Saturday Dec 14, 2024
Saturday Dec 14, 2024
Wednesday, 7 February 2018 00:00 - - {{hitsCtrl.values.hits}}
Asbestos is in fact a set of six naturally occurring silicate minerals, which comes under two contrasting groups viz. Serpentine and Amphibole. Serpentine group consists of only Chrysotile, while Amphibole group comprises Crocidolite, Amosite, Anthophyllite, Tremolite, and Actinolite. While other varieties of asbestos have ceased to exist in the commercial world, Chrysotile continues to be used by 150 countries across the world including the USA, and is used by two thirds of the world populace.
Due to the growing concerns raised by various factions on the use of asbestos, representatives of the world’s major Chrysotile exporting mines signed an agreement, where they pledged to supply Chrysotile fibre only to those companies that demonstrate compliance with national health and safety regulations. Accordingly, the International Chrysotile Association devised the specific standards, technologies, and work methods pertaining to the relevant compliance, and this is collectively known as the ‘controlled-use of Chrysotile’.
According to the recommendations of the WHO experts, the controlled-use of Chrysotile allows the continued use of Chrysotile in high-density products that comply with the permissible exposure limit of 0.1f/cc or below. Furthermore, following the discovery of carcinogenic properties in Amphibole (Blue) Asbestos, both epidemiologically and toxicologically, Amphibole is no longer used for commercial purpose. A convention held by the WHO in 1989 convening international experts further declared to prohibit the use of these varieties of asbestos; however, it further allowed the controlled and regulated use of Chrysotile within the permissible exposure limit of 0.1fiber/ml in the workplace.
Locally, the term Asbestos is hackneyed and synonymous with the roofing sheets. Sri Lanka only uses Chrysotile (white asbestos), which is very much less hazardous in comparison to Amphibole varieties.
Sri Lanka began manufacturing Chrysotile fibre cement roofing sheets since 1954, and even after a lapse of seven decades Chrysotile roofing sheets by far surpass their major counterparts in terms of quality, durability and affordability traits.
A Chrysotile fibre cement roofing sheet contains only 8% of Chrysotile fibres, while the remaining 92% is made of cement and water. A thin layer of Chrysotile fibres is tightly encapsulated within a matrix of high density cement mixture, leaving no room for Chrysotile fibres to be exposed.
These roofing sheets have a number of advantages over its competitors. One of the key distinctive features of Chrysotile cement roofing sheets is its strength, resulting from the strong bonds created between Chrysotile fibres and cement. Studies have shown that the tensile strength of Chrysotile cement roofing sheet is higher than that of steel. Chrysotile roofing sheets are not only heat, fire and electric resistant, but are also chemically neutral, producing no detectable odour.
Since Chrysotile is a natural mineral, the roofing sheets do not cause any harm to the environment. Furthermore, Chrysotile fibres do not permeate through soil, and are not soluble in water; hence they do not pollute water or change the pH level of water. And unlike other roofing products, Chrysotile cement roofing sheets do no crumble into fragments when removed or discarded.
Chrysotile roofing sheets do not require special protective coating, and also possess the ability to withstand inclement weather as well as strong winds. Due to its robustness and unique strength, Chrysotile cement roofing sheets have more than 50 years of durability. The material is not only soundproof but also non-flammable, making it an ideal and safe roofing solution for residences, enterprises as well as plants.
