Portland cement is the most important ingredient of concrete and is a versatile and relatively high cost material. Large scale production of cement is causing environmental problems on one hand and depletion of natural resources on other hand. This threat to ecology has led to researchers to use industrial by products as supplementary cementations material in making concrete. In this study, an attempt has been made to investigate the strength parameters of concrete made with partial replacement of cement by silica fume.

1. STRENGTHOF SILICA FUME
CEMENT CONCRETE
BY:
FARHAN HUSSAIN WAGAN
IRRIGATION DEPARTMENT
SINDH,PAKISTAN

2. INTRODUCTION
 Portland cement is the most important
ingredient of concrete and is a versatile and
relatively high cost material. Large scale
production of cement is causing environmental
problems on one hand and depletion of natural
resources on other hand. This threat to ecology
has led to researchers to use industrial by
products as supplementary cementations
material in making concrete. In this study, an
attempt has been made to investigate the
strength parameters of concrete made with
partial replacement of cement by silica fume.

3. LITERATURE VIEW
 The early work done in Norway containing
silica fume, had very high strengths and low
porosities. Since then silica fume usage and
development has continued making it one of
the world's most valuable and versatile
admixtures and cementations products.

4.  Yogendran et al (1987), investigated on silica
fume in high strength at a constant water
binder action (b/w) of 0.34 and replacement
percentages of 0 to 25, with varying dosages
of HRWKA. The maximum 28 days
compressive strength was obtained at 15%
replacement level.

5.  Hooten RDC (1993) investigated on influence
of silica fume replacement of cement on
physical properties and resistance to sulphate
attack, freezing and thawing, and alkali silica
reactivity. He reported that maximum 28 days
compressive strength was obtained at 15%
silica fume replacement level, at w/c ratio of
0.35 with variable dosages of HRWRA.

6. AIMS ANDOBJECTIVES:
 The main aim of this study is to investigate the
effort of using different dosage or percentage
of Silica fume in ordinary concrete under 28
days curing conditions on its compressive
strength, tensile strength and flexural strength.

7.  To study the strength development in concrete with different dosage of
Silica fume
 To study the effect on compressive strength, Tensile strength and
flexural strength using different dosage of Silica fume cure under 28
days.
 To compare the results of the concrete containing Silica fume with
controlled concrete (without Silica fume)
 4 To reduce the environmental problems caused by the large scale
production of cement.
 5. To reduce the cost of material by using silica fume as partial
replacement of cement with high cost material.
 To improve the strength of concrete.
 To use the by- product industrial waste materials.
 To bring awareness to civil engineers regarding advantages of new
concrete mix.
 Following are the objectives regarding to achieve theFollowing are the objectives regarding to achieve the
aimaim

8. Experimental Study
 This is detailed experimental study on
compressive strength, Spilt tensile strength
and flexural strength at the age of 28 days of
M20 grade concrete with partial replacement
of cement by silica fume by 0,5,10,15,20, 25%
percentage. Increase in compressive, split
tensile and flexural strength of concrete is
compared with normal concrete. Test results
are indicated in tables and graphs.

9.  Materials
1. Concrete mix: Characteristic strength at 28 days = 20 MPa
2. Type of cement: OPC
3. Type and size of coarse aggregate: Crushed and of max. size = 20mm
4. W/C ratio: constant (0.46 determined from mix design)
5. Mix ratio: 1 : 1.38 : 3.5

10. Mix proportion for M20 grade concrete
MaterialsMaterials
controlcontrol SFSF
5%5%
SFSF
10%10%
SFSF
15%15%
SFSF
20%20%
SFSF
25%25%
Cement (Kg)Cement (Kg) 380380 361361 342342 323323 304304 285285
Silica fume (Kg)Silica fume (Kg) 00 1919 3838 5757 7676 9595
Fine aggregate (Kg)Fine aggregate (Kg) 523.5523.5 523.5523.5 523.5523.5 523.5523.5 523.5523.5 523.5523.5
Coarse aggregate (Kg)Coarse aggregate (Kg) 1346.51346.5 1346.51346.5 1346.51346.5 1346.51346.5 1346.51346.5 1346.51346.5
Water (Kg)Water (Kg) 190190 190190 190190 190190 190190 190190
W/CW/C 0.460.46 0.460.46 0.460.46 0.460.46 0.460.46 0.460.46

11. Equipments
Figure 1 Flexural Strength Testing
Machine

12. Figure 2 Specimen after testing

13. RESULTS ANDDISCUSSION
1. Compressive Strength Of Cube
 The results of cube compressive strength of
normal concrete and silica fume concrete are
presented in Table 1. The graph between cube
compressive strength and % cement replaced
by SF is presented in Figure 1.
 Table 1 and Figure 1 depicts that when cement
is replaced by SF the maximum 28 days cube
compressive strength observed as 32.44
N/mm2 (15.19% higher over normal concrete).
The maximum cube compressive strength is
observed at 10% replacement of silica fume.

14.  Table 1 Compressive Strength of Cube ( N/mm2
)

15. Compressive Strength Of Cube
28.16
20.53
32.44
28.57
26.64
24.67
0
5
10
15
20
25
30
35
0 5 10 15 20 25 30
Percentage Of Silica Fume
CompressiveStrength
Compressive Strength
Series2
Fig. 1 Graph showing the Cube compressive strength
of silica fume concrete with respect to % of silica
fume

16.  2. Compressive strength of Cylinder
 The results of cylindrical compressive strength of
normal concrete and silica fume concrete are
presented in Table 2. The graph between
cylindrical compressive strength and % cement
replaced by SF is presented in Figure 2.
 Table 2 and Figure 2 show that the maximum 28
days cylindrical compressive strength observed
is 26.51 N/mm2 (36.36% higher over normal
concrete). The maximum cylindrical compressive
strength is observed at 10% replacement of
silica fume.

17.  Table 2 Compressive Strength Of Cylinder( N/mm2
)

18. Compressive Strength Of Cylender
19.44
15.79
26.51
21.26 20.9
20.06
0
5
10
15
20
25
30
0 5 10 15 20 25 30
Percentage Of Silica Fume
CompressiveStrength
Compressive Strength
Fig. 2 Graph showing the cylindrical compressive strength of silica
fume concrete with respect to % of silica fume

19.  Spilt tensile strength
 The result of spilt tensile strength of normal
concrete and silica fume concrete are presented in
Table 3 the graph between spilt tensile strength
and % cement replaced by SF is plotted and
presented in Figure 3.
 Table 3 and Figure 3 depicts that when cement is
replaced by SF the maximum 28 days spilt tensile
strength is observed as 2.81 n/mm2 (23.24% more
than that of normal concrete). The maximum spilt
tensile strength is observed at 10% replacement of
silica fume.


20.  Table 3 Tensile Strength Of Cylinder( N/mm2 )

21. Tensile Strength Of Cylender ( N/mm2 )
2.28
1.97
2.81
2.4
2.23
2.37
0
0.5
1
1.5
2
2.5
3
0 5 10 15 20 25 30
Percentage Of Silica Fume
TensileStrength
Tensile Strength
Fig. 3 Graph showing the cylindrical tensile strength of silica fume
concrete with respect to % of silica fume

22.  Flexural Strength
 The results of flexural strength of normal
concrete and silica fume concrete are
presented in Table 4 The graph between
flexural strength and % cement replaced by SF
is plotted and shown in Figure 4.
 Table 4 and Figure 4 shows that the maximum
28 days flexural strength as observed as 8.29
N./mm2 (55.53 % more than that of normal
concrete) the maximum flexural strength is
observed at 15% replacement of silica fume

23.  Table 4 Flexural Strength Of Beam/prism( N/mm2 )

24. Flexural Strength Of Beam/prism ( N/mm2 )
5.33
7.44
6.02
8.29
3.76
3.97
0
1
2
3
4
5
6
7
8
9
0 5 10 15 20 25 30
Percentage Of Silica Fume
FlexuralStrength
Flexural Strength
Fig. 4 Graph showing the prism flexural strength of silica fume
concrete with respect to % of silica fume

25. 
Conclusion
 The maximum compressive strength, spilt tensile strength
of silica fume concrete is observed at 10% replacement of
cement with silica fume.
 The maximum flexural strength is observed at 15% of
cement replacement with silica fume.
 The cube compressive strength, cylindrical compressive
strength, spilt tensile strength and flexural strength are
15.19%, 36.36% , 23.24% and 55.53%, more than those of
normal concrete respectively
 Silica fume seems to have a more pronounced effect on
the flexural strength than the spilt tensile strength.

26.  Suggestions
 Since the strength of silica fume concrete is more
than normal concrete so this type of concrete
may be used where high strength is required.
 To save the quantity of cement, silica fume
concrete may be used.
 To reduce environment problems on one hand and
to utilize by product industrial waste material on
the other hand, this type of concrete may be
used.

27. Thanks