CONCLUSIONS The load deflection curves indicated the advantage of fibrous concrete versus control concrete in obtaining higher toughness. Also, the development of crack width of specimen without fibers was quite different than those with steel fibers or polypropylene fibers. By comparison between steel fibers and polypropylene fibers in performance of flexural toughness and crack propagation, it was found that, steel fibers have good performance in flexural toughness than that of polypropylene fibers, on the other hand, steel fibers and polypropylene fibers have the same performance in crack propagation. In spite of the Young’s modulus of polypropylene fibers is about one tenth of steel fibers, it was noticed that the number of cracks and crack width was not increased so much when even polypropylene fibers is used. In spite of the flexural toughness can describe the toughness of concrete structural members with fibers at failure, it is not easy to use it in order to explain the propagation of cracking under service load. It is necessary to express the sustaining ability of load after cracking by an adequate estimating method. In addition, the reliable and easy method to judge the performance of concrete with fibers is necessary that everybody can choose the adequate fibers in order to improve the serviceability of concrete structures. REFERENCES 1. Sun, W., Gao, J. and Yan, Y. (1996) Study of the Fatigue Performance and Damage Mechanism of Steel Fiber Reinforced Concrete, ACI Materials Journal, Vol. 93, No.3, May-June, pp. 206-212. 2. S. P. Singh and S. K. Kaushik (2000) Flexural Fatigue Life Distributions and Failure Probability of Steel Fibrous Concrete, ACI Materials Journal, Vol. 97, No.6, November-December, pp. 658-667 3. Ayano, T., Abo El-Wafa, M., Yabuki, M., and Sakata, K., (2001), Resistance to Cracking due to Drying Shrinkage by Polypropylene Fiber, Proceedings of the Japan Concrete Institute, vol.22, No.2, pp.325~330 4. Hamada, T., Hikasa, J., Suemori, T. and Hirai T. (1999) Study on Concrete Reinforced by Vinylon Fiber, Proceedings of the Japan Concrete Institute, vol.21, No.2, pp.271~276 5. Kanemami A., Saeki N. and Horiguchi T. (1999) Cracking and Strength at Young age of Reinforced Concrete by Hybrid Fiber, Proceedings of the Japan Concrete Institute, vol.21, No.2, pp.259~264 6. Zhang, J. and Henrik, S. (1998) Fatigue Performance in Flexure of Fiber Reinforced Concrete, ACI Materials Journal, Vol. 95, No.1, Jan.-Feb., pp. 58-67. 7. Sun, W., Gao, J. and Yan, Y. (1996) Study of the Fatigue Performance and Damage Mechanism of Steel Fiber Reinforced Concrete, ACI Materials Journal, Vol. 93, No.3, May-June, pp. 206-212
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