The construction industry is responsible for the consumption of approximately 75% of the planet's natural resources. Stones, sand, iron and many other finite resources are removed in large quantities to supply markets.
In addition to exploitation, the large amount of waste generated at construction sites is worrisome, both on site and in demolitions and renovations. In Brazil, for example, waste from the construction industry can represent between 50% and 70% of the mass of municipal solid waste . The destination of this garbage is another key factor, as it is often placed in containers that end up in landfills without a suitable destination, overloading public sanitation systems and generating the appearance of informal disposal sites.
However, if you are careful, these wastes can have great potential for reuse. If they are properly destined and processed, recycled materials can replace others that would be extracted from the tanks, becoming raw material for new building components, of a quality generally comparable to the original materials.
Recycling is the process of reusing discarded materials to reintroduce them into their production cycle. This reduces the consumption of raw materials, decreases the total volume of waste and can even create jobs for thousands of people. To begin with, it is essential to have an efficient separation and collection system, minimizing the problem of clandestine deposition. Although the classification is different in each country, there are generally two main classes. The first refers to concretes, ceramics, stones and mortars, which represent the majority of the rubble. The other class refers to wood, metals, glass, plastics, plaster, among others.
Steel can be manufactured from the combination of iron and coal, heated in a blast furnace or through scrap recycling, using electric furnaces. Its recycling dates back to the Roman Empire, when soldiers used the instruments of war that were left in the trenches to produce new artifacts. In fact, steel can be infinitely transformed into new materials without losing its quality. When it is recycled, electricity consumption is 80% lower for the production of the new piece, causing a lower environmental impact and avoiding the extraction of new raw materials.
Reinforcing bars for reinforced concrete, wires, nails and some metal profiles are generally made from scrap metal.
Recycling concrete allows for the reuse of rubble, also reducing construction costs. For the recycling of hardened concrete, a special crusher is used, which produces the well-known “recycled aggregates”. Until recently, recycled concrete was only used as a subfloor, however there is evidence showing that the aggregate can create structural elements with a compressive strength of between 30 and 40 MPa (Megapascal), if the right technologies are used. It is important to note that recycled aggregates are lighter per unit volume, between 10% and 15% less than products from virgin quarries, which means less weight per cubic meter. This results in the reduction of the costs of the material itself, its transport and the overall costs of the project.
The use of "demolition timbers" is quite popular. Hardwoods can last for hundreds of years, if properly maintained. They can be used in large and structural parts, or made into slats for the manufacture of other artifacts, such as boxes,pallets or supports for various purposes. But even the softest and cheapest woods can be recycled, especially as raw material for the panel industry. The most common option today is the complete grinding of the material for the manufacture of MDF sheets.
Another option, if it is not possible to apply any of the above processes, is to eliminate wood waste for the production of biomass, through its burning in industrial furnaces.
The recycling of gypsum in construction is feasible, but it is a material that, if disposed of incorrectly, can emit hydrogen sulfide, flammable and highly toxic, which contaminates the soil and groundwater. However, if sent to suitable companies, recycled gypsum retains the same physical and mechanical characteristics as conventional gypsum at a relatively low cost.
EPS (Expanded Polystyrene)
Expanded polystyrene or EPS is a material that can also be recycled, becoming a raw material for the manufacture of new plastic products, when it is crushed and compacted. It can be turned into objects for finishes or even paintings.
Although glass bottles and containers are highly recyclable, this is not the case for glass used in windows. Each glass has different chemical compositions and melting temperatures, so they cannot be recycled together. However, there is the option of melting and remanufacturing the glass to convert it into fiberglass, and thus incorporate it into the asphalt and even combine it in reflective, yellow and white paints. Additionally, broken glass can be combined with concrete to create granite floors and countertops, for example.
Zinc, aluminum, packaging, textiles. There are many other materials that can be reused and recycled. Of course, there are also substances such as asbestos, latex paints, chemical solvents, adhesives, and lead-based paints, which must be treated carefully to reduce their impact on the environment. With the growing concern about increasing sustainability in the construction world, thinking about the complete life cycle of materials becomes vital. In addition to reducing the occurrence of landfills in clandestine sites and relieving pressure on landfills, recycling can reduce costs for both the environment and the consumer.
By Eduardo Souza