Issue 41

S. Zhao et alii, Frattura ed Integrità Strutturale, 41 (2017) 412-423; DOI: 10.3221/IGF-ESIS.41.52 414 Experimental study on mechanical properties of test piece of fiber-reinforced concrete In this study, the compressive strength and anti-splitting strength of the test blocks are investigated by using the mixing ratio of the material in the concrete of the energy pile. The contents of fiber, graphite, copper slag, and fine aggregate are taken as the main factors, of which each factor is divided into three levels. This can be seen in Tab. 1. Factor Level A Carbon (steel) fibers (V%) B Graphite(Kg/m 3 ) C Copper slag (V%) D Fine aggregate (V%) 1 2 3 0.0 (0.0) 0.25 (0.5) 0.5 (1.0) 0.0 1.0 2.0 0.0 2.0 4.0 0.0 2.0 4.0 Table 1: Factors and levels. According to the factors and the levels, an L 9 (3 4 ) orthogonal table is used, and the corresponding quality of each factor is determined to obtain orthogonal tests seen in Tab. 2. Columns No. Test No. A Carbon (steel) fibers(g) B Graphite(g) C Ordinary (Composite) copper slag (g) D Ordinary (Composite) fine aggregate (g) 1 0(0) 0 0(0) 5.64(5.34) 2 3 0(0) 0(0) 0.84 16.8 138.3(131.2) 276.5(262.4) 5.53(5.20) 5.42(5.07) 4 37.8(372.6) 0 138.3(131.2) 5.53(5.20) 5 37.8(372.6) 0.84 276.5(262.4) 5.42(5.07) 6 37.8(372.6) 16.8 0(0) 5.64(5.34) 7 75.6(655.2) 0 276.5(262.4) 5.42(5.07) 8 75.6(655.2) 0.84 0(0) 5.64(5.34) 9 75.6(655.2) 16.8 138.3(131.2) 5.53(5.20) Table 2: Orthogonal Test Table. In the table, Ordinary refers to ordinary Portland cement and Composite means composite Portland cement. In this test, 2.97 kg of the ordinary Portland cement are used together with 1.78 kg of water. Moreover, 3.86 kg of composite Portland cement are mixed with 1.78 kg of water. Experiment on mechanical properties of the concrete and results analysis In accordance with the mixing ratio of the material in Tab. 2, 36 groups of test blocks of different mixing ratios are made. Each group with the same mixing ratio includes 6 blocks, which means 216 blocks are made in this experiment, which are to be used for the compressive strength and the anti-splitting experiments. The test results of the compressive strength are recorded in Tab. 3. Figs. 3 and 4 show the relationship between the factors, the levels, and the K values in the compressive strength test when the ordinary Portland cement is used as the cementitious material and the carbon fiber and the steel fiber are selected as the fiber material. According to the conventional analysis of the orthogonal test, it can be seen that A is the carbon (steel) fiber, B is the graphite, and C is the scrap copper slag. In the course of the test, with the amount of these three materials increasing, the corresponding curves of the pile strength of K1, K2, and K3 can be seen in the figures. In Fig. 3, in the case of A, for example, when the amount of fiber is increasing, the pile strength K1 to K3 are is gradually reduced, and it can be concluded that when the content of this fiber increases, the compressive strength of the concrete is negatively impacted, and tends to decrease; the amount of B has little effect on the strength of the test blocks, and the strength slightly increases at Level 3. In Fig. 4, it can be intuitive to seen that when the ordinary Portland cement is selected as the cementitious material, combined with the steel fiber in the reinforced experimental group, the strength does not significantly decrease when the steel fiber content increases, but slightly improves. According to the data, we can