Where it is better to be used slag cement?

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 (SCIC #9, "Reducing Thermal Stress in Mass Concrete")
• Precast and prestressed concrete (SCIC #16, "Producing Precast and Prestressed Concrete with Slag Cement")
• Pipe and Block (SCIC #17, "Producing Concrete Pipe with Slag Cement"; SCIC #18, "Producing Concrete Block with Slag Cement")
• Concrete exposed to harsh environments, such as wastewater treatment and marine applications
• High-performance/high-strength concrete, such as high-rise structures or 100-year service life bridges (SCIC #15, "Slag Cement in High Performance Concrete")

Slag cement is also used in non-concrete applications such as soil-cement and hazardous waste solidification.