纳米改性混凝土的抗盐冻性能及其改性机理研究

发布时间：2018-05-02 16:28

本文选题：混凝土 + 纳米改性　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：利用纳米材料对混凝土进行改性以提高混凝土的性能,特别是抗盐冻性能已被认为具有可行性和广泛前景。本文使用Si O2、纳米Al2O3、纳米Fe2O3以及纳米Ti O2四种纳米材料,掺量为水泥质量的0.05%、0.1%、0.5%和1.0%,对水灰比为0.5的混凝土进行改性,测试了纳米改性混凝土的和易性、力学性能、抗渗性以及抗盐冻性能等,并且利用SEM和EDS等手段对其改性机理进行了分析。试验采用先将纳米材料在减水剂溶液中超声分散后,再与干料一同拌合的方法制备混凝土。研究结果表明,当掺量不大于1.0%时,纳米材料的掺入对混凝土的和易性,特别是流动性无明显影响。四种纳米材料均可以提高混凝土的力学性能,且均呈现随着掺量的增加,混凝土的力学性能随之提高的趋势,当掺量达到1.0%时,四种纳米改性混凝土的抗压强度和抗折强度均提高10%以上。四种纳米材料中,纳米Si O2和纳米Ti O2对混凝土力学性能的提升作用相对较强,而纳米Fe2O3对混凝土的力学性能的改善幅度最低。在Na Cl、CH3COOK和Ca Cl2三种盐环境下对纳米改性混凝土进行冻融循环测试。发现在三种盐冻环境下,纳米改性混凝土均基本呈现,随着掺量的增加,混凝土的质量损失率随之降低,相对动弹性模量随之升高的趋势,既纳米材料的掺量越大,混凝土的抗盐冻性能越好,1%为抗盐冻性能最佳掺量。对比四种纳米材料对混凝土抗盐冻性能的改善作用,纳米Si O2所起作用较为明显地高于其他三者,纳米Ti O2次之,而剩余的纳米Al2O3和纳米Fe2O3两者中,纳米Al2O3的改善作用相对最弱。而利用电通量法测试纳米改性混凝土的抗渗性,也得到了与抗盐冻性能相似的结果。纳米改性混凝土的改性机理主要在于掺入纳米材料后,提高了水化产物的数量和种类。水化产物数量的提升可以使混凝土更为致密。纳米Si O2、纳米Al2O3和纳米Ti O2掺入后,出现的针状水化产物,可以以原生纳米纤维的形式起到阻碍混凝土内部微裂纹的发展,使混凝土增强增韧的作用。而掺入纳米Fe2O3后出现的球状水化产物,由于其排列紧密,同样起到了提升混凝土密实度的作用。这些纳米材料的掺入引起的水化过程的优化,最终使得混凝土在力学性能和耐久性方面得到了提升。
[Abstract]:In order to improve the properties of concrete, especially the salt freezing resistance, it is considered feasible and promising to modify concrete with nano-materials. In this paper, four kinds of nanomaterials, Sio _ 2, nano-Al _ 2O _ 3, nanometer Fe2O3 and nano TIO _ 2 were used to modify the concrete with water-cement ratio of 0.5% and 1.0% respectively. The properties of the concrete were tested. Impermeability and salt freezing resistance were analyzed by means of SEM and EDS. The concrete was prepared by ultrasonic dispersion of nanomaterials in water reducer solution and then mixing with dry materials. The results show that when the content of nano-materials is less than 1.0, the incorporation of nano-materials has no obvious effect on the workability of concrete, especially the fluidity of concrete. Four kinds of nanomaterials can improve the mechanical properties of concrete, and the mechanical properties of concrete increase with the increase of the content of concrete. The compressive strength and flexural strength of four kinds of nano-modified concrete are increased by more than 10%. Among the four kinds of nanomaterials, nano-SiO _ 2 and nano-TiO _ 2 can enhance the mechanical properties of concrete relatively strongly, while nano-SiO _ 2 can improve the mechanical properties of concrete by the least extent. The freeze-thaw cycling test of nanocrystalline modified concrete was carried out under three kinds of salt environments: NaClCl CH3COOK and Ca Cl2. It is found that under three kinds of salt freezing environment, nano-modified concrete is basically present, with the increase of content, the mass loss rate of concrete will decrease, and the relative dynamic elastic modulus will increase, that is, the content of nano-material will increase. The better the salt freezing resistance of concrete is, 1% is the best content of salt freezing resistance. Compared with the improvement of salt and freezing resistance of concrete by four kinds of nano-materials, nano-SiO _ 2 plays a more important role than the other three, nano TIO _ 2 takes the second place, while the remaining nano-sized Al2O3 and nanometer Fe2O3 are the second. The improvement of nanometer Al2O3 is the weakest. The permeability resistance of nano-modified concrete was measured by the method of electric flux, and the results were similar to those of salt freezing resistance. The modification mechanism of nano-modified concrete is mainly due to the increase of the quantity and variety of hydration products after the addition of nano-materials. Increasing the number of hydration products can make concrete denser. After the incorporation of nano-SiO _ 2, Al2O3 and TIO _ 2, the acicular hydration products can hinder the development of microcracks in concrete and strengthen and toughen the concrete in the form of primary nanofibers. However, the spherical hydration products after the addition of nanometer Fe2O3 can also enhance the compactness of concrete because of its compact arrangement. The hydration process caused by the addition of these nanomaterials improved the mechanical properties and durability of concrete.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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