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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.
Superior durability and cost performance |
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Granulated slag for civil engineering works is used in a broad range of applications, including coastal protection backfill, earth covering for correcting soft ground, road subgrade, and embankments.
The physical and mechanical characteristics of sand-like granulated slag include being lighter than natural sand, with a larger angle of shearing resistance. In addition, it has a hydraulic property that causes it to hydrate and solidify over time, yielding a high resistance to liquefaction in the event of an earthquake. When granulated slag is used as a coastal protection backfill material, its light weight and high angle of shearing resistance can be used to good effect, greatly reducing the active earth pressure on the front sheet piles and allowing the sheet pile cross-section to be reduced. Once fully solidified, it will not liquefy in an earthquake, making additional liquefaction countermeasures unnecessary.
When granulated slag is used as an earth covering for correcting soft ground, its light weight reduces the danger of lateral soil flow as well as the amount of consolidation settlement. Because it is also resistant to the effects of water, it provides superior trafficability.
Subgrades made of granulated slag are lightweight and suitable for soft ground. They do not undergo large deformation under traffic loads and provide sufficient bearing capacity. As a road structure, the hydraulic property gives this subgrade advantages including no loss of strength caused by penetrating water even under repeated traffic loads. In addition to cost performance and workability, it offers excellent durability.
When granulated slag is used in embankments, because of its light weight and large angle of shearing resistance, it can provide advantages in design when embankments are constructed on soft ground.
Lighter weights and lower costs for backfill materials:
Tobishima Minami district quay at the Port of Nagoya |
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The Tobishima Minami Container Terminal at the Port of Nagoya began operation in 2005, and is among the largest terminals in Japan, with a seismic-reinforced quay reaching to a depth of 16 m that allows container vessels 10,000 TEU* in size or larger to dock.
Because the material for the backfill of this quay was changed from crushed stone and other materials to granulated slag during a design review, it was possible to reduce the cross-sections of the front steel tube sheet piles and raking piles, greatly reducing the construction costs (by approximately 18%, according to the Port of Nagoya Office of the Ministry of Land, Infrastructure, Transport and Tourism).
*TEU: Unit indicating the load capacity of a container vessel. One TEU is equivalent to one 20-foot container.
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| Steel sheet pile with backfill type |
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Tobishima Terminal, Port of Nagoya |
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Tobishima Minami District Quay, Port of Nagoya |
Contributing to the recovery from the Great Hanshin-Awaji Earthquake:
Rokko Island, Kobe City |
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Approximately 1.1 million tons of granulated blast furnace slag was used in the quay restoration work at the Port of Kobe after the Great Hanshin-Awaji Earthquake of 1995. At the time, the foundation beneath the caisson structures of the Rokko Island District quay at the Port of Kobe had been damaged and largely displaced. During recovery work, because it was necessary to reduce the load applied to existing structures as much as possible, backfill of granulated blast furnace slag over a width of approximately 19 meters was used in order to reduce the earth pressure.
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| Caisson |
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Rokko Island, Port of Kobe |
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Recovery work for the quay
(Rokko Island, Port of Kobe) |
Steel slag crushed stone for civil engineering works (JSTM H 8001)
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 higher bulk density and a larger angle of internal friction. However because it contains lime, its properties also include expansion and high alkali dissolution. By fully understanding these properties and using appropriate methods of use and construction that can fully utilize the characteristics of iron and steel slag products, these products can be expected to result in well-planned, cost-effective structures.
Under these conditions, a new organization standard from the Japan Testing Center for Construction Materials (JSTM standard) was formulated for steelmaking slag materials used in civil engineering works – materials that were not covered by earlier JIS standards. This new standard prescribed the categories, quality standards, and sales management standards for each application of steelmaking slag created from converter slag and electric arc furnace slag. |
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