According to the World Steel Association, the European Union produced 177.2 million tonnes of crude steel in 2011.
Steelmaking can be carried out by basic oxygen steelmaking – primary steelmaking – in which oxygen is blown through molten pig iron. Another process is the Electric Arc Furnace (EAF) – secondary steelmaking – in which scrap metal and/or pig iron is directly exposed to an electric arc and melted down.
A by-product of both processes is steel furnace slag (SFS) which forms on the surface of the molten steel. EAF production – which accounts for some 42.8% of the total - generates up to 15 % of slag/tonne of steel. It is usually composed of molten metal oxides, silicates and ferrites, although the exact composition varies depending on the particular conditions of production. Currently, a great volume of slag is dumped, although there is increasing research into different application alternatives. One of the most important is as a recycled aggregate in road construction, as material for road foundation layers.
The LIFE GAIN project aims to demonstrate the feasibility of using SFS as an eco-friendly aggregate in the construction of railway tracks – specifically to form sub-ballast and sub-grade track foundation layers, a completely new technological solution. The ultimate goal of the project is to reduce the large volume of SFS that is annually disposed in landfills.
The project will produce a new eco-friendly aggregate - SFS-Rail – in valorisation plants. It plans to locate these plants next to steel furnaces to minimise the frequency and intensity of transport. A key feature will be the demonstration that it is possible to adapt an existing valorisation plant to produce the new material.
The project plans to construct 100 m-long test sections of rail. It will then use these to monitor the eco-friendly aggregate’s performance and hopefully demonstrate the predicted benefits of the material. Beyond showing that it is a technically feasible application for recycled SFS, existing research suggests that the project can hope to prove that its mechanical properties – strength, hardness etc. – will actually make it a more durable and sustainable product than natural aggregates.
LIFE GAIN hopes to show that SFS-Rail is an innovative, sustainable and eco-friendly alternative to natural aggregates, applicable throughout Europe. It expects to demonstrate that the technology used to produce SFS-Rail will be easily transferrable to other European countries where there are a large number of furnaces currently facing the same environmental problem.
Based on the application of SFS-Rail in the test sections of the project the expected results are:
- Reduction of the volume of the annual slag disposal on landfills by 1 078 tonnes – with a potential reduction in Europe of 360 000 tonnes/yr;
- Reduction of the use of natural aggregates by 1 078 tonnes – also with a potential reduction of 360 000 tonnes/yr;
- Reduction of the environmental impact at quarries;
- Reduction of the frequency and intensity of transport of SFS;
- Reduction of energy consumption by 197.5 Mkwh - with a potential reduction in Europe of 65 909 Mkwh/yr;
- A reduction in overall CO2 emissions of 6.03 tonnes – with a potential reduction of 2 014 tonnes/yr; and
- Reduction of other environmental impacts, including deforestation, the impact on vegetation and fauna and hydrological impact.