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早齡期凍結土壓力與負溫耦合作用的井壁混凝土性能

Performance of shaft lining concrete under the coupling effect of early-age frozen soil pressure and negative temperature

  • 摘要: 研究了早齡期凍結壓力等荷載、負溫及早齡期荷載和負溫耦合作用對凍結豎井井壁C60混凝土抗壓強度、氯離子擴散系數和聲發射特征的影響,并通過掃描電鏡分析其內部微裂縫.結果表明:早齡期荷載加載時間越早對混凝土28d抗壓強度的影響越大,當外部荷載作用時間在3d以后且荷載水平在混凝土當天強度40%以內時,混凝土28d強度幾乎不受影響;凍結井井幫負溫環境會延緩井壁混凝土早期水化,防凍劑的加入利于加快混凝土水化和強度的發展;在早齡期荷載及負溫耦合作用下,混凝土28d抗壓強度降低明顯,氯離子擴散系數大大增加,混凝土的滲透性由"中"變為"高",內部產生了缺陷和微裂縫導致聲發射"活躍階段"提前,且混凝土呈現明顯的塑性變形.

     

    Abstract: The effects of early-age frozen pressure,negative temperature,and early-age load and negative temperature coupling on the strength,chloride diffusion and acoustic emission characteristic of freezing shaft wall C60 concrete were studied,and the internal microcracks were analyzed by scanning electron microscopy(SEM). It is found that the earlier the early-age load applies,the greater effect it has on the 28 d compressive strength of the concrete. But when the external load is applied 3 d later and the load level is less than 40% of the day's strength,the 28 d compressive strength of the concrete is almost not affected. A negative temperature environment of the freezing shaft wall can delay early concrete hydration,and antifreeze speeds up the development of concrete hydration and strength. Under the early-age load and negative temperature coupling effect,the 28 d compressive strength and durability of the concrete decrease,the chloride diffusion coefficient increases apparently,the concrete permeability changes from middle to high,the internal microcracks and deficiencies lead to advancing the active phase of acoustic emission,and the concrete presents apparent plastic deformation.

     

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