Scholarly article on topic 'Mechanical properties of self-compacted fiber concrete mixes'

Mechanical properties of self-compacted fiber concrete mixes Academic research paper on "Civil engineering"

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Abstract of research paper on Civil engineering, author of scientific article — Mounir M. Kamal, Mohamed A. Safan, Zeinab A. Etman, Bsma M. Kasem

Abstract Increased productivity and improved working environment have had high priority in the development of concrete construction over the last decade. The major impact of the introduction of self-compacting concrete (SCC) is connected to the production process. The productivity is drastically improved through the elimination of vibration compaction and process reorganization. The working environment is significantly enhanced through avoidance of vibration induced damages, reduced noise and improved safety. Additionally, SCC technology has improved the performance in terms of hardened concrete properties like surface quality, strength and durability. The main objective of this research was to determine the optimum content of fibers (steel and polypropylene fibers) used in SCC. The effect of different fibers on the fresh and hardened properties was studied. An experimental investigation on the mechanical properties, including compressive strength, flexural strength and impact strength of fiber reinforced self-compacting concrete was performed. The results of the investigation showed that: the optimum dosage of steel and polypropylene fiber was 0.75% and 1.0% of the cement content, respectively. The impact performance was also improved due to the use of fibers. The control mix specimen failed suddenly in flexure and impact, the counterpart specimens contain fibers failed in a ductile manner, and failure was accompanied by several cracks.

Academic research paper on topic "Mechanical properties of self-compacted fiber concrete mixes"

HBRC Journal (2013) xxx, xxx-xxx

Housing and Building National Research Center L f ^ . HBRC Journal li"!i"I~l

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1 http://ees.elsevier.com/hbrcj

FULL LENGTH ARTICLE

Mechanical properties of self-compacted fiber concrete mixes

Mounir M. Kamal a, Mohamed A. Safan a, Zeinab A. Etman a *, Bsma M. Kasem b

a Department of Civil Engineering, Faculty of Engineering, Menoufia University, Egypt b Civil Engineer and Postgraduate Fellow, Ministry of irrigation and Water Resources, Egypt

Received 12 February 2013; revised 3 May 2013; accepted 23 May 2013

Housing and Building National Research Center HBRC Journal

http://ees.elsevier.com/hbrcj

ARTICLE

KEYWORDS

Steel fibers; Polypropylene fibers; Impact;

Self-compacted concrete; Compressive strength

Abstract Increased productivity and improved working environment have had high priority in the development of concrete construction over the last decade. The major impact of the introduction of self-compacting concrete (SCC) is connected to the production process. The productivity is drastically improved through the elimination of vibration compaction and process reorganization. The working environment is significantly enhanced through avoidance of vibration induced damages, reduced noise and improved safety. Additionally, SCC technology has improved the performance in terms of hardened concrete properties like surface quality, strength and durability. The main objective of this research was to determine the optimum content of fibers (steel and polypropylene fibers) used in SCC. The effect of different fibers on the fresh and hardened properties was studied. An experimental investigation on the mechanical properties, including compressive strength, flex-ural strength and impact strength of fiber reinforced self-compacting concrete was performed. The results of the investigation showed that: the optimum dosage of steel and polypropylene fiber was 0.75% and 1.0% of the cement content, respectively. The impact performance was also improved due to the use of fibers. The control mix specimen failed suddenly in flexure and impact, the counterpart specimens contain fibers failed in a ductile manner, and failure was accompanied by several cracks.

© 2013 Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research

Center.

Introduction

* Corresponding author. Tel.: +20 1009727355; fax: +20 482238232. E-mail address: dr_zeinab_2006@yahoo.com (Z.A. Etman). Peer review under responsibility of Housing and Building National Research Center.

The concept of self-compacting concrete (SCC) was proposed in 1986 by Hajime Okamura [1], but the prototype was first developed in Japan in 1988 by Ozawa [2]. This new concrete was deliberately designed to be able to fill every corner of the form and encapsulate all reinforcements only under the influence of gravitational forces, without segregation or bleeding. These advantages make SCC, particularly useful wherever placing is difficult as in heavily reinforced concrete members or

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in complicated work forms. Through extensive research, it has been established that the addition of fibers to concrete considerably improves its structural properties such as compressive strength, static flexural strength, impact strength, tensile strength, ductility and toughness [3-10]. Felekoglu et al. [11] reported that using SCC with its improving production techniques is increasing every day in concrete production. Domone [12] carried out an analysis for 68 case studies addressing the applications of SCC. He calculated the mix proportions of SCC. 31.2% by volume of the mix were a coarse aggregate. The paste content was 34.8% by volume. The powder content was 500 kg/m3; water/powder ratio was 0.34 by weight, and the fine aggregate/mortar was 47.5% by volume. Uysal and Yilma [13] studied the effect of using different types of mineral admixtures on the fresh and hardened properties of self-compacting concrete. They mentioned that the use of marble powder was the most suitable with regard to the properties of fresh SCC. On the other hand, Khaleel et al. [14] reported that the coarse aggregate properties had a direct effect on achieving SCC. Maximum size, texture and type of coarse aggregate were the factor effects on the flowabilty of concrete. They found that the flow-ability of SCC decreases with the increase in the maximum size of coarse aggregate and using crushed aggregate with the same water to powder ratio and superplast-icizer dosage. However, mix design methods and testing procedures are still developing. Zhu and Bartos [15] studied that permeation properties, which include permeability, absorption, diffusivity, etc., have been widely used to quantify durability characteristics of SCC. The results indicated that SCC mixes had significantly lower permeability than the vibrated normal reference concretes of the same strength grades. Furthermore, SCC mixes containing no additional powder but using a viscosity agent were found to have considerably higher diffusivity than reference mixes, and other SCC mixes. However, it is necessary assuring that this enhancement on the mechanical properties is not accompanied by a detrimental effect on the durability properties. Conventional fiber reinforced concrete is a special type of concrete that has been strengthened by adding fibers to the wet concrete mix. Concrete is quite brittle and while high levels of compressive strength can be achieved; the tensile strength is relatively low, which makes it likely to crack under many conditions. Fiber reinforced concrete is less probable to crack than conventional concrete. In the early years of the 20th century, asbestos fibers were added to concrete. In 1960s, a variety of fibers, including polypropylene, glass, and steel fibers were used in concrete [16]. Fiber reinforced concrete is commonly used in pavements and floors. It can also be used in foundations, pillars, precast forms, and beams in combination with traditional steel reinforcements. Fibers are usually used in concrete to resist cracking due to plastic and drying shrinkage. Numerous researchers have studied the effects of fibers on plastic shrinkage cracking behavior as reported in ACI 544.5R-10. A general observation is that thin fibers are more impressive in reducing the width of plastic shrinkage cracks than thick fibers as reported in ACI 544.5R-10 [17]. Most thin-diameter micro fibers with a high specific fiber surface area are particularly effective in reducing plastic shrinkage cracking [18]. Moreover, the use of fibers helps in reducing the permeability of concrete and its tendency to bleed [14]. A number of studies have been conducted to investigate the relationship between fiber reinforced concrete (FRC) and water permeability [18,19]. Some types of fibers produce great-

er impact, abrasion and shatter resistance of concrete. The amount of fibers added to a concrete mix is measured as a percentage of the total volume of the composite (concrete and fibers) and termed the volume fraction (Vf) [19]. The effect of fibers on the mechanical properties of concrete such as com-pressive strength, splitting tensile strength and flexural strength was reported by Alonso, 2008, Sena-Cruz, 2004 [20] and many other researchers. Some studies on the impact resistance of fiber reinforced concrete showed that self-compacted reinforced composites under impact were capable of dissipating much higher energy compared with conventional fiber reinforced concrete with polymeric or steel fiber [21]. Bindiganavile and Banthia, 2002 observed that the measured impact response was highly dependent on the characteristics of the dropping weight of the impact machine used for testing. Results appear to be far less sensitive to the mass of the hammer than to the drop height [21-23]. When self-compacting concrete becomes so widely used that it is seen as the ''standard concrete'' rather than a ''special concrete'' it will be possible to have durable and reliable concrete structures that require very little maintenance work. The development of SCC was an important step toward efficiency at building sites, rationally producing prefabricated concrete elements, better working conditions and improved quality and appearance of concrete structures. By adding fibers to SCC it is possible to enhance the performance of concrete structures. Fiber self-compacting concrete combines the benefits of SCC in the fresh state and an enhanced performance of fiber reinforced concrete in the hardened state.

Experimental program

To achieve the aim of the research, a two-stage program was conducted. In the first stage, different mixes were prepared to specify the best mix which achieves the requirements of Technical Specification for SCC. In the second stage, six mixes were prepared to determine the optimum content of fibers used in the fresh state of SCC, which are based on the finding of the first stage. A total of 90 cubes 10 x 10 x 10-cm were tested to determine the compressive strength of the mixes at 7 and 28 days. Cylinders of 10 cm in diameter and 20 cm in length were studied to determine the splitting tensile strength of the mixes. To determine the flexural strength of mixes and impact strength; 10 x 10 x 50-cm prisms were used.

Materials

Well graded siliceous sand was used with a specific gravity of 2.60, absorption of 0.78%, and a fineness modulus of 2.61. A coarse aggregate of crushed dolomite with maximum nominal sizes of 10 mm and 14 mm was used, with a specific gravity of 2.64 and absorption of 0.76%. Locally produced Portland cement (CEMI: 42.5 N) conforming to the requirements of Egyptian Standard Specifications (2005/373) was used. Imported class (F) fly ash meeting the requirements of ASTM C618 [24] with a specific gravity of 2.1 was used. Fly ash was added by 10% of the cement content. The cement content was 400 kg/m3 and the water powder ratio (W/P) ranged from (0.35 to 0.4). Tap water was used for mixing the concrete. A high range water reducer (HRWR) with a trade name; Addi-crete BVF was used as superplasticizer meeting the requirements of ASTM C494 (types A and F) [25]. The admixture

Table 1 Concrete trail mix proportions of self-compacted concrete mixes (kg/m3).

Mix No. Cement Sand Dolomite Fly ash W/P % HRWR

M.N.S. 10 mm 1 400 972 864 40 0.35 2

2 972 862 2.5

3 972 860 3

4 968 859 3.25

5 967 858 3.5

M.N.S. 14 mm 6 925 755 2.5

7 923 754 3

8 921 753 3.5

9 920 752 0.4 2.5

Table 2 Rheological properties of trail self-compacted concrete mixes.

Test method Notes

Mix no Slump flow test J-ring test V-funnel test

D (mm) T (s) T50 cm (s) D (mm) Hi-H2 (MM) T50 cm (s) T (s) Velocity

M.N.S. 10 mm 1 450 25.69 1.5 450 25 - 37.58 1.73 Viscosity too high

2 470 37.58 2.0 450 26 - 26.87 2.42 Viscosity too high

3 550 26.87 8 500 23 5.2 25.69 2.53 Viscosity too high

4 565 16.78 6.5 540 17 3.36 22.35 2.91 Viscosity too high +

Segregation

5 780 (700 mm)* 12.25 13 (2-5 s)* 780 2 (0-10 mm)* 3 14 (6-12 s)* 4.64 Bleeding + segregation

M.N.S. 14 mm 6 670 6.8 2.86 650 7 9.27 12.25 5.31 Bleeding

7 720 5.98 2 700 5 7.68 6.8 9.56 Segregation

8 765 14 18.6 780 10 1.27 5.98 10.89 Viscosity too high

9 750 6.25 4.57 670 3.5 4.76 6.25 10.4 Very good SCC

D: final diameter of the concrete = [Dj + D2]/2, T 50cm: time for the concrete diameter to reach 50 cm (s), Hj-H2 the difference of the height of

the concrete just before and after the ring, T: flow-through time (s).

Requirements of technical specification of self-compacted concrete [27].

Fig. 1 J-ring test for passing ability of mix 9.

Fig. 2 Slump flow test for flowability of mix 9.

is a brown liquid having a density of 1.18 kg/L at room temperature. The amount of HRWR ranged from (2.0 to 3.5%) of the cement weight was used. The fibers used to improve the mechanical properties in mixes had a trade name fiber mesh 300-e3 produced by SI Concrete systems, USA. 20 mm length polypropylene fibers were used. According to the manufacture data sheet, the fibers have a specific gravity of 0.91 and comply with ASTM C1116 [26] Type III. Steel fibers also were used. The absolute volume method was used to design the required trial mixes.

Casting and testing procedures

Coarse aggregate, fine aggregate, and the cement were mixed for at least 1 min in the dry state before the water, and admixtures have been added. The mixing time after slurry (water, fly ash, and HRWR) was added for (3-4) minutes to ensure full mixing of the SCC. In case of fiber self-compacted concrete, the fibers were added to the dry components before the slurry.

? 80 -

te et 60 -

n 40 -

o 20 -

□ slump test

□ J-Ring test

123456789 Mix No.

Fig. 3 Relationship between flow diameter of SCC and other mixes using different rheological tests.

25 20- 15

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Mix No.

Fig. 4 Relationship between flow time of SCC mix and other mixes using different rheological tests.

S 20 -

№ 10 -

-♦— M.N.S 10 mm

M.N.S 14 mm

2 3 4 5 Mix No.

Fig. 6 Relationship between Flow Time of SCC Mix and other Mixes Using V-Funnel Test.

12 ^ 10

-♦- M.N.S. 10 mm M.N.S 14 mm

0123456789 Mix No.

Fig. 7 Relationship between velocity of SCC mix and other mixes using V-funnel tests.

Test results

First stage

S 2" <s 1.5 H

01234567 Mix No.

Fig. 5 Relationship between (H1-H2) of SCC mix and other mixes using J-ring test.

The properties of fresh SCC were determined by different methods, which included the normal slump test, V-funnel test and J-ring test as illustrated in Table 2. The concrete specimens were cast and kept at the steel molds for 24 h. After 24 h, the specimens were removed from the molds and submerged in clean water at 20 0C until taken out for testing. Compressive strength testing machine with 2000 KN capacity was used in the determination of the compressive strength and splitting tensile strength. Flexural strength testing machine with 100 KN capacities was used in the determination of the flex-ural strength of the prism. The flexural strength was determined by the four points loading that having the same dimensions' concrete impact test beam specimens.

In this stage, nine mixes were prepared to specify the best mix which achieves the requirements of Technical Specification for SCC [27]. Coarse aggregate (dolomite) with a maximum nominal size of 10 mm and 14 mm was used to achieve the requirements as illustrated in Table 1. The properties of fresh SCC were determined by different methods as illustrated in Table 2.

Workability for self-compacted concrete mixes

Table 2 illustrates a summary of the fresh self-compacting concrete properties. Figs. 1 and 2 show the properties for the fresh self-compacted concrete mixes. It is clear from Figs. 3-7, the basic requirements of flowability as specified by technical specification for self-compacted concrete are satisfied for mix 9. For slump test, the flow diameter and the flow time at 50 cm were (75 cm) and (4.57 s), respectively. For V-funnel test the flow time was (6.25 s). These results indicate that the requirements for self-compacted concrete were achieved. The workability values are maintained by adding suitable quantities of materials and super-plasticizers.

Second stage

Based on results of first stage, mix (9) achieved the requirement of SCC. So, the second stage of the experimental program was conducted to add the fibers to SCC mix. Six mixes were prepared at this stage, after achieving the requirement of technical specification for SCC mixes in the first part as illustrated in mix (9). Different percentages of fiber (steel and polypropylene

Table 3 Concrete mix proportions (kg/m3).

Mix No. Cement Sand Dolomite Fly ash W/P % BVF % Fiber

Steel fibers Polypropylene fibers

M.N.S. 14 mm 9 400 920 752 40 0.4 2.5 - -

SSCC1 (10) 920 752 2.5 0.5 -

SSCC2 (11) 920 752 2.5 0.75 -

SSCC3 (12) 920 752 2.5 1.0 -

PSCC1 (13) 920 752 2.5 - 0.5

PSCC2 (14) 920 752 2.5 - 1.0

PSCC3 (15) 920 752 2.5 - 1.5

fiber) were added to the fresh self-compacted concrete. The percentages of steel fiber used were (0.5%, 0.75% and 1.0%) of the cement content. The percentages of polypropylene fiber used were (0.5%, 1.0%, and 1.5%) of the cement content. The optimum content of fiber was investigated. Tables 3 and 4 illustrated the concrete mix proportions and the rheological properties of fiber self- compacted concrete mixes.

Workability for fiber self-compacted concrete mixes

Table 4 illustrates a summary of the fresh fiber self-compacting concrete properties. It is clear from Figs. 8-14, the basic requirements of flowability as specified by technical specification for self-compacted concrete are satisfied for SSCC2 and PSCC2 compared with the control mix (mixes 9). The flow diameter was (70 and 72 cm) SSCC2 and PSCC2, respectively. The flow time at 50 cm was (4.89 and 5.0 s) for SSCC2 and PSCC2, respectively. For V-funnel test the flow time was (11.2 and 7.05 s) for SSCC2 and PSCC2, respectively. These results indicate that the requirements for SCC were achieved.

9 SSCC1(10) SSCC2 (11) SSCC3 (12) PSCC1(13) PSCC2 (14) PSCC3 (15) Mix No.

Fig. 8 Relationship between Flow Diameter and other Mixes of Fiber Self-Compacted Concrete.

~ 2.5 -S

Ä 2 -S3

1.5 -10.5 -0

0.75 1

% Fibers

Fig. 10 Relationship between (H1-H2) of Fiber Self-Compacted Concrete Mix and Percentage of Used Fiber.

—*— Steel Fibers Polypropylene fiber

^ V. J

0 0.25 0.5 0.75 1 % Fibers

1.25 1.5

Fig. 11 Relationship between flow time of fiber self-compacted concrete mix and percentage of used fibers.

It is noticed that the technical specification for SCC do not cover the properties of fiber self-compacted concrete.

Test set-up for impact Load

9 SSCC1(10) SSCC2 (11) SSCC3 (12) PSCC1(13) PSCC2 (14) PSCC3 (15) Mix No.

Fig. 9 Relationship between flow time and other mixes of fiber self-compacted concrete.

Test set-up was prepared to get the impact strength of self-compacted concrete and fiber self-compacting concrete at 28 days. A 2 kg iron ball was used to make an impact load on the tested specimens from a 1.2 m distance. The striking head of the drop iron ball had a hemispherical tip with a radius of 5 cm; Fig. 13 shows the test set-up. The specimen has been placed in impact testing installation, and it has been fixed using G-clamps. The specimen was supported over a span of 45 cm with specially designed devices, allowing it to freely rotate while preventing it from moving out of displacement. The span of the concrete beams tested was accurately adjusted for specimen of size 10 x 10 x 50 cm. The falling ball was adjusted to dropping on the middle point of the tested specimens. The

30 25 20 15 10 5

0.5 0.75 % Fibers

1.25 1.5

Fig. 12 Relationship between velocity of fiber self-compacted concrete mix and percentage of used fibers.

Iron ball (2 kg)

Fig. 13 Test set-up for impact testing installation.

blows were repeated until the 1st crack appeared. The crack propagation after each blow was marked on the specimen. The experiment was continued until the spalling occurs on the compression face of the specimen. The number of blows required for spalling for the full width on the compression face was noted, and the crack pattern was marked on the specimen. A comparison between the properties of fresh self-compacted concrete and fiber self-compacted concrete was illustrated in Figs. 14-18.

Effect of fiber on bleeding

Based on the experimental study, it can be concluded that the addition of fibers in concrete mixes gives a reduction in bleeding. The homogeneity of the mixes improved by the reduction in bleeding was noticed. The properties of fresh fiber SCC are illustrated in Table 4. Clearly, the SCC mix containing 0.75% steel fiber by cement weight was the best mix (SSCC2) as

■S 20 ta

SSCC2 Mix No.

Ï4 _o

Mix No.

Fig. 15 Relationship between flow time and other mixes.

1 -0.8 -0.6 -0.4 -0.2 -0-

SSCC2 Mix No.

Fig. 16 Relationship between (H1-H2) and other mixes using J-ring test.

12 10 -

8 -6 -4 2 -0 -

SCC SSCC2 PSCC2

Mix No.

Fig. 17 Relationship between flow time and other mixes using V-funnel test.

12 10 -

m 8-c 64"

SCC SSCC2 PSCC2

Mix No.

Fig. 14 Relationship between flow diameter and other mixes.

Fig. 18 Relationship between Velocity and other Mixes Using V-funnel Test.

illustrated in Figs. 8-12. The optimum value for polypropylene in the self-compacted concrete was 1% by cement weight for the mix (PSCC2) as illustrated in Figs. 8-12.

Mechanical properties of fiber self-compacted concrete mixes

Self-compacted concrete mixes containing steel or polypropylene fibers were prepared using 14-mm crushed dolomite as coarse aggregates. Different percentages of fibers were used. Fig. 19 shows the compressive strength for the fibers SCC mixes under investigated. The compressive strength ranged between 30.3 and 42.3 Mpa at 28 days. An increase was observed, which ranged between 33% and 40% for steel fiber SCC mixes compared with plain self-compacting concrete. Increase in compressive strength for polypropylene fiber SCC mix, ranged between 12% and 15% compared with the SCC mix observed. Increase in the compressive strength for the mixes with polypropylene fibers is compared to that with steel fiber. It is worth mentioning that compressive strength of polypropylene fiber SCC mixes was greater by about 17% in comparison with the steel fiber SCC mixes. Fig. 20 shows the fracture modulus (the fracture modulus fr values reported in Table 5.) divided by the square root of the compressive strength fcy and a plot of the ACI-318 code equation for predicting the fracture modulus (SI units):

fr = 0.622yf

Fig. 19 shows that the fracture modulus was safely predicted using Eq. (1). It can also be seen that the fracture modulus tended to increase in both polypropylene and steel fiber self-compacted mixes having lower compressive strength.

Impact resistance

The response of a structural element to impact depends on the interaction between the impacting body and the structure. Nemours factors described impact strength, which relative

4540 -35— 30-

JM 25-~ 201510 -50-

□ 7 days ■ 28 days

SCC SSCC1 SSCC2 SSCC3 PSCC1 PSCC2 PSCC3

Mix No.

Fig. 19 Compressive strength for different mixes.

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A 7 days □ 28 days -ACI

24 27 30 33 36 39 42 compressive strength (Fcy, Mpa)

Fig. 20 Relation between fracture modules and compressive strength.

Ctf •5

O o O o o o o o

>, >,

o SCC O o SCC o

> > > >

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o o o o o o o

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o o O o

(N m <N m

O o O C C C

C C C C C C

S S S S S S

S S S Û- Û- &

S m S s

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Table 5 Compressive strength and flexural strength of self-compacting concrete and fiber self-compacting concrete.

Mix no Compressive strength (MPa) Flexural strength (fr) (MPa)

7 days 28 days 7 days 28 days

SCC (9) 24.0 30.3 3.13 4.07

SSCC1(10) 32.2 40.3 4.26 5.46

SSCC2 (11) 34.5 41.5 4.64 5.73

SSCC3 (12) 35.5 42.3 4.95 6.05

PSCC1(13) 27.5 34.7 3.62 4.77

PSCC2(14) 29.0 34.0 3.99 4.61

PSCC3 (15) 28.0 34.0 3.86 4.61

Fr: measured from the four points loading test on beam specimens.

10 8 6 4 2 0

Deflection

^ rA ¡9

■f ¿2

Fig. 21 Relationship between deflection and no of drops of SCC without any Fiber.

16l 14 12 10 8 6 4 2 0

SSCC2 Mix No.

Fig. 24 Relationship between mix no. and no. of drops.

12 1 10

2 8 ■o

Deflection

Fig. 22 Relationship between deflection and no of drops of SCC with 0.75% steel fiber.

SSCC2 Mix No.

Fig. 25 Relationship between mix no. and energy absorptions.

16 14 12 §■10 -e 8 6

r^ w w ac

ri w w <1 « d Ci Ci

Deflection

ÏS 0.5 -

number of drops

Fig. 23 Relationship between deflection and no. of drops of SCC with 1% polypropylene fiber.

Fig. 26 Relationship between numbers of drops and energy of impact load for different mixes.

masses, velocities, contact zone stiffness, frequency of loading, precision of impact, and the area of local energy absorbed [2830]. In this study; a drop-weight was used to apply the impact loading to the SCC and fiber SCC beams from a certain drop height. The comparative study of impact energy absorption capacities for each type of concrete was performed. The damage and failure forms were identified.

Impact strength of self-compacted concrete and fiber self-compacted concrete

The number of blows that causes complete failure was 9 blows at 28-day for the control SCC mix. While it ranged between 11 and 15 blows at 28 day for steel fiber and polypropylene fiber SCC mixes. Figs. 21-23 show the numbers of drops and the deflection at different stages of loading for the mixes under investigation. A comparison between the number of drops for SCC and fiber SCC was illustrated in Figs. 24 and 25. The percentage of increase in impact strength was 22.2% and 66.7% for steel fiber and polypropylene fiber SCC, respectively compared with SCC mix. Fig. 26 shows the energy absorption for SCC and fiber SCC.

Conclusions

Based on the test results the following conclusions could be drawn:

(1) The addition of either steel or polypropylene was noticed to enhance the fresh properties of self-compacted concrete by reducing the bleeding.

(2) The optimum content for polypropylene fiber was 1% by cement weight while, the optimum content for steel fiber was 0.75% by cement weight.

(3) Using the polypropylene fibers increased the 28 days compressive strength by 13% independent of the fiber content compared to the control self-compacted concrete mix without fiber addition.

(4) Using the steel fibers increased the 28 day compressive strength by 37% independent of the fiber content compared to the control self-compacted concrete mix without fiber addition.

(5) The impact resistance in terms of the number of drops needed to cause the fracture of test specimens was increased by 22% and 67% when polypropylene and steel fibers were used, respectively.

(6) While the control mix test specimens failed suddenly in flexure and impact, the counterpart specimens contain fibers failed in a ductile manner, and failure was accompanied by several cracks.

References

[1] H. Okamura, Self-Compacting High-Performance Concrete, Concrete International, 1997, pp. 50-54.

[2] K. Ozawa, Development of High Performance Concrete Based on the Durability Design of Concrete Structures, EASEC-2, vol. 1, 1989, pp. 445-450.

[3] Final report of RILEM TC 188-CSC, Casting of Self Compacting Concrete, Materials and Structures, 2006, 39(10), pp. 937-954.

[4] "Technical Report''Available from: <http://www.radmix.com/ files/Radmix_Technical_Manual.p> (accessed January 2011].

[5] M.A. Ahmadi, O. Alidoust, I. Sadrinejad, M. Nayeri, Development of mechanical properties of self compacting concrete contain rice husk ash, World Acad. Sci. Eng. Technol. 34 (2007) 168-171.

[6] M. Sahmaran, H.A. Christianto, I.O. Yaman, The effect of chemical admixtures and mineral additives on the properties of self compacting mortars, Cem. Concr. Compos. 28 (2006) 432440.

[7] J.M. Khatib, Performance of self compacting concrete containing fly ash, Construct. Build. Mater. 22 (1) (2007) 1-4.

[8] I. Coppola, T. Ccerulli, D. Salvioni, Sustainable Development and Durability of Self-Compacting Concretes ACI, May 2004; 221: 29-50.

[9] P. Kumar, Self-compacting concrete: methods of testing and design, J. Inst. Eng. (INDIA) 86 (2006) 145-150.

[10] Alonso M. C., Sanchez M., Rodriguez C. and Barragan B., Durability of SCC Reinforced with Polymeric Fibers: Interaction with Environment and Behaviour against High Temperatures. 11th International Inorganic-Bonded Fiber Composites Conference, Madrid-Spain; 5-7 November, 2008.

[11] B. Felekoglu, S. Turkel, B. Baradan, Effect of water/cement ratio on the fresh and hardened properties of self-compacting concrete, Build. Environ. 42 (2) (2007) 1795-1802.

[12] P. Domone, Self-compacting concrete: an analysis of 11 years of case studies, Cem. Concr. Compos. 28 (2) (2006) 197-208.

[13] M. Uysal, K. Yilmaz, Effect of mineral admixtures on properties of self-compacting concrete, Cem. Concr. Compos. 33 (7) (2011) 771-776.

[14] O.R. Khaleel, S.A. Al-Mishhadani, H. Abdual Razak, The effect of coarse aggregate on fresh and hardened properties of self-compacting concrete (SCC), Procedia Eng. 14 (2011) 805813.

[15] W. Zhu, P.J.M. Bartos, Permeation properties of self compacting concrete, Cem. Concr. Res. 33 (6) (2003) 921-926.

[16] "Fiber reinforced concrete'' Cement & Concrete Institute, Midrand, 2010.

[17] ACI 544.5R-10, Report on the Physical properties and Durability of Fiber-Reinforced Concrete.

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