Table 1 Mix proportion and properties of concrete for the laboratory experimentsFig. 1 Loading method for the cubic specimen (flat head loading and four-point hemispherical head loading)Fig. 2 Loading method for the cylindrical specimen (flat head loading, single-point flat and single-point hemispherical head loading)more, the ordinary Portland cement (company M), river sand of the Ooi river system (surface dry density 2.63g/cm3), river gravel of the Ooi river system (surface dry density 2.64g/cm3) were used, while silica fume premix cement (Company M), Iibuchi crushed stone (surface dry density 2.62g/cm3), and Iibuchi crushed sand (surface dry density 2.65g/cm3) were used when W/C was 20% or less. As shown in Table 1, the chemical admixture of No. 70/SP-8N/303A by the company B and SSP-104 by the company T were used. The mixing water was Narashino City tap water. Concretes were molded both in a 150×150×150mm cubic specimen steel form and a φ100×200mm cylindrical specimen form.(2) Curing conditionsThree days after placing, specimens were removed from the mold, and then sealed and cured in a high temperature chamber at 60°C.(3) Compressive strength testA compressive strength test was conducted at the material age of 28-day according to JIS A 1108 “Compression test method for concrete”. As shown in Fig. 1, the 150×150×150mm cubic specimen was subjected to flat head loading and four-point hemispherical head loading, while flat head loading, single-point flat loading and hemispherical loading, as shown in Fig. 2, were applied for the φ100×200mm cylindrical specimen.(4) Splitting tensile strength testSplitting tensile strength test was performed at 28-day after placing according to JIS A 1113 “Test method for splitting tensile strength of concrete”.loadFig. 3 shows compressive load applied to the 150×150×150mm cubic specimen using the flat head loading and four-point hemispherical head loading, and that applied to the φ100×200mm cylindrical specimen using the flat head loading, single-point flat head loading and one-point hemisphere head loading. Fig. 4 shows compressive strength and splitting tensile strength. Compared to the flat head loading, single-point loading was able to break specimens with a smaller load.In the case of the 150×150×150mm cubic specimen subjected to the four-point hemispherical head loading, the fracture load increased as the W/C decreased, but the dependency was not significant.In the case of φ100×200mm cylindrical specimen subjected to the single-point hemispherical head loading having a small loading area, the fracture load was the lowest, and the compressive fracture load was 100kN or less even when the W/C was13%.The splitting tensile strength did not increase much even when the W/C was low, and the splitting tensile strength was 10N/mm2 or less.(2) Relationship between loading method and compressive load ratioFig. 5 shows the compressive load ratio of four-point 2.2 Results and discussion(1) Relationship between loading method and compression ─ 2 ─
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