Regarding fiber cement, we often think of gray corrugated roofing sheets that are preferred by the poor for the construction of side house, toilets or cages. In fact, fiber cement includes different types of products such as flat panels for ceilings or floors, corrugated sheets, plumbing, decorative products, wall cladding etc.
Chrysotile-cement products were invented in the late 19th century by the Austrian industrialist – Ludwig Hatschek when he mixed 90 percent of cement and 10 percent of chrysotile fiber with water and ran it through a cardboard machine, forming strong thin sheets. Fiber cement materials are often used due to many advantages such as low cost, electrical insulation, thermal insulation, fireproofing, waterproofing and light weight. It is considered as one of the most useful and popular inventions of building materials during the 20th century.
In Vietnam, the production of AC roof sheets (also known as chrysotile-cement roofing sheets) has developed since 1963. With good adaptation to the climate, living habit and farming practices of people, the material is commonly used in construction of house, barns or warehouses.
AC roof sheet is a cheap roofing material
Corrugated chrysotile-cement roofing sheets have become familiar with people through another common name. Time goes by and there has been different types of roofing materials such as concrete roofs, roof tile, corrugated iron sheets, etc., but fiber cement materials were still an appropriate choice for local people in the Northern, Central and Southern areas in terms of price.
AC roof sheets are widely used in mountainous areas.
While concrete roofs are relatively durable, difficult to crack or subside, the high price is unaffordable to many families. The beautiful and eye-catching roof tiles also have a higher price compared to average incomes of rural residents. At the same time, the light-weight corrugated iron sheet with diverse types, quick installation easily gets punctured or rusty after 2-3 years of use for cooking and breeding.
The price of roof tiles ranges from 160 to 200 thousand VND per sqm. Types of galvanized and pre-painted galvanized costs up to 80 thousand VND per sqm. Meanwhile, chrysotile-cement roofing sheets only fluctuate in the range of 40 – 45 thousand VND per sqm. Therefore, cheap chrysotile-cement roofing sheets can help the poor save lots of money.
And durability is up to decades
With the close cohesion of 90 percent cement with about 10 percent chrysotile fiber, chrysotile-cement roofing sheets have become a highly durable material. In practical application, chrysotile fiber can expand well, withstand saline salt vapor in the sea, the acidic environment in the breeding facilities, the hoarfrost climate in the mountains area or Mekong Delta, where the temperature changes suddenly many times a day.
Until now, there has not been any kind of substitute product for chrysotile-cement roofing sheets which possess these preeminent properties. Some people using galvanized plain steel sheet for roofing house and barns had to change due to the corrosion and rust after 3-5 years. In particular, this material is also not strong enough to withstand and protect the houses against rainstorms because they are lightweight, prone to winds with tens of meters.
Galvanized plain steel sheet is rusty from the effects of weather, kitchen fumes, or poultry manure.
Ms. Thai Quynh Thi, living in Village 4, Ward 7, Soc Trang City shared her experience from using galvanized plain steel sheet and chrysotile-cement sheets: “My family only can use galvanized plain steel sheet for 15 years because of its durability. We have replaced the sheet with chrysotile-cement roofing sheets”. According to Ms. Thi, many local residents still are using traditional chrysotile-cement sheets: “The whole row of inns is covered by chrysotile-cement sheets. This material is used by many other families in the village”.
Easy to transport and install
In addition to its outstanding features, chrysotile-cement roof sheets can be easily transported by motorbikes and carts to remote and mountainous villages that are not accessible by large vehicles. Therefore, the Government and organizations in the programs of hunger eradication and poverty alleviation No. 134, 167 or relief program of floods and storms often mobilize this material to help people to quickly stabilize their lives. In 2016, more than 4,500 AC roof sheets were provided to support households that suffered from the severe tornadoes and hail of Tuong Duong and Ky Son districts., Nghe An by the Vietnam Roofsheet Association and factory members.
Carcinogenicity is still just a rumor
Due to the regional characteristics and severe weather conditions, many people in remote areas still do not have tap water to use. Drilling wells in rocky areas is not feasible or highly expensive. For people in the Mekong Delta, the situation of saline and alum water forces the local people to collect rainwater from the roof to the tanks to reserve for use in the dry season. This is also a popular situation in India, where there are crises on clean water every year. Indians still have to collect water stored in chrysotile-containing tanks. In Germany or Russia, there are still thousands of kilometers of water pipes made from this material.
Fiber cement water pipes are still in use in the Russia.
According to Assoc.Prof. Dr. Luong Duc Long – Former Director of Vietnam Institute for Building Materials, Ministry of Construction, the amount of chrysotile in roofing sheets accounts for a very small proportion of the mixture. The chrysotile fibers have a hollow structure so the cement-like binder will fill them up, creating a very strong, tight, hard-to-break bond and very difficult to disperse into the environment.
Many studies to determine the level of risk of chrysotile fibers in drinking water to human health have been conducted in the world. The results showed no evidence of negative effects of chrysotile that cause cancer.
In 2002, the World Health Organization (WHO) added to the report on asbestos in drinking water in 1996 with conclusion that “Current epidemiological studies do not provide evidence of an increase in risks regarding human health of asbestos in drinking water. Furthermore, studies on animals have shown that asbestos does not increase the risk of gastrointestinal cancers. Therefore, there is no conclusive evidence that asbestos-containing drinking water is dangerous for human health. Therefore, it is not necessary to create a safety guide for asbestos in drinking water.”