Table 2 Mix proportion and properties of concrete for the mock-up beam experimentsTable 3 Relative strength at the age of demolition. (161-day)Compressivestrength ratio tocontrol (W/C=60%)W/C(%)60201613Fig. 9 The crushing blade for loadingTensile strength/compressivestrength (%)8.53.83.62.71.03.74.15.13.2 Crushing loading test (laboratory experiment)(1) Outline of experimentFig. 8 Specimen of the laboratory test─ 5 ─Tensile strengthratio to control(W/C=60%)1.01.71.71.6described in the section 2.1(1), except for the Portland cement manufactured by company M and silica fume manufactured by company E used for the specimen with a W/C of 20%.The results of the compressive and tensile strength tests at the material age of 28-day and at the time of crushing experiment (161-day) are also shown in Table 2.With respect to the control concrete with a W/C=60%, the compressive strength ratio of each concrete, tensile strength and the tensile strength/compressive strength (%) of the same concrete, are shown in Table 3.Compared to the development of compressive strength associated with a decrease in W/C, the development of tensile strength was small. When the development of compressive strength became 5.1 times, the tensile strength developed only about 1.6 times. It is therefore advantageous for the demolition of ultra-high-strength concrete to apply tensile load with ingenuity.The crushing test was performed with a load device having the maximum load of 4000kN. Fig. 8 shows the installation of a specimen in the load device. The crushing blade manufactured by company S13) (Fig. 9) was attached to the
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