Table of contents:
Non-metallic building materials
- Crushed stone
- Expanded clay
Astringent building materials
- Building plaster. Alabaster.
- Dry mixes
Bulk building materials - the name is collective and there is no standard classification of them, but based on various sources, three large classes of bulk materials used in construction can be distinguished. Bulk building materials include:
- nonmetallic materials - gravel, sand, crushed stone, expanded clay and others;
- binding materials - cement, lime, gypsum, alabaster, clay;
- dry mixes for construction finishing works.
Non-metallic building materials
Non-metallic materials are used either as an independent type of building materials, used as bases for various types of buildings and structures, for ballasting railway tracks, for arranging preparation for the main road bed, for landscaping or as aggregates for concrete, mortars and other mixtures.
In accordance with the standard, nonmetallic materials are divided according to the following indicators: by density, by origin, by grain size and by the nature of the grain shape. In terms of density, nonmetallic materials are dense - having a grain density of more than 2 g / cm 3, which include sand and crushed stone, as well as porous ones, whose grain density is less than 2 g / cm 3 - various aggregates such as expanded clay and its varieties. By origin, nonmetallic materials are natural, artificial, and from industrial waste. According to the grain size, coarse-grained materials with a grain size of more than 5 mm and fine-grained materials with a grain size of less than 5 mm are distinguished. The shape of grains in nonmetallic materials can be round (natural sand, gravel) or angular (crushed stone, crushed sand).
These parameters determine the specific type of inert material and, accordingly, the scope of its application. The most commonly used types of nonmetallic materials include sand, crushed stone, gravel and expanded clay.
Sand is a sedimentary rock and an artificial material made up of rock particles. The sand is almost always composed of almost pure quartz. Sand is widely used in construction work as a base for foundations, for the manufacture of various building materials, concrete and mortars, in road construction, etc. One of the most important qualities of sand is its porosity. From a loose to a dense state, sand easily passes under water saturation and vibration. With its open porosity, sand is a good drainage material, and in a dense state it perfectly perceives dynamic loads and distributes stresses under the foundations.
Construction sand can be natural or artificial. Natural sand grains range in size from 0.15 to 5 mm. Since the grain size plays a major role in the selection of concrete and mortar compositions, according to this indicator, sand is divided into fractions: fine - up to 0.5 mm, medium - from 0.5 to 2.0 mm and large - from 2.0 to 5, 0 mm. Natural sand is also divided by types of occurrence and can be river, mountain, sea and dune sand. Mountain (quarry) and river sand found the greatest use in construction.
River sand, which is extracted from the river bed, is usually fine or medium. It is used as an aggregate for concrete, mortar, and the foundations of roads and runways of airfields are made from it. Washed river sand is used for the production of building materials and structures, since, due to the minimum content of silty or clay impurities, it can provide normalized strength indicators.
Quarry sand has a much wider grain size variation and therefore a wider range of applications. It is used for the preparation of masonry mortar, for the preparation of heavy and heat-insulating concrete, as a preparation for road surfaces, for landscaping. The quarry sand contains a significant amount of silt and clay particles.
Sea sand, like river sand, has a high degree of purification, but contains a certain percentage of sea salts, therefore, for some types of work, it is necessary to rinse it with fresh water. Sea sand is used in concrete production and road construction.
Quartz sand is mainly used for the production of decorative types of finishing materials. Artificial sand is made from granite, marble, tuff, limestone by crushing, it is used to produce textured mortars.
By the type of processing, sand is seeded and alluvial. The sifted sand contains no stones and large fractions. Alluvium sand is obtained as a result of washing with ordinary quarry sand and is used for the production of plaster compositions when the presence of clay impurities is unacceptable. Sand of this kind is characterized by a very fine fraction and low density.
The natural bulk density of natural sand ranges from 1300 to 1500 kg / m 3. A change in moisture leads to a change in the volume of sand and, accordingly, its bulk density. The sand used in construction, regardless of the mining method, must meet the requirements of GOST 8736-93.
Crushed stone is produced by crushing rocky rocks. There is granite crushed stone used for the manufacture of high-strength concrete and limestone used for road construction. It is not suitable for use in concrete, since it has low strength. The parameters that determine the quality of crushed stone are: bulk density, frost resistance, strength, water absorption and water saturation, radioactivity, grain size composition and shape of grains.
The density is determined by the fraction of crushed stone. It is divided into 7 main fractions and 7 accompanying fractions from 5 to 70 mm (main fractions) and from 0 to 5 mm (accompanying fractions). The most common in construction is crushed stone with fractions of 5–20 mm and 5–15 mm, which is used for the production of concrete and asphalt concrete.
Crushed stone with fractions of 20-40 mm, 20-60 mm, 20-65 mm and 40-70 mm is used in the construction of roads, the laying of railway, tram and crane tracks.
The strength of crushed stone is determined by laboratory methods. According to this indicator, crushed stone is divided into five groups from high strength to very weak strength. Frost resistance is determined by the ability of crushed stone to withstand repeated freezing and thawing under conditions of saturation with water. The radioactivity of crushed stone is determined by specialized laboratories and ends with the issuance of a certificate and the conclusion of the sanitary and epidemiological surveillance authorities.
GOST 8267-93 regulates the grain composition of each crushed stone fraction in terms of the percentage of smaller inclusions. For crushed stone there is another standardized indicator - the content of lamellar (flaky) and acicular grains in the crushed stone mass. According to this parameter, crushed stone is: cuboid (up to 15% content), improved (15-25%), ordinary (25-35%). For road construction, cube-shaped crushed stone is preferable, as it allows maximum compaction. In the production of concrete, the presence of flaky and acicular grains leads to an increase in the number of voids, which requires an increase in the consumption of binding material and, accordingly, a rise in price.
Gravel is a building bulk material formed as a result of natural destruction of rocks. The size of its grains ranges from 5 to 70 mm. Gravel can be mountain (granite), river (sea) and artificial (expanded clay). One of the important indicators of gravel is the roughness of the surface of its grains, which contributes to strong adhesion of the gravel to the cement mortar of concrete. Mountain gravel has a rougher surface, but it contains clay, sand, fine earth and other impurities. In river and sea gravel, impurities are practically absent, but the smooth surface forces them to be used in the form of crushed stone.
All types of gravel used in construction must meet the requirements of GOST 8267-93. The main characteristics of gravel that determine its suitability for a particular type of construction work are:
- fraction - 4 fractions are used in gravel construction: 5–10 mm, 10–20 mm, 20–40 mm and 40–70 mm;
- frost resistance - the ability to preserve the main strength indicators with repeated freezing and thawing;
- water resistance - gravel is divided into groups in accordance with the softening coefficient;
- the strength of gravel is determined from the average data obtained from the tests of samples. Gravel has high strength, which contains igneous rocks, gneisses, marble-like limestones, silicified sandstones.
At the same time, the presence of sedimentary rocks in gravel reduces its strength parameters.
Gravel is widely used for various types of construction work. It is used as a filler for lightweight concrete, for protective backfilling of roofs, used in road construction, in landscaping, as well as in landscape construction.
Expanded clay is an artificial building material obtained as a result of high-temperature firing of low-melting clay rocks. Its distinctive feature is its low volumetric weight and cellular structure. Expanded clay has three fractions: 5–10 mm, 10–20 mm and 20–40 mm. The norms allow the presence of up to 5% of smaller or larger grains in each fraction. The most widespread is expanded clay gravel; expanded clay crushed stone with grains of arbitrary shape is used much less often. Expanded clay with a grain size of less than 5 mm is called expanded clay sand.
The expanded clay brand is determined by its bulk density. The density of expanded clay and its fraction are interdependent indicators, the larger fraction has a lower bulk density. Strength requirements are established by the standard for all grades of expanded clay. Expanded clay has a water absorption of 8 to 20%, and frost resistance - at least 15 cycles. Thus, expanded clay has completely unique characteristics:
- high strength - from 0.3 MN / m 2 to 6 MN / m 2;
- high heat and sound insulation;
- fire resistance, moisture and frost resistance;
- acid resistance and chemical inertness;
At the same time, expanded clay is an environmentally friendly material. It is this set of indicators that led to the widespread use of expanded clay in modern construction. Thanks to expanded clay, it became possible to lighten the structure without compromising the strength parameters. Expanded clay is widely used in the production of lightweight and heat-insulating concrete, exterior wall panels for industrial and residential buildings.
The heat and sound insulation characteristics of expanded clay are due to its porosity, however, an increase in porosity sharply reduces the strength of the material. Due to its draining properties, expanded clay is also used in road construction when constructing roads and sidewalks. Backfilling with expanded clay of the outer perimeter of the building prevents the soil from freezing.
As a filler for lightweight concrete, due to the penetration of the solution into the pores of the granules, expanded clay shows increased adhesion to the mortar component, which has a positive effect on the durability, strength and chemical resistance of concrete.
Astringent building materials
Binding materials are substances of mineral and organic origin, which are used for the manufacture of concrete and mortars, waterproofing devices, and the homogenization of individual elements of building structures.
Binding materials of mineral origin are powdery substances that, when mixed with water, form a plastic mass that gradually hardens and forms a strong stone-like body as a result. Astringent materials are:
- hydraulic - these include materials that, being mixed with water, and having previously hardened in air, continue to gain strength over a long period (cements, hydraulic lime);
- air - this includes substances that harden and retain their strength parameters only in air (gypsum, air lime).
One of the most common binders is cement. It is an odorless gray powder. It gained its popularity due to its ability, by reacting with water, to turn into a hardening binder. Cement is made from natural minerals - limestone and clay, which are mixed in certain proportions. The ratio of ingredients determines the properties of the cement. The basis of cement is clinker - a baked and crushed mixture.
The most widespread in construction is Portland cement and its varieties - pozzolanic, quick-hardening, oil-well Portland cement. Alumina, acid-resistant, plasticized, slag, expanding cements are often used for certain types of structures. Colored cements are used for decorative work.
The cement marking contains indications of its strength and the content of additives. The chemical and mineral composition of each grade of cement is stipulated by regulatory documents.
With the serial production of building structures, fast-hardening Portland cement is used to reduce the setting time. For its production, the clinker is subject to maximum grinding. The strength of fast-setting cement grows especially rapidly in the first 24–72 hours.
Backfill Portland cement is used in the oil and gas industry for the manufacture of cement “tampons” that close drilled wells. Gypsum is added to its composition.
Pozzolanic Portland cement is more resistant to corrosion than others, although it hardens more slowly and does not differ in frost resistance. Gypsum and active mineral additives are added to the clinker for the production of such cements. The properties of pozzolanic Portland cement allow the use of concrete based on it in the construction of underground structures, underwater parts of bridges and basements.
Alumina cement, unlike Portland cement, does not contain mineral additives. It has a setting time of 30 minutes to 12 hours. On its basis, heat-resistant concrete is produced, it is used for urgent work and for construction in winter conditions.
Acid-resistant cement is obtained as a result of joint grinding of quartz sand and sodium fluorosilicate, and it is kneaded in an aqueous solution of sodium water glass. Its advantage is resistance to the action of acids, and its disadvantage is its weak resistance to water and caustic alkalis. On its basis, acid-resistant concrete is produced.
Plasticized cement has increased frost resistance, and it is obtained by adding sulfide-alcohol stillage to the cement mixture. Slag cement is obtained by simultaneous grinding of granulated blast furnace slag and additives-activators. Expanding cements are used for sealing joints and cracks, for gas, steam and waterproofing. It acquires its characteristics as a result of the reaction between the clinker and the expanding additive. When various dyes are added to white cement (the most free from coloring chemical elements), colored cements are obtained. They are widely used for decorative purposes and in landscape construction.
Lime is obtained from limestone by burning it at high temperatures. The resulting material is called lime-boiling water, because when interacting with water, it actively releases carbon dioxide. This process is called lime slaking. Lime must be slaked for the bulk of its applications. Slaked lime turns into a doughy mass that can be stored for years without losing its qualities. Quicklime is very fire hazardous, since when even a small amount of water gets on it, it begins to be extinguished, and a high temperature arises that can ignite wooden structures.
Lime can be replaced:
- podzol - waste from the tanning industry (low-grade lime mixed with hair), which is filtered through a sieve and kept for at least a month;
- oksharoy - waste from the textile industry (low-grade lime mixed with fine woolen hair). Since okshara contains chlorine, it must be kept outdoors for 5–6 months;
- carbide sludge - calcium carbide waste from the production of acetylene (bluish lime of the second grade).
It is used only after the smell of acetylene has disappeared, for which it is kept in the open air for 1 - 2 months.
Lime paste or formulations based on lime substitutes are used as plasticizing additives in hard cement mortars used in plastering work.
Building plaster. Alabaster
Building gypsum is a finely dispersed powder, white or light gray, produced from gypsum stone by grinding and firing. The advantage of gypsum is its quick setting from 4 to 6 minutes. During hardening, stucco increases in volume up to 1%, which gives it great advantages in some types of finishing work. The disadvantages of gypsum include its low strength and water resistance.
Gypsum is used for the manufacture of binders, interior decoration and stucco moldings indoors. Today there are 12 grades of gypsum from G-5 to G-25, with strength from 5 to 25 kg / cm 2. The highest gypsum strength is 250 kg / cm 2.
The big advantage of gypsum over other building materials is its environmental friendliness and incombustibility. After hardening, it is able to absorb excess moisture from the air and give it away with a decrease in air humidity.
Alabaster, which is a type of gypsum, is widely used for plastering in buildings with a humidity of no higher than 60%, for the production of gypsum plasterboards, stucco moldings and other types of products.
Clay is a soft, finely dispersed type of rock. When diluted with water, it takes the form of a plastic mass that is easily amenable to any shape. After firing, it hardens and becomes stone-like. At higher temperatures, the clay can melt and become glassy. Clay contains various minerals, so they come in a variety of colors.
On the basis of clay, mortars are prepared for laying furnaces, for plaster, compositions for the production of bricks, etc. One of the characteristic properties of clay is its ability to absorb water only up to certain limits, after which it becomes waterproof. This feature allows the clay to be used as waterproofing.
According to the degree of resistance to high temperatures, clays are:
- fusible with a melting point of 1380 ° C;
- refractory with a melting point of 1380 ° C - 1550 ° C;
- refractory with a melting point above 1550 ° C.
Refractory materials are produced on the basis of refractory clays, and refractory clay is used for laying the inner parts of industrial furnaces.
Dry construction mixtures are multicomponent powders, which, when diluted with water, turn into plastic solutions for various purposes. They are a composition of mineral binders, mineral fillers with controlled dispersion, binders based on polymers and modified chemical additives.
The use of dry mixes in finishing works reduces labor costs at the construction site. The complexity of work on finishing the structures of buildings and structures is about 35-40 percent of the total labor costs for the construction of the facility, therefore even a slight decrease in the number of man-hours for each type of finishing work where dry mixes are used, allows you to obtain an economic effect, despite the higher the cost of building mixtures.
The advantages of dry mixes over traditional solutions are noticeable to the eye. First of all, dry mixes are mixed with water at the work site, before being used in the amount required for the production of a specific amount of finishing work. When using them, it will not work that there was not enough plaster solution for the apartment, or there was a surplus, which usually pours onto the ground.
Among the main advantages of dry building mixtures are:
- improving the quality of work on finishing the structures of buildings and structures through the use of solutions with a constantly stable composition;
- increase in labor productivity by 2-5 times;
- reducing the material consumption of finishing works by 3–10 times (at works on laying tiles up to 7 times, and when installing floors - up to 10 times);
- reduction of transport costs and procurement and storage costs due to the possibility of transporting dry building mixtures at any distance without using special technological transport and the admissibility of their long-term storage, including at temperatures below zero.
It should also be noted that the use of dry building mixtures makes it possible to exclude a number of laborious works. So, with high-quality plaster of brick walls using traditional mortars, it is necessary to install four layers (spray, two layers of soil and a cover layer), while when using compositions based on dry mixtures, two layers are enough (soil and a finishing layer). In this case, it becomes unnecessary to putty and sand the surface for painting.
In accordance with GOST 31189-2003 “Dry building mixes. Classification "they can be classified according to the following criteria:
- for the main purpose;
- by the applied binder;
- by the largest aggregate size.
This article will consider the classification only for the main purpose, since information about the types of binders used and the size of aggregates is necessary for specialists - technologists, to whom most of those who read this article do not apply.
So, according to the main purpose, dry building mixtures (mixtures containing binders, fillers, aggregates, prefabricated modifying additives in dry form) are of the following types:
leveling mixtures are used to level the planes of walls and ceilings, which, depending on the method of their application, are divided into:
- plaster mixes - used to level the planes of walls and ceilings, for decorative finishing;
- putty mixtures - used to seal irregularities, caverns and cavities in the preparation of bases with subsequent grinding;
facing mixtures - used for finishing vertical and inclined surfaces with piece finishing materials, which are divided into:
- adhesive mixtures - used for fastening on vertical and inclined surfaces of facing piece materials, for facing surfaces with tiles, for gluing materials with heat-insulating characteristics and reinforcing mesh when using light plaster systems with heat-insulating properties;
- joint mixtures - used to fill the joint space between facing piece materials;
floor mixes - used to perform floor elements, are divided into:
- leveling mixtures - used for arranging a flat base for a finishing floor covering;
- load-bearing mixtures are used for finishing flooring.
Depending on the conditions of use, floor mixes can be divided into:
- compacted mixtures - for the manufacture of flooring structures with their compaction;
- self-compacting mixtures - for the manufacture of flooring structures using injection molding technology;
- grouting mixtures - for finishing uncured concrete or mortar floors by grouting with a dry mixture;
repair mixtures are used to restore the design parameters of structures. Subdivided into:
- surface mixtures are used to restore the design indicators of load-bearing and enclosing structures by processing their surface;
- injection mixtures are used to eliminate defects inside structures to restore their original performance;
protective mixtures are used to create protective coatings on the surface of structures. Protective mixtures are divided into:
- inhibiting mixtures - used for anti-corrosion protection of metal and reinforced concrete structures;
- sanitizing mixtures - used to prevent efflorescence on structures;
- biocidal mixtures - used to protect structures from the effects of bacteria, fungi, algae, lichens, etc., as well as to prevent their growth;
- fire-retardant mixtures - used for the device of surface protective coatings of structures that increase their fire resistance;
- corrosion-protective mixtures - used for the device of anti-corrosion protective coatings of concrete and reinforced concrete structures and products;
- frost-protective mixtures - used for the device of special coatings on the surface of structures in order to increase their frost resistance;
- radiation-protective mixtures - used for application as coatings that protect buildings and structures from ionizing radiation;
- masonry mixes - used for laying external and internal walls from small-piece materials;
- assembly mixtures - used for the installation of building structures and products, and for the monolithing of joints between them;
- decorative mixtures - used for finishing the surfaces of a building or structure and giving them a certain color or texture;
waterproofing mixtures are used to protect load-bearing and enclosing structures from the penetration of natural moisture and aggressive man-made liquids. Subdivided into:
- surface mixtures - mixtures applied to structures as an insulating layer;
penetrating mixtures are used to fill pores and defects in the body of the structure itself, and in turn are:
- injection mixtures - intended for artificial washing of the solution (clogging) into through pores and defects of concrete and reinforced concrete structures, rocks;
- capillary mixtures - intended for artificial washing of the solution (clogging) into the capillaries of porous materials of construction;
- heat-insulating mixtures - intended for the device of a heat-insulating layer on the surface of structures;
- primer mixtures - designed to increase the adhesion strength of the base and finishing coat.