Composites: Part B 61 (2014) 191–198

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Composites: Part B

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The effects of macro synthetic fiber reinforcement use on physicaland mechanical properties of concrete

http://dx.doi.org/10.1016/j.compositesb.2014.01.0431359-8368/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +90 456 2337425/6/1141; fax: +90 456 233 7427.E-mail addresses: hbolat@gmail.com (H. Bolat), simsek@gazi.edu.tr (O. S�ims�ek),

mcullu@gumushane.edu.tr (M. Çullu), gdurmus@gazi.edu.tr (G. Durmus�),omercan@gazi.edu.tr (Ö. Can).

1 Tel.: +90 312 2126840/2022000; fax: +90 312 2213202.2 Tel.: +90 456 2337425/6/1133; fax: +90 456 233 7427.

Hakan Bolat a,⇑, Osman S�ims�ek b,1, Mustafa Çullu a,2, Gökhan Durmus� b,1, Ömer Can b,1

a Gumushane University, Engineering Faculty, Department of Civil Engineering, 29100 Gumushane, Turkeyb Gazi University, Technology Faculty, Department of Civil Engineering, Gazi Üniversitesi Rektörlügü, 06500 Teknikokullar, Ankara, Turkey

a r t i c l e i n f o

Article history:Received 29 July 2013Received in revised form 14 January 2014Accepted 21 January 2014Available online 29 January 2014

Keywords:A. FibersB. Physical propertiesD. Mechanical testingD. Non-destructive testing

a b s t r a c t

Attempts to find a construction material having increased strength, ductility, toughness, and durabilityhave led to interest in high performance fiber reinforced concrete. The use of such materials increasesday by day. When the fibers are distributed in a homogeneous way and used in appropriate quantityinside the concrete, they reduce cracks, contribute to tensile strength, toughness, ductility and durability,and improve other mechanical properties. In this study, four types of concrete were produced: steel fiber(SFRC), polyester fiber (PYFRC), polypropylene fiber (PPFRC) reinforced concrete and a reference samplemade of plain concrete (R1); these were then compared to one another. The ratio of fibers was used 4.25%of volume of concrete. The effects of the different types of fiber on hardened concrete were determined byconducting physical and mechanical experiments. Compressive strength, surface hardness, ultrasonicpulse velocity, carbonation, abrasion, capillarity and freeze–thaw resistance experiments were conductedon hardened concretes. SFRC had higher 12.4%, PYFRC 3.4% higher and PPFRC 4.3% lower compressivestrength with respect to R1. PPFRC showed 8.04% higher compressive strength than R1 when it was deter-mined by the surface hardness method. SFRC showed 5.4% higher compressive strength than R1 when weapplied the ultrasonic pulse velocity method. In the abrasion experiment, the highest abrasion was foundin SFRC with �0.5%, while the lowest was found in PPFRC at �0.18%. The highest and lowest amount ofcapillary water absorption was seen in R1 and PYFRC, respectively. In a carbonation experiment, SFRCwas determined �130.8% higher than R1. It was concluded that the types of fiber used for reinforcementinfluenced the physical and mechanical properties of the concrete.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction materials is becoming more popular. When the fibers are distrib-

The enhancement properties of concrete in fresh and hardenedstates, its durability and its environmental impacts are interestingtopics for research. One method for increasing some engineeringproperties of concrete is the use of fibers as an additional basicmaterial in the concrete mixture. The fiber can be made from nat-ural materials such as asbestos, sisal and cellulose, or of manufac-tured products such as glass, steel, carbon and polymer [1,2]. Fiber-reinforced concrete (FRC) is a structural material characterized bya significant residual tensile strength in the post-cracking regimeand an enhanced capacity to absorb strain energy due to fiberbridging mechanisms across the crack surfaces [3]. The use of such

uted in a homogeneous way and used in an appropriate quantityinside the concrete, they reduce cracks, contribute to tensilestrength, toughness, ductility and durability, and improve othermechanical properties [4]. It has been assumed that while under-going tensile deformations in the concrete, the fibers with differentmechanical and geometrical properties block the propagation andfurther development of cracking from the micro-to-macro scale[5].

Among the various types of fibers, steel fiber is the most com-monly used for most structural and non-structural purposes. Re-search has shown that fibers have a significant effect on concreteperformance; in particular, steel fibers increases flexural strength,some post-cracking or residual moment capacity and energyabsorption [2,4,6–8]. Additionally, a complete replacement of steelbar reinforcement with steel fibers could lead to further costreduction due to less manpower being required. Even if the mate-rial price of SFRC in high quantities is not necessarily competitiveagainst conventional reinforced concrete, the necessary working

192 H. Bolat et al. / Composites: Part B 61 (2014) 191–198

time for the placement of reinforcing bars could be partially omit-ted [9]. The reasons for greater use of steel fibers include manufac-turing facilities, economics, reinforcing effects and resistance tonegative environmental conditions [10]. This is followed by poly-propylene (PP), glass and other fibers; however, these are not com-monly used for structural concrete applications [11,12].

Among all the types of fibers, steel fiber is most commonly usedfor improving the mechanical properties of concrete, [10–12]. Add-ing steel fiber to concrete increases its density. This is because thistype of fiber has high specific gravity. The test results showed thata higher quantity of steel fiber usually yields heavier concrete. Onthe contrary, synthetic fiber produces lighter concrete [13–15].

The inclusion of fibers in concrete has a significant negative ef-fect on the concrete’s fresh properties [16,17]. The degree of reduc-ing workability depends on the type and amount of fibers used andbecause of its high specific gravity, it can increase the dead load ofa composite [16]. In addition, fiber reinforced concrete mixturesneed more mixing and placing time than non-fiber plain concrete[1,10,14].

Among the various types of fibers, the effect of steel and syn-thetic fibers has been researched with respect to the propertiesof concrete. In most cases, it was reported that although the steelfiber increases the compressive strength of concrete, the increasewas not significant and that the synthetic fibers had no significanteffect on the compressive strength of concrete [4,6,7].

However, the effects of corrosive environments on the steel fiberswere negative. Examples: Fig. 1a shows concrete pavement rebars in An-kara-Turkey (over a period of 18 years); Fig. 1b shows the steel fibersafter a year that were used in this study; Fig. 1c shows steel fibers usedin a study by Granju et al. over a period of one year. Macrosynthetic poly-ester and polypropylene fibers can therefore be shown as alternatives tosteel fibers for preventing the negative effects of corrosion, alkaline reac-tions, acidic water, salt, chlorine, chemicals and micro-organisms. Theyalso have water repellent properties and provide maximum adherenceowing to their wavy curl formation and both ends being hooked [10,18].

In this study, three types of reinforced concrete were produced:steel fiber reinforced concrete (SFRC), polyester fiber reinforced con-crete (PYFRC) and polypropylene fiber reinforced concrete (PPFRC);one type (R1) of made of plain concrete were produced. Compressivestrength of the concretes was determined by uniaxial, surface hard-ness determination, ultrasonic pulse velocity and component meth-ods. Furthermore, determination of depth of carbonation, capillarywater absorption abrasion resistance and freeze–thaw resistanceexperiments were conducted on the concretes. The study aimed todetermine the performances of macro synthetic fiber concretes withrespect to steel fiber and (R1) made of plain concrete.

2. Materials and methods

2.1. Materials

2.1.1. ConcreteFour types of concrete were produced in C30 strength class.

SFRC, PYFRC, PPFRC and R1 were produced in compliance with TS

Fig. 1. The expose to negative condition o

802 [19] and EN 10515 [20] standards. In the formation of con-cretes, CEM I 42.5R cement, Ankara municipal water, crushedaggregates, air entraining admixtures (AEA) complying with EN934-2 standard [21] and hardening retarding superplasticizers(SP) chemical additives were used. Mixture designs of concretesin 1 m3 volume are shown in Table 1. A water/cement ratio of0.45 was used.

2.1.2. FibersA volume of 4.25 dm3/m3 (0.425%) was used for each type of fi-

ber. The polyester (PY), polypropylene (PP) and steel (S) fibers usedare shown in Fig. 2 and their properties are shown in Table 2.

2.2. Method

Dry materials were mixed to form a homogeneous distributionof aggregates, cement and fibers in the production of concretes.Water with chemical additions, including 0.1% AEA and 1.5% SFof cement weight was added to the prepared dry mixture in a con-trolled manner. After approximately 10 min of mixing, fresh con-crete was poured into molds and squeezed by using an externalvibrator for 30 s. Duration of external vibration lasted longer be-cause of a thin aggregate ratio of 0–4 mm, which is higher thanin normal concrete. Production of fresh concretes was performedin compliance with TS 802, EN 10514 [22] and EN 10515 standards.Compressive strength, surface hardness, ultrasonic pulse velocity,carbonation, abrasion, capillarity and freeze–thaw resistanceexperiments were conducted on hardened concretes.

3. Results and discussion

3.1. Fresh concrete properties

Slump tests complying with ASTM C143 [23], air experimentscomplying with ASTM C138 and unit weight experiments comply-ing with ASTM C138 [24] were conducted after the concretes hadbeen prepared. Slump, the amount of air and unit weight weremeasured for each type of concrete six, three and six times, respec-tively, and averaged.

The average values of slump, amount of air and unit weight inconcretes are shown in Table 3. According to TS 802, the plannedslump was 12 cm. However, it was seen that R1 and PPFRC had8% and 2% higher slump, respectively; SFRC and PYFRC had 11%and 42% lower slump, respectively. The reasons for PYFRC to havea lower slump was possibly because polyester fibers, as shown inTable 1, have a water retention capability of 0.4% of their weight.

More air (32%) was found in SFRC, 21% more in PPFRC and 29%more in PYFRC with respect to R1. In the SFRC study of Aruntaset al. [25], it was found that as the ratio of SF in concrete increased,the amount of squeezed air also increased. It was determined thatthe fluidizer, fibers and external vibration duration increased theamount of squeezed air in fiber concretes.

The unit weights of all concretes were found to be �100 kgmore than calculated according to TS 802. The reason for this can

f steel fibers and rebars in concrete.

Table 1Mixture designs of concretes in 1 m3.

Concrete components SFRC–PYFRC–PPFRC (dm3) R1 (dm3)

Water 175 175Cement 126 126Pressed air (%0.1) + AEA (%3.5) 45 45Fibers 4.25 –0–0.25 mm aggregate 160 1600.25–4 mm aggregate 130 1304–11.2 mm aggregate 220.44 224.6911.2–22.4 mm aggregate 134 134SP (%1.5 – weigh of cement) 4.93 4.93AEA (%0.1 weigh of cement) 0.38 0.38

Total 1000 1000

Table 3Slump, air quantities and unit weight of concretes.

Tests N R1 PYFRC PPFRC SFRC

Slump (cm) 6 13 7 12.2 10.7Air quantities (%) 3 2.8 3.7 3.4 3.6Unit weight (kg/m3) 6 2417.2 2420.4 2402 2440.1

Table 4Determination of concrete quality by ultrasonic pulse velocity.

Pulse velocity (V) km/s >4.5 3.5–4.5

3.0–3.5 2.5–3.0

<2.0

Concrete quality Excellent Good Suspect Weak Very bad

H. Bolat et al. / Composites: Part B 61 (2014) 191–198 193

be that the aggregate granulometry of fiber concretes is differentthan the aggregate granulometry of normal concretes. It was seenthat fiber concretes showed differences less than 1% in unitweights with respect to R1. It is thought that SFRC has the highestunit weight because of steel fiber intensity.

3.2. Compressive strength

The compressive strengths of concretes cured in water at roomtemperature until the 28th day was determined using four differ-ent methods. These were: (1) the uniaxial destructive method(rUA); (2) an approximate compressive strength determinationmethod by finding surface hardness with a concrete hammer(rRN); (3) approximate compressive strength determination meth-od by pulse velocity (rV); (4) combined method (rRN+USPV).

The uniaxial destructive method was the first method used fordetermining compressive strength (rUA). Compressive strength(rUA) was calculated on five 100 � 200 mm cylindrical concretesamples according to EN 12390-3 principles [26].

Fig. 2. Polyester, polyprop

Table 2Fibers properties.

Fibers properties

Length (mm)Width (mm)Thickness (mm)Diameter (mm)Specific gravity (g/cm3)Tensile strength (MPa)Young’s modulus (MPa)The final elongation (%)Ignition temperatures (�C)Melting, oxidation and deterioration temperature (�C)According to ASTM D 570 Water absorption (% – weight basis)

The non-destructive testing method that used in the study wasapproximate compressive strength (rRN) determination by deter-mining surface hardness with a concrete test hammer. The surfacehardness rebound number was obtained by using an N-type con-crete hammer (Schmidt hammer) having 0.225 kg m impact en-ergy on concrete plates with dimensions of 600 � 600 � 100 mm.Surface hardness was measured in compliance with ASTM C805[27] standards with an angle of a = �90� when the concrete surfacewas dry. In approximate determination of compressive strengths ofconcretes, Fig. 3 [28] shows the concrete hammer compressivestrength that was used.

The second non-destructive method applied was pulse velocity.Application of this test is fast and easy. This test is accepted as afield test in fast comparisons. The experiment was calculatedaccording to ASTM C597 principles [29].

No unique relationship was found between pulse velocity andconcrete strength. Several relationships between pulse velocityand concrete compressive strength have been described by

ylene and steel fibers.

PY PP S

30 30 301 1 –0.6 0.35 –– – 0.91.36 0.95 7.87400–800 600–750 �110017237 3800 200000>8 10 <2537 537.78 –253 180 8000.4 0.01 0

Fig. 4. Compressive strength on 3rd, 7th, and 28th days provided by uniaxialdestructive method.

194 H. Bolat et al. / Composites: Part B 61 (2014) 191–198

researchers. One of them is the formula determined by Qasrawi[30]. Eq. (1) was used to calculate rUSPV [30].

rUSPV ¼ 36:72ðVÞ � 129:077 ð1Þ

where rUSPV is the concrete compressive strength, MPa and V is thepulse velocity, km/s.

According to Erdogan [28], concrete quality can also be deter-mined by detecting USPV through concrete. According to thismethod, the quality of concretes was determined (see Table 4).

The third method used in non-destructive determination ofcompressive strength was the combined method. Many research-ers have declared that using non-destructive methods in combina-tion instead of separately will result in more accurate results[28,30,31]. In this study, approximate compressive strengths ofconcretes as determined by the combined method were calculatedusing Eq. (2), as formulated by Arioglu and Koyluoglu [31], usingboth the Schmidt concrete hammer rebound number and the pulsevelocity values. The results of surface hardness and pulse velocityexperiments were averaged. Eq. (2) was used to calculate rRN+USPV

[31].

rRNþUSPV ¼ 0:00153ðRN3:V4Þ0:611 ð2Þ

where rRN+USPV is the concrete compressive strength, MPa, V is theultrasonic pulse velocity, km/s and RN is the values of reboundnumber.

The results of the compressive strength (rUA) experiment con-ducted with the uniaxial destructive method on the third, seventhand 28th days are shown in Fig. 4. Generally, parallels were ob-served in compressive strength increasing on the third, seventhand 28th days. The highest compressive strength was seen in SFRC,with an increase of 12.4%, while the smallest compressive strengthwas observed in PPFRC with a decrease of 4.4%, with respect to R1after 28 days. In conclusion, it can be said that steel fibers have po-sitive, polypropylene fibers have negative and polyester fibers haveslightly positive effects on the compressive strength of concrete.Compressive strengths of concretes on the third and seventh daysproportionally resembled concrete strength on the 28th day(Fig. 4). Accordingly, it was seen that concretes gained �66% to72% of their compressive strength on the third day and �85% to89% on the seventh day.

The results of the compressive strength of concrete at 28 daysas determined by destructive and non-destructive methods areshown in Table 5.

When compressive strength results of concretes wereevaluated:

Fig. 3. The relationship of compressive strength with values of concrete hammerrebound number.

– In rUA, SFRC had the highest value with �10.6% increase; PPFRChad the lowest, �6.1% lower than R1.

– In rRN, PPFRC had the highest value with �8% increase; PYFRChad the lowest, �13.2% lower than to R1.

– In rUSPV, R1 had the lowest value; SFRC has the highest with�25.4% increase, with respect to R1.

– In rRN+USPV, PPFRC and SFRC had the highest value with �20%increase; PYFRC had the lowest, �9.4% lower than R1.

– The highest value was seen in SFRC in rRN+USPV and rUSPV, whichare non-destructive methods.

– The lowest value was seen in PYFRC in rRN+USPV and rRN, whichare non-destructive methods.

– rUA and rUSPV results were obtained from saturated samples,while rRN was obtained from the samples dried in air. It isthought that this caused compressive strengths obtained withdestructive and non-destructive methods to appear different.For instance, PPFRC had the highest compressive strength inrRN (�12.4% higher), SFRC in rUSPV was �21.4% higher and SFRCand PPFRC in rRN+USPV were �26.9% higher with respect to R1 inrUA. It can therefore be concluded that fiber reinforcement hasan influence on concrete composites.

Generally, it was observed that the method of compressivestrength measurement, the humidity content of the sample, fiberreinforcement and fiber type influenced compressive strengthresults.

USPVs of the concretes were evaluated according to Erdogan[28]; since all concretes provided the velocity of sound >4.5 km/s,‘‘excellent’’ concrete quality was obtained. However, it is suspectedthat the results were observed to be higher because of the fact thatthe experiment was conducted on the saturated samples, whichwere taken from water treatment and accordingly, capillary poreswere filled with water.

3.3. Capillarity ratio

Capillarity experiments were conducted in compliance with TS4045 (as seen in Fig. 5) [32]. Cylindrical concretes of 10 � 20 cm,whose lateral surfaces were covered with paraffin, were initiallyweighed while dry (a). Then, the bottom surface was placed in con-tact with water up to 5 mm (b). When one surface of the concretecame into contact with water, pores sucked the water inside withthe help of surface tension. The concrete was placed in contact

Table 5Concretes compressive strength on 28th days provided by destructive and non-destructive.

Concrete type Compressive strength test method

Uniaxial Surface hardness Pulse velocity Combined

N rUA (MPa) N RN rRN (MPa) N V (km/s) rV (MPa) rRN + V (MPa)

R1 6 31.07 37 34.62 32.32 15 4.54 30.10 32.75PPFRC 6 29.23 39 36.89 34.92 15 4.66 33.63 39.21PYFRC 6 31.60 37 31.51 28.04 15 4.68 34.51 29.68SFRC 6 34.35 42 35.57 33.82 15 4.80 37.74 39.43

Fig. 6. Concretes water absorption-time and capillary coefficient (K).

H. Bolat et al. / Composites: Part B 61 (2014) 191–198 195

with water during periodic or logarithmic time intervals, whichwere determined according to standard methods; the concretewas weighed again after these time intervals. In this study, sixcylindrical concrete samples of 10 � 20 cm from each concretetype were subjected to the capillary water absorption experiment.After concretes had been in contact with water, their weights weremeasured at 15 min intervals. The amount of water that they ab-sorbed was determined as weight (gram) (c) and transferred intographic representations with respect to time. In the case wherethere was no detectable increase in the amount of water absorbed,the experiment was ended.

The amount of water absorbed by concrete as capillary actionwas proportional to surface area and square of the time passed.The proportion constant K (capillarity coefficient) was a propertydependent on material porosities [31].

The results of capillarity experiments conducted on concretesare shown in Fig. 6. Capillarity coefficients are shown in Fig. 6 interms of considering the surface area of concretes in contact withwater and maximum water absorption durations.

Accordingly:

– The highest amount of water absorption was observed in R1concrete, the lowest in PYFRC.

– The amount of water absorption in SFRC showed a parallelincrease and its final values were very close to each other, withrespect to R1.

– The amount of water absorption of PPFRC was �24.7% lowerand that of PYFRC was �39.7% lower than R1. Accordingly, itcan be said that synthetic fibers reduce the capillary waterabsorption of concrete. The reason for this is thought to be thatthe vibration used while producing concretes makes the syn-thetic fibers move upwards inside the concrete, since their den-sities are small and fibers gather in top layers of concrete inhigh amounts. In parallel with these results, in their studies,Yıldırım and Ekinci stated that there was a lower amount ofwater absorption in fibrous concretes and that the amount ofwater absorption decreased when fiber ratio increased [33].

– When capillarity coefficients of concretes were evaluated, it wasseen that as the amount of capillary water absorption increased,capillarity coefficient increased in parallel.

Fig. 5. Capillary water absor

– Capillary water absorption results seemed inversely propor-tional with uniaxial compressive strength. Normally, capillarywater absorption gives information about capillary voids. It isexpected that while the capillary voids increase, the compres-sive strength decreases [2,4]. However, in this study, the reversewas the case.

3.4. Carbonation depth

Determination of carbonation depth was performed on samplesthat were obtained after tensile strength experiments on cylindri-cal core samples of 100 � 200 mm by splitting at the end of one,three and six months (Fig. 7). Experiments were conducted onthe cylindrical samples obtained from plate concretes that hadbeen subjected to open atmosphere conditions in Ankara.

Experiments were conducted by measuring the color changethat occurred following spraying 1% phenolphthalein solution (sol-ubilized in alcohol) onto the sample surfaces at 2 cm intervals withan accuracy of 0.01 cm with the aid of a caliper. An alkali indicatorsprayed onto concrete surfaces changed the color of non-carbon-

ption experimental set.

Fig. 7. Determination of carbonation depth.

Fig. 8. Main carbonation depth values.

196 H. Bolat et al. / Composites: Part B 61 (2014) 191–198

ated concrete with a pH of 11–12.5 to dark pink; no color changewas observed in concrete where pH value decreased to 8–9 aftercarbonation [34].

Carbonation depth obtained after one, three and six monthswas measured and is graphically demonstrated in Fig. 8Accordingly:

Fig. 9. Abrasion resistan

– Carbonation depth, which was measured at the end of one,three and six months increased within the same parallels.

– Lowest carbonation depth was observed in R1. Accordingly, itcan be said that fiber reinforcement increased carbonationdepth in concrete.

– Maximum carbonation depth after six months was seen in SFRC,which was �130.8% higher than in R1.

– Generally, while concrete age increases, compressive strengthand carbonation depth also increases [35]. This study confirmsthis information.

– In general, carbonation depth within stated durations was at anormal level. Determination of the effects of carbonation depthafter long periods will provide more meaningful results.

3.5. Abrasion resistance

Abrasion resistance was determined on five 100 � 100 mmcylindrical concrete samples according to ASTM C944 principles[36]. The specimen mass was determined in approximately 0.1 gaccuracy. The experimental set-up can be seen in Fig. 9. The resultsof the abrasion resistance test on concretes are graphically shownin Fig. 10.

It was found that while the highest abrasion resistance was inSFRC, the smallest was in PPFRC. With respect to R1, PYFRC�34.6% and SFRC showed �39.7% higher, PPFRC showed �30.8%lower abrasion. The reason for SFRC and PYFRC having the highestabrasion resistance was that steel fibers and polyester fibers pickedlarger particles from concrete during the abrasion testing process.However, the reason for PPFRC to have the lowest abrasion resis-tance is that polypropylene fibers of smaller diameter were pickedfrom concrete before they picked larger particles from concreteduring the abrasion testing stage.

3.6. Freeze–thaw resistance

Freeze–thaw resistance was determined on five 100 � 200 mmcylindrical concrete samples according to ASTM C666 procedure.Fundamental transverse frequency change of concrete sampleswas recorded at every 30th freeze–thaw cycle. Frequency changesrecorded were used to calculate the relative dynamic modulus ofelasticity. Eq. (3) was used to calculate relative dynamic modulusof elasticity Pc [37].

Pc ¼ ðn2c=n2Þ � 100 ð3Þ

ce experimental set.

Fig. 10. Mean abrasion resistance values.

H. Bolat et al. / Composites: Part B 61 (2014) 191–198 197

where Pc is the relative dynamic modulus of elasticity, after ccycles of freezing and thawing, percent, n is the fundamental trans-verse frequency at 0 cycles of freezing and thawing and nc is thefundamental transverse frequency after c cycles of freezing andthawing.

Relative dynamic modulus of elasticity was used to calculatethe durability factor of concrete samples. Eq. (4) was used to calcu-late durability factor DF [37].

DF ¼ PN=M ð4Þ

Fig. 11. Relative dynamic

Fig. 12. Durability factor for control

where DF is the durability factor of the test specimen, P is therelative dynamic modulus of elasticity at N cycles%, N is the num-ber of cycles at which P reaches the specified minimum value fordiscontinuing the test or the specified number of cycles at whichthe exposure is to be terminated, whichever is less, and M is thespecified number of cycles at which the exposure is to beterminated.

The durability factor was found by determining the number ofcycles (N) at which the relative dynamic modulus of elasticityreached 50% (PN). Fig. 11 represents the graphs used to determinethe durability factors.

Results showed that the control samples (R1) possessed lowerresistance to freeze–thaw exposure than all fiber reinforced con-crete. Fig. 12 represents a qualitative estimate of the durabilityperformance of all concrete types. Reference samples were de-formed at the 270th cycle and PPFRC samples were deformed atthe 300th cycle. PYFRC and SFRC samples’ relative dynamic modu-lus of elasticity reduced below 50% at end of the 300th cycle.

The effects of macro synthetic fiber reinforcement use on phys-ical and mechanical properties of concrete.

4. Conclusion

In the present work the physical and mechanical behavior of steeland synthetic fiber reinforced concrete was investigated in terms offresh concrete properties, compressive, abrasion, carbonation depth,

modulus of elasticity.

and mixes with fiber materials.

198 H. Bolat et al. / Composites: Part B 61 (2014) 191–198

capillarity and freeze–thaw behaviors of samples. The obtained re-sults allow drawing the following concluding remarks;

– Fiber type and its geometrical structure affected the slump ofconcrete. The following results were obtained from the smallestslump observed in PYFRC, which showed 42% lower slump thanthe planned value. It can be said that an increase in the hardnessvalue of the fiber in particular reduced the slump of theconcrete.

– The amount of air was 32% higher in SFRC, 21% higher in PPFRCand 29% higher in PYFRC with respect to R1. It can be said thatfibers raised the amount of squeezed air in concrete and that, asthe fiber amount gets higher, air increases.

– It was observed that fiber reinforcement did not affect unit vol-ume weights of fresh concretes.

– With the uniaxial destructive method (rUA), increase instrengths for each type of concrete showed parallelism witheach other. The highest value was seen in SFRC in rRN+USPV

and rUSPV, which are non-destructive methods. The lowest valuewas seen in PYFRC in rRN+USPV and rRN, which are non-destruc-tive methods.

– The highest amount of water absorption was observed in R1,with the lowest observed in PYFRC. Synthetic fibers thereforereduced the capillarity of concrete.

– The increase of carbonation depth measured at the end of thefirst, third and sixth months was roughly parallel. Lowest DCwas observed in R1. Maximum DC after six months was seenin SFRC, which was �130.8% higher than in R1. Fiber reinforce-ment therefore increased DC in concrete.

– The highest abrasion resistance was found in SFRC, while thelowest was found in PPFRC. With respect to R1, PYFRC was�34.6%, SFRC �39.7% higher, PPFRC �30.8% lower in abrasionresistance. Steel fibers and polyester fibers picked larger parti-cles from concrete during the abrasion testing process. Thus,SFRC and PYFRC had the highest abrasion.

– Freeze–thaw resistance was one of the many parametersrelated to concrete durability. SFRC and PYFRC were most resis-tant to freezing–thaw factors.

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