Digest 2006, December 2006 1075-1088

Determining the Engineering Properties of Bentonite – Zeolite Mixtures†1 Abidin KAYA* Seda DURUKAN** A.Hakan ÖREN*** Yeliz YÜKSELEN**** ABSTRACT In this study, as an alternative to bentonite-embedded sand, bentonite-embedded zeolites with different bentonite content were investigated for possible use of landfill liner. For this, cation exchange capacity (CEC) of Na-bentonite and zeolite; volumetric shrinkage, compaction characteristics; and hydraulic conductivity of the mixtures were investigated. Considering the zero adsorption capacity of sand, the practical implication of high CEC of zeolite is remarkable. Hydraulic conductivity tests on bentonite embedded zeolite with 10% and 20% bentonite content show that the hydraulic conductivity of both mixtures are less than 1*10-9 m.s-1, which meets the common regulatory requirements. Moreover, the test results reveal that variations in hydraulic conductivity of the mixtures with different stress conditions are negligible for practical purposes. 1. INTRODUCTION

Development of alternative landfill liner material is an active research area. The requirement of a good landfill liner material is its durability and low hydraulic conductivity under various environmental conditions. In the developed countries, man made materials such as geomembranes are integrated along with clayey based liners to fulfill this requirement. However, use of man made materials is not considered as alternative material for developing countries such as Turkey for two reasons: (i) its relatively high cost and (ii) long term problems intrinsic to geomembranes. Thus, researchers in developing countries are in the search of developing cost effective natural landfill liner materials that can be used effectively for confining waste materials. In the area of landfill liner material development Turkish researchers indicate that zeolite embedded bentonite can be used as alternative landfill liner material. This is because both zeolite and bentonite are natural and abundant throughout Turkey. The idea behind using zeolite is that it will act as a filter in the event of

* Hawaii Department of Transportation, - abidin.kaya@hawaii.gov ** Celal Bayar University, Manisa, Turkey - seda.durukan@bayar.edu.tr *** Dokuz Eylül University, İzmir, Turkey - ali.oren@deu.edu.tr **** Dokuz Eylül University, İzmir, Turkey - yeyukselen@yahoo.com † Published in Teknik Dergi Vol. 17, No. 3 July 2006, pp: 3879-3892

Determining the Engineering Properties of Bentonite – Zeolite Mixtures

1076

leachate through liner due to its high adsorption capacity. Thus, it is worth to study the suitability of using bentonite embedded zeolite as alternative to bentonite embedded sand, which is the subject of this paper. 2. BACKGROUND Several studies have been conducted for various natural materials in order to use as landfill liner and barrier systems. As a result of these studies, typically, a liner is required to have a hydraulic conductivity to be less than or equal to a specified value i.e. ≤ 1.10-9 m/s [1,2,3,4,5,6]. Clays are reasonable materials for a landfill liner with their low hydraulic conductivity and high adsorption capacities. However, results from several studies showed that clays undergo large increases in hydraulic conductivity when exposed to temperature and/or moisture content fluctuations resulting crack formations which led to increase the hydraulic conductivity [7,8,9,10]. Swelling and shrinkage cracking, one of the most encountered problems, must be reduced to a minimum level in order to ensure the integrity of the liner. Kleppe and Olson (1985) established that it required %4-5 volumetric shrinkage to cause significant cracking of mineral liners [11]. Upon the undesired results of clays occurred by the temperature and moisture fluctuations, the idea of blending clays with coarse particles such as sands have been put forward. As an outcome, bentonite, which has the lowest hydraulic conductivity among other clay minerals, and sand mixtures were used. The mixture resulted in success and also no cracks under the effect of related fluctuations were observed. However, regarding the zero adsorption capacity of sands, the hazardous waste adsorption remains far from projected quantities [5,6,11,12,13,14,15]. Another alternative material for clay liners is utilization of geosynthetic clay liners (GCLs). Although GCLs satisfy lower hydraulic conductivities in landfill liner applications, they are not suggested because of their high cost [4,12,16,17,18,19,20]. This is because hydraulic conductivity of GCLs may change by the chemical attacks while permeation [4,20,21,22,23]. Studies on bentonite embedded sand (BES) and GCLs showed that hydraulic conductivities of these materials may increase when permeated with chemicals or waste liquids. Thereupon, bentonite embedded zeolite (BEZ) was proposed as an alternative to bentonite embedded sand (BES) and GCLs. Based on the studies on BEZ, it was reported that BEZ can also satisfy lower hydraulic conductivity values when compared to BES and GCLs. However, it should be considered that these studies are limited and the test conditions may not be represented the real conditions [1,2,3,24]. Thus, utilization of zeolite which has high adsorption capacity at least of clays is proposed instead of sand for landfill liner applications. Hence, the mixture of bentonite and zeolite are subjected to laboratory tests in order to determine the required engineering parameters. Zeolite is a tecto-silicate and in contrast to other tecto-silicates such as feldspar and quartz, the zeolite framework is remarkably open and has an infinite, three dimensional system of a tunnels and cages. This system is adequate for holding the molecules larger than these channels and/or tunnels and zeolites are called as “molecular sieves”. Five types of natural zeolites were defined according to their commercial interests. These are: clinoptilolite, chabazite, mordenite, erionite and phillipsite. Natural zeolites occur in different geological

Abidin KAYA, Seda DURUKAN, A.Hakan ÖREN, Yeliz YÜKSELEN

1077

settings as rock-forming minerals in many locations in the world. Turkey is one of the important settings of zeolite deposits with large and rich reserves. Bigadiç reserve is one of the considerable example; the others are in Ankara Polatlı Mülk Oğlakçı area, Şaphane, Gediz, Emet ve Gördes areas [25,26,27]. The zeolites, which are cost effective materials and can be found in large quantities in Turkey, were evaluated experimentally by means of bentonite-zeolite mixtures and the obtained results are summarized below. 3. MATERIALS AND METHOD In this study, bentonite embedded zeolite (BEZ) and bentonite embedded sand (BES) were used. The mixtures were prepared with a proportion of bentonite ranging in 3%, 5%, 10% and 20% of total weight. Zeolite was obtained from Bigadiç reserves; whereas, bentonite was supplied from Marmara Concord, Balıkesir. Sand was provided from Soil Mechanics laboratory of Dokuz Eylül University, Kaynaklar Campus, Buca, İzmir. Liquid limit (fall cone test), plastic limit, shrinkage limit, specific gravity, standard Proctor compaction test, volumetric shrinkage strain and consolidation tests were applied according to ASTM standards for each mixture [28]. Hydraulic conductivity of mixtures which were compacted at their optimum moisture contents were obtained by using one-dimensional consolidation test apparatus. Volumetric shrinkage strain of compacted samples (with standard compaction method - with varying moisture contents) was obtained by determining the volume change during air-drying and oven drying. Volumetric shrinkage strains were determined only for the samples compacted at their optimum molding moisture contents. 4. RESULTS The experiments on the consistency limits and optimum compaction criteria for all Na-bentonite – zeolite and Na-bentonite – sand mixtures were conducted. For sand – bentonite mixtures it was unable to determine the volumetric shrinkage strain values because of the structural properties of the mixtures. Also, no significant consolidation behavior was observed for mixtures of 3% and 5% both zeolite-bentonite and sand-bentonite; and for 10% sand-bentonite mixture. Therefore, hydraulic conductivity values held from consolidation tests were determined for 10% and 20% zeolite-bentonite and 20% sand-bentonite mixtures. The specific gravity values of zeolite, bentonite and sand were determined as 2.39 t/m3 , 2.71 t/m3 and 2.61 t/m3 and also cation exchange capacity of these materials are determined as 40 meq/100gr, 104.4 meq/100gr, and 0 meq/100gr, respectively. 4.1 Consistency Limits

The results of liquid limit (LL), plastic limit (PL), and shrinkage limit (SL) tests for all mixtures are presented in Table 1. For both mixtures it is seen that the liquid limit, plastic limit, shrinkage limit and also the plasticity index increases while the proportion of bentonite increases. The effect of the bentonite content on the consistency limits is better illustrated in Figures 1, 2 and 3. The mixtures of 3%, 5%, 10% BES and 3% BEZ have no plasticity.

Determining the Engineering Properties of Bentonite – Zeolite Mixtures

1078

Table 1. Consistency Limits Tests Results

Soil LL (%) PL (%) SL (%) PI (%)

Sand * NP * NP

Bentonite 210 52 * 118

Zeolite 42 NP * NP

%3 BEZ 45 NP * NP

%5 BEZ 48 32 36 16

%10 BEZ 54 33 38 21

%20 BEZ 61 35 40 26

%3 BES 30 NP * NP

%5 BES 32 NP * NP

%10 BES 41 NP * NP

%20 BES 54 27 25 27

* Couldn’t be determined. NP; Non-Plastic

Figure 1. Variation of Liquid limit With Respect to Bentonite Content

20

40

60

80

0 5 10 15 20 25

Bentonite (%)

LL (%

)

LL (BEZ)LL (BES)

Abidin KAYA, Seda DURUKAN, A.Hakan ÖREN, Yeliz YÜKSELEN

1079

Figure 2. Variation of Plastic Limit and Plasticity Index With Respect to Bentonite Content

Figure 3. Variation of Shrinkage Limit With Respect to Bentonite Content

10

20

30

40

50

0 5 10 15 20 25

Bentonite (%)

PL, P

I (%

)

PL (BEZ)PI (BEZ)

35

37

39

41

0 5 10 15 20 25

Bentonite (%)

SL (%

)

SL (BEZ)

Determining the Engineering Properties of Bentonite – Zeolite Mixtures

1080

4.2 Compaction Properties Compaction tests were conducted on all BEZ and BES samples. The zero air void ratio and the 85% saturation lines were drawn by using the specific gravities of zeolite and sand with BEZ and BES samples, respectively. The compaction curves of BEZ and BES samples can be seen in Figures 4 and 5, respectively. It is seen that with increasing the bentonite content, optimum water content increases while the dry unit weight decreases. This is the expected behavior and is because of the activity (A) of bentonite. The adsorbed water film around the clay particles have volume that increases the water content and decreases the dry unit weight. However, the increase in optimum water content or decrease in dry unit weight is negligible for all practical purposes. The compaction characteristics of BEZ and BES are represented in Table 2.

1,10

1,15

1,20

1,25

1,30

1,35

20 25 30 35 40 45 50Molding Moisture Content (%)

Dry

Uni

t Wei

ght (

t/m3 )

3% BEZ5% BEZ10% BEZ20% BEZZeolite

S = 100%S = 85%

Figure 4. The Compaction Curves of BEZ Samples

Gs=2.45 20% BEZ

Gs=2.39 zeolite

Gs=2.45 20% BEZ

Gs=2.39 zeolite

Abidin KAYA, Seda DURUKAN, A.Hakan ÖREN, Yeliz YÜKSELEN

1081

1,50

1,60

1,70

1,80

1,90

2,00

5 10 15 20 25 30

Molding Moisture Content (%)

Dry

Uni

t Wei

ght (

t/m3 )

3% BES5% BES10% BES20% BESSand

S=85% S=100%

Figure 5. The Compaction Curves of BES Samples

Table 2. Compaction Characteristics of BEZ and BES Samples

BEZ

Bentonite 3% 5% 10% 20%

Optimum Moisture Content (%) 33 34 36 37

Dry Unit Weight (t/m3) 1.29 1.27 1.25 1.23

BES

Bentonite 3% 5% 10% 20%

Optimum Moisture Content (%) 13 14 15 16

Dry Unit Weight (t/m3) 1.85 1.79 1.76 1.72

4.3 Volumetric Shrinkage Strain The volumetric shrinkage strain (given in Equation 1.) values couldn’t be determined for BES samples in this study. The volumetric shrinkage strain values of BEZ are represented in Figure 6. The optimum moisture contents are 36% and 37% for 10% BEZ and 20% BEZ, respectively. Samples when used at their optimum moisture contents seem far from 5% volumetric shrinkage limit according to Kleppe and Olson (1985). In other words, mixtures used at their optimum moisture contents don’t have any shrinkage risk. The molding

Gs=2.63 20% BES

Gs=2.63 20% BES

Gs=2.61 sand Gs=2.61

sand

Determining the Engineering Properties of Bentonite – Zeolite Mixtures

1082

moisture content of each mixture at 4% volumetric shrinkage and the volumetric shrinkage at optimum moisture contents are given in Table 3 [11].

Volumetric shrinkage strain =0VV∆

(1)

V represents volume change; V0 represents initial volume.

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

0 10 20 30 40

Moisture Content (%)

Volu

met

ric S

hrin

kage

Str

ain

(%)

10% BEZ20% BEZ

Figure 6. Volumetric Shrinkage Strain of BEZ Samples

Table 3. Volumetric Shrinkage Strain Values of BEZ

TEST SAMPLES 10% BEZ 20% BEZ Moisture Content (%)

at 4% Volumetric Shrinkage 60 54

Volumetric Shrinkage (%) at Optimum Moisture Content

2,4 2,75

4.4 Consolidation Parameters and Hydraulic Conductivity Although hydraulic conductivity tests should be conducted by using a triaxial permeameter, with the absence of this test apparatus one dimensional consolidation test apparatus are used to obtain hydraulic conductivity. The consolidation tests to determine the hydraulic conductivity were conducted just on 10% & 20% BEZ and 20% BES samples. The final hydraulic conductivity values of samples are represented in Table 4. The variation of

Abidin KAYA, Seda DURUKAN, A.Hakan ÖREN, Yeliz YÜKSELEN

1083

hydraulic conductivity (k-m/s) with respect to void ratio (e) for each mixture can be seen in Figure 7 [29,23] . One of the most probable shortcomings of determining the hydraulic conductivity by using one-dimensional consolidation test apparatus is probable sidewall leakage between the ring and the test sample. In order to obtain both any sidewall leakage existence and the variation of hydraulic conductivity with respect to vertical pressure; the behavior of 20% BEZ under varying vertical pressure conditions was investigated and the results are represented in Table 5. Also, during tests no sitting pressure was applied to determine if there were any effects of swelling on compacted specimens.

Table 4. Hydarulic Conductivity Parameters of Test Samples

Test Sample 10% BEZ 20% BEZ 20% BES

k final (m/s) 2.69*10-11 4.33*10-11 4.81*10-11

Final void ratio, e 0.7552 0.7769 0.5879

Initial void ratio, e 1.0125 1.0333 0.8662 e 0.2573 0.2564 0.2783

Figure 7. Variation of Hydraulic Conductivity With Respect to Void Ratio

Table 5. Hydraulic Conductivity Values of 20% BEZ Under Varying Initial Pressures

Pressure (kg/cm2) 0,25 0,50 1,00 2,00 Standard Test*

Kinitial (m/s) 2,26E-10 2,88E-10 1,32E-10 1,08E-10 1,39E-10 kfinal (m/s) 5,32E-11 5,57E-11 4,73E-09 7,34E-11 4,33E-11

Kinitial / kfinal 4,2 5,2 2,8 1,5 3,2 *0,07 kg/cm2 (with sitting pressure)

1,0E-12

1,0E-11

1,0E-10

1,0E-09

1,0E-08

0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1

e

k (m

/s)

20% BES

10% BEZ

20% BEZ

Determining the Engineering Properties of Bentonite – Zeolite Mixtures

1084

The hydraulic conductivity test results were practically so close and this indicates that there was no sidewall leakage. Thus, this indicates the fact that no sidewall leakage and swelling were observed even at low pressure conditions. The variation of the hydraulic conductivity values of 20% BEZ samples versus the applied initial pressures are given in Figure 8 and the change of hydraulic conductivity values with respect to the void ratio is presented in Figure 9. As can be seen from Figure 8, almost no change was observed in hydraulic conductivity values with respect to initial pressures. A similar state is valid for hydraulic conductivity versus void ratios (for varying initial pressure) case. In the literature, it is reported that the hydraulic conductivity varies under different vertical pressures. However, no significant difference was observed in the present study [29].

Figure 8. Hydraulic Conductivity of 20% BEZ Under Varying Initial Pressures

Figure 9. Hydraulic Conductivity of 20% BEZ With Respect to Void Ratio

1,0E-12

1,0E-11

1,0E-10

1,0E-09

1,0E-08

0 0,5 1 1,5 2 2,5

Initial pressure (kg/cm2)

k (m

/s)

2 kg/cm2 0,50 kg/cm2

1 kg/cm2

0,25 kg/cm2

0,07 kg/cm2

1,0E-12

1,0E-11

1,0E-10

1,0E-09

1,0E-08

0,700 0,720 0,740 0,760 0,780 0,800

e

k (m

/s)

Abidin KAYA, Seda DURUKAN, A.Hakan ÖREN, Yeliz YÜKSELEN

1085

Based on the above mentioned test results, both BEZ and BES samples have adequate hydraulic conductivity values which are needed for a liner material. Although there is no so much difference between the hydraulic conductivity values of two mixture type of BEZ and BES, BEZ samples have lower hydraulic conductivity than BES samples. It’s seen that compacted BEZ samples are resistant under varying vertical pressure conditions and also resistant to swelling. 5. CONCLUSIONS AND RECOMMENDATIONS Both BES and BEZ are suitable materials for landfill liners; however, considering the cation exchange capacity, one can say that BEZ is superior to BES. Nevertheless, for both mixtures adequate hydraulic conductivity values are achieved and in addition, no shrinkage cracks were observed. Day & Daniel (1985) found that the hydraulic conductivity values of the field are generally higher than the laboratory determined hydraulic conductivity values. However, even if the expected field hydraulic conductivity were a magnitude higher than the laboratory measured value, it still stands with in the acceptable range of hydraulic conductivity for use of a landfill liner material. Furthermore, King et al., (1993) also showed that by time, the hydraulic conductivity of liners may actually decrease [30,31]. It’s emphasized that it would be proper to use tri-axial permeability testing apparatus in order to determine hydraulic conductivity. However, hydraulic conductivity was determined by using an indirect method by one dimensional consolidation test within the facilities. With the absence of backpressure, saturation seems to be a problem. However, compacted clayey samples, which are not back pressured, represent the field liner conditions more realistic than ever. Another problem when using an indirect method of testing hydraulic conductivity is the probable sidewall leakage problem between the ring and the test sample. In the early 1980’s, it was recognized that sidewall leakage might have a significant effect on tests involving clayey materials. However, when the applied vertical stress on the soil specimen increases, the lateral stress of the soil against the inner walls of the cell thereby increases reducing the sidewall leakage. Daniel (1994) showed that sidewall leakage is rarely a problem for compressible soils that have been subjected to compressive stresses of at least 50 kPa or more. However, one should not forget that a liner is not usually under that much large stresses. Therefore, low stress conditions in laboratory tests may be more accurate for modelling of a landfill liner [29]. The results of the volumetric shrinkage test show that shrinkage behavior of BEZ is satisfactory for landfill liner applications. It was seen that there were no visible shrinkage cracks on BEZ samples when compacted at optimum moisture contents and shrinkage cracks occur hardly at very high moisture contents. It’s clear that zeolite is superior over sand in meanings of cation exchange capacity. Consequently, it’s seen that adsorption capacity of BEZ would be higher that that of BES. Both BEZ and BEZ are found to be sufficient enough regarding physical properties as a liner. However, the BEZ mixtures are ascendant, because of their high cation exchange capacity. The field performance of BEZ should be investigated in further studies.

Determining the Engineering Properties of Bentonite – Zeolite Mixtures

1086

SYMBOLS BEZ Bentonite Embedded Zeolite BES Bentonite Embedded Sand CEC Cation Exchange Capacity LL Liquid Limit PL Plastic Limit SL Shrinkage Limit PI Plasticity Index S Saturation Gs Specific Gravity V Volume Change V0 Initial Volume k Hydraulic Conductivity e Void Ratio e Void Ratio Change

References

[1] Güney, Y. & Koyuncu, H., The behavior of bentonite-zeolite landfill versus salt and metal pollution. 6th International Symposium on Geoenvironmental Geotechnology and Global Sustainable Developments, Chung-Ang University, Seoul, Korea, 61-68, 2002.

[2] Kayabalı, K., Engineering aspects of a novel landfill material: Bentonite amended natural zeolite. Engineering Geology, 46, 105-114, 1997.

[3] Kayabalı, K. & Kezer, H., Testing the ability of bentonite amended zeolite (clinoptilolite) to remove heavy metals from liquids waste. Environmental Geology, 34, 95-102, 1998.

[4] Ruhl, J. & Daniel, D.E., Geosynthetic clay liners permeated with chemical solutions and leachates. Journal of Geotechnical and Geoenvironmental Engineering, 123, 369-381,1997.

[5] Stewart, D.I, Cousens, T.W., Studds, P.G., & Tay, Y.Y., Design parameter for bentonite enhanced sand as a landfill liner. Proc. Instn. Civil Engng., October, 137, 189-195, 1999.

[6] Tay, Y.Y., Stewart, D.I. & Cousens, T.W., Shrinkage and dessication cracking in bentonite-sand landfill liners. Engineering Geology, 20, 263-274, 2001.

[7] Benson, C.H., & Othman, A.M., Hydraulic conductivity of compacted clay frozen in situ. J. Geotech. Engng., ASCE, 119(2), 276-294, 1993.

[8] Chamberlain, E.J., Erickson, A., & Benson, C., Effects of frost action on compacted clay barriers. Geoenvironment 2000, ASCE, New York, N.Y., 46, 702-717, 1995.

[9] Chamberlain, E.J., Iskender, I., & Hunsiker, S.E., Effect of freeze thaw on the permeability and macrostructure of soils. Proceedings, International Symposium on Frozen Soil Impacts on Agricultural, Range, and Forest Lands, March 21-22, Spokane, WA, 145-155, 1990.

[10] Othman, M., Benson, C., Chamberlain, E., & Zimmie, T., Laboratory testing to evaluate changes in hydraulic conductivity caused by freeze-thaw: state-of-the-art.

Abidin KAYA, Seda DURUKAN, A.Hakan ÖREN, Yeliz YÜKSELEN

1087

Hydraulic Connductivity and Waste Contaminant Transport in Soils, ASTM, STP, 1142, 227-254, 1994.

[11] Kleppe, J. H. and Olson, R.E., Desiccation cracking of soil barriers. ASTM, Special technical Publication, 874, 263-275, 1985.

[12] Kraus, J.F., Benson, C.F., Erickson, A.E., & Chamberlain, E.J., Freeze thaw cycling and hydraulic conductivity of bentonitic barriers. Journal of Geotechnical and Geoenvironmental Engineering, 123(3), 229-238, 1997.

[13] Shan, H.-Y. & Daniel, D.E., Reults of laboratory tests on a geotextile-bentonite liner material. Proc., Geosynthetics ’91 Industrial Fabrics Association International, St. Paul, Minn., 517-535, 1991.

[14] Sivapullaiah, P.V., Sridharan, A. & Stalin, V.K., Hydraulic conductivity of bentonite-sand mixtures. Canadian Geotech. J., 37, 406-413, 2000.

[15] Villar, M.V. & Rivas, P., Hydraulic properties of montmorillonite-quartz and saponite-quartz mixtures. Applied Clay Science, 9, 1-9, 1994.

[16] Daniel, D.E., Geosynthetic clay liners. Geotechnical News, 9(4), 28-33, 1991. [17] James, A.N., Fullerton, D. & Drake, R., Field performance of GCL under ion

exchange conditions. Journal of Geotechnical and Geoenvironmental Engineering, 123, 897-901, 1997.

[18] Lin, L.-C. & Benson, C.H., Effect of wet-dry cycling on swelling and hydraulic conductivity of GCLs. Journal of Geotechnical and Geoenvironmental Engineering 126, 40-49, 2000.

[19] Shackelford, C.D., Benson, C.H., Katsumi, T., Edil, T.B. & Lin, L., Evaluating the hydraulic conductivity of GCLs permeated with non-standard liquids. Geotextiles and Geomembranes, 18, 133-161, 2000.

[20] Shan, H.-Y. & Lai, Y.-J., Effect of hydrating liquid on the hydraulic properties of geosynthetic clay liners. Geotextiles and Geomembranes, 20, 19-38, 2002.

[21] Alther, G.R., Evans, J.C., Fang, H.-Y. & Witmer, K., Influence of organic permeants upon permeability of bentonite. Hydraulic Barriers in Soil and Rock, ASTM, STP, 874, 64-73, 1985.

[22] Kaya, A., & Fang, H.-Y., The effects of organic fluids on physicochemical parameters of fine grained soils. Canadian Geotechnical Journal, 37, 943-950, 2000.

[23] Olson, R.E., & Daniel, D.E., Measurement of the hydraulic conductivity of fine grained soils. Permeability and Groundwater Contaminant Transport, ASTM STP, 746, 18-64, 1981.

[24] Durukan, S., A study on physicochemical properties of bentonite embedded zeolites, Dokuz Eylül Üniversitesi, Yüksek Lisans Bitirme Projesi, 2002.

[25] Ataman, G., Batı anadolu zeolitleri oluşumları. Yerbilimleri, 3, 85-94, 1997. [26] Baysal, O., Gündoğdu, N., Temel, A., & Öner, F., Bigadiç zeolit oluşumlarının

ekonomik, jeolojik incelenmesi projesi. H.U. YUVAM, 85-2, Ankara, 1986. [27] Kaya, A. & Durukan, S., Utilization of Bentonite Embedded Zeolite as Clay Liner.

Applied Clay Science, 25, 83-91, 2004. [28] ASTM, Annual Book of ASTM Standards; Sect. 4, Vol. 04.08. American Society

for Testing and Materials, Philadelphia, Pa., 1999. [29] Daniel, D.E., State of the art: Laboratory hydraulic conductivity tests for saturated

soils. Hydraulic Conductivity and Waste Contaminant Transport in Soil, ASTM, STP, 1142, 30-78, 1994.

Determining the Engineering Properties of Bentonite – Zeolite Mixtures

1088

[30] Day, S.R. & Daniel, D.E., Hydraulic conductivity of two prototype clay liners. Journal of Geotechnical Engineering, 111, 957-970, 1985.

[31] King, K.S., Quigley, R.M., Fernandez, F., Reades, D.W. & Bacopoulos, A., Hydraulic conductivity and diffusion monitoring of the Keele Valley Landfill liner, Maple, Ontario. Canadian Geotechnical Journal, 30, 124-134, 1993.