GGBFS/Steel Furnace Slag for cement - HLC-062

Ground Granulated Blast Furnace Slag(GGBFS)specification:

These products are made from steel slag, which occurs as a by-product during steelmaking. Due to their unique characteristics, they are used in various fields. With awareness of the need for environmental protection increasing, these steel slag products are highlighted as excellent materials from the viewpoint of resource and energy conservation.

Steel slag is used as raw material for blast furnace cement. Compared to mixed cement, blast-furnace cement offers the great advantages of increased durability (high resistance to seawater, reduction in alkali-aggregate reactivity, etc.) and enhanced long-term strength, along with lower CO₂off-gassing.

Information:

1 Durability

GGBS has now effectively replaced sulfate-resisting Portland cement (SRPC) on the market for sulfate resistance because of its superior performance and greatly reduced cost compared to SRPC. Most projects in Dublin's Docklands, including Spencer Dock, are using GGBS in subsurface concrete for sulfate resistance.

2 Appearance

In contrast to the stony grey of concrete made with Portland cement, the near-white color of GGBS cement permits architects to achieve a lighter colour for exposed fair-faced concrete finishes, at no extra cost. GGBS cement also produces a smoother, more defect free surface, due to the fineness of the GGBS particles. Dirt does not adhere to GGBS concrete as easily as concrete made with Portland cement, reducing maintenance costs. GGBS cement prevents the occurrence of efflorescence, the staining of concrete surfaces by calcium carbonate deposits.

3 Strength

Concrete containing GGBS cement has a higher ultimate strength than concrete made with Portland cement. It has a higher proportion of the strength-enhancing calcium silicate hydrates (CSH) than concrete made with Portland cement only, and a reduced content of free lime, which does not contribute to concrete strength. Concrete made with GGBS continues to gain strength over time, and has been shown to double its 28-day strength over periods of 10 to 12 years.

4 Sustainability

Since GGBS is a by-product of steel manufacturing process, its use in concrete is recognized by LEED etc. as improving the sustainability of the project and will therefore add points towards LEED certification. In this respect, GGBS can also be used for superstructure in addition to the cases where the concrete is in contact with chlorides and sulfates. This is provided that the slower setting time for casting of the superstructure is justified.