International Journal of Material and Mechanical Engineering (IJMME), Volume 5 2016 www.ijm‐me.org doi: 10.14355/ijmme.2016.05.002
Effects of Concrete Compressive Strength of Steel and Polyester Fiber Admixtures and Vacuumed Dewatering Application Hakan Bolat1, Mustafa Çullu2 Gumushane University Natural Science and Engineering Faculty, Department of Civil Engineering 29100 Gumushane, Turkey, 1‐2
1hbolat@gmail.com; 2mustafacullu@hotmail.com Abstract Vacuum dewatering method is the process of removing some of mixing water from fresh concrete. Therefore, excess mix water damages are prevented and mechanical strengths increase after concrete takes the shape of the mold. Fiber admixtures are mostly used for increasing the flexural strength of concrete. However, there are also effects on the compressive strength. In this study, the effects of application of the vacuum dewatering on the compressive strength of concrete are examined with addition of steel and polyester fibers. The parameters of the study are fiber types (steel, polyester), fiber ratios (3 different ratios), fiber lengths (long, short) for concrete class (C16/20‐C25/30‐C35/45 according to EN) and two different application methods (normal, vacuum). The compressive strengths of the concrete prepared in accordance with these parameters are determined after 1, 3, 7 and 28 days. Thus, it is investigated that each of the parameters is affected concrete compressive strength. Keywords Concrete; Compressive Strength; Steel; Polyester Fibers
Introduction Fibers are generally used to increase flexural strength of concrete [1‐3]. However, physical and mechanicalcharacteristics of concrete are affected by type, length, geometric shape and ratio of the fiber [4‐5]. The most important mechanical characteristic of concrete is compressive strength [1‐3]. Itʹs been reported in the literature that fiber admixtures do not have a great influence on compressive strength of concrete, however, any change in fiber parameters also affects compressive strength of concrete [6,7]. If steel fibers with appropriate characteristics are added, they will make a significant contribution to the mechanical strength of concrete [4,6,8]. However if concrete is exposed to conditions such as adverse weather conditions, chemicals, freeze‐thaw, becoming wet or dry, steel fibers in concrete lose their characteristics depending on time [6,9,10] (Fig 1). Synthetic fibers are concrete admixtures developed as an laternative to steel fibers [9‐11]. Although breaking strength of synthetic fibers is not as high as that of steel fibers, their strength against other negative conditions is much higher and they show much more positive behaviors compared to steel fibers over time [8‐10]. One of the factors affecting mechanic behaviors of concrete is the mixing water. Parameters of the mixing water affecting concrete can be summarized as follows [1‐3,7]: • Using water the amount of which is either more or less than what is necessary • Using either too cold or hot water • Using water with unwanted physical and chemical properties • Using too much or too little water Reasons for such parameters occuring can be summarized as follows;
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• Inadequacy and negligence of workers during production, handling, loading and application processes • Using water which was exposed to either cold or hot weather condition • Using dirty, salty, argillaceous, acidic or basic water or water containing organic matter • Wet, dry, hot or cold aggregates, granulometry and cement factors
FIGURE 1. RUSTED STEEL FIBER
In concrete, part of mixing water is used for hydratation reaction and the remaining part for workability. After concrete takes the shape of mold, workability water causes several effects, including segregation, formation of drying shrinkage, which are likely to change according to the quantity of water [1‐3,10]. One of the practices improving mechanical properties of concrete by eliminating negative effects of workability water in fresh concrete is vacuumed concrete. In this application, some of the mixing water is removed from fresh concrete using a special cover laid on the surface of concrete immediately after the surface of fresh concrete is corrected and a vacuum pump (Fig 2). Hence the negative effects arising from segregation and presence of workability water are prevented [11‐14].
FIGURE 2. VACUUMED CONCRETE
The aim of this study was to identify concrete compressive effects in normal and vacuumed concretes of various strength classes by adding steel and polyester fibers with various lengths in a variety of ratios. Materials and Method Materials Fibers In this study, long and short steel and polyester fibers were used (Fig 3). The properties of fibers are given in Table
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1. TS 10514 [15] recommends that the maximum amount per metercube of steel fibers to be used in the concrete is 50 kg. There isnʹt any standard related to synthetic fibers, so 3 ratios including 15‐30‐45 kg/m3 (A‐B‐C) were specified in the study by taking account of the maximum fiber ratio established by steel fiber standard. Volume was established by considering the quantity, density and dimensions of steel fibers prepared on the basis of kg, and the quantity of polyester fiber was established in the same volume.
FİGURE 3. FİBER ADMİXTURES TABLE 1. FIBER ADMIXTURES PROPERTIES
Fiber properties Ratio (dm3 A‐B‐C) Length (mm) Width (mm) Thickness (mm) Diameter (mm) Density (g/cm3) Tensile Strength (MPa) Elastic modulus (MPa) Ultimate elongation (%) Fire point temperature (oC) Melting, oxidation and decomposition temp (oC) Water absorption according to ASTM D 570 (% ‐ by weight)
Polyester 1.91‐3.81‐5.72 25‐50 0.9 0.5 ‐ 1.36 400‐800 17237 > 8 537 253
Steel 1.91‐3.81‐5.72 30‐60 ‐ ‐ 0.9 7.87 ~1100 200000 < 2 ‐ 800
0.4
0
Concrete In the study, normal and vacuumed concretes of C16/20 (low‐L), C25/30 (normal‐N) and C35/45 (high‐H) strength classes were used. Long and short steel and polyester fibers in 3 different volumes (A‐B‐C) (Table 1) were added to the concretes. Fiber volume and the excess total concrete volume were balanced by deducting from sand volume. 79 types of concrete with the parameters including type of application, type of fiber, length of fiber, ratio of fiber and concrete strength class were prepared. Mixture ratios of the concretes by strength classes were specified in Table 2 by considering TS 802 [16] and TS 10514 standards. Granulometry of the agreegates used in the concretes are shown in Fig 4. CEM II/A‐M (P‐LL) 42,5 R type cement was used.
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TABLE 2. CONCRETE MIX DESIGN
Concrete components
Concrete types ( 1000 dm3) Low
Normal
High
Water Cement Air Fluidisation
301 94.3 14 ‐
260 115.7 14 4.4
280 153.3 14 5.8
Aggregates
590.7
608.7
546.9
Fly ash 0‐2 mm 0‐4 mm 2‐4 mm 4‐8 mm 4‐11.2 mm 8‐16 mm 11.2‐32 mm 16‐32 mm
56.7 ‐ 215 ‐ 106 ‐ 106 ‐ 107
58.5 ‐ 199 ‐ 120 ‐ 117 ‐ 117
52.5 120 ‐ 110 ‐ 140 124.4 ‐
Total
1000
1000
1000
FIGURE 4. AGGREGATE GRANULOMETRY
The concrete samples were coded in 2 different ways as reference concrete sample without fiber and concerete samples with fiber, as shown below. Nonfiber concretes: LR‐NR‐HR: Low‐Normal‐High strength reference concretes LVR‐NVR‐HVR: Low‐Normal‐High strength reference vacuumed concretes Fiber reinforced concretes (example):
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Method Destructive uniaxial compressive strength tests were conducted on the concrete samples in accordance with TSEN12390‐3 [17] standard on day 1, 3, 7 and 28. For this purpose, the concrete samples were obtained by cutting them in the form of 15 cm cubes from a concrete area with dimensions of 120x120x20 cm, rather than from a cube or cylinder mold (Fig 5). 3 samples per day were used for the tests. In the results, evaluations were made using average values.
FIGURE 5. OBTAINED OF CONCRETE SAMPLES
Results and Discussion Compressive strength results of the concrete samples were obtained for low, normal and high strength concrete class groups. In each group, compressive strength values of normal and vacuumed reference concrete samples (LR‐ NR‐HR and LVR‐NVR‐HVR) and long or short fiber‐reinforced normal and vacuumed concrete samples were shown. The compression value results on day 1, 3, 7 and 28 were shown cumulatively. Compressive strengths of low‐normal‐high strength steel reinforced concrete samples are given in Figures 6, 7 and 8 and compressive strengths of low‐normal‐high strength polyester reinforced concrete samples are given in Figures 9, 10 and 11.
FIGURE 6. THE COMPRESSIVE STRENGTH OF LOW STRENGTH STEEL FIBER REINFORCED CONCRETE
In view of compressive strengths of low strength steel reinforced concrete samples, itʹs clear that their total strength increased by 48‐60% in the first 3 days. At the end of 28 days, vacuum application increased compressive strength by 10‐50%, when the ratio decreased in the case of short fibers and the ratio increased in the case of long fibers.
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Although compression increased with respect to reference concrete in normal concrete samples with short fiber, vacuumed concrete samples with short fiber and normal concrete samples with long fiber, compressive strengths decreased with increasing fiber ratio. Vacuum application and increased fiber ratio caused increased compression only in the case of long fibers.
FIGURE 7. THE COMPRESSIVE STRENGTH OF NORMAL STRENGTH STEEL FIBER REINFORCED CONCRETE
When compressive strengths of normal strength steel reinforced concrete samples are considered, their total strengths increased by ~50% in the case of normal concrete samples and in the range of ~50 to 65% in the case of vacuumed concrete samples in the first 3 days. At the end of 28 days, in the case of short and long fiber‐reinforced concrete samples, fibers with A ratio and C ratio were found to have no effect on strength, while the fibers with B ratio resulted in an increase of ~10% compared to reference concrete samples without fiber. In the case of the vacuumed concrete samples with short and long fibers, fibers with A ratio and C ratio were found to have no effect on strength, while the fibers with B ratio resulted in an increase of about 10% compared to reference vacuumed concrete samples without fiber. Accordingly, it can be concluded that the fibers with A ratio had no effect on compressive strength, whereas the fibers with C ratio caused an increase which is more than necessary.
FIGURE 8. THE COMPRESSİVE STRENGTH OF HİGH STRENGTH STEEL FİBER REİNFORCED CONCRETE
In view of compressive strengths of high strength steel reinforced concrete samples, itʹs clear that they acquired about more than 50% of their total strength in the first 3 days. In the case of short, normal and long steel fiber‐ reinforced vacuumed concrete samples, this ratio was in the range of 60 to 85%, compared to nonfiber reference
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concrete samples. At the end of 28 days, in the case of fibers with B ratio, short and long steel fiber‐reinforced concrete samples showed an increase of up to 18%, compared to reference concrete, however, this ratio decreased in the case of fibers with A or C ratio. Vacuum application resulted in an increased strength of up to 25%, compared to nonfiber reference concrete samples.
FIGURE 9. THE COMPRESSIVE STRENGTH OF LOW STRENGTH POLYESTER FIBER REINFORCED CONCRETE
When compressive strengths of low strength polyester fiber‐reinforced concrete samples are considered, they acquired strength in the range of 31 to 45% of their total strength in the first 3 days. At the end of 28 days, short and long fibers increased strength by 6 to 20% in the case of normal concrete samples. Vacuum application provided increases in the range of 22 to 30% in the case of long and short fiber‐reinforced concrete samples. B ratio showed the highest strength, whereas C ratio showed the lowest strength in all fiber‐reinforced concrete samples.
FIGURE 10. THE COMPRESSIVE STRENGTH OF NORMAL STRENGTH POLYESTER FIBER REINFORCED CONCRETE
When compressive strengths of normal strength polyester fiber‐reinforced concrete samples are considered, they were seen to have acquired 50 to 62% of their total strength in the first 3 days. At the end of 28 days, strength increased by 7% in long and short fiber‐reinforced normal concrete samples with B ratio, whereas strength diminished in fiber‐reinforced concrete samples with C ratio. Vacuum application provided increases in the range of 15 to 36% in the case of long and short fiber‐ reinforced concrete samples. B ratio showed the highest strength, whereas C ratio showed the lowest strength in all fiber‐reinforced concrete samples.
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FIGURE 11. THE COMPRESSIVE STRENGTH OF HIGH STRENGTH POLYESTER FIBER REINFORCED CONCRETE
In view of compressive strengths of high strength polyester reinforced concrete samples, itʹs clear that normal concretes acquired 48 to 55% of their total strength and vacuumed concretes acquired 38 to 75% of their total strength in the first 3 days. At the end of 28 days, an increase of 9% was achieved for long and short fiber‐ reinforced normal concretes with B ratio. Vacuum application resulted in an increase of 8 to 19% for long and short fiber‐reinforced concretes. B ratio showed the highest strength in all fiber‐reinforced concrete samples. Conclusions It was observed that all factors such as using long or short steel or polyester fibers in various ratios, vacuum application and concrete strength class have an influence on compressive strength of concrete. Accordingly;
Vacuum application increased strength in all types of concrete, compared to reference concrete. It increased strength by up to 41, 26 and 24% for low, normal and high strength steel reinforced concretes and up to 41, 33 and 19% for low, normal and high strength polyester reinforced concrete samples, respectively. This suggests that the effect of vacuum decreases with increasing strength classification.
Compressive strength of fiber reinforced vacuumed concrete samples is higher than that of normal fiber‐ reinforced concrete samples. Compressive strength increased up to 21, 14 and 6% in low, normal and high strength short steel reinforced concrete samples and up to 14, 19 and 7% in low, normal and high strength long steel fiber‐reinforced concrete samples, respectively. Compressive strength increased up to 9, 17 and 7% in low, normal and high strength short polyester reinforced concrete samples and up to 44, 26 and 8% in low, normal and high strength long polyester fiber‐reinforced concrete samples, respectively. It can be concluded that type and length of fiber are effective on compressive strength. However, itʹs clear that as concrete strength class increases, the effects of these factors decrease as well as are similar.
In the case of both normal and vaccumed concrete samples, fibers with B ratio (moderate) provided the highest strength. Fibers with A ratio (few) are lower in quantity than those with normal ratio and had a very little effect on compressive strength. Fibers with C ratio (many) are higher in quantity than those with normal ratio so they caused a very little increase in strength, compared to reference concretes without fiber. Adding small amounts of fiber into concrete samples resulted in almost no effect on strength, while adding excess amounts of fiber is likely to result in reduced composition and hence gradually reduced strength.
ACKNOWLEGEMENT
This study is supported by TUBITAK (The Scientific and Technological Research Council of Turkey). Project number: 212M012. And thank you for contribution to Dr. İlker Tekin, Hacı Mehmet Şahin, Mehmet Nergiz, Mehmet Turgut Kufacı and Murat Cingöz.
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REFERENCES
[1] Neville, Adam. M. “Properties of concrete. 5th edition.” Trans‐Atlantic Publications, (2011) 108–178. [2] Mehta, P.Kumar and Monteiro, J.M. Paulo, “Concrete: microstructure, properties and materials.” The McGraw‐Hill Companies, (2006), 33–187. [3] Erdogan, Y. Turhan. “Concrete. 3rd ed.’ Metu Advances Foundation Publications, (2010), 66–115. [4] Caggiano, Antonio et al., “Fracture behavior of concrete beams reinforced with mixed long/short steel fibers.” Constr Build Mater, (2012), 37, 832–840. [5] Soutsos, N. Marios et al., “Flexural performance of fibre reinforced concrete made with steel and synthetic fibres.” Constr Build Mater, (2012), 36, 704–10. [6] Bolat, Hakan et al., “The effects of macro synthetic fiber reinforcement use on physical and mechanical properties of concrete.” Composites Part B: Engineering, (2014), 61, 191–198. [7] Li, Zongjin. “Advanced concrete technology.” John Wiley & Sons, (2011). [8] Behnood, Ali et al. “Evaluation of the splitting tensile strength in plain and steel fiber‐reinforced concrete based on the compressive strength.” Construction and Building Materials. 98 (2015) 519–529. [9] Bolat, Hakan and Şimşek, Osman. “Evaluation of Energy Absorption of Macro Synthetıc and Steel Fiber Reinforced Concretes.” Romanian Journal of Materials. (2015), 45 (2), 123 – 132. [10] Aïtcin, Pierre‐Claude and Flatt, J. Robert. “Science and Technology of Concrete Admixtures ‐ 5 – Water and its role on concrete performance.” (2016), 75–86. [11] Hattori, Hiroki et al. “Experimental study on pore water pressure distribution in mortar and concrete during vacuum processing (Part.1 outline of experiment).” Proceedings of Annual Meeting of AIJ A‐1, Japanese, (2004) 245–246. [12] Hatanaka, Shigemitsu et al. “Study on mechanism of strength distribution in vacuum processed concrete based on the consolidation theory.” J Struct Constr Eng Archit Ins Jpn, Japanese, (2005) 596, 1–8. [13] Saeed, H. Haitham and Ezzulddin A. Anas. “Study a new technique for producing Vacuum‐dewatered concrete’, International Journal of Enhanced Research in Science Technology & Engineering, (2014), 3(10), 1‐6. [14] Bolat, Hakan et al. “An application of area concrete: vacuumed concrete.” Concrete 2008 ‐ International Ready Mixed Concrete Congress, İstanbul Turkey. (2008) 259‐268. [15] TS 10514. “Concrete‐Steel Fibre Reinforced‐Rules for Mixing Concrete and Control.” Turkish Standards Institute. (1992) 1– 23. [16] TS 802. “Design concrete mixes.” Turkish Standards Institute. (2009) 1–18. [17] TS EN 12390‐3. “Testing hardened concrete – Part 3: Compressive strength of test specimens.” Turkish Standards Institute, (2010) 1–19.
Hakan Bolat was born in 1977 in Ankara‐Turkey. Received his BA(1999), MA (2002) and PhD (2010) education in Gazi University Institute Of Natural Sciences Department of Construction Education in Ankara‐Turkey. His MA Thesis is about Vacuumed Concrete and PhD Thesis is about Energy Absorption of Different Fiber Reinforced slab concrete. He gave undergraduate and graduate lessons such as Construction Drawing, Material Science, Concrete Technolgy and Engineering Management in in Hacettepe and Gumushane. Currently he has been worked as an Assistant Professor at Gumushane University in Turkey since 2010. He continue to researches of about different fiber reinforced concrete energy absorption and durability, different fiber reinforced granul and fluid foam concrete and effects of water properties on concrete. major publications are as follows listed: 1. Bolat H., Şimşek O., Çullu M., Durmuş G., Can Ö. “The effects of macro synthetic fiber reinforcement use on physical and mechanical properties of concrete”, Composites Part B: Engineering, Vol. 61, p.191–198, May 2014 2. Bolat, H., Erkuş, P. ʺUse of Polyvınyl Chloroıde (PVC) Powder And Granules as Aggregate Replacement in Concrete Mıxturesʺ, Science and Engineering of Composite Materials. (DOI: 10.1515/secm‐2014‐0094) 3. Çullu, M., Bolat, H., Vural, A., Tuncer, E., Investigation of Puzzolanic Activity of Volcanic Rocks From Northeast Of Black
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Sea, Science and Engineering of Composite Materials. (DOI: 10.1515/secm‐2014‐0092) 4. Bolat H., Şimşek O. “Evaluation of Energy Absorption of Macro Synthetıc and Steel Fiber Reinforced Concretes” Romanian Journal of Materials 2015, 45 (2), 123 – 132. Mustafa ÇULLU was born in 1975 in Adana‐Turkey. Received his BA(2001), MA (2004) and PhD (2010) education in Gazi University Institute Of Natural Sciences Department of Construction Education in Ankara‐Turkey. His MA Thesis is about Alkali‐silica reactionand PhD Thesis is about antifreeze for concrete. He gave undergraduate and graduate lessons such as Construction Drawing, Material Science, Concrete Technolgy and construction managementin in Hacettepe University and Gumushane University. Currently he has been worked as an Assistant Professor at Gumushane University in Turkey since 2010. He continue to researches of about heavy aggregate and radiation shielding: 1. Arslan, M., Çullu, M., Durmuş, G., “The Effect Of Antifreeze Admixtures On Compressive Strength Of Concretes Subjected To Frost Action”, Gazi University Journal of Science, 24(2), 299‐307, 2011. 2. Çullu, M., Arslan, M., “The effects of antifreeze use on physical and mechanical properties of concrete produced in cold weather”, Composites: Part B, 50, 202–209, 2013. 3. Bolat H., Şimşek O., Çullu M., Durmuş G., Can Ö. “The effects of macro synthetic fiber reinforcement use on physical and mechanical properties of concrete”, Composites Part B: Engineering, Vol. 61, p.191–198, May 2014. 4. Çullu, M., Bolat, H., Vural, A., Tuncer, E., Investigation of Puzzolanic Activity of Volcanic Rocks From Northeast Of Black Sea, Science and Engineering of Composite Materials. (DOI: 10.1515/secm‐2014‐0092).
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