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Resources, Conservation and Recycling 61 (2012) 125– 129

Contents lists available at SciVerse ScienceDirect

Resources, Conservation and Recycling

journa l h o me pa ge: www.elsev ier .com/ locate / resconrec

valuation of non-destructive testing of high strength concrete incorporatingupplementary cementitious composites

ohammad Iqbal Khan ∗

epartment of Civil Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia

r t i c l e i n f o

rticle history:eceived 8 September 2011eceived in revised form 25 January 2012ccepted 27 January 2012

eywords:igh strength concrete

a b s t r a c t

Nondestructive testing (NDT) is a technique to determine the integrity of a material, component or struc-ture. The commonly NDT methods used for the concrete are sorptivity, dynamic modulus of elasticity,ultrasonic pulse velocity, etc. The sorptivity is an easily measured material property which characterizesthe tendency of a porous material to absorb and transmit fluids by capillarity. The dynamic modulus ofelasticity of concrete is related to the structural stiffness and deformation process of concrete structures.The velocity of ultrasonic pulses traveling in a solid material depends on the density and elastic proper-

DTupplementary cementitious composites

ties of the material. In this investigation, non-destructive testing namely, sorptivity, dynamic modulus ofelasticity and ultrasonic pulse velocity was measured for high strength concrete incorporating cementi-tious composites. It was found that the incorporation of fly ash resulted lower sorptivity, especially withup to 20% fly ash contents and inclusion of microsilica reduced sorptivity significantly. NDT is reasonablygood and reliable tool to measure the property of concrete which also gives the fair indication of thecompressive strength development.

. Introduction

Nondestructive testing is a technique to determine the integrityf a material, component or structure. NDT is an assessment with-ut doing harm, stress or destroying the test object. The destructionf the test object usually makes destructive testing more costly andt is also inappropriate in many circumstances. NDT plays a crucialole in ensuring cost effective operation, safety and reliability. Theommonly NDT methods used for concrete are dynamic modulus oflasticity and ultrasonic pulse velocity. These methods are used toonitor service wear and deterioration of concrete and to diagnose

he possible severe zones of the concrete degradation or to detectuality of the concrete. The dynamic modulus of elasticity of con-rete is related to the structural stiffness and deformation processf concrete structures, and is highly sensitive to the cracking. Theelocity of ultrasonic pulses traveling in a solid material dependsn the density and elastic properties of that material. The qualityf some concrete is sometimes related to their elastic stiffness andan often be used to indicate their quality as well as to determineheir elastic properties.

The sorptivity is a measure of NDT which is an easily measuredaterial property which characterizes the tendency of a porousaterial to absorb and transmit water by capillarity. The movement

∗ Tel.: +966 14676920; fax: +966 14677008.E-mail address: miqbal@ksu.edu.sa

921-3449/$ – see front matter © 2012 Elsevier B.V. All rights reserved.oi:10.1016/j.resconrec.2012.01.013

© 2012 Elsevier B.V. All rights reserved.

of water into concrete is controlled by capillary suction forces exist-ing in the empty capillary cavities within the paste matrix. This inturn depends on the saturation gradient through the cover regionwhich varies depending on the time of the year. As the degree ofsaturation of a material increases, capillary suction forces reduce,being zero in a fully saturated state. Movement of water and ionsinto concrete is thus a combination of movement by capillary suc-tion forces and diffusion process. The term permeability is oftenused in connection with concrete durability which relates to themovement of a fluid under the action of a pressure differential. Butin the case of the structures which are above the ground are sub-jected to a cyclic wetting and drying regime, it is capillary suctionforces that are responsible for the ingress of contaminated water.Sorptivity test determines the rate of capillary rise absorption by amortar or concrete prism. The increase in the mass of the prismwith time is recorded. The movement of water is presented by‘square-root-time’ relationship (Hall, 1989).

Conventional concretes often fail to prevent the ingress ofmoisture and aggressive ions adequately. The use of supplemen-tary composite systems increases the resistance of concrete todeterioration by aggressive chemicals such as chlorides (Malhotraand Mehta, 1996; Siddique and Khan, 2011). Fly ash has beenwidely used in concrete as it helps to reduce cost, conserve energy

and resources, reduce environmental impact and enhance theworkability (Siddique and Khan, 2011). Microsilica, due to itshigh pozzolanicity and its extreme fineness, is considered to pro-duce low permeability concrete (FIP Report, 1988). Both fly ash

126 M.I. Khan / Resources, Conservation and Recycling 61 (2012) 125– 129

Table 1Chemical composition of fly ash and microsilica.

Oxides Fly ash (% by weight) Microsilica (% by weight)

SiO2 52.0 90.0Al2O3 27.0 1.0Fe2O3 10.0 1.0

abhtsataimccweiehate

2

2

strToiuowtsctenHc

sed2i2

ba9ss

0

4

8

12

16

20

20181614121086420

Incr

ease

in

Mas

s, 1

0-4

x g

/mm

2

0.50

Control Mix

20%FA

10%MS

40%FA+10%MS

CaO <6.0 0.3MgO <4.0 0.6SO3 <2.6 0.3

nd microsilica are industrial byproducts and utilization of theseyproducts is very effective in the design and development ofigh strength concrete hence has become an attractive alterna-ive to disposal. The use of fly ash causes delay in the early-agetrength development of concrete and microsilica increases early-ge strength development and provides better durability comparedo fly ash but with the drawback of low workability. However, flysh and microsilica could be blended in a way to derive the max-mum short-term and long-term benefits from the use of these

aterials for the production of high strength/performance con-rete. At present the information pertaining to NDT of high strengthoncrete incorporating ternary blended cementitious composites,hich is pertinent to its practical use, is scarce. Therefore, it is nec-

ssary to further investigate ternary blended concrete in detail forts practical use. In this paper sorptivity (S), dynamic modulus oflasticity (Ed) and ultrasonic pulse velocity (V) was conducted onigh strength concrete using cementitious materials such as fly ashnd microsilica to facilitate the formulation of standard specifica-ions, and to transfer research findings into a form which practisingngineer can implement.

. Experimental program

.1. Materials and sample preparation

Type I cement and fly ash (FA) complying ASTM standards andlurry form microsilica (MS) were used throughout the investiga-ion. The fineness of FA and MS was 350 m2/kg and 18,000 m2/kg,espectively. The chemical composition of FA and MS is shown inable 1. Fly ash and MS were used as partial cement replacementsn a weight to weight basis. Various replacement levels of FA wasncorporated as partial cement replacement and to these blendsp to 15% MS replacement levels were incorporated to make vari-us binary and ternary composite systems. Since this investigationas aimed at achieving high strength concrete, relatively low water

o cementitious ratio of 0.30 was used throughout. The constantlump was achieved using sulphonated naphthalene formaldehydeondensate superplasticizer. The superplasticizer dosage requiredo maintain the constant slump was between 10 and 12 L/m3. Asxpected, the superplasticizer dosage required for the same nomi-al slump was observed to increase with the increase in MS content.owever, in ternary blended concrete mixtures, the superplasti-izer dosage decreased with an increase in FA content.

Concrete prisms of 76 mm × 76 mm × 280 mm were cast fororptivity measurements. Samples were taken out of the curingnvironment at the required testing age. The samples were thenried in an oven at the temperature of 105 ± 5 ◦C for approximately4 h, until constant weight was reached. Prior to testing of sorptiv-

ty, the samples were kept in a dessicator for cooling for another4 h.

For the measurement of Ed and V, 100 mm × 100 mm × 500 mmeams were cast, all the specimens were cast and compacted in

ccordance with ASTM standards. Testing was conducted at 7, 28,0 and 180 days. Since the test is a non-destructive one, the samepecimens were used for the measurement at the all test ages. Twopecimens were used for each age and three measurements were

Time (square root scale), min

Fig. 1. Relationship between increase in mass and time at 28 days.

taken for each specimen and the mean of the six is reported as aresult.

2.2. Testing procedure

2.2.1. SorptivityThe moment of water into concrete and other building materials

is governed by a square root-time relationship (Hall, 1989). In thisrelationship, water absorption into a porous material increases asthe square root of the elapsed time. Assuming a constant watersupply at the inflow surfaces, the relationship is as follows:

i = S√

t (1)

where i is the cumulative absorbed volume of water per unit area ofinflow surface (g/mm2); t is the elapsed time (min); S is sorptivity(g/mm2/min0.5). The sorptivity coefficient S is obtained from theslope of i vs t0.5 curve (Fig. 1).

Oven dried samples were placed vertically in water on 5 mmdiameter steel rods to allow free access of water to the inflow. Thewater level was maintained at 5 mm above the base of the prism. Inorder to maintain accuracy of the results, the lower parts of the sidesof the specimens adjoining the inflow face were sealed with a bitu-minous paint. The quantity of the absorbed water (mass change)was measured at 1, 9, 25, 49, 81, 121, 169, 225, 289 and 361 minafter moping off with a damp tissue. The quantity of sorbed watervs the square-root of time was fitted to a straight line as shown inFig. 1. The measurements were taken for triplicate samples and themean was reported as result.

2.2.2. Dynamic modulus of elasticityThe dynamic modulus of elasticity measurement was con-

ducted by excitation in the longitudinal mode of vibration on the100 mm × 100 mm end face of a beam with the path length of500 mm. The exciter is driven by a variable frequency oscillator.The vibrations propagated within the specimen are received by thepick-up, amplified, and their amplitude is measured on an oscil-loscope. The input vibration from the exciter was varied until theresonance is obtained at the fundamental frequency of the spec-imen indicated by the maximum amplitude of the oscilloscope.The test procedure complies with BS 1881. The Ed (GPa) has beenestimated using the following expression:

Ed = 4�2L2�10−15 (2)

where L is the length of specimen (mm); � is the fundamental fre-quency in the longitudinal mode of vibration (Hz) and � is thedensity of the specimen (kg/m3).

M.I. Khan / Resources, Conservation and Recycling 61 (2012) 125– 129 127

5

6

7

8

9

2101801501209060300

Sorp

tivit

y, 10-3

x m

m/m

in0.5

0

Control mix 20%FA

30%FA 5%MS

10%MS 15%MS

2

Pdwwttaf

V

wb

3

3

miu

R² = 0.84

4

5

6

7

8

9

0.50.40.30.20.10

Sorp

tivit

y, 1

0-3

x m

m/m

in0

.50

-16 2

Control mix

FA or MS

FA + MS

Testing age, days

Fig. 2. Sorptivity of concrete incorporating fly ash or microsilica.

.2.3. Ultrasonic pulse velocityA portable ultrasonic non-destructive indicating test (known as

UNDIT) instrument was used for the measurement of V in accor-ance with BS 1881: Part 203 (1986). The time taken by the pulsingave to travel from one longitudinal end of the prism to the otheras recorded by means of 54 kHz transducers of 50 mm diame-

er. The ultrasonic velocity was determined by measuring the timeaken for longitudinal vibrations of ultrasonic frequency to travel

known distance through the material and was calculated by theollowing expression:

= L

T(3)

here V is ultrasonic pulse velocity (km/s); L is distance traveledy pulse (mm) and T is time taken (�s).

. Results and discussion

.1. Sorptivity

Sorptivity of composite systems incorporating fly ash and/oricrosilica is shown in Figs. 2 and 3. It is demonstrated that the

ncorporation of fly ash had little influence on sorptivity at agesp to 90 days (Fig. 2). At 180 days a slight reduction in sorptivity

5

6

7

8

9

2101801501209060300

So

rpti

vit

y,

10

-3x m

m/m

in0.5

0

Testing age, days

Control mix 20%FA+5%MS

20%FA+10%MS 30%FA+10%MS

40%FA+10%MS 40%FA15%MS

Fig. 3. Sorptivity of concrete incorporating fly ash and microsilica.

Permeabili ty, x 10 , m

Fig. 4. Relationship between sorptivity and permeability of concrete.

is recorded by incorporation of up to 20% fly ash. The additionof microsilica demonstrated reduction in sorptivity at all agesinvestigated. However, this reduction in sorptivity was greater forup to 10% microsilica replacement level, beyond that a marginalor reversed reduction was noticed. The optimum performance isdemonstrated between 8 and 12% microsilica, which exhibitedlowest sorptivity values for all fly ash replacement levels. FromFig. 3, the inclusion of microsilica to the systems containing fly ashreduced sorptivity significantly at all ages investigated.

It is clear from the above results that the incorporation of flyash demonstrated slight reduction in sorptivity. The inclusion ofmicrosilica resulted in significant reductions, for all concrete mixeswith or without fly ash (Fig. 3).

It is reported that the use of fly ash, due to its pozzolanic reactionand water reducing effect, makes concrete airtight and microsilica,due to its high pozzolanicity and extreme fineness, significantlyreduced the permeability at all ages (Nagataki and Ujike, 1986).The inclusion of 10% microsilica as cement replacement reducestotal porosity of paste prepared with w/b ratios between 0.20 and0.30 (Zhang and Gjorv, 1991).

The results presented here, suggest that there is an interactionbetween fly ash and microsilica, with their level of replacement andthe age of curing influencing their effect on sorptivity. The lowersorption values are as a result of micro-filling and pore refinementin these mixes (Khan, 2010) and modification of cement hydratesdue to pozzolanic reaction in the presence of fly ash and microsil-ica (Weng et al., 1997). The incorporation of fly ash achieved onlyslight reductions, therefore, the use of fly ash, as cement replace-ment becomes optional. However, the use of fly ash is viable wheneconomical and environmental benefits are sought given the levelof performance achieved.

3.2. Relationships of sorptivity, permeability and porosity

There is a link between sorptivity, porosity (P) and permeability(k). Porosity is measure of total pores present in the system whereaspermeability is related to the interconnectivity of the pores. Thepermeability results and porosity results which are published else-where (Khan and Lynsdale, 2002) were related to sorptivity asshown in Figs. 4 and 5. The relationship fitted expressions as fol-lows:

S = 10.3k0.23 (4)

S = 0.05P1.9 (5)

128 M.I. Khan / Resources, Conservation and Recycling 61 (2012) 125– 129

R² = 0.85

4

5

6

7

8

9

151413121110

Sorp

tivit

y, 10

-3x m

m/m

in0.5

0

Porosity, %

Control mix

FA or MS

FA + MS

Imltfctw

3

coatFIbeo

Fi

4.2

4.4

4.6

4.8

5.0

5.2

2101801501209060300

Ult

raso

nic

Puls

e V

eloci

ty, K

m/s

ec

Testing age, days

Control mix 20%FA

30%FA 5%MS

10%MS 20%FA+5%MS

30%FA+5%MS 30%FA+10%MS

of low early-age strength of FA concrete can be removed using bothFA and MS (Mehta and Gjorv, 1982).

Fig. 5. Relationship between sorptivity and porosity of concrete.

t can be seen that there is a reasonable correlation between per-eability and sorptivity (Fig. 4). It is interesting to note that the

ower permeability values demonstrated good correlation withheir respective sorptivity values but as the values increases the dif-erence become wider. Fig. 5 demonstrates that there is a fairly goodorrelation between porosity and sorptivity. In case of porosityhere is relatively wider range of values which shows relationshipith their respective values of sorptivity.

.3. Dynamic modulus of elasticity

Fig. 6 shows the dynamic modulus of elasticity at various ages. Itan be seen from this figure that the dynamic modulus of elasticityf concrete increased with ages, as expected. Ed decreased withn increase in FA content for a particular MS content, for all agesested. On the other hand, increasing the MS content for a particularA content above 5% replacement level, results in an increase in Ed.t is evident that up to 5% MS incorporation in FA concrete has noeneficial effect in increasing Ed over those of control mix. It is alsovident that at 90 days and for lower FA contents, the incorporation

f MS did not seem to affect the Ed appreciably.

40

42

44

46

48

50

52

54

2101801501209060300

Dynam

ic M

odulu

s of

Ela

stic

ity, G

Pa

Testing age, days

Control mix 20%FA

30%FA 5%MS

10%MS 20%FA+5%MS

30%FA+5%MS 30%FA+10%MS

ig. 6. Dynamic modulus of elasticity of concrete containing cementitious compos-tes.

Fig. 7. Ultrasonic pulse velocity of concrete containing cementitious composites.

3.4. Ultrasonic pulse velocity

Ultrasonic pulse velocity of concrete increased with ages anddecreased with an increase in FA content for a particular MS content(Fig. 7). It is evident that up to 5% MS incorporation in FA concretehas no beneficial effect in increasing Ed over those of control mix.

Generally, the pattern of Ed and V is same, however, in case of Vthe values narrows down difference at later ages. The results clearlydemonstrate that the addition of MS content increased the early-age Ed and V for all types of concrete mixtures. While FA contenthas resulted in an adverse effect on Ed and V at the early-age dueto its delayed hydration. However, at later ages the loss in Ed and Vof FA concrete was compensated for by the addition of MS but onlymixtures with up to 20% FA were able to achieve strength of controlmix. The delayed gain of strength in FA is due to its delayed poz-zolanic reaction (Sarkar et al., 1991). The early loss of the strengthby FA was compensated by the incorporation of MS and the degreeof compensation depended on the quantity of FA and MS incorpora-tion. This is in good agreement with the approach that the problem

R² = 0.70

4.0

4.2

4.4

4.6

4.8

5.0

5.2

5452504846444240

Ult

raso

nic

Puls

e V

eloci

ty, K

m/s

ec

Dynamic Modulus of Elasticity, GPa

Control mix

FA or MS

FA + MS

Fig. 8. Relationship between dynamic modulus and ultrasonic pulse velocity ofconcrete.

M.I. Khan / Resources, Conservation an

R² = 0.60

40

42

44

46

48

50

52

54

120110100908070605040

Dynam

ic M

odulu

s of

Ela

stic

ity, G

Pa

Compressive Strength, MPa

7 days 28 days

90 days 180 days

Fig. 9. Relationship between and dynamics modulus of elasticity and compressivestrength.

R² = 0.82

4.0

4.2

4.4

4.6

4.8

5.0

5.2

120110100908070605040

Ult

raso

nic

Puls

e V

eloci

ty, K

m/s

ec

Compressive Strength, MPa

7 days 28 days

90 days 180 days

Fs

3

atosn(a

V

3

stse

E

ig. 10. Relationship between and ultrasonic pulse velocity and compressivetrength.

.5. Relationship between Ed and V

Both Ed and V are related to the density of hardened pastend the aggregate. An attempt has been made to develop rela-ionship between ultrasonic pulse velocity and dynamic modulusf elasticity. The values of V against Ed have been plotted ashown in Fig. 8. The outlier data point shown on the graph hasot been included in the relationship. The relationship between Vkm/s) and Ed (GPa) fitted a regression line and the expressions iss follows:

= 0.3E0.70d (6)

.6. Relationship between Ed and strength

The Ed values of concrete were plotted against compressivetrength (Fig. 9). The compressive strength results have beenaken from elsewhere (Khan and Lynsdale, 2002). The relation-

hip between Ed (GPa) and compressive strength, fcu (MPa) fittedxpressions as follows:

d = 22f 0.175cu (7)

d Recycling 61 (2012) 125– 129 129

This correlation is similar in nature to that of ultrasonic pulsevelocity but R-value is low. But it is evident from Fig. 9 higherstrength values are more correlated than that of lower values ofstrength.

3.7. Relationship between V and strength

The V values of concrete plotted against compressive strengthvalues at various ages are presented in Fig. 10. The relation-ship between ultrasonic pulse velocity, V (km/s), and compressivestrength, fcu (MPa) fitted expressions as follows:

V = 1.92f 0.20cu (8)

It is evident that the pattern of regression lines of concrete con-taining FA and/or MS is similar to that between Ed and V. Therefore,it can be concluded that the influence on ultrasonic pulse veloc-ity are fairly correlated to the compressive strength irrespective ofconcrete containing FA and/or MS.

4. Conclusions

The incorporation of fly ash resulted in a marginal reduction inthe sorptivity, dynamic modulus of elasticity and ultrasonic pulsevelocity values, especially at later ages. However, the use of fly ashis viable when economical and environmental benefits are soughtgiven the level of performance achieved.

The incorporation of 5% MS has no significant effect on sorptiv-ity, modulus of elasticity and ultrasonic pulse velocity but the rateof gain is significantly increased with 10% MS replacement leveland above 12% incorporation the reductions were marginal.

The results demonstrate that that there is an interactionbetween fly ash and microsilica, with their level of replacementand the age of curing.

Relationships between permeability vs sorptivity and porosityvs sorptivity are reasonably correlated to each other.

Based on the experimental results, some significant correlationswere obtained among the properties investigated in this study. Ithas been found that NDT is reasonably good and reliable tool tomeasure the property of concrete and gives fair indication of thecompressive strength development.

Acknowledgement

The author extends his appreciation to the Deanship of ScientificResearch at King Saud University for funding the work through theresearch group project No. RGP-VPP-105.

References

FIP Report. Condensed Silica Fume in Concrete, FIP State-of-Art Report. London: FIPCommission of Concrete, Thomas Telford House; 1988.

Hall C. Magazine of Concrete Research 1989;41(147):51–61.Khan MI. Journal of the Transportation Research Board 2010(2141):21–7.Khan MI, Lynsdale CJ. Cement and Concrete Research 2002;32:125–33.Malhotra VM, Mehta PK. Pozzolanic and Cementitious Materials—Advances in Con-

crete Technology. Netherlands: Gordon and Breach; 1996.Mehta RK, Gjorv OE. Cement and Concrete Research 1982;12(5):587–95.Nagataki S, Ujike I. Air permeability of concretes mixed with fly ash and condensed

silica fume. In: Proc., Int. Conf. Fly Ash, Silica Fume, Slag, and Natural Pozzolansin Concrete, ACI, SP 91; 1986. p. 1049–68.

Sarkar S, Baalbaki M, Aitcin PC. Cement Concrete and Aggregates 1991;13(2):81–7.

Siddique R, Khan MI. Supplementary Cementing Materials. Germany: Springer-Verlag; 2011.

Weng JK, Langan BW, Ward MA. Canadian Journal of Civil Engineering1997;24:754–60.

Zhang MH, Gjorv OE. Cement and Concrete Research 1991;21(6):1006–14.