Slag Cement Facts What is Slag Cement?

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Slag Cement Association: Slag Cement Facts 
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Slag Cement Facts 
What is Slag Cement? 
 
Slag cement—sometimes referred to as ground granulated blast-furnace slag—is a 
hydraulic cement that significantly improves the strength and durability of concrete.
How Is It Produced? 
Slag cement begins in an iron blast furnace. Carefully controlled amounts of iron ore, 
along with limestone or dolomite, are fed into a blast furnace and heated to 2,700 degrees 
F. When molten, the iron is tapped for steel production and the slag is diverted to a 
granulator. Here, the slag is rapidly quenched with large quantities of water. The process 
minimizes crystallization and forms “granulated slag,” which is composed principally of 
calcium aluminosilicate glass. (Formation of this glass provides slag cement with its 
cementitious properties.) At this point, the slag is the consistency of fine sand. It is then 
dewatered and dried. Finally, the slag is ground to a fine powder and becomes slag 
cement, or it is interground with portland cement clinker to make a blended cement. 
What Is It Used For?
Slag cement is most widely used in concrete, either as a separate cementitious component 
or as part of a blended cement. It works synergistically with portland cement to increase 
strength, reduce permeability, improve resistance to chemical attack and inhibit rebar 
corrosion. Slag cement is used in virtually all concrete applications: 
• Concrete pavements 
• Structures and foundations 
• Mass concrete applications, such as dams or retaining walls 
• Precast concrete, such as pipe and block 
• Prestressed or post-tensioned concrete 
• Concrete exposed to harsh environments, such as wastewater treatment and 
marine applications 
• High-performance/high-strength concrete, used typically in high-rise structures or 
100-year service-life bridges 
Slag cement is also used in non-concrete applications such as soil-cement and hazardous 
waste solidification. 

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Slag Cement Association: Slag Cement Facts 
2