1. Development of Ternary
Cementitious systems Containing
Silica Fume and Fly Ash in Concrete
By: Magzoub H. Saad
Professor: Jose A. Pena

2. Literature Review and Background
Concrete
 Concrete is a mixture of paste and aggregates. The
paste, usually composed of Portland cement and water,
coats the surface of the fine and coarse aggregates.
 A properly designed concrete mixture will possess the
desired workability for the fresh concrete and the
required durability and strength for the hardened
concrete.

3. Silica Fume
 A byproduct of the reduction of high-purity quartz with
coal in electric furnaces in the production of silicon and
ferrosilicon alloys.
 Collected as a byproduct in the production of other
silicon alloys such as ferrochromium, ferromanganese,
ferromagnesium, and calcium silicon.
 Consists of very fine vitreous particles with particles
approximately 100 times smaller than the average
cement particle.

4. Benefits of using silica fume in concrete
 Prevents reinforcing steel corrosion in concrete, due to
its extremely low permeability to chloride-ion intrusion
and high electrical resistively.
 High early strengths, assuring increased efficiency and
greater cost effectiveness in production of prestressed
and precast concrete.
 High ultimate compressive strengths (8,000-20,000 psi),
proportionate to amount of silica fume and the water-to-
cementitious ratio.
 Substantially greater resistance to corrosion, abrasion
and erosion, chemical attack and freeze/thaw damage.

5. Fly Ash
 A fine, glass-like powder recovered from gases created by
coal-fired electric power generation.
 U.S. power plants produce millions of tons of fly ash
annually, which is usually dumped in landfills.
 An inexpensive replacement for Portland cement used in
concrete, while it actually improves strength, segregation,
and ease of pumping of the concrete.
 Used as an ingredient in brick, block, paving, and
structural fills.

6. Type of Fly ash
 Two major classes of fly ash;
 Class F is fly ash normally produced from burning
anthracite or bituminous coal. Class F is rarely
cementitious when mixed with water alone.
 Class C is normally produced from the burning of
subbituminous coal and lignite. Class C fly ash usually
has cementitious properties in addition to pozzolanic
properties due to free lime.

8. Benefits of using fly ash in concrete
 Fresh Concrete Workability: Fly ash increases the
absolute volume of cementitious materials therefore, the
paste volume is increased, then the workability
increased .
 Bleeding: Fly ash in concrete mixtures usually reduces
bleeding by providing greater fines volume and lower
water content for a given workability.

9.  Time of Setting: All Class F and most Class C fly ashes
increase the time of setting of concrete.
 Strength of Hardened Concrete: Fly ash concrete gains
strength slowly with time, that due to relatively slow
pozzolanic reaction.
 Reduces the greenhouse gas signature of concrete, as
the production of one tone of Portland cement produces
one tone of carbon dioxide (CO2).

10. Materials Preparation
 To prepare the materials needed, there are several tests
required.
 Water content: a known amount of aggregate is
obtained, heated to remove the moisture, and the
percentage of moisture determined.
 Sieve Analysis: To determines the relative proportions of
different grain sizes as they are distributed among certain
size ranges.

11. Sieve Analysis Shaker with Stake of Sieves

12.  To calculate the weight of constituent materials;
 First, determine the job parameters- aggregate size,
slump, water/cement ratio, and admixtures if any.
 Second, calculate the batch weights with 5% extra for
waste.
 For this project the slump is 3-4 inches, water/ cement
ratio is 0.41, the maximum nominal size of coarse
aggregate is 3/4 inches.

13. Weights of materials
The total weight of constituent materials are shown in
table below
Cement Water Fine Aggr Coarse Aggr Silica Fume Fly Ash
Mix1 34.86 lb 24 lb 46 lb 150 lb 2.91 lb 20.34 lb
Mix2 40.67 lb 24 lb 46 lb 150 lb 2.91 lb 14.53 lb
Mix3 46.48 lb 24 lb 46 lb 150 lb 2.91 lb 8.72 lb

14. Concrete Mixer Machine

15. Slump Test

16. Sample of Specimen

17. Compressive Strength of Cylindrical Concrete
Specimens
 The objective of this test is to determine the compressive
strength of cylindrical concrete specimens.
 The test method consists of applying a compressive
axial load to molded cylinders at a rate that is within a
prescribed range until failure occurs.

18. Tinius Olsen Test Machine

19. Results

20. Column Graph show compressive strength versus time for
Mix1
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
3 3 3 3 3 7 7 7 7 7 14 14 14 14 14 21 21 21 21 21 28 28 28 28 28
Time (Day)
Compressive Strength (PSI)
3 14 21 287

21. Compressive Strength versus Time for Mix1
4000
4500
5000
5500
6000
6500
7000
7500
8000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Time (Day)
CompressiveStrength(PSI)

22. Column Graph show compressive strength versus time for
Mix2
0
1000
2000
3000
4000
5000
6000
7000
8000
3 3 3 3 3 7 7 7 7 7 14 14 14 14 14 21 21 21 21 21 28 28 28 28 28
Time (Day)
CompressiveStrength(PSI)
3 7 14 21 28

23. Compressive Strength versus Time for Mix2
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Time (Day)
CompressiveStrength(PSI)

24. Column Graph show compressive strength versus time for
Mix3
0
2000
4000
6000
8000
10000
12000
3 3 3 3 3 7 7 7 7 7 14 14 14 14 14 21 21 21 21 21 28 28 28 28 28
Time (Day)
CompressiveStrength(PSI)
3 7 14 21 28

25. Compressive Strength versus Time for Mix3
6000
6500
7000
7500
8000
8500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
Time(Day)
CompressiveStrength(PSI)

26. Discussion
 The compressive strength of all concrete mixes
increased when the age of the concrete increased. This
normal for all concrete, gaining strength with time.
 The target of the compressive strength at day 28 is 6000
psi, this target selected at materials preparation when
choosing the water/cement ratio (0.41).

27.  Mix1 reached the compressive strength of 6000 psi
approximately at day 10, therefore the compressive
strength increased by 29% with respect to compressive
strength at day 28 (6000 psi).
 Silica fume has been shown improve early age strength
of concrete while fly ash improves the late age strength
of the concrete.

28.  Silica fume is added to prevent the formation of free
calcium hydroxide crystals in the cement matrix, which
might reduce the strength at the cement-aggregate
bond.
 Silica fume and fly ash are pozzolanic materials.

29.  A pozzolan is "a siliceous or siliceous and aluminuos
material which in itself possesses little or no
cementitious value but which will, in finely divided form
and in the presence of moisture, chemically react with
calcium hydroxide at ordinary temperature to form
compounds possessing cementitious properties".

30.  Calcium hydroxide is a chemical compound with the
chemical formula Ca(OH)2.
 Calcium hydroxide is available in the system due to the
chemical reaction of C3S (Tricalcium silicate) and C2S
(Dicalcium silicate).
 The compressive strength of Mix2 increased by 13%
with respect to compressive strength at day 28 (6000
psi).

31.  The compressive strength of Mix3 increased by 38%
with respect to compressive strength at day 28 (6000
psi).
 This mixture is the optimum one, because at day 3, the
compressive strength, exceeded the compressive
strength of day 28 (6000 psi) of the design mix
procedure.

32.  The proportion of Mix3 is 80% Portland cement, 15% fly
ash, and 5% silica fume replacement of the total cement
weight (100%).
 Mix3 could be considered a high-strength concrete.
 High-strength concrete has a compressive strength
generally greater than 6,000 psi.
 High-strength concrete is made by lowering the water-
cement (w/c) ratio to 0.35 or lower.

33. Compressive Strength versus Time for Mix1, Mix2, & Mix3
3000
4000
5000
6000
7000
8000
9000
0 7 14 21 28 35
Time (Day)
CompressiveStrength(PSI)
Mix 1
Mix 2
Mix 3
78.6%
47.2%
21.9%
7.1%

34.  The compressive strength results over time in days for
Mix1, Mix2, and Mix3.
 Mix1 with low cement percentage (60%), Mix2 with
medium cement percentage (70%), and Mix3 with high
cement percentage (80%).
 For all mixes, the compressive strength increased with
time.

35.  The compressive strength of Mix3 increased by 78.6% of
Mix2 at day 3, but at day 28, the percentage increasing
of Mix3 over Mix2 is 21.9%.
 Also the compressive strength of Mix3 increased by
47.2% of Mix1 at day 3, and at day 28 the percentage
increasing of Mix3 over Mix1 is 7.1%.

36. Conclusion
 Based on compression test results using Tinius Olsen
machine, the following conclusions are obtained
1. High percentage of fly ash (35%) with low percentage
of silica fume (5%) replacement of Portland cement type
I produce high strength concrete, and this strength
increase with the age of the concrete.
2. Mix3 has the most compressive strength, with
proportion of 80% Portland cement, 15% fly ash, and 5%
silica fume.

37. 3. Reduction of fly ash replacement, increase the
strength of the concrete at early age with high amount,
but at 28 days or more the difference between high
percentage and low percentage of fly ash replacement is
very low.
4. Fly ash with small amount of silica fume can be an
economic alternative to ordinary Portland cement.

38. Acknowledgements
 Professor Jose A. Pena for his time, advice, and
assistance.
 Lab instructor Pete Peters for his help during mixing,
curing, and testing the specimens.
 The faculty members of the Construction Management
and Technologies at Purdue University Calumet for
teaching me construction, management, and engineering

39. Thanks……