Issue 43

S. Jing et alii, Frattura ed Integrità Strutturale, 43 (2018) 33-42; DOI: 10.3221/IGF-ESIS.43.02 39 Test Group A Fly Ash Content B Sand-binder Ratio C Water-binder Ratio D Plasticizer Content Ultimate Tensile Strain （ % ） Z1 1(0.9) 1(0.30) 1(0.20) 1(0.40%) 0.458 Z2 1(0.9) 2(0.33) 2(0.23) 2(0.70%) 0.825 Z3 1(0.9) 3(0.36) 3(0.26) 3(1.00%) 1.482 Z4 2(1.2) 1(0.30) 2(0.23) 3(1.00%) 0.96 Z5 2(1.2) 2(0.33) 3(0.26) 1(0.40%) 1.51 Z6 2(1.2) 3(0.36) 1(0.20) 2(0.70%) 0.424 Z7 3(1.5) 1(0.30) 3(0.26) 2(0.70%) 1.575 Z8 3(1.5) 2(0.33) 1(0.20) 3(1.00%) 0.532 Z9 3(1.5) 3(0.36) 2(0.23) 1(0.40%) 1.045 K 1 2.765 2.993 1.414 3.013 K 2 2.894 2.867 2.830 2.824 K 3 3.152 2.951 4.567 2.974 K — 1 0.922 0.998 0.471 1.004 K — 2 0.965 0.956 0.943 0.941 K — 3 1.051 0.984 1.522 0.991 R 0.129 0.042 1.051 0.063 Table 3 : Orthogonal Experiment Result of Tensile Property. Figure 6 : Influence of Changes in Factors on ultimate tensile strain. D ISCUSSION ABOUT THE TOUGHENING MECHANISM OF PVA FIBERS n general, the numerous initial microdefects in the concrete matrix were demonstrated as tiny cracks in the loading process. According to the test, it is concluded that fibers should take up 2% of the volume of the specimen and should be randomly distributed throughout the specimen. Capable of bridging the initial microdefects, plenty of fibers can obviously reduce the occurrence and expansion of tiny cracks. As much of the matrix is held together by fibers, it is less likely for microdefects to develop in the initial phase. Thanks to the fibers, the specimen is fortified on the inside, making the matrix more resistant to deformation [17]. I