Page 37 - New Trends in Green Construction

EFFECT OF COMPOSITION OF MIXED RECYCLED AGGREGATES ON PHYSICAL- MECHANICAL PROPERTIES
Antonio López-Uceda, Pilar Muñoz-Moreno, Enrique Fernandez-Ledesma, José Ramón Jiménez.
Keywords: Circular economy, mixed recycled aggregate, physical properties, statistical analysis. 1. Introduction
The use of secondary raw materials like construction and demolition waste (CDW), which amounts to a third of the total waste generated in the EU, face the environmental demands required by European policies (Directive 2008/98/EC). However, the recycling rate in Spain is far from the target established (70%) by the Directive for 2020, having one of the lowest ones (European Commission, 2011). CDW after being processed in a recycling plant becomes recycled aggregates (RA). The main components of the RA are unbound natural aggregate (Ru), concrete (Rc1), masonry mortar (Rc2), ceramic particles (Rb), and, to a lesser extent asphalt, gypsum, glass, plastic, wood, and metals among others. Generally, there are two main RA from CDW according to their nature; one from demolition of concrete (RCA); and other from demolition and rehabilitation of buildings called Mixed Recycled Aggregate (MRA), with a heterogenous composition. In Spain, the latter represents 70-80% of the total RA produced.
Authors like Silva et al. (2014) and Barbudo et al. (2028) classified RA according to their composition and their mechanical-physical properties such as density, water absorption and Los Angeles tests. These classification does not distinguish between concrete and masonry mortar components.
The aim of this study has been to have a deeper understanding of the influence of RA´s components on physical-mechanical properties of RA. For this purpose, different RA were collected and each of their components were tested separately.
2. Materials and methods
Different aggregates from five recycling plants were studied: eight MRA and six RCA samples. Four crushed natural aggregates (CNA) with different nature (siliceous, granite and limestone) were used as reference. The main components of RA (Rb, Ru, Rc1, Rc2) were separated in laboratory. The following physical-mechanical properties were tested: dry density and water absorption after 24 hours (UNE-EN 1097-6: 2014), resistance to fragmentation by Los Angeles Test (UNE-EN 1097-2: 2010) and aggregates compressive strength by the Aggregate Crushing Value (ACV) (BS 812-110:1990).
3. Results and conclusions
One-way ANOVA (Statgraphics Centurion XVI) was conducted on each test result to check the component factor influence This factor had five levels, one for each main component (Rb, Ru, Rc1, Rc2) and the corresponding to the CNA. As expected, the p-value of the F-Test were less than 0.05, with a confidence level of 95%, for the component factor on the test results, meaning there were statistically significant differences between the mmean values. Figure 1 shows Fisher’s Least Significant Difference (LSD) tests to check whether there was a significant difference
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New Trends in Green Construction