Page 250 - New Trends in Eco efficient and Recycled Concrete

218 New Trends in Eco-efficient and Recycled Concrete

used (Sev, 2009). However, such use is below 5% for instance in Spain, far below
the European average of 35% in 2011 (Zabalza Bribia ´n et al., 2011).
Finally, besides the energy needed for the raw materials production, at the con-
crete plant electricity and fuel are required for mixing all the components. The
energy consumption for the operations at a ready-mix concrete plant has been esti-
mated to be 4% of the embodied energy of concrete (Marceau et al., 2007).

9.2.1.7 Waste
Solid wastes are generated during raw material production and concrete processing.
While dust is the principal waste of cement and aggregate production, wastes
derived from concrete batching include mixer washout, sludge and returned excess
of fresh concrete (Gursel et al., 2014). On average, the amount of waste generated
by the ready-mix concrete sector is up to 0.45% of the total production, with a max-
imum of about 5% 9% in times of great demand (WBCSD/CSI, 2009). According
to Marceau et al. (2007), the average amount of nonrecycled solid waste is 24 kg/
3
m . Regarding the precast concrete industry, the generation of concrete waste pri-
marily happens due the rejection of constructive elements in the quality control pro-
cedure; a study suggested that the amount of waste is around 1% 3% of the gross
production (Kaysser and Kott, 2002).
Moreover, when the complete life cycle of concrete structures is taken into
account, wastes produced during the construction, renovation and demolition activi-
3
ties (CDW) sum up to important figures. According to Ding et al. (2016),1 m of
3
concrete ends up as 0.4 m of waste in the landfill. Also, for a Spanish scenario,
3
Solı ´s-Guzma ´n et al. (2009) estimated a 0.30 and 1.27 m CDW generation for 1 m 2
of construction and demolition works, respectively. Quantitatively, the mineral frac-
tion of CDW generated in the European Union amounted 284 million tonnes in
2014 (Eurostat, 2018).
The landfilling of these wastes generates visual and aesthetics impacts and
involves land occupation which affect the terrestrial ecosystem. Although theses
wastes are mostly inert materials, which reduces the concerns regarding their land-
filling, leaching of some chemical elements can occur and pollute the soil or neigh-
bouring groundwater reserve (Kuhlman and Paschmann, 1996). Moreover, some
hazardous materials such as asbestos, lead, or polychlorinated biphenyls could be
present among CDW that can put the public health at risk.
Nevertheless, diversion of these wastes from the landfills is possible as both the
leftover ready-mix concrete and concrete slurry wastes have potential for recycling
within the concrete sector, including the reutilisation in new concrete mixes
(Chatveera et al., 2006; Correia et al., 2009; Kou et al., 2012), cement mortars
(Zervaki et al., 2013) and partition wall blocks (Hossain et al., 2017b). Similarly,
the recycling potential of the precast concrete rejects has also been proven (Pedro
et al., 2014; Soares et al., 2014; Thomas et al., 2016). Regarding CDW, and as pre-
viously stated, the reutilisation of CDW as recycled aggregates in concrete is seen
as a symbiotic practice with twofold environmental advantages: (1) it reduces the
use of natural resources; and (2) it avoids landfilling.