STRENGTH OF SILICA FUME CEMENT CONCRETE

BY:FARHAN HUSSAIN WAGANIRRIGATION DEPARTMENT SINDH,PAKISTAN

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.

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.

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.

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.

AIMS AND OBJECTIVES: 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.

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 Following are the objectives regarding to achieve the aimthe aim

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.

Materials1. 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

Mix proportion for M20 grade concrete

MaterialsMaterialscontrcontrolol

SFSF 5%5%

SF SF 10%10%

SF SF 15%15%

SF SF 20%20%

SF SF 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 Coarse aggregate (Kg)(Kg)

1346.1346.55

1346.1346.55

1346.1346.55

1346.1346.55

1346.1346.55

1346.1346.55

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

Equipments

Figure 1 Flexural Strength Testing Machine

Figure 2 Specimen after testing

RESULTS AND DISCUSSION

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.

Table 1 Compressive Strength of Cube ( N/mm2 )

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

Com

pres

sive

Str

engt

h

Compressive StrengthSeries2

Fig. 1 Graph showing the Cube compressive strength of silica fume concrete with respect to % of silica

fume

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.

Table 2 Compressive Strength Of Cylinder ( N/mm2 )

Compressive Strength Of Cylender

19.44

15.79

26.51

21.26 20.920.06

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Percentage Of Silica Fume

Com

pres

sive

Str

engt

h

Compressive Strength

Fig. 2 Graph showing the cylindrical compressive strength of silica fume concrete with respect to % of silica fume

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.

Table 3 Tensile Strength Of Cylinder ( N/mm2 )

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

Tens

ile S

tren

gth

Tensile Strength

Fig. 3 Graph showing the cylindrical tensile strength of silica fume concrete with respect to % of silica fume

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

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

Flexural Strength Of Beam/prism ( N/mm2 )

5.33

7.44

6.02

8.29

3.763.97

0

1

2

3

4

5

6

7

8

9

0 5 10 15 20 25 30

Percentage Of Silica Fume

Flex

ural

Str

engt

h

Flexural Strength

Fig. 4 Graph showing the prism flexural strength of silica fume concrete with respect to % of silica fume

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.

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.

Thanks