纳米碳纤维增强混凝土抗冻性能试验

对六种不同纳米碳纤维掺量的72个纳米碳纤维/混凝土试件进行了慢冻融循环试验，通过测量纳米碳纤维/混凝土经不同冻融循环次数作用后的抗剥落能力、质量损失率、相对动弹性模量和抗压强度损失率，研究了纳米碳纤维掺量对纳米碳纤维/混凝土抗冻性能的影响。另外进行了纳米碳纤维/混凝土的FE-SEM试验和压汞试验，分析了纳米碳纤维对纳米碳纤维/混凝土抗冻性能的微观改性机制。结果表明：纳米碳纤维通过改善混凝土的微观形貌，细化其孔隙结构，提高其整体性和密实度，显著改善了混凝土的抗冻性能；纳米碳纤维掺量为3vol%时，纳米碳纤维/混凝土的抗冻性能最佳。同普通混凝土相比，300次冻融循环后，纳米碳纤维/混凝土的相对动弹性模量提高了33.2%，抗剥落能力显著增强；相同冻融次数下，随着纳米碳纤维掺量的增加，纳米碳纤维/混凝土相对动弹性模量和抗压强度损失率均先增大后减小，质量损失率先减小后增大。但纳米碳纤维掺量最大为5vol%时，纳米碳纤维/混凝土的抗冻性能仍优于普通混凝土；冻融循环次数越多，纳米碳纤维对混凝土抗冻性能的改善作用越显著。

Anti-freeze performance test of nano carbon fiber reinforced concrete

The slow-freeze-thaw cycle test was carried out on 72 nano carbon fiber/concrete specimens with 6 different nano-carbon fiber contents, the effects of nano-carbon fiber content on the anti-freezing performance of nano carbon fiber/concrete were studied by measuring the anti-flaking ability, mass loss rate, relative dynamic elastic modulus and compressive strength loss rate of nano carbon fiber/concrete after different freeze-thaw cycles. In addition, with the help of FE-SEM electron microscopy and mercury intrusion test, the improvement mechanism of nano-carbon fiber on the anti-freezing performance of concrete were analyzed from the microscopic level. The results show that nano carbon fiber can improve the frost resistance of concrete by improving the micro-morphology of concrete, refining its pore structure, improving its integrity and compactness, and improving the frost resistance of concrete. When the content of nano carbon fiber is 3vol%, the anti-freezing performance of concrete is optimized. Compared with ordinary concrete, after 300 freeze-thaw cycles, the relative dynamic elastic modulus of nano carbon fiber/concrete increases by 33.2%, and the anti-flaking ability is significantly enhanced. Under the same number of freeze-thaw cycles, with the increase of nano carbon fiber content, the relative dynamic modulus and compressive strength loss rate of nano carbon fiber/concrete shows a trend of increasing first and then decreasing, and the mass loss rate shows a trend of decreasing first and then increasing. However, when the nano carbon fiber content is up to 5vol%, the frost resistance of nano carbon fiber/concrete is still better than that of ordinary concrete, and the more the number of freeze-thaw cycles, the more significant the effect of nano carbon fiber on the antifreeze performance of concrete.