From the World Leader in Construction Materials
Air Cooled Blast Furnace Slag (ACBFS) - An environmentally friendly alternative to mined aggregate, offering superior performance, substantial savings, and excellent value.

What is Air Cooled Blast Furnace Slag?

Air Cooled Blast Furnace Slag (ACBFS) is a versatile construction aggregate that provides superior compaction and skid resistance plus cost savings over mined aggregate.

It can be safely used in a variety of applications including concrete, asphalt, sub-base, bedding, and backfill.

Duquesne Slag Operations

890 Noble Drive West Mifflin, PA 15122


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Matt Smith

Paul Thomas

Blast Furnace Slag is produced to meet state specifications for gradation and other key requirements.

The American Society of Testing and Materials (ASTM C-125, Definition of Terms Relating to concrete and concrete Materials) defines Blast Furnace Slag as “the non-metallic product consisting essentially of silicates and aluminosilicates of calcium and other bases, that is developed in a molten condition simultaneously with iron in a blast furnace.”

Air Cooled Blast Furnace Slag is the mineral which results from the reaction of limestone (high calcium) and dolomite (high magnesium) with earth metals in iron ore in a blast furnace. It is the co-product of iron manufactured in a blast furnace.

Air Cooled Blast Furnace Slag is the material resulting from the solidification of molten blast furnace slag under atmospheric conditions, subsequent cooling may be accelerated by the application of water to the solidified surface.

Air Cooled Blast Furnace Slag aggregate is created by crushing, screening and washing the blast furnace slag into specification aggregate sizes.

Air-Cooled Blast Furnace slag is non-expansive as tested in accordance to PennDOT PTM130.

PennDOT, Pennsylvania Turnpike, WVDOT, ODOT Approved Air Cooled Blast Furnace Slag undergoes a sulfur leachate test in accordance of Ohio DOT Supplemental 1027 to ensure the material is ecologically benign for use in unencapsulated applications. #1, #8, #10, #57, and #2A Slag is available for these applications once it has been tested and approved in collaboration with the Pennsylvania Department of Transportation, Pennsylvania Turnpike Commission, West Virginia Department of Transportation or the Ohio Department of Transportation.

Chemical Properties

The principal constituents of slag are silica, alumina, calcia and magnesia, which comprise 95% of slag’s total make-up. Minor elements include manganese, sulfur and ferrous compounds as well as trace quantities of several others. The compounds do not occur as oxides in the slag but are combined to form various silicate and aluminosilicate minerals such as melilite (2CaO. A1203.SiO2 and 2 Cao. Mg0.2SiO2), merwinite (3CaO. Mg0.2SiO2), wollastonite (aCaO.SiO2), etc., as found in natural geological forms.

Features and Benefits

Weight/volume advantage

Air Cooled Blast Furnace Slag has a lower weight to volume relationship than mined aggregates (stone and/ or gravel). A given volume requires 10%-35% less slag than mined aggregate, which translates into significant cost savings.

Superior compaction

Air Cooled Blast Furnace Slag compacts quickly to a more stable base than mined aggregates. In road
work and backfill applications, project completion is accelerated, translating again into significant cost savings.

Graded to meet specifications

Air Cooled Blast Furnace Slag is crushed and graded to meet the grading requirements of state departments of transportation and other specifying agencies.

Resistance to polishing

Air Cooled Blast Furnace Slag has a rugged, vesicular surface with a High AWI (Aggregate Wear Index). It resists polishing in surface applications as aggregate in portland cement concrete, asphalt concrete, and chip seal Applications. The surface characteristics provide for superior skid resistance and stability in asphalt pavements.

Beneficial texture and shape

Air Cooled Blast Furnace Slag has a cubical vesicular structure with surface and interior non-connected voids. This structure and shape creates greater surface area and provides for an excellent bond with portland cement mortar for greater compression strength and improved adhesion with asphalt for increased stability in asphalt concrete.

Multiple construction applications

As dense graded aggregate base under pavement, as bedding and backfill under and around structure, as aggregate in portland cement concrete and asphalt concrete, as aggregate in concrete block, Air Cooled Blast Furnace Slag is the construction material
of choice.

Weight Advantage

Air Cooled Blast Furnace Slag weighs less per unit volume than mined (limestone, sand & gravel) aggregate...

weight advantage chart

...translating into significant sustainability and cost savings for contractors when they use Air Cooled Blast Furnace Slag.

These are examples only - actual delivered pricing will vary.

Applications table

The Circular Economy


As a world leader in recycling, Holcim is committed to building better with less and preserving the earth’s ecosystems. We promote circularity along the entire value chain to eliminate waste and decouple our business growth from the consumption of finite natural resources.

circular economy infographic