Asbestos ( Greek ἄσβεστος , indestructible) or mountain flax [1] [2] [3] is the collective name for a number of fine-fiber minerals from the class of silicates that form aggregates in nature consisting of the finest flexible fibers. It is used in various fields, for example, in construction, automotive industry and rocket science.
| Asbestos | |
|---|---|
 Isolated from mineral (ore) and refined asbestos | |
| Formula | see Classification, Chemical composition |
| Trait color | |
| Hardness | 2.5 - 4 |
| Kink | sly |
| Density | 2.5-2.6 g / cm³ |
It is a carcinogen of the first category according to the IARC classification.
Content
Classification
There are two main types of asbestos - chrysotile asbestos and amphibole asbestos.
- Chrysotile asbestos (white asbestos) is a mineral of the serpentine group, the chemical formula 3MgO • 2SiO 2 • 2H 2 O is magnesium hydrosilicate , structurally refers to layered silicates. Due to the incommensurability of the tetrahedral and octahedral layers, stresses arise in the structure of the serpentine, which are compensated by the bending of the T-O packets, which usually leads to their “corrugation”, however, in the case of chrysotile, the direction of the bend is preserved and such layers are twisted into tubes with an external diameter of about 200 angstroms (20 nm). Chrysotile asbestos is resistant to alkaline environments, decomposes in acids with the formation of amorphous silica . Elementary crystals of chrysotile are the thinnest fibril tubes with a diameter of hundredths of a micron. Almost chrysotile is divided into bundles of fibers with a diameter of 10 ... 100 microns, whose tensile strength is 600 ... 800 MPa [1], which is comparable with the best steel grades. This type of asbestos is common in Russia.
- Amphibole asbestos is a complex hydrosilicate . It is similar in physical and mechanical properties to chrysotile asbestos, but has significant differences from it in the crystal structure. The fibrous structure of tremolite is associated with its crystalline structure: the structure is ribbon and consists of double chains of silicon-oxygen tetrahedra, in which individual chains are weakly bonded by magnesium and calcium cations. Weak structural bonds easily break, but the amphibole fibers themselves are highly resistant in a neutral and acidic environment [4]. Amphibole asbestos has worse performance compared to chrysotile asbestos, therefore it is used much less often and where acid resistance is required. Amphiboles have direct needle-shaped fibers - due to the fragility of these structures, they form particles, the inhalation of which is a carcinogenic factor. Therefore, this type of asbestos is forbidden to be used in EU countries in which this type of asbestos was previously widely used. Varieties:
- crocidolite- asbestos or blue asbestos (Na 2 Fe 3 2+ Fe 2 3+ ) Si 8 O 22 (OH) 2 ;
- amosite asbestos (Fe 2+ , Mg) 7 Si 8 O 22 (OH) 2 ;
- tremolite asbestos Ca 2 Mg 5 Si 8 O 22 (OH) 2 ;
- anthophyllite asbestos (Mg, Fe 2+ ) 7 Si 8 O 22 (OH) 2 ;
- actinolite asbestos Ca 2 (Mg, Fe 2+ ) 5 Si 8 O 22 (OH) 2 .
Asbestos is also distinguished by the orientation of the fibers in the minerals: parallel-fibrous and tangled-fibrous. Depending on the impurities of the compounds of iron, calcium, manganese, there is also a different color of asbestos, so hornblende and augite asbestos are white, gray, brown, reddish-brown, almost black; chrysotile - golden yellow, silver-white, greenish, bluish and bluish-black. For example: Ural asbestos is pure greenish, Altai as golden and greenish-yellow [4] . Altai and Ural coil asbestos reach 0.2 meters along the length of fibers, asbestos from Richmond (America) - up to 1 meter.
Chemical Composition
Chrysotile Chemical Composition
The chemical composition of chrysotile is aqueous magnesium silicate, the theoretical composition of which corresponds to the formula 3MgO ∙ 2SiO 2 ∙ 2H 2 O, which corresponds in the mass ratio to the MgO content in it of 42.4%, SiO2 to 44.50%, and H 2 O - 13.04%. As a rule, impurities in the form of FeO and Fe 2 O 3 are always present in it, the content of which rarely exceeds 2%, and part of the chrysotile FeO isomorphically replaces MgO, while the remaining amount of iron is associated with a mechanical impurity of magnetite, less often chromite. The amount of other impurities (Al 2 O 3 , Cr 2 O 3 , CaO, NiO, MnO, CuO and alkali) is determined by fractions of a percent. In the presence of impurities, the amount of MgO and SiO 2 in chrysotile is usually reduced to 40% or less, and the content of constitutional water also fluctuates, either increasing to 14.5-15.0%, or falling to 11.5-12.0%. An idea of the chemical composition of chrysotile is given in the table.
| Components | Bazhenovskoye field (Russia) | Tzetford (Canada) |
|---|---|---|
| SiO 2 | 42.60 | 39.62 |
| Al 2 O 3 | 0.65 | 0.81 |
| Fe 2 O 3 | 1,04 | 4,52 |
| FeO | 0.45 | 1.90 |
| MgO | 40.77 | 39.73 |
| CaO | 0,03 | - |
| Cr 2 O 3 | - | - |
| Nio | - | - |
| MnO | - | - |
| H 2 O + 105 ° | 13.46 | 13.32 |
| H 2 O - 105 ° | 0.95 | 0.43 |
| K 2 O + Na 2 O | Traces | Not |
Properties
In its pure form, chrysotile has a low electrical conductivity, which makes it a high-quality electrical insulating material. Among the important properties are thermal, due to which chrysotile has high heat resistance. In addition, chrysotile is insoluble in water, chemically inert, it is not affected by solar radiation, ozone, oxygen, there are no emissions of harmful gases, vapors, radiation. Chrysotile fiber is easy to fluff in air and water. Treated (fluffy) chrysotile has a high adsorption capacity and exhibits active adhesion to most binding and dispersed ingredients due to the large inner surface of the pores between the fibers and the emergence of strong topochemical bonds [1].
Physico-chemical properties of chrysotile fiber [2]
| No. p / p | Indicators | Numerical range |
|---|---|---|
| one | Tensile Strength, kg • s / mm² | |
| 2 | The density of the mineral, kg / m³ | |
| 3 | Bulk density of fluffed chrysotile, kg / m³ | |
| four | Melting point, ° C | |
| five | Coefficient of friction (for iron) | |
| 6 | Alkali resistance, pH | |
| 7 | Solubility,% when boiled for 4 hours: in HCl with a density of 1.19 kg / dm³ in KOH, 25% | 53.4 - 57.5 0.14 - 1.6 |
| eight | Thermal conductivity, W / (m • K) | |
| 9 | Reflection coefficient in the range 400–700 nm,% | |
| ten | Frequency of the IR absorption spectrum (clearly resolved), cm −1 | |
| eleven | The elastic modulus of undeformed fibers with a cross-sectional area of about 0.01 mm², GPa | |
| 12 | pH of an aqueous suspension | |
| 13 | Sorption ability: dibutyl phthalate, cm³ / 100 g iodine, mg / g water vapor (at 20 ° C) | 40 - 85 1.6 - 1.9 1.6 - 2.5 |
All asbestos have high fire resistance.
Deposits
The largest deposits of asbestos are in Canada (chrysotile), South Africa (crocidolite, amosite, chrysotile) and in Russia (chrysotile) in the Urals - Bazhenovskoe and Kiyembaevskoe deposits. There are also asbestos deposits in the North Caucasus , in Tuva (chrysotile) - the Ak-Dovurak deposit, in the north of Kazakhstan (chrysotile) - the Zhitikarinsky deposit , in China (chrysotile), the USA (chrysotile, amphiboles), Brazil (chrysotile), Zimbabwe (chrysotile) ), Italy (tremolite, chrysotile), France (tremolite), Finland (anthophyllite, the mine was closed in 1975), Japan (chrysotile, tremolite, actinolite), Australia (crocidolite, chrysotile), Cyprus (chrysotile, the mine was closed in 1988 )
Application
Currently, chrysotile asbestos is used in world industry. Chrysotile is part of more than three thousand products in various fields of technology.
Chrysotile is used in the manufacture of:
- roofing, wall products ( asbestos-cement flat and wavy sheets , foam concrete );
- pipes (chrysotile cement pressure and pressureless pipes of various diameters);
- facade plates;
- asbestos-technical and heat-insulating products (fabrics, cords, cardboard, filters, friction products, brake bands, paronite [5] , etc.);
- fixers of the protective layer of concrete for the installation of tunnels, sealants;
- rubber materials, bricks ;
- for the preparation of mastics, sealants, linings, organosilicate coatings, drilling and cement slurries, asphalt mixtures, the preparation of adhesive mixtures and putties, mortars, repair and restoration compounds.
Also, asbestos fabric or string asbestos is used in the field of fire performances (the so-called fireshow) as a material for wrapping fire props (wicks). Asbestos thread impregnated with gun grease is used as an stuffing box in Maxim's machine gun [6] .
World Chrysotile Production in 2015
| Production in 2015 (in 1000 tons) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1100 | 400 | 311 | 215 | 0.35 | |||||
| Russia | China | Brazil | Kazakhstan | other | |||||
Source: US Geological Survey [7]
Health Hazard
Asbestos dust is a carcinogen in the respiratory tract. [8] There is no evidence of a carcinogenic effect in the presence of asbestos with food and water. The fibrogenicity and carcinogenicity of fibers of different types of asbestos is very different and depends on the diameter and type of fibers.
Data on increased mortality and morbidity of workers have been noticed long ago. For example, one of the largest open mines in Europe was in Finland in the town of Paakkila . Only 586,076 tons of amosite and crocidolite asbestos were mined. Mortality in this community reached 150% of the national average. The average life expectancy of men in this place in the 1970s was 57 years, while throughout the country it was 67. The main cause of death of former workers is lung cancer. As a result, the mine was closed even before the international recognition of the substance as carcinogenic.
Convention No. 162 of 1986 on Occupational Health and Safety when Using Asbestos (ILO Convention No. 162), covering all activities related to the effects of asbestos on workers during work, defines protective and preventive measures to prevent exposure to asbestos, monitoring the working environment and for the health status of workers. The governments of countries that have ratified Convention No. 162 and their national laws provide for these protective and preventive measures in relation to their country.
Also, in accordance with Recommendations No. 172 of the International Labor Organization “On labor protection when using asbestos” (adopted in Geneva at the 72nd session of the ILO general conference in 1986), it was determined that the prohibition or permission to use certain types of asbestos and asbestos-containing materials is based products and their replacement with other substances should be a scientific assessment of their health hazards.
When working with chrysotile and other types of fibers, you should control the level of dust and observe the maximum permissible concentration of harmful substances. Compliance with basic sanitary and hygienic requirements in the manufacture of products: general ventilation, aspiration of workplaces, the use of personal protective equipment and wet cleaning of the workplace, protect the health of workers and the safety of the use of chrysotile and its materials. In products, chrysotile is in a bound state (with cement, gypsum, rubber, resins, polymers, oil, bitumen), therefore it is safe and is approved for use in construction and industry in many countries.
Amosite and crocidolite are the most dangerous of asbestos minerals due to their long presence in the lungs of people who breathed them.
Based on the results of comprehensive scientific research on carcinogens, the International Agency for Research on Cancer classified asbestos as the first , most dangerous category of the list of carcinogens for which there is reliable information about their carcinogenicity to humans.
Asbestos consumption in Europe has been declining rapidly lately. On January 1, 1997, the use of asbestos was banned in France . Since 2005, the use of asbestos in the European Union has been completely prohibited [9] . In developing countries, where up to 80% of the world's population lives, chrysotile asbestos is still used in various industries and in housing construction [10] . In Russia, according to the approved list, three thousand types of products containing chrysotile asbestos are allowed for use [11] . At the same time, the use of asbestos-containing materials, in view of the danger of asbestos-generated dust, in residential premises is prohibited or allowed while ensuring the penetration of dust into the premises [12] [13] [14] .
In Russia, the maximum permissible concentration of asbestos dust, including chrysotile asbestos, is carcinogenic (causes the formation of malignant tumors when inhaled [15] ) and fibrogenic (causes asbestosis ) is normalized:
- in the air of working areas: as single as possible - 2 mg / m 3 (6 mg / m 3 for asbestos-cement dust), average - shift - 0.5 mg / m 3 (4 mg / m 3 for asbestos-cement, asbestos bakelite and asbestos-rubber) [16 ] ;
- in the air of populated areas (with chrysotile asbestos in dust up to 10%): daily average - 0.06 fibers per 1 ml [17] .
History
Apparently, from the properties of asbestos, from which ritual figurines were made, the legend came about the salamander - the sacred lizard of the god of fire, who seemed to be able to live in flame and not burn at the stake. According to classical Tibetan medicine, asbestos “heals the veins” and makes a person resistant to stress.
The first written evidence of asbestos use can be found at Strabo . He mentions "stones that scratch and spin cloth from them . " Pliny spoke about this subject in more detail. “There is a fabric stone that grows in the deserts of India, inhabited by snakes, where rain never falls, and therefore it is used to the heat. Funeral shirts are made of it to wrap the corpses of leaders when they are burned at the stake; they make napkins for feasting, which can be heated on fire. ”
Michelangelo , when he was shown asbestos tissue and was introduced to its properties, called this mineral "real hair of Venus."
There has long been a legend about how Akinfiy Demidov brought Peter I a beautiful snow-white tablecloth from his Ural factory. During the meal, he defiantly knocked over a bowl of soup on the tablecloth, poured a glass of red wine, and then crumpled the tablecloth and threw it into the fireplace. Then, taking out of the fire, he showed the king: there was not a single speck left on her. This tablecloth was made of Ural chrysotile asbestos. And in fact, Demidov serf workers have achieved excellence in the manufacture of asbestos fabrics. They made lace hats, gloves, wallets, purses and lace from them. They did not require washing, they were thrown into the fire, and a few minutes after cooling, they could be worn again. With its elasticity, asbestos fabric is stronger than tensile steel wire.
See also
- Ascarite
- Asbestos cement
- Asbestos paper
- Asbestos Ballast
- Paronitis
- Chrysolite
- Vermiculite
Notes
- ↑ Mountain Flax , Great Soviet Encyclopedia. - M.: Soviet Encyclopedia 1969-1978.
- ↑ Mountain Flax // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
- ↑ Mountain Flax , ASIS Synonyms Dictionary, Trishin V.N., 2010.
- ↑ Uralit (Note 1 to the article, supplemented by the Asbest article) , Brockhaus and Efron Encyclopedic Dictionary. St. Petersburg, 1890-1907 Volume XXXIVa (1902): Carbon - Effort, p. 860-862.
- ↑ Paronite , Great Soviet Encyclopedia. - M.: Soviet Encyclopedia 1969-1978.
- ↑ Maxim system machine gun, 1949 , p. 137-138.
- ↑ Mineral Commodity Summaries: Asbestos
- ↑ SanPiN 1.2.2353-08 “Carcinogenic factors and basic requirements for the prevention of carcinogenic danger”
- ↑ France Calls For Worldwide Asbestos Ban ( archived ) Archived April 15, 2012.
- ↑ Chrysotile was again not included in the list of hazardous substances of the Rotterdam Convention
- ↑ Passion for asbestos
- ↑ Sanitary rules and norms of SanPiN 2.2.3.757-99 “Work with asbestos and asbestos-containing materials” /5.7. New construction, expansion, reconstruction, technical re-equipment, repair, conservation and demolition of buildings using asbestos-containing thermal insulation materials Archived May 5, 2016 on Wayback Machine .
- ↑ Recommendations on labor protection when using asbestos-containing materials and products in administrative and non-industrial buildings , Approved January 30, 2003, deputy. Minister of Labor and Social Development of the Russian Federation and deputy. Chairman of the State Committee of the Russian Federation for construction and housing and communal services.
- ↑ Hygienic standards of GN 2.1.2 / 2.2.1.1009-00 "List of asbestos-cement materials and structures approved for use in construction . "
- ↑ Hygienic standards GN 1.1.725-98 “List of substances, products, production processes, domestic and natural factors carcinogenic to humans” Archived May 6, 2016 on Wayback Machine .
- ↑ Hygienic standards of GN 2.2.5.1313-03 “Maximum allowable concentrations (MPC) of harmful substances in the air of the working area” Archived April 19, 2016 on Wayback Machine .
- ↑ Hygienic standards GN 2.1.6.695-98 "Maximum allowable concentrations (MPC) of pollutants in the atmospheric air of populated areas" Archived May 6, 2016 on Wayback Machine .
Literature
- General toxicology / ed. A.O. Loit. SPb .: ELBI-SPb., 2006
- 7.62 mm machine gun Maxim system mod. 1910 Service manual . - M .: Military Publishing, 1949 .-- 184 p. Archived November 24, 2016 on the Wayback Machine
- Asbestos // Military Encyclopedia : [in 18 vol.] / Ed. V.F. Novitsky [et al.]. - SPb. ; [ M. ]: Type. t-va I. D. Sytin , 1911-1915.