【作者】 汪秀石；

【导师】 王建国；

【作者基本信息】 合肥工业大学 ， 工程力学， 2012， 博士

【摘要】 随着资源能源问题的日益突出,采用现代工业废弃物取代天然不可再生资源进行水泥基材料生产需要进行深入研究,以消除或减轻对环境的严重影响将成为水泥基新材料研究的一个重点领域。本文以安徽霍邱特大型铁矿的尾矿砂作为自密实水泥基材料部分细骨料为研究背景,通过试验,系统地研究了水泥基净浆、水泥基砂浆以及自密实混凝土性能。探索铁尾矿砂自密实水泥基材料存在的内部特征以及提高其性能的科学研究方法,对于铁尾矿砂自密实水泥基材料的研究与应用具有重大的现实意义。本文通过对铁尾矿砂自密实水泥基材料的研究得出以下结论：1、通过宏观性能指标并结合微观技术手段,本文对于配制铁尾矿砂自密实水泥基材料的原材料进行了深入分析,给出了各组成成分的宏观技术指标,采用能谱分析(EDS)对于原材料进行了定性、半定量的元素组成分析,并采用X射线衍射分析(XRD)手段对各原材料进行了组成物相分析,为铁尾矿砂自密实水泥基材料性能研究提供基础。2、研究了铁尾矿砂水泥基砂浆和铁尾矿砂自密实混凝土的流变性能宏观表现特征(工作性能)。以一组普通水泥基砂浆为研究基准,铁尾矿砂取代率、水胶比为变量,研究铁尾矿砂水泥基砂浆的工作性能,结果显示,铁尾矿砂取代率为40%的铁尾矿砂水泥基砂浆(简称IM-2)与普通水泥基砂浆(简称M-I)的工作性能指标值相近,具有较好的性能；以铁尾矿砂取代率作为配合比设计变量,并对比普通型自密实混凝土,铁尾矿砂自密实混凝土的工作性能评价采用动态稳定试验和静态稳定试验,综合评价铁尾矿砂自密实混凝土的工作性能,试验结果显示,铁尾矿砂掺量为40%的自密实混凝土(简称ISCC-2)与普通自密实混凝土(简称SCC-1)具有良好的工作性能。3、首次系统地进行了铁尾矿砂水泥基砂浆和铁尾矿砂自密实混凝土的流变性试验研究。推导了Bingham流体模型和Herschel-Bulkley流体模型的库尔特逆问题积分和完整的求解流变本构模型过程。试验结果表明,水泥基砂浆拌合物流变曲线符合非线性特征,符合Herschel-Bulkley流体模型,在相同时间点时,在剪切速率相同的条件下,IM-2的剪切应力更小：自密实混凝土拌合物的流变曲线符合线性特征,符合Bingham流体模型,在相同时间点时,在剪切速率相同的条件下,ISCC-2的剪切应力稍大。4、系统地进行了铁尾矿砂水泥基材料基本力学性能试验,试验结果表明,掺入特细天然砂的净浆和掺入铁尾矿砂的净浆在抗压强度随龄期变化的强度,前者高于后者,而抗折强度则相反,后者高于前者：水泥基砂浆抗压强度早期强度发展较快,其中M-1、IM-2的1d强度超过了20MPa；普通型自密实混凝土与铁尾矿砂自密实混凝土抗压强度随龄期变化增长趋势亦相似,早期强度发展可分为三个阶段：快速发展期、平稳过渡期、稳定增长期等三个强度发展区域。轴压比表现为SCC-1、ISCC-2均大于0.80,表现为高强混凝土的性质。弹性模量试验研究表明,当抗压强度偏低,未达到高强混凝土范围时,铁尾矿砂自密实混凝土弹性模量与普通混凝土相似,当铁尾矿砂自密实混凝土抗压强度达到高强混凝土范围时,采用自密实混凝土弹性模量计算公式进行数据拟合对比,结果最为接近,但当抗压强度继续增长时,其曲线偏低,已经不适用于铁尾矿砂自密实混凝土。5、研究了普通自密实混凝土和不同铁尾矿砂取代率的铁尾矿砂自密实混凝土的耐久性能。在碳化时间发展指数b和混凝土周围CO2浓度C一定的条件下,碳化速率系数a反映了自密实混凝土碳化深度随碳化时间变化情况,即SCC-1和ISCC-2的碳化速率相近；根据Tang提出氯离子扩散系数标准,SCC-1和ISCC-2在标准养护7d、28d和56d之后氯离子抗渗性试验结果均满足抗氯离子侵蚀性能较好等级。6、采用压汞测孔法(MIP)系统地研究了水泥基净浆和水泥基砂浆的微细观孔隙特征参数以及孔隙体积分形维数。三种水泥基净浆孔隙特征参数随龄期变化特点没有明显的规律性；水泥基砂浆各特征参数随龄期变化无明显突变,说明材料性能的稳定性。加天然砂的SCC-1与掺加40%铁尾矿砂的ISCC-2孔隙结构特征参数表现数据较为接近,说明加入铁尾矿砂后,其微观孔隙结构并未发生明显劣化趋势。本文水泥基材料的孔隙结构分布可以用三个阶段的参数描述,即微孔阶段的分形维数,大孔阶段的分形维数和过渡阶段的孔隙特征参数。7、采用扫描电镜(SEM)、X射线能谱分析(EDS)和X射线衍射分析(XRD)的方法,研究了三种水泥基净浆和两种自密实混凝土随龄期变化的微观形貌、水化产物的特点、微观缺陷、C-S-H凝胶能谱定性或半定量分析以及物相分析。三种净浆和两种自密实混凝土主要水化产物的早期微观形貌具有相似的特点。引入原子率(Atomic ratio)的概念,采用Ca/Si原子率和(Al+Fe)/Ca原子率的比值反应微区全谱扫描水化硅酸钙凝胶晶体的结构致密性。在界面过渡区,两种配比的自密实混凝土均表现出明显偏高的Ca/Si原子率,与水泥浆基体存在明显的差别,随着龄期的增长,界面过渡区的宽度在逐渐减小,同时ISCC-2的界面过渡区宽度总体偏小于同龄期的SCC-1的宽度。从水化过程来看,铁尾矿砂物相中,发现了铁尾矿砂中的某一种或几种物质参与水泥浆基体水化过程,致使水化过程中铁尾矿砂的物相衍射峰发生明显变化。更多还原

【Abstract】 The research, modern industrial waste used in the preparation of cement-based materials to eliminate or mitigate a serious impact on the environment, will become a focus area. Based on the reality of a large number of abandoned iron mine tailings produced from Huoqiu iron ore in Anhui province, the iron mine tailings was used as fine aggregate to replace part of the natural sand for self-compacting cement-based materials.The properites of iron mine tailings self-compacting cement-based materials were studies by the tests in this paper. The corresponding research works were summarized as follows:1. Raw materials of self-compacting cement-based materials were analyzed by Analysis of macroscopic features and microscopic techniques.The research contents were as follows:1) Analysis of macro-technical indicators;2) Qualitative and semi-quantitative analysis of raw materials were carried out by X-ray spectroscopy analysis(EDS);3) Phase analysis of raw materials was carried out by X-ray diffraction (XRD). The results can provide a basis for the properties of iron mine tailings self-compacting cement-based materials.2. The workability of iron mine tailings cement-based grouting material(IM) was studied with iron mine tailings ratio and water-binder ratio as variables.The results showed that performance index values of the workability for IM-2and M-lwere better than the others. The dynamic stability test and the static stability test were used the workability evaluation of iron mine tailings self-compacting concrete (ISCC) and self-compacting concrete (SCC). The results showed that ISCC-2and SCC-1had good work performances.3. Rheologies of IM and ISCC were first studies by the test methods in China.The Couette inverse problems for a Bingham fluid:"Reiner-Riwlin" equation and a Herschel-Bulkley fluid were derived by integration approach. The results showed that rheological curves of cement-based grouting material can meet Herschel-Bulkley fluid constitutive model with nonlinear characteristics, and IM-2had smaller shear stress than M-1when shear rates had the same values at the same point in time. Rheological curves of self-compacting concrete can meet Bingham fluid constitutive model with linear characteristics, and ISCC-2had greater shear stress than SCC-1when shear rates had the same values at the same point in time.4. Basic mechanical properites of iron mine tailings self-compacting cement-based materials were studies in different ages. The results showed that compressive strength of paste containing extre-fine natural sand was greater than paste containing iron mine tailings in different ages, but flexural strength had the opposite characteristics. Early compressive strength of cement-based grouting material rapid developed, and compressive strength of IM-2and M-1were more than 20MPa in one day age. There were similar growth laws for compressive strength of ISCC and SCC with ages, and the early strength development can be divided into three stages:the rapid development, the smooth transition and the steady growth.5. Carbonation resistance and anti-chloride penetration of ISCC and SCC has been studied to be used to reflect the durability. The results showed that carbonation ratesof ISCC-2and SCC-1were similar and had good performance of anti-chloride penetration.6. Pore characteristics and pore fractal dimension of cement-based paste and self-compacting concrete were studied by the mercury intrusion porosimetry (MIP) method. The results showed that pore characteristic parameters of three cement-based pastes change with can not find out apparent regularity. The test data of ISCC-2and SCC-1on pore characteristic parameters were close; the results showed that the microscopic pore structure of ISCC-2was not obvious deterioration trend after iron mine tailings added.7. Morphology, hydration products and micro-defects of three cement-based and two types of self-compacting concrete were investigated with ages by SEM, EDS and XRD, and the C-S-H gel was analyzed. The results showed that there were similar characteristics for early morphology of hydration products of three cement-based and two types of self-compacting concrete. Based on the phase analysis of the hydration products, new material has been found out when iron mine tailings involved in the hydration process.更多还原