不同粉磨方式矿渣粉对矿渣水泥流变性的影响

用激光粒度分析仪（LPS）研究了球磨和立磨粉磨的矿渣粉的粒度分布，用旋转粘度计对矿渣水泥的流变性能进行了测量。发现：球磨机所加工的矿渣粉比立磨加工的矿粉颗粒尺寸分布宽、细颗粒含量高；矿渣粉比表面积相近时，矿渣掺量在小于30%和大于40%时由球磨矿渣粉制成的矿渣水泥比立磨矿渣水泥的屈服应力和粘度小，而掺量在30%～40%之间时球磨矿渣水泥的粘度和屈服应力较立磨的稍大。此外，对矿渣粉颗粒群与水泥流变性之间进行了灰色关联分析，发现小于10μm的矿渣颗粒增加了水泥浆的屈服应力和粘度，而大于10μm矿渣颗粒却削弱了水泥浆的屈服应力和粘度。     

不同粉磨方式下高炉矿渣粒度特征的分析比较

为了客观地评价球磨和搅拌粉磨的设备效能,并为高炉矿渣高效制备技术的开发研究提供相关的试验研究数据,采用小型球磨和搅拌磨制备不同粒度的高炉矿渣产品,对不同粉磨方式下高炉矿渣的颗粒群粒度分布特性进行分析研究。结果表明,小型球磨及搅拌磨产品的粒度分布均符合Rosin-Rammler-Bennet分布;随着粉磨时间的延长,颗粒粒径减小;搅拌磨的粉磨效率较高,其高炉矿渣产品的粒度分布较窄。     

磷渣粉颗粒分布对水泥胶凝体系力学性能的影响

采用激光粒度仪对比表面积分别为340m~2/kg、420m~2/kg、500m~2/kg的磷渣粉颗粒粒度分布特征进行了分析,在此基础上运用灰色关联理论研究了磷渣粉颗粒分布与水泥胶凝体系3d、28d、180d力学性能的内在关联。结果表明:不同比表面积的磷渣粉具有不同的颗粒群粒度分布特征,磷渣粉颗粒分布中粒径大于20μm颗粒与水泥胶凝体系3d、28d抗折强度负关联、与180d抗折强度正关联;粒径小于20μm的磷渣粉颗粒对水泥胶凝体体系各龄期抗压强度均有促进作用,其中1~3μm的颗粒对3d抗压强度促进作用最显著、10~20μm的颗粒对28d、180d抗压强度发展促进显著。     

KHM170型卧辊磨制备钢渣超细粉工业试验研究

基于KHM170型卧辊磨的钢渣超细粉制备终粉磨工业试验系统,在给定钢渣粉、矿渣粉、水泥熟料粉的质量和粒度范围内,进行用钢渣粉部分代替矿渣粉制作水泥混凝土的强度试验。结果表明,KHM卧辊磨终粉磨系统可以实现钢渣超细粉终粉磨,可用于以热焖渣、滚筒渣为原料制备钢渣微粉的工业化生产;矿渣粉中掺加质量分数不超过30%的钢渣粉,且在满足钢渣粉比表面积大于矿渣粉比表面积和水泥熟料粉比表面积时,可以作为优选的混合材料大量用于混凝土。     

矿渣微粉的多度域分形研究

以4种不同的矿渣微粉为研究对象,应用分形理论研究矿渣微粉的粒度分布、颗粒外形轮廓和化学成分等3个度域上的分形特征。结果表明,矿渣粉体在不同度域上都呈现良好的自相似性,具有多度域分形特征;随着矿渣粉粒度的减小,其分形维数相应增大,分形维数在2~3之间,矿渣微粉单个颗粒的分形维数约为1.01;矿渣化学组成中主要成分的阳离子场强与其相应的累积分布具有自相似性,分形维数越大,矿渣的质量越好。     

钽粉颗粒强度的研究

研究了采用激光粒度分布仪测试电容器级团化钽粉粒度分布及强度的方法.其中心内容是:先采用3种不同比表面积、松装密度和费氏平均粒径的钠还原原粉,按3种烧结工艺制得团化钽粉.然后把烧结得到的6种试样加入纯水中,以200～300 r/min进行高速搅拌并以40 W,42 kHz超声波振动.将激光衍射分析仪的激光束穿过经不同搅拌时间的悬浊钽粉,测得不同时间的钽粉粒径分布曲线.分析分布曲线可以获得团化钽粉的一系列信息,包括:①几种团化钽粉颗粒的相对强度;②影响团化钽粉颗粒强度的因素;③钽粉强度和其他性能如介电损耗、流动性,平均粒径及密度的关系等.     

混凝土中硅粉的作用机理

硅粉比表面积大,颗粒极细,其主要的化学式是SiO_2,硅粉中二氧化硅的含量越高,细度越细在碱性溶液中的活性就越大,其对混凝土的改性效果也就越好。硅粉能够改善硬化水泥浆体的微结构,具有很高的火山灰活性,通常使用其作为一种辅助性的胶凝材料;硅粉作为掺合料在混凝土中可以替代部分的水泥,并改善水泥颗粒粒径分布和级配。     

低活性酸性矿渣粉细度对胶结充填体早期强度的影响

为了解决以活性较低的酸性矿渣粉开发的胶凝材料胶结充填体早期强度较低的问题,利用对矿渣粉粉磨不同时间的机械活化来研究矿渣粉细度对早期强度的影响。结果表明:对原状矿渣粉粉磨1、1.5 h后,相对于原状矿渣粉的比表面积404.7m~2/kg,矿渣粉比表面积分别增大为521、577.2 m~2/kg;粉磨1 h矿渣粉的3 d抗压强度提高了33.3%,7 d抗压强度无明显增长;粉磨1.5 h矿渣粉的3、7 d抗压强度分别提高了22.2%、18.1%;矿渣粉胶凝材料的水化产物主要以针状钙矾石和团絮状C-S-H凝胶物为主,与骨料紧密粘结构成整体。     

颗粒几何特性对水泥性能的影响

颗粒群的几何特性,即颗粒大小、粒度分布和颗粒形状.本文中论述了水泥颗粒的几何特性对水泥性能的影响.实验研究表明,水泥中3～40μm颗粒含量越多、颗粒球形度越高,水泥强度越大.     

水泥粒度分布对水泥性能影响的研究进展

从两个方面总结了水泥粒度分布对水泥性能影响的研究进展,一方面总结了反映水泥颗粒群整体情况的特征参数比表面积S、特征粒径x′和均匀性指数n对水泥性能的影响;另一方面总结了不同粒径区间水泥颗粒的性能。介绍了描述水泥粒度分布的RRB方程和Fuller曲线,综述了理论上粒度分布对水泥性能的影响情况,认为水泥的粒度分布是与其性能有明确定量关系的细度参数,是水泥粉磨细度控制的最终目标。     

钢渣细度和掺量对钢渣复合水泥力学性能的影响

为找出在钢渣复合水泥中钢渣的最佳细度和最佳掺量,从钢渣的粉磨时间、掺量、不同助磨剂的作用和水泥配比等方面研究钢渣细度及掺量对复合水泥力学性能的影响,分析各个影响因素的作用。结果表明,随着磨细钢渣粒度的减小,钢渣复合水泥的抗折、抗压强度会有不同程度的提高;磨细钢渣的掺量为10%和20%时,钢渣复合水泥的力学性能较好,抗折、抗压强度甚至超过纯水泥;当掺量为30%和40%时,复合水泥力学强度下降幅度较大,3 d抗折强度不符合国家标准规定。     

Pozzolanicity of finely ground lightweight aggregates

This paper examines the pozzolanic behavior of finely ground lightweight aggregates with a mean particle size between 4 and 26 μm. Cement pastes are made with a 20% mass replacement of cement with finely ground lightweight aggregates, fly ash, quartz, and limestone in addition to a control paste with no cement replacement. Isothermal calorimetry, thermogravimetric analysis, and compressive strength testing as well as thermodynamic calculations are performed on these pastes. Isothermal calorimetry and compressive strength testing are shown to not be able to clearly distinguish and quantify the pozzolanic response of the finely ground lightweight aggregates, fly ash, quartz, and limestone when they are used in cement pastes. However, thermogravimetric analysis and thermodynamic calculations clearly show that the finely ground lightweight aggregates are pozzolanic through the consumption of calcium hydroxide. A pozzolanic reactivity test based on isothermal calorimetry also confirms that the finely ground lightweight aggregates are pozzolanic. These results indicate that finely ground lightweight aggregates are pozzolanic and could be used in concreting applications.     

Grey correlation analysis between strength of slag cement and particle fractions of slag powder

The particle size distributions of slag powder were investigated by Laser Scatter equipment. The influence of particle fractions of slag powder on the compressive strength of slag cement composed of 50% slag powder and 50% Portland cement was also studied by the method of grey correlation analysis. The results indicated that the volume fraction of particles 5–10 μm had a maximum positive effect on the mortar compressive strength of slag cement at 7 d and the volume fraction of particles 10–20 μm had a maximum positive effect on the mortar compressive strength at 28 d, whereas the volume fraction of particles larger than 20 μm had a negative effect on the mortar compressive strength at 7 and 28 d.     

Jet mill grinding of portland cement,limestone, and fly ash: Impact on particle size,hydration rate,and strength

While the majority of commercial ordinary portland cement (OPC) is ground using a ball mill or a vertical roller mill, other industries have shown that jet mill grinding can be an alternative approach for grinding materials. This paper investigates the potential application of jet mill grinding for two systems. The first system is a blend of OPC and 15% limestone, and the second system is a blend of OPC and 40% fly ash. It was observed that when jet mill grinding is used, the average particle size of the powders is decreased to approximately 4 μm or less with a narrower particle size distribution than that achieved using ball milling. In addition to evaluating the size and shape of the particles obtained from the jet mill grinding process, this paper focuses on evaluating, using isothermal calorimetry, the effect these changes in particle size and distribution have on the extent and rate of hydration as well as their effect on the compressive strength of cement pastes or mortars.This study also investigated differences between inter-grinding and blending separately ground materials to form an OPC/limestone mixture. Both inter-ground and separately ground OPC/limestone mortars demonstrated an accelerated hydration at early ages accompanied by an increase in early age strength. This appears to be primarily due to the increased surface area of the finer particles that provides more available surface for the hydration reaction. The inter-grinding appeared to be more effective than grinding the materials separately because an improved graded particle size distribution was obtained. The inter-ground OPC/limestone mixture shows accelerated initial hydration at water to powder ratios (w/p, where powder = cement + limestone) of 0.50 and 0.35 when compared with the samples before grinding. At the lower w/p of 0.35, the OPC/limestone mixture appears much more efficient. In the OPC/fly ash mixture, jet mill grinding also accelerates the rate of hydration and strength development.     

水泥浆体中连续粒径粉体的堆积密度研究

为了研究粒径分布对水泥石结构与性能的影响,通过测定多组粒径分布不同的矿粉在流动度相同情况下的需水量,得到矿粉不同粒径分布所对应的不同的堆积密度,推导了浆体中连续粒径粉体的堆积密度公式。用该公式计算上述不同粒径分布的矿粉浆体的堆积密度及需水量,计算结果与试验值基本吻合。说明该公式可以用来模拟诸如水泥、磨细矿渣、粉煤灰等胶凝材料细颗粒的堆积密度。     

稻壳纤维粒径和掺量分数对水泥复合材料性能的影响

以稻壳纤维（Rice husk fiber,RHF）为增强材料,以水泥为基体,制备了RHF/水泥基复合材料。研究了粒径对RHF在水泥基体中分散性能的影响;并以RHF粒径和掺入质量比为考察因素,采用响应曲面法,以RHF/水泥基复合材料的密度、抗折强度、含水率、吸水率和导热系数为响应值,建立数学模型,对RHF/水泥基复合材料的成型工艺进行优化设计。结果表明：RHF的粒径越小,在水泥基体中分散性能越好,粒径为150 μm的RHF分散系数达到最大值,为0.981;响应曲面模型分析表明RHF的粒径为150 μm、掺入质量为水泥质量的3%时,RHF/水泥基复合材料的性能达到最优,此时RHF/水泥基复合材料的密度为1 559.26 kg/m³,抗折强度为9.38 MPa,含水率为7.05%,吸水率为16.71%,导热系数为0.50 W/（m·K）,达到了建筑行业标准JC/T 411-2007的要求。     

Particle Size Distribution of Limestone Fillers: Granulometry and Specific Surface Area Investigations

Mineral fillers can be defined as “inert materials included in a mix design for some useful purpose” (NF P18-508 Janvier 2012). They can be added to compounds in order to complete a large variety of final properties without increasing costs or to improve specific characteristics like hardness, brittleness, impact strength, compressive strength, softening point, fire resistance, surface texture, electrical conductivity, and so on. In Belgium, locally available limestone fillers are specifically very well adapted for the optimization of particle packing and flow behavior of cementitious pastes in concrete mixes. Limestone fillers may be easily characterized in terms of chemical and mineralogical properties. These properties are fundamental for the study of the behavior of concrete mixes in fresh state and for understanding interactions existing at the level of the interfacial transition zone between aggregates and cement paste. These properties are however insufficiently discriminant and particle size, as well as shape distribution, seem to have a potential influence on physical phenomena which happen during the setting process. The aim of this article is to compare five major techniques used to quantify the size and the shape of limestone fillers particles: laser diffraction scattering, wet sieving, and image analysis for particle size measurement; and BET adsorption and Blaine permeability methods for specific surface area.     

Spherical dendritic particles formed in cavitation erosion

Micro spherical particles were found in a vibrating cavitation erosion experiment. Examination of the spherical particles reveals the dendritic pattern on the surface and the hollow structure of the interior. The surface and interior structures of the particle are also related to the particle’s size. For smaller particle, the dendritic structure is replaced by the fine cell and the interior becomes solid. Such special structures are considered to be the result of particle’s solidification from molten state at a rapid cooling rate, which happens in a special transient environment with transient high temperature and high pressure provided by cavity collapsing. The specific area and surface tension force are the main reasons for the different structures of the particles in different size.