Used tires can be reused after retreading. This consists of scraping off the worn tread from the carcass and placing a new tread. After vulcanization, the retreaded tire should have the same durability as the new one.
The economy of the process favors the most expensive tires, such as transportation (truck, bus, plane), because in this segment the costs are better monitored.
There are limits to the number of retreads a tire can handle without affecting its performance. Therefore, sooner or later, tires are considered unusable and discarded.
Discarded tires can be recycled or reused for a variety of purposes. In this case, the following are several options:
In civil engineering
The use of tire casings in civil engineering involves a number of creative solutions in a wide variety of applications, such as roadside barriers, park and playground construction elements, breakwaters, traffic barriers and even artificial reefs. for fish farming.
In the regeneration of rubber
The rubber regeneration process involves separating vulcanized rubber from other components and digesting it with steam and chemicals such as alkalis, mercaptans and mineral oils. The product of this digestion is refined in mills until a uniform blanket is obtained or extruded to obtain granular material.
Fine-grinding the tire allows the direct use of rubber residue in applications similar to regenerated rubber.
In power generation
The calorific value of tire scraps is equivalent to that of fuel oil, being around 40 Mej / kg. The calorific value of wood is around 14 Mej / kg.
Tires can be burned in furnaces already designed to optimize burn. In cement factories, their burning is already a reality in other countries. The Brazilian Portland Cement Association (ABCP) reports that about 100 million carcasses of tires are burned annually in the United States for this purpose, and that Brazil is already experimenting with the same solution.
On rubber modified asphalt
The process involves incorporating the rubber into pieces or powder. Despite the higher cost, adding tires to the pavement can even double the life of the road, because rubber gives the pavement greater elasticity properties when temperature changes. The use of rubber also reduces noise caused by vehicles contacting the road. Because of these benefits, and also to reduce the storage of old tires, the US government requires 5% of the material used to pave federal roads to be ground rubber.