Effects of Spherical Light-weight Aggregates Additions on Workability and Mechanical Properties of Al_2O_3-SiO_2 System Castables

In order to clarify the effect of spherical light-weight aggregates addition on properties of A12 07 - Si02 system castables, adopting ATO mullite traditional light-weight aggregates and ATO mullite spherical light-weight aggre- gates, bauxite homogenization powder, microsilica , cal- cium aluminate cement as main raw materials, light- weight Al2 03 - SiO2 system castables were prepared by replacing conventional light-weight aggregate with spherical light-weight aggregates. The effects of spheri- cal light-weight aggregates addition on workability, me- chanical properties of castables after heated at different temperatures were researched; the microstructure of the aggregates was analyzed by SEM. The result shows that the introduction of spherical light-weight aggregates can significantly improve the flowability and reduce the water addition of the castables. Water demand of the castable is reduced from 18% with the conventional light-weight aggregates to 14% with spherical light-weight aggre- gates. In addition, light-weight castables prepared by spherical aggregates can keep the same workability with- in a wider range of water addition. Therefore, spherical aggregates are user-friendly. The introduction of spheri- cal light-weight aggregates is favorable to packing densi- ty and mechanical properties of castables, such as cold crushing strength, cold modulus of rupture, hot modulus of rupture at 1 200℃.

Effects of Spherical Aggregates Addition on Properties of Al2O3-SiO2 System Castables

Compared with traditional aggregates,spherical aggregates with high flowability,easy control of particle size distribution and favor of dense packing and so on,are expected to replace traditional aggregates as important raw materials for future high performance refractories. Therefore,investigation of effects of spherical aggregates addition on properties of refractories becomes very meaningful. Using A70 mullite traditional aggregates and A70 mullite spherical aggregates, bauxite homogenization powder,microsilica,and calcium aluminate cement as raw materials,different AlO-SiOsystem low cement castables were prepared by replacing conventional aggregates with spherical aggregates. The effect of spherical aggregates addition on workability and mechanical properties of castables after heated at different temperatures was researched,and microstructure of the specimen was analyzed by SEM. Compared with traditional irregularly shaped aggregates,spherical aggregates endow castables with better flowability and easy pump ability. By introduction of spherical aggregates into the castables,flowability and pumpability are significantly improved,and water addition and ball completely sunk time are reduced. The introduction of spherical aggregates is favorable to density and cold crushing strength of castables,but unfavorable to CMOR. The effect of spherical aggregates addition on HMOR at1 400 ℃ can be negligible. Microstructure analysis showsthat the boundary bonding between spherical aggregates and matrix is strong,similar to the traditional aggregates.

Synthesis of Lightweight Spherical Forsterite Aggregates and Research on Their Application in Mgo Based Castables

Magnesite fine powder, natural silica powder,light-burned magnesia fine powder, silica fume and middle grade magnesia fine powder were used as the starting materials,and silica sol as binder to get high purity lightweight spherical forsterite aggregates. The mixture was granulated on a disc pelletizer and then calcined at 1 400 ℃ for 3h. The synthesized spherical forsterite aggregates were added in Mg O based castables with MgO-SiO2-H2O binding system to replace equaldensity high purity common forsterite aggregates. Effect of spherical forsterite aggregates addition on properties of MgO based castables was investigated. The results show that: compared with common aggregates,lightweight spherical forsterite aggregates can improve castables ’flow ability and decrease water addition; addition of spherical aggregates has little effect on cold strength of castables; with the increase of spherical aggregate addition,shrinkage of specimens after drying and heating at intermediate temperatures decreases,but the expansion of specimens after heating at high temperatures increases,bulk density decreases and apparent porosity increases,and thermal conductivity declines.

Influence of Kyanite Content on Microstructures and Properties of Castables Containing Spherical Lightweight Mullite Aggregates

Five lightweight mullite castables were prepared using the lightweight mullite aggregate（M45A） with narrow particle size distribution and spherical shape,mullite powder（M45P）,kyanite powder,microsilica and Secar 71 cement as raw materials. After the specimens fired at 1100 ℃,1200 ℃ and 1300 ℃ for 3h,respectively,the effects of kyanite contents（ 8%,10%,12%,14%,16% by mass） on the physical properties,phase composition and microstructures were investigated through an X-ray diffractometer（ XRD）,a scanning election microscopy（ SEM） and a microscopy measurement method,etc. The results show that,for the specimens fired at 1300 ℃ with the kyanite content from 8%to16%, the bulk densities and apparent porosities change little,but the cold modulus of rupture and the crushing strengths decrease significantly,and the linear change rates increase from-0.87% to 0.64%. The most apposite mode is the specimen containing 12% kyanite fired at 1300 ℃, which has a high crushing strength of 29.3 MPa,a low linear change of 0.18%,an apparent porosity of 36.8% and a bulk density of 1.73 g/cm^3.

Properties of Castables Made of Spherical Lightweight Mullite Aggregates

The castables were prepared from spherical lightweight mullite aggregates,bauxite,SiO2 fine powder,α-Al2O3 fine powder and calcium aluminate cement.The performance changes of the castables were studied after heat treatment at 110℃for 24 h,1100℃for 3 h,1200℃for 3 h and 1300℃for 3 h.The results illustrate that the cold modulus of rupture and hot modulus of rupture of the castable increase with the rising heat treatment temperature.The cold crushing strength shows a“V”change trend when the heat treatment temperature rises from 1100 to 1300℃.After the specimen is heat treated at 1300℃,the thermal conductivity is 0.500 W·m-1·K-1,0.586 W·m-1·K-1,0.595 W·m-1·K-1 at 300,600 and 900℃,respectively.The SEM analysis explains the change trends of these properties.The prepared lightweight mullite castables can be applied as the working lining of hot-blast furnaces.

Spherical Linear Diophantine Fuzzy Sets with Modeling Uncertainties in MCDM

The existing concepts of picture fuzzy sets(PFS),spherical fuzzy sets(SFSs),T-spherical fuzzy sets(T-SFSs)and neutrosophic sets(NSs)have numerous applications in decision-making problems,but they have various strict limitations for their satisfaction,dissatisfaction,abstain or refusal grades.To relax these strict constraints,we introduce the concept of spherical linearDiophantine fuzzy sets(SLDFSs)with the inclusion of reference or control parameters.A SLDFSwith parameterizations process is very helpful formodeling uncertainties in themulti-criteria decisionmaking(MCDM)process.SLDFSs can classify a physical systemwith the help of reference parameters.We discuss various real-life applications of SLDFSs towards digital image processing,network systems,vote casting,electrical engineering,medication,and selection of optimal choice.We show some drawbacks of operations of picture fuzzy sets and their corresponding aggregation operators.Some new operations on picture fuzzy sets are also introduced.Some fundamental operations on SLDFSs and different types of score functions of spherical linear Diophantine fuzzy numbers(SLDFNs)are proposed.New aggregation operators named spherical linear Diophantine fuzzy weighted geometric aggregation(SLDFWGA)and spherical linear Diophantine fuzzy weighted average aggregation(SLDFWAA)operators are developed for a robust MCDM approach.An application of the proposed methodology with SLDF information is illustrated.The comparison analysis of the final ranking is also given to demonstrate the validity,feasibility,and efficiency of the proposed MCDM approach.

A new measuring method for maximal length, width and thickness dimensions of coarse aggregates

In order to establish a new method for measuring the dimensions of coarse aggregates, five different-size flat and elongated (F&E) coarse aggregates were glued into two specimens by epoxy resin, respectively, and slice images were obtained by X-ray CT, then the aggregates were extracted by the fuzzy c-means clustering algorithm. Attributions of the particle on different cross-sections were determined by the ‘overlap area method’. And unified three-dimensional Cartesian coordinate system was established based on continuous slice images. The coefficient values of spherical harmonics descriptor representing particles surface profile were gained, then each scanned particle was represented by 60×120 discrete points conformably with spherical harmonics descriptor. The chord length and direction angles were determined by the calculation. With the major axis (L) and orthogonal axis (W and T), the calculated results were compared with those measured by caliper. It is concluded that the new L, W, and T dimension measuring method is able to take the place of the present manual measurement.

天然彩色盐制备方法的研究

文章介绍了一种具有球状结构的天然彩色盐及其喷雾制备方法,按重量百分计,所述彩色盐的主体成分氯化钠含量为80%~95%、彩色果蔬营养物质含量为5%~20%。文章所述方法获得彩色盐为球状团聚体,颗粒表面致密,彩色物质均匀分布、色泽稳定。该方法制备的产品颗粒超细,粒度分布均匀,平均粒径小,球形度高,流动性好,具有较好的抗结块性,该制备工艺简单、易于工业化生产。

随机球形骨料再生混凝土氯离子扩散研究

基于Monte-Carlo原理及Fuller级配理论,依据PYTHON算法及COMSOL软件建立由天然骨料、老界面区、老砂浆、新界面区及新砂浆组成的再生混凝土三维球形细观模型,模拟计算了不同骨料体积分数、老砂浆扩散系数及老砂浆厚度的再生混凝土内氯离子扩散过程,对比研究了再生混凝土抗氯离子侵蚀影响规律。研究表明:以随机理论建立的再生混凝土三维球形随机骨料模型接近真实再生混凝土细观结构,满足一般工程需要;基于该模型的氯离子细观数值模拟结果同试验结果吻合;再生骨料体积分数从10%增至30%、50%时,再生混凝土表观扩散系数分别增加了6.56%和19.43%;老砂浆扩散系数增加4倍,表观氯离子扩散系数增加19.28%;老砂浆厚度增加2倍,表观氯离子扩散系数增加8.1%,增加老砂浆的厚度和扩散系数会弱化再生混凝土抗氯离子侵蚀的能力。

基于模糊过滤排序法的复球形犹豫模糊多属性群决策方法

为有效分析属性值的概率分布对决策结果的影响,基于模糊过滤排序法提出属性权重和决策成员权重完全已知的复球形犹豫模糊多属性群决策方法。首先,定义复球形犹豫模糊集以及集结算子和满意度;其次,根据模糊过滤排序法构建复球形犹豫模糊多属性群决策模型;最后,运用算例验证所提方法的合理性和有效性。

氧化亚铜准球形聚集体的合成及其抗菌性能

以废弃葡萄果肉提取物(Waste grape pulp extract,WGPE)为还原剂,采用液相还原法将硫酸铜还原成氧化亚铜准球形聚集体(Cu_(2)O-SA),借助傅里叶变换红外光谱仪、X射线薄膜衍射仪、X射线光电子能谱、扫描电子显微镜和场发射透射电子显微镜等表征分析Cu_(2)O-SA的化学结构和形貌,测定反应条件对Cu_(2)O-SA形貌和粒径的影响,并评价Cu_(2)O-SA的抗菌效果。结果表明:以WGPE替代葡萄糖为还原剂或提高WGPE的浓度均有利于Cu_(2)O-SA的合成;提高还原剂浓度和反应温度可使Cu_(2)O-SA的粒径变小,粒径分布区间变窄,比表面积增大;Cu_(2)O-SA是通过晶粒团聚生长并相互融合形成的多晶粉末,且随着生长时间的增加Cu_(2)O-SA会发生聚集和表面重建;Cu_(2)O-SA对金黄色葡萄球菌和大肠杆菌的最小抑菌质量浓度均在3.125~6.250 g/L。该研究对氧化亚铜纳米颗粒的合成和抗菌领域的应用具有指导意义。

基于油石分离的再生集料颗粒形态多尺度变化

为研究废旧沥青混合料(recycle asphalt pavement,RAP)再生工艺对集料颗粒形态特征的影响,采用油石分离处置技术制备再生集料,建立考虑再生集料颗粒宏观-细观-微观的多尺度评价指标体系,结合三维扫描仪和集料图像测量系统测量新集料、未处置RAP和再生集料颗粒的球度、针片状指数、梯度棱角性和纹理指数等4个形态评价指标,对比分析3种集料颗粒的形态特征与多尺度变化规律。结果表明:相比于新集料颗粒和未处置RAP颗粒,再生集料颗粒的形态特征在宏观尺度上的指标参数变化不大,在微观-细观尺度上的指标变化较大,梯度棱角性平均减小12.5%,纹理指数平均增大14.0%,3种集料的4个形态指标均符合正态分布。相比于未处置RAP颗粒,再生集料颗粒的球度、梯度棱角性和纹理指数的标准差均明显变小,表明油石分离处置技术对改善再生集料颗粒的宏观-微观-细观形态特征的变异性有积极作用。对RAP进行高掺量再生利用时,应考虑再生集料颗粒的梯度棱角性和纹理指数与混合料路用性能的关联关系。

球型模糊Hamacher Hamy集成算子及其决策应用

基于对球型模糊Hamacher运算和Hamy均值算子的研究,将Hamacher运算和HM算子综合应用到信息集成当中,提出了球型模糊Hamacher HM算子,球型模糊Hamacher加权HM算子,分别研究其具有的性质,同时给出属性权重的确定方法。最后基于所提算子提出决策方法来解决球型模糊环境下的多属性决策问题,并通过示例验证所提出方法的可行性和有效性。

路用粗集料的三维形态表征及加工工艺影响分析

为定量分析路用粗集料的形状特征,采用高精度三维扫描仪获取集料表面的特征点阵,建立粗集料颗粒的实体模型;对集料二维与三维形态指标进行分析,探讨各指标的适用性;分析不同加工工艺对集料形态的影响。结果表明:不同视角下的集料轮廓周长和投影面积的差异较大,与集料扁平率指标密切相关,集料越接近针片状,二维轮廓的代表性越差;球度指标能够较好地表征集料三维粒型,集料越接近立方体状态,其球度值越大;椭球度指标可以较好地表征集料的棱角特性,棱角性越差,相应的椭球度值越大;反击破碎加工的集料球度偏低,棱角性较好;整形破碎加工的集料球度最优,但棱角性偏低;结合实际的需求,可以选择不同加工工艺组合掺配的形式,获得粒型与棱角性较均衡的集料成品。

球形随机骨料模型模拟自密实重晶石混凝土离析

近年来,具备良好防辐射性能及良好施工性能的自密实重晶石混凝土较多地用于核电站的建设,然而重晶石骨料密度较大,更容易导致混凝土离析,离析会对混凝土的质量产生重大不利影响,以往多采用试验方法研究,费时费力且数据离散性较大。本文将自密实重晶石混凝土看作由粗骨料和砂浆组成的两相复合材料,骨料看作刚性球体,砂浆采用宾汉姆流体模型,运用MATLAB编程语言编制了圆柱体投放域球形随机骨料模型程序sjgl,带入离析试验中相关参数在MATLAB中生成了随机骨料模型。然后将骨料模型中的骨料信息导出编辑了AutoCAD脚本文件,在AutoCAD中生成了随机骨料实体模型。运用FLOW3D软件中的一般运动物体(general moving objects)模型求解模型中大粒径骨料的离析,以此来近似代表随机骨料模型的离析。对应于自密实重晶石混凝土试验离析率计算公式,定义了随机骨料模型离析率,用“像素点法”计算随机骨料模型离析率为7.30%。对《自密实混凝土应用技术规程》(JGJ/T 283—2012)建议的离析率计算公式稍作调整定义了试验离析率,为9.81%。随机骨料模型离析率与试验离析率的相对误差为25.6%,由此论证了在误差允许的范围内圆柱体投放域球形随机骨料模型可有效模拟自密实重晶石混凝土离析。

青海湖底沉积物中球状白云石集合体的发现及其地质意义

青海湖为盐度低于海水的微咸水湖。为了探索白云石的成因,在青海湖二浪尖以北约15 km的湖底采集了长25cm的沉积物柱状样品。对样品所做的X-衍射矿物物相定量分析表明其中含有2.2%的白云石。文献中也曾报道青海湖底沉积物中含有高达10%的白云石矿物。对这些含白云石矿物的湖底沉积物所进行的扫描电镜研究发现了其中呈球状、椭球状,大小1-2μm的白云石集合体及其伴生的草莓状黄铁矿的存在。其特征与文献中报道的现代近海高盐度泻湖和萨勃哈中发现的微生物成因的白云石极为相似。这是内陆低盐度环境中此类白云石的首次发现,对于探讨不同盐度环境中白云石的形成机理,促进“白云石问题”的深入研究具有重要的理论意义。

镁橄榄石质轻质球形骨料的制备

为了降低镁基轻质浇注料在受热过程中的收缩并提高其初始强度,以菱镁矿细粉、天然硅石粉、轻烧MgO和SiO_2微粉为原料,使用硫酸镁溶液为结合剂,采用圆盘造粒机成型料球,分别在1 400、1 420、1 450℃下保温3 h煅烧制备了镁橄榄石质轻质球形骨料。分别研究了结合剂浓度、原料配比和煅烧温度对骨料体积密度、显气孔率、料球强度的影响。结果表明:以质量分数分别为71. 1%的菱镁矿、24. 6%的硅石粉、3. 8%的轻烧镁粉和0. 5%的SiO_2微粉配料,加入w(MgSO_4)=15%的硫酸镁溶液为结合剂,经1 420℃保温3 h可以制备性能较佳的镁橄榄石质轻质球形骨料。

集料形态特征对集料-沥青黏附及水稳定性的影响

为评价集料形态特征对集料-沥青黏附性及其体系水稳定性的影响,提出了一种定量测试集料-沥青黏附性的新方法.借助集料图像测量系统(AIMS)测试了5种集料的形态特征,并对不同形态集料沥青混合料的水稳定性进行评价,建立了集料形态特征与集料-沥青黏附性及水稳定性的关系,同时基于灰色关联法分析了集料形态特征对集料-沥青黏附性及水稳定性的影响排序.结果表明:提出的集料-沥青黏附性定量测试方法简单、可靠;沥青混合料水稳定性最佳的棱角性为2500~3000,球度为0.65~0.75;随着集料表面纹理的增大,沥青混合料的水稳定性增强;集料表面纹理对集料-沥青黏附性的影响最大,棱角性对沥青混合料浸水飞散损失指标的影响最大,球度对沥青混合料冻融劈裂强度比、浸水车辙变形拐点指标的影响最大.

粗骨料颗粒形状评定方法的研究

提出了粗骨料颗粒球度和形状指数的概念 。

球形颗粒遮弹层对高速侵彻弹体的作用机理

在钻地弹威慑之下,重要目标工事外覆盖遮弹层是常见加固和防护手段。硬质球形颗粒(以下简称颗粒)是常见的遮弹层组成结构。本文中将研究高速侵彻弹体与颗粒作用机理,分析遮弹效率的控制因素。首先,基于动态空腔膨胀理论,计及靶的自由面效应和颗粒强度差异,建立了靶对弹体侵彻阻力的表征模型。然后,采用弹靶分离计算方法,模拟并分析了斜侵彻含球形颗粒有限大高强混凝土时弹体的运动与变形,研究颗粒的强度、位置及尺寸对来袭弹侵彻行为的影响规律。结果表明,颗粒的遮弹作用主要取决于与其作用时弹体的姿态,其随颗粒位置变化无明显规律;颗粒强度越高,遮弹效果越好;颗粒半径从1倍到10倍弹径变化时,颗粒对弹体的作用机理从弹道偏转为主转变为弹道偏转与侵彻阻力增加两者耦合。因此,为达到良好的遮弹效果,单层球形颗粒密排遮弹层的颗粒半径建议在5倍弹体直径之上;若采用较小颗粒制作遮弹层,建议采用多层错排方式,且遮弹层厚度须在10倍弹径之上。