In the present study, the uniformity and potential internal defects of concrete elements in situ were assessed by using Ultrasonic Pulse Velocity (UPV) testing method according to TCVN 9357:2012. Thirteen cross beams with dimension of 4.8 × 1.5 × 1.5 m3 were selected to measure the pulse velocity. Three cross beams were used to check potential internal defects in concrete and 10 cross beams were used to assess the uniformity of concrete in the elements.
Journal of Science and Technology in Civil Engineering NUCE 2018 12 (5): 20–27 THE ASSESSMENT OF CONCRETE QUALITY BY ULTRASONIC PULSE VELOCITY Van Viet Thien Ana,∗ a Faculty of Building Materials, National University of Civil Engineering, 55 Giai Phong road, Hai Ba Trung district, Hanoi, Vietnam Article history: Received 10 August 2018, Revised 27 August 2018, Accepted 30 August 2018 Abstract In the present study, the uniformity and potential internal defects of concrete elements in situ were assessed by using Ultrasonic Pulse Velocity (UPV) testing method according to TCVN 9357:2012 Thirteen cross beams with dimension of 4.8 × 1.5 × 1.5 m3 were selected to measure the pulse velocity Three cross beams were used to check potential internal defects in concrete and 10 cross beams were used to assess the uniformity of concrete in the elements The results showed that there is no potential internal defect with size over 100 mm in three tested beams and concrete quality of all tested beams is good with the coefficient of variation (CV) of ultrasonic pulse velocity results of all tested points is lower than 2% Keywords: concrete; homogeneity; internal defects; ultrasonic pulse velocity https://doi.org/10.31814/stce.nuce2018-12(5)-03 c 2018 National University of Civil Engineering Introduction Ultrasonic Pulse Velocity (UPV) test is one of non-destructive testing methods frequently used to assess the quality of concrete structures A pulse of longitudinal vibrations is generated by an electroacoustical transducer, which is held in contact with one surface of the concrete When the pulse is transmitted into the concrete from the transducer, it undergoes multiple reflections at the boundaries of the different material phases within the concrete The first waves to reach the receiving transducer are the longitudinal waves These waves are converted into an electrical signal by a second transducer Longitudinal pulse velocity is given by: L v= (1) T where v is the longitudinal pulse velocity, (m/s); L is the path length, (m); T is the time taken by the pulse to through that length, (s) The equipment consists essentially of an electrical pulse generator, a pair of transducers, an amplifier and an electronic timing device to measure the time interval between the initiation of a pulse produced at the transmitting transducer and its arrival at the receiving transducer (Fig 1) The equipment should be capable of measuring transit time over path lengths ranging from about 100 mm to the maximum thickness to be inspected to an accuracy of ±1% Generally the transducers should be in the range of 20 to 150 kHz although frequencies as low as 10 kHz may be used for very long concrete path lengths and as high as MHz for mortars and grouts or for short path lengths High frequency pulses have a well-defined onset but, as they pass through the concrete, become attenuated more rapidly than ∗ Corresponding author E-mail address: thien.an.dhxd@gmail.com (An, V V T) 20 inspected to an accuracy of ±1% Generally the transducers should be in the range of 20 to 150 kHz although frequencies as low as 10 kHz may be used for very longconcrete path lengths and as high as MHz for mortars and grouts or for short path lengths High frequency pulses have a well-defined onset but, as they pass through the concrete, V V T rapidly / Journal ofthan Sciencepulses and Technology in Civilfrequency Engineering It is therefore become attenuatedAn,more of lower preferable touse high frequency transducers short path lengthstransducers and low for frequency pulses of lower frequency It is therefore preferablefor to use high frequency short path transducers for long path lengths Transducers with a frequency of 50 kHz to 60 kHz lengths and low frequency transducers for long path lengths Transducers with a frequency of 50are kHz suitable common [1] to 60 kHzfor are most suitable for mostapplications common applications [1] FigureFigure Schematic ofofPulse Apparatus Schematic Pulse Velocity Velocity Apparatus [2] [2] UPV is a function of the bulk modulus, shear modulus and density of the material is aUPV function of the bulk modulus density because of the material [1] Thus, [1].UPV Thus, is affected by modulus, concreteshear porosity andand cracking they directly UPV is affected by concrete porosity and cracking because they directly influence the aforementioned influence the aforementioned properties, and high crack density and high porosity yield properties, and high crack density and high porosity yield lower UPV values Moreover, different lower UPV values Moreover, different concrete mixtures can have different densities concrete mixtures can have different densities (e.g variation in the content of air entrained or the (e.g variation the content of air entrained aggregate resulting aggregate density),inresulting in differences in UPV thatorarethe associated withdensity), the level of damage in This differences in UPV that are associated with the level of damage This explains why explains why the UPV can vary from one structure to another, even if the concrete exhibits nothe signs UPV can [3] varyMeasurement from one structure to another, even ifpulses the concrete exhibits no signs of of damage of the velocity of ultrasonic of longitudinal vibrations passing through may be usedof forthe the velocity followingof applications damageconcrete [3].Measurement ultrasonic[4–8]: pulses of longitudinal vibrations Determination of the homogeneity of concrete in and between members passing through concrete may be used for the following applications [4, 5, 6, 7, 8]: - Measurement of changes occurring with time in the properties of concrete Determination of velocity the homogeneity in of and between members Correlation of pulse and strengthofasconcrete a measure concrete quality Measurement with in the properties Determination ofof thechanges modulusoccurring of elasticity andtime dynamic Poisson’s ratioof ofconcrete the concrete - Correlation pulse velocity and strength as a measure of concrete quality The present studyofassesses the uniformity and potential internal defects of concrete beam elements in situ These concrete structures have appeared some defects surface ofPoisson's the elements such hon- Determination of the modulus of elasticity andondynamic ratio ofasthe eycombs, concrete.surface cracks and cold joints Therefore, the quality of hardened concrete in the structures should be checked by non-destructive testing (NDT) methods as the request of the employer, client The present study thedimension uniformity internal defects of and consultant Thirteen crossassesses beams with of 4.8and × 1.5potential × 1.5 m3 were selected to measure concrete beamelements in situ These concrete structures have appeared some defects on the pulse velocity Three cross beams were used to check potential internal defects in concrete and ten cross beams were used to assess the uniformity of concrete in the elements Experimental design and methods 2.1 Experimental design The homogeneity of concrete is evaluated by comparing the pulse velocity of the ultrasonic signal through concrete according to TCVN 9357:2012 - Normal concrete - Nondestructive methods Assessment of concrete quality using ultrasonic pulse velocity [4] The equipment is PUNDIT LAB 21 and ten cross beams were used to assess the uniformity of concrete in the elements Experimental design and methods 2.1 Experimental design An, V V T / Journal of Science and Technology in Civil Engineering The homogeneity of concrete is evaluated by comparing the pulse velocity of the Van, V.To T A./ A./ Journal ofaccording Science and Technology Civilon Engineering V T Journal Science Technology Civil Engineering -ultrasonic Proceq ultrasonic tester reduce theof effect of and steel reinforcements the pulse velocity value, the signal Van, through concrete to TCVNinin9357:2012Normal concrete steel bar detector is also used The arrangement of the transducers is opposite faces (direct transmisNondestructive - Assessment ofwill concrete quality atusing pulseIf Ultrasonic pulse methods velocity through concrete be examined all the theultrasonic tested points If tested points sion) The distance between tested areasconcrete or tested will pointsbe onexamined the surface at of all the element should be less velocity [4] The equipment is PUNDIT LABProceq ultrasonic tester.To reduce the results is less less than 2-3%, concrete in the the tested tested areas the of all thetoresults is 2-3%, concrete in areas thanvariation or equal tocoefficient 1000 mm According Appendix C ofthan TCVN 9357-2012 [4], the concrete in tested effect of steel reiforcements on the pulse velocity value, the steel bar detector is also is considered homogeneous whenthat the there variation ofwith ultrasonic pulse velocity iselements homogeneity and itascan be concluded concluded that there arecoefficient no defects defects with the size size over 100 are no the over 100 used The arrangement of the transducers is opposite faces (direct transmission).The results is less than 2–3% any result result having having aa too too low low velocity velocity value value (lower (lower than than mm in this tested area If there is any distance between tested areas or tested points on the surface of the be In order to assess the homogeneity of concrete in cross beam, array of element the testedshould areas were value), the the ultrasonic ultrasonic pulse pulse velocity velocity at at this this tested tested point point is is 20% compared to the average value), determined the whole surface of the structuresto with the distance between the9357-2012[4], tested areas doesthe not less than oronequal to 1000 mm According Appendix C of TCVN result is correct, correct, there is potential potential internalpulse defect at this this rechecked carefully If the low result is there is internal defect at exceed 1000 mm Inelements each tested 03 tested are measured thethe ultrasonic velocity to concrete in tested is area, considered aspoints homogeneous when variation coefficient be estimated by adding adding aa new new array array of of tested tested points points point The sizevalues of this defect will be estimated by get the average of the tested area (Figs and 3) of ultrasonic pulse velocity results is less than 2-3% with a denser grid in this area Figure Figure Array of tested areas and tested points on the cross beams Array of tested areas and tested points on the cross beams 222 with the theofgrid grid of 100 100inmm mm in 1000 1000 3000 of mm ontested the Figure Array of tested with of in 3000 mm the In order to assess the points homogeneity concrete cross beam,xxarray theon cross cross beams beams areas were determined on the whole surface of the structures with the distance between the tested areas does not exceed 1000 mm In each tested area, 03 tested points are measured the ultrasonic pulse velocity to get the average values of the tested area (Figs and 4) The internal defects in concrete located between two sensors of ultrasonic testing which have their size bigger than diameter of the sensor will decrease the pulse velocity of ultrasonic through concrete The accuracy of the experiment and the detectable size of defects depend on the distance between tested points arranged on the structures To assess thetesting potential internal defectsinternal in concrete of cross beams, an areatester of 1000 a) Homegeneity b)(b)Potential c) Ultrasonic Potential internal defect c)(c) Ultrasonic tester (a) Homegeneity testing Potential internal defectdefect testing Ultrasonic tester x 3000 mm on the selected cross beam testing will be selected and examined Array of tested testing points with the grid of 100 mmofwill be arranged on thisontested area (Figs and 4) Figure Measurement of ultrasonic pulse concrete beams Figure Measurement ultrasonic pulse velocity on beams ultrasonic pulsevelocity velocity on concrete concrete beams 2.2 Calculation of theincoefficient of variation of velocity results: variation (CV) of pulse pulse velocity testing results: The internal defects concrete located between (CV) two sensors of ultrasonic which have their size bigger diameter of the will decrease velocitythrough of ultrasonic concrete The than homogeneity of sensor concrete beams is evaluated the coefficient of concrete beams the is pulse evaluated through thethrough coefficient of The accuracy of the experiment and the detectable size of defects depend on the distance between variation of pulse velocity results The coefficient of variation (CV) of ultrasonic pulse tested points arranged on the structures The coefficient of variation (CV) of ultrasonic pulse velocity results definedinternal as thedefects ratio the deviation (S) to the mean of ratio of of concrete the standard standard deviation (S) toof the mean of pulse pulse To assess the is potential in of cross beams, an area 1000 × 3000 mm2 velocity resultscross as followed: on the selected beam will be selected and examined Array of tested points with the grid of 100 mm will be arranged on this tested area (Figs and & & 4) Ultrasonic pulse velocity through concrete $$% % 𝑥100 (2) will be examined at all the tested points 𝐶𝑉 If coefficient of all the results is less than 𝐶𝑉the= =variation 𝑥100 (2) ' '() () to 3%, concrete in the tested areas is homogeneity and it can be concluded that there are no defects nn with ((V Vii V Vtbtb)) å å 22 i =1 ((SS )) == H H 22 KK i =1 22 ((nn 11)) (3) (3) Ultrasonic pulse velocity through concrete will be examined at all the tested points If the variation coefficient of all the results is less than 2-3%, concrete in the tested areas is homogeneity and it can be concluded that there are no defects with the size over 100 mm in this tested area If there is any result having a too low velocity value (lower than An, V V T / Journal of Science and Technology in Civil Engineering 20% compared to the average value), the ultrasonic pulse velocity at this tested point is with the size over 100 mm in this tested area If there is any result having a too low velocity value rechecked carefully If the low result is correct, there is potential internal defect at this (lower than 20% compared to the average value), the ultrasonic pulse velocity at this tested point is point The size of this willis correct, be estimated by adding a new array tested rechecked carefully If thedefect low result there is potential internal defect at thisof point The points size with a denser grid in this area of this defect will be estimated by adding a new array of tested points with a denser grid in this area FigureFigure Array ofoftested points theofgrid of 100 mm in 1000 x the 3000 on the Array tested points withwith the grid 100 mm in 1000 × 3000 mm2 on crossmm beams cross beams 2.2 Calculation of the coefficient of variation (CV) of pulse velocity results The homogeneity of concrete beams is evaluated through the coefficient of variation of pulse velocity results The coefficient of variation (CV) of ultrasonic pulse velocity results is defined as the ratio of the standard deviation (S) to the mean of pulse velocity results as followed: CV = with n a) Homegeneity testing and S KH × 100 Vtb (2) (Vi − Vtb )2 b) Potential internal defect c) Ultrasonic tester(3) i=1 = (n − 1) testing Figure Measurement of ultrasonicnpulse velocity on concrete beams S KH V i 2.2 Calculation of the coefficient of variationi=1(CV) of pulse velocity results: Vtb = n (4) The homogeneity of concrete beams is evaluated through the coefficient of where S KH is standard deviation of the measurement, (S KH )2 is variance; Vtb is mean of ultrasonic pulse variation of pulse velocity results The coefficient of variation (CV) of ultrasonic pulse velocity results, (m/s); Vi is ultrasonic pulse velocity result at tested point (area) number i, (m/s); n is velocity as the ratio of the standard deviation (S) to the mean of pulse the totalresults numberisofdefined tested points (areas) velocity results as followed: Results and discussion $& 𝐶𝑉 = '% 𝑥100 3.1 Potential internal defects in concrete beams () (2) n The ultrasonic pulse velocity values at the tested points (Vi - Vtbon ) the elements is measured and recorded å H areas i =1 At first, the homogeneity of concrete at the (tested (1000×3000 mm2 ) with 341 tested points/beam SK ) = ( n - 1(CV) ) with (3) (Fig 4) was assessed by the coefficient of variation of ultrasonic pulse velocity results (Table 1) The results showed that the coefficient of variation (CV) of ultrasonic pulse velocity results of all tested points at all the 03 tested areas is lower than 2% The distribution of ultrasonic pulse 23 of variation (CV) of ultrasonic pulse velocity results of all tested points at all ed areas is lower than 2% The distribution of ultrasonic pulse velocity values oints on the elements (Figs.5, and 7) also showed how concentrated the ested points are According to TCVN 9357:2012, concrete in the tested areas An, V V T / Journal of Science and Technology in Civil Engineering ed homogeneous velocity values at tested points on the elements (Figs 5, and 7) also showed how concentrated the use the grid of the tested points array is 100 mm, the difference between the values of tested points are According to TCVN 9357:2012, concrete in the tested areas is considered pulse velocity result of all the tested points and the average value is not homogeneous 20% (Table 1), Because there is no defectarray withisdefect’s 100 between the ultrasonic pulse the potential grid of theinternal tested points 100 mm,size the over difference tested concrete areas velocity result of all the tested points and the average value is not exceeded 20% (Table 1), there is no Results ofpotential investigation homogeneity and size potential internal defects in concrete areas internalofdefect with defect’s over 100 mm in the tested concrete beams Name of lement eam 1A eam 2A eam 3A Table Results of investigation of homogeneity and potential internal defects in concrete beams Ultrasonic pulse velocity, Variance, Coefficient of Ultrasonic pulse velocity, m/s Variance, m/s of Name H (S K ) Variation, (CV) H No element Mean Max (S K ) Min Mean Max Min 4590 3980 Beam 1A 4259.44590 5692.41 3980 4259.4 1.77 5692.41 4559 Coefficient of Variation, (CV) 1.77 Van, V T A./ Journal of Science and Technology 1.71 in Civil Engineering Beam 2A 4559 4063 4364.7 5583.70 4063 Van, 4364.7 5583.7 1.71 V T A./ Journal of Science and Technology in Civil Engineering Beam 3A 4414 4104 4268.6 3653.40 1.42 Distribution of ultrasonic pulse velocity values at tested points on B 4414 4104 4268.6 Figure3653.4 1.42 Figure Distribution of ultrasonic pulse velocity values at tested points on Beam 1A Figure Distribution of ultrasonic pulse velocity Figure Distribution of ultrasonic pulse velocity Distribution of ultrasonic values2Aat tested points on B values at tested points onFigure Beam 1A values at pulse tested velocity points on Beam Figure Distribution of ultrasonic pulse velocity values at tested points on Beam 2A Distribution of values ultrasonic pulse velocity values Figure DistributionFigure of ultrasonic pulse velocity at tested points on Beam 3A at tested points on B Figure Distribution of ultrasonic pulse velocity values at tested points on Beam 3A 3.2 Homogeneity of concrete in beams 3.2.3.2Homogeneity of concrete in beams Homogeneity of concrete in beams All 10 cross beams in the construction were assessed the homogeneity o All 10 beamsbeams in theby construction were assessed the homogeneity of concrete by measuring Allcross 10 cross in the construction werearea/beam assessed the homogeneity concrete measuring 12 tested Each tested area of has 03 tested points to m 12by tested area/beam Each tested area has 03 tested points to measure the average ultrasonic pulse measuring 12 tested area/beam Each tested area has 03oftested points to measure average ultrasonic pulse velocity the area According to the TCVN 9357:2012 velocity of the area According to TCVN 9357:2012, the grid of array of the tested areas on the cross average ultrasonic pulse of velocity of the area According to TCVN 9357:2012, the grid array of the tested areas on the cross beams is not over 1000 mm and given beams is notofover andon given in Fig.beams Thirty-six tested1000 points/beam measured and the of array the 1000 testedmm areas the cross is not over mm andare given Figure 2.Thirty-six tested points/beam are measured and theinultrasonic pulse veloc ultrasonic pulse velocity values are recorded The homogeneity of concrete in the cross beams were 2.Thirty-six tested points/beam are measured and the ultrasonic pulsein velocity are recorded The homogeneity of concrete the crossvalues beams were assess are recorded The homogeneity of of concrete cross beams wereultrasonic assessed pulse by thevelocity results 24in the coefficient variation (CV) of the average coefficient of variation (CV) the average pulsethat velocity results of of tested areas of (Table 2) The ultrasonic results showed the coefficient variation (CV) of areas (Table 2) The results showed thatresults the coefficient of variation of ultrasonic pulse velocity of all tested areas on(CV) all the elements is lower than pulse velocity results ofdistribution all tested areas on all pulse the elements lowerat than Theon the elements of ultrasonic velocity is values tested2% points Van,V V.T T A./ A./ Journal Journal of of Science Science and Technology in Civil Engineering Van, Engineering Table2 2.Results Results of investigation in cross beams Table of and concrete homogeneity An, of V V.investigation T / Journal of Science Technology in Civil Engineering cross beams Ultrasonic pulse assessed by the coefficient of variation (CV) velocity, of the average ultrasonic pulse velocity results of tested Ultrasonic pulse Name of Coefficient of Name of Coefficient of the coefficient of variation (CV) (of pulse velocity Variance, S KKHHultrasonic ) 22 Noareas (Table 2) The results showed that m/s No m/s element (CV) results element of all tested areas on all the elements is lower than 2% The distribution ofVariation, ultrasonic pulse Variation, (CV) Max Min Mean velocity values at testedMax points on the elements (Figs to 17) also showed how concentrated the Min values of tested points are According to TCVN 9357:2012, concrete in the cross beams is considered Beam1B 1B 4471 4181 4325.1 3237.3 1.32 11homogeneous Beam 4471 4181 1.32 22 Beam2B 2B 4391 4196 4305.1 1011.2 0.74 Beam 4391 4196 0.74 Table Results of investigation of homogeneity and potential internal defects in concrete beams 33 Beam3B 3B Beam Name of No Beamelement 4B Beam 4B 44 55 66 77 88 99 10 10 BeamBeam 5B 1B Beam 5B Beam 2B Beam BeamBeam 6B 3B 6B Beam 4B BeamBeam 7B 5B 7B Beam Beam 6B Beam8B 8B 7B BeamBeam Beam BeamBeam 9B 8B 9B Beam 9B 10Beam BeamBeam 10B10B 10B 4422 4189 4308.2m/s 4422 4189 Ultrasonic pulse velocity, 1950.9 Max 4267 Min 4498 4267 4498 Mean 4382.2 Variance, (S KH )2 1293.6 4471 4136 4181 4426 4426 4136 4325.1 4300.6 3237.3 2790.3 4391 4422 4385 4385 4498 4406 4406 4426 4385 4452 4452 4406 4452 4450 4450 4450 4440 4440 4440 4196 4189 4139 4139 4267 4147 4147 4136 4139 4116 4116 4147 4116 4237 4237 4237 4127 4127 4127 4305.1 4308.2 4264.5 4382.2 4269.4 4300.6 4264.5 4334.9 4269.4 4334.9 4348.2 4348.2 4336.9 4336.9 Figure Distribution of ultrasonic pulse velocity Figure 8.8.Distribution ofBeam ultrasonic Figure Distribution ultrasonic values at tested points onof 1B 1011.2 1950.9 1644.6 1293.6 1590.6 2790.3 1644.6 2660.8 1590.6 2660.8 1155.1 1155.1 2709.6 2709.6 1.03 1.03 Coefficient of Variation, (CV) 0.82 0.82 1.32 1.23 1.23 0.74 1.03 0.95 0.95 0.82 0.93 0.93 1.23 0.95 1.19 1.19 0.93 1.19 0.78 0.78 0.78 1.20 1.20 1.20 Figure Distribution of ultrasonic pulse velocity Figure of ultrasonic ultrasonic Distribution of values at tested points on Beam 2B pulse velocity values at tested tested points points on Beam 2B pulse pulsevelocity velocity values values at at tested tested points points on on Beam Beam 1B 1B 25 Van, V.Van, T A./ of Science and Technology in CivilinEngineering V Journal T A./ Journal of Science and Technology Civil Engineering Van, V.Van, T A./ V.Journal T A./ Journal of Science of Science and Technology and Technology in CivilinEngineering Civil Engineering An, V V T / Journal of Science and Technology in Civil Engineering Figure 10 Distribution of ultrasonic 11 Distribution of ultrasonic Figure 10 Distribution of ultrasonic FigureFigure 11 Distribution of ultrasonic pulsepulse velocity valuesvalues at tested pointspointspulsepulse velocity valuesvalues at tested pointspoints velocity at tested velocity at tested Figure 10 Distribution of ultrasonic pulse velocity Figure 11 Distribution of ultrasonic on Beam 3B 3B on Beam 4B 4B pulse velocity on Beam on Beam values at tested points on Beam 3B values at tested points on 4B FigureFigure 10 Distribution 10 Distribution of ultrasonic of ultrasonic Figure Figure 11 Distribution 11 Distribution of ultrasonic ofBeam ultrasonic pulse pulse velocity velocity valuesvalues at tested at tested pointspoints pulsepulse velocity velocity values values at tested at tested points points on Beam on Beam 3B 3B on Beam on Beam 4B 4B Van, V.Van, T A./ of Science and Technology in CivilinEngineering V.Journal T A./ Journal of Science and Technology Civil Engineering Figure 12 Distribution of ultrasonic pulse velocity Figure 13 Distribution of ultrasonic pulse velocity values tested points on tested points onofBeam 6B Figure 12 Distribution of5B ultrasonic FigureFigure 13.atDistribution ultrasonic Figure 12.atDistribution ofBeam ultrasonic 13.values Distribution of ultrasonic velocity at tested velocity at tested pulsepulse velocity valuesvalues at tested pointspointspulsepulse velocity valuesvalues at tested pointspoints on Beam 5B on Beam 6B on Beam 5B on Beam 6B FigureFigure 12 Distribution 12 Distribution of ultrasonic of ultrasonic Figure Figure 13 Distribution 13 Distribution of ultrasonic of ultrasonic pulse pulse velocity velocity valuesvalues at tested at tested pointspoints pulsepulse velocity velocity values values at tested at tested points points on Beam on Beam 5B 5B on Beam on Beam 6B 6B Figure 14 Distribution of ultrasonic pulse velocity values at tested points on Beam 7B Figure 15 Distribution of ultrasonic pulse velocity values at tested points on Beam 8B FigureFigure 14 Distribution of ultrasonic 15 Distribution of ultrasonic 14 Distribution of ultrasonic Figure Figure 15 Distribution of ultrasonic pulse pulse velocity valuesvalues at tested pointspoints pulsepulse velocity values at tested points velocity at tested velocity values at tested points on Beam 7B on Beam 8B on Beam 7B on Beam 8B 26 8 8 FigureFigure 14 Distribution of ultrasonic 15 Distribution of ultrasonic 14 Distribution of ultrasonic Figure Figure 15 Distribution of ultrasonic pulsepulse velocity valuesvalues at tested pointspoints pulsepulse velocity values at tested points velocity at tested velocity values at tested points on Beam 7B Beam 8B 8B onV.Beam 7B of Science and Technology inon on Beam An, V T / Journal Civil Engineering Figure 16 Distribution of ultrasonic pulse velocity Figure 16.atDistribution ultrasonic Figure 16 Distribution of9B ultrasonic values tested points onofBeam Figure 17 Distribution of ultrasonic pulse velocity Figure 17 Distribution of ultrasonic Figure 17.atDistribution ultrasonic values tested points onofBeam 10B velocity values at tested points velocity values at tested points pulsepulse velocity valuesvalues at tested pointspoints pulsepulse velocity at tested on Beam 10B 10B on Beam on Beam 9B 9B on Beam Conclusions Conclusions Conclusions From the results of this study, it can be concluded that the homogeneity and potential internal theelements results of study, this study, it be can be concluded that the homogeneity and From the results of this it canby concluded the homogeneity defects in From concrete can be assessed Ultrasonic Pulsethat Velocity (UPV) testing and method according to TCVN 9357:2012 The of variation (CV) ultrasonic pulse velocity results potential internal defects in coefficient concrete elements can beofassessed by Ultrasonic Pulse potential internal defects in concrete elements can be assessed by Ultrasonic Pulse of all tested points at all the tested concrete beams is lower than 2% It means that concrete in all Velocity (UPV) testing method according to TCVN 9357:2012 coefficient Velocity (UPV) testing method according to TCVN 9357:2012 The The coefficient of theof elements is uniform and there is no potential internal defect with size over 100 mm in three tested variation of ultrasonic velocity results all tested points all tested the tested variation (CV) (CV) of ultrasonic pulsepulse velocity results of alloftested points at allatthe beams although there are some honeycombs, surface cracks and cold joints appearing on the surface concrete is lower than It2% It means that concrete allelements the elements is uniform concrete beamsbeams is lower than 2% means that concrete in allinthe is uniform and there no potential internal size over 100 in mmthree in three beams and there is no ispotential internal defectdefect with with size over 100 mm testedtested beams Acknowledgments although there are some honeycombs, surface cracks and cold joints appearing on although there are some honeycombs, surface cracks and cold joints appearing on the the The author would like to thank for the support in UPV testing in situ from Tran Duc Trung, surface surface Nguyen Van Binh and Tran Van Kien at Laboratory for Testing and Studying of Building Materials National University of Civil Engineering References 9 [1] IAEA (2002) Guidebook on non-destructive testing of concrete structures Vienna, IAEA–TCS–17, ISSN 1018–5518 [2] ASTM C597-02 (2002) Standard test method for pulse velocity through concrete [3] Saint-Pierre, F., Philibert, A., Giroux, B., Rivard, P (2016) Concrete quality designation based on ultrasonic pulse velocity Construction and Building Materials, 125:1022–1027 [4] TCVN 9357:2012 (2012) Normal concrete - Nondestructive methods - Assessment of concrete quality using ultrasonic pulse velocity [5] BS EN 12504-4:2004 (2004) Testing concrete - Part 4: Determination of ultrasonic pulse velocity [6] Lin, Y C., Lin, Y., Chan, C C (2016) Use of ultrasonic pulse velocity to estimate strength of concrete at various ages Magazine of Concrete Research, 68(14):739749 [7] Komlos, K., Popovics, S., Năurnbergerovỏ, T., Babal, B., Popovics, J S (1996) Ultrasonic pulse velocity test of concrete properties as specified in various standards Cement and Concrete Composites, 18(5): 357–364 [8] Bungey, J H (1980) The validity of ultrasonic pulse velocity testing of in-place concrete for strength NDT International, 13(6):296–300 27 ... coefficient of variation (CV) velocity, of the average ultrasonic pulse velocity results of tested Ultrasonic pulse Name of Coefficient of Name of Coefficient of the coefficient of variation (CV) (of pulse. .. Calculation of the coefficient of variation (CV) of pulse velocity results The homogeneity of concrete beams is evaluated through the coefficient of variation of pulse velocity results The coefficient of. .. velocity of the area According to TCVN 9357:2012, the grid of array of the tested areas on the cross average ultrasonic pulse of velocity of the area According to TCVN 9357:2012, the grid array of the