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Urban solid waste from demolition and construction engineering sites has been demonstrated to be mechanically suitable for reuse in civil infrastructures. However, the application of recycled materials as a replacement for natural aggregates demands an assessment of the pollution potential of the material in its second life cycle. Actually, plant managers of construction wastes assess the materials according to concise leaching tests that do not consider the compaction stage of the materials when they are applied in civil infrastructures. For that reason, the aim of the present study is to evaluate the effect of compaction on the leaching behaviour of concrete and mixed recycled aggregates. A percolation test for materials under compaction conditions was designed. The release levels measured in the water percolated through the compacted aggregates were compared with a conventional percolation leaching test. Besides, the compliance test allowed identifying the most conflictive elements according to the measured concentrations in the leachate: chromium and sulphate. The results revealed that under compaction, the highest levels of release were obtained for the concrete material. It was due to its high susceptibility to compaction which increased the content of fine particles affecting to the leaching behaviour. The study also includes the formulation of an equation to determine the emission release time of pollutants. Calculations were developed for two common applications as granular material: embankments and structural road layers.

Recycled aggregates from construction and demolition waste have previously been used to manufacture recycled concrete. Generally, these aggregates weaken the physical properties of concrete, such as the density, durability, compressive strength, flexural strength, water penetration, and chloride penetration. This is predominately attributed to the porosity of particles with adhered mortar or to ceramic particles. In other studies, cements with additions (fly ash, slag, silica fume …) were used to compensate for the effect of incorporation of recycled aggregates. In another, plasticizers were used to improve workability or mechanical properties of recycled concrete. However, the innovation of this research is the use of different amounts of cement according to replacement ratios of natural aggregates for recycled concrete aggregates to achieved structural concretes. Also, two different water/cement ratios were used to analyse if these reached compressive strength similar to control concrete manufactured with natural aggregates. The results revealed that a small increase in the volume of cement (12%) maintained the mechanical properties and reduced the loss of concrete durability. Therefore, increasing the amount of cement in recycled concretes is a feasible technique in works with low exposure to aggressive agents.