【作者】 王桂明；

【导师】 余剑英；

【作者基本信息】 武汉理工大学 ， 材料学， 2005， 博士

【摘要】 混凝土耐久性是国际工程界的重要研究课题。大量研究表明:渗透性是影响水泥混凝土耐久性能的最关键因素,它与混凝土耐久性之间存在着极其密切的关系。因此,改善和增强水泥混凝土的抗渗性能,并使其具有优良的裂缝自修复能力是提高混凝土耐久性的重要途径,对于提高混凝土的耐久性具有重要的意义。本文在对裂缝自修复作用机理的分析研究基础上,制备了一种裂缝自修复材料,对该材料的自修复功能和作用机理进行了研究与表征,并系统地研究了该材料对混凝土耐久性的影响。主要研究结论如下: 1.在查阅与分析了大量国内外文献资料的基础上,提出了化学转换自修复反应思想,以此为理论依据,制备出了化学转换型水泥混凝土裂缝自修复材料—CCSM。 2.研究表明CCSM可显著提高水泥基材料(砂浆、混凝土)的抗渗性能和抗压强度。砂浆试件的一次抗渗压力由0.4MPa提高到1.4MPa以上,二次抗渗压力由O.1MPa提高到1.2MPa以上,抗压强度则由20.4lMPa提高到23.54MPa。 3.CCSM涂层试件的二次和多次抗渗性能的研究表明,CCSM可显著提高混凝土的抗渗自修复能力;对去涂层试件抗渗性能进一步研究证明CCSM主要是通过活性化学物质扩散渗透到混凝土内部,借助化学转换作用来提高混凝土的抗渗性,并赋予混凝土自修复功能。 4.XRD衍射、压汞试验、SEM显微分析和化学分析研究表明,CCSM内含的活性化学物质在水泥基材料中具有扩散渗透性,能在较短的时间内扩散到水泥基材料的内部,并通过化学转换反应促使试件内部的未水化水泥等活性胶凝物质与游离钙离子在孔隙和裂缝中生成不溶性的硅酸钙等结晶体,堵塞内部孔隙,封闭毛细孔通道,显著降低试件的孔隙率(由36.4%降低到14.8%),并使试件内部的有害孔(孔径为100～200nm)和多害孔(孔径大于200nm)明显减少,从而可阻止水与侵蚀性介质向内部的扩散。而CCSM的活性化合物在化学转换反应中并不消耗,可反复参与反应,从而可赋予水泥基材料持久的裂缝自修复功能。 5.对影响CCSM自修复作用的相关因素的研究表明,水泥基材料中应有一定量的水泥含量(10%以上),才能使CCSM化学转换反应充分进行,从而有效提高混凝土的裂缝自修复作用;延长养护时间、增大环境湿度均有利于CCSM化学转换作用的发挥。 6.研究发现CCSM可明显提高混凝土耐化学侵蚀和抗冻融破坏能力。CCSM处理试件在盐酸和氢氧化钠溶液中浸泡3个月后的抗压强度明显提高(增长率超过28%),在硫酸钾溶液中略为降低(小于10%),抗渗压力均由1.4MPa提高到1.5MPa更多还原

【Abstract】 The durability of concrete is an important research subject in the international engineering industry. A lot of researches indicated that the impermeability is the key factor to affect the durability of concrete. Therefore, the important path to improve the durability of concrete is to enhance the impermeability of concrete and make it gain the excellent self-healing function of cracks, which is of great significance to improve the durability of concrete. Based on analyzing the mechanism of self-healing function for cracks, a novel kind of self-healing materials for the cracks of concrete was prepared, and researched its self-healing ability and working mechanism, the influence of self-healing material on the durability of concrete was studied systematically also. The following conclusions and innovation can be obtained:1. Large numbers of literature and datum were consulted and analyzed in this paper, the mechanism of chemical change self-healing reaction was proposed for the first time. Based on this theory, a novel kind of chemical change type self-healing materials (CCSM) for cracks of concrete with good performance was prepared.2. CCSM could improve dramatically the impermeability and compressive strength of the cement-based materials (mortar or concrete). The first impermeability of mortar could be raised from 0.4MPa to higher than 1.4MPa as well as the secondary impermeability could be raised from 0.1 MPa to 1.2MPa. Moreover, the compressive strength was increased from 20.41 MPa to 23.54MPa either.3. The researches on secondary and multiple impermeability of coated specimens with CCSM showed that CCSM could improve dramatically the self-healing ability. Further studies on the impermeability of specimens which the coating have been removed indicated that the active compound of CCSM could penetrate fast into the inner of concrete, and cause a chemical change reaction to increase the impermeability of concrete and endow the concrete with a self-healing function.4. In this paper, the microstructure of concrete is studied by means of XRD, SEM and MIP, and the permeate depth of active compound was measured by chemical analysis also. All the results showed that the active chemical material has very strong ability of pervasion, it could penetrate into the inner of concrete in shorter time. The active compound of CCSM could cause a chemical change reaction between Ca(OH)2 and unhydrated cement, which generate a great quantity non-soluble dendritic crystalline. These dendritic crystalline blocks up the pores and cracks, decreased clearly the porosityof concrete from 36.4% to 14.8%, and reducing the number of the worst pores (the aperture was greater than 200nm) and worse pores (the aperture was between lOOnm and 200nm) in great extent. That is to say, CCSM made the inside structure of the cement concrete more compacted, inhibiting the pervasion of water and aggressive mediator. Moreover, the active chemicals of CCSM can be recovered after the reaction so that it can work forever, and endow cement-based materials with a self-healing function.5. In order to display thoroughly the chemical change function of active compound, the content of cement should be more than 10% of the cement-based materials. There are many factors which affected the chemical change function of CCSM, for example, the dosage of CCSM, the concentration gradient of active compound, pervasion time, the pore structure of concrete, the content of cement and the humidity of Surrounding environment etc.6. CCSM have concrete possess ability for chemical resistant and freeze-thaw resistant. The compressive strength of specimens treated by CCSM improved more than 28% immersed in dilute hydrochloric acid or sodium hydroxide solution for 3 months, and the compressive strength of specimens decreased about 10% immersed in potassium sulfate solution yet, the impermeability of all specimens increased from 1.4MPa to higher than 1.5MPa. However, the compressive strength of uncoated specimens decreased respectively 20 %, 18% and 27%, its impermeability debased from 0.6MPa to 0.4MPa either. Moreover, its loss of compressive strength after 150 freeze-thaw cycles was 3.5% that was much better than that of uncoated specimens whose loss was about 15.6%. The mechanism may be that the active chemical materials could blocks up the pores and cracks through the chemical change reaction, reducing the number of the capillary porosity (the distribution of aperture was between lOOnm and lOOOnm) in great extent, and decrease the porosity of concrete, inhibiting the pervasion of water and aggressive mediator. Therefore, it evidently debased the freeze-thaw injury caused by the water of capillary porosity, and improved effectively the ability of concrete for chemical resistant and freeze-thaw resistant.7. CCSM could effectively inhibited Alkali—Aggregate Reaction(AAR) of concrete. When the dosage of CCSM was 3% of the cement, its expansion ratio of length is only 1/9 of the uncoated specimens for AAR. The mechanism for inhibiting AAR may owe to the chemical change reaction of active chemical materials which obstructed the diffusion of water and alkali, weakening the superficial hydroxylation of aggregate, obstructing the diffusion of Na\ K+f P Ca2+ to the surface of aggregate that benefit the creation of steady solid structure and avoid the occurring of expansion by sopping water.8. The results of water absorption and chloride permeability of cement mortar indicated that CCSM could debase the water absorption of concrete from 5.91wt% of the uncoated specimens to 0.23~0.56wt%, the chloride diffusion coefficient was usually decreased to 20 % of the uncoated specimens. The steel corrosion test showed that the state of steel was in the passive state when the specimens were treated by CCSM. It is clearly that CCSM could prohibit water, chloride ion and any soluble chemical solution from penetrating the concrete to cause corrosion, leaking and other problems, therefore, CCSM was beneficial to the protection of corrosion of concrete.9. In this paper, according to the diffusion theory, the equation of diffusion of CCSM in concrete was established, adopting the method of finite element analysis for the first time to simulate and predict the pervasion of active chemical material in concrete, the data of pervasion depth and velocity of active compound for different time was gained. The results of predicted model of active compound match the actual value. It is proved by the contrast with the measured value and simulated value that the method of finite element analysis could be used effectively for the pervasion prediction of active compound and confirmed the strong pervasion ability of CCSM by theory that is favorable to the application of CCSM in construction work.更多还原