Asbestos refers to six naturally occurring fibrous minerals that have the ability to resist heat, fire and electricity. Chrysotile, crocidolite, amosite, anthophyllite, tremolite, and actinolite. Among these, chrysotile and amosite asbestos is the most common.
Today we will talk about the most common: Chrysotile and Amosite.
Chrysotile or white asbestos is the most commonly encountered form of asbestos. It is a soft, fibrous silicate mineral in the serpentine subgroup of phyllosilicates; as such, it is distinct from other asbestiform minerals in the amphibole group. Its idealized chemical formula is Mg3(Si2O5)(OH)4.The material has physical properties which make it desirable for inclusion in building materials but poses serious health risks when dispersed into air and inhaled.
Chrysotile fibres have a considerable tensile strength and may be spun into thread and woven into cloth. They are also resistant to heat and are excellent thermal, electrical and acoustic insulators.
Chrysotile is resistant to even strong bases (asbestos is thus stable in high pH pore water of Portland cement), but the fibres are attacked by acids: the magnesium ions are selectively dissolved, leaving a silica skeleton. It is thermally stable up to around 550 °C (1,022 °F), at which temperature it starts to dehydrate. Dehydration is complete at about 750 °C (1,380 °F), with the final products being forsterite(magnesium silicate), silica and water.
Asbestos is a set of six naturally occurring silicate minerals, which all have in common their eponymousasbestiform habit: i.e. long (roughly 1:20 aspect ratio), thin fibrous crystals, with each visible fiber composed of millions of microscopic “fibrils” that can be released by abrasion and other processes. They are commonly known by their colors, as blue asbestos, brown asbestos, white asbestos, and green asbestos.
Asbestos mining existed more than 4,000 years ago, but large-scale mining began at the end of the 19th century, when manufacturers and builders began using asbestos for its desirable physical properties. Some of those properties are sound absorption, average tensile strength, affordability, and resistance to fire, heat, and electricity. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement or woven into fabric or mats. These desirable properties made asbestos very widely used. Asbestos use continued to grow through most of the 20th century until public knowledge of the health hazards of asbestos dust led to its outlawing by courts and legislatures in mainstream construction and fireproofing in most countries.
Inhalation of asbestos fibers can cause serious and fatal illnesses including lung cancer, mesothelioma, and asbestosis (a type of pneumoconiosis). The concern of asbestos-related illness in modern times began with the 20th century and escalated during the 1920s and 1930s. By the 1980s and 1990s, asbestos trade and use were heavily restricted, phased out, or banned outright in an increasing number of countries.
Despite the severity of asbestos-related diseases, the material has extremely widespread use in many areas. Continuing long-term use of asbestos after harmful health effects were known or suspected, and the slow emergence of symptoms decades after exposure ceased, made asbestos litigation the longest, most expensive mass tort in U.S. history though a much lesser legal issue in most other countries involved. Asbestos-related liability also remains an ongoing concern for many manufacturers, insurers and reinsurers. On July 12, 2018, a Missouri jury ordered Johnson & Johnson to pay a record $4.69 billion to 22 women who alleged the company’s talc-based products, including its baby powder, contain asbestos and caused them to develop ovarian cancer.