The document compares ground granulated blast furnace slag (GGBFS) and pulverized fly ash (PFA) as supplementary cementitious materials in concrete. GGBFS performs better than PFA in terms of early strength and workability, but PFA surpasses GGBFS in late strength gain and durability, especially class F fly ash. Overall, GGBFS is superior to PFA based on the criteria evaluated, but class F fly ash shows potential as a supplementary cementitious material.

1. Comparison Between GGBFS (Slag)
and PFA
Hume Concrete Sdn. Bhd.

2. PURPOSE OF RESEARCH
1. To compare the differences between the two main
supplementary cementitious material (SCM) which are
ground granulated blast - furnace slag (GGBFS) and
pulverized fly ash (PFA) as binary admixture in a concrete,
which can be divided into several criteria such as:
– Strength
– Workability
– Durability
2. To point out the best SCM between this two material,
namely GGBFS and PFA.

3. SOURCE OF DATA
• Data was extracted from various sources of
journals and research paper online, such as
ScienceDirect, Scopus, ASCE and Scientific.Net
• These sources are very reliable, and approved,
with sufficient references to back their
findings. Hence, data extracted is legit, and
acceptable.

4. Type of
concrete
Source Mixture
Number
OPC
(%)
GGBFS
(%)
FA
(%)
W/CA
ratio
Self
Compacting
Concrete
(SCC)
1 A 100 0.37
B 40 60
C 30 70
D 40 60
E 40 60
2 A 100 0.44
B 82 18
C 82 18
D 82 18
E 64 36
F 64 36
3 A 100 0.44
B 80 20
C 60 40
D 40 60
E 80 20
F 60 40
G 40 60
5 A 100 0.40
B 40 60
C 20 80
D 10 90
E 40 60
F 20 80
G 10 90
Type of
concrete`
Source Mixture
Number
OPC
(%)
GGBFS
(%)
FA
(%)
W/CA
ratio
Normal
Concrete
4 A 100 0.60
B 50 50
C 50 50
D 100 0.38
E 50 50
F 50 50
6 A 75 25 0.38
B 50 50
C 30 70
D 75 25
E 50 50
F 30 70
G 100

5. Type of concrete Source Mixture Number OPC (%) GGBFS (%) FA (%) W/CA ratio
Self Compacting
Concrete (SCC)
A 100 0.40
B 90 10
C 80 20
D 70 30
E 60 40
F 50 50
G 40 60
H 30 70
I 100
J 90 10
K 80 20
L 70 30
M 60 40
N 50 50
O 40 60
P 30 70
5 A 100
B 90 10
C 80 20
D 70 30
E 60 40
F 50 50
G 100
H 90 10
I 80 20
J 70 30
K 60 40
L 50 50

6. COMPRESSIVE STRENGTH FINDINGS

7. Type of
concrete
Source Mixture
Number
OPC
(%)
GGBFS
(%)
FA (%) W/CA
ratio
Compressive Strength (MPa) Early
Strength
(Rank)
Late
Strength
(Rank)
Strength
gain/day
(MPa/day)
7 Days 28 Days 90 Days
Self
Compacting
Concrete (SCC)
1 A 100 0.37 56.50 64.27 1 1 0.370
B 40 60 51.18 58.91 2 3 0.368
C 30 70 48.33 61.91 3 2 0.647
D 40 60 (C) 40.03 54.19 4 4 0.674
E 40 60 (F) 14.72 23.65 5 5 0.425
2 A 100 0.44 39.00 43.80 4 4 0.229
B 82 18 41.70 54.60 1 2 0.614
C 82 18 (C) 39.70 50.10 3 3 0.495
D 82 18 (F) 37.60 41.00 5 5 0.162
E 64 36 (C) 41.10 56.50 2 1 0.733
F 64 36 (F) 25.60 37.60 6 6 0.571
3 A 100 0.44 73.60 2
B 80 20 (F) 68.00 4
C 60 40 (F) 60.30 6
D 40 60 (F) 42.50 7
E 80 20 72.60 3
F 60 40 74.90 1
G 40 60 65.70 5
5 A 100 0.40 51.90 67.30 1 1 0.733
B 40 60 (C) 26.80 34.10 4 6 0.348
C 20 80 (C) 17.00 40.00 6 4 1.095
D 10 90 (C) 3.30 10.90 7 7 0.362
E 40 60 39.60 52.30 2 3 0.605
F 20 80 37.90 57.60 3 2 0.938
G 10 90 23.10 37.90 5 5 0.705

8. Type of
concrete
Source Mixture
Number
OPC
(%)
GGBFS
(%)
FA (%) W/CA
ratio
Compressive Strength (MPa) Late
Strength
(Rank)
7 Days 28 Days 90 Days
Normal
Concrete
4 A 100 0.60 55.70 1
B 50 50 51.70 2
C 50 50 34.20 3
D 100 0.38 86.10 2
E 50 50 89.90 1
F 50 50 72.80 3
6 A 75 25 (F) 0.38 58.80 3
B 50 50 (F) 37.80 6
C 30 70 (F) 15.60 7
D 75 25 68.50 2
E 50 50 55.60 5
F 30 70 58.60 4
G 100 76.80 1

9. Type of concrete Source Mixture
Number
OPC (%) GGBFS
(%)
FA (%) W/CA ratio Compressive Strength (MPa) Late Strength
(Rank)
Strength gain/day
(MPa/Day)
7 Days 28 Days 90 Days
Normal Concrete 8
(M60)
A 100
0.40
65.12 70.21 10 0.082
B 90 10 68.21 72.35 6 0.067
C 80 20 70.50 74.21 4 0.060
D 70 30 72.42 76.12 3 0.060
E 60 40 77.41 79.91 2 0.040
F 50 50 78.16 83.45 1 0.085
G 40 60 66.41 74.23 7 0.126
H 30 70 60.92 69.30 12 0.135
I 100 68.32 74.12 5 0.094
J 90 10 66.25 78.32 8 0.195
K 80 20 65.31 80.12 9 0.239
L 70 30 64.01 82.61 11 0.300
M 60 40 58.91 84.92 13 0.420
N 50 50 56.42 92.73 14 0.586
O 40 60 54.62 78.53 15 0.386
P 30 70 48.28 69.50 16 0.337
8
(M20)
A 100 26.45 34.12 12 0.124
B 90 10 28.21 38.23 8 0.162
C 80 20 32.12 42.12 6 0.161
D 70 30 36.00 51.22 3 0.245
E 60 40 45.30 54.12 1 0.142
F 50 50 44.20 53.40 2 0.148
G 100 30.11 34.31 11 0.068
H 90 10 30.92 36.20 10 0.085
I 80 20 31.84 38.12 9 0.101
J 70 30 32.20 41.33 7 0.147
K 60 40 28.81 44.50 4 0.253
L 50 50 25.80 42.90 5 0.276

10. Discussion
• For SCC:
– GGBFS dominates early strength.
– Moving towards late strength, PFA mixture tends to gain higher rate of
strength, and produce a significantly more strength when compared to
GGBFS mixture.
– In terms of PFA, there are 2 types being tested, which are Class C and
Class F.
• From results, Class C outperform Class F in terms of early and late strength.
Data shows that Class C PFA performs better than Class F. This mainly because
of the amount of Calcium Oxide (CaO) inside Class C PFA, which seems to be
around 10 times higher than Class F. CaO is the main components which is
responsible for the hydration process, thus in the strength gain.

11. Discussion
• For normal concrete:
– GGBFS outperform PFA in terms of strength, by
referring to source 4 and 6. PFA in source 6 is a Class F
fly ash, which explains the result tabulated.
• PFA only perform much better on extended late
strength (90 days) in terms of rate of strength
gained, and final late strength (90 days),
according to source 8 (60M cement).

12. WORKABILITY & DURABILITY FINDINGS

13. Type of
concrete
Source Mixture
Number
OPC (%) GGBFS (%) FA (%) W/CA
ratio
Rapid Chloride Permeability Test
(Coulombs)
Rate of decreasing
value of RCPT
(Coulombs/day)
Slump
Flow
(mm)
T50 (s)
28 Days 56 Days 90 Days
Self
Compacting
Concrete
(SCC)
1 A 100 0.37 3709 650 3.0
B 40 60 1411 650 3.0
C 30 70 585 650 3.0
D 40 60 (C) 1067 612 2.0
E 40 60 (F) 1509 625 2.0
2 A 100 0.44 5635 5058 9.306 2.0
B 82 18 2520 1834 11.065 1.9
C 82 18 (C) 3810 1386 39.097 3.5
D 82 18 (F) 4901 1171 60.161 1.9
E 64 36 (C) 3240 2286 15.387 5.3
F 64 36 (F) 4159 624 57.016 2.2
3 A 100 0.44 2065 670 1.0
B 80 20 (F) 1224 675 2.0
C 60 40 (F) 1083 730 2.0
D 40 60 (F) 1475 720 1.0
E 80 20 1053 670 3.0
F 60 40 403 710 3.0
G 40 60 282 705 3.0
Normal
Concrete
4 A 100 0.60 6813 5500 21.177 90
B 50 50 703 372 5.339 130
C 50 50 (F) 926 161 12.339 140
D 100 0.38 1877 1780 1.565 80
E 50 50 395 206 3.048 150
F 50 50 (F) 531 144 6.242 110

14. Discussion
• For SCC (Durability):
– GGBFS dominates late RCPT value (28 days). However, moving towards
extended late RCPT (90 days), PFA burst up in terms of rate of
decreasing value of RCPT, and overtake GGBFS in terms of lowest value
of RCPT. Hence, PFA will outperform GGBFS in late RCPT value (90
Days).
– In terms of class of PFA, from the result, for late (28 days) best
durability, class C fly ash dominates class F. However, during extended
late durability test (90 days), class F fly ash dominates class C, both in
terms of rate of decreasing value of RCPT and the lowest value of
RCPT. Hence, for durability, Class F Fly Ash is the best.

15. Discussion
• For normal concrete (Durability):
– GGBFS dominates late RCPT value (28 days). However,
moving towards extended late RCPT (90 days), PFA
(Class F) burst up in terms of rate of decreasing value
of RCPT, and overtake GGBFS in terms of lowest value
of RCPT. Hence, PFA (class F) will outperform GGBFS in
late RCPT value (90 Days).
– No data acquired for the comparison between class C
and class F fly ash for normal concrete.

16. Criteria OPC GGBFS Flying Ash
Class C Class F
Strength
Workability
Durability
Conclusion GGBFS > PFA
Ground granulated blast-furnace slag (GGBFS) performs better than flying
ash in most primary criteria.

17. CONCLUSIONSOURCE TYPE CS 7 CS 28 CS 90 ESG LSG SG/D RCPT 28 RCPT 56 RCPT 90 RODVR/D SF T50 TOTAL
1 GGBFS 1 1 - 1 1 0 - 0 - - 1 0 5
PFA (C) 0 0 - 0 0 1 - 1 - - 0 1 3
PFA (F) 0 0 - 0 0 0 - 0 - - 0 1 1
2 GGBFS 1 1 - 1 1 1 1 - 0 0 - 1 7
PFA (C) 0 0 - 0 0 0 0 - 0 0 - 0 0
PFA (F) 0 0 - 0 0 0 0 - 1 1 - 1 3
3 GGBFS - - 1 - 1 - - - 1 - 0 0 3
PFA (F) - - 0 - 0 - - - 0 - 1 1 2
4 GGBFS 60 - 1 - - 1 1 1 - 0 0 0 - 4
GGBFS 38 - 1 - - 1 1 1 - 0 0 1 - 5
PFA 60 - 0 - - 0 0 0 - 1 1 1 - 3
PFA 38 - 0 - - 0 0 0 - 1 1 0 - 2
5 GGBFS 1 1 - 1 1 0 - - - - - - 4
PFA (C) 0 0 - 0 0 1 - - - - - - 1
6 GGBFS - 1 - - 1 - - - - - - - 2
PFA (F) - 0 - - 0 - - - - - - - 0
8 GGBFS 1 0 - 1 0 0 - - - - - - 2
PFA (?) 0 1 - 0 1 1 - - - - - - 3

18. CONCLUSION
• GGBFS total points: 32
• PFA total points (class C + F) : 18
• Thus, theoretically, and technically, GGBFS is
better than PFA.