Classification of construction materials by design. Description of the main properties of building materials

Interrelation of architecture and building materials (examples).

Building materials determine the feasibility of creative design

the reality of new architectural forms and constructive systems

stipulate the economic and functional feasibility of the construction

actively influence the development of modern architecture

stipulate the character and aesthetic expressiveness of the form

At present, buildings and structures can be built from many interchangeable materials, while the living conditions from the operational and technical point of view will be the same, but the perception of the environment, the aesthetics of buildings and structures will be quite different. Here the architect must clearly understand what materials correspond to a certain creative idea.

until the 20th century, materials were used that could withstand heavy loads during compression, but much less when bending and stretching. Such material was, for example, a stone whose properties allowed to cover only small spaces. Monumentality, greatness (ancient tombs, temples). Subsequently, architectural forms made of natural stone became quite light, and the construction that overcame the properties of the stone became extremely difficult and long (the Gothic period).

In the XX century - the wide introduction of materials with high strength properties in bending and stretching. For example, metal cables, the main load-bearing elements in cable-stayed structures, allow to cover huge areas of spaces of various shapes.

The use of metal and reinforced concrete for modern frame structures allows you to obtain virtually any given shape of structures of various sizes, which was not achievable before. Impossible was the creation of stand-alone poles: the materials did not allow rigidly to connect the support to the base. But now, metal or reinforced concrete allows to build high-altitude pillars of separately standing tower structures that are not feasible with the help of wood or stone because of their properties. (Eiffel Tower)

Standardization of building materials (definition, methods of standardization).

Standardization   called the process of establishing and applying standards - a set of regulatory and technical requirements, norms and rules for products of mass application, approved as mandatory for enterprises and manufacturers and consumers of these products.

GOST - state. stdardy - demanding the properties of materials, methods of their testing., acceptance rules, protractor and stored. Technical test (TU) or time (VTU). SNiP - builds norms and rules. But from July 1, 2003 the standards of quality will be offered by enterprises themselves, and the state will ensure only the safety of products for consumption.

Standardization methods include unification and typing of materials.

Unification   - is the reduction of various types of materials to a technically and economically rational minimum of standard sizes, brands, shapes, properties, etc. In this case, as a rule, technical requirements for several materials of the same functional purpose are combined so that it is possible to replace one material with another without deteriorating the quality of the building object.

Typinginvolves the development of typical materials or structures based on common technical characteristics. The requirements for typing are very relevant; they determine the release of materials, the dimensions of which are associated with the module - the conventional unit of measurement. The module is used to coordinate the dimensions of not only materials, but also parts of buildings. A single modular system in Russia is created on the basis of the main module 100 mm. A number of arbitrary enlarged (3M, 6M, 12M, 15M, 30M, 60M) and fractional (1 / 2D, 1 / 5M, 1 / 10M, 1 / 20M, 1 / 50M, 1 / 100M) modules. The enlarged and fractional modules (1 / 2M, 1 / 5M) determine, basically, the sizes of elements and materials for load-bearing and enclosing structures, and smaller fractional modules - the thickness of plate and sheet materials.

Unification and typification allow the architect to create various and original designs of individual buildings and entire ensembles in conditions of mass industrial construction.

Classification of building materials (schemes, examples).

On purpose, the materials are divided into: structural, structural and finishing and finishing.

Structural materials provide protection against various physical influences (climatic factors, noise, etc.), strength and durability of buildings and structures. These materials are hidden in the "body" of the structure, for example, ceramic ordinary brick, heat-insulating material.

Structural and finishing materials also provide certain protection, strength, and their one or more surfaces, which are called facial, are perceived visually during operation. For example, ceramic brick front, linoleum.

Finishing materials affect the perception of the environment of human life. They perform both protection functions (wallpaper, although a little, but protect the materials in the design), but their main function is visual perception (one or several facial surfaces) and a direct impact on the aesthetic appearance of the facade, the interior of the building, the structure. Such materials include ceramic tile for the facade or internal cladding of walls and floor, wallpaper   and etc.

Operational and technical properties of building materials (definition, schematic diagrams and units of measure, comparative indicators for different materials).

Properties - the characteristics manifested in the process of application and operation of materials, with the exception of their economic indicators, can be divided into two groups: operational and technical and aesthetic. The first provide the necessary protection, strength, required durability of the building, structures. The performance and technical properties of the material are influenced by many characteristics.

Porosity   - content in the substance of pores, cells, voids (%). There are low-porosity (less than 30%), medium-porous (from 30% to 50%) and highly porous (more than 50%) materials. The nature of porosity is closed, open, communicating; pores can be small, large. Values ​​of porosity: foams - 96%, wood - 65%, lightweight - 60%, ceramic brick - 35%, heavy concrete - 10%, granite - 1%, steel - 0%.

True density,ρ (g / cm³, kg / m³) is the mass-to-volume ratio of the material in an absolutely dense state, i.e. without pores and voids ρ = m / v. Average densityρp. (g / cm³, kg / m³) is the ratio of the mass of the material to its volume in the natural state, together with the possible pores and voids. Distinguish heavy (more than 2000 kg / m³) and light materials (less than 1000 kg / m³). average density value (kg / m³): polystyrene - 50, timber - 575, light concrete - 1200, ceramic brick - 1900, Natural stone - 2500, heavy concrete - 2200 steel - 7860. The density affects the durability of the material.

Properties under the action of moisture, water, freezing-thawing:

Humidity -moisture content in the material, referred to the mass of the material in the dry state, measured in percent. High humidity is considered to be more than 20%, low - less than 5%.

Hygroscopicity -the ability of the material to absorb water vapor from the air (with its high humidity) and to retain them due to capillary condensation.

Water absorption -the ability of the material to be in contact with water soak and retain it. %, with an error of 0.1%. More than 20% is high, less than 5% is low. Wood - 150%, ceramic brick - 12%, concrete heavy - 3%, granite - 0,5%.

Water resistance -characterized by the coefficient. softening (Kp) - the ratio of the compressive strength of a material saturated with water to the compressive strength of the material in the dry state. For\u003e 0.8 material for buildings that are constantly in contact with water.

Water permeability -the ability of the material to pass water under pressure. Characterized by the amount of water that has passed for 1 hour through 1 cm2 of the area of ​​the test material at constant pressure. The time during which the sample does not pass water at a constant water pressure, or the hydrostatic pressure that sustains a sample of the material for a certain time, is measured. Glass and metals are watertight, almost water-free materials with closed small pores.

Frost resistance -the ability of a water-saturated material to withstand alternating freezing and thawing without signs of deterioration and without significant loss of mass and strength. Freezing is performed at a temperature of -15 ... -20 ° C for 4-8 hours, thawing takes place in a bath with water at a temperature of +15 ... +20 ° C for 4 hours or more. High frost resistance - more than 100 cycles, dozens of cycles - satisfactory, less than 10 cycles - low. The indications of frost resistance determine the durability of the material in the enclosing structures.

Thermal conductivity -the ability of the material to transmit through its thickness the heat flow that occurs when the temperature difference on the surfaces that limit the material. Coefficient. Thermal conductivity (λ) is the amount of heat that has passed for 1 hour through the test material 1 m thick with a temperature difference on its opposite surfaces of 1 ˚C-W / m˚C. Materials with the coefficient. less than 0.17 - heat-insulating, less than 0.05 - significant technical and economic effect. Steel 58, granite 3, concrete heavy 1,3, brick ceramic 0,75, concrete light 0,5, foams 0,04. Features of the structure affect the heat conductive, for example, wood λ along the fibers is 2 times more across.

Fire resistance -the ability of materials to maintain physical and mechanical properties when exposed to fire and high temperatures in a fire. According to the combustibility, they are divided into three groups: non-combustible, hardly combustible and combustible. Non-flammable are not ignited, do not smolder or char (natural stone, concrete, brick, metals). Diffusable char, carbonate or hardly ignite, after removal of the source of fire, combustion and decay cease (asphalt concrete, cement fiberboard). Burned burn, smolder and after removal of fire (wood, bol-in plastic). But with the prolonged action of fire, chemical decomposition of marble, limestone or deformation of steel can occur, therefore, the degree of flammability can not be judged as fire resistance.

Sound absorption -the ability of materials to absorb sound waves. Coefficient. absorption α, showing. which is determined after testing the material in the reverberation chamber. More than 0.8 - high, less than 0.2 - low (mineral wool plates - from 0.03 to 0.45, semi-rigid porous plastics 0.11 and 0.6). A good sound-absorbing material has a porous-fibrous structure with a large number of pores of a communicating branched character, a rough surface.

Corrosion resistance -the ability of materials to resist the action of corrosive substances. Types of corrosion: physical, chemical, physicochemical, electrochemical, biological. The difference between the masses of the samples before and after the action of the aggressive medium and the corresponding change in the strength and elastic characteristics are determined. CM from organic. raw materials (wood or plastic) - compare. resistant to weak (<5%) кислотам и щелочам, но менее биостойки. Корроз. стойкость СМ из не органич. сырья зависит от их состава: если в материале преобладает двуоксид кремния, сравнит. стойкий к слаб кислотам, но взаимодействует с основными оксидами; если же в материале преобладают основные оксиды, сравнит. стойкий к слаб кислотам, но разрушается при взаимодействии с кислотами.

Properties under the action of static and dynamic forces:

Strength -the ability of materials to resist destruction or irreversible change in shape under the influence of internal stresses caused by external forces or other factors. Strength limit - voltage, corresponding. Load, at which the beginning of destruction is fixed. Compression, stretching, bending, impact. High compressive strength - 100 MPa and more, satisfactory - tens of MPa, low less than 10 MPa. Steel 400 MPa, heavy concrete 40, ceramic brick 15. When bending - steel 400, heavy concrete 4, brick about 2 MPa.

Hardness -the ability of the material to resist internal stresses arising from the local introduction of another, more rigid body, MPa. Mohs hardness scale: 10 diamond, 9 corundum, 8 topaz, 7 quartz, 6 orthoclase, 5 apatite, 4 fluorspar, 3 calcite, 2 plaster, 1 talc.

Abrasion resistance -the ability of the material to decrease in volume and mass due to the destruction of the surface layer under the action of abrasive forces. Low abrasion - less than 0.5 g / cm², high - 5 g / cm², quartzite, basalt, diorite, granite, less marble are very resistant to abrasion.

Elasticity -the ability of the material to deform under the influence of the load and self-restore the original shape and size after the termination of the external environment. Elastic deformation is reversible. Modulus of elasticity E (Young's modulus).

Plasticity -the ability of the material to change its shape and dimensions under the action of external forces, without breaking. After the termination of the action, the shape is not restored, the residual deformation is plastic.

Friability -the ability of a solid material to break down under mechanical influences without any significant plastic deformation. According to x-ru def, it is frozen. from the composition and structure, the materials can be conditionally divided into plastic (# metallic materials, except cast-iron ones) and brittle (prerotal stone, concrete, window glass).

Ethical characteristics of building materials (names, definition of color, texture, texture, types of texture).

Aesthetic characteristics include shape, color, texture, pattern (natural pattern - texture).

The formmaterials, the face (or surface) of which is perceived visually during operation, directly affects the uniqueness of the facade or the interior of the building.

Color of materials -this is the visual perception that occurs as a result of the effect on the retina of the human eye of electromagnetic oscillations reflected from the face surface as a result of the action of light.

All colors are divided into two groups: achromatic (white, black, all shades of gray) and chromatic (the colors of the rainbow with all the intermediate shades). The main characteristics of color - color tonality, lightness and saturation.

Texture -visible structure of the face of the material, characterized by the degree of relief and gloss. By the degree of relief, smooth, rough (up to 0.5 cm) and relief (more than 0.5 cm) are distinguished.

Drawing -different in shape, size, location, combination, color of the line, strip, spots and other elements on the face of the material. If the mentioned elements were created by nature, the picture is called texture.

Interrelation of properties and structure of building materials (examples).

The high porosity of the building material provides it with low thermal conductivity (especially when the pore character is closed). For example, foam has a low thermal conductivity (96% of the pores). Open pores that communicate with the environment, increase water absorption, reduce frost resistance and durability of the material (wood, concrete).

Materials with a fibrous structure exhibit anisotropy, which is why the characteristics of the properties differ markedly under physical influences along and across the fibers, for example, the coefficient of thermal conductivity of the wood (λ) along the fibers is twice as large as across the fibers.

The degree of water permeability is also related to the nature of the structure. Materials particularly dense (ρрр ~ ρ) are waterproof (glass, metals).

Relatively dense materials (without pores or with low porosity), absorbing little water, frost-resistant (natural stone).

The degree of sound absorption also depends on the structure, size and nature of the porosity, as well as the thickness of the material. For a sound-absorbing material with a relatively better structure, the porous-fibrous material with a large number of communicating pores and a rough surface (mineral wool plates).

Strength of the material is determined mainly by its structure. Some natural and artificial stone materials, for example, granite and concrete, will compare. well resist compression, but much worse - stretching, bending, impact.

The hardness of the material depends more on the density, as does the abrasion. Stones are very resistant to abrasion - quartzites, granites, basalts.

Interrelation of aesthetic characteristics of the front surface of materials and perception of external and internal decoration of buildings and structures (examples).

Form of construction; aesthetic characteristics of the front surface (texture / color / pattern): the physical essence of building materials.

The impression of heaviness or lightness, plasticity, density of the architectural form is connected with the character of the front surface of the material. For example, the plinth is usually faced with a natural stone with a rough-cut texture to emphasize the tension in the lower part of the wall, the middle floors with a stone with a less high relief, and the upper floors - stones with smooth texture.

A notable role in perception is played by the man's existing ideas about such operational and technical properties as strength, durability. For example, the architectural form of the Ostankino TV tower seems to be quite strong due to information about the material used - monolithic reinforced concrete, pulled together by powerful seven-stranded steel ropes.

Perception of the architectural form is associated with texture, color, character of the drawing of the front surface. Especially important are the aesthetic characteristics of materials in the interior decoration of buildings. The choice of color, texture, surface finish of the finishing material should be related to the functional dimensions of the room, its dimensions and composition. For example, in small rooms, the size of the elements of the invoice should be limited, otherwise the room will appear even smaller, materials with large elements of texture - for large rooms. Also it is necessary to remember that a smooth, brilliant texture can distort the perception of the interior.

The main factors determining the maximum distance from which the elements of the texture of the multi-color finishing building material are discernible.

the size of these elements

distance between them

if the material with a multicolored face, then the degree of color contrast (small, medium, large) between the elements of the invoice

When choosing a texture, a set of factors is taken into account.

* The texture is more clearly perceived on a light surface;

* The relief-bumpy texture is less voluminous than when it is smooth;

* Horizontal reliefs contribute to visual preservation of the height and lengthening of the room;

Quality and integral amount of building materials (definitions, purpose of conducting qualimetric analysis).

The quality of architectural and design projects is related to the quality of the materials used. Quality is a combination of operational and technical and aesthetic characteristics. Special qualimetric analysis helps to solve the quality problem. Economic indicators are also more related to the materials used, as up to 50% of the cost of the building is the cost of materials. Qualimetry - the science of K. K = + exploitation-tech aesthetic Features ΣK = K + economic Har-ki Kvalimetrich analysis - Wed, but an objective selection See See: Over 50% of the cost of any present-day th building 70% of prefabricated buildings ost - Inclusion of operation hr.

SM from wood

Wood.   Materials that are obtained by mining and processing of wood and waste wood. When the ax appears, wooden architecture arises; practically inexhaustible raw materials.

Raw material.   Barrel - 90% of the volume of wood: bark; sapwood; core; core. Basic tree species: conifers: pine - soft, durable, easy to process (furniture); spruce - lighter, a lot of hard knots, comparatively quickly decaying; larch - dense, firm, strong, almost not angry; cedar - light, soft wood is inferior in strength to pine; deciduous:   oak - dense, strong, solid (bridges, carpentry); Ash - dense, flexible (furniture); birch - easily rotting (finishing materials, carpentry); aspen - light, soft (plywood, wood plates); linden - soft (plywood), maple - dense wood, compare a little crumpled and stagnant to rot, is well processed.

Extraction:Valka, bucking, trimming of trees.

Treatment:Bucking - transverse division of the whips. Separate business and wood parts, Sawing - group or individual cutting logs; type sawing determines the character texture: obtaining radial, tangential board; chipping, peeling - removal special knives thin sections of wood with this peeling - cutting spirally; milling - cutting special knives and obtaining the desired profile of woody materials assembly semi - bonding (boards) waste (nail, glue), waste treatment - sorting, mixing with binders and forming (under pressure). Waste:soft (sawdust, shavings, fibers), lumpy (pieces of branches, bark, branches). Drying   - increases the strength of wood, extends the service life: artificial (dryers), natural (in stock).   Protective treatment: antiseptics - substances that are toxic to fungi (copper sulfate, fluoride and silica sodium); antipirirovanie - fire retardants. Surface, volume (deep) processing.

Finish   (formation of esthetic characteristics): transparent - preservation, revealing of natural structure, opaque - color and texture are hidden (needles).   Imitation finish:   mosaic, incrustation - cutting into the wood of other materials (ivory, metal), intarsia - wood in wood, marquetry - mosaic set of pieces of veneer of different species. Wood carving:in-depth; flat-relief, relief.

Kinds:round timber   (pieces of wood trunks); lumber   (Radial, tangential, mixed-sawing I) - then 2, 3, 4 pitched beams, board (for flooring) untreated, a trim, edging - with a blunt-edged - with a sharp-edged, bar; the hollow and slaty region, the sleeper is not edging / edging; veneer   (planed, peeled) (thin sections of wood, given thickness); milled / greased products: handrails; skirting boards; platbands; planking boards; roof tiles; parquet flooring; from glued semi-finished products   - DCC (beams, frames, arches, trusses); parquet boards; parquet; window, door blocks; shields; plywood 3х, 5и, multilayered; cork coatings; based on waste   (3 or more sheets of plywood veneer many. Based on the press pr-i) chipboard; Fiberboard; wallpaper; wood plastics.

Properties.Pros: low average density at high strength characteristics; psychological impact; coefficient of constructive quality - high 0.8 steel - 0.5; ρрр ~ 600 kg / m3 Rs ~. Cons: possible occurrence of vices; high hygroscopicity and water absorption; the possibility of decay; flammability; anisotropy. Density, compression, stretching, bending Larch: 660 65 125 110 Spruce: 450 45 100 80 Birch: 630 55 165 110. Anisotropy - different resistance along and across the fibers. Thermal conductivity, compressive strength, stretching along - exceeds across. Water absorption - EAF - no more than 15%. Decay at a humidity of more than 20%.

Application

built: chopped log architecture: the Kizhi Pogost and the Transfiguration Church, overlapping of the unbroken beams of the Town Hall building in Nürtingem (Germany)

const-department: the church in Lafayette (USA), lined with shingle; Parquet in the interior of the building MARHI,

finishing: plywood facing the audience in the 4 building MARHI, wallpaper - a massive application in the interiors of apartments

opportunities and achievements: The main achievement can be considered the elements of DCC - wooden glued structures (beams, frames, arches, trusses) spans of such structures up to 100 m and more, which makes wood a promising raw material not only for finishing and constructive department, but also for structural materials . Important and protective treatment. Transparent (even more texture) and opaque finishing of the face (paint, lining with adhesive paper) - for wood of inexpensive rocks with an inexpressive texture, imitating the finish (for more expensive raw materials). A labor-intensive type of decoration - mosaic (incrustation (with other mater), intarsia (ancient wood), marquetry (mosaic set of pieces of veneer of different breeds of wood), block mosaic.

Natural stone.

Extraction.Obtained by mining and processing of rocks. (Stonehenge, pyramids, gothic).

Raw materials.   For the manufacture of materials from the natural stone, the rocks are rock-solid, consisting of the same mineral. Classification of the gynecological: 1. igneous rocks: massive / deep (granite) / spillage (basalt). Clastic: Cemented (tuff, penza); Loose (ash). 2. Sedimentary rocks: Mechanical (sandstone - cemented, clay, sand, gravel - loose); Chemical education (gypsum stone); Organic (limestone, chalk). 3. Metamorphic (marble, quartzite): modified: Izv-e (gneiss); sedimentary (marble, quartz, slate).

Treatment.   Obtaining the required form:

shearing; cutting. grinding - for the required invoice. According to the processing of texture of the 2 groups: abrasive (sawed, coarse- and thin-polished, polished, polished) and shock ("rock", coarse and fine-grained, coarse and fine-grained, furrowed, pointed, forged) also opened (ultrasound) , heat-treated.

Kinds:   1. Blocks: for foundations; for the walls. 2. Plates. 3. Profile: portals, balusters, belts, skirting boards, handrails. 4. Small forms.

Properties.   Hardness:   atstrong and durable. Solid (granite, gneiss, diorite, syenite, basalt, labradorite) . Medium hardness (mammoth (achromatic and chromatic), conglomerate, limestone, sandstone, tuff) . Soft (talcum, gypsum).   Density:Solid - 2500-3000kg / m3 , Middle tv. - 1000-2800 . Porosity:TV. - 0.1-0.5% , Ср тв - 0.5-27% (limestone) . Water absorption:   TV. - 0.01-5% , Wed tv. - 0.1-40% Frost resistance:   Тв - 300 cycles Ср тв - more than 25, Мягк - 15 and more. Compressive strength:   Tv 90-300 MPa Ct tv - 60-200 MPa Soft - 15-30MPa., Tearability   not more than 0.5 g / cm2, durabilityis connected with hardness   Aesthetic properties:almost all colors of the color spectrum. Texture:   abrasive: sawed (3mm) / coarse sanding (0.2-0.5mm, traces of tools) / fine-grained (smooth, matte-I) / polished (mirror Gloss) / furrow (3mm); impact rock (5mm) / coarse-hummocky (7-15 mm) / finely billed (3-6 mm) / coarse-rift (1-2 mm parallel furrow) / m (0.5-0.7 mm ) / point / forged (0.5 - 2 mm). Opened - matte surface with a well-defined texture, Heat-treated - rough.

The basic properties of building materials determine, as a rule, the areas of their application and, according to the totality of the characteristics, are divided into chemical, physical, mechanical and technological.
  Properties of building materials determine the areas of their application. Only with proper evaluation of the quality of materials, ie their most important properties, can be obtained strong and durable building structures of buildings and structures of high technical and economic efficiency.
  All the properties of building materials are divided into physical, chemical, mechanical and technological characteristics.
  K include the weight characteristics of the material, its density, permeability for liquids, gases, heat, radioactive emissions, as well as the ability of the material to resist the aggressive action of the external operating environment. The latter characterizes the resistance of the material, which ultimately determines the safety of building structures.

Chemical properties are evaluated by the indicators of the resistance of the material under the action of acids, alkalis, salt solutions, which cause exchange reactions in the material and its destruction. characterized by the ability of the material to resist compression, stretching, impact, as well as indenting an extraneous body and other kinds of influences on the material with the application of force.
  Technological properties - the ability of the material to be processed in the manufacture of products from it.

Properties of building materials

The properties of the building material are determined by its structure. To obtain the material of the given properties, it is necessary to create its internal structure, which provides the necessary technical characteristics. Ultimately, knowledge of the properties of materials is necessary for the most effective use of it in specific operating conditions.

Table 1. The main properties of some building materials (in air-dry state)

The structure of the building material is studied at three levels:
macrostructure - the structure of the material visible to the naked eye; microstructure - a structure visible through a microscope; the internal structure of matter, studied at the molecular ion level (physical and chemical methods of investigation - electron microscopy, thermography, X-ray diffraction analysis, etc.).

The macrostructure of solid building materials (excluding rocks with their geological classification) is divided into the following groups: conglomerate, cellular, fine-pore, fibrous, layered and loose-grained (powdery). Artificial conglomerates are a large group.

Picture 1. Ceramic walling materials

These are various types of concrete, ceramic and other materials. The cellular structure of the material is characterized by the presence of macropores. It is characteristic of gas and foam concrete, gas silicates, etc. The fine-pore structure is characteristic, for example, for ceramic materials obtained as a result of burnout of introduced organic substances. The fibrous structure is inherent in wood, mineral wool products, etc.

Figure-2. Roll material for flooring

Laminated structure is typical for sheet, plate and roll materials. Loose materials are aggregates for concretes, solutions, various types of backfill for heat and sound insulation, etc.
  The microstructure of building materials can be crystalline and amorphous. These forms are often only different states of the same substance, for example quartz and various forms of silica. The crystalline form is always stable. To cause chemical interaction between quartz sand and lime in the production of silicate brick, autoclave treatment of raw with saturated steam with a temperature of 175 ° C and a pressure of 0.8 MPa is used.

At the same time, trembling (amorphous form of silica silica) with lime during water quenching forms calcium hydrosilicate at a normal temperature of 15 ... 25 ° C. The amorphous form of matter can transform into a more stable crystalline form. For polymeric materials, the phenomenon of polymorphism is of practical importance, when one and the same substance can exist in various crystalline forms, called modifications.

Polymorphic transformations of quartz are accompanied by a change in volume. A crystalline substance is characterized by a certain melting point and the geometric shape of the crystals of each modification. The properties of single crystals in different directions are not the same. Thermal conductivity, strength, electrical conductivity, dissolution rate and anisotropy phenomena are a consequence of the internal structure of the crystals. In construction, polycrystalline stone materials are used, in which different crystals are oriented randomly. These materials in their properties are isotropic, except for layered stone materials (gneisses, shales, etc.).

Figure-3. Shield-stone

The internal structure of the material determines its mechanical strength, hardness, thermal conductivity and other important properties.

The crystalline substances that make up the building material are distinguished by the nature of the bond between the particles forming the crystal lattice. It can be formed by: neutral atoms (the same element, as in diamond, or different elements, as in SiO2);

Ions (unlike charged, as in calcite CaCO3, or with the same name, as in metals); whole molecules (ice crystals).
  A covalent bond, usually carried out by an electron pair, is formed in crystals of simple substances (diamond, graphite) or in crystals consisting of two elements (quartz, carborundum). Such materials are characterized by high strength and hardness, they are highly refractory.
  Ionic bonds are formed in crystals of materials, where the bond has a mainly ionic character, for example gypsum, anhydride. They have low strength, not water resistant.

Figure-4. Feldspar

In relatively complex crystals (calcite, feldspars), covalent and ionic bonds also occur. For example, in a calcite within a complex CO 2/3 ion, the bond is covalent, but with Ca2 + ions is ionic. Calcite CaCO3 has high strength, but low hardness, feldspars have high strength and hardness.

Molecular bonds are formed in crystals of those substances in whose molecules the bonds are covalent. The crystal of these substances is constructed of whole molecules that are kept near each other by relatively weak van der Waals forces of intermolecular attraction (ice crystals) having a low melting point.

Silicates have a complex structure. Fibrous minerals (asbestos) consist of parallel silicate chains, interconnected by positive ions located between the chains. Ionic forces are weaker than covalent bonds within each chain, so the mechanical forces, insufficient for breaking the chains, dismember this material to fibers.

Figure-5. The lamellar mineral of mica

Plate minerals (mica, kaolinite) consist of silicate groups bound in flat mesh. Complex silicate structures are built of SiO4 tetrahedra, bound together by common vertices (oxygen atoms) and forming a bulk lattice, therefore they are considered as inorganic polymers.

The building material is characterized by chemical, mineral and phase composition. The chemical composition of building materials allows us to judge a number of properties of the material - mechanical, fire resistance, biostability, and other technical characteristics. The chemical composition of inorganic binders (lime, cement, etc.) and natural stone materials is conveniently expressed by the content of oxides in them (%).

The basic and acidic oxides are chemically bonded and form minerals that characterize many properties of the material. The mineral composition indicates what minerals and in what amount is contained in this material, for example in Portland cement, the content of tricalcium silicate (3CaO · SiO2) is 45 ... 60% more content of this mineral accelerates the hardening process and increases strength.

The phase composition and phase transitions of water in its pores have a great influence on the properties of the material. In the material, the solids that form the walls of the pores are released, that is, the framework and pores filled with air or water. The change in the water content and its state changes the properties of the material.

Classification and standardization of properties

The main and special properties of building materials can be divided into the following groups, taking into account those effects on materials that occur under operating conditions: state parameters and structural characteristics, determine? Technical properties: chemical, mineral and phase composition; specific mass characteristics (density and bulk density) and porosity; dispersibility of powdery materials;

physical properties: rheological properties of plastic-viscous materials; properties hydrophysical, thermophysical, acoustic, electrical, determining the ratio of the material to various physical processes; resistance to physical corrosion (frost resistance, radiation resistance, water resistance);

mechanical properties that determine the ratio of the material to the deforming and destructive effect of mechanical loads (strength, hardness, elasticity, plasticity, brittleness, etc.);

chemical properties: ability to chemical transformations, resistance against chemical corrosion; durability and reliability.

The properties of materials are estimated by numerical indicators established by testing in accordance with standards. In the USSR, a unified state standardization system has been created that allows the application of standardization in all sectors of the national economy. This ensures the effectiveness of the standards as one of the means to accelerate scientific and technological progress and improve the quality of products.

The system of standardization bodies and services is represented by the All-Union Standardization Body (the State Committee of Standards of the Council of Ministers of the USSR) and its services - the standardization service in the branches of the national economy, the standardization service in the Union republics. Depending on the scope of the standards, the standards are divided into four categories: state (GOST), sector (OST), republican (PCT) and enterprise standards (STPs).

State standards are an obligatory document for all enterprises, organizations and institutions, regardless of their departmental subordination, in all branches of the national economy of the USSR and the Union republics. In accordance with the decision of the Council of Ministers of the USSR, they are approved by the State Standard, and the standards in the field of construction and building materials are approved by the USSR Council of Ministers.

In the field of building materials and products, the most common standards are: technical conditions; technical requirements; types of products and their main parameters, test methods; rules of acceptance, marking, packaging, transportation and storage.

Standards of technical requirements normalize the quality, reliability and durability of products, its appearance. However, such standards establish the warranty period of service and the completeness of the delivery of products. Most standards for building materials and products are standards of technical requirements. A significant part of the requirements in the standards is related to the physical and mechanical characteristics of materials (bulk density, water absorption, humidity, strength, frost resistance).

One of the features of the state system of standardization in construction and technology of building products is that, in addition to the standards, there is a system of normative documents incorporated into the Building Norms and Rules (SNiP). SNiP is a set of all-Union normative documents on design, construction and construction materials, mandatory for all organizations and enterprises.

The methodological basis for standardizing dimensions in the design, manufacture of construction products and in the construction of structures is the Unified Modular System (EMC). This system is a set of rules for coordinating the dimensions of elements of buildings and structures, building products and equipment on the basis of a basic module equal to 100 mm (denoted by 1M). The application of EMC makes it possible to unify and reduce the number of standard sizes of building products. This ensures interchangeability of parts made of different materials or differing in design. Products and parts of the same sizes, manufactured in accordance with the requirements of the EMC, can be used in buildings for a variety of purposes.

A single modular system includes derivative modules that are obtained by multiplying the main module by integer or fractional coefficients. When multiplying by integer coefficients, the aggregated modules are formed, and when multiplying by coefficients less than one, fractional modules are formed (Table 2).

Table 2. EMC Module Dimensions

Derived enlarged modules (60M, 30M, 12M) and multiples thereof are recommended for the application of longitudinal and transverse steps of buildings. Modules 6M, 3M, 2M are designed for the separation of structural elements in terms of buildings, purpose

width of the openings. The main module 1M and fractional modules from 1 / 2M to 1 / 20M are used to assign cross-sectional dimensions to relatively small elements (columns, beams, etc.). The smallest fractional modules (from 1 / 10M to 1 / 100M) are used to assign plate and sheet thicknesses, gap widths, tolerances.

The building codes and rules created in the USSR are of great international importance. The decision of the CMEA Standing Commission on the construction of SNiP was taken as the basis for unified norms and rules in the field of construction for all CMEA member countries.

Standardization work on an international scale is carried out by the International Organization for Standardization (ISO), specially created in 1947. The activities of ISO, as stated in its charter, are aimed at promoting the favorable development of standardization throughout the world in order to facilitate international exchange of goods and to develop mutual cooperation in the field of scientific, technical and economic activities. In addition to ISO, the Council for Mutual Economic Assistance and its International Institute for Standardization conduct active work in the field of international standardization and socialist economic integration.

Relationship of structure and properties

Knowledge of the structure of the building material is necessary to understand its properties and, ultimately, to solve the practical question of where and how to apply the material in order to obtain the greatest technical and economic effect.

The structure of the material is studied on three levels: 1) the macrostructure of the material - the structure visible to the naked eye; 2) microstructure of the material - a structure visible in an optical microscope; 3) the internal structure of the substances composing the material at the molecular ion level, studied by X-ray diffraction analysis, electron microscopy, and so on.

Macro structure   solid building materials * can be of the following types: conglomerate, cellular, fine-porous, fibrous, layered, loamy (powdery). * Note: natural stone materials do not belong here, because the rocks have their own geological coassification.

Artificial conglomerates are an extensive group that combines concrete of various types, a number of ceramic and other materials.

The cellular structure is characterized by the presence of macropores characteristic of gas and foam concrete, cellular plastics.

A fine-porous structure is characteristic, for example, of ceramic materials, porous methods of high water saturation, and the introduction of burn-out additives.

The fibrous structure is inherent in wood, fiberglass, mineral wool products, etc. Its feature is a sharp difference in strength, thermal conductivity and other properties along and across the fibers.

The laminated structure is distinctly expressed in roll, sheet, plate materials, in particular, for plastics with layered filler (bumoplast, textolite, etc.).

Loamy materials are aggregates for concrete, granular and powdery materials for mastic thermal insulation, backfill, etc.

Microstructure of substances, which make up the material, can be crystalline and amorphous. Crystalline and amorphous forms are often only different states of the same substance. An example is crystalline quartz and various amorphous forms of silica. The crystalline form is always more stable.

In order to cause chemical interaction between quartz sand and lime, the technology of silicate brick uses autoclave processing of the molded raw with saturated water vapor with a temperature of at least 175 ° C and a pressure of 0.8 MPa. Meanwhile, trepel (an amorphous form of silicon dioxide) together with lime after water quenching forms calcium hydrosilicate at a normal temperature of 15 - 25 ° C. The amorphous form of matter can transform into a more stable crystalline form.

Practical significance for natural and artificial stone materials has the phenomenon of polymorphism - when the same substance can exist in various crystalline forms, called modifications. For example, polymorphic transformations of quartz accompanied by a change in volume are observed.

A feature of the crystalline substance is a certain melting point (at constant pressure) and a certain geometric shape of the crystals of each of its modifications.

The properties of single crystals are not the same in different directions. This is the mechanical strength, thermal conductivity, dissolution rate, electrical conductivity, etc. The phenomenon of anisotropy is a consequence of the peculiarities of the internal structure of the crystals.

In construction, polycrystalline stone materials are used, in which different crystals are randomly oriented. Such materials are considered as isotropic in their construction and technical properties. The exception is made of layered stone materials (gneisses, shales, etc.).

The internal structure of substances,   making up the material, determines the mechanical strength, hardness, refractoriness and other important properties of the material.

The crystalline substances that make up the building material are distinguished by the nature of the bond between the particles forming the spatial crystal lattice. It can be formed by: neutral atoms (the same element, as in diamond, or different elements, as in SiO2); ions (unlike charged, as in CaCO3, or with the same name, as in metals); whole molecules (ice crystals).

Covalent bonding, usually carried out by an electron pair, is formed in crystals of simple substances (diamond, graphite) and in crystals of certain compounds of two elements (quartz, carborundum, other carbides, nitrides). Such materials are distinguished by very high mechanical strength and hardness, they are highly refractory.

Ionic bonds are formed in crystals of those materials in which the bond has a predominantly ionic character. Common building materials of this type gypsum and anhydride have low strength and hardness, not water resistant.

In complex crystals, often found in building materials (calcite, feldspar), both covalent and ionic bonds are realized. Inside the complex C03-2 ion, the bond is covalent, but it itself has an ionic bond with Ca + 2 ions. The properties of such materials are very diverse. Calcite CaCO3 has a low hardness at sufficiently high strength. The feldspars combine rather high strength and hardness parameters, although they are inferior to diamond crystals with a purely covalent bond.

Molecular crystal lattices and their corresponding molecular bonds are formed mainly in crystals of those substances in whose molecules the bonds are covalent. The crystal of these substances is constructed of whole molecules, which are held together by relatively weak van der Waals forces of intermolecular attraction (as in ice crystals). When heated, bonds between molecules are easily destroyed, so materials with molecular lattices have low melting points.

Silicates occupying a special place in building materials have a complex structure that determines their features. Thus, fibrous minerals (asbestos) consist of parallel silicate chains, connected among themselves by positive ions located between the chains. Ionic forces are weaker than covalent bonds within each chain, so mechanical stresses, insufficient for breaking the chains, divide such material into fibers. Plate minerals (mica, kaolinite) consist of silicate groups bound in flat mesh.

Complex silicate structures are constructed of Si04 tetrahedra, bound together by common vertices (common oxygen atoms) and forming a bulk lattice. This gave grounds for considering them as inorganic polymers.

Relationship of composition and properties

The building material is characterized by chemical, mineral and phase composition.

The chemical composition of building blocks, that is, the "skeleton" of the material, and the pores filled with air and water. If the water that is a component of this system freezes, then the ice formed in the pores changes the mechanical and thermal engineering materials allows us to judge a number of properties of the material: fire resistance, biostability, mechanical and other technical characteristics. The chemical composition of inorganic binders (cement, lime, etc.) and stone materials is conveniently expressed by the amount of oxides contained in them (in%). Basic and acid oxides are chemically linked and form minerals, which determine many properties of the material.

Mineral composition shows what minerals and in what quantities are contained in the binding material or in the stone material. For example, in portland cement, the content of tricalcium silicate (3CaO-Si02) is 45-60%, and at higher amounts, hardening accelerates, and the strength of cement stone rises.

The phase composition of the material and the phase transitions of water in its pores affect all properties and behavior of the material during operation. In the material, the solids that form the walls of the material properties are isolated. An increase in the volume of freezing water in the pores causes internal stresses that can destroy the material during repeated cycles of freezing and thawing.

LABORATORY WORK № 1

GENERAL TECHNICAL PROPERTIES

BUILDING MATERIALS

GENERAL TECHNICAL PROPERTIES OF CONSTRUCTION MATERIALS

The main technical properties of all building materials include: mass, density, porosity, strength, water absorption, frost resistance. They serve both for assessing the quality and specifics of the application of materials, and for various technical and economic calculations.

Some of the properties are special and important when choosing a material only for certain operating conditions (water resistance, chemical resistance, thermal conductivity, etc.).

The main properties of building materials are determined on standard samples in accordance with GOST, observing the following conditions:

- The mass of the samples is determined with an error of not more than 0.1%.

- The sizes of samples of the correct geometrical form define with an error no more than 1 mm.

- The volume of samples of an irregular geometric shape is determined with an error of not more than 1%.

- The air temperature in the room in which the samples are tested should be (25 ± 10) ° C, and the relative humidity of the air - not less than 60%.

Weight- the aggregate of material particles (atoms, molecules, ions) contained in a given body. The mass has a certain volume, i.e. occupies a part of space. It is constant for a given substance and does not depend on the speed of its movement and the position in space. The bodies of the same volume, consisting of different substances, have an unequal mass. To describe the differences in the mass of substances having the same volume, the concept of true and average density is introduced.

True density   - the mass of a unit volume of a material substance in an absolutely dense state, i.e. without pores and voids. The simplest instruments with which the true density is determined are the Le Chatelier (see Fig. 1) and a pycnometer.

Fig. 1. The Le-Chatelier

To prepare the sample, we take a sample of material with a mass of at least 30 g and crush it until it passes through a No. 02 mesh screen. The milling is carried out in order to eliminate the porosity. The prepared powder sample of the sample material is dried to constant weight at a temperature of 105-110 ° C. The sample is then cooled to room temperature in a desiccator to avoid absorption of moisture from the air.

The determination of the true density is carried out in parallel on two weights of about 10 g each, sampled from the sample. The selected sample is poured into a clean, dried and previously weighed pycnometer. The pycnometer is weighed together with the test powder, then poured into it water (or other inert liquid) in such an amount that it is filled to approximately half the volume.

To remove air from the sample and liquid material, the pycnometer with the contents is kept under vacuum in a desiccator until the bubbles are stopped. It is allowed (when using water as a liquid) to remove air by boiling the pycnometer with the contents for 15-20 minutes in a slightly inclined state on a sand or water bath.

After the air is removed, the pycnometer is filled with liquid to the mark. The pycnometer is placed in a thermostat with a temperature (20.0 ± 0.5) ° C, in which it is held for at least 15 minutes. After soaking in the thermostat, the liquid level is brought to the mark on the lower meniscus. After reaching a constant liquid level, the pycnometer is weighed. After weighing, the pycnometer is released from the contents, washed, filled with the same liquid, air is removed from it, kept in a thermostat, brought to a constant level and weighed again.

The true density (i) of the sample material in g / cm 3 is calculated by the formula

where the mass of a pycnometer with a sample, g;

Weight of the pycnometer, g;

Density of liquid, g / cc;

Mass of a pycnometer with a liquid, g;

Mass of pycnometer with sample and liquid, g.

For the value of the true density of products, the arithmetic mean of the results of the determinations of the true density of the material of two samples is calculated, with an accuracy of 0.01 g / cm 3. The discrepancy between the results of parallel determinations should not be more than 0.02 g / cm 3. For large discrepancies, the true density of the articles is determined again.

Average density   - the ratio of the mass of the sample of the material to the entire volume occupied by it, including the pores and voids in it. The average density is calculated by the formula

where the mass of the material, kg;

Volume of material in natural state, m 3;

The volume of samples of the correct geometric shape is calculated by their geometric dimensions. If the sample has the shape of a cube or a parallelepiped, then its length, width and height are measured, with each face being measured in three places and calculating the arithmetic mean. When determining the volume of a sample of a cylindrical shape, two mutually perpendicular diameters are drawn on each of the two parallel bases of the cylinder and measured, and the diameter of the cylinder is determined in a mutually perpendicular direction along the middle of the height of the cylinder. At the points of intersection of segments of diameters with the circumference of the bases, the height of the cylinder is measured. The diameter of the cylinder is calculated as the arithmetic mean of the six specified measurements. The height of the cylinder is determined similarly, starting from the four available measurements.

The volume of samples of irregular geometric shape is determined by means of a volume meter or by hydrostatic weighing. The volume is a vessel of arbitrary shape (Figure 2), the value of which allows testing the available samples. The tube is soldered into a tube with an internal diameter of 8-10 mm with a bent end. The volume is filled with water at a temperature of (20 ± 2) ° C until it flows from the tube. When the drop drops from the tube, a pre-weighed container is placed under it. The sample prepared for testing is gently immersed on a thin wire or thread into the volume meter, while water displaced by the sample flows through the tube into the vessel. After stopping the fall of the drops, the container with water is weighed and the mass and volume of the displaced water are determined V В   in cm 3 by the formula

where t 1 –   mass of empty container, g:

t 2 – mass of the container with water displaced by the sample, g;

r B   - the density of water, taken to be 1.0 g / cm 3.

1 - vessel; 2 - a tube; 3 - water collecting tank

Fig. 2. The odometer.

The volume of the sample on the hydrostatic balance is determined by weighing it in air and water in accordance with the scheme shown in Fig. 3.

1 - a vessel with water; 2   - suspension for the sample; 3 - sample; 4 –   Libra;

5 –   weights

Fig. 3. Hydrostatic balance.

The accuracy of determining the average density depends on the porosity of the material, since a sample immersed in a liquid not only displaces but also absorbs it. Samples that have a fine-porous structure are paraffined or saturated with water for at least 24 hours before the test.

The volume of pre-saturated samples V   0 in cm 3 is determined by:

where is the mass of the sample saturated with water, determined by weighing in air, g;

  - mass of water-saturated sample, determined by weighing in water, g;

  - density of water, taken equal to 1 g / cm 3.

Waxing is carried out as follows. The sample, dried to constant weight, is heated to 60 ° C. and several times immersed in molten paraffin so that a paraffin film with a thickness of about 1 mm is formed on its surface. After that, the sample is weighed.

The volume of samples prepared for the test by waxing determines:

- when tested in a volume by formula

- when tested on a hydrostatic balance by formula

where –

–   mass of paraffined sample, determined by weighing in air, g;

–   the mass of the wax sample, determined by weighing in water, g;

  - the density of paraffin, taken equal to 0.93 g / cm 3.

The average density is determined by no less than three samples. The final result is the arithmetic mean of the mean density of the three measurements.

Bulk density   - typical for bulk materials (cement, sand, gravel, gravel, etc.). In this case, the volume of the material includes not only the pores in the material itself, but also the voids between the grains or pieces of material.

Bulk density of loose materials is determined by weighing a certain volume of material. To establish the bulk density of fine-grained materials, a vessel of 1 liter is used. For coarse materials use cylindrical vessels with a volume of 5 to 50 liters.

The definition is as follows. From a special funnel or with a scoop, pour the material into a previously weighed vessel with a small excess, which is then removed with a metal ruler flush with the edges of the vessel. After this, the vessel filled with the material is weighed. Bulk density is determined by the formula:

where t -   mass of a measuring vessel, g;

t   1 - mass of a measuring vessel with sand, g;

V -   volume of a measuring vessel, cm 3.

Porositymaterial () is characterized by the degree of filling its volume with pores and is calculated in percent by volume according to the following formula:

where - average density of sand, kg / m 3;

  - true density of sand, kg / m 3;

Voidness -(the volume of intergranular voids) of bulk materials in the standard unconsolidated state is determined on the basis of the values ​​of true density and bulk density. Voidness () in percent by volume is calculated by the formula

where is the true density of sand, kg / m 3;

  - bulk density of sand, kg / m 3.

Water Absorption   Is the property of the material to absorb and retain water in itself when it comes into direct contact with it. Water absorption depends on the presence of open pores in the material.

Water absorption can be determined by three methods: 1) constant immersion of the test sample in water; 2) by boiling the sample with water; 3) evacuation.

The procedure for determining water absorption by the first method following. Pre-dried at 110 ° C and suspended samples are placed in a container filled with water so that the water level in the container is above the upper level of the stacked samples by approximately 50 mm. The samples are laid in such a way that the height of the sample is minimal (prisms and cylinders are laid on their sides). The water temperature in the tank should be (20 ± 2) ° C. Samples are weighed every 24 hours of water absorption with an error of not more than 0.1%. When weighing, the samples taken from the water are pre-wiped with a dampened cloth. The mass of water that has leaked from the sample pores to the scale pan should be included in the mass of the saturated sample. The test is carried out until the results of two consecutive weighings differ by no more than 0.1%.

When determining the water absorption by boiling the samples ( the second method) the samples are prepared and placed in a vessel with water similarly to the first method, heated and brought to a boil (about 1 hour), boiled for about 5 hours and allowed to cool to room temperature. After that, the samples are weighed in the order indicated above.

Vacuuming the samples ( the third method) are produced as follows. Prepared samples are placed in a vacuum dessicator (container) on a stand and filled with water so that its level is higher than the top of the sample by at least 2 cm. The desiccator is closed with a lid and vacuum (0.05 ± 0.01) MPa [(0.5 ± 0.1) kgf / cm 2], fixed by a manometer. The lowered pressure is maintained, cutting the time until the air bubbles from the samples stop, but no more than 30 minutes. After restoring the atmospheric pressure, the samples are kept in water for as long as under vacuum, so that water fills the volume that was occupied by the remote air. Then they act like the first two methods.

The water absorption of the sample by weight in percent is determined with an error of up to 0.1% by the formula:

where –   mass of the dried sample, g;

–   mass of water-saturated sample, g.

The water absorption of the sample by volume in percent is determined with an error of up to 0.1% by the formula:

where V   Is the volume of the sample, cm 3.

Humidity material is determined by the moisture content contained in the pores and adsorbed on the surface, referred to the mass of the material in the dry state. Humidity depends both on the properties of the material itself (porosity, hygroscopicity), and on the environment (air humidity, contact with water). To determine this property, it is necessary to weigh the sample in its natural state, and then dry it to constant weight and weigh again. Humidity in percent by weight is determined by the formula:

where –   mass of the sample in the natural state, g;

–   weight of dried sample, g.

Frost resistance   - the property of a water-saturated material to withstand repeated alternating freezing and thawing without signs of deterioration, a significant reduction in strength and mass loss.

Freezing of water filling the pores of the material is accompanied by an increase in its volume by approximately 9%, resulting in pressure on the pore walls, leading to the destruction of the material. However, in many porous materials, water can not fill more than 90% of the volume of available pores, so the ice formed during freezing of water has free space for expansion. Therefore, the destruction of the material occurs only after repeated alternating freezing and thawing.

Taking into account the heterogeneity of the structure of the material and the uneven distribution of water in it, a satisfactory frost resistance can be expected in such porous materials in which water fills no more than 80% of the pores, i.e. the volume water absorption of such materials is not more than 80% of the open porosity. Dense materials that do not have pores, or materials with a slight open porosity, water absorption of which does not exceed 0.5%, have high frost resistance. Frost resistance is of great importance for wall materials systematically subjected to alternating freezing and thawing, as well as for materials used in foundations and roofing.

To determine the frost resistance of materials, control and basic samples are saturated with water. Control samples after water saturation are tested for strength. The main samples are loaded into a freezer in a container or placed on a mesh rack of the chamber in such a way that the distance between the samples, the walls of the containers and the overlying shelves is not less than 50 mm. The beginning of freezing is considered the moment of establishment in the chamber of temperature minus 16 ° С. Samples after freezing are thawed in a bath of water at a temperature of (18 ± 2) ° C. In this case, the samples should be immersed in water in such a way that above the upper face there is a layer of water not less than 50 mm. The duration of the freezing and thawing cycles depends on the type of material and the size of the sample. The number of cycles of variable freezing and thawing, after which the strength or mass loss of samples should be determined, is established in accordance with GOST for the test material.

The material is considered to be frost-resistant if, after a specified number of freezing and thawing cycles, the loss in mass of the samples as a result of crushing and delamination does not exceed 5%, and the strength decreases by no more than 25%. The degree of frost resistance of the material can be characterized by the coefficient of frost resistance:

where is the ultimate strength at compression of the samples of the material after the frost resistance test, MPa; - ultimate strength at compression of water saturated material, MPa.

According to the number of cycles of alternating freezing and thawing, the materials are divided into F10; F15; F25; F35; F50; F100; F150; F200 and more.

For some materials, there are accelerated methods for determining the frost resistance of materials. The essence of one of the methods is to saturate the main and control samples before testing with a 5% aqueous solution of sodium chloride. The samples are then tested according to the above procedure only with the difference that thawing is carried out in a solution of sodium chloride. Another accelerated method is similar to that described, but the temperature in the freezer is lowered to - (50-55) ° C. For example, for concrete that has withstood 8 cycles of accelerated alternating freezing-thawing by the third method or 75 cycles by the second method, a frost resistance mark F300 is assigned.

Strength - the ability of a material to resist destruction from the action of internal stresses that arise under the influence of an external load. Since in real constructions the material undergoes various internal stresses - compression, stretching, bending, shearing, torsion, the strength of materials is usually characterized by the magnitude of the compressive strength, tensile strength, bending, etc. Numerically, the ultimate strength is equal to the voltage corresponding to the load, which caused the destruction of the sample of the material.

The compressive strength or tensile strength, MPa is equal to the destructive force per 1 m 2 of the initial section of the material at the moment of sample failure:

where is the destructive force, H;

  - cross-sectional area of ​​the sample, mm 2.

where is the destructive force, H;

  - span between supports, mm;

AND - width and height of the cross-section of the beam, mm.

Bending strength at one concentrated load and rectangular sample beam:

where is the distance between the loads, mm.

The ultimate strength of the material is determined experimentally by testing specially prepared samples (destructive methods) in the laboratory on hydraulic presses or rupturing machines, or by means of non-destructive methods - sclerometric, ultrasonic, etc. To test a sample for compression, the samples are made in the form of a cube or a cylinder, in tension - in the form of round bars, strips or "eights", and for bending - in the form of beams. The shape and dimensions of the samples must strictly comply with the requirements of GOST for each type of material.

Strength of building materials is usually characterized by a mark that corresponds to the strength of the compressive strength obtained by testing samples of standard shapes and sizes. For example, the brand designation for compressive strength M150 corresponds to a strength of 150 kgf / cm 2 (15MPa).

• Physical properties and characteristics
• Mechanical properties
• Chemical properties

To build qualitatively and professionally, you need to have a clear idea of ​​the building materials: their basic properties and the permissibility of their use in the construction of a specific design. It affects the quality of products and, accordingly, the reputation of the builder.

All the basic building materials are endowed with signs and characteristics, which are manifested in the greatest or least extent. The qualitative manifestation depends on the purpose of the material and its application in a particular situation.

Building materials have physical characteristics, mechanical properties and chemical characteristics.

Physical properties and characteristics

Among the properties classified as physical, weight, specific and volume, the degree of density, the presence of porosity, the capacity for water absorption, the degree of moisture output and humidity are often considered.

Also take into account how much the material is frost-resistant, is it capable of carrying gas, is it resistant to fire and high temperatures and whether it has thermal conductivity.

To calculate the volumetric weight, this formula is used: γ0 = G / V, where G is the weight, and V1 is the volume of the material, including pores and voids. Unit of volumetric weight kg / m³. Often the bulk weight is less than the specific gravity. This characteristic is important in calculating the strength of the structure and the organization of transportation by vehicles.

The density indicates the measure of filling the volume of the sample with the substance from which this sample consists. The density unit is used in kg / m³. The amount of pores present inside the sample almost always affects its density index.

The concept of porosity implies the presence of pores in the material and shows how much its volume is filled and measured in percent. There are small and large pores. Consequently, the materials are finely porous and coarse-porous.

By the degree of lightness, non-porous elements are inferior to porous elements. The size of the pores and their number affect the thermal insulation properties: the smaller the pores smaller in size, the stronger the thermal insulation characteristics of building elements.

The ability of a material to absorb water and retain it is called water absorption, which is weight and volume. The weighting is measured as a percentage and represents the ratio of the weight of water absorbed into the sample to the limit, to the weight of the dry sample. The volumetric value is calculated as a percentage and is calculated as the ratio of the volume of absorbed water to the volume in the saturation state.

If the material can give off water, when the surrounding environment changes, it is capable of moisture yield, which is measured in percent. The value shows how much water evaporates from the sample within 24 hours under the condition of 20 ° C and 60% air humidity.

Humidity shows how much liquid, namely water, is contained in the material. The value is calculated as a percentage and is determined by the drying and titration methods according to Karl Fischer.

Frost resistance demonstrates whether a material containing moisture can be subjected to freezing and thawing many times without breaking down, without compromising its strength.

Many materials, in contact with water, are destroyed. This happens because the water in the pores freezes at a temperature below zero. The probability of failure increases, and strength decreases. Materials that absorb little water are more frost-resistant.

Gas permeability is possessed by building samples that pass gas (air) under the influence of pressure. Materials with large pores have a high degree of gas permeability. This figure is influenced by the size and characteristics of the pores.

Gas permeability should be especially taken into account in the construction of residential premises, where natural ventilation must necessarily take place. In other cases, requiring a reduction in gas permeability, this is achieved by plastering walls, coating them with oil-based paints or bituminous compounds.

If the element can transfer heat with a difference in the temperatures of the surfaces surrounding it, then it is capable of carrying out heat. The thermal conductivity is measured in W / (m * C). For example, the thermal conductivity of concrete is 1, 69, granite - 3.49, wood (pine) - 0.09. When installing walls, installing floors, laying the floor, especially the thermal conductivity is important.

Fireproof building materials do not break down when exposed to high temperatures. They are divided into elements that do not burn, burn quickly and difficult to burn. For example, brick and concrete are not flammable, can not smolder and turn into coals. Steel is highly deformed. Granite and limestone are destroyed, and wood and plastic are burning and smoldering.

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Mechanical properties

The mechanical properties of the material will tell you how strong it is, the spine, firm, brittle and plastic.

Strength of building materials is called their ability to maintain their integrity as a result of the action of certain loads on them.

When the material is compressed, bent or stretched, its strength is characterized by a value called the tensile strength. The ultimate strength is measured in MPa.

If the material is able to return to its original form and retain the previous size, undergoing deformation, then it has a certain degree of elasticity.

Deformation is achieved by applying various loads. This property is expressed by the elastic limit, calculated in MPa. Rubber and steel have elasticity.

If the material demonstrates resistance to the penetration of another body into it, such a material is called a solid. To determine the degree of hardness of steel, wood and concrete, a ball made of steel is pressed into pieces of materials, and then the depth of the indentation is determined.

If under the influence of external forces the material is destroyed, then it is classed as fragile. This is especially necessary to take into account when transporting materials (glass, tiles) to the building site.

The property of plasticity is defined as the ability of materials due to the impact on it of different forces to change the size and shape without the appearance of ruptures, and also to remain in a new form after the end of the action of the loads. Plastic, copper and steel are plastic.

Before laying the foundation, each developer puts before himself the main question - from what building material will be created the "child" he conceived.

There is an opinion that wooden houses   more economical in construction and comfortable for living. However, the cost of sawn timber in the suburbs in recent years jumped by more than three times. In the absence of felling tickets, the forest is imported not only from neighboring regions, but also very far from Moscow. The quality control of raw materials and their processing falls to an unacceptably low mark. The erected wooden "box" requires a serious facade and internal processing using additional expensive materials: foam, insulating, paint, fire-fighting mixtures, siding or plastic "lining".

  is one of the oldest building materials. The Great Wall of China and the Egyptian pyramids have passed the test of time and still delight the eyes of tourists. However, at present masonry is used very rarely. Stones of heavy rocks (granites, syenites, diorites) have high strength, frost resistance, water and air resistance, but their extraction is a very labor-consuming and costly process. Therefore, their use in practice is limited to lining and decoration of expensive architectural surfaces. Lung stones (density less than 1800 kg / m³) of rocks have a porous structure (limestone-shell rock, volcanic tuff, pumice), and, consequently, low thermal conductivity and ease of processing, but have low strength, frost resistance and water resistance. Such stones are used, as a rule, locally, where there are deposits of the corresponding rocks.

, which have become widely known in recent decades, have a number of undoubted advantages. The buildings built with their use have good sound insulation and thermal protection. The blocks themselves are lightweight, simple and economical to use, and also relatively inexpensive compared to some other building materials. However, often, developers do not take into account the significant shortcomings of this type of product. Physico-mechanical strength of foam concrete is rather low and does not allow to withstand heavy loads. Penoblochnye walls do not suffer deformations, therefore for them the deep ribbon foundation or the base-plate is required. After the completion of the masonry from the foam blocks before the beginning of their finishing should be at least a year, as the "box" before the beginning of the finish should "settle". In this process, cracks can form on the walls during the draft. High hygroscopicity of foam blocks (intensive absorption of moisture from the air itself) leads to additional shrinkage of this material, which significantly reduces the life of buildings. The minimal excess of the thickness of inter-joint seams during construction (more than 2-3 mm) minimizes heat and sound insulation characteristics. Deficiencies of foam concrete are also due to its composition containing blowing agents, which are usually chemical and poisonous in the combustion of mixtures.

The bulk of small-piece wall materials used in modern construction are products based on artificial stone materials . These are wall ceramic products (ceramic brick), silicate products of autoclave hardening (silicate brick), wall products from concrete of various composition (concrete stones and blocks).

The most famous and widespread since Soviet times red ceramic brick are obtained by the method of plastic molding and subsequent firing of low-melting clays or clay-treply mixtures. To reduce the volume weight of products and improve their thermal characteristics in the charge in the manufacture of additives, after burning which, when fired in a brick, numerous small pores are formed, which reduces their strength and moisture resistance. The range of products of domestic ceramic factories producing bricks until recently was not very large. At the same time, the largest share of manufactured products (about 70%) falls on ordinary (ordinary) building bricks. The natural color of ceramic bricks varies from light red to brown, which is due to the presence of iron oxides. The structures of this brick are unattractive and suggest further plastering or coating with facing material. In addition, the brick, under the influence of the external environment, has the property of self-destruction.

  is made by non-burning pressing from a mixture of quartz sand (90%), air lime and water. The molded article undergoes autoclave treatment - the action of saturated steam and pressure. As a result of the synthesis of hydrosilicates, an artificial conglomerate is formed. Silicate brick, in comparison with ceramic, has a higher density and, as a result, greater thermal conductivity. However, it is less resistant to water and substances dissolved in it. Therefore, it can not be used for laying foundations and socles of buildings, facing facades of structures, and also for walls with wet operation.

in recent years are becoming increasingly popular. If a decade ago in Russia, concrete wall stones were produced in a small volume: about 2 billion pieces. of conventional brick per year, which accounted for 2.5% of all wall materials, America and Europe already then built about 2/3 of all houses with their use. The concrete block is molded with subsequent setting from a mixture of binder (cement) with water, fine and coarse aggregate. According to the bulk weight of concrete, the stones are divided into three groups: blocks of heavy concrete (density of more than 1800 kg / m³), ​​blocks of lightweight concrete (density up to 1800 kg / m³), ​​cellular concrete blocks (density less than 1200 kg / m³). The density of concrete is determined by its structure and type of aggregate. The material is resistant to aggressive media, it does not slip under the feet and wheels, it does not fade, it has 100-percent resistance to ultraviolet rays. To the disadvantages of concrete in the "pure" form is its "coldness". Therefore, when building walls, it is necessary to use a layer of insulation. However, hollow concrete blocks are able to "keep" heat, which significantly saves costs for heating and air conditioning of the building. The use of painted facial blocks allows you to completely abandon the time-consuming and costly facade of the building. The production recipe makes it possible to produce concrete blocks of different characteristics, which makes it possible to use them for both low-rise and multi-storey construction, with a substantial saving of the mortar as compared to ceramic bricks.

A new step in the development of the construction industry heat-effective hollow blocks "TEPLOSTEN-M". This is the only one in the world practice sandwich concrete, not requiring additional   warming of bearing walls, protective and decorative finishing of building facades, internal rough finishing of premises. Three-layer construction of the block (sand-concrete or expanded clay concrete bearing layer, foam polystyrene inner layer, sand-concrete protective and decorative layer, interconnected by basalt-plastic reinforcing bars) provides maximum thermal insulation and sound insulation, water resistance and crack resistance, fire safety, ecological compatibility, durability and aesthetic appeal of cottages, apartment buildings and social facilities.

Since the use of blocks "TEPLOSTEN-M" allows the developer to abandon facade decoration materials, inter-wall heaters, grid reinforcement and plastering works, the time for any construction is reduced by one and a half to two times. At the same time, the cost of one square meter of a wooden, stone or foam block bearing wall with an additional insulation will cost 1.7 times, and a brick one - 2 times more expensive than the walls of the blocks "TEPLOSTEN-M".