Study on mechanical properties and pore structure model of concrete under freeze-thaw action based on grey correlation entropy
In order to study the influence of pore structure on the mechanical properties of concrete during freeze-thaw cycles,the compressive strength,dynamic elastic modulus,scanning electron microscope(SEM),low-field nuclear magnetic resonance(NMR)and other tests of concrete with different freeze-thaw cycles were carried out,and the mathematical model between compressive strength and pore structure during freeze-thaw cycles was established by using the grey correlation entropy method.The results show that with the increase of freeze-thaw cycles,the mechanical properties of concrete decrease obviously,the porosity increases and the total spectral area increases gradually.The two factors that have the greatest influence on the compressive strength during freeze-thaw cycle are the proportion of less harmful pores and free fluid saturation(FFS),and the grey entropy correlation degree is 0.9893 and 0.9952 respectively.The GM(1,3)model is established based on the compressive strength,free fluid saturation and the proportion of less harmful pores.The relative error between the predicted value of the model and the average value of the test is 0.29%,which indicates that the predicted model can provide a formula basis for the mechanical properties of concrete during freeze-thaw cycles.The research results are helpful to deepen the understanding of the damage evolution law of concrete structures during freeze-thaw cycles.
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