Usage of industrial sub-products - flyash

The fly ash issue is the subject of three articles:

• [C 5 373] to find out more about the origin, nature and properties of fly ash, as well as the sources of its production;

• this one, [C 5 374] , is devoted to the wide range of possible uses for fly ash, and to the environmental aspects of these uses;

• Although references to recently completed projects are given here, some will be the subject of detailed presentations in the article [C 5 375] .

The use of fly ash in the construction industry, which dates back to the 1960s, is still going strong. For economic reasons, fly ash is used close to production sites, making it an ideal technical solution.

Ash comes from existing stocks, built up during coal mining in France, and, since the closure of mining sites, from the production in thermal power plants of residues from the combustion of imported coals. Annual production of fly ash is around 1.5 million tonnes.

Fly ash –, and in particular silica-alumina ash –, can be used in a wide range of applications, mainly as a binder or aggregate. They are used in road and rail construction, at all stages of earthworks: backfill, upper earthworks platform (pst), subgrade, pavement base, the areas we will be focusing on in this dossier.

Other uses, as constituents of binders and cements, grouts and concretes, are also discussed for information purposes.

Today, most ash production is consumed by concrete and cement manufacturers.

The recovery of fly ash is encouraged, as it is a much better solution – environmentally and economically – than its disposal as waste. Fly ash is a non-hazardous waste, according to current regulations.

The environmental aspect of ash...