碱激发矿渣微结构优化及性能研究

发布时间：2018-10-18 09:06

【摘要】：碱激发矿渣胶凝材料是一种由磨细水淬高炉矿渣和碱性激发剂混合而成的新型胶凝材料。相比于普通硅酸盐水泥,碱激发矿渣胶凝材料具有水化热低、力学性能发展快、耐久性良好等优异性能,成为替代硅酸盐水泥的胶凝材料之一。但碱激发矿渣胶凝材料具有干燥收缩大、碳化速度快等问题,阻碍了其在工程中推广应用。这些性能缺陷与基体微结构紧密相关,故本文从微结构优化出发,选用纳米材料、火山灰材料及二者复掺,研究这些材料对碱激发矿渣浆体(AASP)的改性作用。本文研究了碱含量及模数变化对AASP的工作性能及力学性能影响用以确定最优配合比,最终优选出的AASP配比：碱含量4.0%,模数1.2,水胶比0.4。第一,基于最优配合比,本文研究了掺量均为矿粉质量的0.5%的金红石型纳米TiO2、锐钛矿型纳米Ti02、纳米SiO2对AASP力学性能、干燥收缩性能以及微结构的影响。研究结果表明：金红石型纳米TiO2的掺入可增强AASP的力学性能尤其是抗折强度。纳米SiO2及锐钛矿型纳米Ti02两组收缩率相近且高于基准值,而金红石型纳米Ti02的掺入则使AASP干燥收缩率降低21.1%。因此,本文选用金红石型纳米TiO2,探究其对AASP微结构的影响。研究发现,金红石型纳米T102的掺入可促进水化反应、使各龄期AASP基体更致密且不影响水化产物种类。且金红石型纳米Ti02的掺入使28d AASP总孔隙率降低至基准组的69.5%,介孔含量降低至59.6%。第二,基于最优配合比,本文采用了偏高岭土、粉煤灰、硅灰,掺量均为矿粉质量的10%并采用内掺和外掺方式,研究其对AASP力学性能、干燥收缩性能以及微结构的影响。研究结果表明：偏高岭土外掺较硅灰内外掺、粉煤灰外掺、偏高岭土内掺而言,能明显提高AASP力学性能及降低干燥收缩。故本文选用偏高岭土外掺探究其对AASP微结构的影响。研究发现,偏高岭土外掺可增加硅酸盐及硅铝酸盐凝胶含量、AFm及沸石类晶体含量,使各龄期AASP基体更加密实。且使28d AASP总孔隙率降低至基准组的46.3%,介孔含量降低至43.1%。第三,基于纳米材料及火山灰材料对AASP的宏观性能改性结果,优选出金红石型纳米Ti02与偏高岭土进行复掺,研究其对AASP性能及微结构的影响。二者复掺使AASP 56d抗折强度及抗压强度分别增加78.9%及26.6%,90d收缩值降低39.9%。且复掺材料掺入可增加硅酸盐凝胶及硅铝酸盐凝胶含量、沸石类产物晶体,使各龄期AASP基体更加密实,使28d AASP总孔隙率降低至基准组的38.2%,介孔含量降低至35.5%。二者外掺对微结构改善及性能优化作用优于单掺金红石型纳米TiO2及外掺偏高岭土。综上所述,金红石型纳米Ti02、偏高岭土外掺及二者复掺都能较好地优化AASP微结构,尤其是显著地改善了浆体的孔结构,从而改善AASP的宏观性能。可见,从微结构优化出发改善AASP宏观性能是可行的。
[Abstract]:Alkali activated slag cementitious material is a new kind of cementing material, which is composed of grinding water quenched blast furnace slag and alkaline activator. Compared with ordinary Portland cement, alkali-activated slag cementitious material has low hydration heat, rapid development of mechanical properties, good durability and so on, so it has become one of the cementitious materials instead of Portland cement. However, alkali-activated slag cementitious material has many problems, such as large drying shrinkage and fast carbonization speed, which hinders its popularization and application in engineering. These properties and defects are closely related to the microstructure of the matrix. Therefore, from the point of view of the optimization of microstructure, the modification effect of these materials on alkali-activated (AASP) of slag slurry is studied by selecting nano-materials, pozzolanic materials and their co-admixtures. The effects of alkali content and modulus on the working and mechanical properties of AASP were studied in this paper. The optimum mix ratio of AASP was determined. The optimum ratio of AASP was as follows: alkali content 4.0, modulus 1.2, water-binder ratio 0.4. Firstly, based on the optimum blending ratio, the effects of rutile nano-sized TiO2, anatase nanometer SiO2 on the mechanical properties, drying shrinkage and microstructure of AASP were studied. The results show that the mechanical properties of AASP, especially the flexural strength, can be enhanced by the addition of rutile nano TiO2. The shrinkage rate of nano SiO2 and anatase nano Ti02 was similar and higher than the reference value, while the dry shrinkage of AASP was decreased by the addition of rutile nano Ti02. Therefore, rutile nano TiO2, was selected to investigate the effect of rutile nano TiO2, on the microstructure of AASP. It is found that the incorporation of rutile nanosized T102 can promote the hydration reaction, make the AASP matrix denser at different ages and have no effect on the type of hydration products. The total porosity of AASP decreased to 69.5 in the reference group and the mesoporous content decreased to 59.6with the incorporation of rutile nanometer Ti02. Secondly, based on the optimum blending ratio, the effects of metakaolin, fly ash, silica fume and mineral powder mass on mechanical properties, drying shrinkage and microstructure of AASP were studied. The results show that the mechanical properties of AASP can be obviously improved and the drying shrinkage can be reduced by adding metakaolin to silica fume, fly ash and metakaolin. Therefore, the effect of metakaolin on the microstructure of AASP was studied. It is found that the addition of metakaolin can increase the content of silicate and aluminate gel, AFm and zeolite crystals, and make the matrix of AASP more compact at different ages. The total porosity of AASP decreased to 46.3% of the reference group, and the mesoporous content decreased to 43.1%. Thirdly, based on the results of macroscopical properties modification of AASP by nano-materials and pozzolanic materials, rutile nano-sized Ti02 and metakaolin were selected for blending, and their effects on the properties and microstructure of AASP were studied. The flexural strength and compressive strength of AASP were increased by 78.9% and 26.6% respectively. The addition of co-doped materials can increase the content of silicate gels and aluminosilicate gels, increase the content of zeolites, make the AASP matrix more dense at all ages, reduce the total porosity of AASP to 38.2% of the reference group, and decrease the mesoporous content to 35.5in the reference group. The effects of the two additives on the microstructure improvement and performance optimization are superior to those of rutile TiO2 and metakaolin. To sum up, rutile nano-sized Ti02, metakaolin can be used to optimize the microstructure of AASP, especially to improve the pore structure of the slurry, and thus to improve the macroscopic properties of AASP. Therefore, it is feasible to improve the macro performance of AASP from the point of view of microstructure optimization.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ177

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