DOI QR코드

DOI QR Code

경량골재 콘크리트의 압축강도에 대한 시험체 기하학적 특성의 영향

Influence of Specimen Geometries on the Compressive Strength of Lightweight Aggregate Concrete

  • Sim, Jae-Il (Dept. of Architectural Engineering, Kyonggi University) ;
  • Yang, Keun-Hyeok (Dept. of Architectural Engineering, Kyonggi University)
  • 투고 : 2012.02.28
  • 심사 : 2012.04.10
  • 발행 : 2012.06.30

초록

경량골재 콘크리트의 압축강도에 대한 크기 및 형상효과를 평가하기 위하여 9 배합의 실내 실험과 3 배합의 레미콘 배합을 수행하였다. 콘크리트 배합은 보통중량, 전경량 및 모래경량의 3그룹으로 분류되었다. 각 콘크리트 배합에서 원형 또는 사각형 단면을 갖는 시험체의 형상비는 1.0과 2.0이었다. 시험체의 단면 크기는 각 실내배합에서는 50~150mm, 각 레미콘 배합에서는 50~400mm 범위에 있었다. 실험 결과 경량골재 콘크리트의 균열진전과 국부 파괴영역은 보통중량 콘크리트와 상당히 달랐다. 경량골재 콘크리트에서 균열은 골재를 관통하였으며, 균열의 분포영역은 매우 국부적이었다. 이로 인해, 경량골재 콘크리트의 크기효과는 보통중량 콘크리트에 비해 더 크게 나타났으며, 이 현상은 형상비 1.0보다는 2.0인 시험체에서 더 뚜렷하게 나타났다. 김진근 등의 크기효과 예측모델은 경량골재 콘크리트에서 시험체 단면크기가 150mm 이상일 때 과대 평가하였다. 반면, 압축강도에 대한 시험체 형상의 영향을 보정하기 위해 ASTM 및 CEB-FIP에서 제시한 수정계수는 경량골재 콘크리트에서도 안전측에 있었다.

The current study prepared 9 laboratorial concrete mixes and 3 ready-mixed concrete batches to examine the size and shape effects in compression failure of lightweight aggregate concrete (LWC). The concrete mixes were classified into three groups: normal-weight, all-lightweight and sand-lightweight concrete groups. For each concrete mix, the aspect ratio of circular or square specimens was 1.0 and 2.0. The lateral dimension of specimens varied between 50 and 150 mm for each laboratorial concrete mix, whereas it ranged from 50 to 400 mm with an incremental variation of 50 mm for each ready-mixed concrete batch. Test observations revealed that the crack propagation and width of the localized failure zone developed in lightweight concrete specimens were considerably different than those of normal-weight concrete (NWC). In LWC specimens, the cracks mainly passed through the coarse aggregate particles and the crack distribution performance was very poor. As a result, a stronger size effect was developed in LWC than in NWC. Especially, this trend was more notable in specimens with aspect ratio of 2.0 than in specimens with that of 1.0. The prediction model derived by Kim et al. overestimated the size effect of LWC when lateral dimension of specimen is above 150 mm. On the other hand, the modification factors specified in ASTM and CEB-FIP provisions, which are used to compensate for the shape effect of specimen on compressive strength, were still conservative in LWC.

키워드

참고문헌

  1. Bazant, Z. P. and Planas, J., Fracture and Size Effect in Concrete and Other Quasibrittle Materials, CRC Press, 1998, 616 pp.
  2. ASTM Standards, "Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens," Annual Book of ASTM Standards (ASTM C 39-01), American Society for Testing and Materials, Philadelphia, 2001, 5 pp.
  3. Comit Euro-International du Beton (CEB-FIP), Structural Concrete: Textbook on Behaviour, Design and Performance, International Federation for Structural Concrete (Fib), 1999, 224 pp.
  4. 국토해양부, 콘크리트 구조설계기준, 한국콘크리트학회, 2003, 328 pp.
  5. ACI Committee 318, Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary (ACI 318R-08), American Concrete Institute, 2008, 473 pp.
  6. Gonnerman, H. F., "Effect of Size and Shape of Test Specimen on Compressive Strength of Concrete," ASTM Proceedings, Vol. 25, No. 2, 1925, pp. 237-255.
  7. Blanks, R. F. and McNamara, C. C., "Mass Concrete Tests in Large Cylinder," ACI Journal, Proceedings, Vol. 31, No. 1, 1935, pp. 280-303.
  8. Neville, A. M., "A General Relation for Strength of Concrete Specimens of Different Shape and Size," ACI Journal, Proceedings, Vol. 63, No. 10, 1966, pp. 1095-1110.
  9. Bazant, Z. P., "Size Effect in Blunt Fracture: Concrete, Rock, Metal," Journal of Engineering Mechanics, ASCE, Vol. 110, No. 4, 1984, pp. 518-535. https://doi.org/10.1061/(ASCE)0733-9399(1984)110:4(518)
  10. Kim, J. K., Yi, S. T., Park, C. K., and Eo, S. H., "Size Effect on Compressive Strength of Plain and Spirally Reinforced Concrete Cylinders," ACI Structural Journal, Vol. 96, No. 1, 1999, pp. 88-94.
  11. 김진근, 어석홍, 이성태, "비표준형 실린더 공시체에 대한 콘크리트 압축강도의 크기효과," 콘크리트학회지, 9 권, 1호, 1997, pp. 105-113.
  12. 양근혁, 오승진, 송진규, "경량골재를 사용한 알칼리활성 슬래그 콘크리트의 역학적 특성," 콘크리트학회 논문집, 20권, 3호, 2008, pp. 405-412. https://doi.org/10.4334/JKCI.2008.20.3.405
  13. Neville, A. M., Properties of Concrete, Longman, UK, 1995.
  14. 심재일, 양근혁, "천연모래 치환율과 경량 굵은 골재 최대 크기에 따른 경량골재 콘크리트의 역학적 특성," 콘크리트학회 논문집, 23권, 5호, 2011, pp. 551-558. https://doi.org/10.4334/JKCI.2011.23.5.551
  15. Kesler, C. E., "Effect of Length to Diameter Ratio on Compressive Strength-An ASTM Cooperative Investigation," Proceeding, ASTM, Vol. 59, 1959, pp. 1216-1229.
  16. Kang, S. C. and Eun, H. C., "A Study on Size Effects of Square Cross-Section Specimens on Compressive Strength of Concrete," Journal of Research Institute of Advanced Technology, Vol. 11, No. 1, 2000, pp. 177-182.
  17. Yi, S. T., Yang, E. I., and Choi, J. C., "Effect of Specimen Sizes, Specimen Shapes, and Placement Directions on Compressive Strength of Concrete," Nuclear Engineering and Design, Vol. 236, No. 2, 2006, pp. 115-127. https://doi.org/10.1016/j.nucengdes.2005.08.004
  18. Chung, H. W., "On Testing of Very Short Concrete Specimens," Cement, Concrete, and Aggregate, ASTM, Vol. 11, No. 1, 1989, pp. 40-44. https://doi.org/10.1520/CCA10100J
  19. Aitcin, P. C., Miao, B., Cook, W. D., and Mitchell, D., "Effect of Size and Curing on Cylinder Compressive Strength of Normal and High-Strength Concretes," ACI Materials Journal, Vol. 91, No. 4, 1994, pp. 349-354.
  20. Sener, S., "Size Effect Tests of High Strength Concrete," Journal of Materials in Civil Engineering, ASCE, Vol. 9, No. 1, 1997, pp. 46-48. https://doi.org/10.1061/(ASCE)0899-1561(1997)9:1(46)
  21. Yang, K. H., "Modelling of the Mechanical Properties of Structural Lightweight Concrete Based on Size Effects," Technical Report, Department of Architectural Engineering, Kyonggi University, 2011, 89 pp.
  22. ACI Committee 211, "Standard Practice for Selection Proportion for Structural Lightweight Concrete (ACI 211.2- 98)," ACI Manual of Concrete Practice, Part 1, American Concrete Institute, Detroit, Michigan, 1983, 20 pp.
  23. ACI 213R-03, Guide for Structural Lightweight Aggregate Concrete, ACI Committee 213, American Concrete Institute, 2003, 38 pp.
  24. 한국공업표준협회, KS 기준안, 한국공업표준협회, 2006.
  25. 길본창, 강창구, 콘크리트 변형과 파괴, 원기술, 2004, 295 pp.