Separating Construction Waste into High-Quality Materials

Abstract

The construction industry is a major contributor to waste generation, with construction and demolition waste (CDW) constituting a significant portion of it. This research is centered on developing a technology to separate and recycle two types of plastics, EPS and PU, from cement matrices, along with recycling the cement itself. The goal is to recover high-quality materials for reuse within the construction sector, thereby promoting sustainable practices and enhancing the circularity of construction materials.
The research involved two classes of samples: samples containing cement and PU foam (Class
A) and samples containing cement and EPS foam beads (Class B). Different separation methodologies were employed for each class.
Class A samples underwent mechanical crushing and sieving, followed by electrostatic separation using a vertical triboelectrostatic separator.
Class B samples were successfully separated using mechanical milling and sieving.
The separated PU foam, due to a reduction in particle size during separation, could not be directly reused as insulation. Therefore, it was analyzed using Fourier-transform infrared spectroscopy (FTIR) to assess its quality for recycling into new polyurethane foam products. The FTIR results confirmed the effectiveness of the separation process, yielding clean polymer suitable for reintroduction into the market as a secondary raw material, particularly for particles smaller than 500 μm.
The separated EPS foam beads were reused to cast new insulating cement, and its thermal conductivity was tested. The results demonstrated that the separation process did not compromise the insulation properties of the EPS beads, allowing for their reuse in their original application.
The recycling potential of the separated cement powder was also analyzed. Chemical composition analysis, particle size distribution, and loss on ignition tests indicated its suitability for reuse as a partial cement replacement in new mortar samples. Mechanical tests on mortar samples with varying percentages of recycled cement powder (15% and 30%) and different reactivation temperatures (650°C and 750°C) showed a slight decrease in compressive and flexural strength compared to the reference mortar, particularly for the 650°C reactivation temperature. However, the recycled cement powder reactivated at 750°C and used at a 15% replacement ratio resulted in a 2.75% increase in compressive strength, highlighting the potential for optimizing the recycling process to achieve comparable or even enhanced performance in construction applications.