摘要
导电混凝土既能用于道路、机场跑道的融冰化雪,又能用于建筑采暖、结构的裂纹监测等方面。开展导电混凝土材料的研究工作有着非常现实的重要意义。从适应社会发展的需要和节约资源的角度出发,本文构建了两种新型的导电混凝土-炭黑轻集料混凝土和复掺炭黑/碳纤维轻集料导电混凝土。分别对这两种新型导电混凝土的制备工艺、力学和电学性能以及电阻随荷载的变化规律进行了较系统的研究,具体研究内容和结论如下:
(1)通过比较不同种类的导电炭黑、不同炭黑分散剂配比、龄期等对轻集料导电混凝土导电性的影响,确定了炭黑轻集料导电混凝土的制备方法。配制的导电混凝土具有渗流导电特征,滤渗阈值约为0.83vol%。抗压强度随着炭黑掺量的增加呈现先增大后降低的趋势,而密度随着炭黑体积掺量的增加而减小。当炭黑掺量为1.94vol%,胶砂比为2.43-5.2时,抗压强度能达到34~38MPa,电阻率稳定,但是拌合物加工困难,和易性较差。
(2)为进一步提高导电混凝土的力学性能,通过研究比较5种不同的炭黑/碳纤维轻集料导电混凝土的制备工艺,得出了采用水溶性碳纤维薄毡制备碳纤维/炭黑轻集料导电混凝土的较好工艺。炭黑轻集料混凝土的电阻率都随着碳纤维的增加而降低。导电相总体积比单掺炭黑的量要少,而且拌合物具有更好的和易性。
(3)研究了炭黑/碳纤维轻集料导电混凝土的抗弯折性能,表明碳纤维对炭黑轻集料混凝土有一定的增强增韧作用。抗折强度随着胶砂比的增大而增大,当胶砂比达到2.0时,抗折强度达到5.7MPa,此后抗折强度变化变得很小。结合抗折、抗压和导电性要求,得出能基本满足融雪化冰路面材料要求的轻集料导电混凝土配合比。
(4)炭黑/碳纤维轻集料导电混凝土单调加载试验表明,在达到弯曲极限载荷之前,电阻变化率呈逐渐线性减小的趋势。胶砂比越大,电阻率越小,电阻变化率的幅度也逐渐的减小。
Conductive concrete can apply for both deicing or melt snowing of road,airport runways and for heating, structural monitoring and so on.It is very real significant to carry out the work of conductive concrete materials.To adapt to the needs of social development and conservation resource.This thesis construct two new conductive concrete-black lightweight aggregate concrete and re-doped carbon black/carbon fiber lightweight aggregate concrete.Preparation processs,mechanical and electrical prop-erties and resistance variation with load of the two new conductive concrete were researched systematicly. The main researching content and results are as follows:
(1) A better preparation process of carbon black lightweight aggregate concrete was obtained by comparing the effect of the different kinds of conductive carbon black, carbon black dispersions in different ratio, age on the electrical conductivity of the lightweight aggregate concrete. Carbon black lightweight aggregate concrete had electrical percolation phenomena and percolation threshold was about 0.83vol%. Compressive strength increased with increasing carbon content at first and then decreased, while the material density decreased with increasing the volume content of carbon black. When the carbon black content was 1.94vol%, cement-sand ratio of 2.43 to 5.2, the compressive strength can reach 34 to 38MPa, and resistivity was stabile, but the poor workability and processing difficulty.
(2) To further enhance the mechanical properties of conductive concrete, a good process that using water-soluble carbon fiber Thin felt to prepare carbon fiber/ carbon black conductive lightweight aggregate was obtained by comparing 5 different preparation process of carbon black/carbon fiber conductive lightweight aggregate concrete. The resistivity of black lightweight aggregate concrete was decreased with the increase of carbon fiber. The total volume amount of carbon black and carbon fiber is less than that of single-doped carbon black, and mixing has better workability.
(3) The bending properties of carbon black/carbon fiber lightweight conductive was studied. The result indicated that carbon fiber has a certain role in strengthening and toughening to black lightweight aggregate concrete. The bending strength of concrete increases with increasing cement/sand ratio, when the cement/sand ratio is 2.0, the bending strength reach 5.7MPa,but then become a very small change in bending strength. A mix of meeting the requirement of deicing or snow melting material was obtained according the requirements of bending, compression, and electrical conductivity.
(4) The experiment that carbon/carbon fiber conductive lightweight aggregate concrete was loaded monotonously show that the resistance change rate decreased linearly before reaching limit load. The larger cement/sand ratio and the smaller the resistance,the smaller the range of resistance change rate.
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