13th International Conference on Fracture June16–21, 2013, Beijing, China -8Table 7. Ultimate loading strength of UHPC2.5 precast specimens after freeze-thaw cycling test Freeze-thaw cycling 0 cycle 200 cycles 400 cycles 600 cycles Ultimate loading strength 12293 kg 12864 kg 13349 kg 14344 kg Ratio of loading strength 0.0 % 4.4 % 8.1 % 15.8 % 4. Summary 1) For the ranges of steel fiber contents investigated in the study, both flexural strength and ultimate loading strength of the UHPC specimens increase as the percent steel fiber increase. 2) The application of the heat water curing or steam treatment is clearly beneficial to UHPC precast specimens. 3) The 2.5, 3.0 and 3.5% steel fibres by volume were chosen and used in UHPC precast products, after UHPC specimens were tested and finished on their performance evaluations. 4) Two diameters of steel fiber used in UHPC precast specimens exhibit non-significantly enhanced ultimate loading strength at 90 °C water curing. 5) UHPC precast specimens containing up to 2.5% steel fiber content reached the predetermined effect at particular load level of 12-ton ultimate loading strength. 6) The UHPC2.5 precast specimens displayed a continuous increase in ultimate loading capacity after 600 free-thaw cycles. References [1] A. M. Neville, Properties of Concrete, John Wiley &Sons, Inc., New York, 1995. [2] J. Hartmann, and B. Graybeal, Testing of ultra-high-performance concrete girders. PCI Journal, 47-1 (2002) 148-149. [3] B. Graybeal, and J. Hartmann, Ultra-high performance concrete material properties. Proceedings, Transportation Research Board Conference, January 2003. [4] Yung-Chih Wang, and Ming-Gin Lee, Ultra-high strength steel fiber reinforced concrete for strengthening or new construction material of RC frames. Journal of Marine Science and Technology, 15-3 (2007) 972-976. [5] Ming-Gin Lee, Yu-Cheng Kan, and Kuei-Ching Chen, A preliminary study of rpc for repair and retrofitting material. Journal of the Chinese Institute of Engineers, 29-6 (2006) 1099-1103. [6] O. Bonneau, M. Lachemi, E. Dallaire, J. Dugat, and P. C. Aitcin, Mechanical properties and durability of two industrial reactive powder concretes. ACI Materials Journal, 94-4 (1997) 286-290. [7] N. Roux, C. Andrade, and M. Sanjuan, Experimental study of durability of reactive powder concrete. Journal of Materials in Civil Engineering, 8-1 (1996) 12-20. [8] F. J. Alaee, Retrofitting of concrete structures using high performance fiber reinforced cementitious composite (HPFRCC), Ph.D. Thesis, University of Wales, Cardiff , 2001. [9] A. H. Kelly, M. Arch., and P. J. Seibert, Thin UHPC cladding exhibits green curves. Precast Magazines, 167 (2011). http://precast.org/precast-magazines/precast-solutions./2011-fall. [10] TechBrief, Simultaneous structural and environmental loading of a UHPC component. FHWA Publication No: FHWA-HRT-10-055, 2010. [11] Ming-Gin Lee, Chui-Te Chiu, and Yung-Chih Wang, The study for bond strength and bond durability of reactive powder concrete. ASTM STP 1463, Editor: Dennis Damico, West Conshohocken, PA, 2005, pp. 104-113. [12] Ming-Gin Lee, Yi-Shuo Huang, Fire-damage or freeze-thaw of strengthening concrete using ultra high performance concrete. Advanced Materials Research, 79-82 (2009) 2047-2050.
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