For years these corrugated sheets of bituminous cardboard for roofs were destined for landfills. Now they can be recycled

The wavy slabs, consisting of recycled paper and bitumen, used for roofing or as a waterproof element to be placed under the tiles and cups, once removed were intended for landfill disposal due to the mix of components of which they were composed.

The fibro-bituminous slabs were born in France in 1944 for the initiatives of Mr. Gaston Gromier who founded the company OFIC S.A.

Until the 1960s the product remained the same due to the strong demand for economic roof cover in the post-war period. Subsequently, the international market became interested in the type of roofing plate, appreciating its ease of laying, colors and cost-effectiveness, prompting the company to increase its types, colors and formats.

But how are the slabs composed?

There are four main raw materials that make up the product:

• Recycling paper
• Paper additives
• Road bitumen 80/100
• Surface pigments

Recycling paper is normally made up of packaging cardboard and unpained newspapers, which create an ideal mix of long and short fibers. It must be used with a low humidity percentage to avoid processing problems. The recycling paper, in the processing, will form the skeleton of the corrugated slab.

The bitumen used is generally the one classified with an 80/100 penetration degree, which corresponds to the type that is also used in road paving. The hot-applied bitumen will aim to waterproof the roofing plate and protect the structure in semi-rigid paper.

Synthetic cone pigments have both the function of attributing a particular color to the slab based on the use that you want to make, but also protect the bitumen from the corrosive effects of the sun’s rays.

How are the slabs produced?

The maple paper (recycled) is selected according to the recipe of the paper mill that produces the artifact and entered in a plant, called pulper, which has the purpose, under the mechanical and water rotary effect, to dismember the mix of cards, loaded into the plant, in order to amalgamate the fibers that will form the supporting structure of the product.

Once this process is finished, the paper fiber is ready to be fitted into a corrugated slab.

The construction of the structure of the plate can take place:

• To wrap multiple sheets to compose a thin multilayer plate
• To press a certain amount of fiber into a mold by forming a thicker slab

After the formation of the flat and damp slab, it is initiated to a corrugator through which the slab will take the desired wavy form.

The corrugators, with the slab perched on top of them, will be directed to a tunnel oven for drying and subsequent cooling, the purpose of which is to make it semi-rigid.

The dry cardboard artifact will now have to be waterproofed with liquid bitumen and, this process, will be made in two different operational methodologies:

For multilayer slabs, having a specific density high, it is necessary to provide waterproofing through a bath in a hot bitumen tub.

For the monolayer plate, waterproofing will take place through a bath in a hot bitumen tub.

The last step is the coloring of the extractor of the slab, which will be sprayed or dipped, depending on the final destination of the artifact, with the choice of the correct colored mixture and the necessary U.V. protections.

How do I recycle the product at the end of my life?

Until a few years ago, the bituminous sheets, once removed from the roofs for breakages, wear or other patterns, ended up in landfill because the composition with symbiotic materials did not allow them to be recycled.

If we consider that, in Europe alone, the lumps produced each year are around 2 million tonnes,we can imagine the amount of oil waste to be recycled.

Today the recycling process is possible because, after several tests, it has identified the most suitable channel to give a second life to this product. In fact, it has been seen that the road-bitumen sector, which already welcomes in its recipes the recycled ground of tar oil sheaths and tyres, has found the right balance to use even the druvy tarps.

Considering that on average a roofing plate contains about 60 in the weight of road bitumen, and being this perfectly compatible with that normally used for asphalt and that the basic structure formed by the paper, if added in the correct percentages, the use of the grind from bitumen roofing slabs does not affect the final recipes of road bitumen.

The slabs are then ground into special mills,removing any remaining nails for anchoring still present, creating a grind of different grains depending on the customer’s requirements.

With the reclaimed mince, road paved producers can make mixtures that respect the philosophy of the circular economy by being able to use recycled products, save the use of a part of natural bitumen, reduce waste destined for landfill and improve the environmental impact.