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TOXICITY OF RECYCLED CONCRETE AGGREGATES: LEACHING TESTS
Margarida Braga Maia, Jorge de Brito, Isabel M. Martins, José Silvestre
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Keywords: Eluate, Leaching, Recycled concrete aggregates (RCA), Sustainability, Toxicity 1. Introduction
The toxicity of building materials can be addressed in the areas of occupational and environmental toxicology. In the first case, the harmful effects to workers caused by exposure to a specific substance during building materials production are analysed. In the latter case, the toxic effects of that substance on living organisms in the biosphere is examined.
From an environmental perspective, only a few studies are focused on toxicity assessment. Some of the traditional constituents of concrete may be potentially hazardous, presenting different levels of toxicity. Still, and in order to reduce its potential environmental impact, studies on the incorporation of alternative raw materials have already started, which may affect concrete’s toxicity (Roque et. al., 2016).
Depending on their origin, recycled concrete aggregates (RCA) from construction and demolition waste (CDW) have different characteristics (Bestgen et. al., 2016). If the recycling plant does not carry out an adequate management, CDW can be contaminated, impairing their recovery as aggregates (Saca et. al., 2017).
The use of recycled aggregates has been evaluated in several applications, namely when in direct or indirect contact with soil and groundwater. Leachates resulting from the leaching of the aggregates can toxically affect all the surrounding elements, and may put ecosystems and human health at risk (Directive 2013/39/EU). Thus, the exhaustive characterization of the RCA eluates and of the concrete incorporating them is essential (Engelsen et. al., 2010; Newman and Unger, 2003; Butera et. al., 2014).
The ecotoxicological characterization of materials is based on the analysis of the eluates resulting from leaching tests, comparing the released contents with the legal limits defined in national or international legislation.
Several researchers apply different experimental leaching procedures according to existing standards, while others change the standard test conditions, in particular particle size and duration of the test.
Most leaching tests are performed in laboratory to reduce costs, and to guarantee an easier control as well as faster results (Van der Sloot et. al., 1997).
2. Conclusions
• Considering RCA’s heterogeneity, it is important to analyse their eluates and check whether they are appropriate for the intended use and comply with existing legislation;
• Leaching tests’ results depend on the RCA’s source, size, and previous exposure, and on the l/s ratio test used;
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New Trends in Green Construction