生态型偏高岭土超高性能水泥基复合材料的制备及机理分析

发布时间：2018-01-19 19:06

本文关键词： 偏高岭土超高性能水泥基复合材料力学性能微观性能　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：辅助性胶凝材料是高性能混凝土中必不可少的一部分,其中硅灰的使用较为广泛。然而,硅灰是冶金工业收集下来的一种工业副产物,其产量和质量都不太稳定,远远不能满足混凝土工程发展的需要,寻找新型优质矿物掺合料迫在眉睫。偏高岭土由高岭土人工煅烧生成,具有较高的火山灰活性和稳定的质量。在国外,从20世纪80年代人们已开始对偏高岭土在混凝土领域的应用研究。在我国,偏高岭土的作用近十年来开始逐渐被人们重视,研究将其作为矿物掺合料掺入混凝土中一度成为热点。虽然偏高岭土作为辅助性胶凝材料在水泥基复合材料中的应用得到了广泛的研究,但是在超高性能水泥基复合材料中的应用研究较为少见。本文针对目前偏高岭土在水泥基复合材料中的研究现状,系统研究了偏高岭土在3d、7d、28d、56d的火山灰活性指数,并且研究了在粉煤灰、硅灰、偏高岭土三元复掺条件下偏高岭土替代水泥或硅灰对水泥基复合材料的新拌性能、力学性能、微观结构、水泥水化的影响及其微结构形成机理分析。可以得到以下结论：火山灰活性测试结果表明,偏高岭土的火山灰活性比硅灰高,尤其在28d反应龄期,并且7d反应龄期前,偏高岭土和硅灰的火山灰活性指数分别为36.9和22.6,活性都比较低。新拌性能测试结果表明,由于偏高岭土颗粒形貌的不规则性,随着偏高岭土替代水泥的量的增大和偏高岭土替代硅灰的量的增大,浆体的流动度逐渐降低；掺加偏高岭土可有效抑制成型振捣中钢纤维的下沉,有利于钢纤维在砂浆中均匀分散,并且10%偏高岭土掺量钢纤维的分散最佳。力学性能测试表明,对于素砂浆,偏高岭土的掺入降低了材料的抗折强度,却可提高抗压强度：对于钢纤维增强砂浆,10%偏高岭土掺量下砂浆的抗折、抗压强度最大；弯曲韧性和断裂能试验表明,偏高岭土掺量为20%时弯曲韧性和断裂能最优,但综合考虑新拌浆体的工作性能,偏高岭土的最佳掺量为10%；在85%蒸汽养护条件下,试验所得抗压强度最高为210.4MPa,其配合比为0.17水胶比、10%掺量偏高岭土、10%掺量硅灰、20%掺量粉煤灰、3%体积率钢纤维、1.0砂胶比。微观性能分析测试结果表明,10%左右的孔隙率是材料具有超高性能的重要原因之一；偏高岭土的掺入提高了砂浆的孔隙率,细化了浆体的孔径；XRD Rietveld全谱拟合法分析了不同配比的水泥水化程度,结果表明水泥的最终水化程度在60%左右。偏高岭土可以提高水泥的水化程度,显著降低Ca(OH)2的含量；纳米压痕试验表明,随着偏高岭土掺量的增大,超高密度C-S-H凝胶含量增大。正是由于偏高岭土的加入使孔径得到细化、纤维分散更均匀、基体同钢纤维之间的粘结力的提高才使得复合材料具有更加优异的力学性能。
[Abstract]:Auxiliary cementitious material is an essential part of high performance concrete, in which silica fume is widely used. However, silica fume is a kind of industrial by-product collected from metallurgical industry. Its output and quality are not very stable, far from meeting the needs of the development of concrete engineering. It is urgent to find new high quality mineral admixture. Metakaolin is formed by artificial calcination of kaolin. It has high pozzolanic activity and stable quality. Since 1980s, people have begun to study the application of metakaolin in concrete field in China. The role of metakaolin has been paid more and more attention in recent ten years. Although the application of metakaolin as auxiliary cementitious material in cement matrix composites has been widely studied. However, the research on the application of metakaolin in cement matrix composites is rare. According to the current research status of metakaolin in cement matrix composites, the metakaolin is studied in 3 days and 7 days to 28 days. The pozzolanic activity index of 56d, and the new mixing properties and mechanical properties of cement or silica fume substituted for cement or silica fume by metakaolin in the condition of fly ash, silica fume and metakaolin ternary admixture were studied. The results show that the pozzolanic activity of metakaolin is higher than that of silica fume. The pozzolanic activity index of metakaolin and silica fume were 36.9 and 22.6 respectively before the 28 d reaction age and 7 d reaction age. The fresh mixing performance test results showed that the pozzolanic activity index of metakaolin and silica fume was lower than that of silica fume. Due to the irregular morphology of metakaolin particles, the fluidity of the slurry decreases gradually with the increase of the amount of metakaolin instead of cement and the amount of metakaolin replacing silica fume. The addition of metakaolin can effectively inhibit the sinking of steel fiber in forming vibration, which is beneficial to the uniform dispersion of steel fiber in mortar, and the dispersion of steel fiber with 10% metakaolin content is the best. The mechanical properties test shows that. For plain mortar, the addition of metakaolin reduces the flexural strength of the material, but it can improve the compressive strength. The compressive strength of the mortar with 10% metakaolin content of steel fiber reinforced mortar is the highest; The bending toughness and fracture energy tests show that the flexural toughness and fracture energy are optimal when the content of metakaolin is 20, but the optimum addition of metakaolin is 10 when considering the working performance of fresh slurry. Under the condition of 85% steam curing, the maximum compressive strength is 210.4MPa, and the mixture ratio is 0.17 water / binder ratio 10% of metakaolin and 10% silica fume. The ratio of 20%% fly ash to 3% volume ratio of steel fiber is 1.0 sand / binder. The results of microcosmic property analysis show that the porosity of about 10% is one of the important reasons for the super high performance of the material. The addition of metakaolin increases the porosity of mortar and refines the pore size of mortar. The hydration degree of cement with different ratio was analyzed by XRD Rietveld full spectrum fitting method. The result shows that the final hydration degree of cement is about 60%, and metakaolin can improve the hydration degree of cement. The content of Ca(OH)2 was decreased significantly. The nano-indentation test showed that the content of ultrahigh density C-S-H gel increased with the increase of the content of metakaolin. It was precisely because of the addition of metakaolin that the pore size was refined and the fiber dispersed more evenly. The increase of adhesion between matrix and steel fiber makes the composite have better mechanical properties.
【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】：TU599

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