3.4 Overall look at the crushing demolition of ultra-high-strength concrete membersFig. 14 Strengths of ultra-high-strength concrete normalized with the control with a W/C=60%Table 5 Maximum crushing load of shovel crusher.Maximum hydraulicpressure (MPa)W/C(%)6020161330.030.029.029.5Maximum load atthe head (kN)780780754767─ 7 ─Maximum loadratio to control(W/C=60%)1.001.000.970.98performed in the crushing and demolition process and changing of the biting position and applying the blade to the position of the reinforcing bar, it was possible for concrete by being pushed out from the reinforcing bar all at once due to the occurrence of cracks in the concrete. The crushed concrete pieces were sharply angled.Table 5 shows the maximum hydraulic pressure and maximum crushing load in this experiment. It was obvious that the capacity of the hydraulic shovel was used to the maximum, including in the case of the ordinary concrete.(1) Breaking load ratio of ultra-high-strength concrete specimen (member) to the ordinary concrete specimen (member)Fig. 14 shows the strength and maximum load ratios of ultra-high-strength concrete against those of the ordinary concrete with a W/C=60% at the time of demolition (age of 161-day). It includes compressive strength and tensile strength with a cylindrical specimen of φ100×200mm and maximum crushing loads of mock-up beam members both in laboratory and the actual machine tests.Looking at the strength ratio of W/C=13% concrete, the compressive strength was 5.1 times, but the tensile strength was 1.6 times, and the crushing load in the laboratory experiment was 1.4 times and almost no differences was found in the actual machine experiments. It was found that the current crushing demolition method can be applied to ultra-high-strength concrete members, and that the demolition method by crushing was advantageous as a breaking mechanism for the ultra-high-strength concrete members.(2) Noise and particle scattering during crushingIn the crushing of the ultra-high-strength concrete members, it is not easy for the blade to enter the concrete, and the blade sometimes bounced with explosion noises of high frequency range unlike the level of the ordinary concrete.Similar to the compressive strength test of the φ100×200mm specimen, crushing during demolition accumulated force and broke members at once, so the broken pieces were sharper and had a greater scattering force than that of the ordinary concrete pieces.From the experiment that examined the loading method for the demolition load of high-strength and ultra-high-strength concrete structures, the followings are obtained.(1) Compared to the flat head compression loading, the single-point concentrated loading was able to break specimens at a smaller load.(2) When the shape of the single-point head was hemispherical, the fracture load was smaller than loading with a single-point flat head.(3) The compressive strength of ultra-high-strength concrete (W/C=20% or less) was 6 to 7 times that of the ordinary concrete (W/C=60%), while the ratio of fracture loads when using point loading was about twice.(4) It was confirmed that the tensile strength of ultra-high-strength concrete did not increase unlike the increase in compressive strength level.From the crushing experiment,(5) In the range of water to cement ration of 20% to 13%, it was confirmed that the maximum breaking load in the 4. Conclusions
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