Construction mortars: general technical conditions, composition, application, state standard. Mortars

Based on their density in the dry state, solutions are divided into: heavy ones with a density of 1500 kg/m3 or more; heavy quartz or other sands are used for their production; light solutions having a density of less than 1500 kg/m 3, the fillers in them are light porous sands made of pumice, tuff, slag, expanded clay and other light fine aggregates.

Based on the type of binder, mortars are: cement, prepared with Portland cement or its varieties; lime - based on air or hydraulic lime, gypsum - based on gypsum binders - gypsum binder, anhydrite binders; mixed - with cement-lime binder. The choice of the type of binder is made depending on the purpose of the solution, the requirements for it, the temperature and humidity conditions of hardening and the operating conditions of the building or structure.

Based on their intended purpose, mortars are divided into: masonry mortars masonry and masonry walls from large elements; finishing for plastering, manufacturing of architectural details, applying decorative layers to wall blocks and panels; special, having some pronounced or special properties (acoustic, X-ray protective, plugging, etc.). Special solutions have a narrow application. Based on their physical and mechanical properties, solutions are classified according to two important indicators: strength and frost resistance, which characterize the durability of the solution. Based on their compressive strength, mortars are divided into eight grades: 4, 10, 25, 50, 75, 100, 150 and 200. Mortars M4 and 10 are made using local binders (air and hydraulic lime, etc.). According to the degree of frost resistance in freezing cycles, the solutions have nine frost resistance grades: from F10 to F300.

The composition of the solution is indicated by the quantity (by mass or volume) of materials per 1 m 3 of solution or by the relative ratio (also by mass or volume) of the original dry materials. In this case, the consumption of the binder is taken as 1. For simple solutions consisting of a binder and not containing mineral additives (cement or lime mortars), the composition will be indicated, for example, 1:6, i.e. for 1 hour of binder there are 6 hours. sand. The composition of mixed mortars, consisting of two binders or containing mineral additives, is indicated by three numbers, for example 1: 0.4: 5 (cement: lime: sand). However, it should be taken into account that in mixed cement mortars, cement together with lime is taken as a binder.

The following are used as fine aggregate: for heavy solutions - quartz and feldspathic natural sands, as well as sands obtained by crushing dense rocks; for light solutions - pumice, tuff, shell, slag sands. For ordinary bricklaying, regularly shaped stones, including blocks, largest size sand grains should not exceed 2.5 mm; for rubble masonry, as well as for embedding joints of prefabricated reinforced concrete structures and for sand concrete - no more than 5 mm; for the finishing layer of plaster - no more than 1.2 mm.

Mineral and organic additives are used to obtain a workable mortar mixture when using Portland cements. As an effective mineral additive, lime is introduced into cement mortars in the form of a dough. The addition of lime in cement mortars increases water-holding capacity, improves workability and saves cement. Active mineral additives are used as inorganic dispersed additives - diatomite, tripolite, ground slag, etc.

Surface-active additives are used to increase the plasticity of the mortar mixture and reduce the consumption of binder; tenths and hundredths of a percent of the amount of binders are added to solutions. Sulphite-yeast mash (SYB), hydrolyzed slaughterhouse blood (HA), soap naft, hydrophobic-plasticizing additive “phlegmator”, etc. are used as surface-active organic additives.

The quality requirements for binders, fillers, additives and water are the same as for the materials used to prepare concrete.

QUESTION No. 3.1. Classification of mortars.

Building mixture is an artificial stone material obtained as a result of hardening of a rationally selected mixture of binder, fine aggregate, water and additives.

Classification:

1) By average dry density:

Lungs ρ m<1500 кг/м 3

Heavy ρ m >1500 kg/m 3

2) By type of binders:

Cement

Limestone

Plaster

Mixed

3) But to the purpose:

Masonry

Assembly

Finishing

Special

QUESTION No. 3.2. Materials for mortars and their purpose.

In order to save mortar, hydraulic binders and improve technological properties mortar mixtures apply following materials for mortars - cement and lime, cement and clay, etc.

Lime for mortars is used in the form of ground, (quicklime) powder or lime paste. You can use fatty and lean lime.

Gypsum is used mainly in plaster mortars as an additive to lime. Gypsum is rarely used in masonry mortars.

Sands. Natural (heavy) sands are usually used in solutions - quartz, feldspathic and artificial (light) sands made from tuff, pumice, slag, etc.

For high grades of mortars (more than 100), sands must meet the same requirements regarding the content of harmful impurities as sands for concrete. For solutions of grades 50 and less, the use of sands containing up to 10% of dust and clay particles, but without organic impurities, is allowed.

The sand size is selected depending on the thickness of the joint in the masonry. Coarse sands with a maximum particle size of 5 mm are used only for rubble masonry. For laying bricks and other stones, sand with a maximum particle size of less than 2 mm is used.

Supplements To improve the workability of mortar mixtures, various plasticizing additives are introduced into them. Clay can be effectively used as such an additive in cement and lime mortars. The clay content in the solution should not exceed the binder content. Clay is introduced into the solution in the form of clay milk or (even worse) finely ground powder. Clay as a plasticizing additive should not contain organic impurities and easily soluble salts. Finely ground hydraulic additives of tripoli, volcanic ash, etc. can be added to the solutions.

To improve the technological properties, surfactants are introduced into mortar mixtures, for example, sulfite-alcohol mash (0.1-0.3% by weight of the binder, saponified wood pitch, soap naptha, etc.). These additives also improve frost resistance, reduce water absorption and shrinkage of solutions. When using solutions in winter conditions they contain hardening accelerators and freezing point lowerers (calcium chloride and sodium chloride), as well as heat-generating materials (bleach, lime - boiling water, potash).

QUESTION No. 3.3. Basic properties of mortar mixtures and solutions.

Workability – This property of the mortar mixture is easy to lay in a dense and thin layer on a porous base and does not delaminate during storage and transportation.

Mobility mixtures is characterized by the depth of immersion of the metal cone of a standard device. For brickwork the mobility of the solution is 9-13 cm, for filling the seams between panels and other prefabricated elements - 4-6 cm, and for vibrating rubble masonry - 1-3 cm.

Water holding capacity – this is the property of a mortar mixture to retain water when laid on a porous base, which is necessary to maintain the mobility of the mixture, prevent delamination and good adhesion of the mortar to the porous base. Water-holding capacity is increased by introducing inorganic dispersed substances into the solution mixture. (consisting of small particles) additives and organic plasticizers. The mixture with these additives releases water to the porous base gradually, while it becomes denser, adheres well to the brick, making the masonry stronger.

Strength during compression is determined by testing cube samples at the age specified in the standard or technical specifications for this type of solution. The production of samples from a mortar mixture with a mobility of less than 5 cm is carried out in conventional forms with a tray, and from a mixture with a mobility of 5 cm or more - in forms without a pallet, installed on a brick base.

Mortars Based on strength at 28 days of age under compression, they are divided into grades: 4, 10, 25, 50, 75, 100, 150, 200.

Frost resistance solution is characterized by the number of cycles of alternating freezing and thawing that standard cube samples measuring 15x15x15 cm can withstand saturation with water.

Mortars for masonry exterior walls and external plaster have frost resistance grades: F10, F15, F25, F35, F50, and the grade increases for wet operating conditions. Under such conditions, solutions satisfy even more high requirements by frost resistance: F 100, F 150, F 200, F 300. Frost resistance of solutions depends on the type of binder, water-cement ratio, additives introduced and hardening conditions.

QUESTION No. 3.4. Dry mixes.

Construction dry mixtures– these are factory-made compositions based on mineral binders, including fillers and additives. In some cases, water-soluble or water-emulsifying polymers can be used as a binder. To the place of production construction work dry mixtures are delivered in packaged form, and to use them for their intended purpose, you just need to add the required amount of water.

Dry mixtures have a number of advantages compared to commercial and concrete mixtures: reduction in the amount technological operations for transferring dry mixtures into working condition; improving the quality of construction work due to factory preparation of mixtures; reduction of transport costs by 15%; reduction of solution waste by 5-7% as a result of batch preparation; increase in labor productivity by 20-25% due to increased plasticity of solutions.

Currently, dry mixtures are one of the areas of technical progress in construction; they are used as masonry, installation and plaster solutions, putties, tile adhesives, compositions for self-leveling floors, repair compositions.

Materials used for dry mixtures. Powdered mineral binders are used as a binder: Portland cement, building gypsum, puffed lime. In some cases, powdered polymers are used as a binder, which dissolve in water or form emulsions (cellulose ethers, polyvinyl acetate, acrylates).

Sand with a particle size of 1-2 is widely used as a filler for construction work, and the small grain size should not exceed 1.25 mm. For light solutions, porous expanded sands (perlite, vermiculite, expanded clay) are used. For putties, lime flour and powdered chalk are used.

Additives play a big role in the preparation of dry mixtures. Since mortar mixtures prepared from dry mixtures are laid, as a rule, in a thin layer on porous bases, inorganic and organic plasticizing additives are used to ensure plasticity and water-holding capacity: clay, puffed lime, thermal power plant ash, superplasticizer S-3.

To increase adhesion (adhesion of surfaces of dissimilar bodies), crack resistance and impermeability, polymer additives are introduced into the composition of dry mixtures, which, as mentioned above, must be in powder form, be water-soluble or form emulsions with water.

To carry out work at negative temperatures Antifreeze additives are added to the composition of dry mixtures: potash, sodium nitrite nitrate, calcium formate. At the same time, special requirements are imposed on the hygroscopicity of additives. (ability to absorb moisture from the environment).

Water for mixing dry mixtures should not contain harmful impurities.

The quality indicators of dry mixtures must correspond to the area of ​​application of the mixture. If the dry mixture is used as a masonry mortar, then it must have the following set of quality indicators: plasticity, water-holding capacity, compressive strength, frost resistance.

Construction mortars are thoroughly mixed mixtures of binders (cement), fine aggregates (sand), aggregates (water) and, if necessary, special additives. After hardening it turns out fake diamond. In practice, this is fine-grained concrete, without the addition of coarse and medium-sized aggregates.

Classification of building mortars

Solutions are classified according to the following criteria:

1. According to the binders used:
   • cement, on Portland cement or its varieties;
   • lime, lime, air and hydraulic;
   • gypsum, in which the binder is gypsum.

   Simple solutions use one type of binder. In complex mixtures (for example, lime-cement or lime-gypsum).

   The specific binder is selected depending on the purpose of the solutions, the environmental conditions in terms of humidity and temperature at which hardening occurs, and the conditions in which the building structure is expected to be used.

2. According to the main use of mortars, they are distinguished:
   • masonry, including those used in laying large building elements and for installation work;
   • facing, for the design of various architectural products;
   • plastering machines for plastering buildings inside and outside with decorative layers;
   • for special purposes, with pronounced special properties (for example, plugging, injection or acoustic). Such mortars are intended for narrow, specific applications.
3. According to average density in dry form there are:
   • heavy, volumetric mass ≥ 1500 kg/m3, prepared using quartz sands;
   • light, with a density ≤ 1500 kg/m3. Ground porous materials (tuff, expanded clay, pumice and blast furnace slag) are used as filler. This type also includes porous solutions prepared with foaming agents.

Types of mortars

According to the ratio of the amount of binding materials and fillers, they differ:

• fatty mortar materials characterized by an excess of binders. They are distinguished by their plasticity and ease of use, but have a high degree of shrinkage during hardening. When applied in a thick layer, cracks appear;
• skinny, with low content astringent. They are characterized by low shrinkage, which is especially important when performing facing work;
• normal.

An important characteristic is the strength of the solution. Grades of mortars by strength, meaning compressive strength, are divided into grades from 4 to 200 tons.

Brand strength, depending on the degree of activity of the binder, water-cement ratio and the quality of fine aggregates, is determined in the laboratory by compressing samples in the form of cubes certain sizes after 28 days of hardening at temperatures from 15 to 25 degrees. If hardening occurs in another temperature range, then the relative brand is determined using special tables. Samples with a mixture mobility of ≤ 5 cm are made in collapsible metal forms with a bottom, and with greater mobility in forms on a brick or other solid base.

The relative average strength of cement mortar mixtures hardening under the above temperature conditions is, in fractions of the brand strength, the following values:

• at 3 days of age - 0.25;
• 7 days - 0.5;
• after 14 - 0.75;
• 60 - 1.2;
• after 90 - 1.3.

In mixed mortar mixtures, the greatest strength with optimal workability is achieved by introducing finely ground additives into them.

When using mortar mixtures in winter conditions, their grade is increased by one step (for example, instead of 100, 150 is used) and additives that slow down the freezing of water and accelerate hardening (potash, sodium and calcium chloride, sodium nitrate and others). To mix the mixture, water without harmful impurities is used, usually tap water is used.

Another one important characteristic— frost resistance, characterized by the number of cycles of alternating freezing and thawing that can be withstood. The state standard for frost resistance of construction mortars stipulates 9 grades, from F10 to F300. Tests are carried out in the laboratory with alternate freezing and thawing of water-saturated samples in the form of cubes with 15 cm sides until the initial strength is reduced to 15%. If used in a humid environment, the grade must be upgraded.

When preparing mortar mixtures, it is important to maintain the optimal water-cement ratio.

Decorative colored solutions are used for finishing the front surfaces of large-block structures and panels in factories, plastering inside and outside buildings, and finishing architectural elements. Binders are white and colored Portland cement, gypsum and lime. Fillers are washed quartz sands or obtained by crushing multi-colored rocks (granite, limestone, marble, tuff, dolomite). Mica ≤ 1% or crushed glass up to 10% are added to the mixture. For coloring, natural (ochre, red lead, mumiyo, chromium oxides, ultramarine) and artificial dyes that have chemical and light resistance are used.

The following are added to construction mortar mixtures as additives:

• organic and minerals, increasing workability. Effectively adding to cement mixtures lime paste, which creates savings in cement, increases the ability to retain water, which has great importance during transportation, improves the ease of installation. Mineral additives with high activity (diatomaceous earth, slag powders, tripoli, etc.) are introduced in dispersed form;
• surfactants, which increase plasticity and save binders, are added in hundredths of a percentage of the mass of binders. The most commonly used are SDB and soap naft. The preparation, storage of constituent substances, transportation and use of ready-made mixtures are regulated by GOST 28013-98.

By type of binder mortars are: cement prepared with Portland cement or its varieties; limestone - on air or hydraulic lime, gypsum - based on gypsum binders (gypsum binder, anhydrite binders); mixed – on cement-lime binder. The choice of the type of binder is made depending on the purpose of the solution, the requirements for it, the temperature and humidity conditions of hardening and the operating conditions of the building or structure.

By purpose mortars are divided into: masonry for masonry and masonry of walls made of large elements; finishing for plastering, manufacturing architectural details, applying decorative layers to wall blocks and panels; special, having some pronounced or special properties (acoustic, X-ray protective, plugging, etc.).

According to physical and mechanical properties solutions are classified according to two important indicators: strength and frost resistance, which characterize the durability of the solution. By strength value when compressed, mortars are divided into eight grades: 4, 10, 25, 50, 75, 100, 150 and 200. Mortars M4 and 10 are made using local binders (air and hydraulic lime, etc.). According to the degree of frost resistance in freezing cycles, solutions have nine grades of frost resistance: from F10 to F300.

The composition of a solution is indicated by the quantity (by mass or volume) of materials per 1 m of solution or by the relative ratio (also by mass or volume) of the original dry materials. In this case, the binder consumption is taken as 1. For simple solutions consisting of a binder and not containing mineral additives (cement or lime mortars), the composition will be indicated, for example, 1:6, i.e., 1 part of the binder is 6 parts of sand. The composition of mixed mortars consisting of two binders or containing mineral additives is indicated by three numbers, for example 1: 0.4: 5 (cement: lime: sand). However, it should be taken into account that in mixed cement mortars, cement together with lime is taken as a binder.

As a fine aggregate, quartz and feldspathic natural sands, as well as sands obtained by crushing dense rocks are used for heavy solutions; for light solutions, pumice, tuff, shell, and slag sands are used. For ordinary bricklaying, regularly shaped stones, including blocks, the largest sand grain size should not exceed 2.5 mm; for rubble masonry, as well as giving a monolithic structure to joints of prefabricated reinforced concrete structures and for sand concrete - no more than 5 mm; for the finishing layer of plaster – no more than 1.2 mm.

Mineral and organic additives are used to obtain a mortar mixture that is convenient for laying when using Portland cement. As an effective mineral additive, lime is introduced into cement mortars in the form of a dough. The addition of lime increases the water-holding capacity of mortars, improves ease of installation and saves cement. Active mineral additives are used as inorganic dispersed additives - diatomite, tripolite, ground slag, etc.

Surface-active additives are used to increase the plasticity of the mortar mixture and reduce binder consumption; they are introduced into solutions in quantities equal to tenths and hundredths of a percent of the amount of binders. Sulfite-yeast mash, hydrolyzed slaughterhouse blood, soap naft, hydrophobic-plasticizing additive “phlegmator”, etc. are used as surface-active organic additives.

The quality requirements for binders, fillers, additives and water are the same as for the materials used to prepare concrete.

Mortars for masonry

The compositions of masonry mortars and the type of initial binder depend on the nature of the structures and their operating conditions. Mortars for masonry and for laying large wall elements and their installation are prepared using binders the following types: on Portland cement and Portland slag cement - for the installation of walls made of panels and large concrete and brick blocks, for the production of vibrobrick panels and large blocks, for conventional masonry using high-grade mortars, as well as for masonry performed using the freezing method; based on lime, if high grade mortars are not required, and local binders (lime-slag and lime-pozzolanic) - for low-rise construction. Solutions based on local binders should not be used at temperatures below 10 °C; on pozzolanic and sulfate-resistant Portland cement are used for structures operating under conditions of exposure to aggressive and waste water.

Construction masonry mortars are divided into three types: cement, cement-lime and lime.

Cement mortars used for underground masonry and masonry below the waterproofing layer, when the soil is saturated with water, i.e. in cases where it is necessary to obtain a solution of high strength and water resistance.

Cement-lime mortars They are a mixture of cement, lime paste, sand and water. These solutions are easy to install, have high strength and frost resistance. Cement-lime mortars are used for the construction of underground and above-ground parts of buildings.

Lime mortars have high ductility and ease of installation, adhere well to the surface, and have low shrinkage. They are quite durable, but are slow-hardening. Lime mortars are used for structures operating in aboveground parts buildings experiencing low stress. The composition of lime mortars depends on the quality of the lime used.

The mobility of masonry mortars is determined depending on their purpose and method of installation within the following limits: for filling horizontal joints when installing walls made of concrete and vibrobrick panels and for jointing vertical and horizontal joints - 5–7 cm; for making large blocks of brick, filling horizontal joints when installing walls made of concrete blocks, brick blocks, concrete stones and stones made of light rocks (tuff, etc.) - 9-13 cm; for rubble masonry – 4–6 cm, and for filling voids in it – 13–15 cm.

When selecting the composition of the mortar, the cement consumption per 1 m of sand is set depending on the required durability and operating conditions: 75 kg in cement-lime mortars. For above-ground masonry with a relative humidity of indoor air above 60% and for laying foundations in wet soils, the consumption of cement in cement-lime mortars should be at least 100 kg. The specified cement consumption refers to sand in a loose-saturated state at natural humidity 1–3 %.

As mentioned earlier, to obtain solutions of the required mobility and water-holding capacity, inorganic or organic plasticizers are introduced into their composition. Application of additives when laying below the highest level groundwater not allowed. For masonry of external walls, cement-lime mortars of the following grades are used: for buildings with a relative indoor air humidity of 60% or less - not lower than M10; when the humidity increases to 75%, the grade of the solution must be at least M25, and at a humidity of 75% or more - at least M50.

For underground masonry and the laying of plinths below the waterproofing layer, use cement and cement-lime mortars of grades no lower than M25-50. For reinforced masonry walls, the strength grade of the mortar should be: in dry operating conditions (relative indoor air humidity up to 60%) - no less than M25, and in humid operating conditions (relative indoor air humidity above 60%) - no less than M50. For laying pillars, piers, cornices, lintels, vaults and other parts of buildings, mortars of grade M25-50 are used. To fill horizontal joints when installing walls made of panels, use solutions not lower than M100 for panels made of heavy concrete and not lower than M50 for panels made of lightweight concrete. When laying walls made of panels, large blocks and ordinary masonry in winter conditions, the strength grade of mortar is used depending on the outside temperature and taking into account the load-bearing capacity of the structure. In mortars used for the installation of walls made of concrete and vibrobrick panels and large blocks in winter conditions, chemical additives are widely used that lower the freezing point of the mortar and accelerate its strength gain; potash is added in an amount of 10–15% by weight of the mixing water, sodium nitrite 5 -10%, etc.

Finishing solutions

There are finishing solutions - ordinary and decorative. Conventional finishing solutions prepared using cements, cement-lime, lime, lime-gypsum binders. Depending on the area of ​​application, finishing solutions are divided into solutions for external and internal plasters. The compositions of finishing solutions are established taking into account their purpose and operating conditions. These solutions must have the required degree of mobility, have good adhesion to the base and change little in volume during hardening, so as not to cause the formation of cracks in the plaster.

The mobility of finishing solutions and the maximum fineness of sand used are different for each layer of plaster. The mobility of the solution for the preparatory layer with mechanized application is 6-10 cm, and with manual application - 8-

12 cm. The largest sand size should not exceed 2.5 mm. The finishing layers of solutions containing gypsum should have greater mobility (9-12 cm) than solutions without gypsum (7-8 cm). To regulate the setting time, hardening retarders are introduced into gypsum solutions. For the finishing layer, fine sands with a particle size of no more than 1.2 mm are used. To increase the mobility of plaster solutions, organic plasticizers are introduced.

For external plasters stone and monolithic concrete walls In buildings with a relative indoor air humidity of up to 60%, cement-lime mortars are used, and for wooden and gypsum surfaces in areas with a persistently dry climate, lime-gypsum mortars are used. For external plastering of plinths, rims, cornices and other sections of walls that are subject to systematic moisture, cement and cement-lime mortars based on Portland cement are used. For interior plaster walls and ceilings of a building with a relative air humidity of up to 60%, lime, gypsum, lime-gypsum and cement-lime mortars are used.

Decorative colored solutions are used for factory finishing of front surfaces wall panels and large blocks, for finishing the facades of buildings and elements of urban improvement, as well as for plastering inside public buildings. Decorative solutions used for finishing reinforced concrete panels, must have a grade of at least M150, and for finishing panels made of lightweight concrete and for plastering building facades - at least M50. The frost resistance grade of finishing mortars must be at least F35; water absorption of solutions with fillers made of quartz sand is no more than 8%, and solutions with fillers from rocks with a tensile strength below 40 MPa is no more than 12%.

To prepare decorative mortars, the following are used as binders: Portland cements (regular, white and colored) - for finishing layered reinforced concrete panels and panels made of concrete on light porous aggregates; lime or Portland cement (regular, white and colored) - for the front finishing of silicate concrete panels and for colored plasters of building facades; lime and gypsum - for colored plasters inside buildings.

Washed quartz sand and sand obtained by crushing granite, marble, dolomite, tuff, limestone and other white or colored rocks are used as fillers for colored decorative mortars. To add shine to the finishing layer, up to 1% mica or up to 10% crushed glass is added to the solution. Natural and artificial pigments (ochre, red lead, mummy, chromium oxide, ultramarine, etc.) that are resistant to alkalis and light are used as dyes.

The composition of the decorative mortar is selected experimentally. The mobility of decorative solutions is similar to the mobility of solutions for ordinary plaster. The mobility of decorative solutions for finishing panels and large blocks is established by the technical conditions for the manufacture of these products. The mobility, water-holding capacity and weather resistance of decorative colored solutions can be increased by introducing water-repellent additives (soap naptha) or the plasticizing additive SDB. Sometimes dry mortar mixtures are used, which are mixed with water at the work site.

Special solutions

Special ones include solutions for filling joints between elements of prefabricated reinforced concrete structures, injection solutions, floor solutions, waterproofing, grouting, acoustic and X-ray protective.

Mortars for filling joints between elements of prefabricated reinforced concrete structures prepared using Portland cement and quartz sand with a mobility of 7–8 cm. Mortars that bear the design load must have a grade equal to the strength of the concrete of the structures being connected, and solutions that do not bear the design load must have a grade of at least Ml00. In cases where there is reinforcement or embedded parts in the seams, the solutions should not contain additives that cause metal corrosion, in particular calcium chloride.

Injection solutions represent cement-sand mortars or cement paste used to fill the channels of prestressed structures. Injection solutions are subject to increased requirements for strength (at least M300), water-holding capacity and frost resistance. To reduce the viscosity of the solution, add SDB or soap naphtha in an amount of up to 0.2% by weight of cement. For injection solutions, cement grades M400 and higher are used.

Waterproofing solutions prepared using high-grade cements (M400 and higher) and quartz or artificially produced sand from dense rocks. To construct a waterproofing layer exposed to aggressive waters, sulfate-resistant Portland cement and sulfate-resistant pozzolanic Portland cement are used as binders for the solution. The approximate composition of solutions for waterproofing plaster is 1:2.5 or 1:3.5. For sealing cracks and cavities in concrete and for plastering concrete or masonry by shotcrete or in the usual way use cement mortars with the addition of polymers or bitumen emulsions. If it is necessary to ensure waterproofness of seams and joints in a structure, waterproofing solutions prepared with waterproof expanding cement are used.

Grouting solutions used for plugging oil wells. They must have high homogeneity, water resistance, and mobility; setting times, corresponding conditions for injection of the solution into the well; sufficient water yield under pressure with the formation of dense waterproof tampons in cracks and voids of rocks; strength, resisting the pressure of groundwater, resistance in an aggressive environment. Portland cement is used as a binder for cement mortars. aggressive waters- slag Portland cement, pozzolanic Portland cement and sulfate-resistant Portland cement, and in the presence of pressure water - Portland cement cement. The composition of grouting solutions is prescribed depending on the hydrogeological conditions, type of support and method of grouting work. When excavating mine workings with freezing and fastening with concrete, cement-sand-loamy solutions with the addition of up to 5% calcium chloride are used.

Acoustic solutions used as sound-absorbing plaster to reduce noise levels. Their density is 600-1200 kg/m. Portland cement, Portland slag cement, lime, gypsum or mixtures thereof and caustic magnesite are used as binders. The fillers are single-fraction sands with a particle size of 3–5 mm made from light porous materials: pumice, slag, expanded clay, etc. The amount of binder and grain composition of the filler in acoustic solutions should ensure open, unclosed porosity of the solution.

X-ray protective solutions Designed for plastering walls and ceilings of X-ray rooms. Portland cement and Portland slag cement are used as binders, and barite and other heavy rocks in the form of sand up to 1.25 mm in size and dust are used as fillers. To improve the protective properties, additives containing light elements are introduced into X-ray protective mortar mixtures: hydrogen, lithium, cadmium and boron-containing substances.

The classification of mortars by type of binder is as follows:

Cement mortars (based on Portland cement or its varieties);

Lime mortars (air or hydraulic lime);

Gypsum solutions (based on gypsum binders);

Mixed mortars (with cement-lime, cement-clay, lime-gypsum binders).

Solutions prepared with one binder are called simple, and solutions prepared with several binders are called mixed (complex).

The choice of binder depends on the purpose of the solution, the requirements for it, the temperature and humidity conditions of hardening and the operating conditions of the building. Portland cement, pozzolanic Portland cement, slag Portland cement, special low-grade cement, lime, and gypsum binder are used as binders. To save hydraulic binders and improve the technological properties of mortars, mixed binders are widely used.

Masonry mortars distinguished by type of binder and application. Cement-lime and cement-clay mortars are used for the installation of structures made of large-sized elements, masonry of walls made of bricks and blocks. The binders in this case are Portland cement and Portland slag cement. The addition of lime or clay ensures better workability of the mortar and helps save cement.

Finishing mortars are divided into ordinary plaster and decorative. For external plaster coatings of the walls of buildings with indoor air humidity up to 60%, cement-lime mortars are used, for internal plaster - lime, gypsum, lime-gypsum and cement-lime mortars. For buildings with a relative indoor humidity of more than 60%, cement and cement-lime mortars based on Portland cement are used.

Decorative mortars in modern industrial construction are used for finishing reinforced concrete wall panels and large lightweight concrete wall blocks.

Properties of mortar mixtures

1) workability

2)Delamination

3) Air entrainment

This was written about in question 64

Monolithic and prefabricated reinforced concrete

Monolithic

Disadvantages: seasonality of work, excessive consumption of cement, poor personnel, inability to control all operations, expensive formwork

Advantages: Possibility of changing the external appearance of the building, no seams, no inconvenience to residents due to factories.

Prefabricated everything is the other way around

74. Micro-structure of wood: Wood cells have a cellulose shell; inside there are plateauplasms and vacuoles. By the end of summer, only cellulose remains from the cell. The cells have an elongated shape, oriented along the trunk; by the end of summer, a hollow tube remains. The structure of the tree is porous and fibrous, the fibers are oriented vertically.

Macro-structure of wood: Trees are heartwood, sapwood and mature wood.

Sound and mature wood species are mainly deciduous. Leaf blades mostly wide. The pores of fungi enter the loose part, which feed on cellulose and waste products are colored dark color. In a cross section, between the bark and sapwood there is a very thin layer of living cells. 2 Layers (cambium and phloem) Cambium cells divide and grow growth rings, most of them into wood. The bast transfers water from the roots to the leaves. Longitudinal section - along the projection radius tree rings. Tangent - tangent. Knots may be single and whorled. Whorl - branches extending along one plane.

Destructive and non-destructive methods for assessing the strength of wood.

Destructive: Strength is assessed along the fibers, across the fibers, during bending, during chipping. The compressive strength along the fibers is estimated at maximum load Crosswise at 30 percent linear deformation.

Non-destructive: determination of strength by percentage of late wood

76. Defects of wood:1) Trunk structure: 1. Slope 2. Curvature (one-sided and scalene) 3. Stony 4. Stepson 5. Heel 6. Twist 7. Oblique

3) Cracks:1. Frostweeds 2.Vetrinitsa 3.Otlup

4) Bio-damage

77. Wood range: two-edged, three-edged, four-edged timber. Unfinished board. Clean cut board, Medium board with thin wane, Edged board with blunt wane, block, double floor, plank floor, uncut sleeper, edged sleeper.

Physico-chemical properties: 1. Excellent thermal insulation material

2. Anisotropic

Wood rotting is classified as bio-damage. Caused by mushrooms. Bacteria and insects. In a living tree, spores enter and germinate. First it develops, the wood rots.

The behavior of wood during combustion goes through several stages:

When heated to 105°C, water evaporates from wood;

When heated to 150°C, residual moisture is removed from the wood and decomposition and release of gaseous products begin;

When heated to 270-280°C, an exothermic reaction begins with the release of heat, i.e. conditions have been created for self-maintenance of the required temperature, at which wood decomposes with the formation of a flame and a further increase in temperature;

At a temperature of 450°C or more, flaming combustion turns into flameless combustion of coal (smoldering) with temperatures up to 900°C.

Methods of protection against rotting are, first of all, the desire to try to avoid constantly heating enclosed spaces (conditions conducive to the development of fungi), impregnation of wood with special compounds. You can protect wood from burning by covering it with special compounds, or by covering it with paint, varnish, etc., which in turn, it will also protect the tree from burning.

Composition and properties and scope of application of bitumen and tars

Bitumen and tars

The allocation of auxiliary materials into a separate group is determined by their secondary role in the creation of decorative and finishing coatings. For example, bitumen and tars, which have a specific odor and black-brown color, are rarely used directly in finishing. However, in the composition of mastics, varnishes, and waterproofing, these materials play a primary role.

Bitumen and tars are a group of organic binders. Bitumen (natural, oil, shale) are substances consisting of high molecular weight hydrocarbons of the naphthenic, aromatic and methane series and their oxygen, sulfur and nitrogen derivatives, completely soluble in carbon disulfide. Tars (coal, peat, wood) are substances consisting mainly of a mixture of high molecular weight aromatic hydrocarbons and their oxygen, nitrogen and sulfur derivatives.

The chemical composition of bitumen and tar is complex. It contains about 200 different organic substances. Bitumen and tar have a number of properties general properties:

1) at normal temperatures, organic binders are solid masses or thick liquids of a dark, almost black color;

2) when heated, they soften (liquefy), and when cooled, they harden. This feature allows them to be used as a binder;

3) they are practically insoluble in water (and many in acids), but soluble in organic solvents (carbon disulfide, chloroform, benzene, dichloroethane, etc.). This allows them to be used in the manufacture of varnishes and mastics;

4) the true and average densities of bitumen and tar are equal, since they have no porosity, therefore, they are practically waterproof;

5) bitumen and tar are hydrophobic (not wetted by water);

6) taking into account properties 4 and 5, we can make a conclusion about the water resistance and frost resistance of bitumen and tar. These properties allow them to be used as roofing and waterproofing materials;

7) bitumens and tars have an amorphous structure, therefore they do not have a specific melting point, but there are softening intervals, that is, when heated, they gradually transform from a solid to a viscous-liquid state;

8) bitumens and tars, when softened, firmly adhere to stone, wood, metal, etc. (this property is called adhesion). Used when used as binders; Bitumen and tar can be brought into working condition not only by melting and dissolving in organic solvents, but also by emulsifying in water. (Bitumen emulsions are produced using special emulsifier additives.)

When assessing the quality of bitumen and tars, it is necessary to know their group composition. The group composition of bitumen includes:

oils (45 ...65%) - viscous liquids of light yellow color with a density of less than 1, consisting of hydrocarbons with a molecular weight of 100 ...500; oils give the binder mobility and fluidity;

resins (15... 30%) - viscoplastic, high-molecular amorphous substances of dark brown color with a density of about 1 and a molecular weight of 500... 1000; the degree of bitumen plasticity and astringent properties depend on their content;

asphaltenes (10... 30%) - hard, brittle substances crystal structure with a density greater than 1 and a molecular weight of 1000... 5000; their content determines the heat resistance, viscosity and fragility of the binder;

carbenes and carboids (1... 2%) - solid carbonaceous substances formed at high temperatures; their content increases the viscosity and fragility of the binder.

The admixture of crystalline paraffin in bitumen (0.6...8%) reduces its quality, in particular increases fragility at low temperatures.

Group hydrocarbons, as components of bitumen, form a complex system. The dispersion medium in this system is a molecular solution of resins or their parts in oils, and asphaltenes serve as the dispersed phase. Asphaltogenic acids are adsorbed in the boundary zone. If there is an excess of dispersion medium in the system, then complex particles (micelles) move freely in it and do not contact each other. This is typical for liquid bitumen at normal temperatures and for viscous bitumen at elevated temperatures. With a reduced amount of dispersion medium and a larger number of micelles, they contact each other and form a micellar spatial network. Such bitumens are characterized by high viscosity and hardness at room temperature.

In addition to oils (60...80%) and resins (15...25%), tars contain free carbon (5...25%) - a solid substance with a high molecular weight. Tar also contains naphthalene, anthracene, phenols and some other impurities.

By origin, bitumen is divided into natural, oil (artificial) and shale.

Natural bitumens are formed as a result of the natural process of oxidative polymerization of oil. They sometimes meet in pure form, forming lakes, but more often they impregnate rocks - limestones, dolomites, sandstones. Such rocks are called bitumen or asphalt.

Natural bitumens are obtained from asphalt rocks by extraction using various solvents (but this is an expensive method, so it is not widely used), or by boiling in hot water.

Artificial petroleum bitumens - products of oil refining and its resinous residues - are almost six times lower in cost than natural ones. According to the production method they are divided:

to residuals obtained from hydron by further deep selection of oils from it;

oxidized, obtained by oxidizing oil residues with air oxygen in cubes (converters) of continuous or periodic action;

cracking, obtained by processing residues formed during oil cracking;

compounded, obtained by mixing petroleum products of various viscosities;

deasphalting bitumens obtained by precipitation of the asphalt-resinous part of hydrons with propane and other solvents.

In our country, the most common method for producing oxidized bitumen.

Tar - the residue after distillation of oil fractions from fuel oil; it is the main raw material for the production of petroleum bitumen.

The term “shale” bitumen is not entirely accurate. In terms of properties and chemical composition, shale bitumens are close to bituminous materials, and in terms of the production method - to tars. The scope of application of shale bitumen is basically the same as that of oil bitumen.

By purpose, bitumens are divided into construction, roofing and road, and according to their main properties they are divided into grades.

Construction petroleum bitumen is produced in three grades: petroleum bitumen BN-50/50, BN-70/30, BN-90/10. The numbers show: numerator - softening temperature, °C; denominator is the average needle penetration depth. They are used for the production of asphalt concretes and mortars, adhesive and insulating mastics, coating and restoration of roll roofing.

Petroleum roofing bitumen used for the production of roofing and waterproofing materials is produced in three grades: petroleum roofing bitumen BNK-45/180 - impregnating bitumen, BNK-90/40 and BNK-90/30 - coating bitumen. The numbers show: the numerator is the average value of the softening temperature, °C, the denominator is the average value of the needle penetration depth.

Petroleum road bitumen, used as a binder in the construction of road and airfield pavements, is produced in five grades: petroleum road bitumen BND-200/300, BND-130/200, BND-90/130, BND-60/90, BND-40/ 60. The numbers show the permissible deviation limits of the needle penetration depth at 25°C.

When viscous bitumen is liquefied with liquid petroleum products, liquid petroleum bitumen is obtained. Depending on the rate of structure formation, liquid bitumen is divided into three classes: BG - fast-thickening, SG - medium-thickening, MG - slow-thickening.

Liquid bitumen is used mainly in road construction (for processing gravel and crushed stone mixtures, producing asphalt materials).

Tar is obtained in the process of destructive (heating without air access) distillation of solid fuels. Depending on the source raw material, coal, peat and wood tars are obtained. Coal tar is the most widely used in construction practice.

It is a viscous, non-explosive, oily liquid of black color with a characteristic odor due to the content of phenols and naphthalene in it.

The composition of coal tars includes coal tar pitch (about 50%) and high-boiling fractions of coal tar, which determine their toxic properties.

Depending on the viscosity value, coal tars are divided into six grades: D - 1, D - 2, D - 3, D - 4, D - 5, D - 6.

When processing 1 ton of coal, 700... 750 kg of coke, 300... 350 m3 of coke oven gas, 12... 15 liters of benzene, up to 3 kg of ammonia, 30... 40 kg of raw tar (raw coal tar) are obtained. Raw coal tar is not suitable for production building materials, as it contains a significant amount of volatile substances and soluble compounds washed out by water, which reduce their weather resistance. By distilling water, all light and partly medium oils from raw tar, distilled tar is obtained, and with further distillation of medium and heavy oils, anthracene oil and pitch are obtained.

Compound tar is obtained by fusing pitch with anthracene oil or distilled tar. Compounded tars are most suitable for construction purposes, since by changing the ratio between pitch and anthracene oil or distilled tar, it is possible to obtain compounded tars of the required viscosity and softening point.

Coal tar pitch is the solid residue after distillation of all volatile fractions from coal tar. This amorphous substance black, fragile, with a characteristic shine and conchoidal fracture. It consists of high molecular weight hydrocarbons and their derivatives and free carbon in the form of fine particles (8... 30%). Coal tar pitch is produced in two grades: medium-temperature (A and B) and high-temperature, which differ from each other in softening point, ash content and moisture content.

Distilled and compounded tars, anthracene oil and pitch are used as raw materials in the production of tars. roofing materials, gluing and painting mastics.

Bituminous materials are most widely used in construction (they are more weather-resistant), while tar materials serve as valuable raw materials for the production of various chemical products. In addition, tar materials age relatively quickly under the influence of moisture, atmospheric oxygen, and solar radiation, becoming brittle and low-strength. But tar materials are more bioresistant than bitumen ones. Resistance to decay is explained by the high toxicity of the phenol contained in tars, for example, carbolic acid.

Bitumen and tar are united by the similarity of composition and structure and, as a consequence, the similarity of basic technical properties.

The most important parameters tars and bitumens are viscosity, plasticity and heat resistance. If necessary, additional quality indicators are determined for bitumen and tar; flash point, brittleness temperature, adhesion to stone materials, etc.

1. The viscosity of bitumen and tars is a characteristic of their structural and mechanical properties and depends mainly on temperature. As the temperature rises, the viscosity decreases, and as the temperature decreases, it increases sharply; At low temperatures, bitumen and tar become brittle. Structural viscosity for liquid bitumen and tars is determined by the sample flow time in seconds at a constant temperature through the orifice of a standard viscometer measuring 5 or 10 mm. For semi-solid and solid bitumen, structured viscosity, or more precisely fluidity (the reciprocal of viscosity), is measured in conventional units by the depth of penetration of a needle into the bitumen at a certain load, temperature, and immersion time.

2. The plasticity of bitumen is characterized conventionally by the elongation value of the thread before breaking, expressed in centimeters, at a temperature of 25°C.

3. The heat resistance of bitumen and tars that have an amorphous structure is determined using a “ring and ball” device by the temperature at which bitumen or pitch, poured into the ring, is squeezed out to a certain depth (2.54 cm) under the influence of the mass of the steel ball.

4. The flash point characterizes the degree of flammability of bitumen when heated in boilers.

5. The brittleness temperature is the temperature at which the first crack forms in a bendable thin layer of bitumen applied to a steel plate of a special device. The lower the brittle temperature of bitumen, the higher its frost resistance and the higher the quality of bitumen.

6. Solubility in organic solvents.

8. Water resistance is characterized by the content of water-soluble compounds.

9. “Passive” adhesion to marble and sand, etc. Coal tars and bitumens are flammable substances; tar flash point - 150... 190°C, ignition temperature - 180...270°C; auto-ignition temperature is above 540°C. Temperature limits for ignition of vapors: lower - above 120°C, upper - above 150°C. Flash point of bitumen 220... 240°C (depending on brand), minimum temperature self-ignition 300... 368°C.

Tars and bitumens are stored in closed storage facilities equipped with devices for heating with steam. In construction, bitumen and tar are used: for the production of rolled roofing, waterproofing and sealing materials; production of various mastics, pastes, emulsions and simple varnishes; preparation of asphalt concrete and mortars.

80. Rolled roofing materials based on bitumen and tar Bitumen and tar rolled roofing materials, despite some significant disadvantages compared to asbestos-cement and tiles (lower durability and fire resistance, the need for a continuous sheathing for laying them), are widely used in construction, especially in industrial construction. They allow you to install roofs with a low slope, flat roofs and roofs of complex configuration; their use reduces the cost of operating the roof in an aggressive environment, etc.

In the total volume of all types of roofing materials, about 50% falls on the share of soft roofing.

Roofing and waterproofing materials Based on bitumen and tar, they are divided into rolls, sheets and piece products, coating materials - mastics, emulsions and pastes, and based on the type of binders - into bitumen, tar, gum, rubber bitumen, bitumen and tar polymers.

Rolled roofing and waterproofing materials can be of two types - basic and non-core. Basic materials are produced by treating the base with an organic binder - roofing cardboard, fiberglass, glass felt, metal foil, asbestos cardboard, etc. Non-base materials are obtained in the form of panels of a given thickness by rolling on calenders thermomechanically processed mixtures of organic binder, powder or fibrous filler and special additives The materials of the first type are most widespread in construction; some of their representatives were first manufactured in 1877 in Russia by engineer. A. A. Summer.

Depending on the class of structures, climatic and operational conditions, and the slope of the roof, rolled materials are laid in one, or more often in several layers, which form a monolithic covering called a roofing carpet.

In accordance with their purpose, roll materials with a base are divided into two types: cover and coverless. Covering materials, used mainly for the upper part of the roofing carpet, are obtained by impregnating the base with organic binders and applying a covering layer of more refractory organic binders to it on both sides, often with the addition of fillers, antiseptics and other components. The covering layer is susceptible to atmospheric influences. Coverless materials intended for the lower and middle parts of the roofing carpet do not have a covering layer.