1. CON 123
Cementitious Materials
Session 7
Slag Cement

2. Ground Granulated
Blast-Furnace Slag “Cement” (GGBFS)
 Ground Granulated
blast-furnace slag is the
correct technical term
for slag that is finely
ground and is used as a
separately batched
cementitious materials.
 Slag is ground to the
fineness of Portland
cement or finer.

3. Ground Granulated Blast-Furnace
Slag “Cement”
Finely Ground granulated
blast-furnace slag
consisting of primarily
calcium and aluminum
silicates, used as a partial
replacement for Portland
cement in concrete

4. ASTM 989
Slag Cement
 GGBFS – glassy granular material formed
when molten blast-furnace slag is rapidly
chilled as by immersion in water with or
without compositional adjustments made
while the blast-furnace is molten

5. Grades of Slag - ASTM C 989
Strength of 1:1 Slag: Cement Mortar
Slag Activity Index =
Strength of Control Cement Mortar
Grade 7-day Index 28-day Index
80 - 75
100 75 95
120 95 115
Requirements for average of 5 consecutive

6. Specifications and Grade of Ground Granulated
Iron Blast-Furnace Slags
ASTM C 989 (AASHTO M 302)
 Grade 80
 Slag with a low activity
index
 Grade 100
 Slag with a moderate
activity index
 Grade 120
 Slag with a high activity
index

7. Slag - Manufacture
Iron Blast Furnace
 Iron ore is layered with a mixture of limestone
and coal or coke. The coal is the fuel. The
limestone is a flux that reduces fusion
temperatures.
 The molten materials settle out at the bottom
and slag floats on the top of the pig iron. It is
tapped away

8. Slag - Manufacture
Iron Blast Furnace
Iron Ore Limestone/Coal
Fusion at
1400 to 1600 C
Slag
Pig Iron

9. Slag – Manufacture
Hot Runner
 Molten blast furnace slag is tapped from the
blast furnace, moved through a hot runner on
the blast-furnace work floor. Dropped in a
“blow” box to a jet-process granulator.
 GGBF is glassy - with the right chemistry and
morphology to form hydraulic cement when
finely ground.

10. Slag – Manufacture
Hot Runner

11. Slag - Manufacture
Jet Process Granulator
Liquid Slag Adjustable Deflector Plate
Furnace Runner
Vibrating Feed Plate
Rotating Drum
Granules Pellets

12. Slag Products - Manufacture
Molten Slag is cooled
Air-cooled Aggregate
Palletized Granules & Pellets
Jet Process Granulator Granules
Granules are ground in a ball mill
Fineness similar to cement

13. Slag - Manufacture
Grinding Mills

14. SEM Micrograph of Slag Particles
Scanning electron microscope micrograph of
slag particles.
Scanning electron microscope micrograph of slag particles.

15. Slag - Characteristics
 Cooled Rapidly - Glass
 Fineness - 450 to 650 m2/kg
 Specific gravity - 2.90
 White to Buff color
 Hydration - activated by alkalis
 Forms cementitious silicates - C-S-H

16. Slag - Reactivity
 Glass content
 Fineness
 Alkalis of reacting system
 Concrete curing temperature

17. Slag - Mechanism
Portland Cement Portland Cement + GGBF Slag
Reduced Permeability
Increased Strength

18. Slag - Typical Dosage
Application Dosage
( % by wt)
Exterior flatwork 35%
General use 35 to 50%
Mass Concrete 60 to 80%
Sulfate Resistance
Type II equivalent 35%
Type V equivalent 50%
Marine/chemical/heat >50% < 80%

19. Slag – Typical Dosage
Application Dosage (% by wt)
Exterior Flatwork 35%
General Use 35 to 50%
Mass Concrete 60 to 80%
Sulfate Resistance
Type II Equivalent 35%
Type V Equivalent 50%
Marine/chemical/heat >50%, <80%

20. Slag - Mixture Proportioning
 Typical - 35 to 50% wt. cementitious
 w/c ratio w/(cement + slag) ratio
 Water demand - 1 to 5% lower
 Admixture dosage
 Similar for air entraining admixtures
 May be lower for others
 SG 2.90 - more abs. vol. than cement

21. Slag Benefits
Workability Finishability Pumpability
Color Durability Strength

22. GGBF Slag Concrete
Workability
22

23. GGBF Slag Concrete
Finishability

24. GGBF Slag Concrete
Pumpability

25. GGBF Slag Concrete
Color
25

26. Slag - Applications
 Compressive and Flexural strength
 Permeability
 Sulfate Resistance
 Alkali Silica Reactivity
 Mass concrete - more than 70% slag

27. GGBF Slag Concrete
Compressive Strength
6000
Grade 120 Slag
Compressive Strength, psi
5000
W/C+M ratio = 0.55
4000
3000
Portland Cement
2000
40% Slag
1000 50% Slag
65% Slag
0
0 5 10 15 20 25 30
Age, days
Ref: ACI 233R

28. GGBF Slag Concrete
Flexural Strength
900
800 Grade 120 Slag
W/C+M ratio = 0.55
Flexural Strength, psi
700
600
500
400
Portland Cement
300
40% Slag
200
50% Slag
100 65% Slag
0
0 5 10 15 20 25 30
Age, days

29. GGBF Slag Concrete
Sulfate Resistance
0.25
Portland Cement (Type II)
Expansion mortar bars, %
0.20 40% Slag
50% Slag
0.15 65% Slag
0.10
0.05
0.00
0 10 20 30 40 50 60 70
Age, Weeks
Ref: ACI 233R

30. GGBF Slag Concrete
Alkali-Aggregate Reactions
0.40
Expansion mortar bars, %
0.30
Portland Cement
40% Slag
0.20
50% Slag
65% Slag
0.10
0.00
0 5 10 15 20
Age, Months
Ref: ACI 233R

31. GGBF Slag Concrete
Heat in Mass Concrete
80
70
Concrete Temperature, C
60
50
40
30
20 Portland Cement
10 70% Slag
0
1 10 100 1000
Age, Hours
Ref: ACI 233R

32. GGBF Slag Concrete
Chloride Permeability
7500
Water-Cement Ratio
Charge Passed, Coulombs
6000 0.70
4500 0.55
0.45
3000
1500
0
Portland cement 25% Slag 50% Slag

33. Slag Cement and the
Environment
 Recovered/ recycled material
 Replaces Portland cement
 Reduction of CO2
 Reduction of Heat
 Reduced Material extraction
 Energy Saving
 Lighter Color

34. LEED Credits
 Leadership in Energy and Environmental Design
(LEED) is a system developed by the
 United States Green Building Council to rate a
building's environmental performance.
 This system has become the principal method by
which buildings can achieve green
 building certification. The system is based on credits
earned in five major categories.
 Slag cement can positively impact several credit
categories

35. LEED Categories
􀁺 Site credit for reduction of heat islands: Use of high-albedo
materials like concrete
produced with slag cement.
􀁺 Materials credit for building reuse: Slag cement makes
concrete structures more
durable.
􀁺 Materials credit for recycled content: Slag cement is a
recycled material used in
concrete.
􀁺 Materials credit for use of local/regional materials: Slag
cement can be considered
a local material in many areas.
For more information on the LEED system, visit www.usgbc.org

36. LEED Categories
 Site credit for reduction of heat islands: Use of high-albedo
materials like concrete produced with slag cement.
 Materials credit for building reuse: Slag cement makes
concrete structures more durable.
 Materials credit for recycled content: Slag cement is a
recycled material used in concrete.
 Materials credit for use of local/regional materials: Slag
cement can be considered a local material in many areas.
 For more information on the LEED system, visit
www.usgbc.org.