冻融损伤后钢筋与再生混凝土黏结滑移性能试验研究

STUDY ON BOND-SLIP PROPERTIES BETWEEN STEEL BARS AND RECYCLED CONCRETE AFTER FREEZE-THAW CYCLES

  • 摘要: 对经过0次、25次、50次、75次、100次冻融循环作用后的再生混凝土(粗骨料取代率100%)进行拉拔试验研究,得出不同冻融循环次数、保护层厚度和锚固长度下钢筋与再生混凝土间黏结性能的变化规律。结果表明:随着冻融循环次数的增加,钢筋与再生混凝土间的黏结强度逐渐降低,而滑移值逐渐增加;黏结强度随着相对保护层厚度的增加而增大且呈线性关系,随着相对锚固长度的增加,黏结强度却随之减小,当相对保护层厚度和锚固长度增加到一定值后,黏结强度基本保持不变。基于试验结果给出黏结-滑移曲线,曲线分为微滑移线性阶段、滑移阶段、滑移加速阶段、非线性下降段和残余阶段等5个阶段。通过分析试验数据提出不同影响因素下各阶段黏结锚固特征值的拟合计算公式,为我国冻融环境下再生混凝土结构的耐久性设计提供参考。

     

    Abstract: Pull out tests of steel bars in recycled concrete after 0, 25, 50, 75 and 100 freeze-thaw cycles are carried out for recycled concrete of 100% recycled coarse aggregate. The influences of freeze-thawing cycle numbers, cover thickness and anchorage length are analyzed. The results show that the bond strength decreases and the slip increases gradually with the increase of the numbers of freeze-thaw cycles; the bond strength is proportional to the increase of relative cover thickness and it is inversely proportional to the anchorage length. However, when the relative cover thickness and the anchorage length increases to a certain value, the bond strength remains almost constant. The bond-slip curve of recycled concrete can be divided into five sections, that is, micro-slip, slip, slip speed-up, inelastic descending and residual stage. Based on the analysis of the experimental data, an empirical formula for characteristic values under different influential factors is proposed, which may provide reference for durability design of structures composed of recycled concrete in freeze-thaw environment.

     

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