Sustainable Construction A Life Cycle Approach in Engineering

2.2 Existing research of Life cycle assessment for bridge
Nowadays, the increasing transportation demand has concerned people to look into the
environmental performance of different transportation infrastructures in a life-cycle
perspective. Although LCA has been widely applied in industrial domain, there is limit
implementation in bridge infrastructure field, thus it has high potential for the further
research. A literature review of the studies focused on the environmental assessment of
bridge infrastructure is presented in the following part.
D. Collings (2006) compared the embodied energy and CO2 emissions for three basic bridge
forms: cantilever, cable stayed and tied-arch bridge. For each bridge type three material
alternatives were considered: steel, concrete and steel–concrete composite. The assessment is
performed for the construction process and the operation process in 120 years assumed life
span of the bridge. Result indicated that the consumption of the embodied energy increases
with the span length. The well engineered longer span bridge can be almost as environmental
friendly as shorter span bridge which has no environmental consideration. The architectural
solutions have a higher environmental burden for the same bridge forms. The CO2 emission
is almost the same for three bridge materials during the operation process.
In order to improve the environmental performance of concrete infrastructure, Gregory A.
Keoleian, et al. (2005) applied a comparative life cycle assessment (LCA) of two bridge
deck systems over a 60 years’ service life. One deck system is containing the conventional
steel expansion joints, while the alternative one is a link slab using the engineered
cementitious composite (ECC). ECC is an alternative promising material for extending the
service life and reducing the maintenance activities. The results of LCA model indicate that:
the ECC bridge deck system has significant advantages for all pollutants categories.
Compare to the conventional joints, the consumption of life cycle energy for ECC is 40%
less, the generation of solid waste decreased 50%, and the raw material consumption is 38%
less. The construction related traffic congestion is the greatest contributor to most life cycle
impact categories.
Lee et al. (2008) applied the life cycle assessment method on two rail track systems: gravel
ballast and the concrete track system. Those track system are constructed between Seoul and
Busan in South Korea. The analysis compasses the whole life-cycle of the system from the
raw material extraction to the maintenance activities, within a service life of 20 years. The
result shows that the ballast track system had a better environmental performance than the
concrete track system. The major environmental contributor was the ties, the fasteners and
the ballast for the ballasted track, and the ready mixed concrete, the ties and the fasteners for
the concrete track.
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