Construction and Building Materials 44 (2013) 654–662

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Construction and Building Materials

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Estimation of compressive strength of self-compacted concrete withfibers consisting nano-SiO2 using ultrasonic pulse velocity

0950-0618/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.conbuildmat.2013.03.082

⇑ Corresponding author.E-mail addresses: Arefsadeghinik@gmail.com (A. Sadeghi Nik), O.Lotfiomra-

n@yahoo.com (O. Lotfi Omran).

Aref Sadeghi Nik a,⇑, Omid Lotfi Omran b

a Young Researchers Club, Jouybar Branch, Islamic Azad University, Jouybar, Iranb Young Researchers Club, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran

h i g h l i g h t s

� Estimation of compressive strength of SCC with fibers consisting Nano-SiO2 using UPV.� Relation between pulse velocity (PV) and compressive strength of control specimens.� Relation between PV and compressive strength of the specimens with steel fiber.� Relation between PV and compressive strength of the specimens with PP fiber.� Relation between PV and compressive strength of the specimens with glass fiber.

a r t i c l e i n f o

Article history:Received 23 March 2012Received in revised form 15 March 2013Accepted 22 March 2013Available online 19 April 2013

Keywords:Compressive strengthSelf-compacted concreteFibersNano-SiO2

Ultrasonic pulse

a b s t r a c t

In this research the performance of ultrasonic pulse velocity in concrete is examined as a nondestructiveexperiment, in order to estimate compressive strength of fiber-reinforced self-compacted concrete withnano particles. For this purpose there were 40 mix plans including four groups of A, B, C and D in whichcement was replaced with 0, 2, 4 and 6 vol.% of nano-SiO2 respectively. In this experiment a comparisonwas made between the four groups which included three types of fibers (steel: 0.2, 0.3 and 0.5 vol.%, poly-propylene: 0.1, 0.15 and 0.2 vol.% and glass: 0.15, 0.2 and 0.3 vol.%). Cube specimens were tested in orderto determine ultrasonic velocity. The compressive strength was also tested. According to the results, rela-tions were established between ultrasonic velocity in the specimens and the compressive strength at dif-ferent ages and so the range of the velocity of the waves was also determined for this kind of concrete.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Previous researches showed that using fibers in concrete wouldcause an increase in its striking and scratching strength and bend-ing and tensile strength and a decrease in cracking [1–4]. Sinceself-compacted concrete has a low viscosity there are no problemslike separating and getting watery, moreover it can be consolidatedbecause of its heavy weight and any internal or external vibrationis needed. This property is a great help to construct the structurewhere there is a jam of bars. On the other hand nanotechnologyhas caused amazing revolution in scientific areas for the last fewyears. Nano particles resulted from nanotechnology can act as avery active artificial pozzolan in cement-basis materials and havean influence on their structure and improve them. This is due tothe physical and chemical properties of such particles [5–9]. There-

fore using self-consolidated concrete with nano particles can playan important role in building complex structures.

Today, civil engineers all around the world are interested in thequality control of concrete by means of nondestructive methodsbecause of the followings:

� Doubtfulness about the strength of ordinary standardspecimens.� Local damages due to airing, fire and chemical effects.� Low cost and short length of the experiment.� Its simplicity compared with destructive methods.

Other different techniques of the same kind have also been ac-cepted [10–14].

Ultrasonic pulse velocity technique, offered based on the calcu-lation of transmission speed of ultrasonic pulses in concrete, is oneof the nondestructive testing methods with the help of which it ispossible to foresee some of the properties of the concretestructures [13]. Researchers have done a lot of studies on different

A. Sadeghi Nik, O. Lotfi Omran / Construction and Building Materials 44 (2013) 654–662 655

concretes with the help of ultrasonic pulse velocity and get positiveresults [15–20]. Existing air bubbles and the pores inside the solidobject (solid object density) affects the way ultrasonic pulsestransmit through it. Ultrasonic velocity depends on many factorssuch as the type of cement, concrete age, water–cement ratio,aggregate used in concrete, curing, measuring distance length,and the temperature of the measuring zone [10–13]. There havebeen a lot of efforts made to study the influence of effective param-eters on the velocity of ultrasonic pulses [21–25]. Rommel andMalhotra have studied the velocity of ultrasonic pulses in concretespecimens with different water–cement ratio and gravel amounts.They introduced the concrete specimen and the range of ultrasonicvelocity regarding the kind of variables and finally introduced apattern for the evaluation of concrete quality [21,22]. Knowing thatthe existing air bubbles in self-consolidated concrete is less thanthe ordinary concrete due to its special properties and the powderingredient; efforts have been made in this research to study theperformance of nondestructive method in self-compacted concretecontaining fibers and nano particles to introduce a relation be-tween compressive strength and the velocity of ultrasonic pulsesin the specimens. In this research concrete specimens were madewith 40 mix plans containing different percentages of steel, poly-propylene and glass fibers and also nano-SiO2. Ultrasonic pulseexperiment was conducted on the specimens at the age of 7, 28and 90 days.

Fig. 1. Grading curve for fine and coarse aggregates used in the experiment.

Table 1Chemical compositions of cement and limestone powder (wt.%).

Items SiO2 Al2O3 Fe2O3 CaO MgO SO3 CaCo3 L.O.I

PC 21.90 4.86 3.30 63.33 1.15 2.10 – 2.40LS 0.45 0.33 0.02 52.35 0.02 52.35 99.3 –

PC: ordinary Portland cement.LS: limestone powder.

Table 2Analysis of physical properties of cement.

Blaine (cm2/g) Expansion (autoclave) (%) Compressive strength (kg/cm2)

3 days 7 days 28 days

3050 0.05 185 295 397

Table 3Properties of nano-SiO2.

Diameter (nm) Surface–volume ratio (m2/g) Density (g/cm3) Purity (%)

15 ± 5 160 ± 20 <0.15 >99.9

Fig. 2. AFM image of used nano-SiO2.

2. Materials

The gravel used in the experiment is maximum 12.5 mm and lies in gradingcurve of standard ASTM and the sand was selected from sieve No. 4.75 mm equiv-alent to 76% sand. Grading curve for fine and coarse aggregates with ASTM C33standard limits are shown in Fig. 1 [26]. The cement used in the experiment wasof Portland type II produced by Mazandaran cement Co. for which the physicaland chemical properties are presented in Tables 1 and 2. Limestone powder withthe specific gravity of 2.6 g/cm3 was used to make the concrete for which the chem-ical properties are presented in Table 1.

In this research a superplasticizer upon ether carboxylic was used in all mixplans with the concentration of 7 kg/m3 (its trade name is GELENIUM-110P) andthe specific gravity of 1.1 g/cm3.

Fibers used were of three kinds: steel, propylene and glass. Used nano-SiO2 con-tains over 99% of amorphous silica for which the physical properties are presentedin Table 3. The silica used in different series was 2%, 4% and 6% of the weight of ce-ment. Also the AFM image of nano-silica used in the mixing is presented in Fig. 2.

3. Experimental method and mix plan

Ultrasonic pulse velocity determining test and compressive strength of the cubespecimens (100 � 100 � 100 mm) at the age of 7, 28 and 90 days for 40 mix plansincluding four groups of A, B, C and D in which cement was replaced with nano-SiO2

of 0, 2, 4 and 6 wt.% of cement respectively, was conducted. Each group includedthree kinds of fibers (steel: 0.2, 0.3 and 0.5 vol.%, polypropylene: 0.1, 0.15 and0.2 vol.% and glass: 0.15, 0.2 and 0.3 vol.%) all presented in Table 4. In all 40 plans,all the components of the concrete were fixed except for the kind and the amount offibers and the amount of nano-SiO2. The amount of gravel, sand, cement, limestonepowder and superplasticizer in one cubic meter were 722, 826, 413, 288 and 7 kgrespectively. Water–cement material ratio (nano-SiO2 + cement) equals to 0.39and plan No. A1 which lacks fibers and nano-SiO2 is introduced as the control plan.(Vf in Table 4 is the volumetric percentage of fiber, i.e. fiber–concrete volumetricratio).

Table 4Details of specimens mix designs.

Mixno.

Groups Nano silica(%)

Fiber Vf (%) Gravel (kg/m3)

Sand (kg/m3)

Lime stone powder (kg/m3)

Cement (kg/m3)

Nano silica (kg/m3)

Water (kg/m3)

SP (kg/m3)

1 A 0 – 722 826 288.9 413.1 0 162 72 St 0.2 722 826 288.9 413.1 0 162 73 0.3 722 826 288.9 413.1 0 162 74 0.5 722 826 288.9 413.1 0 162 75 PP 0.1 722 826 288.9 413.1 0 162 76 0.15 722 826 288.9 413.1 0 162 77 0.2 722 826 288.9 413.1 0 162 78 Glass 0.15 722 826 288.9 413.1 0 162 79 0.2 722 826 288.9 413.1 0 162 7

10 0.3 722 826 288.9 413.1 0 162 7

1 B 2 – 722 826 288.9 396.6 16.5 153.7 72 St 0.2 722 826 288.9 396.6 16.5 153.7 73 0.3 722 826 288.9 396.6 16.5 153.7 74 0.5 722 826 288.9 396.6 16.5 153.7 75 PP 0.1 722 826 288.9 396.6 16.5 153.7 76 0.15 722 826 288.9 396.6 16.5 153.7 77 0.2 722 826 288.9 396.6 16.5 153.7 78 Glass 0.15 722 826 288.9 396.6 16.5 153.7 79 0.2 722 826 288.9 396.6 16.5 153.7 7

10 0.3 722 826 288.9 396.6 16.5 153.7 7

1 C 4 – 722 826 288.9 380 33 145.5 72 St 0.2 722 826 288.9 380 33 145.5 73 0.3 722 826 288.9 380 33 145.5 74 0.5 722 826 288.9 380 33 145.5 75 PP 0.1 722 826 288.9 380 33 145.5 76 0.15 722 826 288.9 380 33 145.5 77 0.2 722 826 288.9 380 33 145.5 78 Glass 0.15 722 826 288.9 380 33 145.5 79 0.2 722 826 288.9 380 33 145.5 7

10 0.3 722 826 288.9 380 33 145.5 7

1 D 6 – 722 826 288.9 363.5 49.6 137.2 72 St 0.2 722 826 288.9 363.5 49.6 137.2 73 0.3 722 826 288.9 363.5 49.6 137.2 74 0.5 722 826 288.9 363.5 49.6 137.2 75 PP 0.1 722 826 288.9 363.5 49.6 137.2 76 0.15 722 826 288.9 363.5 49.6 137.2 77 0.2 722 826 288.9 363.5 49.6 137.2 78 Glass 0.15 722 826 288.9 363.5 49.6 137.2 79 0.2 722 826 288.9 363.5 49.6 137.2 7

10 0.3 722 826 288.9 363.5 49.6 137.2 7

St: steel fiber.PP: polypropylene fiber.SP: superplasticizer.

Fig. 3. Pundit tester device. Fig. 4. Location of test points.

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Table 5Result for compressive strength and pulse transmission velocity.

Mix no. Groups 7 days 28 days 90 days

F 0c (MPa) V (km/s) F 0c (MPa) V (km/s) F 0c (MPa) V (km/s)

1 A 65 5.07 73 5.20 80 5.402 62 5.05 74.3 5.20 81 5.403 64.5 5.07 81.5 5.31 85.3 5.434 65 5.07 78 5.23 83 5.405 64.5 5.05 71.7 5.15 74.8 5.316 63.7 5.02 69.3 5.15 71.3 5.297 60.6 4.95 66.6 5.12 68.2 5.238 61 5.05 82 5.31 84.7 5.499 59 5.02 78.5 5.26 80 5.43

10 59 5.02 72.8 5.18 77 5.34

11 B 68.5 5.10 75 5.23 82.2 5.4312 65 5.07 77.5 5.26 82 5.4313 65.7 5.07 82.7 5.31 84.6 5.4914 66 5.05 78.2 5.26 82.5 5.4015 65.4 5.07 73.6 5.18 75 5.3116 64 5.05 70.8 5.18 73.7 5.3417 61.5 4.97 68 5.15 70 5.2618 62.5 5.07 82.6 5.31 85 5.4919 60.7 5.10 80.5 5.29 82.7 5.4620 59.3 5.10 78.7 5.26 80.3 5.43

21 C 78.7 5.20 86 5.37 87.7 5.5222 77.2 5.15 85.7 5.37 88.3 5.5823 79.2 5.20 88 5.43 91.2 5.6124 79 5.20 87.2 5.40 87.5 5.5825 74.3 5.12 82.6 5.26 83.2 5.4626 72.5 5.10 78.7 5.26 81.1 5.4327 71.7 5.10 76.5 5.23 80.6 5.4328 69.5 5.15 88.7 5.40 89.8 5.5529 66 5.20 84 5.37 84.3 5.4930 64.4 5.20 83.6 5.34 84 5.49

31 D 75 5.15 85 5.31 86.3 5.5232 74 5.15 85.2 5.34 86.7 5.5533 74.3 5.15 86.7 5.37 87 5.5534 73.2 5.12 86.1 5.37 86 5.5535 72.3 5.10 79.6 5.26 81.7 5.4636 67.4 5.07 77 5.23 82.3 5.4937 68.5 5.07 82.3 5.18 78.3 5.3738 67 5.12 86.5 5.37 78.2 5.4939 64.7 5.15 83 5.34 84.5 5.4640 64 5.15 82.7 5.34 84 5.49

Fig. 5. The influence of steel fibers on ultrasonic pulse velocity.Fig. 6. The influence of polypropylene fibers on ultrasonic pulse velocity.

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Nondestructive test was first conducted on the specimens at mentioned ages inorder to determine ultrasonic pulse transmission time by means of direct transmis-sion method, using pundit tester devise shown in Fig. 3.

Frequencies of pulses were 54 kHz and transmission time was measured at micro-second and shown on a digital screen to 0.1 ls. According to the other researchers,using ultrasonic pulses in the range of 40–80 kHz is suitable for the evaluation ofthe concrete [10,21]. In all the experiments, refractory grease was used to connecttransducers on the surface of the concrete. Before the experiment was conducted,the surfaces were made flat and smooth. During the transmission of pulses five pointsof the concrete were checked so that the entire surface and the whole volume of thespecimen could be examined. Fig. 4 shows the location of the five points on each cube.For the pulses of each specimen, the average velocity in directions perpendicular toeach other was considered. Also the related strength was considered as the averagestrength of the two same specimens. After the test, finding the mean for the results,

there was one figure as the time of transmission was recorded for the proposed spec-imen. Calculating the transmission time for the pulses and regarding the distance of100 mm (specimens of 100 � 100 � 100 mm) and using the following formula, ultra-sonic pulse transmission time was determined at km/s.

V ¼ LT

ð1Þ

where L is transmission distance (km), T is transmission time in the concrete (s) andV is pulse transmission velocity in concrete (km/s) [13].

After conducting nondestructive test on concrete specimens, a compressive testwas also conducted on them at the speed of 0.3 kN/s and the compressive strengthwas determined at MPa. The results for compressive strength and pulse transmis-sion velocity are presented in Table 5.

Fig. 7. The influence of glass fibers on ultrasonic pulse velocity.

Fig. 8. The influence of the percentage of nano-SiO2 on the ultrasonic pulse velocity.

Fig. 9. The influence of the concrete age on ultrason

Fig. 10. The influence of the concrete age on ultrasonic p

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4. Results and discussion

In this section regarding experimental results, some diagramsare introduced to show the relationship between effective param-eters such as concrete age, the amount of nano-SiO2 and the pro-portion of existing fibers and the way they influence each other.Following we discuss above mentioned issues.

4.1. The influence of the type and amount of fibers on ultrasonic pulsevelocity

In Figs. 5–7, some cases of the influence of the type andamount of fibers on ultrasonic pulse velocity are presented.Fig. 5 shows the influence of steel fibers on ultrasonic pulsevelocity. It does not show significant changes in increasing theultrasonic pulse velocity for different age of the concrete, so thatthe maximum rate of velocity is 5.43 km/s for the 90-day-oldspecimen with 0.3% of fiber, this velocity for the control samplewithout fiber at the same age is 5.40 km/s. In contrast, the min-imum rate of velocity is 5.05 km/s for the 7-day-old specimenwith 0.2% fiber, this amount of velocity is even less than thatof the control sample at the same age, which is 5.07 km/s.

Fig. 6 shows the influence of polypropylene fibers on ultrasonicpulse velocity. It can be seen that when the amount of polypropyl-ene fibers increases, the ultrasonic pulse velocity declines so thatthe maximum velocity is 5.31 km/s for a 90-day-old specimen with0.1% of fiber added, while the rate is 5.40 km/s for the control

ic pulse velocity in specimens with steel fibers.

ulse velocity in specimens with polypropylene fibers.

Fig. 11. The influence of the concrete age on ultrasonic pulse velocity in specimens with glass fibers.

(A) Specimens without fibers and nano-SiO2.

(B) Specimens without fibers and with 2% of nano-SiO2.

(C) Specimens without fibers and with 4% of nano-SiO2.

(D) Specimens without fibers and with 6% of nano-SiO2.

Fig. 12. Effect of concrete ages (without fibers and samples containing 0%, 2%, 4%, 6% nano-SiO2). (A) Specimens without fibers and nano-SiO2. (B) Specimens without fibersand with 2% of nano-SiO2. (C) Specimens without fibers and with 4% of nano-SiO2. (D) Specimens without fibers and with 6% of nano-SiO2.

Table 6Relations between pulse velocity and compressive strength of the specimens.

Experimental groups A B R2

General 2.862 0.617 0.967

St nano 0% 1.305 0.771 0.929St nano 2% 2.662 0.635 0.916St nano 4% 16.07 0.307 0.881St nano 6% 9.759 0.397 0.816

PP nano 0% 5.313 0.494 0.846PP nano 2% 4.942 0.509 0.840PP nano 4% 12.91 0.340 0.781PP nano 6% 10.26 0.382 0.628

Glass nano 0% 1.195 0.782 0.892Glass nano 2% 0.893 0.835 0.827Glass nano 4% 2.623 0.633 0.754Glass nano 6% 1.616 0.724 0.747

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specimen without fiber at the same age. Also the minimum rate is4.95 km/s for the 7-day-old specimen with 0.2% of fiber added,while it is 5.07 km/s for the control specimen without fiber atthe same age.

Fig. 7 shows the influence of glass fibers on ultrasonic pulsevelocity. It can be seen that adding 0.15% of glass fiber thevelocity increases in all the specimens except for the 7-day-old one; but adding more glass fiber by 0.2% and 0.3%, velocitydecreases; so that the maximum velocity is 5.49 km/s for the90-day-old specimen with 0.15% glass fiber added while it is5.40 km/s for the control specimen without fiber at the sameage. Meanwhile the minimum velocity is 5.02 km/s for the 7-day-old specimens with 0.2% and 0.3% of fiber added, while itis 5.07 km/s for the control specimen without fiber at the sameage.

Fig. 13. Relation between pulse velocity and compressive strength of controlspecimens.

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4.2. The influence of nano-SiO2 proportion on the ultrasonic pulsevelocity

The influence is shown in Fig. 8. The overall view indicates thatthe more nano-SiO2 used in the concrete the higher velocity of theultrasonic pulses is observed. The reason can be referred to the high-er density of the cement part of the concrete, especially in the trans-mission zone, due to the higher proportion of nano-SiO2 [10,11]. The

Fig. 14. Relation between pulse velocity and compre

Fig. 15. Relation between pulse velocity and compressive

cement part of the concrete is less able to transmit the pulses; so re-duced pores and micro cracks cause higher velocity.

As it can be seen in Fig. 8 adding 2% and 4% of nano-SiO2, theultrasonic pulse velocity constantly increases, but adding evenmore nano-SiO2 up to 6%, there would not be a significant increasein velocity especially at the age of 7 and 28 days. Maximum in-crease in velocity goes to the specimens with 4% and 6% of nano-SiO2 at the age of 90 days, which is 5.52 km/s in both. While it is5.40 km/s for the control specimen without nano-SiO2 at the sameage; meanwhile the minimum velocity goes to the specimen with2% of nano-SiO2 at the age of 7 days which is 5.10 km/s, while it is5.07 km/s for the control specimen.

4.3. The influence of the age of concrete on the ultrasonic pulse velocityand its compressive strength

This influence can be seen in Figs. 9–11. The overall view indi-cates that in the same mentioned conditions; the older the con-crete is the higher the velocity will be. It seems this is due to theelimination of capillary pores and cracks in the cement part ofthe concrete and hydration development when it gets older, there-fore the nominal resistance against the transmission of pulses willdecrease. Changing in compressive strength and ultrasonic pulsevelocity due to aging in self- compacted concrete without fibersand with nano-SiO2 as much as 0, 2, 4 and 6 wt.% of the cementused in the concrete, can be seen in Fig. 12A–D.

ssive strength of the specimens with steel fiber.

strength of the specimens with polypropylene fiber.

Fig. 16. Relation between pulse velocity and compressive strength of the specimens with glass fiber.

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4.4. The relationship between ultrasonic pulse velocity andcompressive strength of the cube specimens

In case of using ultrasonic pulse velocity to determine compres-sive strength of the concrete, it should be said that there is no cer-tain relationship between the two parameters. Elasticity module isrelated to the compressive strength. On the other hand there is arelationship between the velocity and elasticity module and thedensity of the concrete. So there is a good reason to study the com-pressive strength of the concrete on the ultrasonic pulse velocitybasis. Many researchers have shown that the relationship betweenthe compressive strength and pulse velocity can be estimated bythe following exponential function:

F 0c ¼ A � eðBVÞ ð2Þ

where F 0c is the compressive strength, V is the pulse velocity (km/s),A and B are empirical constants [11].

According to the function, regressing an exponential curveamong the data, relationships between the pulse velocity andthe compressive strength for the cube specimens at differentages and for all the specimens regardless of their age are definedand presented in Table 6. In Figs. 13–16 regression of the curveon the data with the formula of the regressed curve and alsoRegression Coefficient (R) for all the specimens are presented.The closer R2 (Regression Coefficient) is to 1 the less is thedispersion.

5. Conclusions

In this research, important parameters of the mix plan for fiberconcrete with the presence of different percentages of steel, poly-propylene and glass fibers and also using nano-SiO2, on ultrasonicpulse velocity were studied. The results of the study are as follow:

� Proposed formula by former researchers [11], which were anexponential relationship between compressive strength andultrasonic pulse transmission velocity in concrete, has a goodregression with the experimental results from this study.� It seems that increasing the volumetric percentage of steel fiber

up to 0.3% will cause an increase in pulse velocity. While in caseof polypropylene fibers, the increase of the volumetric percent-age will cause a decrease in the velocity, for the case of glassfiber there is first an increase in velocity and then a decrease.

� Also when the percentage of nano-SiO2 is increased up to 4% ofthe cement weight in the specimens, there is first an increase inboth compressive strength and pulse velocity but then theyalmost decrease. This is due to filling and pozzolan effect ofnano-SiO2 in reinforcing fiber zone and cement matrix. It’safterward decline is due to lumping of the silica which is itselfbecause of its high specific surface. A physical reaction causesthe silica to get together and make unstable lumps. In this study4% of silica is applicable.� The older the concrete is the higher the pulse transmission

velocity will be.

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