Funded under the European Regional Development Fund (POR CALABRIA 2014-2020), the ‘PVC Upcycling’ project is led by R.ED.EL. SRL, an Italian company operating in the construction and maintenance of medium-low voltage electrical, plants in collaboration with the University of Calabria, for the management of scientific activities, and ENEA (the Italian National Agency for New Technologies, Energy and Sustainable Economic Development), in charge of testing the recycled materials performance.
The project focuses on electrical cables consisting mainly of metals (copper and aluminium) and PVC, with the objective of recycling the plastic component in potential secondary raw materials, PVC powder and granules, and in new civil engineering applications.
Two different applications were investigated: urban tiles, and cement-based mortars reinforced with PVC compound coming from electric cables protective sheaths.
For both applications, experimental investigations were carried out to verify mechanical strength, hygrothermal and durability properties.
The manufacturing of the urban PVC tiles consisted in a standard-mix design made of 90% of PVC powder and 10% of polyurethane resin.
These percentages have been fixed to obtain a density of the finished product as close as possible to the density of the reference one (made without R-PVC). The preparation of the compound took place through the mixing of components consisting of a secondary raw material (PVC powder) and a thermosetting polyurethane resin. The mixing phase was carried out in three different steps to ensure a more homogeneous and uniform mix.
At the end of the curing phase, the obtained specimen was satisfactory both in terms of surface flaking and density reached, and in terms of size (20×20 cm). Furthermore, the final product maintained adequate mechanical strength and surface abrasion.
The manufactured mortars were obtained by the volumetric substitution of the sand with five different percentages of plastic waste, ranging from 10% to 50%.
The waste materials used for the PVC mortar samples came from operations carried out at R.ED.EL. SRL, consisting in grinding end-of-life PVC copper cables (PVC-Cu) through a procedure that allowed the complete segregation of the conductive metal and the polymeric protective coating, producing fully disaggregated and heterogeneous mixture, subsequently separated.
All the mortars were prepared by substitution of natural aggregate with recycled plastic and showed a thermal conductivity coefficient lower than the reference mortar.
Moreover, mortars containing plastic aggregates had better thermal insulation properties than conventional ones, which help to control heat loss from building during winter and heat gain during summer.
The reduced thermal conductivity is also due to the low density, which depends both on the presence of plastic aggregates and on the increased induced porosity. This is an interesting reduction in the civil engineering field, where the potential amount of materials needed is huge.
Even though the replacement of the siliceous aggregate with PVC residues leads to a decrease in mechanical properties, opportunities in the use of these materials are not affected, especially for applications that do not require a structural function.
Finally, the reduction of water absorption by capillarity showed that the incorporation of various types of plastic aggregate can improve the permeability behaviour of cement-based composites, making them more durable in case of aggressive chemical agents and for effect of weathering environment.
The ‘PVC Upcycling’ project demonstrates that an innovative PVC cables recycling might generate further benefits in scientific, environmental, and economic terms, transforming a linear economy model into a circular economy one at higher added value.