Sustainable bridges –LCA for a composite and a concrete bridge - Economical Bridge Solutions based on Innovative Composite Dowels and Integrated Abutments - page 42

Production phase
The GWP of the production phase is dominated by concrete production for case A, and by
steel production for case B, which respectively accounts for 60% and 69% of the impacts.
Comparatively, the composite bridge production (330 tCO2eq) generates 43% less GWP than
the prestressed concrete (580 tCO2eq).
End-of-life phase
As explained in 4.2 and 4.3, a credit is given to materials that are reused or recycled at their
end-of-life.
For the composite bridge, recycling of steel avoids 32 tCO2eq and reuse of concrete
0.2 tCO2eq. This is compensated by the impacts linked to the dismantling of the bridges,
the treatment before reuse (separation of concrete and rebars) and the landfill (22 tCO2eq).
Altogether, the EOL phase of the composite bridge has a negative value (-10 tCO2eq) and
thus slightly decreases the overall life cycle GWP of the bridge.
On the other hand, for the prestressed concrete bridge, the GWP of the dismantling,
separation of concrete and steel and landfill (78 tCO2eq) is larger than the credit provided
by recycling (1 tCO2eq). As a result, the EOL phase of the prestressed concrete bridge has a
positive value (77 tCO2eq) and thus increases the overall life cycle GWP.
These results are sensitive to a change in EOL assumptions; therefore another scenario
was tested to evaluate the effect of a 100% recycling of reinforcing steel and concrete. In this
scenario, all reinforced concrete needs to be crushed. In that case, the recycling compensates
the burden of sorting only because of the recycling of steel while the benefit of recycling
concrete is not high enough.
Altogether, for the two bridges, the EOL phase has a much lower contribution to the life
cycle GWP than the production phase.
Life cycle results
The production phase (from extraction of raw materials to semi-finished products) is the
main contributor to the GWP. This is also true for seven of the other indicators, except for
ozone depletion (ODP), acidification (AP), human (HTP), marine (MTP) and freshwater tox-
icity (FTP) where the EOL phase contributes much more to the overall results. This is related
to the treatments in the sorting plant which has a large effect on these particular indicators.
Finally, the contribution of transportation of concrete and steel elements represents a
rather low share of the overall GWP results, respectively 4% and 7% for the prestressed con-
crete bridge and the composite bridge.
6. Conclusions
There is a direct connection between the mass of the bridge as shown in the bill of quanti-
ties and the environmental burdens. The heavier concrete bridge has a significantly higher
burden.
The production phase is more important than the end-of-life phase and the transporta-
tion of materials for most indicators. In addition, the end-of-life phase is sensitive to the fate