Research ArticleEffect of Chlorides on Conductivity and Dielectric Constant inHardened Cement Mortar NDT for Durability Evaluation
Sunkook Kim1 Joowon Kang2 Sang-Hyo Lee3 and Yong Han Ahn3
1Multi-Functional NanoBio Electronics Lab Department of Electronics and Radio Engineering Kyung Hee UniversityGyeonggi 446-701 Republic of Korea2School of Architecture Yeungnam University 280 Daehak-ro Gyeongbuk 712-749 Republic of Korea3Division of Architecture and Architectural Engineering Hanyang University-ERICA Gyeonggi 15588 Republic of Korea
Correspondence should be addressed to Yong Han Ahn yonghan77gmailcom
Received 22 February 2016 Accepted 27 April 2016
Academic Editor Yuyin Wang
Copyright copy 2016 Sunkook Kim et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Dielectric constant and conductivity the so-called EM properties (electromagnetic) are widely adopted for NDT (NondestructiveTechnique) in order to detect damage or evaluate performance of concrete without damage to existing RC (reinforced concrete)Among deteriorating agents chloride ion is considered as one of the most critical threats due to rapid penetration and direct effecton steel corrosion In the work cement mortar samples with 3wc (water-to-cement) ratios and 4 levels of chloride addition areconsidered Conductivity and dielectric constant aremeasured in the normal frequency rangeThey increasewith strength ofmortarand more chloride ions due to denser pore formation Furthermore the behaviors of measured EM property are investigated withcarbonation velocity and strength which shows an attempt of application to durability evaluation through EMmeasurement
1 Introduction
Nondestructive Techniques (NDT) are widely used for eval-uation of physical and durability performance in concretestructures Among various techniques the techniques usingelectromagnetic (EM) properties are increasingly applied asan alternative for performance evaluation in RC (reinforcedconcrete) structure [1 2] Several researchers have focused onEM properties in cement-based materials These researchescan be classified into several categories Many studies relatedto the characterization of EM properties in cement-basedmaterials have been performed [3ndash5] They cover not onlyOrdinary Portland Cement (OPC) but also cement-basedmatrix with mineral admixtures such as fly ash [6ndash9] Someof the studies focused on the variations of EM properties inwide frequency range [3] Recently EMproperties are appliedfor durability evaluation in concrete such as permeabilityand the diffusion coefficient [10ndash12] Usually the modelswhich are made up of porosity solid paste and saturation ofwater can provide dielectric constant and loss factor throughcomplex equations [2 13ndash15] The models have been applied
to the deteriorated RC structures considering permittivity insaline water The evaluation techniques like monitoring andcondition assessment are also proposed through the uniquecharacteristics of EM measurement [15ndash18] Recently NDTtechniques using EM properties are applied to the evaluationof delamination in composite member repaired with glassfiber reinforced plastic (GFRP) [19ndash21]
The porosity and saturation in concrete have a great effectnot only on the EM properties but also on the durabilitycharacteristics in concrete During hydration process poresare naturally generated in the concrete and the amount ofpores (porosity) has a close relationship with the structuraland durability performance [22ndash24] As porosity plays animportant role in intrusion of deteriorating agent it ismainly considered to explain themechanism of diffusion andpermeation of ion [25ndash28]
This work is focused on the characterization of EM prop-erties in cement mortar with chloride ionThe measured EMproperties are compared with typical concrete performancelike carbonation velocity and strength In the practical pointof view the characteristics of EM properties observed in
Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2016 Article ID 6018476 9 pageshttpdxdoiorg10115520166018476
2 Advances in Materials Science and Engineering
Table 1 Influencing parameters for EM properties
Type Parameters Characteristics of EM properties
Interior conditionWater amount (i) Strongly affect dielectric constant and conductivity
(ii) Increase with larger amount of waterPorosity (i) Decrease with larger porosity
Chloride ion (i) Greatly increase with larger amount of chloride in water
Exterior condition Temperature (i) Increase with higher temperature (lt10ndash12GHz)Humidity (i) Increase with higher humidity
Measurement condition Frequency (i) Dielectric constant decrease with higher frequency(ii) Conductivity increase with higher frequency
Measuring surface (i) Increase with larger contact surface
the work can be utilized for not only strength evaluation butalso durability evaluation
2 Conductivity and Dielectric Constant
21 Conductivity and Dielectric Constant in Porous Media[3 20] All materials have a unique set of EM propertiesNonmetallic materials like concrete can be characterized bytwo independent electromagnetic properties (1) the complexpermittivity (120576lowast) and (2) the complex permeability (120583lowast) [3]Since most of the dielectric materials such as concrete arenonmagnetic the permeability 120583lowast of the dielectric materialsis very close to that of free space (120583
0= 4120587 times 10
minus7
henriesmeter) Thus it is enough to focus on the complexpermittivity 120576lowast defined by [3 20]
where 1205761015840 and 12057610158401015840 are the real and imaginary parts of thecomplex permittivity and 119895 = radicminus1 Equation (1) can berewritten as (2) when considering the permittivity in freespace 120576
0(8854times10minus12 faradm) Equation (2) can be rewritten
as (3) which is dimensionless [3 20]
120576lowast
1205760
=
1205761015840
1205760
minus 119895
12057610158401015840
1205760
(2)
120576lowast
119903= 1205761015840
119903minus 11989512057610158401015840
119903 (3)
where 120576lowast119903is the relative complex permittivity 1205761015840
119903and 12057610158401015840119903are the
real and imaginary parts of the relative complex permittivityrespectively
The real part of the relative complex permittivity 1205761015840119903 also
known as the dielectric constant is a depiction of how muchenergy can be stored in a material from an external electricfieldThe imaginary part of the relative complex permittivity12057610158401015840
119903 represents how dissipative a material is to an external
electric field This value can be simply referred to the lossfactor [3 22] The equivalent conductivity 120590 (mhosm) canbe written in terms of the imaginary part of the complexpermittivity 12057610158401015840 as shown in
120590 = 12057610158401015840120596 = (120576
1015840
1199031205760tan 120575) (2120587119891) (4)
where 120596 is angular frequency of EM wave (radsec) tan 120575 isloss tangent (the ratio of energy lost to energy stored in amaterial) and 119891 is the number of cycles per second (Hz)These EM properties are not constant and are dependentupon the frequency temperature moisture content chloridecontent and concrete mix constituents [2ndash4]
The influencing parameters can be summarized as Table 1in the view of porous media Exterior conditions like temper-ature and humidity and the measurement condition such asthe range of frequency also have effects on the EMproperties
3 Conductivity and Dielectric Constant inConcrete
31 Experimental Program
311 Measurement of Dielectric Constant and ConductivityThe OPC mortars with 3 different wc ratios (045 055 and065) are prepared For each case of wc ratios 4 differentchloride contents (00 06 12 and 36 kgm3) are addedat the mix stage The chloride ion within 12sim36 kgm3 ismeaningful since chloride content of 12 kgm3 is regardedas a critical threshold which can cause steel corrosion inconcrete Thus a total of 12 mix conditions are preparedfor the comparative investigation Each sample was keptin air-curing condition for 4 weeks after mixing The mixproportions for OPC mortar are listed in Table 2
For the test cement mortar is used for EM prop-erties in order to prevent a measurement error due todirect contact on the coarse aggregate Cylindrical samples
Advances in Materials Science and Engineering 3
Figure 1 Setup for EM measurement
(100mm times 200mm) are made for the compressive strengthtest and the disk type specimens (100mm diameter times 20mmthickness) are prepared for EM property measurement Aconcrete depth of over 5mm was reported to have insignif-icant effect from reflected microwaves [18]
Themeasurement setup is shown in Figure 1The packagefor EMmeasurement has a dielectric probe kit which includesanalyzing software an open ended coaxial probe (OECP)a network analyzer and a laptop computer Conductivityand dielectric constant are measured by placing the probein contact with a flat face of a solid surface The networkanalyzer sends and receives microwaves through the probeover a frequency range of 02 GHz to 20GHz with an intervalof 04GHz
For the calibration of the test system using the OECPpredefined property values for the reflected signal should beprepared over themeasuring frequency range [29] In the testthe calibration is performed in the air namely free space andin the water with 25∘C prior to the measurement
312 Compressive Strength Compressive strength tests areperformed referring to Korea Standard [30] Trifold cementmortar samples with 100mm of diameter and 200mm ofheight are prepared The samples have been kept for 4 weeksin the same curing condition and compressive strength testwas performed after 1-day exposure to room condition
313 Carbonation Test After 4 weeks of curing the sampleswere kept in the condition of relative humidity at 60 and25∘C temperature for 2 weeks And then the accelerated car-bonation test is performed for 8 weeks referring to the KoreaStandard [31 32] For 1-dimensional accelerated carbonationtest the sides of specimens are coated with epoxy except fortop surface The conditions for accelerated carbonation testare listed in Table 3 The photos for compressive strength testand carbonation test are shown in Figure 2 The carbonationtest is performed on cement mortar samples (50mm ofthickness) without chloride contents
32 Test Results
321 Measurement of Dielectric Constant and ConductivityIn the test the measurements from OECP are repeatedly
Table 3 Conditions for accelerated carbonation test
Temperature (∘C) Relative humidity () CO2concentration ()
20 plusmn 2 60 plusmn 5 5 plusmn 02
(a) Compressive strength
(b) Samples in the carbonation chamber
Figure 2 Photos for compressive strength and carbonation test
performed 10 times for each disk samples and the values ofdielectric constant and conductivity are averaged The rangeof frequency is 02sim20GHz and several points of 02 5 10 15and 20GHz are selected and measured in a room conditionwith 60 relative humidity and 20sim22∘C temperature Themeasured results with different wc ratios are plotted inFigures 3sim5
As shown in Figures 3sim5 conductivity becomes largerand dielectric constant decreases with the increase of fre-quency The changing behavior with frequency is consistentwith the previous researches [18 21] With the smaller poresmortar surface has more contact area with probe and thiscauses higher conductive and dielectric constant The largeraddition of NaCl causes more dense porosity [33 34]
322 Compressive Strength Results The compressivestrength shows a close relationship with wc ratios incement mortar but it shows insignificant variations withchloride amount included in the test The drop of pH due
4 Advances in Materials Science and Engineering
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 3 Conductivity and dielectric constant (wc 045)
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 4 Conductivity and dielectric constant (wc 055)
to the addition of calcium chloride (CaCl2) can accelerate
the hydration activity so that the compressive strengthin early-aged stage rapidly increases [33] Concrete withsodium chloride (NaCl) is reported to show little change inhydration activity but significant effects on drying shrinkagedue to the altered pore distribution [34] The test resultsof compressive strength are shown in Figure 6 where onecan indicate that the compressive strength has no clearrelationship with the chloride contents The similar resultsrelated to the compressive strength can be found in previousresearch [24] Traditional strength reduction is found inFigure 6 with increasing wc ratio
323 Accelerated Carbonation Test Result It is also foundthat concrete with low wc ratio shows small carbonationdepth since it has low diffusion coefficient of CO
2and
large amount of hydrates such as CHS and Ca(OH)2which
have potential to keep high pH in pore water [26 35]Carbonation velocity is usually adopted for carbonationresistance based on the assumption that carbonation depthhas linear relationship with square root of exposed time [3637] In Figure 7 the results of accelerated carbonation test areplotted which shows slower carbonation progress with lowerwc ratio Carbonation velocity through regression analysiscan be summarized in Table 4
4 Characteristics of EM Properties forDurability Evaluation
41 EM Characteristics and wc Ratios For the purpose ofcomparison of the results EM properties corresponding to
Advances in Materials Science and Engineering 5
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 5 Conductivity and dielectric constant (wc 065)
Figure 6 Compressive strength with different chloride contents
5sim20GHz range are respectively averaged as one value toobtain parameter Each averaged value of conductivity anddielectric constant is plotted in Figure 8 with wc ratiosconsidering chloride contents
Typically porosity in cement mortar has effect on theconductivity and dielectric constant In cement mortarporosity becomes smaller with decrease in wc ratios due toabundant hydrates and the reduced porosity causes higherEMproperties [22 23 38] Usually permittivity of cement gel
0
1
2
3
4
5
0 2 4 6 8 10
Carb
onat
ion
dept
h (m
m)
Period (week)
wc 055wc 065
wc 045
Figure 7 Carbonation depth with exposed period
is in the level of 5sim10 and this is larger than that of air (=10)[2 13] One can also indicate that for the samples containingthe samewc ratiosmore chloride content leads to higher EMproperties due to reduced porosity
42 EM Characteristics and Compressive Strength As inSection 322 the addition of NaCl cannot cause a big changein strength The averaged EM properties can compare theresults of compressive strength as in Figure 9 EM properties(dielectric constant and conductivity) without chloride con-tent are used for the comparison with the results since theyare varying significantly with chloride addition Compressivestrength is reported to have linear relationship with wc ratio[22] As shown in Figure 8 EM properties without chloridecontent have linear relationship with wc ratio with highdetermination coefficient (1198772) so that linear relationship
6 Advances in Materials Science and Engineering
04
06
08
1
12
045 05 055 06 065
Aver
aged
cond
uctiv
ity (S
m)
wc ratio
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Averaged conductivity
3
4
5
6
7
045 05 055 06 065
Aver
aged
die
lect
ric co
nsta
nt
wc ratio
36kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Averaged dielectric constant
Figure 8 Averaged EM properties with different wc ratios and chloride contents
0
10
20
30
40
50
60
04 05 06 07 08 09
Com
pres
sive s
treng
th (M
Pa)
Averaged conductivity (Sm)
y = 66107x minus 76805
R2 = 09861
(a) Conductivity and strength
0
10
20
30
40
50
60
3 4 5 6
Com
pres
sive s
treng
th (M
Pa)
Averaged dielectric constant
y = 14637x minus 28161
R2 = 09868
(b) Dielectric constant and strength
Figure 9 EM properties and compressive strength
is found between EM properties and strength as shown inFigure 9
43 EMCharacteristics and Carbonation Velocity For porousmedia the diffusion mechanism in concrete is also closelyrelated with porosity characteristics [26ndash28] In Figure 10 theaveraged EM properties are compared with the carbonationvelocity obtained from the accelerated carbonation test Theresults are only for the case without chloride contents
The carbonation velocity is observed in linear proportionto the wc ratios and the trend can be found in conventionalequations for the prediction of carbonation depth [26 36]For the cement mortar without chloride amount it is foundthat that the averaged EM properties decrease with the highcarbonation velocity which is consistent with the resultsin high wc and low compressive strength Considering
the results in strength and carbonation depth the lower wcratio in cement mortar causes larger content of hydrateswhich yields high strength and low porosity The densestructure shows relatively high EM properties With increas-ing strength due to larger hydrates and lower porosity theresistance to carbonation also increases due to low CO
2
diffusion and more carbonatable materialsmdashCa(OH)2 In
Figure 10 higher carbonation velocity which means coarsestructure shows lower conductivity and electric constant
44 EM Characteristics and Chloride Content in Cement Mor-tar In the water-submerged condition chloride ion does notsignificantly affect dielectric constant however loss factorwhich causes attenuation is greatly changed due to increasein ohmic conductivity [3] In cement mortar both conduc-tivity and dielectric constant increase with larger amount
Advances in Materials Science and Engineering 7
0
02
04
06
08
1
0
1
2
3
4
5
6
05 06 07 08 09 1 11 12
Con
duct
ivity
(Sm
)
Die
lect
ric co
nsta
nt
DielectricConductivity
y = minus32795x + 71144
R2 = 09985
y = minus07258x + 12651
R2 = 09981
Carbonation velocity (mmweek05)
Reg (conductivity)Reg (dielectric constant)
Figure 10 Relationship between carbonation velocity and EM properties
04
05
06
07
08
09
1
11
0 1 2 3 4
Con
duct
ivity
(Sm
)
wc 065wc 055wc 045
NaCl content (kgm3)
(a) Conductivity variation
3
35
4
45
5
55
6
0 1 2 3 4
Die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl content (kgm3)
(b) Dielectric constant
Figure 11 Effect of chloride contents on conductivity and dielectric constant
of chloride amount It is because the chloride ion in initialmix causes smaller pore distribution in OPC mortar andsodium ion dissolved in pore water can increase conductivityand dielectric constant In Figure 11 the effect of chlorideon EM properties is plotted with varying chloride contentsThe result in higher wc ratio shows more rapid increase inboth conductivity and dielectric constant because the coarsepore structure in OPC mortar with higher wc ratio is moreaffected by chloride ion which can cause the densification ofpore structure
The regression analysis is performed with increasingratios to noncontaminated OPC mortar and is plotted inFigure 12 The linear relationships between EM propertiesand chloride content are summarized in Table 5 In Table 5the gradient of slope means the effect of chloride ion on
EM properties Lower wc ratio shows higher strength inconcrete and lower dependency of chloride ion howevermix conditions with high wc ratio (065) show clear increasein chloride effect When chloride ion is added to 36 kgm3conductivity and dielectric constant increase to 173 and134 respectivelyThe relationship shows clear linearity withhigh determination coefficient over 09 which strongly showsapplicability as NDT for evaluation of chloride contamina-tion for cement mortar
5 Concluding Remark
Among various nondestructive testing (NDT) techniqueselectromagnetic properties of conductivity and dielectricconstant are attempted for an evaluation of chloride effect
8 Advances in Materials Science and Engineering
1
12
14
16
18
0 1 2 3 4
Nor
mal
ized
cond
uctiv
ity
NaCl content (kgm3)
wc 065wc 055wc 045
(a) Normalized conductivity
1
11
12
13
14
0 1 2 3 4
Nor
mal
ized
die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl (kgm3)
(b) Normalized dielectric constant
Figure 12 Increasing ratios of EM properties with chloride contents
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
the work can be utilized for not only strength evaluation butalso durability evaluation
2 Conductivity and Dielectric Constant
21 Conductivity and Dielectric Constant in Porous Media[3 20] All materials have a unique set of EM propertiesNonmetallic materials like concrete can be characterized bytwo independent electromagnetic properties (1) the complexpermittivity (120576lowast) and (2) the complex permeability (120583lowast) [3]Since most of the dielectric materials such as concrete arenonmagnetic the permeability 120583lowast of the dielectric materialsis very close to that of free space (120583
0= 4120587 times 10
minus7
henriesmeter) Thus it is enough to focus on the complexpermittivity 120576lowast defined by [3 20]
where 1205761015840 and 12057610158401015840 are the real and imaginary parts of thecomplex permittivity and 119895 = radicminus1 Equation (1) can berewritten as (2) when considering the permittivity in freespace 120576
0(8854times10minus12 faradm) Equation (2) can be rewritten
as (3) which is dimensionless [3 20]
120576lowast
1205760
=
1205761015840
1205760
minus 119895
12057610158401015840
1205760
(2)
120576lowast
119903= 1205761015840
119903minus 11989512057610158401015840
119903 (3)
where 120576lowast119903is the relative complex permittivity 1205761015840
119903and 12057610158401015840119903are the
real and imaginary parts of the relative complex permittivityrespectively
The real part of the relative complex permittivity 1205761015840119903 also
known as the dielectric constant is a depiction of how muchenergy can be stored in a material from an external electricfieldThe imaginary part of the relative complex permittivity12057610158401015840
119903 represents how dissipative a material is to an external
electric field This value can be simply referred to the lossfactor [3 22] The equivalent conductivity 120590 (mhosm) canbe written in terms of the imaginary part of the complexpermittivity 12057610158401015840 as shown in
120590 = 12057610158401015840120596 = (120576
1015840
1199031205760tan 120575) (2120587119891) (4)
where 120596 is angular frequency of EM wave (radsec) tan 120575 isloss tangent (the ratio of energy lost to energy stored in amaterial) and 119891 is the number of cycles per second (Hz)These EM properties are not constant and are dependentupon the frequency temperature moisture content chloridecontent and concrete mix constituents [2ndash4]
The influencing parameters can be summarized as Table 1in the view of porous media Exterior conditions like temper-ature and humidity and the measurement condition such asthe range of frequency also have effects on the EMproperties
3 Conductivity and Dielectric Constant inConcrete
31 Experimental Program
311 Measurement of Dielectric Constant and ConductivityThe OPC mortars with 3 different wc ratios (045 055 and065) are prepared For each case of wc ratios 4 differentchloride contents (00 06 12 and 36 kgm3) are addedat the mix stage The chloride ion within 12sim36 kgm3 ismeaningful since chloride content of 12 kgm3 is regardedas a critical threshold which can cause steel corrosion inconcrete Thus a total of 12 mix conditions are preparedfor the comparative investigation Each sample was keptin air-curing condition for 4 weeks after mixing The mixproportions for OPC mortar are listed in Table 2
For the test cement mortar is used for EM prop-erties in order to prevent a measurement error due todirect contact on the coarse aggregate Cylindrical samples
Advances in Materials Science and Engineering 3
Figure 1 Setup for EM measurement
(100mm times 200mm) are made for the compressive strengthtest and the disk type specimens (100mm diameter times 20mmthickness) are prepared for EM property measurement Aconcrete depth of over 5mm was reported to have insignif-icant effect from reflected microwaves [18]
Themeasurement setup is shown in Figure 1The packagefor EMmeasurement has a dielectric probe kit which includesanalyzing software an open ended coaxial probe (OECP)a network analyzer and a laptop computer Conductivityand dielectric constant are measured by placing the probein contact with a flat face of a solid surface The networkanalyzer sends and receives microwaves through the probeover a frequency range of 02 GHz to 20GHz with an intervalof 04GHz
For the calibration of the test system using the OECPpredefined property values for the reflected signal should beprepared over themeasuring frequency range [29] In the testthe calibration is performed in the air namely free space andin the water with 25∘C prior to the measurement
312 Compressive Strength Compressive strength tests areperformed referring to Korea Standard [30] Trifold cementmortar samples with 100mm of diameter and 200mm ofheight are prepared The samples have been kept for 4 weeksin the same curing condition and compressive strength testwas performed after 1-day exposure to room condition
313 Carbonation Test After 4 weeks of curing the sampleswere kept in the condition of relative humidity at 60 and25∘C temperature for 2 weeks And then the accelerated car-bonation test is performed for 8 weeks referring to the KoreaStandard [31 32] For 1-dimensional accelerated carbonationtest the sides of specimens are coated with epoxy except fortop surface The conditions for accelerated carbonation testare listed in Table 3 The photos for compressive strength testand carbonation test are shown in Figure 2 The carbonationtest is performed on cement mortar samples (50mm ofthickness) without chloride contents
32 Test Results
321 Measurement of Dielectric Constant and ConductivityIn the test the measurements from OECP are repeatedly
Table 3 Conditions for accelerated carbonation test
Temperature (∘C) Relative humidity () CO2concentration ()
20 plusmn 2 60 plusmn 5 5 plusmn 02
(a) Compressive strength
(b) Samples in the carbonation chamber
Figure 2 Photos for compressive strength and carbonation test
performed 10 times for each disk samples and the values ofdielectric constant and conductivity are averaged The rangeof frequency is 02sim20GHz and several points of 02 5 10 15and 20GHz are selected and measured in a room conditionwith 60 relative humidity and 20sim22∘C temperature Themeasured results with different wc ratios are plotted inFigures 3sim5
As shown in Figures 3sim5 conductivity becomes largerand dielectric constant decreases with the increase of fre-quency The changing behavior with frequency is consistentwith the previous researches [18 21] With the smaller poresmortar surface has more contact area with probe and thiscauses higher conductive and dielectric constant The largeraddition of NaCl causes more dense porosity [33 34]
322 Compressive Strength Results The compressivestrength shows a close relationship with wc ratios incement mortar but it shows insignificant variations withchloride amount included in the test The drop of pH due
4 Advances in Materials Science and Engineering
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 3 Conductivity and dielectric constant (wc 045)
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 4 Conductivity and dielectric constant (wc 055)
to the addition of calcium chloride (CaCl2) can accelerate
the hydration activity so that the compressive strengthin early-aged stage rapidly increases [33] Concrete withsodium chloride (NaCl) is reported to show little change inhydration activity but significant effects on drying shrinkagedue to the altered pore distribution [34] The test resultsof compressive strength are shown in Figure 6 where onecan indicate that the compressive strength has no clearrelationship with the chloride contents The similar resultsrelated to the compressive strength can be found in previousresearch [24] Traditional strength reduction is found inFigure 6 with increasing wc ratio
323 Accelerated Carbonation Test Result It is also foundthat concrete with low wc ratio shows small carbonationdepth since it has low diffusion coefficient of CO
2and
large amount of hydrates such as CHS and Ca(OH)2which
have potential to keep high pH in pore water [26 35]Carbonation velocity is usually adopted for carbonationresistance based on the assumption that carbonation depthhas linear relationship with square root of exposed time [3637] In Figure 7 the results of accelerated carbonation test areplotted which shows slower carbonation progress with lowerwc ratio Carbonation velocity through regression analysiscan be summarized in Table 4
4 Characteristics of EM Properties forDurability Evaluation
41 EM Characteristics and wc Ratios For the purpose ofcomparison of the results EM properties corresponding to
Advances in Materials Science and Engineering 5
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 5 Conductivity and dielectric constant (wc 065)
Figure 6 Compressive strength with different chloride contents
5sim20GHz range are respectively averaged as one value toobtain parameter Each averaged value of conductivity anddielectric constant is plotted in Figure 8 with wc ratiosconsidering chloride contents
Typically porosity in cement mortar has effect on theconductivity and dielectric constant In cement mortarporosity becomes smaller with decrease in wc ratios due toabundant hydrates and the reduced porosity causes higherEMproperties [22 23 38] Usually permittivity of cement gel
0
1
2
3
4
5
0 2 4 6 8 10
Carb
onat
ion
dept
h (m
m)
Period (week)
wc 055wc 065
wc 045
Figure 7 Carbonation depth with exposed period
is in the level of 5sim10 and this is larger than that of air (=10)[2 13] One can also indicate that for the samples containingthe samewc ratiosmore chloride content leads to higher EMproperties due to reduced porosity
42 EM Characteristics and Compressive Strength As inSection 322 the addition of NaCl cannot cause a big changein strength The averaged EM properties can compare theresults of compressive strength as in Figure 9 EM properties(dielectric constant and conductivity) without chloride con-tent are used for the comparison with the results since theyare varying significantly with chloride addition Compressivestrength is reported to have linear relationship with wc ratio[22] As shown in Figure 8 EM properties without chloridecontent have linear relationship with wc ratio with highdetermination coefficient (1198772) so that linear relationship
6 Advances in Materials Science and Engineering
04
06
08
1
12
045 05 055 06 065
Aver
aged
cond
uctiv
ity (S
m)
wc ratio
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Averaged conductivity
3
4
5
6
7
045 05 055 06 065
Aver
aged
die
lect
ric co
nsta
nt
wc ratio
36kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Averaged dielectric constant
Figure 8 Averaged EM properties with different wc ratios and chloride contents
0
10
20
30
40
50
60
04 05 06 07 08 09
Com
pres
sive s
treng
th (M
Pa)
Averaged conductivity (Sm)
y = 66107x minus 76805
R2 = 09861
(a) Conductivity and strength
0
10
20
30
40
50
60
3 4 5 6
Com
pres
sive s
treng
th (M
Pa)
Averaged dielectric constant
y = 14637x minus 28161
R2 = 09868
(b) Dielectric constant and strength
Figure 9 EM properties and compressive strength
is found between EM properties and strength as shown inFigure 9
43 EMCharacteristics and Carbonation Velocity For porousmedia the diffusion mechanism in concrete is also closelyrelated with porosity characteristics [26ndash28] In Figure 10 theaveraged EM properties are compared with the carbonationvelocity obtained from the accelerated carbonation test Theresults are only for the case without chloride contents
The carbonation velocity is observed in linear proportionto the wc ratios and the trend can be found in conventionalequations for the prediction of carbonation depth [26 36]For the cement mortar without chloride amount it is foundthat that the averaged EM properties decrease with the highcarbonation velocity which is consistent with the resultsin high wc and low compressive strength Considering
the results in strength and carbonation depth the lower wcratio in cement mortar causes larger content of hydrateswhich yields high strength and low porosity The densestructure shows relatively high EM properties With increas-ing strength due to larger hydrates and lower porosity theresistance to carbonation also increases due to low CO
2
diffusion and more carbonatable materialsmdashCa(OH)2 In
Figure 10 higher carbonation velocity which means coarsestructure shows lower conductivity and electric constant
44 EM Characteristics and Chloride Content in Cement Mor-tar In the water-submerged condition chloride ion does notsignificantly affect dielectric constant however loss factorwhich causes attenuation is greatly changed due to increasein ohmic conductivity [3] In cement mortar both conduc-tivity and dielectric constant increase with larger amount
Advances in Materials Science and Engineering 7
0
02
04
06
08
1
0
1
2
3
4
5
6
05 06 07 08 09 1 11 12
Con
duct
ivity
(Sm
)
Die
lect
ric co
nsta
nt
DielectricConductivity
y = minus32795x + 71144
R2 = 09985
y = minus07258x + 12651
R2 = 09981
Carbonation velocity (mmweek05)
Reg (conductivity)Reg (dielectric constant)
Figure 10 Relationship between carbonation velocity and EM properties
04
05
06
07
08
09
1
11
0 1 2 3 4
Con
duct
ivity
(Sm
)
wc 065wc 055wc 045
NaCl content (kgm3)
(a) Conductivity variation
3
35
4
45
5
55
6
0 1 2 3 4
Die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl content (kgm3)
(b) Dielectric constant
Figure 11 Effect of chloride contents on conductivity and dielectric constant
of chloride amount It is because the chloride ion in initialmix causes smaller pore distribution in OPC mortar andsodium ion dissolved in pore water can increase conductivityand dielectric constant In Figure 11 the effect of chlorideon EM properties is plotted with varying chloride contentsThe result in higher wc ratio shows more rapid increase inboth conductivity and dielectric constant because the coarsepore structure in OPC mortar with higher wc ratio is moreaffected by chloride ion which can cause the densification ofpore structure
The regression analysis is performed with increasingratios to noncontaminated OPC mortar and is plotted inFigure 12 The linear relationships between EM propertiesand chloride content are summarized in Table 5 In Table 5the gradient of slope means the effect of chloride ion on
EM properties Lower wc ratio shows higher strength inconcrete and lower dependency of chloride ion howevermix conditions with high wc ratio (065) show clear increasein chloride effect When chloride ion is added to 36 kgm3conductivity and dielectric constant increase to 173 and134 respectivelyThe relationship shows clear linearity withhigh determination coefficient over 09 which strongly showsapplicability as NDT for evaluation of chloride contamina-tion for cement mortar
5 Concluding Remark
Among various nondestructive testing (NDT) techniqueselectromagnetic properties of conductivity and dielectricconstant are attempted for an evaluation of chloride effect
8 Advances in Materials Science and Engineering
1
12
14
16
18
0 1 2 3 4
Nor
mal
ized
cond
uctiv
ity
NaCl content (kgm3)
wc 065wc 055wc 045
(a) Normalized conductivity
1
11
12
13
14
0 1 2 3 4
Nor
mal
ized
die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl (kgm3)
(b) Normalized dielectric constant
Figure 12 Increasing ratios of EM properties with chloride contents
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
(100mm times 200mm) are made for the compressive strengthtest and the disk type specimens (100mm diameter times 20mmthickness) are prepared for EM property measurement Aconcrete depth of over 5mm was reported to have insignif-icant effect from reflected microwaves [18]
Themeasurement setup is shown in Figure 1The packagefor EMmeasurement has a dielectric probe kit which includesanalyzing software an open ended coaxial probe (OECP)a network analyzer and a laptop computer Conductivityand dielectric constant are measured by placing the probein contact with a flat face of a solid surface The networkanalyzer sends and receives microwaves through the probeover a frequency range of 02 GHz to 20GHz with an intervalof 04GHz
For the calibration of the test system using the OECPpredefined property values for the reflected signal should beprepared over themeasuring frequency range [29] In the testthe calibration is performed in the air namely free space andin the water with 25∘C prior to the measurement
312 Compressive Strength Compressive strength tests areperformed referring to Korea Standard [30] Trifold cementmortar samples with 100mm of diameter and 200mm ofheight are prepared The samples have been kept for 4 weeksin the same curing condition and compressive strength testwas performed after 1-day exposure to room condition
313 Carbonation Test After 4 weeks of curing the sampleswere kept in the condition of relative humidity at 60 and25∘C temperature for 2 weeks And then the accelerated car-bonation test is performed for 8 weeks referring to the KoreaStandard [31 32] For 1-dimensional accelerated carbonationtest the sides of specimens are coated with epoxy except fortop surface The conditions for accelerated carbonation testare listed in Table 3 The photos for compressive strength testand carbonation test are shown in Figure 2 The carbonationtest is performed on cement mortar samples (50mm ofthickness) without chloride contents
32 Test Results
321 Measurement of Dielectric Constant and ConductivityIn the test the measurements from OECP are repeatedly
Table 3 Conditions for accelerated carbonation test
Temperature (∘C) Relative humidity () CO2concentration ()
20 plusmn 2 60 plusmn 5 5 plusmn 02
(a) Compressive strength
(b) Samples in the carbonation chamber
Figure 2 Photos for compressive strength and carbonation test
performed 10 times for each disk samples and the values ofdielectric constant and conductivity are averaged The rangeof frequency is 02sim20GHz and several points of 02 5 10 15and 20GHz are selected and measured in a room conditionwith 60 relative humidity and 20sim22∘C temperature Themeasured results with different wc ratios are plotted inFigures 3sim5
As shown in Figures 3sim5 conductivity becomes largerand dielectric constant decreases with the increase of fre-quency The changing behavior with frequency is consistentwith the previous researches [18 21] With the smaller poresmortar surface has more contact area with probe and thiscauses higher conductive and dielectric constant The largeraddition of NaCl causes more dense porosity [33 34]
322 Compressive Strength Results The compressivestrength shows a close relationship with wc ratios incement mortar but it shows insignificant variations withchloride amount included in the test The drop of pH due
4 Advances in Materials Science and Engineering
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 3 Conductivity and dielectric constant (wc 045)
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 4 Conductivity and dielectric constant (wc 055)
to the addition of calcium chloride (CaCl2) can accelerate
the hydration activity so that the compressive strengthin early-aged stage rapidly increases [33] Concrete withsodium chloride (NaCl) is reported to show little change inhydration activity but significant effects on drying shrinkagedue to the altered pore distribution [34] The test resultsof compressive strength are shown in Figure 6 where onecan indicate that the compressive strength has no clearrelationship with the chloride contents The similar resultsrelated to the compressive strength can be found in previousresearch [24] Traditional strength reduction is found inFigure 6 with increasing wc ratio
323 Accelerated Carbonation Test Result It is also foundthat concrete with low wc ratio shows small carbonationdepth since it has low diffusion coefficient of CO
2and
large amount of hydrates such as CHS and Ca(OH)2which
have potential to keep high pH in pore water [26 35]Carbonation velocity is usually adopted for carbonationresistance based on the assumption that carbonation depthhas linear relationship with square root of exposed time [3637] In Figure 7 the results of accelerated carbonation test areplotted which shows slower carbonation progress with lowerwc ratio Carbonation velocity through regression analysiscan be summarized in Table 4
4 Characteristics of EM Properties forDurability Evaluation
41 EM Characteristics and wc Ratios For the purpose ofcomparison of the results EM properties corresponding to
Advances in Materials Science and Engineering 5
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 5 Conductivity and dielectric constant (wc 065)
Figure 6 Compressive strength with different chloride contents
5sim20GHz range are respectively averaged as one value toobtain parameter Each averaged value of conductivity anddielectric constant is plotted in Figure 8 with wc ratiosconsidering chloride contents
Typically porosity in cement mortar has effect on theconductivity and dielectric constant In cement mortarporosity becomes smaller with decrease in wc ratios due toabundant hydrates and the reduced porosity causes higherEMproperties [22 23 38] Usually permittivity of cement gel
0
1
2
3
4
5
0 2 4 6 8 10
Carb
onat
ion
dept
h (m
m)
Period (week)
wc 055wc 065
wc 045
Figure 7 Carbonation depth with exposed period
is in the level of 5sim10 and this is larger than that of air (=10)[2 13] One can also indicate that for the samples containingthe samewc ratiosmore chloride content leads to higher EMproperties due to reduced porosity
42 EM Characteristics and Compressive Strength As inSection 322 the addition of NaCl cannot cause a big changein strength The averaged EM properties can compare theresults of compressive strength as in Figure 9 EM properties(dielectric constant and conductivity) without chloride con-tent are used for the comparison with the results since theyare varying significantly with chloride addition Compressivestrength is reported to have linear relationship with wc ratio[22] As shown in Figure 8 EM properties without chloridecontent have linear relationship with wc ratio with highdetermination coefficient (1198772) so that linear relationship
6 Advances in Materials Science and Engineering
04
06
08
1
12
045 05 055 06 065
Aver
aged
cond
uctiv
ity (S
m)
wc ratio
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Averaged conductivity
3
4
5
6
7
045 05 055 06 065
Aver
aged
die
lect
ric co
nsta
nt
wc ratio
36kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Averaged dielectric constant
Figure 8 Averaged EM properties with different wc ratios and chloride contents
0
10
20
30
40
50
60
04 05 06 07 08 09
Com
pres
sive s
treng
th (M
Pa)
Averaged conductivity (Sm)
y = 66107x minus 76805
R2 = 09861
(a) Conductivity and strength
0
10
20
30
40
50
60
3 4 5 6
Com
pres
sive s
treng
th (M
Pa)
Averaged dielectric constant
y = 14637x minus 28161
R2 = 09868
(b) Dielectric constant and strength
Figure 9 EM properties and compressive strength
is found between EM properties and strength as shown inFigure 9
43 EMCharacteristics and Carbonation Velocity For porousmedia the diffusion mechanism in concrete is also closelyrelated with porosity characteristics [26ndash28] In Figure 10 theaveraged EM properties are compared with the carbonationvelocity obtained from the accelerated carbonation test Theresults are only for the case without chloride contents
The carbonation velocity is observed in linear proportionto the wc ratios and the trend can be found in conventionalequations for the prediction of carbonation depth [26 36]For the cement mortar without chloride amount it is foundthat that the averaged EM properties decrease with the highcarbonation velocity which is consistent with the resultsin high wc and low compressive strength Considering
the results in strength and carbonation depth the lower wcratio in cement mortar causes larger content of hydrateswhich yields high strength and low porosity The densestructure shows relatively high EM properties With increas-ing strength due to larger hydrates and lower porosity theresistance to carbonation also increases due to low CO
2
diffusion and more carbonatable materialsmdashCa(OH)2 In
Figure 10 higher carbonation velocity which means coarsestructure shows lower conductivity and electric constant
44 EM Characteristics and Chloride Content in Cement Mor-tar In the water-submerged condition chloride ion does notsignificantly affect dielectric constant however loss factorwhich causes attenuation is greatly changed due to increasein ohmic conductivity [3] In cement mortar both conduc-tivity and dielectric constant increase with larger amount
Advances in Materials Science and Engineering 7
0
02
04
06
08
1
0
1
2
3
4
5
6
05 06 07 08 09 1 11 12
Con
duct
ivity
(Sm
)
Die
lect
ric co
nsta
nt
DielectricConductivity
y = minus32795x + 71144
R2 = 09985
y = minus07258x + 12651
R2 = 09981
Carbonation velocity (mmweek05)
Reg (conductivity)Reg (dielectric constant)
Figure 10 Relationship between carbonation velocity and EM properties
04
05
06
07
08
09
1
11
0 1 2 3 4
Con
duct
ivity
(Sm
)
wc 065wc 055wc 045
NaCl content (kgm3)
(a) Conductivity variation
3
35
4
45
5
55
6
0 1 2 3 4
Die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl content (kgm3)
(b) Dielectric constant
Figure 11 Effect of chloride contents on conductivity and dielectric constant
of chloride amount It is because the chloride ion in initialmix causes smaller pore distribution in OPC mortar andsodium ion dissolved in pore water can increase conductivityand dielectric constant In Figure 11 the effect of chlorideon EM properties is plotted with varying chloride contentsThe result in higher wc ratio shows more rapid increase inboth conductivity and dielectric constant because the coarsepore structure in OPC mortar with higher wc ratio is moreaffected by chloride ion which can cause the densification ofpore structure
The regression analysis is performed with increasingratios to noncontaminated OPC mortar and is plotted inFigure 12 The linear relationships between EM propertiesand chloride content are summarized in Table 5 In Table 5the gradient of slope means the effect of chloride ion on
EM properties Lower wc ratio shows higher strength inconcrete and lower dependency of chloride ion howevermix conditions with high wc ratio (065) show clear increasein chloride effect When chloride ion is added to 36 kgm3conductivity and dielectric constant increase to 173 and134 respectivelyThe relationship shows clear linearity withhigh determination coefficient over 09 which strongly showsapplicability as NDT for evaluation of chloride contamina-tion for cement mortar
5 Concluding Remark
Among various nondestructive testing (NDT) techniqueselectromagnetic properties of conductivity and dielectricconstant are attempted for an evaluation of chloride effect
8 Advances in Materials Science and Engineering
1
12
14
16
18
0 1 2 3 4
Nor
mal
ized
cond
uctiv
ity
NaCl content (kgm3)
wc 065wc 055wc 045
(a) Normalized conductivity
1
11
12
13
14
0 1 2 3 4
Nor
mal
ized
die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl (kgm3)
(b) Normalized dielectric constant
Figure 12 Increasing ratios of EM properties with chloride contents
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
Figure 3 Conductivity and dielectric constant (wc 045)
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 4 Conductivity and dielectric constant (wc 055)
to the addition of calcium chloride (CaCl2) can accelerate
the hydration activity so that the compressive strengthin early-aged stage rapidly increases [33] Concrete withsodium chloride (NaCl) is reported to show little change inhydration activity but significant effects on drying shrinkagedue to the altered pore distribution [34] The test resultsof compressive strength are shown in Figure 6 where onecan indicate that the compressive strength has no clearrelationship with the chloride contents The similar resultsrelated to the compressive strength can be found in previousresearch [24] Traditional strength reduction is found inFigure 6 with increasing wc ratio
323 Accelerated Carbonation Test Result It is also foundthat concrete with low wc ratio shows small carbonationdepth since it has low diffusion coefficient of CO
2and
large amount of hydrates such as CHS and Ca(OH)2which
have potential to keep high pH in pore water [26 35]Carbonation velocity is usually adopted for carbonationresistance based on the assumption that carbonation depthhas linear relationship with square root of exposed time [3637] In Figure 7 the results of accelerated carbonation test areplotted which shows slower carbonation progress with lowerwc ratio Carbonation velocity through regression analysiscan be summarized in Table 4
4 Characteristics of EM Properties forDurability Evaluation
41 EM Characteristics and wc Ratios For the purpose ofcomparison of the results EM properties corresponding to
Advances in Materials Science and Engineering 5
0
03
06
09
12
15
18
02 5 10 15 20
Con
duct
ivity
(Sm
)
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Conductivity
2
3
4
5
6
7
8
02 5 10 15 20
Die
lect
ric co
nsta
nt
Frequency (GHz)
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Dielectric constant
Figure 5 Conductivity and dielectric constant (wc 065)
Figure 6 Compressive strength with different chloride contents
5sim20GHz range are respectively averaged as one value toobtain parameter Each averaged value of conductivity anddielectric constant is plotted in Figure 8 with wc ratiosconsidering chloride contents
Typically porosity in cement mortar has effect on theconductivity and dielectric constant In cement mortarporosity becomes smaller with decrease in wc ratios due toabundant hydrates and the reduced porosity causes higherEMproperties [22 23 38] Usually permittivity of cement gel
0
1
2
3
4
5
0 2 4 6 8 10
Carb
onat
ion
dept
h (m
m)
Period (week)
wc 055wc 065
wc 045
Figure 7 Carbonation depth with exposed period
is in the level of 5sim10 and this is larger than that of air (=10)[2 13] One can also indicate that for the samples containingthe samewc ratiosmore chloride content leads to higher EMproperties due to reduced porosity
42 EM Characteristics and Compressive Strength As inSection 322 the addition of NaCl cannot cause a big changein strength The averaged EM properties can compare theresults of compressive strength as in Figure 9 EM properties(dielectric constant and conductivity) without chloride con-tent are used for the comparison with the results since theyare varying significantly with chloride addition Compressivestrength is reported to have linear relationship with wc ratio[22] As shown in Figure 8 EM properties without chloridecontent have linear relationship with wc ratio with highdetermination coefficient (1198772) so that linear relationship
6 Advances in Materials Science and Engineering
04
06
08
1
12
045 05 055 06 065
Aver
aged
cond
uctiv
ity (S
m)
wc ratio
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Averaged conductivity
3
4
5
6
7
045 05 055 06 065
Aver
aged
die
lect
ric co
nsta
nt
wc ratio
36kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Averaged dielectric constant
Figure 8 Averaged EM properties with different wc ratios and chloride contents
0
10
20
30
40
50
60
04 05 06 07 08 09
Com
pres
sive s
treng
th (M
Pa)
Averaged conductivity (Sm)
y = 66107x minus 76805
R2 = 09861
(a) Conductivity and strength
0
10
20
30
40
50
60
3 4 5 6
Com
pres
sive s
treng
th (M
Pa)
Averaged dielectric constant
y = 14637x minus 28161
R2 = 09868
(b) Dielectric constant and strength
Figure 9 EM properties and compressive strength
is found between EM properties and strength as shown inFigure 9
43 EMCharacteristics and Carbonation Velocity For porousmedia the diffusion mechanism in concrete is also closelyrelated with porosity characteristics [26ndash28] In Figure 10 theaveraged EM properties are compared with the carbonationvelocity obtained from the accelerated carbonation test Theresults are only for the case without chloride contents
The carbonation velocity is observed in linear proportionto the wc ratios and the trend can be found in conventionalequations for the prediction of carbonation depth [26 36]For the cement mortar without chloride amount it is foundthat that the averaged EM properties decrease with the highcarbonation velocity which is consistent with the resultsin high wc and low compressive strength Considering
the results in strength and carbonation depth the lower wcratio in cement mortar causes larger content of hydrateswhich yields high strength and low porosity The densestructure shows relatively high EM properties With increas-ing strength due to larger hydrates and lower porosity theresistance to carbonation also increases due to low CO
2
diffusion and more carbonatable materialsmdashCa(OH)2 In
Figure 10 higher carbonation velocity which means coarsestructure shows lower conductivity and electric constant
44 EM Characteristics and Chloride Content in Cement Mor-tar In the water-submerged condition chloride ion does notsignificantly affect dielectric constant however loss factorwhich causes attenuation is greatly changed due to increasein ohmic conductivity [3] In cement mortar both conduc-tivity and dielectric constant increase with larger amount
Advances in Materials Science and Engineering 7
0
02
04
06
08
1
0
1
2
3
4
5
6
05 06 07 08 09 1 11 12
Con
duct
ivity
(Sm
)
Die
lect
ric co
nsta
nt
DielectricConductivity
y = minus32795x + 71144
R2 = 09985
y = minus07258x + 12651
R2 = 09981
Carbonation velocity (mmweek05)
Reg (conductivity)Reg (dielectric constant)
Figure 10 Relationship between carbonation velocity and EM properties
04
05
06
07
08
09
1
11
0 1 2 3 4
Con
duct
ivity
(Sm
)
wc 065wc 055wc 045
NaCl content (kgm3)
(a) Conductivity variation
3
35
4
45
5
55
6
0 1 2 3 4
Die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl content (kgm3)
(b) Dielectric constant
Figure 11 Effect of chloride contents on conductivity and dielectric constant
of chloride amount It is because the chloride ion in initialmix causes smaller pore distribution in OPC mortar andsodium ion dissolved in pore water can increase conductivityand dielectric constant In Figure 11 the effect of chlorideon EM properties is plotted with varying chloride contentsThe result in higher wc ratio shows more rapid increase inboth conductivity and dielectric constant because the coarsepore structure in OPC mortar with higher wc ratio is moreaffected by chloride ion which can cause the densification ofpore structure
The regression analysis is performed with increasingratios to noncontaminated OPC mortar and is plotted inFigure 12 The linear relationships between EM propertiesand chloride content are summarized in Table 5 In Table 5the gradient of slope means the effect of chloride ion on
EM properties Lower wc ratio shows higher strength inconcrete and lower dependency of chloride ion howevermix conditions with high wc ratio (065) show clear increasein chloride effect When chloride ion is added to 36 kgm3conductivity and dielectric constant increase to 173 and134 respectivelyThe relationship shows clear linearity withhigh determination coefficient over 09 which strongly showsapplicability as NDT for evaluation of chloride contamina-tion for cement mortar
5 Concluding Remark
Among various nondestructive testing (NDT) techniqueselectromagnetic properties of conductivity and dielectricconstant are attempted for an evaluation of chloride effect
8 Advances in Materials Science and Engineering
1
12
14
16
18
0 1 2 3 4
Nor
mal
ized
cond
uctiv
ity
NaCl content (kgm3)
wc 065wc 055wc 045
(a) Normalized conductivity
1
11
12
13
14
0 1 2 3 4
Nor
mal
ized
die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl (kgm3)
(b) Normalized dielectric constant
Figure 12 Increasing ratios of EM properties with chloride contents
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
Figure 6 Compressive strength with different chloride contents
5sim20GHz range are respectively averaged as one value toobtain parameter Each averaged value of conductivity anddielectric constant is plotted in Figure 8 with wc ratiosconsidering chloride contents
Typically porosity in cement mortar has effect on theconductivity and dielectric constant In cement mortarporosity becomes smaller with decrease in wc ratios due toabundant hydrates and the reduced porosity causes higherEMproperties [22 23 38] Usually permittivity of cement gel
0
1
2
3
4
5
0 2 4 6 8 10
Carb
onat
ion
dept
h (m
m)
Period (week)
wc 055wc 065
wc 045
Figure 7 Carbonation depth with exposed period
is in the level of 5sim10 and this is larger than that of air (=10)[2 13] One can also indicate that for the samples containingthe samewc ratiosmore chloride content leads to higher EMproperties due to reduced porosity
42 EM Characteristics and Compressive Strength As inSection 322 the addition of NaCl cannot cause a big changein strength The averaged EM properties can compare theresults of compressive strength as in Figure 9 EM properties(dielectric constant and conductivity) without chloride con-tent are used for the comparison with the results since theyare varying significantly with chloride addition Compressivestrength is reported to have linear relationship with wc ratio[22] As shown in Figure 8 EM properties without chloridecontent have linear relationship with wc ratio with highdetermination coefficient (1198772) so that linear relationship
6 Advances in Materials Science and Engineering
04
06
08
1
12
045 05 055 06 065
Aver
aged
cond
uctiv
ity (S
m)
wc ratio
36 kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(a) Averaged conductivity
3
4
5
6
7
045 05 055 06 065
Aver
aged
die
lect
ric co
nsta
nt
wc ratio
36kgm3 NaCl12 kgm3 NaCl
06 kgm3 NaCl00 kgm3 NaCl
(b) Averaged dielectric constant
Figure 8 Averaged EM properties with different wc ratios and chloride contents
0
10
20
30
40
50
60
04 05 06 07 08 09
Com
pres
sive s
treng
th (M
Pa)
Averaged conductivity (Sm)
y = 66107x minus 76805
R2 = 09861
(a) Conductivity and strength
0
10
20
30
40
50
60
3 4 5 6
Com
pres
sive s
treng
th (M
Pa)
Averaged dielectric constant
y = 14637x minus 28161
R2 = 09868
(b) Dielectric constant and strength
Figure 9 EM properties and compressive strength
is found between EM properties and strength as shown inFigure 9
43 EMCharacteristics and Carbonation Velocity For porousmedia the diffusion mechanism in concrete is also closelyrelated with porosity characteristics [26ndash28] In Figure 10 theaveraged EM properties are compared with the carbonationvelocity obtained from the accelerated carbonation test Theresults are only for the case without chloride contents
The carbonation velocity is observed in linear proportionto the wc ratios and the trend can be found in conventionalequations for the prediction of carbonation depth [26 36]For the cement mortar without chloride amount it is foundthat that the averaged EM properties decrease with the highcarbonation velocity which is consistent with the resultsin high wc and low compressive strength Considering
the results in strength and carbonation depth the lower wcratio in cement mortar causes larger content of hydrateswhich yields high strength and low porosity The densestructure shows relatively high EM properties With increas-ing strength due to larger hydrates and lower porosity theresistance to carbonation also increases due to low CO
2
diffusion and more carbonatable materialsmdashCa(OH)2 In
Figure 10 higher carbonation velocity which means coarsestructure shows lower conductivity and electric constant
44 EM Characteristics and Chloride Content in Cement Mor-tar In the water-submerged condition chloride ion does notsignificantly affect dielectric constant however loss factorwhich causes attenuation is greatly changed due to increasein ohmic conductivity [3] In cement mortar both conduc-tivity and dielectric constant increase with larger amount
Advances in Materials Science and Engineering 7
0
02
04
06
08
1
0
1
2
3
4
5
6
05 06 07 08 09 1 11 12
Con
duct
ivity
(Sm
)
Die
lect
ric co
nsta
nt
DielectricConductivity
y = minus32795x + 71144
R2 = 09985
y = minus07258x + 12651
R2 = 09981
Carbonation velocity (mmweek05)
Reg (conductivity)Reg (dielectric constant)
Figure 10 Relationship between carbonation velocity and EM properties
04
05
06
07
08
09
1
11
0 1 2 3 4
Con
duct
ivity
(Sm
)
wc 065wc 055wc 045
NaCl content (kgm3)
(a) Conductivity variation
3
35
4
45
5
55
6
0 1 2 3 4
Die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl content (kgm3)
(b) Dielectric constant
Figure 11 Effect of chloride contents on conductivity and dielectric constant
of chloride amount It is because the chloride ion in initialmix causes smaller pore distribution in OPC mortar andsodium ion dissolved in pore water can increase conductivityand dielectric constant In Figure 11 the effect of chlorideon EM properties is plotted with varying chloride contentsThe result in higher wc ratio shows more rapid increase inboth conductivity and dielectric constant because the coarsepore structure in OPC mortar with higher wc ratio is moreaffected by chloride ion which can cause the densification ofpore structure
The regression analysis is performed with increasingratios to noncontaminated OPC mortar and is plotted inFigure 12 The linear relationships between EM propertiesand chloride content are summarized in Table 5 In Table 5the gradient of slope means the effect of chloride ion on
EM properties Lower wc ratio shows higher strength inconcrete and lower dependency of chloride ion howevermix conditions with high wc ratio (065) show clear increasein chloride effect When chloride ion is added to 36 kgm3conductivity and dielectric constant increase to 173 and134 respectivelyThe relationship shows clear linearity withhigh determination coefficient over 09 which strongly showsapplicability as NDT for evaluation of chloride contamina-tion for cement mortar
5 Concluding Remark
Among various nondestructive testing (NDT) techniqueselectromagnetic properties of conductivity and dielectricconstant are attempted for an evaluation of chloride effect
8 Advances in Materials Science and Engineering
1
12
14
16
18
0 1 2 3 4
Nor
mal
ized
cond
uctiv
ity
NaCl content (kgm3)
wc 065wc 055wc 045
(a) Normalized conductivity
1
11
12
13
14
0 1 2 3 4
Nor
mal
ized
die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl (kgm3)
(b) Normalized dielectric constant
Figure 12 Increasing ratios of EM properties with chloride contents
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
Figure 8 Averaged EM properties with different wc ratios and chloride contents
0
10
20
30
40
50
60
04 05 06 07 08 09
Com
pres
sive s
treng
th (M
Pa)
Averaged conductivity (Sm)
y = 66107x minus 76805
R2 = 09861
(a) Conductivity and strength
0
10
20
30
40
50
60
3 4 5 6
Com
pres
sive s
treng
th (M
Pa)
Averaged dielectric constant
y = 14637x minus 28161
R2 = 09868
(b) Dielectric constant and strength
Figure 9 EM properties and compressive strength
is found between EM properties and strength as shown inFigure 9
43 EMCharacteristics and Carbonation Velocity For porousmedia the diffusion mechanism in concrete is also closelyrelated with porosity characteristics [26ndash28] In Figure 10 theaveraged EM properties are compared with the carbonationvelocity obtained from the accelerated carbonation test Theresults are only for the case without chloride contents
The carbonation velocity is observed in linear proportionto the wc ratios and the trend can be found in conventionalequations for the prediction of carbonation depth [26 36]For the cement mortar without chloride amount it is foundthat that the averaged EM properties decrease with the highcarbonation velocity which is consistent with the resultsin high wc and low compressive strength Considering
the results in strength and carbonation depth the lower wcratio in cement mortar causes larger content of hydrateswhich yields high strength and low porosity The densestructure shows relatively high EM properties With increas-ing strength due to larger hydrates and lower porosity theresistance to carbonation also increases due to low CO
2
diffusion and more carbonatable materialsmdashCa(OH)2 In
Figure 10 higher carbonation velocity which means coarsestructure shows lower conductivity and electric constant
44 EM Characteristics and Chloride Content in Cement Mor-tar In the water-submerged condition chloride ion does notsignificantly affect dielectric constant however loss factorwhich causes attenuation is greatly changed due to increasein ohmic conductivity [3] In cement mortar both conduc-tivity and dielectric constant increase with larger amount
Advances in Materials Science and Engineering 7
0
02
04
06
08
1
0
1
2
3
4
5
6
05 06 07 08 09 1 11 12
Con
duct
ivity
(Sm
)
Die
lect
ric co
nsta
nt
DielectricConductivity
y = minus32795x + 71144
R2 = 09985
y = minus07258x + 12651
R2 = 09981
Carbonation velocity (mmweek05)
Reg (conductivity)Reg (dielectric constant)
Figure 10 Relationship between carbonation velocity and EM properties
04
05
06
07
08
09
1
11
0 1 2 3 4
Con
duct
ivity
(Sm
)
wc 065wc 055wc 045
NaCl content (kgm3)
(a) Conductivity variation
3
35
4
45
5
55
6
0 1 2 3 4
Die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl content (kgm3)
(b) Dielectric constant
Figure 11 Effect of chloride contents on conductivity and dielectric constant
of chloride amount It is because the chloride ion in initialmix causes smaller pore distribution in OPC mortar andsodium ion dissolved in pore water can increase conductivityand dielectric constant In Figure 11 the effect of chlorideon EM properties is plotted with varying chloride contentsThe result in higher wc ratio shows more rapid increase inboth conductivity and dielectric constant because the coarsepore structure in OPC mortar with higher wc ratio is moreaffected by chloride ion which can cause the densification ofpore structure
The regression analysis is performed with increasingratios to noncontaminated OPC mortar and is plotted inFigure 12 The linear relationships between EM propertiesand chloride content are summarized in Table 5 In Table 5the gradient of slope means the effect of chloride ion on
EM properties Lower wc ratio shows higher strength inconcrete and lower dependency of chloride ion howevermix conditions with high wc ratio (065) show clear increasein chloride effect When chloride ion is added to 36 kgm3conductivity and dielectric constant increase to 173 and134 respectivelyThe relationship shows clear linearity withhigh determination coefficient over 09 which strongly showsapplicability as NDT for evaluation of chloride contamina-tion for cement mortar
5 Concluding Remark
Among various nondestructive testing (NDT) techniqueselectromagnetic properties of conductivity and dielectricconstant are attempted for an evaluation of chloride effect
8 Advances in Materials Science and Engineering
1
12
14
16
18
0 1 2 3 4
Nor
mal
ized
cond
uctiv
ity
NaCl content (kgm3)
wc 065wc 055wc 045
(a) Normalized conductivity
1
11
12
13
14
0 1 2 3 4
Nor
mal
ized
die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl (kgm3)
(b) Normalized dielectric constant
Figure 12 Increasing ratios of EM properties with chloride contents
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
Figure 10 Relationship between carbonation velocity and EM properties
04
05
06
07
08
09
1
11
0 1 2 3 4
Con
duct
ivity
(Sm
)
wc 065wc 055wc 045
NaCl content (kgm3)
(a) Conductivity variation
3
35
4
45
5
55
6
0 1 2 3 4
Die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl content (kgm3)
(b) Dielectric constant
Figure 11 Effect of chloride contents on conductivity and dielectric constant
of chloride amount It is because the chloride ion in initialmix causes smaller pore distribution in OPC mortar andsodium ion dissolved in pore water can increase conductivityand dielectric constant In Figure 11 the effect of chlorideon EM properties is plotted with varying chloride contentsThe result in higher wc ratio shows more rapid increase inboth conductivity and dielectric constant because the coarsepore structure in OPC mortar with higher wc ratio is moreaffected by chloride ion which can cause the densification ofpore structure
The regression analysis is performed with increasingratios to noncontaminated OPC mortar and is plotted inFigure 12 The linear relationships between EM propertiesand chloride content are summarized in Table 5 In Table 5the gradient of slope means the effect of chloride ion on
EM properties Lower wc ratio shows higher strength inconcrete and lower dependency of chloride ion howevermix conditions with high wc ratio (065) show clear increasein chloride effect When chloride ion is added to 36 kgm3conductivity and dielectric constant increase to 173 and134 respectivelyThe relationship shows clear linearity withhigh determination coefficient over 09 which strongly showsapplicability as NDT for evaluation of chloride contamina-tion for cement mortar
5 Concluding Remark
Among various nondestructive testing (NDT) techniqueselectromagnetic properties of conductivity and dielectricconstant are attempted for an evaluation of chloride effect
8 Advances in Materials Science and Engineering
1
12
14
16
18
0 1 2 3 4
Nor
mal
ized
cond
uctiv
ity
NaCl content (kgm3)
wc 065wc 055wc 045
(a) Normalized conductivity
1
11
12
13
14
0 1 2 3 4
Nor
mal
ized
die
lect
ric co
nsta
nt
wc 065wc 055wc 045
NaCl (kgm3)
(b) Normalized dielectric constant
Figure 12 Increasing ratios of EM properties with chloride contents
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
in cement-based construction material The conclusions oneffect of chlorides on conductivity and dielectric constant inhardened cement mortar are as follows
(1) Through the measurement of electromagnetic prop-erties within the 02sim20GHz frequency range thepatterns of dielectric constant and conductivity areinvestigated in cement mortar with 00sim36 kgm3of chloride addition The relationships between elec-tromagnetic properties and engineering parameterslike wc ratios carbonation velocity and the inducedchloride content are compared as well
(2) The carbonation velocities and compressive strengthare measured for OPC mortar with different wcratios Then the results are compared with averagedEM properties Both conductivity and dielectric con-stant linearly decrease with increasing carbonationvelocity and decreasing compressive strength withhigh determination coefficientWithmore addition ofchloride content to cementmortar dielectric constantand conductivity are observed to linearly increaseReferred to the results without chlorides the cementmortar containing 36 kgm3 of chloride amountshows 173 increasing of dielectric constant and 134
increasing of conductivity The linear regression withhigh determination coefficient is also observed withmore chloride content
Competing Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgments
This research was supported by Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) funded by the Ministry of Science ICT amp FuturePlanning (no 2015R1A5A1037548)
References
[1] J Glanvile and A Nevile ldquoPrediction of concrete durabilityrdquoin Proceedings of the STATS 21st Anniversary Conference EampFNSPON London UK November 1995
[2] U B Halabe A Sotoodehnia K R Maser and E A KauselldquoModeling the electromagnetic properties of concreterdquo ACIMaterials Journal vol 90 no 6 pp 552ndash563 1993
[3] H C Rhim and O Buyukozturk ldquoElectromagnetic propertiesof concrete at microwave frequency rangerdquo ACI MaterialsJournal vol 95 no 3 pp 262ndash271 1998
[4] M N Soutsos J H Bungey S G Millard M R Shaw and APatterson ldquoDielectric properties of concrete and their influenceon radar testingrdquoNDTampE International vol 34 no 6 pp 419ndash425 2001
[5] F H Wittmann and F Schlude ldquoMicrowave absorption ofhardened cement pasterdquo Cement and Concrete Research vol 5no 1 pp 63ndash71 1975
[6] W J McCarter T M Chrisp G Starrs and J BlewettldquoCharacterization and monitoring of cement-based systems
Advances in Materials Science and Engineering 9
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
using intrinsic electrical property measurementsrdquo Cement andConcrete Research vol 33 no 2 pp 197ndash206 2003
[7] W J McCarter T M Chrisp and G Starrs ldquoThe earlyhydration of alkali-activated slag developments in monitoringtechniquesrdquo Cement and Concrete Composites vol 21 no 4 pp277ndash283 1999
[8] W J McCarter G Starrs and T M Chrisp ldquoImmittancespectra for Portland cementfly ash-based binders during earlyhydrationrdquo Cement and Concrete Research vol 29 no 3 pp377ndash387 1999
[9] W J McCarter G Starrs and T M Chrisp ldquoThe compleximpedance response of fly-ash cements revisitedrdquo Cement andConcrete Research vol 34 no 10 pp 1837ndash1843 2004
[10] C Shi J A Stegemann andR J Caldwell ldquoEffect of supplemen-tary cementing materials on the specific conductivity of poresolution and its implications on the rapid chloride permeabilitytest (AASHTO T277 and ASTM C1202) resultsrdquo ACI MaterialsJournal vol 95 no 4 pp 389ndash394 1998
[11] W J McCarter G Starrs and T M Chrisp ldquoElectrical con-ductivity diffusion and permeability of Portland cement-basedmortarsrdquoCement andConcrete Research vol 30 no 9 pp 1395ndash1400 2000
[12] E J Garboczi L M Schwartz and D P Bentz ldquoModellingthe DC electrical conductivity of mortarrdquo Materials ResearchSociety Symposia Proceedings vol 370 pp 429ndash436 1995
[13] U B Halabe Condition assessment of reinforced concrete struc-tures using electromagnetic waves [PhD thesis] Department ofCivil amp Environmental Engineering MIT Cambridge MassUSA 1990
[14] S Feng and P N Sen ldquoGeometrical model of conductive anddielectric properties of partially saturated rocksrdquo Journal ofApplied Physics vol 58 no 8 pp 3236ndash3243 1985
[15] WMK RoddisConcrete bridge deck assessment using thermog-raphy and radar [MS thesis] Department of Civil EngineeringMassachusetts Institute of Technology Cambridge Mass USA1987
[16] T M Chrisp W J McCarter G Starrs P A M Basheer andJ Blewett ldquoDepth-related variation in conductivity to studycover-zone concrete during wetting and dryingrdquo Cement andConcrete Composites vol 24 no 5 pp 415ndash426 2002
[17] H C Rhim ldquoCondition monitoring of deteriorating concretedams using radarrdquo Cement and Concrete Research vol 31 no 3pp 363ndash373 2001
[18] S-J Kwon M Q Feng and S S Park ldquoCharacterizationof electromagnetic properties for durability performance andsaturation in hardened cement mortarrdquoNDTamp E Internationalvol 43 no 2 pp 86ndash95 2010
[19] M Q Feng F De Flaviis and Y J Kim ldquoUse of microwavesfor damage detection of fiber reinforced polymer-wrappedconcrete structuresrdquo Journal of Engineering Mechanics vol 128no 2 pp 172ndash183 2002
[20] Y J Kim L Jofre F De Flaviis and M Q Feng ldquoMicrowavereflection tomography array for damage detection in concretestructuresrdquo in Proceedings of the IEEE MSS-S InternationalMicrowave Symposium Digest vol 51 pp 651ndash654 June 2002
[21] H C Rhim Y J Kim M Q Feng S K Woo and Y CSong ldquoMeasurements of electromagnetic properties of concreteand fiber reinforced polymer for nondestructive testingrdquo inProceedings of the US-Korea Joint SeminarWorkshop on SmartStructures Technologies Seoul Republic of Korea 2004
[22] PKMetha andP JMMonteiroConcrete Structure Propertiesand Materials Prentice Hall Englewood Cliffs NJ USA 2ndedition 1993
[23] A M Neville Properties of Concrete Longman New York NYUSA 1996
[24] H W Song H J Cho S S Park K J Byun and K MaekawaldquoEarly-age cracking resistance evaluation of concrete structurerdquoConcrete Science Engineering vol 3 pp 62ndash72 2001
[25] T Gonen and S Yazicioglu ldquoThe influence of compaction poreson sorptivity and carbonation of concreterdquo Construction andBuilding Materials vol 21 no 5 pp 1040ndash1045 2007
[26] H-W Song S-J Kwon K-J Byun and C-K Park ldquoPredictingcarbonation in early-aged cracked concreterdquo Cement and Con-crete Research vol 36 no 5 pp 979ndash989 2006
[27] H W Song S J Kwon K J Byun and C K Park ldquoAstudy on analytical technique of chloride diffusion consideringcharacteristics ofmixture design for high performance concreteusing mineral admixturerdquo Journal of the Korean Society of CivilEngineers vol 25 no 1 pp 213ndash223 2005
[28] H-W Song and S-J Kwon ldquoPermeability characteristics of car-bonated concrete considering capillary pore structurerdquo Cementand Concrete Research vol 37 no 6 pp 909ndash915 2007
[29] A Nyshadham C L Sibbald and S S Stuchly ldquoPermittivitymeasurements using open-ended sensors and reference liquidcalibrationmdashan uncertainty analysisrdquo IEEE Transactions onMicrowave Theory and Techniques vol 40 no 2 pp 305ndash3141992
[30] Korea Standard Method of Test for Compressive Strength ofConcrete KSF 2405 2005
[31] Korea Standard Standard test method for accelerated carbona-tion of concrete KSF2584 2005
[32] Korea Standard ldquoMethod for measuring carbonation depth ofconcreterdquo KSF 2596 2004
[33] P W Brown C L Harner and E J Prosen ldquoThe effect ofinorganic salts on tricalcium silicate hydrationrdquo Cement andConcrete Research vol 16 no 1 pp 17ndash22 1986
[34] A K Suryavanshi J D Scantlebury and S B Lyon ldquoPore sizedistribution of OPC amp SRPC mortars in presence of chloridesrdquoCement and Concrete Research vol 25 no 5 pp 980ndash988 1995
[35] T Ishida and K Maekawa ldquoModeling of PH profile in porewater based on mass transport and chemical equilibriumtheoryrdquo Concrete Library International JSCE Publication vol 37pp 131ndash146 2001
[36] I Izumi D Kita and H Maeda Carbonation KibodangPublication 1986
[37] V G Papadakis C G Vayenas andMN Fardis ldquoFundamentalmodeling and experimental investigation of concrete carbona-tionrdquo ACI Materials Journal vol 88 no 4 pp 363ndash373 1991
[38] K Maekawa R Chaube and T Kishi Modeling of ConcretePerformance EampFN SPON 1999
