Unused and discarded electric cables from decommissioned energy plants as the source of secondary raw materials?
It’s the idea behind an Italian project, funded under the European Regional Development Fund and led by R.ED.EL. SRL, an Italian company operating in the construction and maintenance of medium-low voltage electrical, is working in collaboration with the University of Calabria, for and ENEA, the Italian National Agency for New Technologies, Energy and Sustainable Economic Development.
The project is targeted at cables consisting mainly of copper, aluminium and PVC protective sheaths, and is studying how the PVC can be recycled into powder and granules for use in new civil engineering applications. Two different applications were investigated and tested: the first, in urban tiles; the second, the use of PVC compound as reinforcement in cement-based mortars.
For the manufacture of the tiles, a standard-mix design made of 90% of PVC powder and 10% of polyurethane resin was selected, in order to achieve a finished product with a density similar to that of the reference tile, made without rPVC. The components - PVC powder and a thermosetting polyurethane resin - underwent a three-step mixing process to ensure a homogeneous and uniform mix.
This yielded, at the end of the curing phase, a good specimen, in terms of surface flaking, density reached, and size (20×20 cm). The final product maintained adequate mechanical strength and surface abrasion.
Five different mortars were obtained through the volumetric substitution of the sand, which is normally used, by plastic waste, in percentages ranging from 10% to 50%.
The waste materials used for the PVC mortar samples were derived from R.ED.EL.’s operations. End-of-life PVC copper cables were ground up, after which the metal was separated out. All of the mortars exhibited a thermal conductivity coefficient that was lower than the reference mortar.
Mortars containing plastic aggregates were also found to offer improved thermal insulation properties compared to conventional mixtures, which can 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.
Note that, while replacing the siliceous aggregate by PVC residues somewhat reduces the mechanical properties, these mortars remain eminently for the huge number of applications without a structural function.
It was also found that incorporating various types of plastic aggregate could improve the permeability behaviour of cement-based composites, making them more durable in case of aggressive chemical agents and for effect of weathering environment.