不同形态硅灰在高强混凝土中的作用机理

发布时间：2018-03-27 19:06

本文选题：加密硅灰　切入点：原状硅灰　出处：《清华大学》2015年硕士论文

【摘要】：在高强混凝土的材料组成中,硅灰通常是必不可少的组分。由于硅灰密度小,易飞扬,使其运输、储存与使用较困难。近年来,我国市场上用于混凝土生产的硅灰大部分已改为加密硅灰。本文通过对比加密硅灰和原状硅灰的差异,重点研究了不同形态的硅灰在水泥基材料水化硬化过程中的作用机理、对硬化胶凝材料浆体和混凝土微结构的影响规律和对不同水泥基材料体系强度性能的影响。得出了以下结论:(1)加密硅灰对于不同硬化水泥基材料体系的早期强度发展的促进作用不明显;随着龄期增长,掺硅灰的水泥基材料的强度发展更快,掺加硅灰明显提高了水泥基材料的28 d抗压强度,加密硅灰对水泥基材料后期强度发展的促进作用逐渐减弱。(2)早期高温养护对硅灰的活性有明显激发作用,促进了硅灰在胶凝材料体系中的反应活性,这种激发作用主要集中在水化开始后最初72小时内,但是对水泥基材料后期强度发展有不利影响。(3)在胶凝材料净浆中,存在直径10~50μm的硅灰团簇,原状硅灰的分散情况优于加密硅灰,这些硅灰团簇内部未发生水化反应,可能成为净浆浆体内的薄弱区域,使硅灰的增强作用不明显。在混凝土中,不同密度的硅灰分散情况均比较良好。(4)硅灰会降低硬化胶凝材料体系中Ca(OH)_2晶体的含量,细化硬化浆体内部孔隙,有效改善其孔结构。由于加密硅灰在胶凝材料浆体中的分散情况不如原状硅灰,所以加密硅灰对于硬化浆体微观结构的改善作用也弱于原状硅灰。(5)硅灰能够减小界面过渡区中Ca(OH)_2晶体的取向程度,明显改善浆体与骨料间的过渡区结构,提高界面的粘结强度。
[Abstract]:Silica fume is usually an essential component in the material composition of high strength concrete. Because of its small density and easy to fly, it is difficult to transport, store and use it. Most of the silica fume used in concrete production in our country has been changed into encrypted silica fume. By comparing the difference between encrypted silica fume and undisturbed silica fume, the mechanism of different forms of silica fume in the hydration and hardening process of cement-based materials has been studied in this paper. The effects on the mortar and concrete microstructure of hardened cementing materials and on the strength and properties of different cement-based material systems are discussed. The following conclusions are drawn: 1) early strength of infilled silica fume for different hardened cement-based material systems. The promoting effect of development is not obvious; With the increase of age, the strength of cement-based materials doped with silica fume developed faster, and the compressive strength of cement-based materials increased obviously with the addition of silica fume. The effect of infilled silica fume on the later strength development of cement-based materials is gradually weakened. (2) early high temperature curing has an obvious stimulating effect on the activity of silica fume, which promotes the reaction activity of silica fume in the cemented material system. The excitation was mainly concentrated within 72 hours after hydration, but had a negative effect on the later strength development of cement-based materials, and there were 1050 渭 m silica fume clusters in the cement paste. The dispersion of the raw silica fume is better than that of the encrypted silica fume. There is no hydration reaction in these silica fume clusters, which may become the weak area in the slurry, which makes the enhancement of silica fume not obvious. The silica fume with different density can decrease the content of Ca(OH)_2 crystal and refine the porosity of hardened paste. Improve the pore structure effectively. Because the dispersion of the encrypted silica fume in the cement paste is not as good as the original silica fume, Therefore, the effect of encrypted silica fume on the microstructure of hardened paste is also weaker than that of raw silica fume. 5) silica fume can reduce the orientation of Ca(OH)_2 crystal in the interfacial transition zone, improve obviously the structure of transition zone between slurry and aggregate, and increase the bond strength of interface.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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