Investigation of usage of electric arc furnace slag as artificial aggregate in cement stabilized base course of flexible pavement

As a result of industrial activities along with increasing world population and technological developments, unserviceable materials named as "waste" increase day by day and affect environment negatively. Various researches conducted associated with waste management topics in order to reduce generated and recycled wastes. Commencement of extinction of the current resources, recycling of waste and evaluating as an alternative raw material source have extended the studies. Arising from production quantity in million degrees and generated as a result of industrial activities, recycling with raw material source usage in different industries, waste disposal, cost reduction and efficient source usage constitutes an importance. Iron and steel industry products are constituted fundamental raw materials of industrial sectors. It is not only been vital part of the society, but also strategically significance from the point of the countries in sectors such as construction, infrastructure, machinery and automotive with great strength and durability. Steel production is growing day by day all over the world. Only in 2014, 34 million tons steel produced in Turkey while 1,662 million tons produced around the world. Both in Turkey and in the world, 70% of steel productions is performed with EAF furnace. Waste and by products are comprised 90% of slag, dust and sludge in iron and steel industry. Iron and steel slag constitutes most of the waste product of iron and steel production. Nowadays, production of 1 ton liquid steel generates 169 kg Electric Arc Furnace (EAF) slag, 275 kg blast furnace slag in integrated facilities and 126 kg basic furnace slag. Every year, over 400 million tons iron and steel slag is produced around the world. In the light of this data, considered that steel productions and their increments, obtained slag could be regained as a raw material source for various industries. One of the sectors that used a major level of raw material is construction sector. Especially, in road constructions in which extra raw material needed, 95% of materials constitutes from aggregate. Consumed aggregate sources increase demand for new aggregate mines (fields) each day passing. This situation also results in an increase of costs. The use of iron and steel slag as a road construction material benefit not only the environment, but also the financial way. Due to the very high costs for landfilling, many solutions have found for recycling. Thereby, use of slag generated during production of iron and steel on road construction besides its contribution to the environment, with efficient source usage it presents an economic solution. While iron and steel production proceeding on integrated facilities, some solid wastes occur such as blast furnace slag, steel slag, coal ash and dust. Disposing of these solid wastes may cause soil pollution, ground and surface water pollution. Emerged slags seems like "waste" in iron and steel industry, have constituted major part of the waste and by products. Slags defined as marketable products along with increment their usage area. New execution areas enhanced while growth in economical, environmental and social advantages of slag use. Iron and steel slag is being marketable product with increasing usage possibilities. Slag is widely used in construction sector especially in cement paste, concrete mixture, hydraulic structures and road constructions. Steel plant slag is considered to be very suitable for road constructions based on strength, stability, abrasion, porosity and water absorption properties. Some investigations are being made about steel plant slag if it can be used as sub-base material in road constructions with its great strength properties. In this study, availability of EAF slag, which is generated as waste product of iron and steel production, was investigated as artificial aggregate in cement stabilized base course of flexible pavement. All of the experiments have done comparatively with natural aggregate within the scope of Republic of Turkey General Directorate of Highways Technical Specification published in 2013. First of all, importance and goal of this study were explained literally. Then, general information about flexible pavement layers was asserted. Also, significant processing steps and types of iron and steel production, which are blast furnace, basic oxygen furnace and electric arc furnace, were explicated. Iron and steel industry was revealed with numerical data both for Turkey and world-wide. Some information have given about generation of slag which is derived from iron and steel production, types of slags, physical and chemical properties of slags. Their generation stages and reactions are given in 4 main topics as blast furnace slag, basic oxygen furnace slag, electric arc furnace slag and secondary metallurgical slag. General usage area and usage ratios were stated in terms of slag types. Where the experimental studies handled after this section, the usage of EAF slag was investigated in cement stabilized base course of flexible pavement. Certain information detailed about physical properties and layer stabilities of aggregate can be used in cement stabilized base course according to Republic of Turkey General Directorate of Highways Technical Specification published in 2013. Numerous experiments performed such as density and absorption of aggregate test, Los Angeles abrasion and impact test, flatness index test, determination of organic matter test, methylene blue test, clay lumps and friable particles in aggregates test, durability of freeze effect test, liquid limit test and plastic limit test to determine physical properties of EAF slag and natural aggregate within the scope of Republic of Turkey General Directorate of Highways Technical Specification published in 2013. As a consequence, all assessments were made according to experimental test results. Usage of EAF slag was investigated in cement stabilized base course of flexible pavement. If slag is carefully treated beginning at the EAF furnace to the slag plant, it can be a useful and competitive product for road construction and several other applications. Certain suggestions were made about usage of EAF slag in road constructions.