石灰—偏高岭土胶凝材料的制备及其天然矿物纤维改性研究

发布时间：2018-06-03 21:59

本文选题：石灰-偏高岭土 + 天然矿物纤维　；参考：《长安大学》2017年博士论文

【摘要】：古建筑遗址是人类历史文化遗产的重要组成部分,见证了人类文化的发展和科技的进步。目前,中国保有大量如城墙、墓葬、石雕造像及岩画壁画等砖石及岩土质古建筑遗址,而此类遗址保护工作的关键就在于修护所采用的胶凝材料是否得当,因此,古建筑修护胶凝材料的研发一直是相关领域学者的研究重点。石灰-偏高岭土(Lime-metakaolin,L-MK)胶凝材料是由熟石灰与偏高岭土混合而成的胶凝材料,由于其机械强度适中、透水透气性良好、不含可溶性盐类等特性,可与古建筑基体进行良好兼容,因而成为近几年古建筑修复材料领域的研究热点。本文以氢氧化钙和偏高岭土为原料,制备了L-MK净浆及砂浆,并以性能增强及生产安全性为出发点,选用坡缕石、硅灰石、水镁石及海泡石四类非石棉天然矿物纤维对其进行改性。采用现代测试手段对浆体的固化反应机理、物相成分和微观结构变化以及纤维改性机理等方面进行了分析研究,本文主要研究内容和成果如下:(1)在偏高岭土掺量0%~50%范围内,其掺量的增加有助于净浆中水化反应的进行,使材料整体性能提高。其中,当掺量40%~50%时,C4AH13为反应初期的主要结晶态水化产物,而后C4AH13逐渐向C2ASH8转化,28天时C2ASH8成为主要产物,养护28天可可基本将原料Ca(OH)2反应完全;掺量10%~20%时,C4AH13为整个过程中的主要结晶态水化产物,养护28天时样品中仍存有大量未反应的Ca(OH)2;掺量30%时,经过28天养护,产物中C4AH13和C2ASH8并存,也存在一定量未反应的Ca(OH)2;整个养护过程中C4A?H11仅作为中间产物短时间存在于反应初期,对材料结构和性质影响不大;此外,水化产物C-S-H中存在普遍的Al类质同象替代Si的现象。(2)与净浆相比,标准砂的加入会延缓砂浆的水化反应进程,有利于碳化反应的进行;偏高岭土掺量的升高有助于砂浆机械强度、抗干燥收缩性、质量稳定性、水稳定性及抗硫酸盐腐蚀性的提高;较高的养护湿度条件有利于L-MK砂浆总体性能的提升,表明L-MK砂浆适用于潮湿环境中,但高湿度条件下养护后的L-MK固化砂浆对硫酸盐侵蚀的敏感性更高;胶砂比和水胶比的改变,会对新拌砂浆的工作性能及固化砂浆的物理、力学性能产生不同程度的影响。(3)在坡缕石及硅灰石纤维粉改性L-MK砂浆中,纤维粉尺寸越细小,改性作用效果越明显,但两种纤维对砂浆的作用机理不同:坡缕石纤维会促使水化产物沿纤维表面生长成放射状的脉络结构,而硅灰石则会参与体系内部水化反应;两种纤维粉均会在一定程度改善砂浆的柔韧性,有利于提高砂浆的抗裂性能;坡缕石纤维的添加会使新拌砂浆流动度明显减小,收缩值和吸水性变大,而力学性质有不同程度的下降;硅灰石纤维会增加砂浆流动度,收缩值和吸水性变小,有利于抗折强度的提升,对抗压强度影响不大,经分析,坡缕石纤维最佳掺量为2%~4%,硅灰石为4%;(4)在水镁石及海泡石纤维改性L-MK砂浆中,经过松解处理,可以使纤维束发生显著松解,杂质含量减少,相比于干法添加,湿法添加更有利于纤维在砂浆中的均匀分散;两种纤维的添加均会减小新拌砂浆的流动度,增加固化砂浆的收缩性及吸水性,其中海泡石纤维影响效果更为明显;此外,水镁石和海泡石纤维的添加会在砂浆内部形成三维网状结构,能有效承担并消耗断裂能,使砂浆力学性能获得一定提升;水镁石和海泡石纤维分别在掺量2%和6%时效果最好。(5)基于纤维增强复合材料中纤维和裂纹的几何关系模型,探究了水镁石和海泡石纤维改性L-MK材料中乱向分布的微裂纹和纤维之间的量化关系。在假定微裂纹尺寸一定的条件下,裂纹与纤维的接触概率与纤维掺量成正比,与纤维长径比成反比。水镁石纤维相比海泡石纤维具有更低的相对密度和长径比值,有利于在较少的纤维体积掺量条件下增加微裂纹与纤维的接触概率,从而可在较少的纤维掺量条件下发挥其纤维增强赠韧的作用效果。
[Abstract]:The ancient architectural site is an important part of human historical and cultural heritage. It has witnessed the development of human culture and the progress of science and technology. At present, China maintains a large number of bricks and rocks, such as walls, tombs, stone sculptures and rock paintings, and other rock and earth ancient building sites, and the key to this kind of site protection is the cementitious material used in the repair. Therefore, the research and development of gelling materials for ancient building repair has always been the focus of research in the related fields. Lime-metakaolin (L-MK) cementitious material is a cementitious material composed of lime and metakaolin. Because of its moderate mechanical strength, good permeability and permeability, and no soluble salts, it can be used in ancient times. In this paper, L-MK pulp and mortar are prepared by using calcium hydroxide and metakaolin as raw materials, and four kinds of non asbestos natural mineral fibers, palygorskite, wollastonite, brucite and sepiolite, are selected as the starting point for the preparation of calcium hydroxide and metakaolin as raw materials. The curing reaction mechanism, phase composition and microstructure change and fiber modification mechanism of the slurry are analyzed with modern testing methods. The main contents and results of this paper are as follows: (1) in the range of 0%~50%, the increase of the content of the mixture is helpful to the hydration reaction in the pulp. When the amount of 40%~50% is added, C4AH13 is the main crystalline hydration product at the initial stage of the reaction, and then C4AH13 is gradually converted to C2ASH8, and C2ASH8 becomes the main product at 28 days, and 28 days of cocoa basically reacts the raw material Ca (OH) 2, and C4AH13 is the main crystalline hydration product in the whole process when the amount of 10%~ 20% is added. There are still a lot of unreacted Ca (OH) 2 in the curing 28 days, and 30%, after 28 days of curing, C4AH13 and C2ASH8 coexist in the product, and there is a certain amount of unreacted Ca (OH) 2. During the whole curing process, C4A H11 only exists as a intermediate product in the initial period of the reaction, and has little effect on the structure and properties of the material; in addition, the hydration product C-S-H There is a common phenomenon of Al like homogeneous image instead of Si. (2) compared with the net pulp, the addition of standard sand will delay the hydration process of the mortar and be beneficial to the carbonization. The increase of the content of the high ridge soil is helpful to the mechanical strength of the mortar, the anti drying shrinkage, the quality stability, the water stability and the sulfate corrosion resistance; The curing moisture condition is beneficial to the improvement of the overall performance of L-MK mortar, indicating that the L-MK mortar is suitable for the wet environment, but the sensitivity of the L-MK solidified mortar after the maintenance of high humidity is higher, and the change of the mortar ratio and the water glue ratio will not produce the physical and mechanical properties of the new mortar. (3) in the modified L-MK mortar of palygorskite and wollastonite fiber powder, the smaller the size of the fiber powder, the more obvious the modification effect is, but the mechanism of the action of the two fibers is different: palygorskite fibers will cause the hydration products to grow into a radial choroid structure along the surface of the fiber, and the wollastonite will be involved in the internal water of the system. The two kinds of fiber powder will improve the flexibility of the mortar to a certain extent and improve the cracking resistance of the mortar. The addition of palygorskite fibers will reduce the flow degree of the new mortar, the shrinkage and water absorption, and the mechanical properties of the mortar to a different degree, and the silt fiber will increase the mobility, shrinkage and water absorption of the mortar. It is beneficial to improve the flexural strength, which has little effect on the compressive strength. After analysis, the best dosage of palygorskite fiber is 2%~4%, and the wollastonite is 4%. (4) in the brucite and sepiolite fiber modified L-MK mortar, the loosening of the fiber bundle and the decrease of the impurity content can be made by the loosening of the brucite and the sepiolite fiber modified mortar. The addition of the two fibers will reduce the flow degree of the fresh mortar, increase the shrinkage and water absorption of the solidified mortar, and the effect of the sepiolite fiber is more obvious. In addition, the addition of brucite and sepiolite fiber will form a three-dimensional network structure in the inner part of the mortar, which can be effectively borne and consumed. The fracture energy can improve the mechanical properties of the mortar, and the best effect of the brucite and sepiolite fiber is 2% and 6% respectively. (5) based on the geometric model of fiber and crack in the fiber reinforced composites, the quantitative relationship between the microcracks and the fibers in the disorderly distribution of the brucite and sepiolite fiber modified L-MK materials is explored. Under the assumption that the size of the micro crack is certain, the contact probability of the crack to the fiber is proportional to the fiber content, and is inversely proportional to the fiber length diameter ratio. The brucite fiber has a lower relative density and the ratio of the length to the length, which is beneficial to the increase of the contact probability of the micro crack and the fiber under the less volume of the fiber. It can give full play to the effect of fiber reinforcing and toughening under the condition of less fiber content.
【学位授予单位】：长安大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ177;TU578.1

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