TANAHASHI Isamu Nagoya Institute of Technology, Assistant, 工学部, 助手 (40024252)
TANIGAWA Yasuo Faculty of Engineering, Mie University, Prof., 工学部, 教授 (70023182)
OKAJIMA Tatsuo Nagoya Institute of Technology, Prof., 工学部, 教授 (30024243)
NAGAMASTU Shizuya Faculty of Engineering, Oita University, Prof., 工学部, 教授 (70037828)
The main conclusions on fracture toughness of concrete which cleared in the research project are as follows.
1) On the fructure toughness, <K_(lc)> of cement paste and mortar;
<K_(lc)> of cement paste and mortar depend on the water-cement ratio, (W/C) the sand-cement ratio, (S/C) and the compressive strength. However, the slit wiath of notch, (t) the relative notch depth, (d/D) the grading of sand under 5 mm and the size of cross section of beam has no effect on <K_(lc)> of cement paste., In the mortar, <K_(lc)> is inluenced by the relative notch depth slightly, and it's <K_(lc)> decrease with the contained air void increase at about 3 percent over. From the test results, it was concluded that the liner elastic fracture mechanics (LEFM) is applicable to evaluate of the fracture toughness, <K_(lc)> of hydreted cement paste and mortar.
2) On the fracture toughness, <G_(lc)> of concrete;
The strain energy release rate, <G_(lc)> of concrete was investigated experimentally by three methods as a) the calculation inducing from <K_(lc)> -value, b) the analysical method and c) the comliance method. The effect of notch depth, beam size, aggregate size, volum fraction of coarse aggregate, mixing ratio and contained air volum of concrete on <G_(lc)> was tested. According to the experiment and the analysis based on the three method, the <G_(lc)> takes the near values one other. And the <G_(lc)> of concrete depend on the beam size, beam span length, relative notch depth, air volume and volume fraction of coase aggregate. So, it is considered that LEFM is not appricable to concrete to be exact.