【作者】 李娟；

【导师】 马保国；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2013， 博士

【摘要】 水泥熟料生产的CO2排放约有65%来自石灰石的碳酸盐分解,仅有35%来自燃料的燃烧排放,基于材料本征的排放特点,通过优化工艺提高能效、辅助胶凝材料使用等措施减排的潜力日益减小,而从水泥基材料组成本身进行创新成为全球研究的焦点。本文通过对熟料矿物的形成温度、形成焓、单位矿物CO2排放量等多重因素进行低钙低碳优化设计,实现了不含高钙矿物-阿利特(C3S)、以贝利特(C2S)和硫铝酸盐(C4A3S)为主导矿物的低能耗、低CO2排放C2S-C4A3S-C4AF三元熟料体系(Belite Calcium Sulfo-Aluminate, BCSA)。通过矿物组成优化匹配及晶体的稳定与活化,制备出性能优于但能耗和排放远低于普通硅酸盐水泥的BCSA水泥。与普通硅酸盐水泥相比,BCSA水泥生产过程中可节约石灰石28%和标煤约16%以上,减少CO2排放20%以上,实现了通过水泥基材料创新达到节能降耗的目的。本文利用XRD、红外光谱IR和SEM等方法,围绕BCSA的矿物组成设计、离子掺杂作用机理、工业试生产及其水泥混凝土性能,主要研究了以下内容：(1)熟料低钙组成设计和高温矿相形成研究确定了熟料低钙低碳矿物组成的原则。由C2S-C4A3S-C4AF三元矿物组成的熟料体系里,CaA3S和C2S分别是熟料的早期强度和中后期强度的来源。研究了C2S、C4A3S和C4AF三种矿物的形成温度和最佳范围,阐明了三种矿物的共存温度区间1250-1350℃。研究了熟料的易烧性、主要熟料矿物C4A3S和C2S的形成和结晶发育状况、以及熟料的物理性能。研究表明,BCSA熟料的最佳烧成温度范围是1280-1320℃,在该温度范围内烧制的熟料具有良好的工作性和物理力学性能。(2) BCSA熟料矿物优化匹配和熟料／石膏作用机理确定了BCSA熟料矿物组成范围为C2S36-56%, C4A3S32-42%和C4AF5-9%。在上述矿物组成范围内,BCSA熟料具有最佳的物理性能,3天和28天抗压强度分别达到34.3MPa和55.1MPa。研究了BCSA熟料与石膏的相互作用机理。石膏掺量显著影响BCSA水泥的性能,确定了石膏最佳掺量范围为12.5-15%。石膏主要是与C4A3S发生反应形成钙矾石。在浆体结构中,钙矾石与其他水化产物一起形成密实的空间网架结构。(3)离子掺杂对熟料矿物晶体的稳定与活化机理研究p晶型C2S水化速率慢,早期强度低,一直影响着这种矿物在熟料中的作用。本文着重研究了提高β-C2S活性的方法和作用机理。研究表明,外掺离子Ba2+、P5+和Zn2+等离子均可进入p-C2S晶格,引起晶格畸变,并且在矿物表面发生富集,使得矿物晶体细化,增强了p-C2S的水化反应活性。同时发现在多种矿物共存的熟料体系中,部分外掺离子进入CSA矿物晶格中,引起晶格畸变,提高了CSA水硬性。β-C2S和C4A3S两种矿物共存时,外掺离子影响其活性的显著性依次为：Ba2+>P5+>Zn2+>B3+。掺入Ba2+的熟料制得的水泥,其28d抗压强度达到69.7MPa,比未掺杂空白样强度提高了15MPa(26.5%)。(4) BCSA水泥工业试生产关键技术的研究利用现有水泥工艺设备和工业原燃料,全球首次在带五级预热器窑的新型干法生产线上进行了BCSA水泥工业化试生产的关键技术研究,实现了该水泥在新型干法生产线的工业化试生产。确定了工业化制备的主要工艺参数,所生产水泥的3d强度达43.7MPa,28d强度达66.9MPa。(5) BCSA水泥混凝土力学性能及耐久性研究结果表明,BCSA水泥配制混凝土具有良好的力学性能(抗折抗压强度、劈拉强度、轴心抗压强度等)和耐久性能(包括抗渗性、抗冻性、氯离子渗透性、抗硫酸盐侵蚀性、抗碳化性能、体积稳定性等)。这些性能均优于普通水泥配制的混凝土性能。分析表明,BCSA水泥需水量少,浆体内部孔隙率较低,且水化产物中钙矾石形成过程伴随的微膨胀增加硬化浆体结构的致密度。这是BCSA水泥混凝土具有良好的力学性能和耐久性能的主要原因。更多还原

【Abstract】 During the process of clinker production, roughly65%of the CO2emission is from the decomposition of limestone, and only around35%is from the combustion of fuels. Some levers were used to reduce the CO2emission, including increasing energy efficiency by optimizing processes, and increasing cementitious additions into the cement, etc. In terms of the fact that most of the emission is from limestone, there is less potential for conventional levers to mitigate CO2. Research on new cementitious binder has become a global focus.According to low calcium and low carbon design on clinker minerals composition, a type of C2S-C4A3S-C4AF clinker system (BCSA) with low energy consumption and low emission is developed. High energy consumption and high emission mineral C3S is replaced by low energy consumption and low emission minerals, belite (C2S) and sulphoaluminate (C4A3S). Through optimizing and activating the clinker minerals, the cement made of BCSA clinker can attain better properties with much less emission than OPC. Compared with OPC, BCSA cement consumes28%less limestone and16%less coal, and generates20%less CO2.Many aspects of the BCSA clinker are studied through the tests of XRD, Infrared, SEM, etc. in this paper. The following main parts are researched in this paper:(1) Low calcium design of clinker and clinkering of BCSAThe new clinker system is based on low calcium and low carbon minerals principle. C4A3S and C2S are providing the early strength and later strength of the clinker respectively in the C2S-C4A3S-C4AF clinker system.The clinkering temperature ranges of the minerals are studied. Considering the formation of well crystallized β-C2S and C4A3S, as well as the nucleation quantity of crystals, the optimum temperature range is1280～1320℃to ensure better properties.(2) Optimization of clinker mineral composition and clinker-gypsum reaction mechanismIt is defined that the ideal range for mineral composition of BCSA clinker is C2S36-56%, C4A3S32-42%and C4AF5-9%. The clinker can reach34.3MPa and55.1MPa respectively at3days and28days.The reaction mechanism between BCSA clinker and gypsum is studied. It is showed that the best range for gypsum content is12.5-15%. Gypsum reacts with C4A3S to form ettringite, and then the ettringite forms a compacted network with other hydrates.(3) Activating technologies for BCSA clinker minerals through ion dopingLow hydration rate of β-C2S and low early strength has been bottleneck of the effect of C2S in the clinker. The measures to increase the reactivity of P-C2S and its mechanism are studied. It is shown that foreign ions of Ba2+, P5+and Zn2+have effects on stabilization of β-C2S and activation of both β-C2S and C4A3S. Distortion defects of the lattice are occurred by the foreign ions via entering into the lattice of the β-C2S crystal structure, thus to prevent the transformation from β-C2S to γ-C2S, and accelerate the nucleation of P-C2S. In addition, the foreign ions can easily concentrate on crystal boundary and prevent the growth of crystal grains, eventually enhance the reactivity of P-C2S. Further study shows that the foreign ions enter into the lattice of C4A3S and cause distortion, as a result, the reactivity of C4A3S is enhanced as well. The sequence of combined effects of different ions on the reactivity of β-C2S and C4A3S:Ba2+>P5+>Zn2+>B3+.The compressive strength of cement from Ba2+doped clinker can reach69.7MPa at28d, nearly15MPa higher than reference one.(4) Key technology for trial production of BCSA cement on a line with NSP processBCSA cement is produced using existing NSP process and equipment, conventional raw materials and fuel. It was the first time in the world to produce BCSA cement on a real line. Main parameters for production are researched during the trial production. The compressive strength of BCSA cement produced can reach43.7MPa at3d and66.9MPa at28d.(5) Mechanical properties and durability of BCSA concreteIt is showed that BCSA-30concrete has good mechanical properties. And BCSA-30concrete has higher durability than OPC concrete in terms of frost resistance, sulphate resistance, drying shrinkage, etc. That is mainly due to the lower water demand, lower porosity, micro-expansion of ettringite and much denser hydration products.更多还原