碳纳米管对水泥基材料热膨胀性能的影响

在水泥基中掺入不同比例的碳纳米管，制备出碳纳米管水泥基复合材料。测量其在室温~600℃的热膨胀性能，并根据DSC/TG、XRD图谱，孔径分布图和扫描电镜图从微观尺度分析其变化规律的机理。结果表明，从室温到150℃掺入各比例碳纳米管的水泥基复合材料热膨胀率变化趋势相似，热膨胀率为正值而出现微膨胀；150℃~590℃热膨胀率为负值且逐渐减小，试件持续收缩。当碳纳米管的掺量为水泥的0.3%时热膨胀曲线始终在其他掺量之下，热膨胀率达到最小值。这表明，碳纳米管掺量为0.3%的材料水化反应充分，产生大量的水化硅酸钙凝胶，收缩明显、密实度显著提高。掺入0.3%的碳纳米管可有效阻止供暖管道局部混凝土的膨胀，提高结构的耐久性。

Effect of Carbon Nanotubes on Thermal Expansion Properties of Cement-based Materials

Carbon nanotubes of different proportions were added to the cement matrix to prepare cement-based materials, and the thermal expansion property of those materials was measured from room temperature to 600°C. While the materials were characterized by means of DSC/TG, XRD, pore size distribution diagrams, SEM images. The results show that the thermal expansion rate is positive from room temperature to 150°C, there is a slight expansion; the thermal expansion rate is negative and gradually decreases from about 150°C to 590°C, the specimen shrinks continuously. When the blending amount of carbon nanotubes is 0.3%, the thermal expansion curve is always below those with the amounts other than 0.3%, and the thermal expansion rate reaches a minimum value. This shows that when the amount of carbon nanotubes is 0.3%, the hydration reaction is sufficient and a large amount of hydrous calcium silicate gel is produced, and the shrinkage is obvious and the density is significantly improved. Therefore, the content of 0.3% carbon nanotubes can effectively prevent the emerge of abnormal expansion of local area for a heating pipe and therefore, improve the durability of the structure.