PSI - Issue 13

N.S. Selyutina et al. / Procedia Structural Integrity 13 (2018) 705–709 Author name / StructuralIntegrity Procedia 00 (2018) 000 – 000

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4. Concrete

The incubation time is a measure of the reaction of materials subjected to dynamic loading. Discussed in Section 3, the behaviour of incubation times of dry and saturated rocks (granite, tuff) has the same dependence on saturation ratio. It is plotted these dependences for concrete on static and dynamic experiments by Zhou and Ding (2014); Cadoni et al. (2001); Reinhardt et al. (1991); Brara and Klepaczko (2006) using split Hopkinson pressure bars, values of incubation times were calculated according to criterion (1). Zhou and Ding (2014) used specimens of concrete with the following saturation ratios: 0%, 52%, 87%, 92%, 100%. Cadoni et al. (2001) were conducted dynamic tests with three types of the saturation ratio: 0%, 50% and 100%. Reinhardt et al. (1991) and Brara and Klepaczko (2006) investigated of concrete with limiting values of saturation ratio: 0% and 100%. The increase of incubation time of concrete on the saturation ratio is observed in each experiment, presented in Fig.2. The greater incubation time with maximum value of the saturation ratio in the material is given the higher limiting tensile stress. Thus, we can predict behavior of the incubation time of concrete and rocks depending on saturation level which provides the possibility to evaluate average ultimate stress for a wide range of applied loads.

Fig. 2. The calculated values of incubation times of concretes depending on saturation ratio on the basis of experimental data by Zhou and Ding (2014); Cadoni et al. (2001); Reinhardt et al. (1991); Brara and Klepaczko (2006).

5. Conclusions

The incubation time criterion (1) is utilized in order to describe material strength in the case of dynamic and static loading. Temporal dependences of strength of the investigated concrete and rocks, which were constructed on the basis of the incubation time criterion, turned out to be in a good agreement with experimental data. The dominant influence of incubation processes in the granite and tuff at high-rate loading and the effect of hydrostatic pressure at static loading were compared. The competitive inversion effect of ultimate stress for dry and wet granite was explained in terms of the incubation time approach. Dependences of incubation times of various concretes on a saturation ratio were calculated. Thus, parameters of the incubation time criterion can be considered as a convenient tool to evaluate an effect of the saturation ratio and the ratio of water to cement and to predict a related effect of inversion of the ultimate stresses with growing loading rate.