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Variations in Heavy Metal Analytical Results and Leaching Characteristics of Coal Ash Recycled Concretes according to Sample Crushing Methods

분쇄방법에 따른 석탄재 재활용 콘크리트의 중금속 분석결과 및 용출특성 변화

  • Lee, Jin Won (Department of Environmental Engineering, Kunsan National University) ;
  • Choi, Seung-Hyun (Department of Environmental Engineering, Kunsan National University) ;
  • Kim, Kangjoo (Department of Environmental Engineering, Kunsan National University) ;
  • Moon, Bo-Kyung (Korea Western Power, Co., Ltd.)
  • Received : 2018.08.14
  • Accepted : 2018.10.18
  • Published : 2018.10.28

Abstract

Since concrete is a hardened aggregates of various materials, it needs to be crushed for chemical analyses. However, the effect of sample crushing on the analytical results has not been precisely assessed till today. In this study, we prepared concrete test pieces using Portand cements and fly ashes as binding materials, and ponded ashes and sands as aggregates and analyzed the heavy metals of the test pieces using Standards for Fair Testing of Soil Contamination (SFTSC) and Wastes (SFTW). For this, each test piece was partially crushed at first and sieved for separation of grains of <0.15 mm, 0.15-0.5 mm, and 0.5-5 mm from the same crushed samples (Crushing Method I). Results of those samples using SFTSC showed a clear trend that analyzed heavy metal concentrations are higher in the finer fractions. Particularly, fractions with <0.15 mm indicated much higher concentrations than the theoretical ones, which were calculated based on the concentrations of individual materials and their mixing fractions. In contrast, the analytical results were generally comparable with the theoretical ones when the test pieces were totally pulverized such that all the crushed grains were <0.15 mm in size (Crushing Method II). These results are associated with the fact that cement materials and fly ashes, which are high in heavy metals relative to other materials, are enriched in the fine fractions. The analytical results using the SFTW derived very low concentrations in most of parameters and did not indicate the dependence of concentrations on the crushing methods due to using distilled water as leaching agent.

콘크리트는 덩어리이기 때문에 분석을 위해서는 분쇄를 할 수밖에 없다. 그러나, 콘크리트와 같이 여러 재료의 혼합물을 파쇄, 특정 입도를 선별하는 것에 따른 효과는 아직까지 적절하게 평가된 바가 없다. 본 연구에서는 시멘트와 비산재를 고화제로 사용하고, 매립재와 모래는 골재로 사용하여 콘크리트 공시체를 제작한 다음, 토양오염공정시험기준과 폐기물공정시험기준에 따라 중금속분석을 수행하였다. 이를 위하여, 먼저, 공시체를 어느 정도 파쇄한 다음 채질하여 <0.15 mm, 0.15~0.5 mm, 0.5~5 mm를 선별(분쇄방법 1)하여 분석하였다. 토양오염공정시험기준 분석 결과, 작은 입도의 시료가 높은 중금속 농도를 보이는 경향이 뚜렷하였다. 특히, <0.15 mm는 각 개별재료의 농도와 배합비로 계산된 이론값보다도 몇 배 높은 값을 보이기도 하였다. 반면, 시료 전체가 <0.15 mm를 갖도록 완전히 분쇄(분쇄 방법 2)하여 분석한 결과는 이론값과 비슷한 농도를 보였다. 이 같은 결과는, 부분 분쇄 시에는 작은 입도에 중금속 농도가 높은 시멘트와 비산재가 농집되는 것과 관련이 있다. 반면, 폐기물공정시험기준 분석에서는 모든 항목에서 매우 낮은 용출 농도를 보였고, 토양오염공정시험기준에서와 같은 경향도 관찰되지 않았다.

Keywords

References

  1. Abouelnasr, D.M. (2010) The relationship between soil particle size and lead concentration. Proceedings of the annual international conference on soil, sediments, water and energy, v.14(8), p.1-86.
  2. Ahmaruzzaman, M. (2010) A review on the utilization of fly ash. Prog. Energy Combust. Sci., v.36, p.327-363. https://doi.org/10.1016/j.pecs.2009.11.003
  3. Ainsworth, C.C. and Rai, D. (1987) Chemical characterization of fossil fuel wastes. Rep. EA-5321 Electric Power Res. Inst., Palo Alto, CA.
  4. Akpomie, K.G., Dawodu, F.A. and Adebowale, K.O. (2015) Mechanism on the sorption of heavy metals from binary-solution by a low cost montmorillonite and its desorption potential. Alexandria Eng. J., v.54, p.757-767. https://doi.org/10.1016/j.aej.2015.03.025
  5. Chen, Q.Y., Tyrer, M., Hills, C.D., Yang, X.M. and Carey, P. (2009) Immobilisation of heavy metal in cement-based solidification/stabilisation: A review, Waste Manage., v.29, p.390-403. https://doi.org/10.1016/j.wasman.2008.01.019
  6. Cheriaf, M., Cavalcante, R.J. and Pera, J. (1999) Pozzolanic properties of pulverized coal combustion bottom ash. Cem. Concr. Res., v.34, p.957-693.
  7. Choi, W.H., Lee, S.R. and Park, J.Y. (2009) Cement based solidification/ stabilization of arsenic-contaminated mine tailings. Waste Manage., v.29, p.1766-1771. https://doi.org/10.1016/j.wasman.2008.11.008
  8. Eary, L.E., Rai, D., Mattigod, S.V. and Ainsworth, C.C. (1990) Geochemical factors controlling the mobilization of inorganic constituents from fossil fuel combustion residues: II. Review of the minor elements. J. Environ. Qual., v.19, p.202-214.
  9. Jaturapitakkul, C. and Cheerarot, R. (2003) Development of Bottom Ash as Pozzolanic Material. J. Mater. Civil Eng., v.15, p.45-53.
  10. Jung, B.K., Kim, K. and Kim, S.H. (2012) Environmental assessment for reclamation using coal ash. Academy-Industry Cooperation of Kunsan National University.
  11. Kim, K. (2013) A study on the possibility of economic metal extraction from coal ash. Academy-Industry Cooperation of Kunsan National University
  12. Kim, K., Kim, S.H., Park, S.M., Kim, J. and Choi, M. (2010) Processes controlling the variations of pH, alkalinity, and $CO_2$ partial pressure in the porewater of coal ash disposal site. J. Hazard. Mater., v.181, p.74-81. https://doi.org/10.1016/j.jhazmat.2010.04.089
  13. Kim, K., Park, S.M., Kim, J., Kim, S.H., Kim, Y., Moon, J.T., Hwang, G.S. and Cha, W.S. (2009) Arsenic concentration in porewater of an alkaline coal ash disposal site: Roles of siderite precipitation/dissolution and soil cover. Chemosphere, v.77, p.222-227. https://doi.org/10.1016/j.chemosphere.2009.07.029
  14. Kim, S.H., Choi, S.H., Jeong, G.Y., Lee, J.C. and Kim, K. (2014) A geochemical study on the enrichment of trace elements in the saline ash pond of a bituminousburning power plant in Korea. J. Miner. Soc. Korea, v.27(1), p.31-40. https://doi.org/10.9727/jmsk.2014.27.1.31
  15. Kim, S.H., Kim, K., Ko, K.S., Kim, Y. and Lee, K.S. (2012) Co-contamination of arsenic and fluoride in the groundwater of unconsolidated aquifers under reducing environments. Chemosphere, v.87(8), p.851-856. https://doi.org/10.1016/j.chemosphere.2012.01.025
  16. Kim, Y., Kim, K. and Jeong, G.Y. (2017) Study of detailed geochemistry of hazardous elements in weathered coal ashes. Fuel, v.193, p.343-350. https://doi.org/10.1016/j.fuel.2016.12.080
  17. Lee, J.W., Choi, S.H., Kim, K., Kim, S.H. and Moon, B.K. (2018) A study on changes in heavy metal contents in concrete prepared using coal ashes. Econ. Environ. Geol. (submitted)
  18. Park, S.G. and Kim, J.M. (2012) Present Status and Recycling Technology for Bottom Ash in Korea. J. Rec. Const. Resources, v.7 n.1
  19. Shi, H.S. and Kan, L.L. (2009) Leaching behavior of heavy metals from municipal solid wastes incineration (MSWI) fly ash used in concrete. J. Hazard. Mater., v.164, p.750-754. https://doi.org/10.1016/j.jhazmat.2008.08.077
  20. Smedley, P.L. and Kinniburgh, D.G. (2002) A review of the source, behaviour and distribution of arsenic in natural waters. Appl. Geochem., v. 17, P. 517-568. https://doi.org/10.1016/S0883-2927(02)00018-5
  21. Vysvaril, M. and Bayer, P. (2016) Immobilization of heavy metals in natural zeolite-blended cement pastes. Procedia Eng., v.151, p.162-169. https://doi.org/10.1016/j.proeng.2016.07.363