Abstract
To study the dynamic mechanical characteristics and constitutive relation of concrete materials under freeze–thaw (FT) cycle conditions, C35 concrete was taken as the research object in this paper, and FT tests were carried out with a freeze–thaw range of −20–20 °C and a freeze–thaw frequency up to 50 times. By using the separated Hopkinson pressure bar (SHPB) system, impact compression tests of concrete specimens under different FT cycle actions were developed, then the dynamic fracture morphology, fracture block distribution, stress–strain curve, peak stress and other dynamic mechanical properties of concrete were analyzed, and the influence law of FT action and strain rate was obtained. Through introducing the freeze–thaw deterioration damage factor and the stress damage variable, the dynamic visco-elastic damage constitutive equation of freeze–thawed concrete was constructed based on component combination theory. Furthermore, the damage evolution process and mechanism of freeze–thawed concrete materials were revealed. The research results show that the dynamic mechanical properties of concrete under a freeze–thaw environment are the combined results of the freeze–thaw deterioration effect and the strain rate strengthening effect. The dynamic visco-elastic damage constitutive model established in this paper can effectively describe the dynamic mechanical properties of freeze–thawed concrete, and has the characteristics of few parameters and good effect. The stress damage evolution path of concrete goes backward with the increase of FT cycles and the development speed gradually slows down. The greater the difference in FT cycles, the greater the difference in stress damage path.
Highlights
The cold areas in China are widely distributed, and the seasonal and permanent cold areas account for more than three quarters of China’s land area
As a kind of material widely used in railway, highway, dam, tunnel and other cold region engineering, concrete will suffer from freeze–thaw damage in the long service of freeze–thaw environment
Petros Petrounias [3,4] and Wojciech Piasta et al [5] studied the effect of coarse aggregate performance on concrete under ordinary temperature and freeze–thaw conditions, respectively, and the results showed that the resistance of the aggregate to freezing and thawing was demonstrated to agree with the values of crushing resistance and the lowest contents of pores with diameters unsafe in terms of the freeze–thaw resistance
Summary
The cold areas in China are widely distributed, and the seasonal and permanent cold areas account for more than three quarters of China’s land area. Sun Ming et al [9] proposed a cohesion reduction parameter and investigated the mechanism of damage evolution and plasticity development of concrete materials subjected to freeze–thaw cycles during the load process. The constitutive model is one of the important bases on which to study the strength and deformation of concrete, and reflects the stress–strain curve, the most basic mechanical property of concrete [12]. The component model is often used to study the dynamic constitutive relation of concrete It is composed of the components in series or in parallel, and it simulates the actual stress–strain relationship by adjusting the parameters and the number of combined components, so that the stress–strain curve of the model is consistent with the test results. The damage evolution process and mechanism of freeze–thawed concrete materials were revealed
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