Issue 41

S. Zhao et alii, Frattura ed Integrità Strutturale, 41 (2017) 412-423; DOI: 10.3221/IGF-ESIS.41.53 417 Fig. 7 and Fig. 8 show the relationship between the factors, the levels, and the K values of the anti-splitting test when the ordinary Portland cement is selected as the cementitious material and the carbon fiber and the steel fiber are selected as the fiber materials. It can be seen from Fig. 7 that the splitting strength clearly increases obviously when the content of the carbon fiber increases, and it declines when the content of the carbon exceeds a certain amount. Meanwhile, the content of the carbon fiber greatly affects the splitting strength of the concrete largely, followed by the graphite, and the scrap copper slag has the smallest impact. As can be analyzed concluded from Fig. 8, when the ordinary Portland cement is selected as the cementitious material, mixed with steel fiber in the splitting test group, with the amount of steel fiber increasing, the anti-splitting strength of the test block is basically even. According to the data in the figures, the content of graphite in this experiment is the biggest factor affecting the strength, followed by scrap copper slag. Fig. 9 and Fig. 10 show the relationship between the factors, levels, and K values in the anti-splitting test when the composite Portland cement is selected as the cementitious material, and the carbon fiber and the steel fiber are selected as the fiber materials. It can be seen from Fig. 9 that the strength of the test block decreases slightly when the content of the carbon fiber increases, but it increases when the content of carbon exceeds a certain amount. It can be seen from Fig. 10 that the strength of the anti-splitting increases significantly when the content of the steel fiber increases, and the amount of the steel fiber greatly affects the concrete's strength largely. Figure 9: Relationship between factors, levels, and K values (carbon fiber). Figure 10: Relationship between factors, levels, and K values (steel fiber). When comparing the compression process of the test blocks, it can be found that the pressure value of the concrete piece with carbon fiber under the pressure of the pressure testing machine of the concrete suddenly decreases, but the integrity of the test block is good. Under the pressure of the concrete pressure testing machine, the changes of in the compressive strength of the test block with steel fiber reflect are more uniform. However, after the test piece is damaged due to the pressure, the surface of the test block is more seriously damaged, as is shown in Fig. 11. (a) Ordinary concrete (b) Concrete with carbon fiber (c) Concrete with steel fiber Figure 11: Damage situation of the two different test blocks after the pressure test As can be seen from Fig. 11, (a) the compressive process of the ordinary concrete is clearer, and the pressure value decreases uniformly before the destruction, in line with the general law of the damage of the ordinary concrete; (b) the