Study of the usability of the basic oxygen furnace slag in terms of artificial aggregate as lower foundation and foundation layers in flexible superstructures

The rapid increase in the world population, industrial growth and technological developments that are constantly advancing, increase the need for raw materials thus resulting in natural resources to be consumed at a rapid rate. The depletion of these finite resources and the rapid degradation of the environmental balance in this process pose a great threat for future generations and natural equilibrium. This fact has led the human being to pay more attention to the effective use of by-products and recycling waste. Studies on this subject are taking place worldwide including Turkey and efforts are put to get positive results about recycling. The development of a country is directly proportional to the sustainability of investments in that country and the minimization of environmental impact. Turkey is a country that is constantly developing and constantly expanding its economy. Investors and the government of a growing country in this way need to work hard to reduce the environmental damage of the investments made. Our country has a natural beauty that is unique and unparalleled elsewhere in the world. Unfortunately, however, nature does not receive the desired sensitivity and is given great damage. Investments made with the developing industry give unacceptable damage to natural resources and to this treasure. As citizens of the country, they must strive to prevent all individuals from being sensitive to this issue and depriving future generations of these beauties. Being a conscious consumer community is one of the most important parts of sustainability. The construction sector in Turkey has been growing at a very rapid pace in recent years and this growth is continuing to increase. The biggest raw material of the construction sector is the aggregate. As an alternative to aggregate, the use of slag as raw material in the construction sector is significant for recycling. One of the branches of the construction sector that requires the raw materials is transportation investments. In transportation investments, road construction, the most used material is the aggregate. The decline of natural stone quarries from day to day and the idea that the slag, which is iron-steel factory waste, could be used as raw material ensured the emergence of this academic work. Progress in transportation investments in our country and the large need for raw materials of these investments have led the sector to conduct research for the utilization of by-products and wastes. Turkey is in the 9th place in steel production in the world and the amount of production results in the waste formation in high volumes. Because of the high storage costs and adverse impacts on the environment, recycling and of slag generated as a by-product from iron and steel plants and reuse of them in other industries are of immense importance. In this study, the use of basic oxygen furnace slags, which occur during steel production, as artificial aggregate in flexible superstructures in substructure and foundation layers in steel making plants with basic oxygen furnace has been investigated. Experiments are carried out with materials according to the Highway Technical Specification 2013 data. In these experiments, basic oxygen furnace slag obtained from Ereğli Iron and Steel Plant was used. In the basic oxygen furnace production process, molten pig iron and scrap metals are used. In this respect basic oxygen furnace also contributes to the recycling of the production phase as it is also used in scrap metal. Recycling of this slag is of foremost importance as slag also appeared during production. In the first chapter of the thesis, the purpose and scope of the research is explained. Information on the damages caused by slags not recycled are given and examples are given. In the second chapter, infrastructure and superstructure layers of highway construction is explained. Layer types have been studied together with their subheadings. According to the Technical Specification of Highways, road strata are explained. In the third chapter, iron and steel production, iron and steel sector and furnace types are examined. Information about iron and steel sector in Turkey and in the world, has been given. In the same section, separate production methods are explained according to furnace types and working principles are given. In the fourth chapter, the formations, properties and application areas of slags emerging from iron and steel plants as waste material are explained. In the fifth chapter, the material properties and construction conditions of the lower foundation and foundation layers according to the Highway Technical Specification 2013 are described. The application granulometry limit values of each layer are given in tables. In very chapter, the experiments to be performed according to the technical specification are explained and the results of the experiments that are carried out using samples from Erdemir basic oxygen furnace slag are studied. In this study, according to the standards of the Highways Technical Specification 2013, the resistance against weather effects (frost), (Los Angeles) abrasion test, flatness index test, water absorption test, plastic limit and liquid limit test, experiment, organic matter experiment (with 3% NaOH), methylene blue experiment and the experiments are explained. Modified Proctor and California Transport Ratio Tests are performed according to, 9 different mix, lower limit, upper limit and the average design granulometry of the lower foundation type B, the foundation type A, the plant mix foundation 1 (PMT1). The results of the experiments are compared with the data of KTŞ 2013 and it was evaluated whether the material satisfy the requirements of the specification. Finally, in the sixth section, comments are listed on the results of abovementioned experiments and suggestions are presented.