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of materials, whether they are recycled, reused, or land filled. The avoided impact by the EOL
of reinforced concrete being smaller than that of the treatment necessary to crush it, the EOL
of reinforced concrete downgrades the overall impact of bridges. On the contrary, the other
steel elements (sections, plates and studs) avoid environmental impacts and improve globally
the profile of the bridges.
In the case of the composite bridge, recycling of steel reduces the emissions by 10% (32
tCO
2
eq) savings which are equivalent to 246.000 km driven by a car emitting 130 gCO
2
/km
[16].
The conclusion of this work shows clearly that the composite bridge has significantly
smaller environmental burdens than the other bridge: this directly related to the use of steel
in the first bridge. Moreover, the difference is very large: 40% to 70% depending on the
indicator.
Another interesting result of this work is that recycling does not necessarily reduce the
environmental burdens as the cost of recycling may be higher than the benefits it brings. A
material like steel, the recycling of which avoids using virgin iron ore, should thus always
be recycled - and indeed it is in general recycled to a very high level (more than 80%). A
material like concrete, which is recycled as an aggregate, i.e. a low energy low greenhouse
gas material, generates more burdens by recycling than by land filling. This is true of primary
energy use and CO2 emissions, but is even more significantly true of ODP, AP, HTP, FTP
and MTP.
When designing a bridge, it is essential to carry out an LCA and to use the results to
improve on the design. Software tools such as AMECO [17], which calculates a simplified
LCA of buildings or bridges focussing on energy and greenhouse gases, help to achieve this.
References
[1] ISO 14040-44: “Environmental management - Life cycle assessment - Principles and framework” and “Envi-
ronmental management - Life cycle assessment - Requirements and guidelines”; 2006
[2] PE INTERNATIONAL, “Critical review report of the method for the environmental evaluation of bearing
structures made of steel and concrete”, 2010
[3] J.-B. Guinée, “Handbook on Life Cycle Assessment”, P GUINEE, 2001
[4] A.-L. Hettinger, F. Labory, Y. Conan, “Environmental assessment of building structures made of steel or
concrete”, 2010
[5] WORLDSTEEL, www.worldsteel.org, 2010
[6] ECSC Final Report, “Life-cycle assessment (LCA) for steel construction”, 2002
[7] SRI, “Steel Recycling Institute”, www.recycle-steel.org, 2008
[8] M. Sansom, J. Meijer, “Life-cycle assessment for steel construction”, SANSOM, 2002
[9] BIRAT, “The value of recycling to society”, 2006
[10] ZEMENT, “Bauberatung Zement - Expositionsklassen von Beton und besondere Betoneigenschaften”, 2004
[11] D. Kellenberger, H-J Althaus, T. Künninger, “Concrete Products and Processes - Ecoinvent”, ECOINVENT,
2007
[12] Jeannette Sjunnesson, “Life Cycle Assessment of Concrete” - Master thesis, LUND University, Department
of Technology and Society, September 2005
[13] INRETS, Institut National de Recherche sur les Transports et leur Sécurité
[14] PE International - GaBi databases, 2010
[15] IPCC, http://unfccc.int/, 2010
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