Page 25 - New Trends in Green Construction

RECYCLING OF ‘ALPERUJO’ (OLIVE POMACE) AS A KEY ADDITIVE IN THE MANUFACTURE OF LIGHTWEIGHT AGGREGATES
José Manuel Moreno-Maroto, Manuel Uceda-Rodríguez, Carlos Javier Cobo- Ceacero, Teresa Cotes Palomino, Carmen Martínez García,
Jacinto Alonso-Azcárate
Keywords: alperujo, olive pomace, lightweight aggregates, Circular Economy, waste recycling 1. Introduction
The circular economy model is based on the intelligent reuse of waste, so that it becomes a raw material to feed natural cycles or simply to be transformed into new technological products with a minimum energy expenditure (Lett, 2014). The growing concern on sustainability and environmental issues has led many researchers around the world to focus their efforts on the investigation of wastes as possible raw materials for the production of lightweight aggregate (Dondi et al., 2016). Lightweight aggregate (LWA) is a very low density granular material with enormous applications in construction, agriculture or civil and environmental engineering. The objective of this study was to recycle a waste that is widely used in the Mediterranean agricultural sector, such as the so-called alperujo (olive pomace). The aim is to find out whether this material could favor the bloating and decrease in density typical of LWAs, thus transforming a waste into a highly technological material when mixed with different types of clay.
2. Materials and methods
Both the three clays used in this study - black (BC), yellow (YC) and white (WC) - and the olive pomace (OP) came from the province of Jaén (Spain). The samples were oven-dried at 105oC and ground below 200 μm in the case of the clays and below 500 μm in the case of OP. A complete characterization of the raw materials has been carried out, including their main physical, chemical, mineralogical and thermal behavior properties. After that, mixtures containing 2.5% OP and 97.5% of each of the clays have been prepared. The material was blended with its optimum water content, and after a maceration period of 24 hours it was extruded and pelletized. The resulting granules were dried and then fired in a tubular rotary kiln for 4 min at the maximum temperature that the material was able to withstand without melting. The firing process has also been carried out on the clays without OP, in order to know how the addition of this residue affects the properties of the sintered material. A complete characterization of the aggregates has been conducted, including density, porosity, water absorption and mechanical strength tests.
3. Results and conclusions
Although for WC the addition of OP has not affected the working temperature (1180oC), OP has favored a decrease in the firing temperature of the YC and BC clays, which have changed from firing at 1205oC without OP to 1180oC and 1190oC with the residue, respectively. This would be interesting from an economic and environmental perspective, as it would mean an improvement in energy saving.
On the other hand, it has been observed that the addition of OP has affected differently depending on the clay used. In the case of BC, this is a clay that is capable of producing LWAs without the
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New Trends in Green Construction