【作者】 张彦娜；

【导师】 潘志华；

【作者基本信息】 南京工业大学 ， 材料学， 2004， 硕士

【摘要】 赤泥是氧化铝冶炼过程中排出的固体废渣,据统计我国每年排放赤泥300万吨以上,累积堆存量已高达4100万吨。目前赤泥的综合利用率很低尚不到15%,大量的赤泥被堆放于露天堆场,不仅占用土地资源,造成环境污染,也造成资源浪费。如何有效地利用赤泥,使之变废为宝成为一个社会问题,也成为众多科学研究者感兴趣的研究课题。另一方面传统硅酸盐水泥在生产过程中暴露出来的高能耗高资源消耗等弊端和水泥长期使用过程中表现出的性能劣变等问题,正受到当今社会可持续发展基本方针的严峻挑战。已经被列为国家重点基础研究发展规划的973项目“高性能水泥制备和应用的基础研究”正是出于上述战略考虑,将固体工业废渣作为高性能水泥性能调节型辅助胶凝组分的研究列为其中的重要研究课题之一。本论文围绕赤泥在高性能水泥中的利用这一主题,就赤泥的组成和性能特点、赤泥的活化方法、赤泥-高性能水泥熟料体系的胶凝性随赤泥与熟料的配合比和激发剂的变化规律,以及赤泥-熟料体系水化硬化过程和水泥硬化体的微观结构特征进行了全面系统的研究。TG-DTA、XRD、IR等现代测试方法对赤泥特征的分析表明,经露天长久放置的陈赤泥中结晶态物质主要为碳酸钙(以方解石为主,少量文石)和钙钛矿。电子显微镜观察表明,组成赤泥团聚体的一次粒子尺寸极其细小,外形极不规则。对赤泥颗粒的微区电子衍射分析则进一步表明,赤泥粒子中有相当部分为化学组成变动不定的无定形铝硅酸盐物质。在室温～900℃的加热处理过程中,赤泥中吸附水和结晶水的脱除于600℃之前基本完成,620℃～760℃发生碳酸钙的分解,加热处理温度达到700℃时(-C2S开始形成,800℃时大量形成,钙钛矿在整个加热处理过程中表现为惰性。采用化学活化和热活化的方法,在实验室条件下就不同化学试剂、不同温度下加热处理和不同掺量的赤泥-硅酸盐水泥熟料体系的胶凝性能试验表明,未经任何处理的赤泥掺入水泥中后,水泥砂浆后期强度显著降低,尤其是赤泥掺量大于20%时,而经特定化学试剂和一定煅烧温度处理的赤泥掺入水泥中,或添加少量化学物质,水泥砂浆后期强度的降低幅度得到明显减缓。 <WP=4>采用常规的化学分析方法对赤泥-熟料体系水化过程中液相钙离子溶出、结合水以及水化样品含Ca(OH)2随龄期的变化的跟踪测定结果表明:赤泥-熟料体系的水化硬化过程中赤泥中的组分与硅酸盐水泥水化后放出的氢氧化钙之间发生了火山灰反应;600℃加热处理对赤泥产生明显的活化作用。对水泥硬化体的SEM观察和MIP测定结果表明,少量赤泥的掺加使水泥硬化体的总孔隙率增大但是硬化体的大孔比例减小,小孔比例增加,说明赤泥微粒同时起着较好物理填充作用,这种作用是赤泥-熟料体系强度降低幅度得以有效控制的物理原因所在。但是,过多赤泥的掺加尽管具有同样的填充效果,由于物理填充比例过高,导致硬化体整体结构变弱,对强度发展不利。更多还原

【Abstract】 Red mud is a kind of solid by product raised from the alumina refining plant. It is reported that at least more than 3,000,000 ton red mud is discharged annually in China, and the accumulated amount of red mud discarded has reached 41,000,000 ton. Among those only little part was reutilized in some different ways, the rate of reutilization being said to be fewer than 15%, and large amount of red mud was exposured to atmosphere, which not only occupy land and caused pollution on environment but also resulted in the waste of natural resource. Therefore how to eliminate the problem of pollution and at the same time to transfer the waste residue into useful raw material consequently became a social focus meanwhile an interesting research subject for many investigators. On other hand, many disadvantages such as vast energy demanding and large natural resource consumption during the manufacture process of Portland cement and the deterioration of properties during its long term service attracted a severe challenge from the principal of persist development of modern society. As a result, the investigation of red mud to be used as a property modifying mineral admixture for high performance cement became one of the important subjects of a National Basic Research Priorities Programme, i.e. 973 programme, titled as “a basic research on the preparation and application of high performance cement”.Based on the fact described above and aimed at the goal of the utilization of red mud in high performance, the following research activities were carried out in this study, such as the analysis of chemical and physical properties of red mud, and the attempt of activation method of red mud, and tests of strength development on red mud – clinker systems with different mix proportions and different dosage of chemical additives, finally the analysis of hydration process of red mud – clinker systems and the microstructure of hardened cement pastes.Results of TG-DTA, XRD, and IR analysis showed that the main crystalline substances existed in aged red mud which was exposed in atmosphere for long time are calcium carbonate, mostly calcite and little aragonite, and perovskite. Electronic microscope observation and analysis showed that the red mud agglomerate was actually composed of very fine first particles which were in irregular outline and <WP=6>variable chemical composition, and most of them being amorphous alumino-silicates. Furthermore, it was proved that the absorbed water and crystalline water in red mud was found to be driven out before 600℃ during heating from ambient to 900℃, the decomposition of calcium carbonate took place between 620℃ and 760℃, the formation of (-C2S was detected to begin at 700℃ and continually to form thereafter, whereas perovskite remained unchanged during heating.Test results on the strength development of red mud – clinker systems with different proportion of red mud and clinker and different kinds of red mud thermally treated at different elevated temperatures and with different dosage of chemical additives showed an obvious drop in 28d compressive strength when raw red mud was used in replacement of cement, especially when the addition of red mud is more than 20%, however, the degree of the 28d compressive strength drop was effectively controlled when the thermally treated red mud was used or some chemical additives was introduced.Tracking of the hydration process of red mud – clinker systems by means of chemical analysis such as the dissolution of Ca2+ ions in liquid phase, the amount of combined water and Ca(OH)2 in hardened cement pastes along with curing age revealed that pozzolanic reaction occurs between the components of red mud and Ca(OH)2 released from the hydration of Portland cement clinker during the hydration process of red mud – clinker systems, especially the red mud was thermally treated at 600℃.SEM observation and MIP determination on hardened cement paste proved that parts of the large capillary pores in hardened cement paste of red mud – clinker systems were effect更多还原