Temperature response and mechanism of mechanical properties of polyurethane concrete
The static and dynamic mechanical properties of polyurethane concrete were studied in the tempera-ture range of-25-75 ℃.Electron backscatter diffraction(EBSD)and Fourier-transform infrared spectrosco-py(FT-IR)were used to study the influence of temperature on the mechanical properties of polyurethane con-crete.The results indicate that elevated temperatures significantly reduce the compressive strengths,tensile strengths,and the elastic modulus of polyurethane concrete.The most notable changes in mechanical proper-ties occur between 25 ℃ and 50 ℃,where both the axial compressive strength and elastic modulus experience reductions exceeding 30 MPa and an order of magnitude,respectively.It is attributed to the transition of poly-urethane from a glassy state to a viscoelastic state within this temperature range.Additionally,the dynamic mechanical properties of polyurethane concrete exhibit frequency dependence.When the frequency is increased from 10 Hz to 120 Hz,the glass transition temperature rises from 66.51 ℃ to 74.41 ℃.The FT-IR test con-firms that hydrogen-bonded functional groups gradually weaken as the temperature increases,indicating a pro-gressive dissociation of internal hydrogen bonds in polyurethane.This leads to a decreased degree of micro-phase separation between the soft and hard segments.
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