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Steel Sands Solution

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We have seen the old CDs hanging from the branches to scare away the birds from the gardens; we have seen to remove from the old shirt many rags to clean the crystals of the house; we have seen old marmites to keep the umbrellas impregnated by the rain. However, the amount of waste that accumulates in the sidewalks can hardly be seen used.

Stainless steel is probably the best known of steels. It is fashionable, they are of non-oxidizable steel spoons, knives, casseroles, barrels of some sidrerías, kitchens... However, there are other types of steels, such as alloy, low alloy or carbon. These last ones are seen, for example, in the body of the cars, in the somieres and in the helmets of the ships. These steels differ in their chemical composition.

Steel is a carbon and iron base alloy, but can carry chromium and nickel. Despite its hardness, it is easy to give shape, which is probably the main feature of steel. Steel is obtained by heating the scrap iron and in the process different by-products are generated. From the iron heated in the electric furnace comes the black slag, heavy, from whose purification comes a fine powder, the white slag. Each one has its composition and properties.

The Basque Country has 15 steel mills, among which hundreds of thousands of tons of slag are generated. The residues are managed by the factories themselves and their final destination is mainly in their landfills. However, black slag has a solution and is used to make roads. The white slag is, therefore, the one that accumulates the most, since it is not used for any other use.

Solutions in the thesis

The white slag is a fine powder that accumulates forming dunes in the dumps' landfills. In a thesis presented at the University of the Basque Country, three solutions are proposed to convert this dust into something useful.

For example, it can be used as a mortar. The mortar is used to coat brick walls. It is mainly made with cement, sand and water. The addition of white slag to the mortar does not alter its characteristics and reduces the process by requiring less cement. To this conclusion has arrived Milagros Losañez, author of the aforementioned thesis, of the studies carried out in the laboratory.

In the same way, the white slag can be used for the formation of cement soil, giving rigidity to the tracks. Although it has been done in an unregulated way, the residues of the sidewalks are used for a long time for this task, which has proven any person who has walked the mountain. It has been done mixing white slag and black slag. Now, after research, it has been shown that this mixture has excellent properties for this application. For example, it has been shown that rainwater does not carry clear indications, so the use of slag is ecologically acceptable.

On the other hand, there is the possibility of using white slag as concrete mixed with black slag, but some problems have been found in the tests performed and it is not the most suitable solution for the thesis, since it requires a high control of the product.

Waste raw material waste

For each ton of steel produced it is generated between 120 and 150 kg of black slag and between 40 and 70 kg of white slag. If steel is still produced, the waste source can be considered inexhaustible. Construction and civil work is a sector of great strength that consumes a lot of raw materials. In this way, an economic saving and a reduction of waste can be achieved by using what one has more.

Of course, in practice it is not as simple as it seems, and some problems should be solved first. For example, some changes in production should be introduced. In fact, today in the steel mills is the one that has value, the white slag is only a residue. Therefore, the production of slag is not controlled. If from now on you want it to be a product of value, you will have to control it as it is done with steel.

In spite of the difficulties, the sustainable development and the attitude of environmental protection incites to reduce and recycle waste. The waste that each generates in your home is managed individually, by recycling glass, oil and paper, or by using CDs, old shirts and marmitas. Similarly, the industry is looking for a solution to its waste. The steel mills generate thousands of tons of waste; construction and civil works need hundreds of tons of materials. The combination of both would mean a small reduction in the human trash bag.