Blast Furnace Slag

Blast furnace slag is one of the most versatile products used in construction. Crushed and screened to required gradations, blast furnace slag is the preferred aggregate where its unique qualities assure highest performance:

• Maximum Durability
• Higher Fire-Resistance
• Higher Strength
• Better Insulation
• Extreme Hardness
• Lighter Weight
• Skid Resistance

Where is blast furnace slag used?

Aggregate Base:

• Used under both portland cement concrete and bituminous concrete paving

• All types of binder and wearing courses

• Lightweight block

• All types of concrete paving, sidewalks, curbs, slabs and structures

• Used on main lines of major railroads and spur track ballast for plant service

• Slag aggregate surfacing for built-up roofs

• Raw material for rockwool or mineral wool insulation production
• Chip and seal surfacing
• Slurry seal surfacing
• Glass-making raw material
• Filter media applications
• Soil conditioning
• Cement manufacture
• Surfacing for playgrounds, driveways, and ball diamonds
• Head lap granules on asphalt shingles

• All construction uses, interior and exterior

General Characteristics

Blast furnace slag is the co-product of molten iron production in a blast furnace.

The chemistry usually has a narrow ratio of basic to acid components.

Calcium and magnesium content, reported as equivalent oxides, normally results in a 1.25 to 1.55 basicity ratio.

The total basic elements, reported as equivalent CaO plus MgO divided by silica results in slag chemistry such as:

• CaO - 38%
• MgO - 10%
• SiO2 - 36%

with minor elements such as:

• Iron Oxide - (FeO &Fe₂O₃)<1%
• Sulfur - (S) 1%±
• Alumina - (Al₂O₃) 6-12%

Physical Characteristics

Slag Type	Physical Characteristics
Air Cooled	Molten slag poured into pits in layers, allowed to solidify, and cooled either by external temperatures or by water addition after solidification, then crushed and screened.
Expanded or Lightweight	Produced by rapidly pouring molten slag into sloping pits, moist on the bottom to allow steam penetration while still viscous, causing many small voids.
Granulated	Rapidly cooled by a high velocity mixing of molten slag flow with water jets in a ratio of one part slag to 6-10 parts water by mass.
Pelletized	A variation of granulating in which less water is used with violent impelling of the viscous, but rapidly cooling slag through the air.