The Effect of Ulexite Additive on the Engineering Properties of Sand-Bentonite Mixtures

Abstract

Bentonites and sand-bentonite mixtures are usually used for impervious barriers at nuclear waste repositories, municipal solid waste landfill liners, etc. These mixtures should be able to perform for a long time without changing their strength and hydraulic conductivity properties. The literature studies have shown that high temperature and thermal cycles have negative effects on the hydraulic conductivity and strength of soils. For example, hydraulic conductivity increases in the presence of high temperature. For that reason, the resistivity of bentonites and sand-bentonite mixtures should be increased against high temperatures when they are used in liners. Boron minerals are used in order to increase the thermal resistivity of materials in industry. Hence the boron mineral namely; ulexite can be added to the sand-bentonite mixtures in order to improve strength and hydraulic conductivity properties of these mixtures against high temperature or thermal cycles. In this study, the compaction, consolidation, hydraulic conductivity and shear strength properties of ulexite added sand-bentonite mixtures were investigated at room temperature. Additionally, the shear strength behavior of ulexite added sand-bentonite mixtures was investigated under high temperature (80°C). The sand-bentonite mixtures were prepared which contains 10% bentonite by weight. The 10% and 20% ulexite were added to these mixtures. The mixtures were prepared according to the compaction test results (dry unit weight and optimum water content+2%). According to the test results, as the ulexite additive decreased the optimum water content value and increased the maximum dry unit weight. When the ulexite was added to the sand-bentonite mixtures, amount of the total vertical strain (compressibility) increased as the ulexite percentage increased. The maximum shear stress value of sand-bentonite mixtures in the presence of ulexite at 80°C was generally higher than those of at room temperature.

Keywords

• Boron,shear strength,consolidation,compaction,temperature

Üleksit Katkısının Kum-Bentonit Karışımlarının Mühendislik Özelliklerine Etkisi

Abstract

Bentonit ve kum-bentonit karışımları genellikle nükleer atık depolama sahaları, kentsel katı atık depolama alanlarında geçirimsiz bariyer uygulamalarında kullanılırlar. Bu zemin karışımlarının dayanım ve hidrolik iletkenlik gibi mühendislik özellikleri tasarım aşamasındaki değerlerde çok uzun süre değişmeden kalmalıdır. Literatür çalışmaları, yüksek sıcaklık ve termal döngülerin, zeminlerin hidrolik iletkenlik, hacimsel deformasyon ve dayanımı üzerinde olumsuz etkileri olduğunu göstermiştir. Endüstride, malzemelerin termal direncini arttırmak için bor mineralleri kullanılmaktadır. Bu nedenle bir bor minerali olan üleksit, zemin karışımlarının yüksek sıcaklık veya termal döngülere karşı dayanım ve hidrolik iletkenlik özelliklerini geliştirmek için bentonit veya kum-bentonit karışımlarına eklenebilir. Bu çalışmada, üleksit katkılı kum-bentonit karışımlarının kompaksiyon, konsolidasyon, hidrolik iletkenlik ve kayma dayanımı özellikleri oda sıcaklığında, ayrıca üleksit ilave edilmiş kum-bentonit karışımlarının kayma dayanımı davranışı yüksek sıcaklık varlığında (80°C) incelenmiştir. Deneylerde %10 bentonit içeren kum-bentonit karışımlarına %10 ve %20 oranlarında üleksit eklenmiştir. Elde edilen sonuçlara göre, üleksit katkısı kum-bentonit karışımlarının optimum su içeriği değerini düşürürken, maksimum kuru birim hacim ağırlık değerini arttırmıştır. Üleksit yüzdesi arttıkça toplam düşey deformasyon (sıkışabilirlik) miktarı artmıştır. Üleksit varlığında kum-bentonit karışımlarının 80°C'de maksimum kayma gerilmesi değeri, genellikle oda sıcaklığındaki değerlerden daha yüksek elde edilmiştir.

Keywords

• Bor,kayma dayanımı,konsolidasyon,kompaksiyon,sıcaklık

References

1. [1] Abuel-Naga H.M., “Experimental evaluation of engineering behavior of soft Bangkok clay under elevated temperature”, Journal of Geotechnical and Geoenvironmental Engineering, 132(7): 902- 910, (2006).
2. [2] Pusch R., “General microstructural model for qualitative and quantitative studies of smectite clays”, SKB Technical Report, 90-43, Stockholm, Sweden (1990).
3. [3] Cho W.J., Lee J.O., and Chun K.S., “The temperature effects on hydraulic conductivity on compacted bentonite”, Applied Clay Science, 14: 47-58, (1999).
4. [4] Wang M.C., “The effect of heating on engineering properties of clays”, Physico-Chemical Aspects of Soil and Related Materials, ASTM STP 1095, Philadelphia, 139-158, (1990).
5. [5] Mitchell J. K., “Temperature effects on the engineering properties and behavior of soils”, Proceeding of International Conference on the Effects of Temperature and Heat on Engineering Behaviour of Soils, 9(6): 9–28, (1969).
6. [6] Hong Z. S., Bian X., Cui Y. J., Gao Y. F., and Zeng L. L., “Effect of initial water content on undrained shear behaviour of reconstituted clays”, Géotechnique, 63(6): 442–450 (2013).
7. [7] Abuel-Naga H.M.,” Effect of temperature on shear strength and yielding behavior of soft Bangkok clay”, Soils and Foundations, 47(3): 423–436, (2007).
8. [8] Alther G.R., “The role of bentonite in soil sealing applications”, Bulletin of the Association of Engineering Geologists, 19(4): 401-409, (1982).

9. [9] Alther G.R., “The qualifications of bentonite as a soil sealant”, Engineering Geology, 23(3-4): 177-191, (1987).
10. [10] Reschke A.E,. and Haug M.D., “The physico-chemical properties of bentonites and the performance of sand-bentonite mixtures”, in Proc. 44th Canadian Geotechnical Conf., Calgary, Alberta, Sept. 29 - Oct 2, 62-1 to 62-10, (1991).
11. [11] Kleppe J. H., and Olson R.E., “Desiccation cracking of soil barriers”, ASTM, Special Technical Publication, 874: 263-275, (1985).
12. [12] Özkan Ş. G., Çebi H., and Delice M. D., “Bor minerallerinin özellikleri ve madenciliği", 2 Endüstriyel Hammaddeler Sempozyumu, İzmir, Türkiye, 224-228, (1997).
13. [13] Sugozu I., Mutlu I., and Sugozu K. B., “The effect of ulexite to the tribological properties of brake lining materials”, Polymer Composites, 39(1), (2018).
14. [14] Alpaydın Ş.G., and Yukselen-Aksoy Y., “The effects of colemanite and ulexite additives on the geotechnical index properties of bentonite and sand-bentonite mixtures” In: Wu W., Yu HS. (eds) Proceedings of China-Europe Conference on Geotechnical Engineering, Springer Series in Geomechanics and Geoengineering. Springer, Cham, (2018a).
15. [15] Alpaydın Ş.G., and Yukselen-Aksoy Y., “The effect of colemanite and ulexite additives on the shear strength behavior of sand-bentonite mixtures under high temperature” International Symposium on Energy Geotechnics (SEG-2018). Laussanne- Switzerland (2018b).
16. [16] ASTM D4318-98, “Standard test methods for laboratory compaction characteristics of soil using standard effort”, ASTM International, West Conshohocken, PA, USA (1999).
17. [17] ASTM D2435/D2435M–11, “Standard test methods for one-dimensional consolidation properties of soils using incremental loading”, ASTM International, West Conshohocken, PA, USA (2011).
18. [18] ASTM D3080/D3080M–11, “Standard Test Method for Direct Shear Test of Soils Under Consolidated Drained Conditions”, ASTM International, West Conshohocken, PA, USA (2012).
19. [19] ASTM D5084 - 16a, “Standard test methods for measurement of hydraulic conductivity of saturated porous materials using a flexible wall permeameter”, ASTM International, West Conshohocken, PA, USA, 1–24 (2016).
20. [20] Keren R., and Mezuman U., “Boron adsorption by clay minerals using a phenomenological equation”, Clay and Clays Minerals, 29: 198-204, (1981).
21. [21] Wang S., Zhu W., Qian X., Xu H., and Fan X., “Applied clay science temperature effects on non-darcy flow of compacted clay”, Applied Clay Science, 135: 521–525 (2017).