【作者】 王迎飞；

【导师】 马保国；

【作者基本信息】 武汉理工大学 ， 材料学， 2003， 硕士

【摘要】 本文以“十五”期间四大工程之一青藏铁路工程建设为课题背景，开展多因素破坏作用下负温早强混凝土材料的工程性质和理论研究。负温混凝土由于和普通混凝土在施工环境及服役环境上存在的差异，因此表现为比普通混凝土更为较高的耐久性要求；负温混凝土首先要避免早期的冻害以及具备长期抗冻性能，才能够满足工程实际应用的要求，这也是负温混凝土必须解决的两大技术关键；通过对目前常用防冻剂组分作用机理的分析研究及混凝土早期防冻机理探讨，采用矿物外加剂+防冻组分+高效减水剂+引气+阻锈组分功能复合的技术路线，通过正交试验设计复配了适应青藏铁路工程要求的专用多功能复合型外加剂FD-1；并在此基础上配制不同等级负温高性能混凝土，开展一系列包括硫酸盐侵蚀、氯离子渗透、抗冻融循环、收缩及耐磨性等耐久性能研究；通过对FD-1组分和掺量的调整，优化负温混凝土在施工特性、力学指标和耐久性三个方面的兼容、协调性。 通过对负温混凝土早期防冻分析研究认为，环境温度对混凝土的结构形成及其性能的影响十分突出，水泥水化温升和环境散热降温两个过程导致混凝土结构内部产生不均匀温度场，对过渡相、水泥砂浆以及骨料都能产生不同程度的温度损伤，产生内部温差应力裂纹，初始损伤也是不可避免的。影响混凝土冻害的主要因素是水、温度和孔结构。笔者半定量的描述负温混凝土早期抗冻临界结构的特征为抗压强度在3.3～4.0Mpa之间，并且自由水基本连续且尽可能地富集在易于迁移的毛细孔中。 采用FD-1型多功能复合型防冻剂，能够配制出-5℃环境下的C50以上负温高性能混凝土，产品性能稳定。在FD-1组分对负温混凝土的耐久性能研究中，认为影响自收缩的主要因素是水灰比和龄期；FD-1外加剂对水泥自收缩有很好的抑制作用，能够有效的提高水泥砂浆的耐磨性能。发现粉煤灰和硅灰的双掺技术能够显著改善混凝土的耐久性能，引气剂具备防冻抗冻、抗渗及提高负温混凝土工作性的优点，在负温混凝土中应该加大使用范围，但必须控制其掺量，确保强度损失较小。外掺石膏法、干湿交替法以及快速沸煮法三种实验方法对评价水泥砂浆的抗硫酸盐侵蚀性能有较好的一致性；高标号水泥品种对抗硫酸盐侵蚀性能有很好的改善作用。抗氯离子渗透性随着单方胶材掺量的增加摘要而增加。不同的水泥品种对氯离子的固化能力有所差别，胶材体系中C3A越低，抗渗性能较差。由N.S.Berke、M:C Hicks公式计算的氯离子扩散系数是冯乃谦公式的2.05~2.30倍之间。冯乃谦公式计算结果能够较为准确的反应负温高性能混凝土的渗透性能。 通过XRD、SEM、MIP、BET激光粒度分布仪等多种测试手段研究FD一1外加剂对负温高性能棍凝土耐久性增强机理。试验证明，矿物外加剂使水泥浆体孔径细化、水化产物相密实、界面过渡区改善、CH晶相总量减少;Ca困02)2促进和稳定了CH晶体生成，但改变了水泥石中水的迁移机制，包括迁移途径和速度。劣化了孔结构，相对削弱了自身的防冻能力，大大降低了混凝土的抗渗抗冻等耐久性能。在冬季施工中应该严格控制其掺量。 由于“高原”和“冻土”是青藏铁路修建面临的两大技术难题，作者简化了混凝土工程和冻土层边界条件，模拟了混凝土的水化放热温度变化过程及对周围冻土层结构热扰动的影响，提出了单层圆筒壁稳态导热模型，通过热工计算导出水泥品种、等级及其单方掺量和冻土层结构之间的热交换数学关系表达式，用热扰动半径和回冻时间两个技术参数来反应混凝土结构工程对冻土层结构的热效应程度，提出冻土区混凝土材料设计原则，对冻土层区施工的混凝土进行配合比优化设计;更多还原

【Abstract】 This paper unfolds engineering disposition and theoretical research of Negative Temperature High Performance Concrete (NTHPC) with the damage of many factors motivation, the project background based on Qing-Zang railway engineering, which is one of four-emphasized engineering during the tenth Five-plan. Due to the difference of environment of construction and service between NTHPC and ordinary concrete, and therefore durability of NTHPC is required to higher level. At a first, NTHPC must avoid frozen damage at early age and possess anti-freezing property at later period, in order to meet engineering practicable application need, and this are two emphasized and difficult problems, as for NTHPC; By means of mechanism analysis about deicing-agent ingredient and anti-freezing at early period, adopting composite technique routine of mineral addition+anti-freezing element+water-reducer4- air-entraining+anti-erosion of steel component etc, based on orthogonal experimental approach, FD-1 composite functional admixture was manufactured, which has more property and orientation on Qing-Zang railway. And different strength grade NTHPC has been manufactured based on the FD-1, Influence on the durability of NTHPC such as anti-sulfate corrosion, chloride penetration, freezing-thaw, shrinkage and antifriction etc is studied. The compatibility and harmony among workability, mechanical grade and durability are optimized, with the ground of adjusting composition and dosage of FD-1;After analyzing anti-freezing damage mechanism, it is concluded that temperature is main factor, which affects structure and property of concrete. After two processes of temperature-elevation of hydration heat and temperature-descent of cold-environment, there is original damage in concrete and its existence leads to temperature fields, as results in temperature damage on transition phase > aggregate and cement mortar of concrete. Main factors impact on frozen-damage of concrete are water, temperature and pore structure. The author hypothesizes anti-freezing threshold interface structure model, its token is that water nearby plump micro-pore possesses continuity of migration and mechanical strength range fluctuating 3.3~4.0Mpa, and they are two basic premise conditions to realize anti-freezing property of concrete at early age.Adopting FD-1 admixture, C50 concrete can be obtained, which has excellent adaptability for environment temperature ?5 C; Self-shrinkage of concrete is inevitable, and its variation tendency based on w/c and hydration age, FD-1 has wonderful inhibition for self-shrinkage, and meanwhile anti-friction property can be promoted. Two-addition technique of flying ash and silica fumecan meliorate durability of concrete; Air-entraining admixture possesses anti-freezing, descending ice point, and improving workability, and thereof it should be used in concrete. But controlling its dosage is very important to avoid strength loss. There is correspondence in evaluating sulfate resistance of cement paste by three test methods such as rapid boiling, gypsum mixing and wet-dry test. High strength grade cement can meliorate property of sulfate resistance. And chloride-resistance property is promoted by increasing dosage of cementttious materials; there is obvious difference on chloride-solidified performance of different cement variety. When CsA content is low, anti-chloride penetration property can be descent. According to the experience formula of Feng Naiqian and N.S.Berke, M.C.Hicks, diffusion coefficient is calculated respectively and compared. It is concluded that the latter is 2.05 ~ 2.30 multiple than the former, and Feng’s formula approaches the practical diffusion coefficient of NTHPC.By means of XREK SEM, MIP, BET modern testing apparatus and avenue, Reinforced durability of NTHPC mechanism by FD-1 is studied. It is proved that mineral admixture can prompt pore tiny, promote interface station and decrease CH phase. Ca(NO2)2 can activate hydration reaction at early age, but it harasses migration mechanism of water in mi更多还原