Determination of Mean Grain Size of Various Marbles from Turkey by Ultrasonic, Attenuation and Polarize Microscopy Methods

İsmail H. SARPÜN1, Vildan ÖZKAN2,*, Sabri TUNCEL3

1Afyon Kocatepe University, Physics Dept., Afyonkarahisar, Turkey; e-mail: isarpun@gmail.com2Muş Alparslan University, Science Faculty Physics Dept., Muş, Turkey

Phone: +90 436 213 00 13, Fax: +90 436 213 00 54; e-mail: vozkan44@hotmail.com, v.ozkan@alparslan.edu.tr3TUBITAK Marmara Research Center, Gebze, Turkey; e-mail: Sabri.Tuncel@mam.gov.tr

AbstractThe ultrasonic non-destructive testing technique continues to cover new materials at different test conditions, different testing techniques and higher accuracy, sensitivity and reliability. A detailed examination of the mechanical properties of various types of marble is attempted in the present experimental study with the aid of the non- destructive method of ultrasounds. In this work, sixteen marble samples classified into three groups according to their formations have been studied to evaluate the grain size with ultrasonic methods. Ultrasonic velocity and attenuation values have been measured by using probes of 2 MHz and 4 MHz and their relationship with the grain sizes have been examined. It has been found that there is a linear relation between experimental and evaluated mean grain size in all marble groups.

Keywords: Marble, Ultrasonic velocity, Ultrasonic attenuation, Mean grain size.

1. Introduction

The marbles having small grain size, dominant grain size distribution in a narrow range, and irregular grain boundary are more resistant against the ageing tests than the ones with large grain size, grain size distribution in a wide range, and straight grain boundary. Marble is no less complex; it is a product of metamorphism of limestone beds subjected to heat and/or pressure. It appears to be only anisotropic. Marble was extensively used for the construction of common buildings and the hardening of monuments and sculptures from ancient times. The very good physical and mechanical properties of marble, such as its high resistance to abrasion, translucence and capability to be polished, as well as its high strength and hardness render it one of the most widely used structural materials even today for the construction of both buildings and sculptures.

Ultrasonic testing of marbles has been examined by several researchers and all of them observed that the ultrasonic technique is suitable and accurate enough to detect chemical and structural anomalies and discontinuities in marble material [1-7]. One of the non-destructive physical methods with most acceptance and applications in the study of the structural characteristics and mean grain size formation of marbles is the determination of the propagation velocity of ultrasonic waves [8-10]. Mean grain size determinations of marbles have been obtained by ultrasonic velocity [11] and ultrasonic relative attenuation methods[12].

In this work, we have studied the mean grain size determination of some marbles using ultrasonic velocity measurements, ultrasonic attenuation and the ultrasonic relative attenuation (URA) method. The samples were collected from different regions of Turkey and they were separated into three groups. We have determined the mean grain size of marbles by using velocity-grain size, attenuation-grain size and echo height-grain size graphs. These values have been compared with results obtained by polarize microscope images.

5th Pan American Conference for NDT 2-6 October 2011, Cancun, Mexico

2. Materials and Methods

2.1. Samples

Marble samples have been collected from different regions of Turkey (Fig. 1). Thicknesses of the samples varied from 9 mm to 12 mm with a front surface dimension of 5×5 cm2. Front surface of all samples has been manufacturely polished and therefore roughness has been eliminated. Marble samples classified into three groups according to formations:

i. Sedimentary marbleii. Metamorphic marble

iii. Travertine marble

Figure 1. Distribution of selected marble samples in Turkey.

2.1.1. Sedimentary Marble Samples

Sedimentary marbles are composed largely of quartz with other common minerals including feldspars, amphiboles, clay minerals, sandstone with quartz, limestone and sometimes more exotic igneous and metamorphic minerals. They contain fossils, the preserved remains of ancient plants and animals. Sedimentary rocks are economically important since they can be used as construction material. The polarized microscopy images of studied sedimentary samples are shown in Fig. 2.

(S1) (S2) (S3)

(S4) (S5) (S6)

Figure 2. Polarized microscopy images of sedimentary marble samples (S1) Akhisar Onyx, (S2) Bursa Beige-Grey, (S3) Toros Beige-Crema, (S4) Hazar Pink, (S5) Bilecik Pink, (S6) Vize Pink.

2.1.2. Metamorphic Marble Samples

Marble is generally a metamorphic rock resulting from regional or contact metamorphism of sedimentary carbonate rocks, either limestone or dolostone. This metamorphic process causes a complete recrystallization of the original rock into an interlocking mosaic of calcite and/or dolomite crystals. The temperatures and pressures necessary to form marble usually destroy any fossils and sedimentary textures present in the original rock. The sedimentary marble samples’ polarized microscopy images are given in Fig. 3.

(M1) (M2) (M3)

(M4) (M5) (M6)

Figure 3. Polarized microscopy images of metamorphic marble samples (M1) Afyon Kaymak, (M2) Afyon Tigerskin, (M3) Manyas Beige, (M4) Marmara Adası, (M5) Afyon Striped Sugar, (M6) Eskişehir

Süpren.

2.1.3. Travertine Marble Samples

Travertine is a terrestrial sedimentary rock, formed by the precipitation of carbonate mineralsfrom geo-thermally heated hot-springs. Travertine is often used as a building material. It is sometimes known as travertine limestone, sometimes as travertine marble; these are the same

stone, even though it is neither limestone nor marble. The travertine marble samples studied in the present work are shown in Fig. 4.

(T1) (T2)

(T3) (T4)

Figure 4. Polarized microscopy images of travertine marble samples (T1) Sivas Yellow Travertine, (T2) Antalya-Finike, (T3) Balıkesir Light Pink, (T4) Denizli Travertine.

2.2. Ultrasonic Measurements

The determination of transmission velocity of ultrasonic waves through the marbles were performed by a Sonatest Sitescan 150 pulser/receiver instrument with Sonatest SLH2-10 and Sonatest SLH4-10 transducer operated at the frequency of 2 MHz-4MHz at the room temperature. Sonatest sonagel-W was used as interface between the transducers and marbles, given the smoothness of the marble surfaces. Velocities of ultrasound wave passing through the samples have been measured six times and the mean values are given in Table 1. The velocity values were obtained directly from knowledge of the properties of the flaw detector.According to the ultrasonic attenuation method, the amplitudes of successive backwall echoes are used to determine the attenuation coefficient of marbles. In this work, ratio of the amplitudes of the first back-wall echo to that of the second back-wall echo were used to calculate attenuation coefficient as follows:

� =�

�20���

��

�� (1)

where A1 and A2, are the amplitudes of successive reflected ultrasonic wave from the materials surface [13]. A modified URA (Ultrasonic Relative Attenuation) method was also applied to samples, which is given by [12]. According to this method the rate of peak heights was used to determine mean grain size of samples. The mean grain sizes of marbles were determined experimentally using LV100 50i POL model polarized light microscopy. The images of marbles were taken by changing magnification of the polarized light microscope. Later, mean grain size was calculated by using software with polarized microscopy.

3. Results

3.1. Experimental Works

The mean values of the velocity, attenuation coefficient and rate of peak heights in the three types of marbles were given in Table 1 with mean grain size of samples.

Table 1. Mean values of ultrasonic longitudinal velocity, ultrasonic attenuation and rate of peak heights in sedimentary, metamorphic and travertine marble samples by 2 MHz probe,

mean grain size of samples.

Samples Velocity (m/sn)Attenuation

(dB/mm)Rate of peak

heights

Mean Grain Size (m)

Sed

imen

tary

S1 5277.83 1.719 7.38 252.94

S2 6497.33 0.838 2.65 143.37

S3 6586.67 0.517 2.04 135.66

S4 6294.67 0.724 2.30 175.93

S5 6023.33 1.058 3.38 186.76

S6 6788.33 0.539 1.85 118.63

Met

amor

ph

ic

M1 3513.00 1.982 9.80 299.77

M2 4096.33 2.165 11.80 273.33

M3 5876.50 0.833 3.16 169.68

M4 4505.50 1.270 4.32 223.85

M5 5470.50 0.790 2.55 138.48

M6 5687.17 0.730 2.13 142.97

Tra

vert

ine T1 5263.00 1.995 9.50 112.75

T2 4066.50 2.260 12.80 133.58

T3 4805.83 2.132 10.60 113.88

T4 5063.00 1.386 6.79 77.22

3.2. Reference Graphs

In ultrasonic methods reference graphs have to be plotted to determine the mean grain size of samples. The reference graph could be plotted by two ways: the first way is to use reference sample and the second is to use different probes to carry out measurements from another region of sample. In this paper second way has been used to plot reference graph of samples because of anisotropic properties of marbles. The reference graph for the ultrasonic velocity method was plotted using the values from Table 1 as shown in Fig. 5.

One can see from the Fig 5, Sedimentary marble samples’ correlation coefficient is higher than the other samples in ultrasonic velocity method. The reference graph for the ultrasonic attenuation method was plotted using the values from Table 2 as shown in Fig. 6.

Figure 5. Reference graph of marble samples according to ultrasonic velocity method.

Figure 6. Reference graph of marble samples according to ultrasonic attenuation method.

In Fig. 6, fitting line of travertine marbles has the highest correlation coefficient where sedimentary marbles have the lowest. This is due to the nature of attenuation of ultrasonic waves which has lower attenuation coeficient, will have higher velocity values. The URA values of marble samples are shown in Fig. 7 which was plotted using the values from Table 1.

Figure 7. Reference graph of marble samples according to modified URA method.

y = -11.1x + 8118.8R² = 0.9864

y = -13.391x + 7643.7R² = 0.9123

y = -14.909x + 6430R² = 0.4468

10

100

1000

10000

25 75 125 175 225 275 325Ult

raso

nic

Ve

loci

ty (

m/s

)

Mean Grain Size (m)

Sedimentary/100Metamorphic/10Travertine

y = 0.0088x - 0.5839R² = 0.8966

y = 0.0089x - 0.5576R² = 0.9229

y = 0.0161x + 0.1812R² = 0.9546

1

10

100

1000

10000

25 75 125 175 225 275 325Ult

raso

nic

Att

en

uat

ion

(d

B/m

m)

Mean Grain Size (m)

Sedimentary x 1000Metamorphicx x 100Travertine x 10

y = 0.04x - 3.4893R² = 0.8616

y = 0.0554x - 5.9068R² = 0.8488

y = 0.1041x - 1.4669R² = 0.9564

1

10

100

1000

25 75 125 175 225 275 325

Pe

ak H

eig

th R

ate

Mean Grain Size (µm)

Sedimentary x 100Metamorphic x 10Travertine

The URA and ultrasonic attenuation methods depend on the rate of screen height of peaks. The main difference between these two methods is in URA method all the samples have to have the same thickness, but not in attenuation method. Because of this, correlation factors have the same range with attenuation method.

3.3. Evaluation of Mean Grain Size

In all methods fitting equations were used to evaluate the mean grain size of samples. Ultrasonic values have been measured 6 times using 4 MHz probe and the mean values have been used in calculations. The ultrasonic methods have been compared in the separate graphs for each marble group. Both ultrasonic measurement results obtained using 4 MHz probe and the evaluated mean grain size of samples were given in Table 2 for sedimentary marble samples. The comparison of the experimental and the evaluated mean grain size results have been shown in Fig. 8.

Table 2. Evaluated mean grain size of sedimentary marble samples by using 4 MHz probe.

Sedimentary S1 S2 S3 S4 S5 S6Experimental Mean

Grain Size (µm)252.94 143.37 135.66 175.93 186.76 118.63

Vel

oci

ty

Velocity4 MHz (m/s)

5343.83 6304.50 6384.67 6198.67 6028.17 6436.00

Evaluated Mean Grain Size (µm)

249.99 163.45 156.23 172.98 188.35 151.6

Δ (grain size) 2.95 20.08 20.57 2.95 1.59 33.24

Att

enu

atio

n Attenuation4MHz (dB/mm)

1.704 0.545 0.591 0.718 1.204 0.636

Evaluated Mean Grain Size (µm)

259.98 128.28 133.51 147.94 203.17 138.63

Δ (grain size) 7.04 15.09 2.15 27.99 16.41 20.00

UR

A

Rate of Screen Heights 4 MHz

7.25 1.88 2.26 2.29 4.00 2.06

Evaluated Mean Grain Size (µm)

268.48 134.23 143.73 144.48 187.23 138.73

Δ (grain size) 15.54 9.14 8.07 31.45 0.47 20.1

Figure 8. Comparison of experimental and evaluated mean grain size of sedimentary marbles.

R² = 0.9525

R² = 0.8738

R² = 0.86910

100

1000

10000

100000

100 150 200 250Eval

uat

ed

Me

an G

rain

Siz

e

(m

)

Experimental Mean Grain Size (m)

Sedimentary

Velocity

Attenuation x 10

URA x 100

The evaluated values obtained using 4 MHz probe are given in Table 3 and the comparison of the mean grain sizes are shown in Fig. 9, for metamorphic marble samples.

Table 3. Evaluated mean grain size of metamorphic marble samples by using 4 MHz probe.

Metamorphic M1 M2 M3 M4 M5 M6Experimental Mean

Grain Size (µm)299.77 273.33 169.68 223.85 138.48 142.97

Vel

ocit

y

Velocities4 MHz (m/s)

3447 4228.33 6022.67 4501 5612.33 5464.50

Evaluated Mean Grain Size (µm)

313.39 255.05 121.05 234.69 151.69 162.74

Δ (grain size) 13.62 18.28 48.63 10.84 13.21 19.77

Att

enu

atio

n Attenuation4MHz (dB/mm)

2.000 1.787 0.866 1.665 0.918 0.649

Evaluated Mean Grain Size (µm)

287.37 263.44 159.96 249.73 167.79 135.57

Δ (grain size) 12.40 9.89 9.72 25.88 29.31 7.40

UR

A

Rate of Screen Heights 4 MHz

10.00 7.67 3.31 7.33 2.97 1.96

Evaluated Mean Grain Size (µm)

287.13 245.07 166.37 238.93 160.23 142.00

Δ (grain size) 12.64 28.26 3.31 15.08 21.75 0.97

Figure 9. Comparison of mean grain sizes of metamorphic marble samples.

The evaluated values measured by 4 MHz probe are given in Table 4 and the comparison of experimental and evaluated mean grain sizes of samples are given in Fig. 10, for travertine marble samples.

R² = 0.8675R² = 0.9205

R² = 0.944210

100

1000

10000

100000

125 150 175 200 225 250 275Eval

uat

ed

Me

an G

rain

Siz

e (

m)

Experimental Mean Grain Size (m)

Metamorphic

Velocity

Attenuation x 10

URA x 100

Table 4. Evaluated mean grain size of travertine marble samples by using 4 MHz probe.

Travertine T1 T2 T3 T4

Experimental Mean Grain Size (µm)

112.75 133.58 113.88 77.22V

elo

city

Velocity4 MHz (m/s)

5041.33 3532.83 4896 5234.17

Evaluated Mean Grain Size (µm)

93.14 194.32 102.89 80.21

Δ (grain size) 19.61 60.74 10.99 2.99

Att

enu

atio

n Attenuation4MHz (dB/mm)

1.736 1.928 1.946 1.645

Evaluated Mean Grain Size (µm)

96.57 108.49 109.61 90.92

Δ (grain size) 16.18 25.09 4.27 13.70

UR

A

Rate of Screen Heights 4 MHz

7.09 8.80 8.33 9.70

Evaluated Mean Grain Size (µm)

82.19 98.63 94.11 107.27

Δ (grain size) 30.56 34.95 19.77 30.05

Figure 10. Comparison of experimental and evaluated mean grain sizes of travertine marble samples.

4. Conclusion

According to Table 2, the difference between the experimental and the evaluated values reaches up to 20%. The ultrasonic velocity measurements have the highest correlation coefficient of 0.9525 for Sedimentary marble samples. One can see from the Table 3, the difference between the experimental and the evaluated values for metamorphic marble samples is 20% which is similar to sedimentary marble samples. According to Fig 9, the highest correlation coefficient is seen in the URA method for metamorphic marble samples. According to Table 4, the difference between the experimental and the evaluated values for

R² = 0,6333

R² = 0,6763R² = 0,231610

100

1000

10000

100000

70 80 90 100 110 120 130 140 150

Eval

uat

ed

Me

an G

rain

Siz

e (

m)

Experimental Mean Grain Size (m)

Travertine

VelocityAttenuation x 10URA x 100

travertine marble samples goes up to 50%. This is due to the porosity structure of travertine marble samples. Also all the correlation coefficients are low.

One can compare three marble groups by their ultrasonic properties. The correlation coefficients of metamorphic marble samples are higher than the others and also travertine marble samples are not suitable because of their porosity structure. Besides, as the mean grain size decrease, the ultrasonic velocity and the rate of heights of successive peaks increase whereas the ultrasonic attenuation coefficient decreases.

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