International Journal of Highway Engineering (한국도로학회논문집)

Korean Society of Road Engineers (한국도로학회)
권호 표지

A Preliminary Study on Reduction of Shrinkage Stress in Concrete Slabs

콘크리트 슬래브 건조수축 응력 감소에 관한 초기연구

  • Published : 2009.12.15
Download PDF
⟨ Previous Next ⟩

Abstract

Volume of concrete slab changes by variations of temperature and moisture after its placement. Shrinkage due to evaporation causes tensile stress in the slab when contraction of the slab is restrained by its self weight, friction with subbase, and etc. Actual tensile stress caused by the shrinkage was less than theoretically predicted stress according to previous studies. It was the stress reduction due to visco-elastic property of the early-age concrete slab partially restrained. In this study, strains of restrained circumferential, unrestrained circumferential, and unrestrained square pillar concrete specimens were measured to investigate stress reduction of the specimens with age of concrete. Elastic modulus of the concrete was measured at the age of 1, 3, 7, 14, 28 days and penetration test was performed. The stress reduction was calculated by input the test results into theoretical equations suggested by previous researchers. The stress reduction of the restrained concrete specimens will be applied to design of concrete pavements based on results of the study.

콘크리트 슬래브는 타설 후 온도와 수분 변화를 통해 체적이 변화한다. 수분증발에 의하여 발생한 건조수축은 슬래브의 자중이나 하부층과의 마찰 등에 의하여 구속되어 슬래브 내부에 응력이 유발된다. 선행 연구에 의하면 건조수축에 의하여 발생된 실제 인장응력은 이론적으로 예측된 값보다 작은 것으로 보고되었다. 이는 부분적으로 구속된 슬래브에서 발생하는 초기 재령 콘크리트의 점탄성에 기인한 응력감소 현상이다. 본 연구에서는 재령에 따른 콘크리트의 응력감소 현상을 조사하기 위하여 구속된 원주형, 구속되지 않은 자유건조 원주형, 그리고 자유건조 각주형 콘크리트 시편의 변형률을 측정하였다. 재령 1, 3, 7, 14, 28일에 콘크리트의 탄성계수를 측정하였으며 관입저항 실험을 실시하였다. 실험결과를 기존 연구자들이 제안한 이론식에 대입하여 구속된 원주형 콘크리트 시편의 응력감소를 계산할 수 있었다. 향후 본 연구의 결과를 바탕으로 구속된 콘크리트 시편의 응력감소 현상을 콘크리트 포장의 설계에 적용할 예정이다.

Keywords

References

  1. 김진철 (2003).' 콘크리트의 건조수축 매커니즘과 예측모형', 도로포장공학 회지, 제5권, 제3호, pp. 32-41
  2. 조호진 (2003).' 초기재령 콘크리트의 거동 해석 기법.' 박사학위논문. 연세 대학교
  3. AASHTO (2002). 'Guide for Design of Pavement and Structures', American Association of State Highway and Transportation Officials.
  4. ACI Committee 209. (1997). 'Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures', ACI 209R-92, ACI Manual of Concrete Practice, American Concrete Institute, Farmington Hills, MI.
  5. Altoubat, S. A. and Lange, D. A. (2001). 'Creep, Shrinkage and Cracking of Restrained Concrete at Early-age,' ACI Material Journal, Vol. 98, No. 4, July- Aug, pp.323-331.
  6. Bazant, Z. P. and Panula, L. P. (1978)'. Simplified Prediction of Concrete Creep and Shrinkage from Strength and Mix', Structural Engineering Report No. 78- 10/640, Northwestern University, Evanston, IL.
  7. Bazant, Z. P. (2001). 'Prediction of Concrete Creep and Shrinkage: Past, Present and Future', Nuclear Engineering and Design, Vol. 203, No. 1, January, pp.27- 38. https://doi.org/10.1016/S0029-5493(00)00299-5
  8. Bendana. L. J., Sargan. S. H., Khoury. I., and Selle. R. (2003). 'Environmental Influence of Early Age Response of PCC Pavement', 82nd Transportation Record Board Annual Meeting.
  9. CEB-FIP. (1990). 'CEB-FIP Model Code 1990: Design Code',. Thomas Telford Ltd., London, UK.
  10. Hossain A. B. and Weiss J. (2004). 'Assessing Residual Stress Development and Stress Relaxation in Restrained Concrete Ring Specimens.'Cement and Concrete Composites, Vol. 26, No. 5, pp.531-540. https://doi.org/10.1016/S0958-9465(03)00069-6
  11. Hossain. A. B, Fonseka. A. and Bullock. H. (2008)'. Early Age Stress Development, Relaxation, and Cracking in Restrained Low W/C Ultrafine Fly Ash Mortars'Journal of Advanced Concrete Technology, Vol. 6, No. 2, April, pp.261-271. https://doi.org/10.3151/jact.6.261
  12. Jeong, J. H. and Zollinger, D. G. (2005)'. Environmental Effects on the Behavior of Jointed Plain Concrete Pavements.' Journal of Transportation Engineering, ASCE, Vol. 131, No. 2, February, pp. 140-148. https://doi.org/10.1061/(ASCE)0733-947X(2005)131:2(140)
  13. Kovler, K., Sikuler, J., and Bentur, A. (1993).“ Restrained Shrinkage Tests of Fiber Reinforced Concrete Ring Specimens : Effect of Core Thermal Expansion”, Materials and Structures, Vol. 26, No. 4, pp.231-237. https://doi.org/10.1007/BF02472616
  14. Schooppel. K., Plannerer. M. and Springenschmid. R. (1995). 'Determination of Restraint Stresses and of Material Properties During Hydration of Concrete with the Temperature-Stress Test Machine', Proceedings of the International RILEM Symposium, Thermal Cracking in Concrete at Early Ages, Springenschmid, R., ed, E&FN Spon, Germany, pp.153-160.
  15. Sun Renjuan (2009). 'Development of shrinkage-Equivalent Temperature Difference Model for Concret Pavement Slabs', Ph.D. Thesis, Inha University
  16. Suprenant, B. A. (2002).' Why Slabs Curl.', Concrete International, Part1, March, pp. 56-61
  17. Suprenant, B. A. (2002).“ Why Slabs Curl.”, Concrete International, Part 2, April, pp. 59-64
  18. Yang. W., Jason. W., and Surendra. P. S. (2000)'. Predicting Shrinkage Stress Field in Concrete Slabs on Elastic Subgrade', Journal of Engineering Mechanics, Vol. 126, No. 1, January, pp.35-42. https://doi.org/10.1061/(ASCE)0733-9399(2000)126:1(35)