Definition & Chemical Composition of Asbestos

What is asbestos?

This article gives a definition of asbestos and interestingly, explains that the name asbestos does not refer to a distinct mineral species but it is a commercial term applied to fibrous varities of several minerals differing widely in composition, strength, flexibility, and usefulness.

This article series describes the physical properties of asbestos including its mechanical, chemical, electrical and related properties both in pure asbestos form and when asbestos is mixed with other materials. Page top photo: tremolite asbestos fibers in the microscopy laboratory - ©Daniel Friedman.

Definition of Asbestos Fibers

Asbestos is the name given to a number of mineral silicates. The name asbestos does not refer to a distinct mineral species but it is a commercial term applied to fibrous varities of several minerals differing widely in composition, strength, flexibility, and usefulness.

Figure 2.2. View showing parallel fiber structure of asbestos vein, (Courtesy Johns-Manville-Corp.) [Click to enlarge any image]

Chemical and mineralogical studies show that asbestos is of mineral origin. The most important variety is chrysotile, which constitutes approximately 95 per cent of total world prOduction. Its wide use is caused by the fact that its fibers are generally strong, flexible, chemical resistant, and heat resistant.

Other varieties of asbestos are crocidolite, amosite, anthophyllite, tremolite, and actinolite; each has its own field of utility. The chrysotile is classified as being of the serpentine family. The others are of the amphibole family.

The amphibole groups of asbestos minerals were originally known as hornblende, inasmuch as they were closely related to the minerals tremolite and actinolite. This group is made up of complex silicates.

Such varied types of fibers as tremolite and actinolite have widely different chemical structures. Sometimes, it is difficult to identify these different minerals except by x-ray. The amphibole group is interesting insofar as chemical aspects are concerned;, although, weak fibrous structures are present in the group..

Specific gravity of asbestos fibers ranges from 2.5 for chrysotile to 3.3 for the other types.

Chemical Compostion of Chrysotile, Crocidolite, Amosite, Anthophyllite & Tremolite Asbestos

The chemical composition of the various types of asbestos are shown in Table 2.1.

Also see ASBESTOS FLOOR TILE COMPOSITION for an example of distinguishing between use of chrysotile and crocidolite asbestos in products.

TABLE 2.1. CHEMICAL COMPOSITION OF VARIOUS TYPES OF ASBESTOS * [ Click to enlarge or view details]

* Encyclopedia of Chemical Technology, Vol. 2, New York and London, Intérscience Publisher (1948).

The chemical feature common to all asbestos is that they are hydrated silicates The degree of hydration varies from approximately one per cent in some types to as much as approximately 14 per cent in most kinds of chiysotile It generally accepted that asbestos is a metamorphic product derived from certain types of silica-bearing minerals.

Asbestos is generally as dense as the rock in which it occurs but it forms masses of fibers

Definition of Friable & Nonfriable Asbestos Materials

U.S. EPA Definition of Friable Asbestos

The US EPA in their "Asbestos NESHAP Adequately Wet Guidance" defines "friable asbestos material" as

Friable asbestos material is any material containing more than 1 percent asbestos as determined using Polarized Light Microscopy (PLM), that, when dry, can be crumbled, pulverized, or reduced to powder by hand pressure. - (EPA p, 3)

Properly defined in plain english, "friable" asbestos means that one can easily produce powdered material, for example by rubbing asbestos pipe insulation between one's fingers to produce a crumbly dust. In this regard your floor tiles are a mix of asbestos and vinyl or asphalt, and are not readily friable.

The definition of friable asbestos is important, because non-friable asbestos-containing material is less likely to be an asbestos hazard in buildings, unless it is mechanically ground or pulverized.

Asbestos is most-hazardous when it is friable. An example of friable asbestos include sprayed-on asbestos insulation.

U.S. EPA Definition of Nonfriable Asbestos Material

The US EPA in their "Asbestos NESHAP Adequately Wet Guidance" defines "nonfriable asbestos material" as

Nonfriable asbestos-containing material is any material containing more than 1 percent asbestos as determined by Polarized Light Microscopy (PLM) that, when dry, cannot be crumbled, pulverized, or reduced to powder by hand pressure. (Op Cit. p. 3)

By this definition, asphalt-asbestos and vinyl-abestos floor tiles are normally and virtually always non-friable materials.

Examples of nonfriable asbestos include asbestos-containing ceiling tiles, floor tiles, roof shingles, siding shingles, and similar "hard" materials. These materials do not release asbestos fibers unless they are disturbed or damaged, for example by drilling into an asbestos-containing ceiling tile or running power equipment or usign other means to aggressively break up and demolish asphalt-asbestos or vinyl-asbstos floor tiles.

Photo below: asbestos cement siding shingles: not friable.

You will see the importance of the distinction between friable and non-friable asbestos containing materials in articles about asbestos removal, encapsulation, or hazard reduction in buildings, such as

at ASBESTOS FLOORING HAZARD REDUCTION

Asbestos is safe and legal to remain in homes or public buildings as long as the asbestos materials are in good condition and the asbestos can not be released into the air. - US EPA [not currently easy to find this source - Ed. 2021]

THE BEST THING TO DO WITH ASBESTOS MATERIAL IN GOOD CONDITION IS TO LEAVE IT ALONE!

Disturbing it may create a health hazard where none existed before. - U.S. EPA, "Asbestos In The Home", retrieved 2021/07/17 original source: https://www.cpsc.gov/safety-education/safety-guides/home/asbestos-home

Photo below: friable asbestos debris from damaged paper asbestos duct insulation.

Watch out: some non-friable asbestos-containing materials such as floor tiles or paper duct insulation become friable either during demolition or in the case of paper asbestos insulating products the material may become friable due to exposure to water or weather.

See examples at ASBESTOS PAPER DUCT INSULATION

Above: Except from EPA's Guide to Demolition Practices (for non-friable asbestos material cateogies and handling), discussed in detail

at ASBESTOS LEFT in PLACE in BUILDINGS - MANAGEMENT GUIDES

...

Continue reading  at ASBESTOS FIBER PROPERTIES or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• ASBESTOS DEFINITION & COMPOSITION
• ASBESTOS FIBER PROPERTIES
• ASBESTOS in GOOD CONDITION - what to do about it
• ASBESTOS FLOORING LEFT IN PLACE - keep it and cover it
• ASBESTOS FLOORING REMOVAL GUIDE - if you must remove it
• ASBESTOS IDENTIFICATION IN BUILDINGS - home
• ASBESTOS LEFT in PLACE in BUILDINGS - MANAGEMENT GUIDES
• ASBESTOS LIST of PRODUCTS
• ASBESTOS PHOTO GUIDE to MATERIALS
• ASBESTOS PRODUCTS BANNED vs PERMITTED U.S. 2023

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