Materials discarded in construction, demolition and refurbishment activities of buildings represented the most abundant type of waste by volume in the EU in 2018(1). Even though this waste can formally be used as raw material for the manufacture of new recycled construction materials, it has a low recycling rate mainly due to the difficulty in its separation and classification, which is translated in its use in activities with low added value such as road filling. The valorisation of this waste through its classification would favours the ecological transition towards an economy of zero-by-products practice, making a circular economy possible. That is why government organizations support practices that favour the use of this waste as raw material(2). Within the construction sector, ceramic materials such as tiles are widely used as a wall and floor covering as well as structural materials such as bricks. The ceramic industry already practices the reuse of discarded pieces and other by-products, adding them as raw material in the manufacture of the same tiles(3). That is why the use of construction and demolition waste (CDW) materials is pursued for the manufacture of recycled circular ceramic tiles. The main handicap in this practice is the classification of this waste that allows adjusting the formulation of the tiles, since now, the source of recycled construction materials is variable and unknown, compared to the recycling practiced to date. Currently CDW are classified manually and the investigations that pursue their classification in a continuous and automated manner are mainly based on short-wave infrared (SWIR)-based hyperspectral spectroscopy(4). This study proposes a methodology for the valorisation of these residues through their homogenization and subsequent classification using chemometric with Raman and SWIR spectroscopies. The proposed strategy begins with the homogenization of the residue through a high-efficient grinding process. This homogenization makes it possible to have a material that is representative of the waste while being integrated into the subsequent recycling process, since the necessary granulometry of the material to be used as raw material in new tiles is obtained. Then, it is classified using chemometric prediction models designed for the classification of brick and concrete, the main components of this waste. These models were built using principal component analysis and a quantification model applying improved Kernel partial least square discriminant analysis from controlled mixtures of the materials of interest.  Moreover, this study provides the first use of Raman spectroscopy for this purpose, offering advantages over other used spectroscopies such as simplicity of measurement, little or no sample preparation, and directly providing structural data on the material. Once classified using this technique, the material can be mixed to reach the necessary formulation for the manufacture of new recycled ceramic tiles, thus valuing a material with no added value to date.

1.Eurostats. Waste statistics. Waste generation, 2018. 2021.
2.European Commission. A new Circular Economy Action Plan For a cleaner and more competitive Europe. 2020.
3.Andreola F., Ceram Int. 2016
4.Hollstein F., Chemical, and Biological Sensing Technologies XIII. 2016.