Effects of Concrete Compressive Strength of Macro and Micro Polypropylene Fiber Admixtures and Vacuu

International Journal of Material and Mechanical Engineering (IJMME), Volume 5 2016 www.ijm‐me.org doi: 10.14355/ijmme.2016.05.001

Effects of Concrete Compressive Strength of Macro and Micro Polypropylene 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 Polypropylene fibers are manufactured as an alternative to steel fibers. When steel fibers are exposed to adverse environmental conditions, they can lose their properties by time. Therefore, the physical and mechanical properties of the concrete expected from them are weaken. Polypropylene fibers have superior properties compared with steel fibers in terms of chemical and physical properties. There are two types of polypropylene fibers as an admixture in concrete; macro and micro. This study investigated the effects of macro and micro fibers of polypropylene on compressive strengths of normal and vacuum applied concrete. Parameters of the study were as follows: fiber diameter, 3‐different fiber ratios, different fiber length, 3‐different concrete strength class (C16/20‐C25/30‐C35/37 according to EN) and two different application methods (normal and vacuum).

Compressive strength tests were performed at the end of 1, 3, 7 and 28 days. Consequently, all the parameters affected the compressive strengths and other properties of the macro and micro polypropylene fiber‐reinforced concretes.

Keywords Concrete, Compressive Strength, Micro and Macro Polypropylene Fiber

Introduction The polymer fiber which gives the best results after its addition to concrete is polypropylene fiber. Polypropylene fibers are adapted version to modern technology of the use of natural micro equipment, straw and animal hair, which is as old as humanity [1]. Polypropylene fibers are widely used in concrete, plaster, mortar, and shotcrete applications. The addition of fibers to concrete considerably improve its structural characteristics such as static flexural strength, impact strength, tensile strength, ductility and flexural toughness [2, 3].

Polypropylene fibers are made up of 100% polypropylene, and they do not require additional labor, being easy to apply, improving the quality of concrete and plaster and not decay. A polypropylene fiber forms a three‐ dimensional micro network of reinforcement in concrete, improving some of the mechanical properties of concrete.

These fibers intended to improve the mixture to be the lightest micro‐reinforcement system, compared with alternative reinforcement systems, such as iron mesh, metal fiber and poultry net. Its weight per square meter is in the range of 90 g to 200 g. Therefore, it doesnʹt bring dead reinforcement weight to the structure, as in the case of other reinforcement systems [1]. Polypropylene fibers are produced from 100% homo‐polypropylene, in two types, including F and M type. F‐fibrillated fibers represent M‐multifilament fibers. M‐type fibers are very fine and can provide good results for indoor screeds, as they are not visible on screed surface. F‐type fibers are better suited for durable and tough concrete in industrial floor applications and heavy‐duty floors. Polypropylene fiber types and specifications are shown in Table 1. According to ASTM C1116 / C1116M‐10 standard, presence of 0.1% = 1 liter by volume in the fibers produced using 100% pure raw material is sufficient for 1 m³ of concrete [4].

Density of polypropylene fiber raw material is 0.9 kg/lt so the recommended amount of fiber should be at least 0.9 kg/l. These rates range between 0.05% and 2% and even go up to 5% [5]. Polypropylene fibers do not absorb water,

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therefore they do not affect water/cement ratio of concrete and mortars so they do not require a new mixture design or a change in mixing ratio. After polypropylene bundles are mixed at high speed for five minutes, they will be dissolved and thousands of fibers will be distributed uniformly throughout the concrete. Therefore itʹs easy and economical to place polypropylene fiber‐reinforced concrete [6, 7, 8].

Fibers with a variety of diameters and lengths depending on the application have caused improvement on characteristics of concrete [9]. Polypropylene fiber reduces plastic shrinkage cracks in early periods of concrete.

Polypropylene does not undergo a chemical reaction. Synthetics are resistant against alkalis and chemical wear, and impervious toward water so polypropylene became a synthetic material that can be used in Portland cement [10].

It was identified that strength values of field concrete samples, in the case of which polypropylene fiber‐reinforced concrete with fine aggregate are placed in a substitution reaction with thermal power plant boiler bottom ash and granulated blast furnace slag, do not change but a substition of 20 to 30% was reported to have positive effects on field concrete samples [11]. It was reported that high values of compressive strength and tensile splitting strength were obtained for concrete samples with hyperplasticiser additives and better bending strength values were obtained for polypropylene‐fiber reinforced concrete samples with hyperplasticiser additives [12]. In a study inverstigating the effects of the use of fly ash and polypropylene fiber on the properties of roller compacted concrete, it was established that water contents of the mixtures increased with the addition of fly ash and polypropylene fiber, unit weight values decreased, fly ash of 40% and 60% negatively affected mechanic strength, the fibers had no effect on mechanic strength and impact effect but affected breaking behavior [13].

Murathan et al.ʹs work, which aimed to use plastics assessed as hazardous waste in construction materials, revealed results on how propylene textile waste fibers affect mechanical strength, water absorption and shrinkage of composites, reported that other samples of various sizes containing polypropylene fibers broke in a ductile manner in a controlled way over a long time and hence fibers may enable composites acquire an elastic structure.

In the same study, positive results obtained from water absorption and shinkage experiments suggested that cracks which may emerge especially in hot and humid weather can be corrected and produced composites may be used in areas with a large surface area. In addition, direct effects of such waste on human and environmental health were reduced, contributing to sustainable development [14].

Vacuum concrete is the effective technique used to overcome this contradiction of opposite requirements of workability and high strength. With this technique both these are possible at the same time. In this technique, the excess water after placement and compaction of concrete is sucked out with the help of vacuum pumps (Figure 1).

This technique is effectively used in industrial floors, parking lots and deck slabs of bridges etc. The magnitude of applied vacuum is usually about 0.08 MPa and the water content is reduced by upto 20‐25%. The reduction is effective upto a depth of about 100 to 150 mm only [15‐18].

FIGURE 1. VACUUMED CONCRETE

The aim of this study was to identify concrete compressive effects in normal and vacuumed concretes of various

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strength classes by adding macro and micro polytablepropylene fibers with various lengths in a variety of ratios.

Materials and Method Materials 1)

Fibers

In this study, long and short macro and micro polypropylene (PP‐PPE) fibers were used (Figure 2). The properties of fibers are given in Table 1. The quantities of fibers were established according to TS 10514 Steel Fiber standard, which stipulates that the maximum amount per metercube of concrete should be 50 kg [19].

There isnʹt any standard related to synthetic fibers so PP and PPE volumes corresponding to 15‐30‐45 kg/m3 (A‐ B‐C) were specified in the study by taking account of the maximum fiber ratio established by TS 10514.

TABLE 1. FIBER ADMIXTURES PROPERTIES IN CONCRETE

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)

Macro Polipropilen 1.91‐3.81‐5.72 25‐50 0.5 0.25 ‐ 0.91 600‐750 3800 10 537 180

Micro Polipropilen 1.91‐3.81‐5.72 25‐50 ‐ ‐ 0.018 0.91 600‐700 3000‐3500 < 80 590 150

0.01

0.01

FIGURE 2. FIBER ADMIXTURES

2)

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 PP and PPE fibers in 3 different volumes (A‐B‐C) (Table 1) were added to the concretes.

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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 as in Table 2 by considering TS 802 [20] and TS 10514 standards. Granulometry distibutions of the agreegates used in the concretes are shown in Figure 3. CEM II/A‐M (P‐LL) 42,5 R type cement was used.

TABLE 2. CONCRETE MIX DESIGN

Concrete types ( 1000 dm3)

Concrete components

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 3. 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 TSEN 12390‐3 [21] 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 (Figure 4). 3 samples per day were used for the tests. In the results, evaluations were made using average values.

FIGURE 4. OBTAINED OF CONCRETE SAMPLES

Results and Discussion

FIGURE 5. THE COMPRESSIVE STRENGTH OF LOW STRENGTH PP FIBER REINFORCED CONCRETE

Compressive strength results of micro and macro polypropylene fiber‐reinforced concrete samples were obtained for low, normal and high strength concrete class groups. In each group, compression values of normal and vacuumed reference concrete samples 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 macro polypropylene fiber‐reinforced concrete samples are given in Figures 5, 6 and 7 compressive strengths of low‐normal‐high strength micro polypropylene fiber‐reinforced concrete samples are given in Figures 8, 9 and 10.

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In view of compressive strengths of low strength polypropylene fiber‐reinforced concrete samples, itʹs clear that nonfiber normal and vacuumed concrete samples and short fiber‐reinforced vacuumed concrete samples acquired about 50% of their total strengths in the first 3 days. In the case of short and long and long fiber‐reinforced concrete samples, a strength in the range from 28 to 41% was acquired in the first 3 days. At the end of 28 days, short and long fibers provided an increase in strength varying between 9 and 15% for normal concrete samples. Vacuum application provided an increase of up to 39%, which was the highest, for long and short fiber‐reinforced concrete samples with B ratio. Among all fiber‐reinforced concrete samples, B ratio showed the highest strength and C ratio showed the lowest strength. Particularly long fiber‐reinforced concrete samples with C ratio were found to have much lower strength, compared to the concrete samples with A or B ratio. This suggests that using excess amounts of long polypropylene fibers in low strength concrete negatively affects compressive strength.

FIGURE 6. THE COMPRESSIVE STRENGTH OF NORMAL STRENGTH PP FIBER REINFORCED CONCRETE

FIGURE 7. THE COMPRESSIVE STRENGTH OF HIGH STRENGTH PP FIBER REINFORCED CONCRETE

When compressive strengths of normal strength polypropylene fiber‐reinforced concrete samples are considered, they were found to have acquired 43 to 57% of their total compressive strengths in the first 3 days. At the end of 28 days, short fibers caused a decline of 3 to 6% in strength for normal concrete samples. Vacuum application caused the highest increase for long and short fiber‐reinforced concrete samples with B ratio (i.e. 23 and 27%, respectively).

Particularly fiber‐reinforced concrete samples with C ratio were found to have much lower strength than the concrete samples with A and B ratio. This suggests that using excess amounts of long polypropylene fibers in normal strength concrete causes a negative effect on compressive strength.

In view of compressive strengths of high strength polypropylene fiber‐reinforced concrete samples, itʹs clear that they acquired about 43 to 57% of their total compressive strength in the first 3 days. At the end of 28 days, B ratio

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resulted in an increase of ~11% in strength, whereas A and C ratios caused a decrease of 1 to 3% in strength for short fiber‐reinforced normal concrete samples. The highest increase provided by vacuum application was for long and short fiber‐reinforced concrete samples with B ratio (i.e. 22 and 19%, respectively). The strength of fiber‐ reinforced concrete samples with C ratio was much lower than the strength of concrete samples with ratio A and B, implying that using excess amounts of long polypropylene fibers in normal strength concrete negative affects compressive strength. In addition, there was no significant difference in compressive strength between nonfiber vacuumed concrete samples and fiber‐reinforced vacuumed concrete samples.

FIGURE 8. THE COMPRESSIVE STRENGTH OF LOW STRENGTH PPE FIBER REINFORCED CONCRETE

FIGURE 9. THE COMPRESSIVE STRENGTH OF NORMAL STRENGTH PPE FIBER REINFORCED CONCRETE

When compressive strengths of low strength polypropylene fiber‐reinforced concrete samples are considered, long and short fiber‐reinforced normal concrete samples acquired strength in the range from about 20 to 35% of their total strength, while vacuumed concrete samples acquired strength of 45 to 65% in the first 3 days. At the end of 28 days, A ratio resulted in an increase of ~4%, while B and C ratios resulted in a decrease of 3 to 14% for short and long fiber‐reinforced normal concrete samples. Vacuum application provided increases of 20% and 32% in the case of short and long fiber‐reinforced concrete samples, respectively, and strength decreased with increasing fiber ratio. In the case of polypropylene fiber‐reinforced concrete, compressive strength of low strength concrete decreases with increasing fiber ratio. This may be attributed to micro size of the fibers, higher number of micro fibers compared to macro fibers and accordingly, nonhomogeneous distributions inside concrete.

When compressive strengths of normal strength polypropylene fiber‐reinforced concrete samples are considered, short and long fiber‐reinforced normal concrete samples acquired about 27 to 48% of their total compressive

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strenghts, while vaccumed concrete samples acquired strength in the range from 39 to 61% in the first 3 days. At the end of 28 days, in the case of short and long fiber‐reinforced normal concrete samples, A ratio resulted in a decrease of ~1% and ~2% in strength, while B and C ratios resulted in a decrease in the range from 6 to 19%.

Vacuum application provided the highest increase in strength for long and short fiber‐reinforced concrete samples (i.e. 9% and 16%, respectively). The effects of polypropylene fibers on normal strength concrete samples and low strength concrete samples were similar.

FIGURE 10. THE COMPRESSIVE STRENGTH OF HIGH STRENGTH PPE FIBER REINFORCED CONCRETE

In view of compressive strengths of high strength polypropylene fiber‐reinforced concrete samples, short and long fiber‐reinforced normal concrete samples acquired about 20 to 42% of their total compressive strenghts, while vaccumed concrete samples acquired strength in the range from 39 to 51% in the first 3 days. At the end of 28 days, in the case of short fiber‐reinforced normal concrete samples, a decrease of 5 to 19% in strength occured with increasing fiber ratio, while in the case of long fiber‐reinforced normal concrete samples, a decrease of 6 to 16% in strength occured with increasing fiber ratio. Vacuum application provided the highest increase in strength for long and short fiber‐reinforced concrete samples (i.e. 11% and 16%, respectively). The effects of polypropylene fibers on low, normal and high strength concrete samples were similar.

Conclusions It was observed that all factors such as using long and short, micro and macro polypropylene fibers in various ratios, vacuum application and concrete strength class have an influence on compressive strength of concrete.

Accordingly;

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

Although equal ratios of macro and micro polypropylene fibers were used, significant differences were observed in compressive strengths of concrete samples due to a 40‐fold difference between diameters of these fibers. Microfibers, particularly long microfibers are more prone to flake compared to microfibers.

Therefore, microfibers fail to dissolve homogeneously inside concrete, resulting in reduced strength.



In microfiber‐reinforced concrete, strength decreases with increasing fiber ratio. In the case of macrofiber‐ reinforced concrete samples, the highest strength was observed in concrete samples with B ratio, while the lowest strength was observed in concrete samples with C ratio. This suggets that using excess amounts of macrofiber decreases concrete strength.



Vacuum application increases 28‐day compressive strength of concrete up to 25%. The highest increase in strength was observed in macro PP fiber‐reinforced concrete samples with B ratio and micro PP fiber‐ reinforced concrete samples with A ratio.



In comparison to reference concrete, there was almost no increase in strength in micro PP fiber‐reinforced concrete samples. On the contrary, a linear decrease in strength of 0 to 18% occurred with increasing fiber ratio.

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

The size of fibers was found to be influential on compressive strength of concrete. In all strength classes, long fiber‐reinforced normal or vacuumed concrete samples showed a higher compressive strength in the range from 4 to 9%, compared to short fiber‐reinforced normal or vacuumed concrete samples. Long fibers provide higher strength to concrete, compared to short fibers.



High strength macro PP‐fiber reinforced concrete samples and micro PP‐fiber reinforced concrete samples showed very similar strengths. Compressive strengths of micro PP‐fiber reinforced concrete samples with A ratio or C ratio were found to be lower by ~8‐19%, compared to macro PP‐fiber reinforced concrete samples.

Increased ratio of micro PP‐fibers in concrete result in lower compressive strength, compared to macro PP‐ fibers.

ACKNOWLEGEMENT

This study was 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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[12] Aktürk, Mehmet, “The investigation of performance charecteristics polypropylene fiber reinforced sel compacting concretes”, MS Thesis, Selcuk University Institute of Science and Technology, (2007), Page: 150 [13] Üte, Arif, Atacan, “Effects of fly‐ash and polypropylen fibers on the properties of roller compacted concrete”, MS Thesis, Ege University Institute of Science and Technology, (2008), Page: 193 [14] Murathan, Ayşe et al., “Useability Of High Density Polypropylene Textile Waste In Composite Material Production”, Journal of the Faculty of Engineering and Architecture of Gazi University, (2014), 29 (1), 9‐14.

[15] 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.

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[16] 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.

[17] Saeed, Haitham, H and Ezzulddin, Anas, A., “Study a new technique for producing Vacuum‐dewatered concrete”, International Journal of Enhanced Research in Science Technology & Engineering, (2014), 3(10), 1‐6.

[18] Bolat, Hakan et al., “An Application Of Area Concrete: Vacuumed Concrete”, Concrete 2008 ‐ International Ready Mixed Concrete Congress, İstanbul Turkey, 2008, 259‐268.

[19] TS 10514, “Concrete ‐ Steel Fibre Reinforced ‐ Rules for Mixing Concrete and Control, Turkish Standard Institute, (2015), Page: 1‐7.

[20] TS 802, “Design concrete mixes”, Turkish Standards Institute, Ankara, (2009), 1–18.

[21] TS EN 12390‐3, “Testing hardened concrete‐Part 3:Compressive strength of test specimens”, Turkish Standards Institute, Ankara, (2010), Page: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 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.

Black

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Çullu, M., Bolat, H., Vural, A., Tuncer, E., Investigation of Puzzolanic Activity of Volcanic Rocks From Northeast Of Sea, Science and Engineering of Composite Materials.

(DOI: 10.1515/secm‐2014‐0092).