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Geotetechnical Usage - Ashes in roads, constructions etc.

Ash use
Applications: Geotechnical

Energy ash may be used as a durable building material in many different constructions like roads, parking lots, industrial floors and work surfaces. In the production of mainly soil concrete, ash can replace cement, which also reduces carbon dioxide emissions in the construction industry. 

Today, only a small part of the energy ash is used as construction material for roads and surfaces, but the potential is considerably larger. Research shows that ash works very well in various construction projects, both technically and environmentally.

More environmentally friendly concrete
In the manufacture of concrete, energy ash may play an important role. A new, greener recipe for plain concrete is now being used where fly ash replaces cement. This makes the concrete less expensive and more environmentally friendly. Partly because the ash is reused and partly because cement production is very energy intensive, and partly that the process itself releases CO2.

The new, green plain concrete is now being used successfully. In Västerås, the municipal energy company has regained ash from the district heating plant for the past 20 years, thereby saving millions of Swedish crowns. The ash has been used to build parking lots, industrial flooring and large work surfaces for containers. The advantage of ash concrete is that it is very durable and functions as a bearing layer for soft clay.

Many years of research
Several research projects in the past few years have tested the technical characteristics of the ash and how they affect the environment, for example when building roads. The results have been positive and today, several roads have been built with ash. For example, parts of the motorway at Norrköping (E4) consists of energy bottom ash as a replacement of light weight ballast

Research shows that roads with ash as the bearing layer are more frost resistant and thus require less maintenance. The ash, however, should not be used on the road surface, because it is not sufficiently durable because of the risk of dusting.

Sustainable roads
Roads can also be built using  bottom ash, in this case a kind of improved bottom ash from household and industrial waste. It consists, apart from ash in various sizes, of stone, gravel, porcelain, glass and metal. Much of the metal has previously been separated from it.

Research shows that bottom ash has very little impact on the environment in terms of leaching of metals. This has been documented in a decade-long research project in Umeå, where a test road was built near the district heating plant. Both Swedish Geotechnical Institute(SGI)and Luleå University of Technology have taken measurements. SGI and Universtiy of Stockholm (MTI) have also found that leachates from most ashes including MSWI-bottom ashes are not ecotoxical due to ecotoxical elements.
Correctly used, bottom ash can play an important role as a substitute for natural gravel and crushed rock in road construction. Instead of making new interventions in nature, recycled bottom ash can be used to build smaller roads, preferably near district heating plants.

Bottom ash also can be used as filler for the closure of pipes. In this case, a more powdery bottom ash is used. Fly ash provides more frost resistant and stiffened roads and can advantageously be used to stabilize weak materials to premium construction materials. Port construction environmentally safer and cheaper with ash

Energy ash can solve the problem of contaminated dredged material when rebuilding ports. When ash is mixed in, the heavy metals are bound and the dredged material can be reused as building material in the port.

Many ports around the Baltic Sea have to dredge their entrances to become safer and to be able to accommodate increasingly larger vessels. A major environmental problem when ports are rebuilt is the bottom sludge, much of which contains hazardous substances such as heavy metals. The contaminants are a result of earlier emissions from industries and transport. During the next few years, hundreds of thousands of cubic meters of contaminated sediment will have to be dredged at ports around the Baltic Sea.

Saves 500 million Swedish crowns
Several ports now are using a new dredging technique with energy fly ash as an important ingredient. The technology is both environmentally safe and considerably cheaper than the traditional one.

In Sweden, the port of Gävle has received permission to test the technology. This means that ash from district heating plants is mixed into the dredged material together with cement and other binding agents. This binds the pollutants firmly in the dredged materials and prevents them from leaking. Also, a new, solid building material is created and can be used for constructions in building the port.
Using ash as a solution saves both the environment and big money. The port of Gävle expects to reduce the costs for the port construction with 500 million Swedish crowns compared with having carried it out the traditional way.

Usually, the contaminated dredged material has to be excavated and placed in landfills, which is very expensive. This procedure also requires both transport and structure surfaces. With the new technology the dredged material can be returned in the expansion of the port and replace natural resources such as crushed rock, sand and gravel.

New practises for sustainable port construction ( En del upprepningar mot ovan men det kanske passar in I broschyren)
The method of binding pollutants in the dredged material instead of having it excavated and replaced has been used for many years worldwide. In recent years, this technology also has been tested in the Nordic countries. Both the port of Gävle and the port of Kokkola (Karleby) in Finland are part of a three-year pilot project, funded by the EU. Other countries participating are Germany, Poland and Lithuania. To replace part of the construction cement with energy fly ashes reduces an important margin of the costs.

The project, led by Swedish Geotechnical Institute in Linköping, is now in progress, developing a practice for how to handle the contaminated dredged materials in a safe and sustainable manner in the entire Baltic region.






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