高温后高延性混凝土的抗压性能及微观结构

Compressive properties and micro-structure of high ductility concrete exposed to elevated temperature

  • 摘要: 为研究高温后高延性混凝土(HDC)的抗压性能,考虑温度、冷却及养护方式、静置时间三个因素设计了49组立方体试件,并测试其抗压强度。通过5组棱柱体试件的超声回弹试验,探讨HDC抗压强度、经历最高温度与超声波速和回弹值的相互关系。结果表明:温度对抗压强度影响较大,随着温度升高,抗压强度降低;温度低于200℃时,冷却方式的影响不可忽略;温度为400℃时,静置时间对自然冷却试件也有较大影响。超声回弹试验表明,HDC抗压强度与超声波速和回弹值有良好的相关性;通过回归分析,建立了高温后HDC测强曲线及推定其经历最高温度的公式。借助XRD、SEM和热重-差热分析(TG-DSC)等试验,揭示了高温对HDC力学性能影响的微观机制。

     

    Abstract: In order to study the compressive properties of high ductility concrete (HDC) exposed to elevated temperature, 49 groups of cubic specimens were designed considering three factors:temperature, cooling and curing mode, and standing time. And their compressive strength was tested. The relationship among compressive strength, maximum temperature, ultrasonic velocity and rebound value of HDC was studied by ultrasonic rebound test of five groups of prism specimens. The results show that the temperature has significant impact on compressive strength, and with the increase of temperature, the compressive strength decreases; the influence of cooling mode cannot be neglected when the temperature is below 200℃ and the standing time has a great impact on the natural cooling specimens when the temperature is 400℃. Ultrasonic rebound test shows that the compressive strength of HDC is well correlated with the ultrasonic velocity and rebound value. Based on the regression analysis of test data, the strength curve of HDC exposed to elevated temperature and the formula for estimating the highest exposure temperature were established. The effect mechanism of elevated temperature on the mechanical properties of HDC was revealed by using XRD, SEM and thermogravimetric-differential thermal analysis (TG-DSC).

     

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