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Building materials Main properties of building materials The properties of building materials are generally classified as chemical, physical, mechanical and special properties. During maintenance of building materials classification on effectual by such groups of various factors: 1) Mechanical factors: a) Various static and dynamic loads; b) Weight of construction structures; c) Mechanical work of wind; d) Mechanical work of ice; 2) Physical influences: a) Fluctuation of medium temperatures; b) Precipitation (rain); 3) Chemical factors: a) Aggressive water; b) Aggressive gas and other environment; Mostly complex of these factors influence building materials and constructions. Building materials (concrete, ceramic materials and oflens) as all physical bodies are characterized with the composition structure and properties. Building materials science is dealing with the composition and structures of materials, as will as how their factors are related to their properties or behaviors. In this context the composition of a building materials refers to it’s chemical make up (sudėtis), while structure includes atomic and electronic configurations, molecules and crystalline structures, microstructure (the appearance of internal structure under a microscope) and macrostructure (how the inter cell structure appears to the unnamed eye). Abilities of material to react to physical, chemical, mechanical environmental temperatures or it’s fluctuation, technology operations or another operate or groups of factors are properties of building materials. Certain mechanical and physical properties of building materials are strongly depended on structure. Structure can be any complex depending on a number of factors including: chemical composition and it’s uniformity in the material, the degree of mechanical work that a particular product receives and certain fluency treatments or processes that a materials may receive in order to achieve the desired properties. Understanding the relationship between these factors and the result mechanical or physical properties forms the basis for considering building materials as a modern science. Common physical properties 1. Actual density (savitasis tankis) or specific gravity. The actual density is the mass of a unit volume of dry homogeneous substance (without pores and voids): M – mass of substance in g or kg; Va – absolute volume of the substance in m3 or cm3; 2. Density (tūrio masė). Density is the mass of unit volume of a dry material in the natural state (voids and pores included): M – mass of a material in kg; V –volume of a material in natural state in m3; Density of a material may vary as a function of porosity and void content. 3. Bulk density (piltinis tankis) Lose materials (birios medžiagos) as sand, crashed stone, cement and often all characterized by their: M – mass of lose material in kg; V1 –volume of lose material in m3; The volume of these materials is consisted to include not only the pours in the grades of the material, but also the voids between them. The density of a material influents it’s physical-mechanical properties, such as strength and thermal conductivity. These characteristics all used to determine the thickness of the enclosing walls of heated buildings, the dimensions of building structures, to calculate the amount and the capacity of the required transportation means and handling, lifting equipment. Density also depends on porosity and the moisture content of a material. Porosity The porosity of materials is the relative volume of the pours it contains: The porosity expressed in percent will be: - Density of material in ; - Actual density in ; Pores are small cells in a material filled with air or water. Pores may be open or closed (firm and corse). Firm executes pores filled with air impact (suteikia) building materials god heat insulating properties, such as density, strength, water absorption, thermal conductivity, durability etc. Structures which are required to be very strong or impervious (nelaidžios vandeniui) are built of denser materials where as walls of buildings are generally made of substantially porous materials, which have good heat insulation properties. Void content (tuštumėtumas) Voids are empty spaces between grains of lose material (sand, crushed stone) or cavities in some of components such as hollow bricks and reinforced concrete panels. Void content or - both density of lose material; - density of grains of lose material; The void content of sand and crashed stone ranges from 35% - 45% and of hollow brick 15% - 50%. The properties of material with respect of affection of water Water absorption is the ability of building material to absorb and retain water. It’s described by the amount of water absorbed by an initially dry material fully immersed in water and is expressed in percent of mass (water absorption by mass) or of volume (water absorption by volume) of the dry material. The volume of water absorption in percent is determined by means of formula: Water absorption by volume: M1 – mass of the material in water natural state in kg; M – mass of the material in dry state; V – volume of the material in natural state; Water absorption is always less than the full or absolute porosity since some of the pours are closed. Water absorption by mass of very porous materials may exceed 100%. Saturation with water greatly effects the properties of materials: the density and heat conductivity of some goes up. Where as others materials clay tend to swell so that there between the particles are broken by penetrating molecules of water. When building materials are studied some coefficients must be known. The ratio of the water absorption Wt to porosity P of material is called as the coefficient of water saturation (prisotinimo vandeniu koeficientas): If kp is less then 0.8 the material is frost resistant. The ratio of the compressive strength of material saturated wit water (Rs) to that in dry state (Rd) is called the coefficient of softening (suminkštėjimo koeficientas): Materials with a coefficient of softening of 0.8 and thinner higher are referred to as water resisting materials. Moisture content (drėgmės) (Humidity (USA)) It’s a property of building material to release moisture to the surrounding medium. Materials placed in the air retain moisture as long as it in equilibrium with relative humidity of the air. Should the letter fall below the equilibrium value the materials will release moisture to the surrounding medium or dry. This property is reverse to water absorption. The rate of drying depends: 1) On the difference between the moisture of the material and the relative humidity of the air – the quarter the difference the more intensive is drying of the material; 2) The rate of drying is effective by the properties of the material itself and the natural of its porosity. Water repellence (atstumiančios, hidrofobinės) and materials with large pours their moisture more ready then fine pores and hydrophilic. Under natural conditions the water release for construction materials is described by the intensity of the water loss at a relative air humidity of 60% and temperature of 200C in 24h. There is always some water vapors in the atmosphere and therefore a moist material dries in the air not completely but to a certain degree called the equilibrium humidity, the material then being called air dry (orasausė). Under room conditions when the relative humidity of the air seldom exceed 60% woods has a moisture content of 8% - 10% and the exterior walls of building 4% - 6%. Variations in humidity are companied in many materials by changes in volume: the materials swell, when moisture content increases and shrink when it decreases. Repeated moisting and drying cause alternating stusses in the material of building structures and may result in cause of time in the loss of land bearing capacity. Hydroscopisity It’s a property of a material to absorb water vapor from air. It’s governed by air temperature and relative humidity, by the type of pores their number and size and finally by the nature of the substance involved. Surfaces of some materials called water retaining or hydrophilic evilly (godžiai) attract water, while surfaces of theirs known as water repellent or hydrophobic repulse water. With all their conditions being equal the hydroscopisity of material depends on its surface area including that of pores and capillarity channels. Materials of equal porosity but with smaller pores and capillary channels prove to be more hygroscopic than materials with large pores. Capillarity It’s the rising of fluid in tiay hair like space (capillaries). If to avoid capillary moisturing of construction it needs to isolate with layer of absolute dense hydro isolation materials (when brick walls from foundation are isolated with layer of tarred felt (tolis). Water permeability It’s described by the amount of water penetrating in one m2 at a constant pressure though 1 m2 of material being tested. Dense materials as steel, glass and bitumen most plastics are imperious to water. Frost resistant (atsparumas šalčiui) It’s the ability of water-saturated material to endure (išlaikyti) up rating freezing and thawing without visible signs of failure or considerable decrease of mechanical strength. Water contained inside material pores increased in volume by up to 9% - 10% in the process of freezing. The walls of water filled pores subjected to freezing experience considerable stusses and may even fail. Frost resistance of materials is determined by freezing water saturated specimens by temperature -150C and -170C and subsequently thawing them out. The frost resistance of material depends on its density and the degree of its saturation with water. Material is considered frost resistant when its strength decreases by not more than 15% – 25% and the loss in weight as a result of spalling does not exceed 5% after a prescribe number of freezing cycles. Materials are subdivided in to grades of frost resistance labeled F: F10, F15, F25, F35, F50, F75, F100, F200, F300, F400, F500. Under laboratory conditions specimens are frozen in refrigerating chambers. One or two freezing cycles in the chamber are equivalent to 3 or 5 years of atmospheric exposure. There is also faster testing method in which specimen are soaked (įmerkiami) in a saturated in 1000C-1100C of Na2SO4 solution. Crystals of decahydryer Na2SO4 formed inside the pours of the atom press against the walls of the pours even stronger then the freezing water. This kind of test is particularly severe. One cycle of testing in a solution in Na2SO4 is equivalent to 5 – 10 or even 20 cycles of direct freezing tests. The properties of materials with Respect to action of heat Heat conductivity is a property of a material to conduct heat. The heat conductivity Of material is (quantictivly) evaluated by a coefficient of heat conductivity λ, which is equal to the quantity of heat flowing in 1h through a specimen of 1 m2 and 1m of thickness, when the temperature difference between it’s opposite and parallel flat surfaces is -10C: Q – quantity of heat energy in J A – thickness of materials in m A – square of surface in m2 T – time in s Thermal resistance The thermal resistance may also characterize the heat conductivity of a material, which is equivalent of heat conductivity The heat conductivity of material depends on the number of factors: nature of a material, it’s structure, porosity, characters of pores, humidity and (min) temperature of which the heat exchange take place. Materials with closed pores have lower heat conductivity than with communicating pores. Fine pour materials have lower heat conductivity than these with large pores. Then density decreases heat conductivity drops, moist materials have higher heat conductivity then dry ones. The coefficient of heat conductivity is the basis for subdividing various construction materials into heat – insulating l (0.082-0.210), (>0.210) structural categories. Coefficients of heat conductivity of some building materials are: Granite – 2,9 – 3,3 Steel – 58 Heavy concrete – 1 – 1.6 Common clay brick – 0.44 – 0.9 Water – 0.58 Light weight concrete – 0.35 – 0.8 Heat insulating concrete – 0.08 – 0.3 Foam glass – 0.06 – 0.08 Rock (mineral) wool – 0.046 – 0.09 Air in pores – 0.023 Ice – 2 Heat conductivity is greatly affected by humidity. Heat conductivity of water is 25 higher then heat conductivity of air. Heat conductivity Is major importance for materials used to build walls of heated buildings for various thermal units as boilers heat supply mains etc. The l directly governs the cost of heating which is a major factor in the evaluating the economic effectiveness of walls in dwelling houses. Heat capacity (šiluminė talpa) It’s ability of building materials to absorb or give of heat, the heat capacity is described by specific heat which is quantity of heat required to heat in kg of building materials by 10C. It may be determined by the formula: Q – quantity of heat required to heat a material from temperature T1 to T2 T2 – T1 difference between the temperatures of material pores and of the heating Heat capacity is of vital importance when heat accumulations is to be taken into account, so as to prevent temperature variations caused by outside temperature fluctuations, in calavation of furnaces. The specific heat of coefficient of heat capacity of : Stone materials – 0.755 – 0.925; Wooden materials – 2.38 – 2.72; Heavy concrete – 0.8 – 0.9; Steel – 0.46. Spalling resistance (sutrukinejimas atsisluoksniuojant) (terminis atsparumas) It’s characterized by it’s ability endure a certain number of cycles of sharp temperature variations without failing. Spalling resistance depends on the degree of homogeneity of a material and the coefficient of linear expansion a of it’s constituents. The lower the letter values, the higher are spalling resistance of building materials Concrete a=(10-14)10-6 Steel a=(11-11.9)10-6 Glass and granite may be mentioned as examples of materials with pore spalling resistance. Fire resistance (patvarumas ugnyje) It’s the ability of a material to resist the action of high temperature without loosing it’s load heating capacity or without substantial deformation. This property is tested by the combined actions of high temperature and water. By their fire resistance building materials are subdivided into such groups: 1. Non – combustible (as clay, bricks tiles, etc) (nedegios) 2. Fire – resistive (xylilite, asphalt concrete) (sunkiai degios) 3. Combustible (paper, ruberoid, timber) (degios). Refractorious (atsparios ugniai) It’s ability of a material to withstand prolonged action of high temperature without melting or loosing shape. There are three varieties of a material: 1. Refractory (atsparios) – capable of resisting prolonged action of temperature 15800C and higher, chamote, dinas, etc; 2. High melting materials (sunkiai lydžios) with stand temperatures from 13500C-15800C, clay, bricks for façade; 3. Low melting materials 13500C common clay bricks. Chemical properties Chemical resistance is the ability of building materials to withstand the action of acids, alkalies, salt solutions and gasses. Most resistive the acids and alkalies are ceramic materials, manufactured items and plastic articles (dirbiniai). Natural stone materials such as limestone, marble, dolomite are even byuvuk acids. The resistance of wood to the action of acids and alkalies is low. Bitumen disintegrates rapidly when placed in contact with concentrated alaked lignors. Sanitary facilities, sewer pipes and hydectic engineering installations are most frequently attached by corrosive liquids and gasses and in some cases by sea water which contains a large quantity of dissolved salts. Special properties of Building material Workability (apdorojamumas). It’s the amenability (pasklusnumas) of materials to working. This property has some varieties polish ability, dense-ability, spread-ability (klojingumas), formation, cover-ability, joining and transport-ability. For example workability of concrete mix is the case with which concrete can be planed. Wet concretes are workable but weak. This workability can be measured by the slump test. Durability It’s the property of building materials to resist the combined action of atmospheric and their factors, such as variations in humidity and temperature, attack by gasses contained in the air and salt dissolved in water or the combination of water test, insulation (saulės). The less of mechanical strength may be due cracks, to exchange reactions with substances in the surrounding mechanics and also to changes in the state of material (recristilyction and others). Aging It’s an alteration in the strength properties of the building materials with time. Usually it may be a strengthening or hardening such as with durahiumine after heat treatment, mildotel after cold working, concrete throughout it’s life or plywood (fauna) a few days it has been glued. Age hardening implies embritlement. Weathering resistance (atsparumas atmosferiniams reiškiniams) It’s an ability of material to endurance repeated moistening and drying over prolonged periods of time without either suffering considerable deformation or loosing mechanical strength. Materials behaved differently when exposed to varying humidity; concrete tensed to fall because its cement stone shrinks in a process of drying while the aggregates suffins practically as volumetric changes. This causes tensile stresses in cement stone which contract and teas itself if aggregate. Wood under goes alternating resistance of materials may be exchanged by means of hydrophobic additives, which make the materials water repellent. Atomic properties Sound is a mechanical disturbance in a elastic medium (in air, water, solid body). The quantity of energy carried by sound wave per 1s through an area of 1cm2 normal direction of it’s travel is known as sound intensity. A prolonged action of audible (girdimas), in particular that of high pitch sound is detrimental to human health. Sound energy that falls upon an exterior structure as wall, floor etc. Is partly reflected, absorbed and partly passes through the structure with the effect that sound is transmitted to its other side. The ability of material to pass sound is called it’s sound transmission and it’s reapoard (1 equivalent) is called proofing. Sound proofing of a wall material is evaluated by difference in sound levels on both sides of the wall and expressed in decibels. Permeability of gas And vapor Gas permeability is the capacity of building materials to let through gas under difference of pressure. For building materials the vapor is very dangerous. After condensation water can wash some components and destroy a material. Gas and water permeability mostly depends on structure. Permeability to nuclear Decay radiation Among the great variety of physical properties required of materials intended for atomic industry a major one is the ability to arrest gamma rays and neutron fluxes which are dangerous for living organisms. For this reasons some parts of installations at atomic industry plants and research institutes are required to serve as biological shields (apsauga). Degree of absorption of radioactive flux depends on the thickness of the shield, the nature of the radiation and the properties of the shield materials. Protection against neutron radiation is provided by materials containing a large amount of combined water and against gamma rays by high density materials as had, extra heavy concrete, etc. A flux of neutrons penetrating the concrete may be lessened by introducing special admixtures as: boron, cadmium, lithium (B, Cd, Li). Mechanical properties of building materials Mechanical properties are characterized by the ability of building materials to resist all external actions involving the application of force. Ultimate strength (stiprumo riba) And safety factor of building materials Strength is the ability of building materials to resist failure under the action of stresses caused by a load. The strength of building materials is described by their ultimate strength which is stress corresponding to the load destructive a specimen of the material. In building materials stresses are not allowed to exceed a certain part of their ultimate strength, this providing a safety factor. The values of the safety factor are specified by design standards. Compressive, tensile and Bending strength of building materials Compressive and tensile strength is computed by the aid of the formula: P – breaking load F – area The bending strength is determined with the aid of following formulas: 1) For single concentrated load and the bar of rectangular cross-section 2) For two equal loads located symmetrically with respect to the bar axis The strength of material is affected not only by the shape and the size of the specimen, but also by the character of it’s surface, the rate of load application also by its structure, density, porosity, moisture content direction of load application. Novel techniques, which allow non-destructive Testing of building materials for strength The building practice has been enriched (praturtintas) by novel techniques which allow non-destructive testing of specimens or elements of construction for strength, these techniques can be used to test items (dirbtiniai) either in the process of their manufacture or directly at construction sights after there are mounted. The ultrasonic (acoustic) and radioactive isotope methods are the best known. Such methods are based on the principle that physical properties velocity of ultrasonic waves or the propagation time of shock waves required to penetrate the material and also by the frequency by natural assignations of the material and their attenuation (susilpnėjimas) which depends on the material density and strength. Method of radioactive isotopes is rather similar but more dangerous. The principle is the same as in the case in ultrasonic waves. The strength of concrete in a construction may be determined by non-destructive mechanical techniques as by means of a device hose work is based on a strength character which correspond to the depth of an indentation (žymė) made in concrete by a ball or to the high of respond of a pendulum or bar. Hardness It’s the ability of building materials to resist penetration by a hard body. Hardness may be determined by a number of methods. Hardness of stone materials is found with the aid of Mohr’s scale of hardness, which is a list of ten minerals arranging in the order of increasing hardness. Hardness of metals and plastics is finding by indentation of a steel ball or some or pyramid. Abrasion resistant (diliumas) It’s characterized by the loss its initial mass referred to 1m2 of a surface and being abraded (trinamas), Tested for abrasion resistance are materials attended to floors, roadway surfaces, stair treads and etc. Wear resistance It’s the failure of material under the combined action of abrasion and impacts. Wear resitance is evaluated by the loss in mass expressed in %. Subjected to wear are road and street surfaces and railway ballast. Impact strength It’s important in building materials for floor and road, street surfaces. Materials are tested for impact strength in a special impact-testing machine. The ultimate strength of building materials subjected is impact is described by the quantity of work required to cause the failure of a specimen per its unit volume. Elasticity (standumas, tamprumas) It’s the ability of material to resist its initial form and dimensions after the load is removed. Plasticity It’s the ability of building materials to change its shape under load without cracking and to retain this shape after the load is removed. Plastic materials may be: hot bitumen, clay grout (molio tešla (dough)), copper, steel, etc. Brittleness Building materials may be divided into plastic and brittle. Brittle materials fail suddenly without any considerable deformations preceding the failure. Rock materials are generally brittle. Brittle building materials have adegnae (pakankamą) to kompussion only and a pure resistance to tension, bending and impacts. Building materials from natural rock Common information and classification of rocks Natural rock or stone is one of the oldest building materials that is known. The Earth’s crust is composed of rocks. Rock is a mineral mass of more or less uniform composition consisting of single (monomineralic) or of several (polymineralic) minerals. A mineral is a natural body homogenous in chemical composition and physical properties. Minerals are products of physical and chemical processes occurring in Earth’s crust. Depending on its geological origin, rock can be divided in 3 general categories: 1. Igneous (magninės) 2. Sedimentary 3. Metamorphic Igneous rock was formed as the result of the cooling of molten matter. Sedimentary rock was formed by depositing minerals at the bottom of water body or depositing them on the Earth’s surface formed sedimentary rock. The latter took place when water flowed to the surface from the Earth’s interior bringing minerals, which were deposited as the water evaporated. Metamorphic rocks have been changed from their original structure by the action of extreme pressure, heat, moisture or various combinations of these forces. Basic rock-forming minerals The properties of rocks as building materials are governed to a great degree by their mineralogical composition. Minerals are falling in such groups: 1. Quartz’s group – quartz and opal 2. Aluminum silicates – feldspars, kaolin, micas 3. Ferrous-magnesia – hornblende, augite, olivine, pyroxene and others. 4. Carbonates – these chief minerals of sedimentary rocks are calcite, magnetite, dolomite 5. Sulphates – gypsum and anhydrite Igneous rocks Among the igneous rocks distinction is made between the massive deep-seated rocks, it effusive rocks and fragmental varieties. The chief representatives of massive deep-seated rocks are granites, syenites, diorites, and gabbros. Granite is the most widely found igneous origin deep-seated rock composed of quartz, feldspar, hornblende, and mica. The color of granite depends on main constituent and the presence of dark minerals. It is found in red, pink, yellow, green, blue, white, black and brown varieties. The density of granite is 2600kg/m3. Its compressive strength is 100 – 300 mpa, tensile strength 1/40 – 1/60 of the compressive strength. Wm = 0.002 ÷ 0.2%. High mechanical strength, weathering and frost resistance predetermine high building quality of granite and building materials made of it. Granite has a wide variety of uses in building for facing slabs, staircases, floors, curb and paving stones, crushed stone, flag stone, ashlars or rubble veneers. Other uses of granite include facings for bridges, riprap, and mosaic – type facing by setting small cut or broken pieces into the face of a precast concrete panel. It is also used in the construction of hydraulic engineering installations and for various monuments, etc. Syenite. Its structure is similar to that of granite but it consists mostly of feldspar. Syenite is used for the same purpose as granite. Diorites are used for road construction as facing slabs and for broken stone. Diorite in color can be from green darkish to blackish. Gabbros. Its color ranges from gray or green to black. It is used for hydraulic engineering and other kinds of installation in the form of rubble facing slabs etc. Labradorite, also belonging to gabbros group, is used as facing material because of its beautiful color (gray, green, green-grayish, or dark with a blue lustre). Effusive rocks are of the same chemical and mineralogical composition as the deep-seated rocks and have approximately the same physical and mechanical properties. Representatives are such: quartz porphyry, porphyrite, andesyte, diabaze (it is an analogy of gabbros), and basalt. Fragmental rocks fall into loose (pumice, volcanic ash, volcanic sand and cemented (volcanic tuffs, volcanic lava, tuff lava, trass)) varieties. They are used as aggregates for light weight concretes (pumice), as heat insulating material and as active mineral admixture to lime and cement. Tuff is used also as aggregate for lightweight concretes and mortars for large wall slabs. It is also excellent decorative and frost resistant material and is used as a facing material for facades of buildings. Sedimentary rocks Sedimentary rocks is a result of deterioration of massive magnetic or fragmental rocks, the precipitation of salts in drying water basins (chemical deposits) and the accumulation of plant or animal remains (organogenous rocks). Mechanical deposits Products by disintegration were transported by winds, by water streams over big distances and the settled, thus giving origin to clays, sands, crushed stone and gravels from massive rocks. Sand is a loose mixture of grains of various rocks ranging in size from 0.14-to 5 mm. According to origin sands fall into rock, river, sea, dune, and lake varieties. Gravel is formed of rounded off stones which measures range from 5 to 70 mm. Cobble stones (rieduliai) – rounded stones, often used for paving. Clay - under the action of water and carbon dioxide of the air, feldspar form a mineral called kadinite, which is the main constituent of clay. Cemented mechanical sedimentary rocks Mechanical deposits of sedimentary rocks are divided into sand stones (smiltainiai), conglomerates and breccias. Sand stone is a sedimentary class of stone made up of quartz grains cemented together. Conglomerates are rocks consisting of cemented grains of gravel. Rocks consisting of cemented stone fragments are called breccias. Conglomerates and breccias are used as crushed stone for concretes as well as piece of stones and facing slabs. Chemical deposits Gypsum (caso4 ·2H2O). Its density is 2 ÷ 2.3 g/cm3. Rc ~ 20 MPa. It is used for the manufacture of an air-setting binder (construction gypsum), for the manufacture of portland cement and as artificial marble for interiors of building. Anhydrite (caso4) is used for the manufacture of anhydrite cement and for facing. Magnesite mgco3 is a raw material for the manufacture of refractory and for air-setting binding materials (caustic magnesite). Dolomite consists mainly of the mineral dolomite (caco3∙mgco3) with some admixtures. It is the source material for crushed stone, facing slabs, refractory and binding materials. Lime tuffs have formed in the process of separation of calcium carbonate caco3 from calcium carbonate dissolved in water. They are used as raw materials for production of lime and cement, as piece stones, as aggregates for lightweight concretes and as facing material. Organic rocks The comprise limestone, shell limestone, marl, chalk, diatomite and tripoli. Limestone has formed from animal and plant remains in water basins (or as product of chemical deposits). It is used for the manufacture of crushed stone, facing slabs and architectural items and for the production of lime and portland cement. Marl (mergelis) is a rock containing some quantities of lime and clay. Clay’s constituent is 20÷60%. Marl is used for the manufacture of binding materials. Shell limestone is a porous rock. It is used for the manufacture of wall stones and blocks and as aggregate for lightweight concrete. Chalk is a rock composed of almost pure calcium carbonate. It is used as a white pigment and in the manufacture of putty (glaistas), lime, portland cement and glass. Diatomite is a poorly cemented very porous siliceous rock formed of shells of diatom algae and partly of skeletons of living organisms. They are used for the manufacture of heat insulation materials, lightweight brick and as active mineral admixture in hydraulic-setting materials. Tripoli is lightweight clay-like rock carrying amorphous silica in the form of fine opal balls. It is used for the same purposes as diatomite. One of sorts of tripoli is opoka, which has been found in Stoniškės quarry. It is used as additional material for manufacture of portland cement. Metamorphic rocks Gneisses is crystalline rock formed of granites, syanites, diorites, and are shelly in structure. It is used as facing slabs, rubble stone for foundations and walls of non-heated buildings, paving stones for sidewalks. Clay shales are metamorphic rock formed by the metamorphosis f clays and shales. Common uses include roofing files, flooring, wall facing windowsills and others. Clay shales are weather resistant and durable. Marble. Limestone and dolomite have been recrystallized to form marble. The colors of marble are ranged from pure through all shades of gray to black, including violet, red, yellow, pink and green. Rc = 100 ÷ 300 mpa. Itranges hardness is relatively low – from 3 to 3.5 according to Mohr’s scale. Density is 2900 – 3000 kg/m3. It can be readily sawn and polished. Marble is used mainly for wall or column facing and for flooring. Its pure chemical resistance against sulphureous gases and atmospheric moisture makes it unsuitable for external application. Quartzites are metamorphic varieties of siliceous sand stones. It is a stone, which is harder than some granite. Their Rc = 150 ÷ 340 mpa, they are weather resistant. They are suitable for use as facing of building bridge piers and manufacture of silica refractory items (Dinas). It is also available for treads, mantels (atbrailos), hearts etc. Stone mining and working Operations involved in obtaining minerals are called mining. Rocks that are suitable for manufacture of stone materials are called useful minerals. Rocks that are accomplished of minerals and not used for manufacturing purposes are referred to waste rock. Voids formed in the process of mining are termed excavations, and the mined deposits-quarries. Quarry is an open peat from which building stone, sand, gravel, mineral is taken. Natural stone materials are mined in quarries by the use of excavators, hydromechanisation techniques, stone cutting, and machines for sawing rock. Sand and gravel are classified at the quarries into 2 or more size fractions. Rock is crushed, screened and concentrated at crushing-and-screening plants. Massive igneous rocks are mined as a rule by blating. Power shovels, etc. are used to separate lumps of rocks. Holes are drilled close together at right angles to the bending planes or joint planes or both. Wedges are driven into the holes to split the rock along the drilled line. Finer and softer rocks are mined by sawing massive rock with aid of cutting machines or by the mechanical saws. Stones are worked by mechanical means by specialized plants. Machine finishes include a planer finish shaping, carborundum finish, rubbed (poliravimas) finish and various other machine tool finishes. A variety of hand finishes are also applicable to cut stone. They include the bush-hammer, hand-rubbed and another finishes. By the character of worked surfaces split stones are subdivided into some types of finish – “rock” ribbed grooved (vagotas) and pointed. Items from slag melts Molten slag are used to manufacture floor blocks for industrial plants, facing tiles for corrosive media, tubing for supporting drives in mines, light weight materials (thermosite, slag wool, etc). Thermo-site (slag, pumice) is a cellular material obtained by expanding molten slag as it is being rapidly cooled, r is 300-1100 kg/m3.Expanded thermo-site is a good aggregate for the manufacture of lightweight concrete. Slag wool is a material constituted by fine threads obtained from molten blast furnace slags (or other mineral melts). Temperature of manufacture is 1200-1400° C, r - 250 – 300 kg/m3, l - 0,05 w/m° C. Items from such wool are widely used as sound-and-heat insulating materials. Ceramic building materials Common information and classification Ceramic building materials are manufactured from clay compositions by molding and intermediate drying of items and sub segment burning. Good technical properties, wide range of product, high strength, durability, reasonable cost of ceramic item underlay their wide use in various subassemblies of buildings and installations (statiniai) such as walls, wall and floor facing materials, heating units sewer pipes, light porous aggregate of concretes, etc. Raw materials for manufacture of ceramic items Clay and its properties Clay result from weathering of eruptive desinfregration feldspathic rocks. Purest clays consisting mainly of kaolinite and are called kaolin. Clays after contain such minerals as quarter nice, folds paths, calcite, magnetite, etc. Clay is capable to mix with water and form a plastic viscous mass that on drying retains the shape and after burning acquires the strength of stone. By resistance to high temperatures clay fall into 3 groups: 1) Refractory (ugniai atsparūs) have a refractors hot below 15800C; 2) High molting from 13500C-15800C; 3) Low molting lower than 13500C; Clays consist of several oxides aluminum, Al2O3, Fe2O3, CaO, Na2O, MgO, K2O few and chemically bonded waters and organic impurities. Ceramic properties of clays are characterized by plasticity, echelon, and cohesiveness and their response to drying and high temperatures, granulometric composition (grains are less then 0.005mm are clay fractures). Some ceramic plants lack in natural rough materials suitable for the manufacture of corresponding items. Such materials call for the introduction of various additives. The addition of leaner (liesų) substances as quartz, slag, shemote and others to plastic clays minimizes the shrinkage during drying and burning. Light weight ceramic items of inhaust porosity are obtain by mixing the raw mass with various performing agent as clay nearl, chock, ground dolomite, etc. and materials that burn out during firing operation as saw dust (pjuvenas), pulverized (susmulkintos) coke, peat powder and alike. The burning temperature of some items may be lowered by adding to clay fluxes (fliusai) such as: feldspaths, ison ores, silica, etc. The plasticity of the moulding clay mass may be inhaled by introducing in the mix of 0,1-0,3 of surface active surfactants. Colored ceramic items are obtained by tinting the clay mix with various oxides of metals as irons, cobalt, chromium, etc. Glaze. Glazing makes the items waterproof and give them an excellent decorative appearance. Glazes are available in different composition: translucent and opaque (nepermatomas), glaized and lusterless, white and colored, high and low heat varieties. High heat glazes are used as coats for porcelain items and are composed of kaolin, quarter and florspaths, and the low heat glazes of radial fusible days with admixtures of chock and iron oxides. They serve as coating material for facing brick, roof tiles and sewage pipes. Colored glazes are obtained by introducing coloring oxides or salts of metals. Glazes suspensions are used in form of which are spuad over ceramic items or applied with a brush. The items are glazed then and burned again. Engobe (angobas). A new efficient method of obtained facing brick and ceramic stones by engobing has been investigating. The surface of facing bricks is colored by specially developed variously colored frost resistant engobe composition. Engobes are manufactured from low heat clay and sand. This composition is mixed with coloring agents. Engobing consist of opsaying a thin colored facing larger are freshly moulded or dry brick to enhance or to wash when burned the structure and the color of ceramic material. General production slow sheet for ceramic building materials The basic production steps for all ceramic building materials are: 1) Mining of raw materials; 2) Preparation of raw past; 3) Moulding of items; 4) Drying of items; 5) Burning of items; 6) Finishing of items (trimming, glazing, etc.); 7) Packing. Raw materials are carried by the open the pit method with the aid of power shovels (ekskavatoriais). Preparation of raw materials involves disintegration of clay, removal or grind of large inclusions, mixing with admixtures and water. Ceramic mass is prepared by the stiff-nud (pussausis) method, moisture content (8%-12%), soft-nud (plastinis) (20%-25%) and slip casting methods (till 60%). An essential intermediate operation in the manufactures of ceramic items by the soft-nud is drying (if a high moist green is burned directly after molding it will crack). Artificial drying effected in bath – type box dryers or continuous tunnel dryers. Burning is the final stage in the manufacture of ceramic items. Green items are changed into furnace at a moisture content 8%-12%. Bricks are burned in circular or tunnel cilus (krosnyse), a circular one being a closed burning channel divided into chambers. The heating of items in the range 00-1500 C removes their hygroscopic moisture. The processes occurring in the 5000-8000 C range are the dehydration of the day mineral and removal of the chemically bound of water. A further rise in temperature 8000C – max value involves the breaking up of the clay mineral crystalline lattice and changes the structure of the item. It’s possible to burn bricks in 6-8 hours. Items of low melting clays are burned at temperatures between 9500-11000 C until they become stone-like. Classification of ceramic items According to the applications ceramic building materials and items are classified into such main groups: 1) Wall materials: common clay bricks, perforated plastic moulded ceramic stones (blokeliai) and light weight bricks; 2) Bricks and clay building stones for purposes: curved clay bricks; stones for sewage installations, bricks for roads and street surfaces; 3) Hollow ceramic items for floors: stones for close-ribbed floors, stones for uniforced ceramic beans, sub-flooring stones (juodgrindims). These will be filter between beaurs; 4) Ceramic items for façade decoration: glazed or non-glazed varieties subdivided into facing bricks and ceramic stones floor, ceramics tiles, ceramic plates for facades and window – cill – drip stones; 5) Ceramic items for interior decoration; tiles for facing walls, large floor tiles and mosaic floor tiles; 6) Roof materials: common clay roof tiles (for covering stopes of roofs, ridge tiles and riks, valley tiles and tiles for closing rows of tiles and special tiles); 7) Sewer and drainage ceramic pipes; 8) Acid-resistant ceramic shaped tiles for special purposes, ceramic acid- resistant pipes and companion shaped; 9) Sanitary ceramic items: faience, semi-porcelain (which differ in degree of calcing and in porosity); 10) Ceramsite: as aggregate for light weight concretes and as heat insulting materials, agloporite (also for light weight concrete and heat insulation); 11) Refractory materials: silicious, alliums–silicate (as chamotte), magnesium, chrome and carbonations varieties. Properties of clay bricks and ceramic stones Common clay bricks are available in ordinary size 250x120x65mm and module sizes 250x120x88mm. The quality of bricks should satisfy the requirements of the state standard. The module brick with molded voids is not more than 4 kg in mass, there are 7 grades of bricks: 75, 100, 125, 150, 200, 250, 300 kgf/cm2 which indicates respective compressive strength. Bricks should also met their bending strength: 1.5; 2.2; 2.5; 2.8; 3.4; 4.0; 4.4 MPa respectively. Brick dimensions are as follows: length 250±4mm; 120±3mm; 88 or 65±3mm, curving of the edges and the fans should not exceed 3mm. Individual small spalls of the edges and the angles should not be greater then 15mm along the edge and not more than 2 spalls are allowed per brick. Line undusions under burning or over burning are not tolerated. Color of burned brick should correspond to that of a standard brick. It’s necessary that bricks of grades 150 and higher should have a water absorption wm³6%, of other grades wm³8%. By their first resistance bricks are subdivided into 4 grades: F15, F25, F35, F50 They should be molted in vacuum anger brick machine, fixed with special devices (punches – skylamušis) for making hoks (voids) in the brick. Size is the same as few common bricks. Grades 75, 100, 125, 150. Density 1000 – 1450 kg/m3; wm³6%; F³15. Light weight building bricks They are module and burned as artificial from diatomite’s (spec. Minerals) or Tripoli with admixtures of clay or a combination of clay and burning-out admixtures. Size 250x120x88, density 700-1000 kg/m3, Rc=5; 7.5; 10 MPa, F³10. Ceramic stones or blocks They have smooth or filled surfaces and through or closed voids. Dimensions 250¸280x120¸190x130¸288mm, r=1300-1450kg/m3, wm=6%; F³15, grades 75, 100, 125, 150. They are used for same prepossess as bricks. Curved clay bricks They are used for brick work of industrial chimneys and for vining piper when they are heated by flow gasses to a temperature not higher then 7000C. Grades 100, 125, 150, wm=8%; F³15. Clinker’s bricks for roads And street surfaces They are artificial stone modules from high-heat clays and burned until caked, but not glazed. A single size 220x100x65mm, grades 1000, 600, 400, wm=2, 4, 6%; F³100, 50, 30. They are abrasion resistance. Number of impact respectively ³ 16, 12, 8. Paper – mounted glazed and unglazed Ceramic ties for facades They are small size, thin, variously around tiles glued upon a paper sheet to form a mosaic. They are manufactured in a range more than 30 types and sizes. Width size measuring from 20 – 125mm, H= 4mm, F³15. The glue should off readily after the facing is completed. Ceramic slaks for facades Are available in common and angle types. Common slaks are 120 – 240mm length 65 – 140mm height and 6-17mm thick. Angle 65 – 190mm and 8 – 17 mm thick. Ceramic tiles for interior facing They are divided into wall, large floor tiles and mosaic floor varieties. Wall tiles are divided into majolica and faience kinds according to the raw materials used. Majolica tiles are manufactured from low-heat clays to which up to 20% caco4 is added in the form of chock. Their face side is glazed and the back side fluted to improve adhesion to the wall surface. Tiles are glazed and then burned again. The tiles have a white or slightly colored shell whose face is coated with white or colored transhunt or dead clays, their bad side is generally rifled. Both verities are manufactured L150, W 25, 50, 75, 150 thickness 6, 10, 12mm, wm£16%. Such tiles are used for face walls of kitchens, bathrooms, laundries, etc. Ceramic floor tiles They must be durable and impervious to coater, resist well abrasions and wash readily. They are used for floors of public building halls, bath-houses, laundries, sanitary closets, chemical plants etc. These tiles are available with side measuring from 500 – 150mm and thickness 10 – 13mm, wm£4%. Their resistance to absorption should be high (loss in mass should not exceed 0,1g per 1cm2) for floors of other premises. Mosaic floor tiles are manufactured in squares with sides 23 and 48 mm and thickness of 6 and 8mm. Very often they have rectangular shape. Wm£3-4. Burnins tiles are then placed into dies (matrica) and carbdound is glued over them and washed off one the floors in bathrooms, bathhouses, swimming pools and public premises, hallways, underground railways stations etc. Clay roof tiles They are manufactured from clay with and without admixtures. They are such main types: stamped, valley, flat, ribbon and ridge, also special tiles as end-tiles (halves, jambs) for closing causes. Roof tiles should be well burned, uniformly colored, have an even and smooth surfaces, be sufficiently strong (breaking loud out less then 70kg of forces), impervious to water and frost resistant, F³25. Sewer and drainage ceramic pipes Sever pipes are made from high heat of refractory clays without admixtures (finely ground chamote or quarter sand) in cylindrical shapes and bell-double shaped ends. Dried and finished pipes are coated on the outside and on the inside with clay glaze then burned at temperatures 12500C - 13000C (wm£8% for 1st grade and wm£11% for 2nd grade). The pipes must withstand hydraulic pressures not less 0.2 MPa. They are available in diameter from 150 to 600mm and in length from 800 – 1200mm. Ceramic draining pipes on the outside can be protected by glazing. They are manufactured with or without bell shaped ends. The reason trend has been to manufacture plane draining pipes. The pipes being joined together and protecting against mud plugging by ceramic unions. Water enters the pipes through the joints they are manufactured 25 – 250mm in diameter, in length 333 – 335mm and sometimes up to 500mm. F³15. Sanitary ceramic items are manufactured mainly from wide burning refractory clays, kaolines quartz. There are 3 groups of such ceramic: faience, semi-porcelain and porcelain which differs in degree of caking and as a consequence in porosity. Items are generally molded by casting into gypsum molds and charged into drying chambers, then coated with raw glazing and burned at temperature 12500C - 13000C in buch-type or continues shilus. Solid faience is used mainly for manufacturer toilet bowless, wash-basins, toilet-tanks and bath tubs. Items are glazed since unglazed faience is water permeable. Porcelain is used to manufacture insulator for power transition lines, chemical laboratory vessels and so on. Ceramsite It’s a light-weight porous material of cellular structure whit closed pores. It’s used mainly as aggregate for light-weight concerts and as heat insulting material. It’s manufactured from low heat clays. Pulverized (susmulkintas) coal, peat crumbs or similar materials are added to clay. In the process of burning the material soften and water vapors cause the semi-liquid mass to expend and form pores in the clay. Ceramsite gravel is burned for 30 – 60 min in rotary heater (krosnis) 20 – 50 m long, 1.5 – 3.5 in diameter and temperature of 13000C. After coating is crumbed to various sizes fractions and stores in silos. Ceramsite gravel is available in prelist 5 – 40mm in diameter. Grains smaller than 5mm being called ceramsite sand by its density gravel is divided into grades: 250, 300, 350, 400, 500, 600, 800, 1000. Agloporite The raw materials for manufacture of agloporite all clays (loam, launay sand, argillite-baltes, clay scale (skalūnas)) and industrial waste such as burn rock, fuel cinder (pelenai), ash feour power stations and other. Size of granules from 5 – 20mm. Usage is the same as ceramsite. Refractory materials Most widely used all the siliceous, alum-silicate, magnesium, chromius and carbonous vavilies (to read independly). Glass and other building materials from mineral melts Classification Materials in items produced from mineral melts may be divided according to their source material into glasses, cast stones, slags, sitals (sitalai), slag sitals. Raw materials for glass The source materials for the manufacture of structural sheet glass are: quartz sand, sodium sulfate, limestone, dolomite and other substances. Manufacture of structural glass, it consist of the following main questions: the preparation of consistent materials involves drying sand and cleaning it of admixtures impurities, crushing and drying (chock) dolomite, pulverizing coal, proportioning and mixing the ingredients. A change is melted in special continues tank or batch. The source charge is processed at 11000C - 12000C until all the impurities separate and float to the surface as foam. Glass is discolored by introducing special additives and air. Gas bubbles are eliminated. The melt is taken up by vertical or horizontal type drawing machine and shaped into a shape by passing between two rolls, then cooled. Shaped glass also may be manufactured by casting and rolling. A glass melt is poured on the smooth surface and rolled between smooth or figured rolls. Sheet for other items is similar with some exceptions. Properties of glass The compressive strength Rc of glass may be as high as 700mpa – 1000mpa. The tensile strength Rt only 30mpa – 80mpa. Common silicate glass is transparent to the entire visible part of the spectrum, practically to ultraviolet and infrared rays. Silicate glass is highly resistant to attach by various agents except hydrofluoric acids. Flat glass 1) Window sheet glass. It’s widely used kind of flat glass. It’s available in thickness from 2mm – 6mm. The light transparency of window glass ranges from 85% - 90%. Window sheet glass is available in the following varieties: ornamental, manufactured by casting, one side of such glass has a smooth and the other a rehif figured surface; 2) Wire glass obtained by continues rolling with simultaneous imbedding inside the sheet of a wire mesh. It has luchanced fire resistance (up to 1.3h). Light transmission of the glass is not less than 60%, Rc=600mpa, Rb=30 - 40mpa. It’s used for glazing ceiling lightning fittings, window sashes, for making ouritons, for gardening balconies and other applications. 3) Colored and colored wire glasses are obtained by applying a metallic oxide film on to the surface of the colorless glass. It has a golden tint (atspalvis). Such glass is used for gardening balcony, loggias stairs, elevator pits for decorative purposes in dwelling houses, sanatoriums, rest homes etc. 4) Actinic glass is obtained in vertical growing machine, through alrosol processing of the compounds and the processing conditions may be so adjusted as to produce glass with different light and heat transmission and reflection characteristics for various spectrum ranges. Transmission of visible light amounts to 30-70% that of heat rays 40-60%. 5) “Vitrasyl” glass is capable of diffusing light all over the premises. It dominates the glare and is also a good heat and sound absorbing material. 6) Heat-absorbing glass, contains special additives contains special additives with selectively absorbs infrared rays of the solar spectrum. It’s intended to reduce insulation. The transmission of visible light amounts to red rays the 65% and that of infrareds rays not more than 35%. 7) Facing glass is used for lining wall panels. It’s weather resistant and highly hygienic. Facing glass is available with a smooth surface on one side and a figured on other. 8) Stemalite is sheet glass variously texted, coated on one side with solid ceramic pains of various colors. It’s manufactured from non-polished shop window or rolled glass 6-12mm thick of surface areas up to 3m2. Density It’s intended for outside and inside facing of buildings and may be used for the manufacture of multi-layer panels. 9) “Carpet” type art glass tiles are manufacture in squares opaque, pressed or rolled variously colored glass with glazy (blizgantis) a lusterless surface. Tiles available in size of 18x18x4mm, or 22x22x4mm, 23x23x4mm are durable and color fast. They are used for facing wall panels and interiors of premises. 10) Shop window glass is manufactured from polished and unpolished glass 6-12mm thick in panels of 4-12m2. Rc up to 1200MPa. It may be either flat or curved. It’s used for glazing shop windows and openings in shops, restaurants, etc. Other items from glass Glass slabs (stiklo paketai) are 2 or a number of glass sheets fused together hermetically along the perimeter of surface areas up to 5m2. Such slabs are good heat and sound insulators. Sterite is composed of two glass sheets ailed hermetically along perimeter and inter-layered inside with nowowen fiber-glass fabric. It’s used to fill window openings, glaze skylights (stikl. Stogas) and build translucent partitions in various buildings, when diffused light is required. Thickness 7-15mm. Door panels are made from special heat-cured (grūdintas) glass sheets. Such sheet is rather thick, polished or unpolished and rolled art with holes and nocks (išpjovas) for attaching doors fixtures. Thickness 10-15mm, Rc=800-900MPa, Rb=250MPa. Glass blocks are hollow (translucent) items with variously figured inside and outside surfaces. Premises are up uniformly (inside building). Such blocks are obtained by fusing preheated half blocks together. l=0.4. Glass pipes are manufactured by vertical or horizontal drawing or by the centrifugal method. Diameter 15-65mm, length 100-300mm. Such pipes have formed intensive application in the food industry, pharmaceutical, chemical and other industries for handling corrosive liquids. Profile structural glass is channel and boxed elements molded in horizontal rolling machines into a continuous bend out length up to 6m. Profile glass is used for translucent partitions and self-supporting walls, for transparent flat roof). Glass wool is material composed of thin flexible threads and is obtained many mechanical drawing and centrifugal or blowing (glass jet) techniques. Glass wool is used as heat and sound insulating materials. Foam glass and gas glass are obtained by causing neolten glass to expand when mixed with a substance as limestone coal capable of giving off gas at temperatures 750-8500C. It’s a good heat and sound insulating material. Sytals are crystalline materials obtained from glass as the result of its complete or partial crystallization. Crystallization katalysator are components of fluorides and phosphates of alkaline and alkine earth metals. These materials are very strong up to 500mpa and highly resistant to attach by chemical and thermal agents. Sytals from the bases of various glues used for metals, glass and ceramics. They also may be used as constructional and finishing materials. Slay sytals molten slag is blended with admixtures to improve its composition and with modifiers as tio2, caf, P2O5 to accelerate the crystallization of slag. Items have high resistance to abrasion and attack by chemical or atmospheric agents. They are used for floors, decorative and protecting facing, sockets, lining of various elements as anticorrosive. Foam slag sytals l=0.08 till l=0.25 is used as thermo-isolation material. Materials items from cast stone and slag melts Items from cast stone Source materials of cast stone are: rocks magnetic origin, mainly basalt and diabase. The stones cast from them have high chemical and abrasion resistance. Some mat. For manufacture of light – colored cast stone are quartz sand 45%, dolomite 34%, chock or marble 21%. These materials with some additives are melted at a temperature 14500C. Cast stone slabs are used instead of metal ones to pave floors in corrosive media workshops and to line operators exposed to severe abrasive conditions. Materials and items for slag melt Molten slag are used to manufacture floor blocks for industrial plants, facing tiles for corrosive media, tubing for supporting drives in mines, light weight mat. Such as thermosite, slag wool cooled. g=300-1100. Expanding thermosite is a good aquagate for the manufacter of light-weight concrete. Slag wool is material constituted by fine threads obtained from molten blast furnance slags (or other mineral melts). Temperature T=1200-14000C, g=250-300, l=0.05. Items from such wool are widely used as sound and heat insulating material. Mineral binders Classification Mineral binders are fine powders that are capable of producing a plastic pasty mass on mixing with water and passing into a stony state when exposed to physical and chemical action. Mineral binders are subdivided into air-setting, hydraulic-setting, and autoclave-setting varieties. Air-setting binding materials are substances that pass into a stone state gaining and retaining mechanical strength in air only. Hydraulic-setting binding materials are substances that pass into a stone state gaining and retaining strength not only in air, but in water as well. Autoclave-setting binding materials set only when treated in autoclaves with saturated steam at pressures 0,8 – 12 MPa and temperature 170 – 200 °C. Air-setting binding materials Representatives of them are gypsum, magnesium, acid-resistant cement, air-hardening lime (building lime), and anhydrite cement. Gypsum binding materials The source materials for manufacture of such materials are natural gypsum rock and two molecules of water (caso4 ∙ 2H2O), natural anhydrite (caso4) and also chemical industry waste, for example, in Lithuanian conditions – phosphorous gypsum in Kėdainiai. Gypsum binders are subdivided into two groups – low and high burning varieties. Low burning gypsum binder is obtained by thermal processing of gypsum rock at temperature of 150 – 160 °C according to the reaction: CaSO4 · 2H2O → CaSO4 ∙ 0.5H2O + 1.5H2O There are several flow sheets for processing gypsum. The manufacture of building (construction) gypsum involves crushing, grinding and thermal processing of gypsum rock. Extra-strong gypsum (aukštavertis) also falls into the low burning category. It is obtained by heating of natural gypsum by steam at a pressure up to 0.2 mpa, followed by drying at 160 – 180 °C. The process results in formation of larger crystals, the effect being a lower hygroscopicity and gypsum stone of greater density and strength. When water is added to gypsum powder, the semi-hydrate calcium sulphate caso4 ∙ 0.5H2O contained in the later dissolves until a saturated solution is formed according such reaction: CaSO4 ∙ 0.5H2O + 1.5H2O → CaSO4 ∙ 2H2O The fine precipitates of dehydrate calcium sulphates accumulate bond together to cause the setting of the pulp, and then crystallize to form a strong gypsum stone. The setting of gypsum may be accelerated by drying but at a temperature not higher than 65 °C, to avoid the reverse dehydration of the dehydrate gypsum. Setting of building gypsum should begin not earlier than in 4 minutes and end not earlier than in 6 minutes and not later than 30 minutes after it has been mixed with water. The fineness of building gypsum is determined in terms of the total retained on sieve No.02 (size of sieve mesh is 0.2 mm in the clear). The finer content of gypsum, the greater is its strength. The bending strength is determined on specimen bars measuring 4X4X16 cm, 1.5 hours after mixing the gypsum with water. Building gypsum is used for the manufacture of gypsum and gypsum-concrete structural items for interiors of buildings as partition slabs, panels, plaster boards, for preparing gypsum and complex mortars and for manufacture of ornamental and finishing materials, for example, as artificial marble etc. Extra-strong gypsum can successfully replace common building gypsum while making items of great strength. Anhydrite cement It is obtained by burning natural dehydrated gypsum caso4 ∙ 2H2O at temperature of 600 – 800 °C and then grinding the product together with such hardening catalyzers as lime (1-5%) or mixture of sodium sulphate naso4 with green or blue vitriol (akmenėlis arba kuparosas), burnt dolomite (3-8%), granulated blast furnace slag (10-15%) etc. This binding material is a slowly setting binder comparing with gypsum. Its setting starts not earlier than 30 minutes and ends not later than 24 hours. By compressive strength this cement is available in grades 50, 100, 150, 200. Anhydrite cements are used for preparing brick lying and plastering mortars, for heat insulating materials, artificial marble and other ornamental items. Estrich gypsum (High burnt gypsum) It is also a slowly setting binder. It is manufactured by burning natural gypsum or anhydrite at temperature of 800 – 1000 °C, followed by fine grinding, it is used also to prepare brick laying and plaster mortars, to manufacture artificial marble, to build mosaic floors, for low grades of gypsum concrete, etc. Items from this sort of gypsum have low heat and sound conductivity, higher frost and water resistance and smaller tendency to plastic deformation than products from building gypsum. Magnesian binding materials Caustic magnesite and caustic dolomite are two varieties of magnesian binders. Caustic magnesite is obtained by burning magnesite rock mgco3 in shaft or rotary furnaces at temperatures of 650 – 850 °C. In furnace such reaction takes place: MgCO3 ↔ MgO + CO2 Caustic dolomite is obtained by burning natural dolomite at temperatures of 650 – 750 °C, according reaction: CaCO3∙MgCO3 ↔ CaCO3 + MgO + CO2 And then grinding the product to fine powder as in case of caustic magnesite. Magnesian binders are mixed not with water but with aqueous solutions of magnesium sulphate or chloride. Caustic magnesite is available in grades 400, 500, 600 (compressive strength after 28 days). Magnesian binders that are being air-setting have a poor resistance against water. They may be used only in an atmosphere of a relative humidity of not more than 60%. A mixture of sawdust and binder (xylonite) used to make floors as well as fibrolite (a mixture of wooden shavings and binder) and other heat insulating materials are manufactured from magnesian binders, which are also used for fabricating items for interior facing of buildings, subflooring (juodgrindės), sometimes for sculptures. Caustic magnesite with sand and crushed stone is used to manufacture windowsills, footsteps, artificial marble etc. Acid-resistant cement Acid-resistant cement consists of an aqueous solution of soluble glass (sodium silicate), acid resistant aggregate (užpildas) and hardening accelerant (an additive). The micro aggregates are quartz, quartzite, andesyte, diabaze and other acid resistant materials. The main hardening accelerant is sodium fluorosilicate Na2SiF6. The binding material in acid-resistant cement is soluble glass. It is a water solution of sodium silicate Na2 ∙ n ∙ sio2 or potassium silicate K2O ∙ n ∙ sio2, where n = 2.5 ⁄ 3.5. Soluble glass is melted from quartz sand, grounded and thoroughly mixed with ash sodium, sodium sulphate or potassium carbonate in glass tanks at a temperature of 1300–1400 °C. Acid-resistant cement is used to prepare concrete or mortar for building towers, tanks and other installations for chemical industry and for lining chemical operators. Building (air-hardening) lime (Statybinės orinės kalkės) Raw materials Building lime is made by burning limestone (klintys), chalk, dolomite, marl bearing limestone and marl-bearing chalk. Manufacture Building air-hardening lime is manufactured from calcium magnesium bearing rocks containing not more that 6% clay impurities. After burning lump lime is ground to unslaked powder lime or is slaked (gesinamas) with water to yield slaked lime. In burning stage the limestone (calcium carbonate caco3) breaks down into lime and carbon dioxide according to the reaction: CaCO3 + HEAT → CaO + CO2 CaO is unslaked lime. The temperature of limestone burning is set generally between 1000 and 1200 °C. Limestone is burnt in various types of kilns as shaft, rotary, fluid-bed reactors, flash burning furnaces etc. In Lithuania we use shaft, sometimes rotary. The product from the burning of carbonate rock is known as unslaked lump lime (negesintos gabalinės kalkės) or quicklime. This lime is either ground prior to use or directly slaked. Slaking of lime Air-hardening lime differs from other binders because it may be powdered not only by grinding but also by slaking, according to reaction: Cao + H2O → Ca(OH)2 + 65.5 kJ Ca(OH)2 – slaked lime Slaking is particularly rapid when performed under elevated pressure in closed drums. Also lime can be slaked to powdered state in special operators called hydrators. Ground unslaked lime Lime may be powdered not only through slaking but also through grinding in rotary mills. Ground unslaked lime should be ground to a fineness of not more than 1 – 10% oversize on screens. No.023 and 008, respectively which corresponds to a specific surface area of 3500 (in first case – No.023) to 5000 cm2/g. The bigger is specific surface area, the finer are limes. Properties of building lime * Usage At present building air-hardening lime is widely used in preparation of mortars for brick laying and plastering in the manufacture of lime-puzzolana binding materials, artificial stone materials, such as lime-sand bricks (silicate bricks), lime-sand and foam lime-sand items, slag concrete blocks and also as painting compositions. * Transporting Lump lime is transported in bulk care being taken to protect it against humidity and contamination. Ground lime is generally packed in special bituminous impregnated paper bangs or closed airtight metal containers are subjected to heat. Lime paste is transported in specially fitted dump trucks (savivarčiuose). * Storage Lime should not be stored for more than 30 days, as it is gradually slaked by air moisture and looses its activity. Hydraulic-setting binding materials Classification Representatives of hydraulic binders are hydraulic lime, roman cement (romancementis), portland cement, aluminous cement etc. Hydraulic lime It is a product of burning of marl limestone containing 6-20% of clay impurities at temperatures of 900 – 1100 °C. Hydraulic lime is used as a fine powder for preparing construction mortars intended for service in dry or moist surrounding, as an admixture to lower grades of concrete etc. Roman cement It is a product of fine grinding of pure and dolomite bearing marl which contain not less than 25% clay impurities and which have been burnt just below the caking point – 1000-1100 °C. The properties of roman cement are adjusted by the introduction of up to 15% of active mineral additives and up to 5% of natural dehydrated gypsum. Roman cement should set 15 minutes and harden not later than 24 hours after it has been mixed with water. Grades are such: 25, 50, 100 according to compressive strength. Roman cement is used for plasters (tinkai) and brick-laying mortars for low-grade concretes, for manufacture of wall stones and smaller slabs etc. Portland cement * Definition By definition portland cement is a hydraulic binding material that sets and hardens by chemically reacting with water to produce a substance that is durable, resists the effects of water and continuous to gain strength as long as moisture is present. It will continue gaining strength even when completely submerged in water. The process is called hydration and combines cement with water to form a stone-like mass. Compared with hydraulic limes, the strength gained is quite rapid and much greater in value. Portland cement is manufactured by fine grinding of a mixture of limestone or other calcareous material and clay that has been burnt until the components have caked; presence of clay ensures the predominance of calcium silicate in the clinker which is a mixture of raw materials burnt to fusion and composed of grains up to 40mm in size. The quality of clinker governs the major properties of cement: strength and rate of strength gain, durability, resistance to various service conditions. Setting time of cement is controlled by adding gypsum during grinding in amounts from 1.5 to 3.5 or even to 5%. * Raw materials Raw materials that are used for manufacture of portland cement should contain 75-78% of calcium carbonate and 22-25% of clay substance. Rocks meeting the above requirements and % are seldom found in nature. Portland cement is usually manufactured (as in Lithuania) from limestone and clay, which are complemented by the so-called correcting admixtures containing a considerable amount of oxides that are missing in the raw mixture. Thus a deficit of silica oxide SiO2 for an introduction of high silica substances as tripoli or opoka or diatomite. The content of iron oxides may be increased by the addition of pyrite unders (from Estonia) or ore (geležies rūda) because of the lack of iron oxides. * Manufacture There are two chief technologies for manufacture of portland cement: the wet and the dry. They differ by manner of preparing the raw material mixture. In the wet method source materials are ground and mixed in the presence of water and the mixture is burnt in the form of a pulp (slime of a liquid consistence). In the dry method the materials are ground, mixed and burnt dry. Along with the two main techniques there is an increasing tendency to use a combined method, which incorporates the advantages of both methods. According to this technique the raw mixture is prepared by the wet method, then slime is dewatered and processed to granules that are burnt by the dry method. In Eastern Europe the wet method is the most popular one, while Western European countries and USA use the dry method. * Wet method By the wet method lump source material as limestone or chalk or another calcareous material is transported from the quarry to the plant and is crushed to a size not larger than 5mm. Hard rocks are broken up in crushers while softer rocks as clay or chalk are ground by stirring with water in plungers. The resultant pulp is pumped into a tubular rotary mill, which is also continuously fed with crushed limestone. Finally ground material of a creamy consistence (pulp) is pumped to special reservoirs. Pulp or slurry is pumped from reservoirs to tanks and then is fed uniformly to a rotary kiln for burning. Kilns measure 150-250 m in length and 4-7 m in diameter. Such cylinder kilns are sloped 3-4 degrees and revolve above their axis at a speed of 0.5 – 10.4 revolutions per minute. Pulp is injected at the top end of the kiln and moves toward the bottom end. Fuel gas or pulverized coal is injected together with the air at the opposite end of the kiln and burns to give temperature of about 1400-1650 °C, changing the raw material chemically into cement clinker. When clinker is cooled, it is ground together with a small amount of gypsum or anhydrite or another admixture in tubular multi-chamber mill. The gypsum or the anhydrite is added to regulate the setting time of the cement. The finished pulverized product is portland cement. Finished portland cement is conveyed by pneumatic transport to the silos for cooling. Once cooled it is packed in batches at 50 kg in multi-layer paper bags, or loaded in bulk into special shipping facilities as railway cement cars or cement trucks. * Chemical and mineralogical compositions The quality of clinker depends on its chemical and mineralogical compositions. The ranges of oxides composition usually found in normal portland cement are approximately as follows: Lime (cao) – 60-67% Silica (sio2) – 19-25% Alumina (Al2O3) – 3-8% Iron (Fe2O3) – 1-6% Magnesia (mgo) – 0-5% Sulphur trioxide (SO3 – 1-3.5% The chief oxides already mentioned are not free in the clinker and can be in the process of burning into some principal artificial materials. For practical purposes portland cement can be considered as comprising four principal compounds, whose chemical formulas, short abbreviations and relative amount in % are as follows: Artificial mineral Chemical formula Short international abbreviation Amount, % Tricalcium silicate (alite) 3cao ∙ sio2 C3S 42-45 Dicalcium silicate (belite) 2cao ∙ sio2 C2S 12-35 Tricalcium aluminate (celite) 3cao ∙ Al2O3 C3A 4-14 Tetracalcium alumoferrite (braunmilerate) 4cao ∙ Al2O3 ∙ Fe2O3 C4AF 10-18 * Influence of mineralogical composition on properties of portland cement These compounds have the following properties: • Tricalcium silicate (C3S) hardens rapidly and is largely responsible for initial set and early strength. The early strength of portland cement concrete is higher with increased percentages of C3S. • Dicalcium silicate (C2S) hardens slowly and contributes largely to strength increase at ages beyond one week • Tricalcium aluminate (C3A) liberates large amount of heat during the first few days of hardening. It also contributes slightly to early strength development. Cement with low percentages of this compound is especially resistant to soils and water containing sulphates. • Tetracalcium alumoferrite (C4AF) reduces the clinkering temperature, thereby assisting in the manufacture of cement. It acts as a flux in burning the clinker. * Mineralogical composition and strength C3S is the fastest one to gain strength: after 7 days of hardening it attains about 70% of its 28-day-old strength. After 28 days the hydration of C3S goes practically to the end but C2S only begins at that time. Therefore whenever the high strength concrete is required within a short period of time, use is made of cement with a high content of C3S (the so-called alite cement) and conversely. If a high strength is desired at a later date (as a hydraulic massive engineering construction), belite cement (C2S) should be used. The knowledge of the mineralogical composition of clinker bears direct relation to chief physical and mechanical properties of cement. This allows predetermining the properties of portland cement and to design cement and make it for preparing concretes for specific working conditions. * Hardening of portland cement According to the most popular theory, the hardening of portland cement comprises 3 stages. The first stage involves dissolution of the binder in water until the formation of a saturated solution. When portland cement is mixed with water, it hydrates forming hardened cement paste. The second step is the colloid formation or setting. The third stage is crystallization and hardening, when the gel-like formations reclystallize and turn into a crystalline growth. So the system hardens and increases its strength. Portland cement satisfies the standard specifications as its setting begins not earlier than 45 minutes and ends not later than 12 hours from the time of its mixing with water. The hardening of portland cement involves changes in its volume. Hen the process takes place in the air, the cement may shrink due to evaporation of water, but when the cement hardens in water, it tends to swell. Shrinkage is particularly undesirable as the concrete may then crack. To prevent shrinkage deformations, the hardening of cement in particular in its initial stages should be carried out in a humid medium. If water evaporates completely, the hardening practically stops. * Properties of portland cement (test 3, task 2) The main properties are these: 1. Normal consistency of cement paste (finding of quantity of water for normal consistency of the paste) 2. Time of setting (beginning and ending) 3. Bulk density 4. Actual density 5. Soundness (Tūrio kitimo tolygumas) 6. Fineness 7. Unit (or specific) surface area 8. Compressive and bending strength 9. Others: heat of hydration, frost resistance of cement stone, loss on ignition, content of insoluble residue etc. * Corrosion of cement stone Cement stone in concrete may be subjected to the corrosive action by fresh and mineralized water, by combined action of water and frost, by alternative humidification and drying. Corrosion of cement stone in water may be divided into three main types. The first type of failure results from dissolution and washing out of some of its constituents. The second type of corrosion is the failure of cement stone under the action of water carrying salts that are capable of entering into exchange reactions with the cement stone constituents, the products being either highly soluble substances that are readily carried away by water filtering through the concrete or precipitating as an amorphous mass that has no binding properties. The effect of these changes is greater porosity of the cement stone and therefore its reduced strength. The third type of corrosion is so – called “cement bacillus”. Proves due to action of sulphates belongs to this type of corrosion. Poorly soluble substances contained in water or products resulting from their interaction with the cement stone constituents precipitate in the pores of cement stone. Their accumulation and crystallization bring about considerable tensile stresses in pore walls and may lead to the failure of cement stone. Base of protecting cement stone against corrosion bay be following. Corrosion by water may be prevented (reduced) to a minimum by proper designing, by improving concrete preparation techniques and employing cement of a certain mineralogical composition and of a specified content of active mineral admixtures. Drainage, water proofing and water removal are among the possible design means to prevent the action of water upon concrete constructions. Means to improve the water resisting properties of concrete are: intensive compaction of concrete, when it is placed or moulded, usage of concrete mixes of lowest possible water cement ratio W/c – more cement than water and a judicious choice of aggregate size composition (among big particles we must put small to make dense). * Transporting and storage Once cooled portland cement is packed in batches of 50 kg in multi-layer paper bags or loaded into special shipping facilities. Mostly portland cement is shipped in bulk by railroad, trucks or barges generally by pneumatically loading and unloading the transport vehicle. The relative humidity in a warehouse or shed used to store cement should be as low as possible (60% or less). Cement bags should not be stored on damp floor but should rest on pallets. Bags to be stored for long periods should be covered with tarpaulin (brezentas) or other waterproof covering. Bulk cement should be stored in weather tight concrete or steel bins or silos. Cement tends to lose its activity even when stored under the most favorable conditions. After 3 months of storage the loss in activity may be as high as 20% (activity-compressive strength), after 6 months – from 15% to 30%, after a year – up to 40%. Cement of greater fineness loses its activity at a faster rate. * Usage of portland cement It is normally used for reinforced concrete buildings, bridges, pavements and sidewalks, where the soil conditions are normal, for most masonry units, plastering and for all uses where concrete is not a subject to special hazards or where the head generated by the hydration of cement is not objectionable. * Main world trends of manufacture of portland cement At present the world trend is to convert cement works to the dry method through introduction of high capacity rotary kilts (Japan, Germany). As compared to the wet technique, the combined method lowers the consumption of fuel by 20-30%, but requires more electric power and labor. In Russia up to 90% of cement is manufactured b wet method, in the USA – up to 58%, in Canada – 66%, in Great Britain – 94%. In Japan, Germany, France, Italy, Sweden and Mexico, where the raw materials are crystalline limestones of low natural moisture content, the dry method prevails. The designation C150 of the American Society for Testing of Materials (ASTM) provides 8 types of portland cement: I – normal cement IA – normal air intraining cement II – moderate cement IIA – moderate air intraining cement III – cement having high early strength IIIA - air intraining cement having high early strength IV – cement, which needs low heat of hydration V – sulphate resistant cement * Special types of portland cement Several types of portland cement are available commercially and additional special cements can be produced for specific uses. ** Sulphate-resisting portland cement It is manufactured from clinker of predetermined mineralogical composition. The content of tricalcium silicate in cement should not be higher than 50%, of dicalcium silicate not more than 5% and the tricalcium aluminate and tetracalcium alumoferrite in sum should not overcome 22%. This sort of cement is available in grades 300 and 400. Other properties are the same as of the ordinary portland cement. It is used to produce concrete intended for operation in mineralized and fresh waters. Sulphate attach is greatly accelerated if accompanied by alternate wetting and drying, as in a marine structure in the zone between the tides. ** Plasticized portland cement It is made by adding plastic zing surfactants (about 0.15-0.25%) as sulphite waste liquor (SWL), which enhance mobility and make hardened concrete highly frost resistant. There are four grades: 300, 400, 500, 600. They find wide use in roads, airfields, and hydraulic engineering constructions and also in making mortar, plaster and stucco (mortar for outside decorative layers). ** Hydrophobic portland cement This cement has been developed to prevent partial hydration of the cement during storage, especially in damp conditions. A water repellant film is coated around each grain of cement by suitable materials such as oleic acid (aleino rūgštis) or oxidized petrolatum, naphtene soap, acidol or acidol-naphtene soap with the clinker during the production of such cement. These substances are added in amounts of 0.06 – 0.3% of the weight of cement. This water repellant film around each particle of cement is broken during the mixing of the concrete and normal hydration takes place but early strength is rather low when the 28day strength is equal to that of common portland cement. It is available in grades 300, 400, 500, 550, 600. This cement may be used along with cements of the common grades. ** Rapid hardening portland cement The chemical composition of such cement is generally similar to the common one with a slightly higher proportion of C3S to C2S and the cement is ground a little finer. The usage of this cement is indicated where a rapid strength development is desired, for example, where the formwork (klojiniai) is to be removed early for re-use or where sufficient strength for further construction is wanted as quickly as practicable. Since the rapid gain of strength means a high rate of heat development, such portland cement should not be used in mass constructions or in large structural sections. ** Extra rapid hardening portland cement This cement is made by integrating a small amount (around 2%) of calcium chloride cacl2 with rapid hardening cement. This cement is particularly suitable for cold weather concreting. Such type of cement is not recommended for reinforced or prestressed concrete because of corrosion. The setting time of extra rapid hardening cement is short – depending on temperature, it can be 5-30 minutes. ** Low heat portland cement The rise in temperature in the interior of a large concrete mass due to the heat developed by the hydration of cement can lead to serious cracking. By limiting C3S and C3A content of the cement, the heat of hydration can be lowed. Cement having such a low rate of heat development was first produced for usage in large dams in the USA and is known as low heat portland cement. ** White portland cement The source materials for it are pure limestone, chalk or marble and white kaolin clays (china clays). The fuel is gas or fuel oil, which causes no ash contamination of the clinker. Contamination (teršalai) of cement with iron during grinding must also be avoided. Cement should be given a fine grinding. White cement is available in 3 strength grades: 300, 400, 500. It is used primarily for architectural purposes such as facing panels and precast curtain walls (iš anksto surenkamos pertvaros), decorative concrete, stucco, cement paint etc. ** Colored portland cement It is made by adding up to 10% of pigments to white cement. Colored cement is also used as white one – mostly for finishing works, in manufacture of facing tiles, stairs, treads, window-sill slabs, textured panel faces, artificial marble etc. ** Road portland cement It must have a number of specific properties: high strength, wear resistance, frost and rainwater resistance. When clinker is ground, the only acceptable hydraulic addition is granulated blast - furnace slag (up to 15%)/ it is used for concrete surfaces of automobile roads and for their beds, constructions of bridges and some other installations of roads and streets, sidewalks, curb stones (bordiūrai) and reinforced water leakage pipes under roads or streets. ** Antibacterial portland cement It is a portland cement ground together with an antibacterial agent that prevents microbiological fermentation. This sort of cement can be successfully used in swimming pools, public baths, for concrete floors of food processing plants and similar places where bacteria or fungi are present. ** Puzzolana portland cement This is the name given to interground or blended mixtures of portland cement and puzzolana. Puzzolana is a natural or artificial active mineral material containing silica. In the presence of water it forms stable calcium silicates that have cementations properties. Active mineral admixtures are subdivided into natural and artificial varieties. Natural admixtures of volcanic origin are volcanic ashes, volcanic tuffs, pumice, trasses etc. Natural admixtures of sedimentary origin are diatomites, tripoli, opoka and naturally burnt clay rock. Artificial admixtures are granulated blast-furnace slags, belite slime, waste of aluminum manufactured with up to 80% of belite and partly hydrated, ash-waste from combustion of some kinds of solid fuel. And so puzzolana portland cement is a hydraulic cementing material obtained by combined fine grinding of clinker, a predetermined amount of gypsum (up to 3.5%) and an active mineral admixtures or by thoroughly mixing the same materials which have been separately ground. Admixtures of volcanic origin, burnt clay or fuel ash are added in amounts of 25-40% of the weight of cement. Admixtures of sedimentary origin – in amounts of 20-30%. As a rule, however, puzzolana portland cement gains strength very slowly and therefore requires queuing over a comparatively long period, but their ultimate strength is approximately the same as that of ordinary portland cement alone. Fineness is 3000cm2/g, initial setting time is not less than 30 minutes, and final setting time is not more than 10 hours. Minimum compressive strength at 7 days is 220 kg/m2, at 28 days – 310 kg/m2. Such cement is produced in such grades: 200, 300, 400, 500. Bulk density is 900-1100 kg/m3 and actual density is 2700-2900 kg/m3. Their main advantage lies in slow hydration and therefore low rate of heat development. This is of great importance in mass construction and it is there that puzzolana portland cement is mostly used. Puzzolana portland cement is not suitable for elements exposed to systematic moistening and freezing or drying conditions. Such cement has lower water permeability than portland cement because of the expansion of admixtures, which make the concrete denser. Puzzolana portland cements show also good resistance to sulphate attack and some other destructive agents. It is particularly suited for underwater and underground concrete and reinforced concrete constructions. It is used in massive structures, such as dams, pairs or large footings where early strength is not required. ** Gypsum-cement-puzzolana binder (GCPB) This binder is obtained by thorough mixing of 50-75% semi hydrate gypsum with 15-25% portland cement and 10-25% of an active mineral addition containing silica in active form. Grades are 100, 150. It begins to set not earlier than 4 minutes and not later than 20 minutes. Such binder is used for preparing floor bedding (juodgrindės), for internal wall panels, for prefabricating toilet and washroom units etc. ** Slag portland cement It is a hydraulic binding material obtained by combined grinding of portland cement clinker, granulated blast-furnace slag (30-65%) and gypsum (up to 5%). The separate kind of slag portland cement is rapid-hardening slag portland cement, distinguished by intensive strength gained during the initial period (up to 7 days) and is manufactured industrially along with slag portland cement. Such cement is manufactured from rapid-hardening cement clinker and high activity blast-furnace slags. By compressive and bending strengths it is divided into grades 200, 300, 400, 500. Slag portland cement is used for similar purposes as common, but should be preferred in massive hydraulic engineering installations. Along with the above cements use is made in construction practice of locally available binders, such as lime-slag binding material, gypsum-slag, slag clinkerless, lime-puzzolana and other varieties of cement. ** Aluminous portland cement It is a quick hardening hydraulic binding material. The raw materials for manufacture of the sort of cement are limestone or chalk and bauxite. Aluminous cement is obtained by fine grinding of a burned mixture of bauxites and lime (at melting at 1250-1350 °C (sukepimas) or caking at 1500-1700 °C). After approximately 5-6 hours aluminous cement may attain 30% and over of its grade strength value and after a day of hardening – over 90% and in the end of third day – the grade strength. There are such grades: 400, 500, 600. Most favorable for hardening of aluminous cement is moisture atmosphere and normal temperature (20 ± 5°C). No steam curing of aluminous cement items is allowed. The high rate of heat liberation makes it necessary for aluminous cement concrete to be placed in thin sections and never in a large mass because of cracks. Concrete from aluminous cement is air, water and frost resistant and also show good service in fresh and sulphate waters but disintegrate under the action of alkali water. The use of aluminous cement is substantially limited by its cost, which is 3-4 times higher than that of portland cement. This cement is one of the foremost refractory materials. Concrete made with aluminous cement and refractory aggregate is stable at temperature up to 1300 °C. It is particularly valuable where concrete must be put into service in a short time. Repairs to sewers and water concrete mains, for example, can be made overnight. Airport runways can be repaired with little or no disruption of traffic and so in practice aluminous cement is used in urgent repair works of dams, pipes, roads, bridges and urgent laying of foundations. Chemical stability of aluminous cement allows using it for plugging up oil and gas wells in the food industry plants, for lining tunnels and shaft pits. Concrete made with aluminous cement and refractory aggregates is useful for flue linings, combustion chambers for domestic furnaces, for furnace foundations etc. Generally it is limited to service below 1370 °C. ** Expanding cements The main types of expanding cements are such: water impermeable and gypsum-aluminous expanding cements. *** Water impermeable expanding cement It is rapid setting and rapid hardening hydraulic cementing material obtained by grinding or mixing finely ground aluminous cement (about 70%), gypsum (20%) and calcium aluminate (10%) in ball mills. After 1 day of hardening the specimens should be fully impermeable to water applied under pressure of 0.6 MPa. Linear expansion after 1 day of hardening should not be less than 0.2% and not more than 1%. It is used for repairing concrete and reinforced concrete constructions, for water proofing tunnels and pit shafts, in underground and underwater constructions and for water impermeable joints. *** Gypsum-aluminous expanding cement It also is a rapid-hardening hydraulic binding material obtained by combined fine grinding or mixing of high quality alumina _____ (70%) and natural dehydrate gypsum (30%). Grades are 300, 400, 500. Setting begins not earlier than 20 minutes and ends not later than in 4 hours after mixing with water. Specimens from this cement paste should be impermeable to water applied at pressure of 1 MPa in one day. This cement is used for the manufacture of non-shrinking and expanding water permeable mortars and concretes, for caulking joints and for water proofing underground minds. Expanding cements can be used to induce tensile stress in reinforcement used for prestressing purposes. Another type of expanding cement called high-energy expanding cement (įtempiantysis). It is made by intergrinding portland cement clinker, aluminous cement clinker and gypsum approximately in proportions 65:20:15. High expanding cement is quick setting and rapid hardening. Such cement has a high resistance to sulphate attack. Concretes Definition and classification Concrete is an artificial stone resulting from hardening of rationally chosen mixture of binding material water and aggregate (sand and crushed stone or gravel 5-70 mm). The mixture of these materials is called concrete mixture before it hardens. Concrete combined with steel reinforcement is called reinforced concrete. According density r concretes are divided into: 1. Super heavy concrete - r > 2500 kg/m3 2. Heavy concrete - r = 1800 - 2500 kg/m3 3. Light-weight concrete - r = 500 - 1800 kg/m3 4. Extra light-weight concrete - r 0.4 (c/w =2.5) Rcon28 = A1·Rcem (c/w + 0.5), Where Rcon28 – compressive strength of concrete after 28 days of hardening under normal conditions in Pa Rcem – cement activity, i.e. Compressive strength of specimens from cement mortar C/w – cement/water ratio A and A1 – dimensionless factors that depend on the quality of materials. Quality of materials A A1 High 0.65 0.43 Common 0.60 0.40 Poor 0.55 0.37 The strength of concrete is greatly affected by compaction of concrete mix. Under normal hardening conditions the average 7 days strength of concrete specimen’s amounts to 60-70% to that of 28 days. After 12 months it is 75% higher than that of 24 days. The strength of concrete may be roughly calculated for different periods of hardening by this empiric formula: Rn = R28 · lg n / lg 28 Where Rn – strength of concrete after n days in Pa R28 – strength of concrete after 28 days in Pa N – time of hardening in days (more than 3) Concrete strength is greatly affected by surrounding medium. The conditions generally accepted as normal for the hardening of concrete are as follows: general humidity of air 90-100%, temperature 20±2 °C. Such admixture as calcium and sodium chloride, etc accelerates hardening of concrete. This has great practical significance for concreting in the cold season, because the accelerants also allow to mix concretes capable of hardening of subzero (below zero) temperatures. Other kinds of strength Concrete tensile strength is small compared with its compressive strength and has poor correlation with R28. As determined in flexural tests, the tensile strength is about 7 times square root of R28 for the high strength concretes and for the low strength concretes it is 10 times square root of R28. Designing (choosing) of composition of heavy concrete mixes See lab. 5. It is an examination question. Preparation and transportation of concrete mixes The main operations in the process of preparing concrete mixes are proportioning of mixing of ingredients. Materials are proportioned in accordance with the working composition of concrete by measuring devices of batch or continuous action. Most efficient are automatic weighing-machines. According to existing norms, the proportioning tolerances are ±1% by mass for cement and water and ±2% for aggregate. Concrete mixes are prepared in batch and continuous mixers. Concrete mixers are subdivided into positive (būtinasis) mixing and gravity mixing machines. Gravity mixers have drum capacities of 100, 250, 425, 1200, 2400, 4500 liters. Stirring time of a 400 l concrete mixer is 1 minute, that of 4500 l – about 3 minutes. Vibro-mixers have been specially constructed for preparing stiff and extra stiff concrete mixes. Next type of mixers is jet stirring. In turbulent steams of energy carriers such as compressed air (at 0.3 MPa) and super heated steam (85-95 °C) are supplied to special jet mixers. During transportation of the concrete mix to the site of placement, its homogeneity and mobility should be preserved. When considering haulage of concrete account should be taken of the distance, the time of transportation and the mobility of mix. Concrete mixes are carried to concreting sites in transit or in agitating trucks, where the mix is made ready roughly 5 minutes before it is delivered. A special certificate accompanies each batch of concrete mix from the ready mix plant with some necessary data. Placing and compacting of concrete mixes and curing of concrete The placing of a concrete mix and its compaction are currently performed with the aid of concrete placers or distributors. After mix is placed it may be compacted by vibration, Vibro-stamping, centrifuging, vacuumizing and rolling. One of the most widely used techniques for compacting concrete mixes is vibrating. Vibrators are subdivided into electromechanical, electromagnetic, pneumatic types. Large open concrete surfaces as floors, slabs or roads should be compacted with the aid of external vibratos with a metallic platform (20-30 cm depth, about 1 minute). Internal vibrators are used for compacting mixes in massive constructions. Mechanics of materials They are needle vibrators, high-frequency vibrators (up to 7000 oscillations per minute) with a flexible shaft on the working tip. Even better results are obtainable by complementing vacuumizing with repeated vibration. Curing of concrete involves mean that provide normal hardening of concrete mixes and prevent damage to green structures of concrete should be organized immediately after concrete is placed and compacted. Horizontal surfaces are covered with wetted sand or sawdust. Sometimes surfaces are called by film, farming substances such as bitumen, emulsions, latex, synthetic rubber, etc. Placing concrete in freezing weather To reduce the time of hardening down, it is necessary to take such measures: 1. To use high strength and rapid hardening cements. 2. To lower w/c/ ratio 3. To intensity the compaction of concrete mixes. 4. To introduce hardening accelerants 5. To heat concrete mix ingredients (water to 800C аггрегатес то 400C) 6. To cover concrete constructions with heat insulating materials The technique is called “thermas” 7. To heat from outside by steam or electric current. Particular properties of concrete 1. Density (tankumas). High density of concrete is obtained by 1.1. Rational choice of aggregate 1.2. Use of mixes with low w/c/ 1.3. Intensive compaction 1.4. Introduction of plasticizing and hydrophobic surfactant admixtures 2. Water and gas impermeability. Impermeability (water tightness) is an important property of concrete that can often be improved by reducing the amount of water in the mix. Water impermeability of concrete is characterized by the highest pressure of water which concrete is capable of resisting without letting water through. According this concretes fall into 4 grades: 2,4,6,8 that correspond to pressures of 0.2, 0.4, 0.6, 0.8 MPa respectively. Thinner constructions can be made perfectly water tight by using hydrophobic cement. Another method consists in applying a code of water proof plaster by pneumatic techniques (gunitting – torkretavimas) To make concrete constructions gas impermeable their interior surfaces are coated with gas impermeable films such as plastic. 3. Frost resistance – it is characterized by freezing and thawing cycles. According cycles heavy concrete are specified into 6 grades: F15, 100, 150, 200, 300, 400. Frost resistance of concrete can be improved by: 3.1. Increasing water tightness and density 3.2. Entrainment of 2-6% air using special agents. 3.3. Applying a protecting coating to the surfaces 3.4. Using aggregates which frost resistance should not be lower than that of concrete. 4. Volume change. Hardening of concrete in the air is accompanied by a decrease in its volume, but no in this initial period. When concrete hardens in water, its volume increases during the initial period of hardening. Volumetric changes may cause considerable deformation and even cracking of construction. To prevent such things, special expansion joints are provided in massive concrete construction and use is made of cements with 5. Shrinkage. Under air setting conditions concretes shrink. Shrinkage is maximum during the initial period of hardening, its value being 60-70% of the shrinkage after a month of hardening. 6. Creep (plastic flow) – it is strain that occurs under a constant long time load. The concrete continues to deform, but at the rate that diminishes with time. Part of the creep can be recoverable on removal of the load. 7. High – temperature resistance. Special heat resisting concrete is used in constructions exposed to the action of high temperatures (about 2500C) for long period of time. Fire resistance of concrete allows to use it for building chimney stacks of industrial furnaces and their foundations, for lining thermal operators operating at T=10000C and higher. If concrete is heated above 5000C end then wetted, it will disintegrate. At the aggregates are composed of crystalline quartz rack concrete may crack at about 6000C because of a considerable increase in the volume of quartz. 8. Corrosion resistance. Corrosion of concrete is due to the penetration of aggressive substances (of liquids and gases) into the body of concrete particularly through gas and pores. Principal methods against corrosion: 8.1. To make concrete as dense as possible 8.2. To use cements as Portland cements with hydraulic admixtures, slag Portland cement, aluminous cement, sulphate - resisting cement 8.3. To impregnate surfaces with cement mortar and to silicate and fluate them. 8.4. To protect concrete by surface codes (with ceramic tiles or stones, with shells from fat clay or loam, with bituminous materials etc. Special kinds of heavy concretes Hydraulic engineering concretes The classification of them takes into account the zones where concrete is used: 1. Underwater concrete 2. Concrete in zone of fluctuating water level 3. Concrete located above fluctuating water level. The parts exposed to abrasion by water are made of 400 and 500 compressive strength concrete it is determined at the age of 180 days. Frost resistance grades F50-0F300. There are 4 grades of water impermeability: 2,4,6,8/ Natural aggregates as sand and gravel should satisfy the more streanged specifications than common concrete. Granulometric composition of aggregates should provide minimum voids. Acid – resistant concrete Acid resistant concrete obtained from acid-resistant cement and aggregates as quartz sand, crushed stone from andezite quartzite and others is mixed with water glass. This concrete should be hardened in the warm arr-dry conditions. It is used for various constructions and for lining operators in the chemical industry. Refractory concrete ( kaitrai atsparus) It is capable of retaining its properties under prolonged exposure to high temperatures. By the kind of binding material heat resistant concretes fall into the following kinds: 1. Concretes from Portland cement or slag Portland cement 2. Concretes from high-aluminous cement 3. Concretes from periclase cement 4. Concretes from water glass By degree of refractoriness refractory concretes are divided into: 1. High refractory concrete (refractoriness above 17700C) 2. Refractory concrete (15800C - 17700C) 3. Heated – resistant (less than 15800C) with properly chosen binding materials and aggregates concretes may withstand prolonged exposure to temperature up to 12000C and are suitable for building stacks and foundations for blast furnace open heart (Martelio) and other types of industrial furnaces. For all of these sorts of concretes as aggregates can be from chramide, from high – allumine bricks waste, from magnesite brick waste basalt, diabase, andesite and others. Colored concretes They are obtained by introducing alkali and light – resistant pigments into the mix 18 – 10% of the weight of cement) such pigments are: ochre, mummy, mimum and others. Sometimes are used color cements. Aggregates are such: tuffs, red quartzite’s, marble and other color rocks. Color concretes are used for ornamental purposes, underground pedestrian crossings, separating lines on traffic lanes, park lanes and also for the manufacture of items for public welfare. Road and street concrete It is exposed to repeated wetting and drying, freezing and thawing, wears by vehicle wheels; therefore it must satisfy stringent requirements as regards strength, wear and frost resistances atmospheric erosion. According its application road concrete is subdivided into: 1. Concrete for single – layer roads 2. For surface causes at 2 – layer concrete roads 3. For bed causes of 2 layer roads and super – highways. A major strength characteristic of road cement and concrete is the tensile strength in bending, which should amount to 2 – 5.5 MPa and over. Frost resistance of concrete for single – layer roads should range f100, f200 and for bed caused not less than f15. The hardening accelerants particularly effective in freezing weather are admixtures of cacl2 and NaCl. No such admixtures are allowed in pre stressed surface causes, because of corrosion of reinforcement. Concrete for biological shielding The usage of atomic energy has necessitated means for protecting the personal against (36 p) the radiation hazard caused by nuclear reactors, atomic power stations and others (for ex. Special laboratories) particularly hazardous to living organisms are radiation and neutrons. Aggregates for shielding concretes are heavy materials, such as barite z= 3300 – 3600 kg/m3), magnetite (…= 2800 – 4000 kg/m3), limonite (…=2800 – 3000 kg/m3), metal scrap as shots, shavings (…= 3500 – 5000 kg/m3). Binding materials are: portland cement, slag portland cement, alluminous cements. Light weight concretes Concretes of density from 500 to 1800 kg/m3 are referred to a group of light weight concretes of high porosity. Classification of light weight concretes By application light weight concretes are classified as follows: 1. Heat insulating concretes, their ….

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