Issue 46

J. Liu et alii, Frattura ed Integrità Strutturale, 46 (2018) 352-360; DOI: 10.3221/IGF-ESIS.46.32 354 CT DAMAGE LOCATION TEST IN CONCRETE UNDER UNIAXIAL COMPRESSION he process of cracks propagation was observed with X-ray CT scan detection system in State Key Laboratory of coal mining, China University of Mining and Technology (Beijing), 3000kN ultra high rigidity servo testing machine under uniaxial compression, the schematic diagram of the test system is shown in Fig. 1. Figure 1: Sketch of experimental system. Different amount air entrained agent was added when making concrete blocks, then 4 groups concrete specimens, with initial porosity of 1.1%, 3.3%, 6.7% and 9.2%, were obtained to utilize in this test. The hight and the radium of the concrete cylinder blocks are 190mm, 50mm. The mix proportion of concrete specimens used in the test is shown in Tab. 1. The amount of materials in per cube meters concrete Cement (kg) Water (kg) Sand (kg) Coarse aggregate (kg) 327 189 755 1133 Table 1: Mix proportion of concrete specimens in test. Displacement control methods was used in the test and its laoding rate was 0.2mm/min. The scanning work was done in the range of upper 100mm, and it is needed add that the scanning interval is 0.2mm. Repeat the work like this until test specimens reach the peak strength. Continue with the loading after the scanning. The loading curve of the test is shown in Fig. 2. The acoustic emission machine was introduced to collect the test data in the whole loading process. Figure 2: Loading-time curve. As shown in Fig. 2, 5 cyclic loading tests were carried out on concrete test specimens, and the loading interval was 30KN in every two adjacent loads, finally the ultimate strength was 134KN. T