Building Materials

Building materials serve for the construction of walls, foundations, floors, roofs and other parts of residential and non-residential buildings and structures. Building materials are usually divided into natural, which are used for construction in the form in which they are found in nature (wood, granite, limestone, clay, etc.), and artificial, prepared from natural raw materials (brick, concrete, slag concrete, solomite, etc.). Building materials are also conventionally divided into old and new, understanding the latter as materials that have entered into construction practice in recent years, even though the material may be geologically very old; hence the concept of "new materials" is quite conditional. The introduction of new materials into construction practice, especially in the USSR, is explained by the enormous growth of construction and the scarcity of old materials, as well as the revealed uneconomical nature of the latter. The thinning of walls through the use of new, cheaper heat-insulating building materials now makes construction more efficient. All building materials have common properties, which, by combining with each other, characterize the materials in terms of their suitability for construction in general and for various parts of a building in particular. These common properties include: 1) specific and bulk density, 2) porosity, 3) air permeability, 4) water absorption, 5) thermal conductivity, 6) heat capacity, 7) strength, 8) hardness, abrasion, brittleness, 9) frost resistance, 10) sound conductivity. From a hygienic point of view, the following properties of building materials are important: thermal conductivity, heat capacity, water absorption, air permeability and sound conductivity, which basically depend on the porosity and bulk density of the materials. A uniform, hygienically required thermal regime of a dwelling depends to a large extent on the low thermal conductivity of the building materials of the walls and their high heat capacity, as these properties ensure the heat resistance of the walls, i.e., their ability to retain heat and thereby regulate the temperature of the dwelling between stove heatings. Lower water absorption of materials prevents the walls from becoming damp (see Room Dampness). The air permeability of materials provides desirable natural ventilation of dwellings, provided it is not excessively high (more than 2.0), which can cause excessive heat loss in the dwelling and unpleasant sensations for the occupants. Poor sound conductivity gives peace and rest to the occupants. Thus, hygienic requirements for building materials come down to low thermal conductivity, high heat capacity, low water absorption, good but not excessive air permeability and poor sound conductivity. To determine thermal conductivity, various devices are used; a convenient device is in the form of a wooden frame, insulated inside with asbestos, into which slabs of the building material under study are inserted from both sides, thus forming a closed space with an electric stove placed inside, the energy consumption of which is measured by a meter and converted into thermal units. The temperature on the inner and outer surfaces of the slabs is measured by thermocouples. Knowing the area and thickness of the slabs and noting the time of the experiment, the thermal conductivity is calculated. To determine thermal conductivity, one can also use the formula of Prof. Nekrasov: λ = - 0.14 + 1/0.0196 + 0.22ρ², where ρ is the bulk density of the material in kg/m³ at its natural humidity. Heat capacity is determined, as in physics, in a calorimeter or by the void method or by the mixing method. Dampness (see Room Dampness) is determined by various methods. Water absorption is determined by the difference in weight of a sample of material before and after saturation with water (gradual immersion in water for several hours until the release of air bubbles ceases), calculated as a percentage of the weight of the sample or preferably of its volume. Air permeability is determined with the help of various devices, where air is either forced through the material under study or sucked through; the latter method is used in a device in the form of a tin box made of two halves, into which the sample under study is placed and sealed on the sides with mastic; the box is connected with a rubber tube to an aspirator (a bottle with a tap at the bottom, filled with water), which is connected to a water manometer; on the other side, the box is connected with a rubber tube to a vessel with H₂SO₄, in which the moisture of the air being drawn is retained. After establishing a constant vacuum, 1 liter of air is drawn through the building material (i.e., 1 liter of water is released from the bottle), the time is noted, and then the air permeability coefficient is calculated. Sound conductivity is determined in special acoustic chambers. Many building materials, especially new ones, are complex materials, the composition of which includes binders and fillers; their combination determines the sanitary-technical properties of the materials. In the form of mortars, they serve for bonding masonry elements, for preparing concrete and concrete blocks, and for plastering. Binders are divided into: air binders, which harden to a stone-like state only in the air, and hydraulic binders, which harden both in the air and under water. Air binders include 1) burnt lime, obtained by burning limestone until complete release of CO₂; when water acts on burnt lime, a fine powder of slaked lime-flour is obtained, which, with a clay and sand content of less than 13%, will be fat, with more than 33%-lean. With an excess of water, flour gives lime paste and milk; 2) gypsum, which depending on the degree of burning is divided into plaster, anhydrite and hydraulic, and after burning is ground, and 3) caustic magnesite (moderate burning of natural magnesite and its grinding), dissolved in a strong solution of MgCl₂. Hydraulic binders include: 1) hydraulic lime, obtained by moderate burning of marly limestones, i.e., containing clay impurities, from which it gets hydraulic properties, 2) Portland cement, 3) Roman cement and 4) aluminate (bauxite) cement. - Fillers or hydraulic additives are added to either lime or cement mortars and form a paste that hardens under water; the main active component is silica (SiO₂); they are divided into natural and artificial. Natural, or pozzolanic, ones with an acid reaction include: 1) pozzolanas, i.e., loose products of volcanic eruptions (in Italy, Greece, in USSR at the foot of Mount Kara-Dag near Feodosia-trass), 2) diatomite-a loose rock consisting of the shells of diatom algae, skeletons of radiolarians and spicules of sponges, which have retained their structure under the microscope, 3) tripolite-the same rock but with destroyed shells from various influences in geological epochs; denser and with larger impurities of sand and clay, and the silicic acid is in a more active modification; 4) opoka-a more compacted tripolite, with even larger impurities and with amorphous silica in the form of tiny opal balls. Artificial hydraulic additives include: 1) acid sintoff-a waste in the production of Al₂(SO₄)₃ from clays; 2) acid blast furnace slags (from smelting with charcoal), solidifying into an amorphous glassy mass having _ggMg_<i, i.e., less alkaline oxides than acidic ones; 3) basic blast furnace slags, obtained from smelting pig iron with coke, having-^-^г-.-ту^-,^-к- &gt; 1. easily crystallizing and brittle; 4) burnt clay; 5) ash of brown coals of the Moscow region. The addition of one or another filler changes the thermal conductivity of mortars and building materials depending on the properties of the filler. Diatomites go into mortars, into burnt brick, in the form of crushed stone into light concrete, into liquid glass, etc., everywhere significantly increasing the heat-insulating properties of building materials. Slags, added to mortars, concretes, bricks and used as backfill, also increase heat-insulating properties, but to a lesser extent. Since the amount of mortar in wall masonry reaches 30% of the total volume of the walls, and on the outer surface of the walls the area of the joints reaches 20%, the importance of choosing a mortar with lower thermal conductivity is clear. With the correct choice of mortar, the thermal conductivity of the wall is reduced by up to 20%. All these hydraulic additives, as well as pumice (loose, spongy, erupted volcanic rock), expanded clay (pumice-like burnt clay) and other inorganic and organic materials in a crushed state in the form of sand or crushed stone are used for making warm bricks, concretes, concrete blocks, i.e., economically more efficient new building materials. Of the old building materials for walls, wood meets sanitary requirements (its thermal conductivity is 4 times less than that of brick and 6-7 times less than that of concrete), however, different species of wood have different thermal conductivity, and along the trunk it is greater than across it. Hardwood species have greater water absorption, while conifers have the least.

Freshly cut wood contains from 27% to 48.6% moisture in the wood depending on the species, age of the tree, time of felling, etc., why wood must be dried before construction, which significantly reduces moisture; thus, after 2 years of storage under a canopy, the moisture content in oak decreases from 34.7% to 19.1% (air-dry), in pine from 39.7% to 17.9%, and in fir from 45.2% to 17.2%; without drying, the positive properties of wood are significantly less. From a technical point of view, wood possesses lightness, satisfactory strength, especially on tension, easy workability, but little hardness, easy abrasion, flammability, and easy rotting. Therefore, wooden buildings are not made multi-story and are not durable; sometimes wood is protected from rotting by various methods and made more fire-resistant. Close to wood in its positive properties stands ordinary building brick, possessing considerable porosity. Brick is made from clay or a mixture of clay and sand as a thinning additive; the mixture is kneaded, formed, and fired in kilns. With normal firing, red brick is most often obtained, with less firing, pink brick is obtained, and with overfiring, ironstone brick is obtained. The water absorption of red brick is 8-20%, the softening coefficient is significant, i.e., strength when wet is maintained; brick is strong, frost-resistant, and fire-resistant, rough, and therefore well bonded with a binding mortar, suitable for all kinds of strong building structures. Pink brick is more moisture-absorbent (up to 25%), less strong, frost-resistant, and is used for interior walls. Ironstone brick has opposite properties and is mainly used for foundations and sidewalks. Close to red brick is silicate brick from lime and quartz sand with steaming under pressure; used for walls, foundations. To increase porosity and reduce heat and sound conductivity, lightweight, or efficient, brick of various types is produced. This includes: 1) porous brick from clay with admixtures of combustible materials (sawdust, peat, coke dust, etc.), which burn out during firing and give small pores; used for load-bearing walls with small dynamic loads and for partitions; its drawback: strong air permeability and water absorption; 2) hollow brick with channels inside and hollow-porous brick, used for walls with even less load, light, warm, and soundproof; 3) tripoli brick, as well as clay-tripoli and clay-tripoli-porous brick, more porous, and therefore less heat-conducting, sound-absorbing, frost-resistant, light, and strong. Heavier brick is used for walls, lighter brick for partitions. From the combination of various binders with fillers, warm (light) concrete and a whole series of warm-concrete stones are obtained, of which the most commonly used are slag-concrete—cement-slag, lime-diatomite-slag, lime-slag, opoka-concrete (Portland cement and opoka), pumice-concrete (cement or lime and pumice sand), and silicatic-organics [lime-diatomite binder and more often peat-sphagnum and sawdust, but shavings (fibrolite), straw, bark and other waste can also be used]. Artificially porous (cellular) concretes should also be included among warm-concretes: gas-concrete and foam-concrete. In gas-concrete, pores are formed in place of small gas bubbles (H2, acetylene) from the chemical reaction of aluminum, zinc dust, etc., introduced into the concrete mass; fillers can also be introduced here. In foam-concrete, pores are formed mechanically from the introduction of small air bubbles into the concrete mass in the form of foam that does not settle until the concrete begins to set. For this, a foam additive is made to the binders and fillers from soap root and alginate thickener (infusion of marine algae in a solution of calcined soda) or from a mixture of soap solution of rosin in alkali and glue (bone or hide glue) solution. The properties of warm-concretes in terms of thermal conductivity and strength vary considerably depending on the properties and ratio of the ingredients contained in them; therefore, some warm-concretes are suitable for load-bearing walls, others for lightly loaded walls, and still others for interior partitions. Sanitary-technical properties of clay as a building material - see Clay. Slow drying, low water resistance and strength of clay have led to attempts to increase these properties in various ways. Only calcined clay with the introduction of light fillers or without them has entered into construction practice. Natural stones are less used for building walls and more often go for cladding buildings or as rubble stone for foundations. From old stone materials (granites, limestones and sandstones), walls are built only at the place of stone extraction due to the unprofitability of stone transportation; the same must be said about new stones (Armenian tuff, shell rock, andesite, beshtauite). Sanitary-technical properties of stones vary depending on their strength, thermal conductivity and porosity. Low-porous massive materials require a large thickness of walls to maintain a normal thermal regime, and natural ventilation through such walls is extremely difficult. Porous limestones and sandstones, as well as new stone materials, see as more porous, less heat-conducting, although less strong, meet sanitary requirements as wall building materials. Partitions inside buildings are usually built from lighter materials possessing the following properties: fire resistance, low sound conductivity, sufficient strength and heat capacity, easy nailability. For partitions of industrial buildings, light and hollow bricks and concretes and gas-concretes are used, for residential buildings - wood, gypsum-fiber boards, fibrolite, reed board, asbestos-fiber board, and various peat materials. Some of these materials, as well as straw board, shevelin, morozin, floemalite, cork boards, felt, etc., are thermal insulation materials for walls and ceilings. Gypsum-fiber boards depending on fillers are reed-gypsum (differential), gypsum-slag and gypsum-peat as solid and hollow, and alabaster sheet in the form of paper covered with a 1 cm layer of gypsum-slag; the sound conductivity of these building materials is significant, non-flammability, high water absorption, poor nailability. Used for partitions, ceiling linings, but are not thermal insulation materials. Thermal insulation materials have the purpose of insulating and thinning the load-bearing walls of buildings, replacing part of the brick or concrete with cheaper non-deficit materials with low thermal conductivity; these materials find wide application for the outer walls of frame houses (non-load-bearing walls), as well as for partitions, for insulating roofs, etc. Old insulators - cork boards, felt, etc. - at present due to the scarcity of raw materials are gradually going out of use and are being replaced by new non-deficit materials that give no worse results. These include primarily pressed fibrous materials. Fibrolite boards are made from wood shavings or wool, kenaf hurd, stems of grassy plants, which are pressed together with a binder: magnesia cement and drying at 90° (magnesia fibrolite - heraclite, tectone, fonitram, aubach, etc.) or lime-tripoli and steaming (lime-tripoli fibrolite). From straw and reed, boards (straw board and reed board) are made by pressing them and sewing with wire. Morozin is obtained by pressing chemically treated (boiling with soda) linen hurd. Shevelin is prepared in the form of sheets stitched with threads and consisting of paper on both sides with waste from linen production (noils, combings, tow) in the middle. From peat-sphagnum, i.e., the more surface and less decomposed layer of peat, are prepared: 1) peat filling - a loose-fibrous mass; 2) peat boards (peat-leum) - by pressing in liquid form, drying and thermal treatment until the beginning of dry distillation; 3) peat-fiber board from a layer of peat and 87% 880 glued plywood on both sides. Floemalite is made from spruce bark and tannin, mixed with sawdust or linen hurd; during treatment with water, centrifuging and steaming, boards are obtained. To insulating fillings, in addition to peat-sphagnum, belong wood sawdust alone or with 5% lime-powder and 5% gypsum (thermolite), tripoli (diatomite). The desire to obtain thermal insulation materials - silicatic-organics - without special binders due to the cementing properties of the organic substances themselves has led to the use of the most diverse industrial waste (branches, tree bark, sawdust, linen, hemp, kenaf hurd, sunflower, corn stalks, etc.) after grinding, rubbing, pressing and thermal treatment at a temperature almost of dry distillation. These include insorit (from straw), arbarit and masonite (from wood waste).

The sanitary-technical evaluation of thermal insulation materials is given in the table: Materials Coefficient of thermal conductivity Note Cork slab Fibrolite (HeracLite) Straw board Reed board Morozin Shevelin Peat board (peatoleum) Sphagnite Peat-fanero Floemalite Peat-fill Sawdust-fill Tripolite-fill 0.065 0.085-0.13 0.054 0.06-0.09 0.048-0.052 0.01 0.064 0.032 0.045 0.07 0.05-0.07 0.08 0.08 Smolders, scarce Fire-resistant, poor sound conductivity, high moisture content 100% Smolders, poor sound conductivity. In straw, rodents nest; in reed, house fungus grows Burns, high moisture content Burns, low moisture content Smolders, poor sound conductivity, affected by house fungus and rodents Smolders, poor sound conductivity, affected by house fungus Burns, damaged by water Burns, high moisture content, affected by house fungus Smolders, very high moisture content, affected by house fungus Burns, rodents nest Fire-resistant, high moisture content Roofing material should protect the building from atmospheric precipitation, moderate temperature influences, especially for attic spaces, be fire-resistant, low in moisture content, and not excessively heavy. Hygienic requirements here mainly come down to low thermal conductivity and poor permeability to water. Besides scarce roofing iron, which has high thermal conductivity, and excessively heavy cement tiles, lighter ceramic tiles, lath (flammable), and tar-cardboard, impregnated with coal tar with pitch and sprinkled with mica, are widely used as roofing material for lighter and temporary buildings. Among new roofing materials, the following should be mentioned: 1) natural stone-slate: shifer (asbestos) in the form of rectangular tiles; very durable (300-400 years), low in moisture content, but with significant thermal conductivity, 2) artificial slate (asbestos slate, asbestos board, etherite or terrphaserite): from cement and asbestos (up to 15%) in the form of tiles or sheets with better thermal insulation, nailed in place, 3) roofing felt (bituminized or asphalted cardboard), more durable than tar paper, 4) pergamino (cardboard, impregnated with petroleum asphalts) in the form of fabric, 5) tar-leather (like tar paper, but without sand), 6) tar-fanero (teroxyl), i.e., the connection of plywood with tar paper, 7) sphagnofiber-boards from peat-sphagnum and cement, 8) goodroberdan-plaiting from reed, coated with bitumen, as well as substances used for covering roofs of wood, concrete, etc.-iron tar, tar cement, the composition of which includes bitumen, pitch, lime, sulfur, etc. All new roofing materials meet hygienic requirements, and the use of one material or another depends more on its availability, the purpose of the building, and the technical requirements arising from this. To protect the building from water penetration from the soil through the foundation, various waterproofing materials are used, which are laid in the foundation above the level of the highest groundwater level. For less important buildings, layers of birch bark, tar paper, liquid glass are used; for more important ones-a layer of asphalt (see) or cement with 10% ceresite or cerolite, consisting of calcium oleate, which makes cement solutions waterproof. For flooring, various building materials are used, the choice of which depends on the requirements for floors of buildings of various purposes. Floors in residential buildings, according to hygienic requirements, should be: 1) impermeable to water, gases, and dust, 2) not forming dust, as well as cracks where dust can accumulate, 3) non-heat-conductive, 4) with poor sound conductivity, 5) smooth but not slippery, 6) easily cleanable, and 7) sufficiently elastic. Few materials satisfy all these requirements, while some materials do not meet them at all, such as earth, clay, concrete, asphalt, which produce a lot of dust, are cold, etc. Metlach tiles (from burned clay) although they provide a dust-free and easily kept clean floor, it is often cold, slippery, and inelastic; they are mainly used in corridors, bathrooms, toilets, etc. The best material for floors is wood in the form of oak parquet on a wooden subfloor or in the form of dry, smoothly planed floor boards without gaps, primed and painted. Wooden floors are warm, elastic, and meet other requirements, but spruce and linden are too soft and absorb water easily, so floors made of pine, oak, and beech are better as they are denser and less water-permeable. Often floors are covered with linoleum, which is a canvas of jute, kenaf, hemp, covered with a mass of oxidized technical oil, cork flour, resins, rosin, and mineral pigment. Linoleum, laid on wooden, asphalt, concrete, and other floors, ensures warmth, cleanliness, non-slipperiness, elasticity, and water impermeability of this floor. Magnesia floors (xylolith) are also good, when a concrete, brick, wooden, but not asphalt or clay floor is covered with a magnesia solution 1-2 cm thick. The composition of magnesite includes caustic magnesite in a solution of magnesium chloride with the addition of various fillers, most often wood shavings (1:2-1:4). A magnesia floor is applicable in dormitories, schools, hospitals, and industrial enterprises where there is no constant dampness; it is warm, clean, non-sound-conductive, waterproof, and elastic.

K. :Shashev.