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APPLICATION OF MIXED RECYCLED AGGREGATES IN CONCRETE FOR BIKE LINE DITCHES
Antonio López-Uceda, Jesús Ayuso, José Ramón Jiménez-Romero, Antonio Jesús González
Keywords: Sustainability, mixed recycled aggregate, mechanical performance, low cement content, ditch. 1. Introduction
Regarding the increase in environmental awareness, the integration of the use of secondary raw material like construction and demolition waste (C&DW) face the environmental demands by European policies (Directive 2008/98/EC). Spain has one of the lowest CDW recycling rates in the EU (10-15%). Indeed, recycling rates of EU member states vary between 10 and 90%, with an average of 46% (European Commission. 2011), which is far from the 70% target established by the Directive for 2020.
Generally, there are two main Recycled Aggregates (RA) from C&DW; one from demolition of concrete (RCA); and another one from the demolition and rehabilitation of buildings, which is called Mixed Recycled Aggregate (MRA) with a heterogenous composition. In Spain, the latter one represents 70-80% of the total recycled aggregate (RA) produced.
The most common applications of MRA are normally for road layer construction such as backfilling, subgrade, subbase and base. In Spain, the regulatory framework that sets the concrete requirements (Structural Concrete Code EHE-08) forbids the use of MRA in concrete. The use of MRA for non-structural applications with low cement content such as ditches, ground slabs, levelling surfaces, subgrades for foundations and similar civil works could contribute to the sustainability of construction sector. Hence, this research tries to prove the feasibility of using MRA as coarse fraction in non-structural concrete applied in a ditch of a bike lane (Figure 1). Samples were casted during the pouring concrete, and mechanical and capillarity tests were conducted on the samples after curing.
Figure 1. Location of ditch of recycled aggregate concrete and placing detail.
2. Materials and methods
Natural siliceous sand (NS), with a maximum size of 4 mm, and Portland cement-type CEM II/A-V 42.5 R, were used in the two mixes. Two types of coarse aggregate with similar particle size distribution were used: a siliceous gravel (NG) and a mixed recycled aggregate (MRA) from a recycling plant of CDW, which was used exactly as it came out of the plant. A plasticizer (Pl.) and a superplasticizer (Spl.) were used to reduce the water content and increase workability. A nearby ready-mix concrete plant supplied the two concrete mixes (Table 1).
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