Rock wool – Wollastonite – Attapulgite

Rock wool, wollastonite and attapulgite are useful substitutes for asbestos.

Rock wool

Rock wool, also called mineral wool or slag wool, is manufactured from a molten rock mixture or from molten slag, by flowing the pouring melt with a blast or air or steam. The fibres vary in length from 50 micrometers to 50 mm and they are not of uniform diameters. These fibres are brittle and their energy content is quite high. Rock wool is not alkali resistant and is therefore unsuitable for fibre-cement products. However it is suitable for bulk thermal insulation. It cannot be woven into textiles but it can be formed into felts used for flooring underlay. The latter lack homogeneity, yield relatively rough surfaces and lack durability.

The cost of rock wool is in the order of 0.34 10 0.42 $/kg, or about thee times the cost of short chrysotile asbestos.

Compared with cluysotile asbestos, rock wool is adequate with regard to a availability, cost, heat and chemical resistance. It is not as strong, flexible and soft.


Wollastonite is a naturally occurring acicular calcium metasilicate. Its fibres have a diameter of 3.5 micrometers and a specific gravity of 2.9. It’s cost is around 2.00 $/kg.

It is used as a substitute for asbestos in latex sheet roofing, and as a thixotrope in asphalt-based paints for driveway bituminous pavements. It is also used as filler for plastics, composite papers, flooring felts, thermal insulation, and in ceramic compounds.


Attapulgite is a naturally occurring fibrous clay (a crystalline hydrated magnesium aluminum silicate) that is used as a substitute for asbestos in friction materials, as a thickener in caulks, grouts and sealants, as a viscosity control agent in drilling muds, and as a carrier for pesticides. Its cost is in the order of 1.00 $/kg.

When used in friction products it is found to be abrasive and to cause rotor wear.

Substitutes for asbestos – Marcel Cossette