of the material, expressed in relation to water: λ=1.16√(0.0196 + 0.22γ2)-0.16. As temperature increases, the thermal conductivity of most materials increases. R - thermal resistance, R = 1/λ.
Heat capacity c [kcal/(kg*C)] is the amount of heat that must be imparted to 1 kg of material in order to increase its temperature by 1C. For stone materials, the heat capacity varies from 0.75 to 0.92 kJ/(kg*C). As humidity increases, the heat capacity of materials increases.
Fire resistance is the ability of a material to withstand prolonged exposure to high temperatures (from 1580 °C and above) without softening or deforming. Refractory materials are used for the internal lining of industrial furnaces. Refractory materials soften at temperatures above 1350 °C.
Fire resistance is the property of a material to resist the action of fire during a fire for a certain time. It depends on the combustibility of the material, that is, on its ability to ignite and burn. Fireproof materials - concrete, brick, steel, etc. But at temperatures above 600 °C, some fireproof materials crack (granite) or become severely deformed (metals). Refractory materials smolder under the influence of fire or high temperature, but after the fire ceases, their combustion and smoldering stops (asphalt concrete, wood impregnated with fire retardants, fiberboard, some foam plastics). Combustible materials burn with an open flame, they must be protected from fire by structural and other measures, and treated with fire retardants.
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