【作者】 刘涛；

【导师】 孙明清；

【作者基本信息】 武汉理工大学 ， 固体力学， 2013， 硕士

【摘要】 机敏混凝土作为一种水泥基复合材料,与混凝土结构具有天然的相容性和同寿命性,还具有造价低、课大规模布设等特点,可以满足土木工程结构长期健康监测的需要,已成为该领域的热点和前沿研究方向。水泥基导电复合材料应变自感知性能是基于电阻变化率与应变的对应关系,即压阻特性。本文针对现阶段机敏混凝土研究存在的问题,提出了制备以掺入细钢纤维和石墨为导电相材料的水泥基复合材料,从其制备工艺,电学性能,力学性能,压敏性和纤维界面等方面进行研究。本文的主要成果及创新之处如下：1)研究不同硅粉掺量对混凝土的流动性和抗压强度的影响。当硅粉的掺量小于25%时,随着硅粉掺量的增加,水泥砂浆的强度呈不断增长趋势,其中25%硅粉掺量的水泥砂浆强度达到了80.1MPa。而继续增加硅粉的掺量,会发现水泥砂浆的强度反而下降了。而硅粉对砂浆的流动性有一定的反作用,硅粉还能提高混凝土的早强强度。2)在硅粉混凝土中掺入石墨,研究不同石墨掺量对混凝土的抗压强度,导电性能和压敏性的影响。随着石墨掺量的增加,材料的抗压强度不断减小。随着石墨掺量的增加材料的电阻不断减小,当石墨掺量为15%时,电阻率陡降,再增加石墨的掺量,电阻基本不变,具有明显的渗流现象,故此材料的渗流阈值是石墨掺量为水泥质量的15%。当石墨掺量达到20%后,材料具有一定压敏性,其压敏灵敏系数为12。3)在硅粉混凝土中复掺细钢纤维和石墨,研究此材料的导电性,抗压强度和压敏性。在掺入同量的石墨的条件下,复掺纤维和石墨的水泥基复合材料的导电性能,抗压强度和压敏性均优于单掺石墨的水泥基复合材料。其中当石墨掺量为水泥质量15%,纤维掺量为总体积0.5%时,材料的压敏灵敏系数为517。4)通过单根纤维拔出实验,发现在纤维逐渐被拔出的过程中,纤维和基体的界面渐渐被破坏从而导致纤维和基体的界面电阻越来越大。通过受压材料界面应力传递机理的理论计算,发现纤维在混凝土中通过剪切作用提高混凝土的横向抗拉能力。更多还原

【Abstract】 As a kind of cement-based composites, smart concrete presents many characteristics, such as high durability and excellent compatibility with concrete structures themselves, as well as cheap and large-scale-distributed embedded and so on. Therefore, it has been more and more attractive for structural health monitoring in civil infrastructures due to its promising performance in long-term service, and has become an attractive topic and cutting-edge research in the field. At the existing problems on the smart concrete, this thesis focuses on the research of cement-based composite materials containing graphite. For the problem for smart concrete research at the current stage, cement-based composites have been developed that incorporate copper-coated steel fiber and graphite as conductive paste materials. It has been studied on preparation technology, electrical properties, mechanical properties, piezoresistivity and fiber surface. The main achievements and innovations are as follows:1) This study revealed the influence of different silicon powder content on the fluidity and compressive strength of concrete. It was suggested that with the increase of dosage of silicon powder, the strength of the cement mortar was growing when the amount of doped silicon powder was less than25%. The amount of doped silicon powder was25%, the strength of cement mortar was80.1MPa. The strength of cement mortar decreased with the dosage of silica fume increasing. It had a certain adverse effect on the liquidity of silicon powder of cement morta and improve the early strength of the concrete.2) With the increase of graphite content, the compressive strength and the resistance of materials decreased continuously. When the graphite content was15%, the resistance rate is sharply down. And then increase the content of graphite, the resistance was essentially the same and the obvious percolation phenomenon come up. Therefore the material seepage threshold graphite content was15%of the cement quality. When the graphite content reached20%, the certain piezoresistivity was evident and the material has a certain pressure-sensitive, and the Sensitivity of piezoresistivity is12.3) Electrical conductivity, compressive strength and piezoresistivity of the concrete mixed copper-coated steel fiber and graphite were studied. Under the condition of mixed with the same amount of graphite, electrical conductivity, compressive strength and piezoresistivity of mixed fiber and graphite in cement-based composites were superior to the only graphite doped. When the proportion of graphite content is15%of cement quality, the fiber content of the total volume is0.5%, the Sensitivity of piezoresistivity is517.4) The interface of the fiber and matrix was gradually destroyed that resulting in increasing the interfacial resistance of the fiber and matrix when the fiber was gradually pulled out. Theoretical calculations of interfacial stress transfer mechanism through compression were done and found that the transverse tensile strength of concrete was improved through shearing of fiber in concrete.更多还原