Utilized

Cement Industry

Iron and steel slag products are used in a variety of areas where their unique characteristics are put to effective use. The majority of the demand for these products comes from the field of cement. Approximately 40% of iron and steel slag products, and 60% of blast furnace slag, are used in cement. Most of these products are used as a raw material in Portland blast furnace slag cement. Portland blast furnace slag cement has the following characteristics

(1) It has high resistance to seawater and to chemicals, and can improve durability.
(2) It has a low chloride ion diffusion coefficient (resists rebar corrosion).
(3) It can reduce alkali-aggregate reaction.
(4) Its strength increases over time.
(5) It produces little elution of hexavalent chrome when used in ground improvement.

Wave Breaker

Tetrapods are a type of structure in coastal engineering used to prevent erosion caused by weather and longshore drift, primarily to enforce coastal structures such as seawalls and breakwaters. Tetrapods are made of concrete, and use a tetrahedral shape to dissipate the force of incoming waves by allowing water to flow around rather than against them, and to reduce displacement by interlocking.

Roads

Iron and steel slag used in road construction is manufactured by crushing and mechanical stabilization of blast furnace slag and steelmaking slag for use as paving material. These two types of slag are used in base course materials that are produced from them individually or in a mixture, and steelmaking slag is used as an aggregate for asphalt mixtures. Blast furnace slag contains a small amount of sulfur. When sulfur contacts water, the water turns yellow and may emit an unpleasant odor. To prevent these problems, aging is performed. In this process, the sulfur is oxidized by reacting with air to form stable sulfate ions or is neutralized with carbon dioxide gas. Aging is carried out by piling the product in a holding yard immediately after crushing and sifting until it has stabilized.

Civil Material for Airport / Harbors

Granulated slag for civil engineering works is lighter in weight than natural sand (11 – 16 kN/m3 wet unit weight), has a high angle of shearing resistance (35℃ or more), and has the hydraulic property that it hardens over time. It also has the same, or better, water permeability of high-quality sand.
Because of its properties, steelmaking slag can be handled as granular material in the same way as natural road base course material. It has better soil mechanics than natural base course material, including a higher bulk density and larger angle of internal friction. However because it contains lime, its properties also include expansion and high alkali dissolution.

Fertilizers

Because blast furnace slag contains fertilizer components CaO, SiO2, and MgO, it is used in rice cultivation as calcium silicate fertilizer. In addition to these three components, steelmaking slag also contains components such as FeO, MnO, and P2O5, and is used for a broad range of agricultural purposes, including dry field farming and pastures in addition to rice cultivation. Its alkaline property also remedies soil acidity.

Ceramic Tile Production

With an objective of making ceramic tile, granulated blast furnace slag (GBFS) and common clay were mixed whereby calcia and silica ratio varied from 0.04 to 0.86. Calcia and silica combined calsium-wollastonite as the major minerals and phase in the sintered microstructure. Excess silica combined with magnesia, iron oxide and alumina to from enstatite, fyalite and alumino silicates respectively during sintering. Optimum compositions were found to be where calcia-silica ratio were in the range of 0.1-0.3 where mechanical strength and water absorption of the fired specimen were in the range of 28-38 MPa and 2.5-0.1% respectively. Physical properties of the sintered specimen are explained on the basis XRD and SEM analysis. Formation of wollastonite in the sintered compacts with finer grain size was found to be an important parameter for increase in strength.

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