Research on Steel Fiber Reinforced Concrete Mix Proportion Based on the Theory of the Orthogonal Exp

Research on Steel Fiber Reinforced Concrete Mix Proportion Based on the Theory of the Orthogonal Experiment Jinsong Lei*1, Zhiping Zhou2, Zhangteng Sun1 College of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang, Sichuan, 621010, China 1

Zhejiang Zhongnan Construction Group Co., Ltd., Hangzhou, Zhejiang, 310051, China

2

*1

leijinsong2003@163.com; 257420187@qq.com; 3948368046@qq.com

Abstract According to the needs of the quick mending engineering in concrete pavement, the theory of orthogonal experiment and the major indicators that influence the performance of steel fiber reinforced concrete, the influence of the various factors’ change on physical and mechanical properties of the mixed steel fiber reinforced concrete is studied, with water‐cement ratio, accelerator, steel fiber content, coarse aggregate gradation as the essential factor. The research shows that flexural strength of steel fiber reinforced concrete increases with the increase of the steel fiber content and decreases with the increase of the water‐cement ratio. In addition, the level of grade aggregate also has an important influence on the flexural strength of steel fiber reinforced concrete. The study figures out the optimum mix proportion of steel fiber reinforced concrete and provide a good reference to engineering application.

Keywords Pavement Concrete; Steel Fiber; Mix Proportion; Orthogonal Experiment; Range Analysis

Introduction Compared with ordinary concrete, steel fiber reinforced concrete in the tensile, bending, shear, torsion strength and impact resistance are improved significantly. Meanwhile, the right amount of steel fiber can also reduce the shrinkage of concrete and improve the fatigue resistant ability of concrete and the durability of concrete [1].

Aiming at the quick mending engineering in concrete pavement, the paper studies the mix proportion of the steel fiber reinforced concrete by combining the situation of the local raw material supply and taking the requirement into consideration that the road returns to normal traffic within 3 days after the

pavement mending. Through the orthogonal experiment [2], the appropriate mix proportion of steel fiber reinforced concrete is chosen, which provides the theoretical principles for the application in practical engineering.

The Preliminary Plan of Heat-Resistant Concrete Raw Materials Combined with the requirement of fast normal traffic after the pavement mending and the actual situation of the car load, the study decides the degree of strength of steel fiber reinforced concrete mixture is C40. The study focuses on indicators of 3d concrete flexural strength, as well as considers 28d the concrete flexural strength, 3d and 28d compressive strength. In order to ensure that the workability of concrete during construction, requirement of concrete slump is between 15 to 30 mm.

Combined with the above requirements, the study decides that cementing material contains P.O42.5R cement, corrugated steel fiber, aggregates: aggregate is mainly divided into fine aggregate and coarse aggregate and fine aggregate is natural sand with fineness modulus of 2.6; and coarse aggregate chooses gravel. After inspection, all the indicators of raw materials are able to satisfy the requirement of regulations.

Orthogonal Test Design It is generally believed that the main factors influencing the strength of steel fiber reinforced concrete are water‐cement ratio, he content of steel fiber and admixture, the coarse aggregate grading, etc.

In order to accurately determine the mix proportion of

18 International Journal of Engineering Practical Research, Vol. 4 No. 1‐April 2015 2326‐5914/15/01 018‐04 © 2015 DEStech Publications, Inc. doi: 10.12783/ijepr.2015.0401.04

Research on Steel Fiber Reinforced Concrete Mix Proportion Based on the Theory of the Orthogonal Experiment 19

among the total quality of aggregate.

the material composition’s quality of the steel fiber concrete, research adopts orthogonal experiment method [2] to test the steel fiber reinforced concrete from four factors and three levels. Details of the experiment is shown in table 1 and table 2. In table 1, “Gradation 1” means that the total quality of aggregate contains 42% sand, 16% gravel with particle size from 10 to 20 mm and 42% the particle size of 20‐40 mm gravel; ʺ Gradation 2ʺ means that there are 40% sand, 21% the particle size of 10‐20 mm gravel and 39% the particle size of 20‐40 mm gravel; ʺGradation 3ʺ means there are 38% sand aggregate, 26% the gravel size of 10‐20 mm, 36%r the particle size of 20‐40 mm of gravel

The mix proportion of steel fiber reinforced concrete in the orthogonal experiment is shown in table 3. The workability of steel fiber reinforced concrete is good with the slump between 15 mm and 38 mm. The initial setting time and final setting time can meet the standard [3] requirements. According to the number of test items, 12 standard samples are done in each group, a total of 108 standard samples in the orthogonal experiment. Then, test samples are moved to standard curing room maintenance. Maintenance conditions meet the specification [4].

TABLE 1 CORRESPONDING SCCEDULE DIMENSIONS WITH THREE FACTORS AND THREE LEVELS

type

A (water‐cement ratio)

B (accelerator (%) )

C(steel fiber(kg/m2))

D(coarse aggregate gradation)

1

0.35

1.0

40

gradation 1

2

0.38

1.5

50

gradation 2

3

0.41

2.0

60

gradation 3

TABLE 2 THE ORTHOGONAL TEST TABLEWITH THREE FACTORS AND THREE LEVELS (TYPE)

test number

A (water‐cement ratio)

B(accelerator)

C(steel fiber)

D(coarse aggregate gradation)

1

1

1

1

1

2

1

2

2

2

3

1

3

3

3

4

1

1

2

3

5

2

2

3

1

6

2

3

1

2

7

3

1

3

2

8

3

2

1

3

9

3

3

2

1

TABLE 3 MIX PROPORTION OF CONCRETEWITH ORTHOGONAL EXPERIMENT (THEMIX PROTION OFQUALITY)

test number

water(kg)

concrete(kg)

sand(kg)

aggregate(kg)

accelerator(kg)

steel fiber(kg)

slump(mm)

1

170

486

755

1043

4.9

40

25

2

164

458

725

1014

7.0

50

20

3

158

452

692

1129

7.1

60

15

4

168

441

698

1139

4.4

50

23

5

166

438

768

1061

6.5

60

38

6

160

420

748

1122

8.4

40

30

7

168

409

744

1115

4.1

60

22

8

164

400

716

1172

6.0

40

17

9

162

396

791

1092

7.9

50

28

TABLE 4 PHYSICAL AND MECHANICS PROPERTIES OF STEEL FIBER REINFORCED CONCRETE

test number

flexural strength(MPa)

compressive strength(MPa)

3d

28d

3d

28d

1

5.82

7.68

48.42

59.13

2

6.09

8.14

49.69

52.72

3

5.92

7.92

52.65

54.87

4

5.27

7.81

41.36

56.29

5

5.72

8.32

46.57

50.38

6

5.21

6.77

39.48

49.89

7

5.39

8.13

38.03

48.71

8

5.19

6.32

39.49

51.68

9

5.20

6.91

43.62

45.58

20 Jinsong Lei, Zhiping Zhou, Zhangteng Sun

TABLE 5 THE RESULT TABLE OFRANGE ANALYSIS

item

3d flexural strength

factor

A

B

C

D

K1

17.83

16.48

16.22

16.74

K2

16.20

17.00

16.56

16.69

K3

15.78

16.33

17.03

16.38

range R

2.05

0.67

0.81

0.36

K1 3d compressive strength

28d flexural strength

28d compressive strength

23.74

23.62

22.90

22.78

22.86

23.04

K3

21.36

21.60

24.37

22.05

range R

2.38

2.02

3.6

0.99

K1

150.76

127.81

127.39

138.61

K2

127.41

135.75

134.67

127.20

K3

121.14

135.75

137.25

133.50

range R

29.62

7.94

9.86

11.41

K1

166.72

164.13

160.70

155.09

K2

156.56

154.78

154.59

151.32

K3

145.97

150.34

153.96

162.84

range R

20.75

13.79

6.74

11.52

When the maintenance of the samples gets to the required time, three samples in each group are taken to do experiments [5] on cube strength. The specific test items and test results of the data are shown in table 4.

Test data is analyzed by the method of range analysis method, including the primary and secondary factors in each group and determining the optimum combination of each set of test.

Through the analysis of the range of the experiment results, the size of the range reflects the strength of the effect of the corresponding factors. The formula of the column i factors is as type: Ri  max Ⅰi ,Ⅱi , Ⅲi , Ⅳi   min Ⅰi ,Ⅱi , Ⅲi , Ⅳi 

Range calculation is shown in table 5. Factor ʺAʺ stands for the water‐cement ratio, ʺBʺ for the accelerator, ʺCʺ for the steel fiber and ʺDʺ for the coarse aggregate. ʺK1ʺ is the sum of the experimental values of the factors on level 1. ʺK2ʺ is the sum of the experimental values of the factors on level 2. ʺK3ʺ is the sum of the experimental values of the factors on level 3.

Drawn from the analysis of all the factors in table 5 are as follows. (1) The influence order of the material 3d flexural strength is water‐cement ratio, steel fiber, accelerator and aggregate. The influence order of the material 28d flexural strength is steel fiber, water‐cement ratio, accelerator and aggregate. The influence order of the material 3d compressive strength is water‐cement ratio, aggregate, steel fiber and accelerator. The influence order of the material

A＞C＞B＞D

22.91

K2

Test Results and Analysis

20.77

factor of progression

C＞A＞B＞D

A＞D＞C＞B

A＞B＞D＞C

28d compressive strength is water‐cement ratio, accelerator, aggregate and steel fiber. (2) Under the condition of the other factors unchanged, the influence of water‐cement ratio on flexural strength and compressive strength of steel fiber concrete is inversely proportional to the size of water‐cement ratio. (3) Steel fiber content has great influence on the 28d flexural strength of concrete, but has less effect on the 3d flexural strength of concrete. This is because in the early stage of the concrete hardening, concrete strength is low and bond strength between concrete and steel fiber is weak. At the later stage of the concrete hardening, concrete strength is significantly increased and the bond strength between concrete and steel fiber increases. On the whole, the steel fiber content has a relatively small impact on the compressive strength of concrete. (4) According to the indicator of 3d flexural strength of steel fiber reinforced concrete, it can be seen that with the increase of dosage of accelerator, the strength of the concrete increase firstly and then decreases, which shows that there exists an optimum value of the dosage of accelerator as to the mixed steel fiber reinforced concrete. (5) The aggregate graduation has great effect on the compressive strength of steel fiber reinforced concrete and has small effect on the flexural strength of concrete. (6) Taking the 3d flexural strength as benchmark, water‐cement ratio of the steel fiber reinforced concrete is 0.35, accelerator 1.5%, steel fiber content 60 kg/m3 and coarse aggregate gradation 2.

Conclusions According to the technical requirements of fast

Research on Steel Fiber Reinforced Concrete Mix Proportion Based on the Theory of the Orthogonal Experiment 21

mending in pavement, some researches on the mix proportion of steel fiber reinforced concrete are carried out. Based on the range theory, the suitable mix proportion of steel fiber reinforced concrete is obtained through the orthogonal experiment. Conclusions are as follows:

REFERENCES

(1) Steel fiber content is mainly influence the flexural strength of steel fiber reinforced concrete. With the increase of dosage of steel fiber, flexural strength of steel fiber reinforced concrete increases. Coarse aggregate gradation mainly affects the compressive strength of steel fiber reinforced concrete.

National Standard of the people’s Republic of China. “JG/T

(2) Water‐cement ratio is the main factor influencing the compressive strength of steel fiber reinforced concrete. The strength of steel fiber reinforced concrete with water‐cement ratio is inversely proportional to the increase.

National Standard of the people’s Republic of China. “GBT 50107‐2010 Standard for Test and Evaluation of Concrete Compression Strength”, Beijing: China Architecture &Building Press, 2010.

3064‐1999, Steel Fiber Reinforced Concrete”, Beijing: China Architecture &Building Press, 1999.

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“JTG F30‐2003, Technical Specifications for Construction of Highway Cement Concrete Pavements”, Beijing: China Communications Press, 2003.

W. Q Liu. “Experiment Design”, Beijing: Tsinghua University Press, 2005.

Z. J. Wang and X. L. Meng. “Steel fiber reinforced concrete basic mechanical properties research”, Concrete, 294(4): 78‐81, 2014.