Page 362 - New Trends in Eco efficient and Recycled Concrete

Equivalent functional unit in recycled aggregate concrete 317

Braunschweig et al. (2011) performed a LCA in order to study and identify eco-
logical optimisation potentials of aggregate production and developed scenarios for
ecologically optimal production of aggregates and concrete for construction pro-
jects. The reuse of RCA in the production of concrete proved to have higher envi-
ronmental benefits than their disposal. However, the feasibility of producing RCA
concrete mainly relies on the wastes’ transport distances.
De Schepper et al. (2014) LCA results suggested that, when compared to con-
ventional concrete, the use of RA can reduce the global warming potential (GWP)
of this material.
Sjunnesson (2005) concluded that the GWP of concrete is highly affected by raw
material production and, along with other indicators (Eutrophication Potential, EP,
Acidification Potential, AP and Photochemical Ozone Creation Potential, POCP),
depends on transportation operations. He also showed that the environmental load
is linearly related to transport distances. By decreasing the transport distances by
40%, the transport operation’s environmental impacts (EI) decreased by 63%,
which became approximately equivalent to the EI of the raw material production.
Estanqueiro et al. (2018) performed a LCA on RA used in the manufacture of
ready-mixed concrete, and also on the calculation and comparison of the corre-
sponding EI. However, results also showed that the assessment was very sensitive
to the transportation distances.
Evangelista and de Brito (2007b) obtained the EI from fine NA and RCA con-
crete at product and construction stages, use and end of life, in a ‘cradle to grave’
LCA by using EcoConcrete software. They found that the EI (Abiotic Depletion
Potential, ADP, GWP, Ozone Depletion Potential, ODP, AP, EP and POCP)
decrease between 6% 8% and between 19% 23%, when 30% and 100% of fine
NA are replaced with fine RCA, respectively.
Braunschweig et al. (2011) showed that the EI of high quality RCA concrete
with 25% of RCA, and NA concrete, are similar if the cement content of the first is
only slightly higher. They also showed that the contribution of NA and RA produc-
tion for GWP, AP, respiratory effects, energy use, gravel use and land use is below
10% in concrete EI. According to Knoeri et al. (2013), impacts from NA and RA
concrete mixes can be similar when the additional cement content of RA concrete
is below 10%. Furthermore, these authors took into account the advantages from
recovered steel scrap and eliminated impacts of waste disposal into the LCA to
make the analysis more beneficial for RCA concrete.
Marinkovi´ c et al. (2010) compared the EI caused by the production of two types
of ready-mixed concrete (one NAC and the other RAC) with two transport scenar-
ios. The distance between concrete plant and NA and cement production sites was
considered to be 100 or 150 km. The distance between concrete plant and RCA pro-
duction sites was considered to be 15 km in the first scenario and 100 km in the
second. It was found that, in the Serbian context, the EI of NA and RCA concrete
are highly dependent on travel distances and transport type of aggregates between
recycling plants and construction sites. Moreover, Marinkovi´ c et al. (2010) reported
similar EI for NAC and RCA concrete with 100% of coarse RA and 3% additional
cement, when transport distances of RA are smaller than that of NA.