Dynamic mechanical characterization of frozen concrete

To study the dynamic response characteristics of cryogenically treated cementitious composites, a 75 mm diameter split Hopkinson pressure bar apparatus combined with NMR spectroscopy was utilized to evaluate temperature-dependent mechanical behavior and pore water phase transitions. Fracture patterns were quantitatively assessed through fractal dimension analysis, while a statistically based damage evolution model integrating phenomenological principles, D-P yield criteria, and Weibull probability functions was established. Experimental findings reveal that concrete pore structures are primarily composed of microscopic voids, with ice formation temperatures showing inverse correlation to pore dimensions. Substantial water crystallization occurs in larger cavities between -10°C and -20°C, whereas below -30°C, the phase change process decelerates. Material strength parameters demonstrate temperature dependence, with maximum compressive stress and stiffness modulus rising as thermal conditions decrease, accompanied by reduced failure deformation and significant strain rate sensitivity. Fractographic analysis indicates enhanced structural integrity at lower temperatures, manifested through larger fragment dimensions and diminished damage propagation. The developed constitutive model successfully captures temperature-strain rate coupling effects on mechanical response, showing strong agreement between numerical simulations and empirical measurements. Model coefficients exhibit decreasing thermal dependence but increasing strain rate correlation, verifying its applicability for characterizing cryogenic concrete behavior.