Journal of the Korea institute for structural maintenance and inspection (한국구조물진단유지관리공학회 논문집)

Korea Institute for Structural Maintenance Inspection (한국구조물진단유지관리공학회)
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Experimental Study for Evaluating Early Age Shrinkage of Mortar for 3D Printing

3D 프린팅용 모르타르의 초기재령 수축거동 평가를 위한 실험적 연구

  • 서은아 (한국건설기술연구원 구조연구본부) ;
  • 양근혁 (경기대학교 스마트시티공학부 건축공학전공) ;
  • 이호재 (한국건설기술연구원 구조연구본부)
  • Received : 2022.03.17
  • Accepted : 2022.04.25
  • Published : 2022.04.30
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Abstract

Since the 3D printing mortar is exposed to the atmosphere immediately after printing, moisture is largely evaporated from the surface of the layer. The evaporation of moisture on the surface of the layer greatly causes drying shrinkage and increases the risk of cracking and damage to the structure due to drying shrinkage. This study experimentally evaluated the shrinkage behavior of the initial age using the mortar used for 3D printing. The change in shrinkage was evaluated by comparing the shrinkage of the specimen cured by the sealing method and the atmospheric exposure method. In addition, compared with the case where type 1 cement was used 100%, the shrinkage amount was evaluated when 20% of fly ash was replaced and 10% of silica fume was used. In particular, the effect of three chemical admixtures applied using 3D printing on shrinkage was evaluated experimentally. When fly ash and silica fume were used, the shrinkage amount increased by 60 - 110% compared to the case when type 1 cement was used. The application of viscosity modifiers and shrinkage reducers reduced the shrinkage by at least 18% and at most 70% depending on the curing conditions. The temperature of the specimen temporarily decreased to 15 ℃ at the beginning of curing, and the correlation between the internal temperature of the specimen and the shrinkage behavior was observed.

이 연구는 적층 시공 시 타설 초기부터 외기에 직접 노출되는 조건을 모사하여 밀봉조건과 노출조건에 따른 수축거동을 100일 이상 실험적으로 분석하였다. 결합재 치환에 따른 수축거동 분석을 위해 1종 시멘트, 플라이애시, 실리카흄을 사용하여 동일한 조건에서 길이변화율을 측정하였다. 혼화제 사용이 수축거동에 미치는 영향을 분석하기 위해 적층 시공 시 사용되는 셀룰로오스계 점도조절제와 유지계 수축저감제를 사용하였다. 표면노출양생 시 초기 수축 발생시점이 단축됐으며, 플라이애시와 실리카흄을 사용 시 수축량은 양생조건에 따라 OPC100 배합 대비 60 - 110% 증가했다. 점도조절제와 수축저감제 적용은 양생조건에 따라 최소 18%에서 최대 70% 수축량을 저감시켰다. 시험체의 온도는 양생초기 15 ℃까지 일시적으로 저하됐으며, 수축거동과 상관성을 이 연구를 통해 확인했다.

Keywords

Acknowledgement

이 논문은 2022년 해양수산부 재원으로 해양수산과학기술진흥원의 지원을 받아수행된 연구임(과제명: 수중 적층 타설용 콘크리트 복합재료 개발, 과제번호: 20200555).

References

  1. ASTM C39. (2020). Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens.
  2. ASTM C490/C490M-21. (2021). Standard Practice for Use of Apparatus for the Determination of Length Change of Hardened Cement Paste, Mortar, and Concrete.
  3. ASTM C596-18. (2018). Standard Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement.
  4. Buswell, R. A., Kinnell, P., Wu, j., Hack, N. (2020). Inspection Methods for 3D Concrete Printing, RILEM Bookseries, 790-803.
  5. Chen, H., Chen, Q., Xu, Y., Lawi, A. S. (2022), Effects of silica fume and Fly ash on properties of mortar reinforced with recycled-polypropylene, Construction and Building Materials, 316 125887. https://doi.org/10.1016/j.conbuildmat.2021.125887
  6. Federowicz, K., Kaszynska, M., Zielinski, A., & Hoffmann, M. (2020). Effect of Curing Methods on Shrinkage Development in 3D-Printed Concrete. Materials, 13(11), 2590. https://doi.org/10.3390/ma13112590
  7. Jo, J. H., Jo, B. W., Cho, W., Kim, J. H. (2020). Development of a 3D Printer for Concrete Structures: Laboratory Testing of Cementitious Materials. International Journal of Concrete Structures and Materials. 14, 13. https://doi.org/10.1186/s40069-019-0388-2
  8. Kim, J. H., Park, B. S., Jung, S. H., Choi, Y. C. (2016), Effect of Properties of Fly-ashes on the Characteristics of Fly-ash Mortars, Journal of the Korean Recycled Construction Resources Institute, 4(4), 439-445. https://doi.org/10.14190/JRCR.2016.4.4.439
  9. Kwon, S. H., & Kim, J. K. (2016). Understanding of Drying Shrinkage and Autogeneous Shrinkage in Concrete. Magazine of the Korea Concrete Institute, 28(6), 22-26.
  10. Langan, B.W., Weng, K., Ward, M.A. (2002). Effect of silica fume and flyahs on heat of hydration of Portland cement, Cement and Concrete Research, 32(7), 1045-1051. https://doi.org/10.1016/S0008-8846(02)00742-1
  11. Lee, D. G., Yoo, B. H., Son, H. J. (2019a). Development of Shrinkage Reducing Agent for 3D Printing Concrete. Journal of the Korea Academia-Industrial cooperation Society, 20(12), 37-43. https://doi.org/10.5762/KAIS.2019.20.12.37
  12. Lee, H. J., Kim, K. H., Yoo, B. H., Kim, W. W. Moon, J. H. (2019b). Shrinkage Characteristic of Cementitious Composite Materials for Additive Manufacturing, Journal of the Korea institute for structural maintenance and inspection, 23(6), 99-104. https://doi.org/10.11112/JKSMI.2019.23.6.99
  13. Lee, H. J., Kim, J. H., Moon, J. H., Kim, W. W., and Seo, E. A. (2020), Effect of Shrinkage Characteristics of Cement-Based Composites by Extrusion and Lamination Process of Construction 3D Printing, Journal of the Korea Institute for Structural Maintenance and Inspection, 24(6), 113-118. https://doi.org/10.11112/JKSMI.2020.24.6.113
  14. Lee, H., Seo, E. A., Kim, W. W. Moon, J. H. (2021). Experimental Study on Time-Depend_ent Changes in Rheological Properties and Flow Rate of 3D Concrete Printing Materials, Materials, 14(21) 6278. https://doi.org/10.3390/ma14216278
  15. Park, J. P., Jung, Y. W. (2015) Fundamental Properties on the Development of High Performance Shrinkage Reducing Agent for Concrete, Journal of the Korea Academia-Industrial cooperation Society, 16 (6), 4298-4307. https://doi.org/10.5762/KAIS.2015.16.6.4298
  16. Shi, C., Day, R.L., (1995) A calorimetric study of early hydration of alkali-slag cements, Cement and Concrete Research, 25(6), 1333-1346. https://doi.org/10.1016/0008-8846(95)00126-W