偏高岭土改性海工混凝土的若干问题研究

发布时间：2018-04-27 13:38

本文选题：偏高岭土改性混凝土 + 水化过程　；参考：《武汉理工大学》2014年博士论文

【摘要】：混凝土材料与结构都处于特定的环境中，诸如城市环境、海洋环境、寒冷环境、盐碱侵蚀环境等，，随着混凝土应用的日益广泛，混凝土耐久性的问题受到越来越多专家学者和行业人员的关注。近年来，随着海洋开发的不断深入，海洋混凝土用量大增，其耐久性问题受到更高的重视。海工混凝土结构长期浸泡在海水环境中，结构受到海水中有害物质的侵蚀，混凝土结构极易劣化，表面产生裂缝、体积膨胀、剥落、破洞等损坏现象，现有研究表明将偏高岭土作为掺合料加入混凝土能够提高其力学性能和耐久性，加之远海施工中原材料拌和水与细骨料的取材存在运输困难，因此深入研究海水环境下混凝土结构与性能的关系对于海洋工程意义重大。本文以低掺量偏高岭土体系为基础，与不同原材料相配合，分别组成不同的海工混凝土体系，这些体系包括普通粗骨料-河砂-淡水-偏高岭土改性体系、普通粗骨料-河砂-人工海水-偏高岭土改性体系、普通粗骨料-海砂-淡水-偏高岭土改性体系，研究上述三类体系分别在标准条件、氯化钠溶液、硫酸钠溶液、硫酸镁溶液养护下水泥基材料体系的显微结构特征、强度发展规律、耐久性能与改善机理，以期将研究结果应用于海洋工程。论文进行的主要工作和取得的主要成果如下： (1)三大体系在标准养护下的力学性能测试表明，对于各体系，当偏高岭土掺量为5wt%时，偏高岭土对净浆、砂浆、混凝土强度活性指数最高。 (2)淡水-偏高岭土和人工海水-偏高岭土水泥体系的水化量热分析表明，淡水体系偏高岭土的加入使得72小时总放热量降低，人工海水的加入使得水化放热总量有不同程度的提高。两种体系水化放热速率在偏高岭土掺量为3wt%时高于基准样，而偏高岭土掺量为5wt%和6wt%时低于基准试样。 (3)水化产物的矿物组成研究发现，淡水拌合的情况下的水化产物为C-S-H凝胶、氢氧化钙(CH)、钙矾石(ettringite)、单硫型硫铝酸钙及类水滑石(hydrotalcite，HT，Mg4Al2(OH)12CO3(H2O)3)。人工海水拌合的情况下的水化产物种类与淡水拌合情况下类似，类水滑石生成量降低，并增加生成新的矿物水铝钙石(hydrocalumite，HC，Ca8Al4(OH)24(CO3)Cl2(H2O)1.6(H2O)8)。 (4)水化产物氢氧化钙含量的分析表明，未掺入偏高岭土的净浆基准试样中氢氧化钙的含量随着龄期增长而增加，而掺入偏高岭土的净浆，氢氧化钙的含量从3天到7天增加，而从7天到28天龄期的含量下降，这说明在后期偏高岭土与氢氧化钙产生火山灰反应。相同偏高岭土掺量下，海水拌合体系的氢氧化钙含量始终高于同掺量同龄期的淡水拌合体系，这说明人工海水拌合对水化有促进作用。 (5)对抗氯离子侵蚀性能的研究结果表明，各系列中，掺入5wt%偏高岭土能够有效提高混凝土的抗压强度和抗氯离子渗透性能，其原因是浆体致密度的提高以及固化侵蚀溶液中的氯离子生成Friedel盐。海水拌和体系中偏高岭土的加入同样使体系表现出一致的抗氯离子侵蚀性能。对于所有系列，氯离子侵蚀后的水化产物为碳酸钙、氢氧化钙及Friedel盐。原有的水化产物中的钙矾石及类水滑石或水铝钙石均转变为碳酸钙和Friedel’s salt，起到固化氯离子的作用。 (6)对抗硫酸盐侵蚀性能的研究表明，各体系中5wt%偏高岭土体系在硫酸钠和硫酸镁溶液侵蚀后的抗压强度较其他体系更佳。含5wt%偏高岭土的人工海水拌和体系经硫酸盐侵蚀后强度与任一试样相比均为最高，这说明使用人工海水拌合并掺入5wt%偏高岭土能够增强混凝土的抗硫酸盐侵蚀性能。硫酸根离子侵蚀深度的结果表明，偏高岭土的加入使体系尤其是混凝土有更好的抗硫酸盐侵蚀性能，表现出良好的抗渗性。
[Abstract]:Concrete materials and structures are in a specific environment, such as urban environment, marine environment, cold environment, saline alkali erosion environment, and so on. With the increasing application of concrete, the problem of concrete durability has been paid more and more attention by experts and scholars and industry personnel. In recent years, with the continuous development of marine development, marine concrete The durability problem of the sea workers has been paid more attention to. The structure of the marine concrete is soaked in the seawater environment for a long time, the structure is eroded by the harmful substances in the sea water, the concrete structure is very easy to deteriorate, the surface produces cracks, the volume expansion, the exfoliation, the broken hole and so on. The existing research shows that the high ridge soil is used as the admixture to add the coagulation. Soil can improve its mechanical properties and durability. In addition, there is a transport difficulty in the material of raw materials mixed with water and fine aggregate in the offshore construction. Therefore, it is of great significance to study the relationship between the structure and properties of concrete under seawater environment for marine engineering.
Based on the low content of the metakaolin system, different raw materials are combined to form different marine concrete systems. These systems include ordinary coarse aggregate - river sand - freshwater - metakaolin system, ordinary coarse aggregate - river sand - artificial sea water - high ridge soil modified body system, ordinary coarse aggregate - sea sand fresh water and high ridge soil modification In this system, the microstructure characteristics, strength development law, durability and improvement mechanism of the above three kinds of systems under the standard conditions, Sodium Chloride Solution, sodium sulfate solution and Magnesium Sulfate solution are studied in order to apply the results to marine engineering.
The main work and main achievements of the paper are as follows:
(1) the mechanical properties test of the three major systems under the standard maintenance showed that, when the content of kaolin was 5wt%, the strength activity index of the ridge to the pulp, mortar and concrete was the highest.
(2) the hydration heat analysis of the fresh water - metakaolin and the artificial sea water - metakaolin cement system shows that the addition of the metakaolin in the freshwater system makes the total amount of heat reduced in 72 hours. The addition of artificial sea water makes the total amount of hydrated exothermic increase in varying degrees. The hydration heat rate of the two systems is higher than that of the base of 3wt%. The content of meta kaolin is lower than that of reference sample when 5wt% and 6wt% are added.
(3) a study of the mineral composition of the hydration products found that the hydration products of fresh water are C-S-H gel, calcium hydroxide (CH), ettringite (ettringite), single sulphur type calcium aluminate and hydrotalcite like (hydrotalcite, HT, Mg4Al2 (OH) 12CO3 (H2O) 3). The types of hydration products under artificial seawater are similar to those of fresh water. The amount of hydrotalcite decreased and the formation of new mineral alcalite (hydrocalumite, HC, Ca8Al4 (OH) 24 (CO3) Cl2 (H2O) 1.6 (H2O) 8) increased.
(4) the analysis of the content of calcium hydroxide in the hydration products showed that the content of calcium hydroxide increased with the age increase, and the content of calcium hydroxide was increased from 3 days to 7 days, while the content of calcium hydroxide was increased from 7 days to 28 days, which indicated that in the later period the metakaolin and hydrogen oxidation were oxidized. Calcium produced the reaction of volcanic ash. Under the same amount of kaolin, the content of calcium hydroxide in the seawater mixing system is always higher than the fresh water mixing system with the same age at the same age, which indicates that the artificial seawater mixing can promote the hydration.
(5) the results of the study on the corrosion resistance of chlorine ion show that the addition of 5wt% to high ridge soil can effectively improve the compressive strength and the permeability resistance of the chloride ion, which is due to the increase of the density of the slurry and the formation of the chloride ion in the solidified solution of the Friedel salt. For all series, the hydrated products after chlorine ion erosion are calcium carbonate, calcium hydroxide and Friedel salt. The ettringite and hydrotalcite or alalite in the original hydration products all change into calcium carbonate and Friedel 's salt, which play the role of curing chlorine ions.
(6) the study of resistance to sulfate erosion shows that the compressive strength of the 5wt% metakaolin system after erosion of sodium sulfate and Magnesium Sulfate solution is better than that of the other systems. The strength of the artificial seawater mixing system containing 5wt% metakaolin is the highest after sulfate attack, which indicates the combination of artificial seawater mixing. The addition of 5wt% to the high ridge soil can enhance the corrosion resistance of the concrete. The result of the depth of sulfate ion erosion shows that the addition of the metakaolin makes the system especially the concrete have better resistance to sulphate erosion, and shows good impermeability.

【学位授予单位】：武汉理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV431

【参考文献】