Bitumen Based Materials

Basic info is found in Chapter 9.

Bituminous products have good waterproofing qualities and are often used for waterproofing membranes in both the exterior and interior of a building, as well as in roof coverings. The first known building-use of bitumen can be traced back about 5000 years to the Indus valley, where it was used to make a temple pool watertight. This fatty and water-repelling material is also often mixed into other building materials that are exposed to moisture such as perlite insulation and wood fibre wind barriers. Coal tar was once used instead of bitumen - such products are no longer in use.

For use as a waterproofing membrane, it is common practice to first oxidize the bitumen mass by blowing air into it. The material is then

14.15

Cabins partly buried in a sensitive area along the south coast of Norway. The materials and structures have been chosen with respect to the local climate and properties in earth and ground water. The aim has been to reduce the physical and chemical traces of the buildings to a minimum when they eventually fall to ruin. Gaia Lista, 1997.

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Cabins partly buried in a sensitive area along the south coast of Norway. The materials and structures have been chosen with respect to the local climate and properties in earth and ground water. The aim has been to reduce the physical and chemical traces of the buildings to a minimum when they eventually fall to ruin. Gaia Lista, 1997.

heated and applied directly onto the surface, e.g. a foundation wall. Solvents can be added to give a more workable consistency. A filler such as crushed limestone or sand can be used. Waterproof sheeting is produced by coating a base product of polyester, fibreglass, rag fibre or paper with bitumen. Small granules of ground stone can be added to give a more resistant surface. Bituminous mastic for making joints watertight consists of a solution or emulsion of bitumen with fine stone powder or synthetic rubber. The mixture contains high levels of solvents.

Bituminous products do not have a long lifespan if they are exposed to a combination of sunlight, large variations in temperature and a lot of damp. They can also be attacked by acids found in soil. When protected from these conditions they can be very durable.

Bitumen is derived from fossil oils, in particular the heavy fractions of crude oil. The production of bitumen-based materials is therefore unsustainable, intensive in its use of energy, and also causes pollution -however, on a somewhat lesser scale than that of oil-based plastic products.

Heating bitumen on a building site emits dangerous fumes: polycyclic aromatic hydrocarbons (PAH) amongst others, though the amount of PAH in bitumen is considerably lower than that in coal tar. Some of the products contain organic solvents (see Table 9.4), which are also easily emitted even in a cold state.

If bitumen products are exposed to heat or sunlight, fumes can be released into a building. Bitumen products cannot usually be re-used or material recycled. For enhanced recycling of adjoining components in concrete or timber, loose membranes are preferable to membranes poured in situ. Both bitumen and coal tar contain substances that are the initial stages of dioxins, which can seep out; waste products should therefore be carefully disposed of (Strunge etal., 1990).

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