Page 269 - New Trends in Eco efficient and Recycled Concrete

Life cycle assessment applied to recycled aggregate concrete 237

aggregates were send to landfill. Under those conditions, only for land use and
respiratory inorganics the recycled aggregate option performed comparatively bet-
ter. Contrarily, when recycled fine aggregates from CDW were also employed in
concrete manufacturing (around 10.7% and 37%, for their production in mobile and
stationary recycling plants, respectively), the environmental gain compared to a
conventional concrete could increase up to 23%. A sensitivity analysis taking into
account the transport showed that distances greater than 96 and 67 km for the natu-
ral aggregates supply are required to make the use of recycled aggregates produced
in a stationary and a mobile plant, respectively, environmentally preferable.
Moreover, it was found that stationary management plants are only preferable to
mobile plants for distances lower than 12.5 km from the demolition, whereas
mobile management plants are only preferable over the supply location of natural
aggregate for distances lower than 3 km.
Agreeing with the beneficial effect of the incorporation of fines, Evangelista
and de Brito (2007) observed improvements for all impact categories and reported
a 6.9% and 21% reduction of the global warming potential for 30% and 100%
substitution rates. Serres et al. (2016) reported lower environmental loads for
concrete made with recycled coarse and fine aggregates. This was also the case
for concrete made with recycled coarse aggregates and natural sand, in all impact
categories except for the one representing acidification, which was due to the
admixtures used, compared to the conventional concrete with the same cement
content. Kurad et al. (2017) also observed that the global warming potential
decreased about 0.02% and 0.11% per unit per cent of recycled coarse and fine
aggregate, respectively.
Kleijer et al. (2017) observed that recycled concrete performed better than
conventional concrete (differences of 2%, 4%, and 12% were observed for green-
house gases emissions, cumulative energy demand and ecological scarcity), even
when considered the dismantling of the building within the boundaries of the sys-
tem. Nonetheless, results were sensitive to transport and thus to the distance
between the construction site and the recycled concrete plant, with recommended
maximum distances ranging between 20 and 68 km depending on the impact cate-
gory or the scenario assumed. In this regard, Estanqueiro et al. (2018) specified
that the production of 1 t of recycled aggregates required 20.86 and 37.09 MJ
when traditional and selective demolition methods were used, respectively.
Meanwhile, the study of Coelho and de Brito (2012) showed that a comprehensive
selective demolition carries lower impacts (57% in acidification, 77% in climatic
change and 81% in summer smog) than the traditional method; however, partial
selective demolition (controlled demolition and recycling for nonstructural ele-
ments and conventional demolition and landfilling for the remaining structure)
could result in increasing environmental loads (less than 5%) due to additional
transport distances.
Some studies have looked at the cradle-to-cradle LCA of natural and recycled
concretes. Ding et al. (2016) observed that recycled concrete (100% replacement
ratio, 5% additional cement and superplasticiser) presented a 6.32% and 3.28%
increase in global warming potential and cumulative energy demand and a