An Experimental Study of Fibrous Triple Blended High Strength Concrete with Fly Ash and Condensed Silica Fume

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An Experimental Study of Fibrous Triple Blended High Strength Concrete with Fly Ash and Condensed Silica Fume

Abdullah Mohammed Veranna Gugulothu

Assistant Professor Pg Scholar

Nalgonda, India Nalgonda, India

Table 1.1

Physical properties of cement

Components

Results

Require

ments

1.

Normal consistency

28.66%

Min 300

2.

Specific gravity

2.99

——

3.

Initial setting time

Final setting time

30 min

160 min

Min 30

4.

Soundness (expansion)

lechatlier Method

2 min

Max 600

5.

Fineness of cement

3050

Max 10

6.

Compressive strength of cement mortar cubes

  1. 7 days

  2. 28 days

33 N/mm²

52 N/mm²

Min 33

Abstract – Concrete is the most widely used construction material employed for the construction of various types of structures including buildings, roads, bridges, dams etc. Since many centuries, there have been several mere structures and some civil engineering marvels that have been constructed over time all over the world. Some with the idea to shelter people or to store water etc. while some with the idea of creating a historical symbol like the India Gate.

Keywords: Compressive Strength Flexural Strength Of Concrete Flyash And Silica Fume.

INTRODUCTION

Concrete, is one of the key construction materials having good compressive &, flexural strengths and durable properties among others. With comparative low cost made from some of the most widely available elements, it has found wide usage. It is mouldable, adaptable and relatively fire resistant. The fact that it is an engineered material which satisfy almost any reasonable set of performance specifications, more than any other material currently available has made it immensely popular construction material. In fact, every year more than 1 m3 of concrete is produced per person (more than 10 billion tonnes) worldwide.

What is trible blended concrete?

Triple blended concretes belong to that strata of concretes where the strength and durability characteristics are maximized to the highest extent possible, in comparison to various other types of concretes, by subtle tailoring of its chemical composition, fineness and particle size distribution. Greater varieties are introduced by the incorporation of additives like pozzolana, granulated slag or inert fillers. These lead to different specification of cements in national and international standards.

EXPERIMENTAL INVESTIGATIONS

Materials Used In Present Work Cement

Ordinary Portland cement 53 grade brand conforming to

I.S.I standard is used in the present investigation. The physical properties of cement are listed in the Table 1.1

Fine Aggregate

The locally available sand is used as fine aggregate in the present investigation. The sand is free from clayey matter, salt and organic impurities. The sand is tested for various properties like specific gravity, bulk density etc., in accordance with IS 2386-1963(28). Grain size distribution of sand shows that it is close to the zone 1 of IS 383- 1970(29). The properties of sand are shown in Table 1.2

Table 1.2

Physical properties of fine aggregate

Property

Result

Remarks

1.

Specific gravity

2.68

——–

2.

Density

1640 kg/m³

———

3.

Fineness Modulus

2.78

——–

Coarse Aggregate

Machine crushed angular granite metal from the local source is used as coarse aggregate. It is free from impurities such as dust, clay particles and organic matter etc. The coarse aggregate is also tested for its various properties.

The specific gravity and fineness modulus of coarse aggregate are 2.64, 7.14 respectively. The bulk density of coarse aggregate is 1700 kg/m³. The details are tabulated in table 3.6. Sieve analysis is carried out ant grading results are shown in the Table 1.3.

Table 1.3

Properties of coarse aggregate

Property

Value

Remarks

1.

Specific Gravity

2.64

——-

2.

Density

1700kg/m³

——–

3.

Fineness Modulus

7.14

——–

Fly Ash

Table- 1.4

physical properties of fly ash

Property

Results

1

Particle Size

1 to 150 µm

2

Fineness

7-12 µm

3

Specific Gravity

1.3-4.8

Fly ash, an artificial pozzolanna is the unburned residue resulting, from combustion of pulverized coal or lignite. It is collected by mechanical or electrostatic separators called hoppers from flue gasses of power plants where powdered coal is used as fuel. This material, once considered as a by- product finding difficulty to dispose off, has now become a material of considerable value when used in conjunction with concrete as an admixture. Its physical and chemical properties are shown in the table 1.4 & 1.5.

Table-1.6

Physical properties of fly ash

Property

Results

1

Particle Size

< 1 µm

2

Bulk Density

130-430 kg/m³

3

Specific Gravity

1.3-4.8

4

Specific Surface

15000-30000 m²/kg

Table 1.7

Chemical properties of fly ash

Constituents

Value(%)

Remarks

1

SiO2

>85%

—-

2

Amorphous

highly

——

Water

Potable water has been used in the experiment for

Table 1.5

Chemical properties of fly ash

Constituents

Value(%)

Remarks

SiO2

49-67

Al2O3

16-33

Fe2O3

4-10

CaO

1-4

MgO

0.2-2.

—-

SO3

0.1-2.0

Na2O

0.1-0.2

K2O

0.1-1.0

LOI

0.1-1.6

Silica Fume

Condensed Silica fume, also known as microsilica, is a dry amorphous powder which, when added with standard cements will increase the durability and strength of the concrete as well as reducing permeability and improving abrasion-erosion resistance. It may also be used in many applications where high strength is required.

The addition of silica fume produces concrete with reduced permeability resulting in increased water tightness enhanced chemical resistance and reduced corrosion of reinforcing steel. Its physical and chemical properties are shown in the table 1.6 & 1.7

mixing and curing.

Super Plasticizer

The super plasticizer used in this experiment is SP430.

It is manufactured by FOSROC.

Super plasticizers are new class of generic materials which when added to the concrete causes increase in the workability. They consists mainly of naphthalene or melamine sulphonates, usually condensed in the presence of formaldehyde.

RESULTS AND DISCUSSION

Compressive Strength

Compressive strength of M80 grade concrete cubes with various percentages of Fly ash, Silica Fume & Fibre:

  1. Variation of compressive strength at 28 days with addition of 0% fibre by volume of concrete and with various

    Table- 1.8

    Compressive Strength (MPa) of Concrete

    Silica fume %

    Fly ash

    %

    Compressive Strength, MPa

    28 days

    % increase over

    0%

    1

    0

    0

    76.24

    2

    5

    0

    77.89

    2.16

    3

    10

    0

    78.94

    3.54

    4

    15

    0

    78.42

    2.85

    5

    0

    20

    77.59

    1.77

    6

    5

    20

    78.50

    2.96

    7

    10

    20

    79.48

    4.24

    8

    15

    20

    79.25

    3.94

    9

    0

    40

    77.12

    1.15

    10

    5

    40

    78.26

    2.64

    11

    10

    40

    79.19

    3.86

    12

    15

    40

    78.75

    3.29

    % of Silica Fume and Fly ash

  2. Variation of compressive strength at 28 days with addition of 0.5% fibre by volume of concrete and with various % of Silica Fume and Fly ash

    Table- 1.9

    Compressive Strength (MPa) of Concrete

    Silica fume %

    Fly ash

    %

    Compressive Strength, MPa

    28 days

    % increase over

    0%

    1

    0

    0

    77.21

    2

    5

    0

    78.94

    2.24

    3

    10

    0

    79.47

    2.92

    4

    15

    0

    79.15

    2.51

    5

    0

    20

    78.14

    1.20

    6

    5

    20

    79.59

    3.08

    7

    10

    20

    79.96

    3.56

    8

    15

    20

    79.56

    3.04

    9

    0

    40

    77.83

    0.80

    10

    5

    40

    79.18

    2.55

    11

    10

    40

    79.62

    3.12

    12

    15

    40

    79.38

    2.81

  3. Variation of compressive strength at 28 days with addition of 1% fibre by volume of concrete and with various

Table- 2.0

Compressive Strength (MPa) of Concrete

Silica fume %

Fly ash

%

Compressive Strength, MPa

28 days

% increase over

0%

1

0

0

79.69

2

5

0

80.23

0.67

3

10

0

80.68

1.24

4

15

0

80.29

0.75

5

0

20

80.17

0.60

6

5

20

80.78

1.36

7

10

20

81.20

1.89

8

15

20

80.64

1.19

9

0

40

79.98

0.36

10

5

40

80.51

1.02

11

10

40

80.82

1.41

12

15

40

80.40

0.89

% of Silica Fume and Fly ash

Flexural strength

Flexural strength of M80 grade concrete beams with various percentages of Fly ash, Silica Fume & Fibre:

  1. Variation of flexural strength at 28 days with addition of 0% fibre by volume of concrete and with various % of Silica Fume and Fly ash

    Table- 2.1

    Flexural Strength (MPa) of Concrete

    Silica fume %

    Fly ash

    %

    flexural Strength, MPa

    28 days

    % increase over

    0%

    1

    0

    0

    6.40

    2

    5

    0

    6.90

    7.81

    3

    10

    0

    7.10

    10.93

    4

    15

    0

    6.90

    7.81

    5

    0

    20

    6.60

    3.12

    6

    5

    20

    7.10

    10.93

    7

    10

    20

    7.31

    14.21

    8

    15

    20

    7.10

    10.93

    9

    0

    40

    6.50

    1.56

    10

    5

    40

    7.00

    9.37

    11

    10

    40

    7.20

    12.50

    12

    15

    40

    7.02

    9.68

  2. Variation of flexural strength at 28 days with addition of 0.5% fibre by volume of concrete and with various % of Silica Fume and Fly ash

    Table- 2.2

    Flexural Strength (MPa) of Concrete

    Silica fume %

    Fly ash

    %

    flexural Strength, MPa

    28 days

    % increase over

    0%

    1

    0

    0

    7.17

    2

    5

    0

    7.40

    3.20

    3

    10

    0

    7.70

    7.39

    4

    15

    0

    7.60

    5.99

    5

    0

    20

    7.30

    1.81

    6

    5

    20

    7.60

    5.99

    7

    10

    20

    7.90

    10.18

    8

    15

    20

    7.80

    8.78

    9

    0

    40

    7.20

    0.41

    10

    5

    40

    7.50

    4.60

    11

    10

    40

    7.80

    8.78

    12

    15

    40

    7.70

    7.39

  3. Variation of flexural strength at 28 days with addition of 1% fibre by volume of concrete and with various % of Silica Fume and Fly ash

Table- 2.3

Flexural Strength (MPa) of Concrete

Silica fume %

Fly ash

%

flexural Strength, MPa

28 days

% increase over

0%

1

0

0

7.50

2

5

0

7.80

4.0

3

10

0

8.10

8.0

4

15

0

8.00

6.66

5

0

20

7.70

2.66

6

5

20

8.04

7.2

7

10

20

8.40

12.0

8

15

20

8.20

9.33

9

0

40

7.60

1.33

10

5

40

7.90

5.33

11

10

40

8.20

9.33

12

15

40

8.10

8.0

Graphs

  1. Graphs depicting results for compressive strength

    Graph 1: variation of compressive strength with various percentages of Fly ash and Silica Fume with 0% fibre

    Graph 2: variation of compressive strength with various percentages of Fly ash and Silica Fume with 0.5% fibre

    Graph 3: variation of compressive strength with various percentages of Fly ash and Silica Fume with 1% fibre

  2. Graphs depicting results for flexural strength

Graph 1: variation of flexural strength with various percentages of Fly ash and SilicaFume with 0% fibre

Graph 2: variation of flexural strength with various percentages of Fly ash and SilicaFume with 0.5% fibre

Graph 3: variation of flexural strength with various percentages of Fly ash and SilicaFume with 1% fibre

CONCLUSIONS

The following conclusions are drawn from this study:

  1. Higher dosages of superplasticizer are required for high strength concrete mixes particularly when mineral admixtures and fibres were employed to maintain workability.

  2. For this combination of 10% silica fume with 20% fly ash the compressive strength has shown an increase from 2 to 7 % with various percentages of fibre

  3. 20% fly ash generates marginal increase in strength. To compensate for the loss of strength when higher percentages of fly ash is used silica fume is added

  4. Fly ash is pozzolanic in nature and slowly reacting and it requires longer curing periods even beyond 28 days to generate high strength particularly when percentage is more

  5. As the percentage of steel fibre is increased there is marginal increase in the compressive strength for all the combinations

  6. For this combination of 10% silica fume with 20% fly ash the compressive strength has shown an increase from 15 to 31.5 % with various percentages of fibre

  7. As the percentage of steel fibre is increased there is higher increase in the flexural strength for all the combinations

  8. An optimum high strength concrete mix possessing optimum strength properties can be obtained resorting to triple blending.

REFERENCES

  1. IS : 516 1959 : Indian standard Methods of Tests for strength of Concrete Bureau of Indian Standards

  2. IS : 4037 1988 : Indian standard methods of physical test for Hydraulic cement Bureau of Indian Standards

  3. IS : 1344 1968 : Indian standard specifications for pozzalonas –

    Bureau of Indian Standards

  4. IS : 2386 1963 : Indian Standards methods for aggregates of concrete Bureau of Indian standards, New Delhi

  5. IS : 380 1970 : Indian standard specifications for coarse and fine aggregates (natural) – Bureau of Indian Standards (revised)

  6. IS : 7869 (part 2) 1981 : Indian standard specifications for admixtures in concrete

  7. IS : 456 2000 : Plain and reinforced concrete Indian standard specifications

  8. A.M Neville (1998) : Properties of concrete English language book society

  9. N. Krishnaraju : Design of concrete mix CBS publisher 1985

  10. M.S Shetty : Concrete Technology 2006

  11. P.K Mehta and J.J.M Paulo : Concrete micro structure and properties and materials- McGraw Hill publishers 1997

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