硅粉、矿渣微粉、粉煤灰在制备高性能胶凝材料中的应用

介绍了硅粉的特性,探讨了硅粉单独使用的优缺点,以及利用硅粉、矿渣微粉、粉煤灰等三种物料生产高性能胶凝材料的生产过程。硅灰通过内掺法掺入混凝土,可等量替代部分水泥,有效取代系数达3～4,最佳掺入量为8%～10%。实践表明,该胶凝材料能很好地改善混凝土性能,具有较好的经济效益和社会效益。     

冲击荷载作用下SFFAC材料性能研究

利用SHPB试验设备对硅粉粉煤灰双掺混凝土(SFFAC),进行冲击试验,通过改变硅粉和粉煤灰的掺量来进行对比试验。结果表明,硅粉的加入对混凝土的动态力学性能有较大的改善,较理想的硅粉掺量为16%。同时还可以发现,粉煤灰的加入不仅不会降低硅粉混凝土的强度,还能提高混凝土工作性,与素混凝土相比,硅粉粉煤灰双掺混凝土(SFFAC)具有更好的抗冲击性能。     

钢包用低硅湿式喷补料的开发

研究了超细硅粉用量对材料各项性能的影响。其结果表明，减少超细硅粉的用量，可提高材料的耐蚀性和耐热震性，从而提高了使用寿命。     

掺纳米硅粉和掺粉煤灰防火耐热混凝土性能的比较

对掺纳米硅粉和掺粉煤灰防火耐热混凝土性能进行了研究.测试了高温煅烧前后混凝土试件的尺寸、质量及耐压强度,试验结果表明,掺入纳米硅粉能显著降低混凝土的高温收缩变形值及高温质量损失率,能显著提高混凝土的烧后耐压强度及相对耐压强度.掺5％纳米硅粉的混凝土与掺25％粉煤灰的混凝土相比,其高温收缩变形值约降低15.2％,质量损失程度约降低10.2％,烧后耐压强度约提高25.4％,而与不掺纳米硅粉的混凝土相比,其烧后耐压强度提高41.4％ ～ 90.5％,试验表明纳米硅粉比粉煤灰更能改善混凝土内部的微结构,提高混凝土的高温耐热性能.     

混凝土中微硅粉的应用

介绍硅金属炉冶炼烟气回收的微硅粉在混凝土中应用情况，实验数据证明在混凝土中添加一定比较微硅粉，混凝土强度和耐久性等理化指标均有明显改善，同时展望了微硅粉的应用前景。     

铁合金冶炼副产物微硅粉的性能及用途

微硅粉是冶炼硅系产品的副产物,被广泛应用于水泥、混凝土等行业。文章论述了微硅粉的形成过程、理化性能、国内外应用现状,并展望了微硅粉的发展趋势和方向。     

寒冷地区硅粉增强玄武岩纤维路面混凝土抗冻性能研究

为探究硅粉对玄武岩纤维路面混凝土抗冻性能的增强效果及改性机理,采用快冻法研究了不同硅粉掺量下玄武岩纤维混凝土质量损失、相对动弹模量、抗弯拉强度随冻融次数的衰减规律;借助压汞法(MIP)以及扫描电子显微镜(SEM),分析冻融前后孔结构及界面结构的演化,从细微观层面揭示硅粉增强机理。研究结果表明:9%(质量分数)硅粉掺量的玄武岩纤维路面混凝土抗冻性能增强效果最佳,相比基准混凝土,冻融320次后质量损失率降低了62.35%,相对动弹性模量提高了14.68%,抗弯拉强度提高了43.89%;MIP测试表明,掺入硅粉能够细化混凝土内部孔结构,减少孔隙数量,优化孔的分布,阻抑最可几孔径和临界孔径的增长;SEM分析发现,掺入硅粉能够改善纤维-水泥石与骨料-水泥石的界面区结构,提高玄武岩纤维路面混凝土的抗冻性能。     

陶瓷粗骨料混凝土抗氯离子渗透性能试验研究

试验采用电通量法研究了陶瓷粗骨料、矿物掺合料掺量对混凝土抗氯离子渗透性能的影响.试验结果表明:陶瓷粗骨料掺量对混凝土抗氯离子渗透性能影响不大,与普通混凝土一样,其渗透性能等级为Q-Ⅱ;28 d龄期时,电通量随着粉煤灰掺量的增大略有增加;龄期继续增长,粉煤灰的掺入明显改善了混凝土抗氯离子渗透性能.复掺硅粉后,随着硅粉的增加,混凝土的电通量明显降低,硅粉的掺入大大提高了混凝土的抗氯离子渗透能力.     

矿物掺合料对轻集料混凝土性能影响研究

通过将不同掺量粉煤灰、矿渣粉及硅灰等量取代水泥制备成轻集料混凝土,然后分别测试坍落度和不同龄期抗压强度,探讨矿物掺合料对轻集料混凝土工作性能及力学性能的影响。结果表明:粉煤灰掺量控制在20%内能避免混凝土沁水离析,可有效提升了轻集料混凝土的工作性能和力学性能;轻集料混凝土的坍落度随着矿渣粉的增加呈先减后增,抗压强度随之先增后减,故低掺量矿渣粉等量取代水泥对轻集料混凝土的工作性能和力学性能提升效果更好;高掺量硅灰混凝土的后期抗压强度小于低掺量,制备硅灰轻集料混凝土的硅灰掺量建议控制在10%左右。     

早期强度对混凝土抗裂性能的影响研究

在本文中,笔者通过大量实验来探究不同掺量的粉煤灰、矿渣粉以及硅粉对混凝土强度和抗裂性能的影响。试验结果表明:单掺15%粉煤灰、20%矿渣粉控制混凝土早期强度增长速率最显著;单掺10%硅粉提高混凝土早期强度增长速率最显著,并增加单位总开裂面积至715mm~2/m~2。单掺不同掺量粉煤灰、矿渣粉和硅粉不能同时满足抗裂性能和强度要求,研究发现,复掺15%粉煤灰无矿渣和7%硅灰可以满足混凝土强度性能,混凝土抗裂敏感性最差达到55h,通过添加0.5%葡萄糖酸钠缓凝剂,可以对早期强度增长率起到延缓作用,将混凝土抗裂敏感性提升到78h。     

Exploitation of poor Greek kaolins: strength development of metakaolin concrete and evaluation by means of k-value

In this paper, the effect of metakaolin on concrete properties is investigated. A poor Greek kaolin was thermally treated at defined conditions, and the produced metakaolin was superfine ground. In addition, a commercial metakaolin of high purity was used. Eight mixture proportions were used to produce high-performance concrete, where metakaolin replaced either cement or sand in percentages of 10% or 20% by weight of the control cement content. The strength development of metakaolin concrete was evaluated using the efficiency factor (k-value). The produced metakaolin as well as the commercial one imparts a similar behavior with respect to the concrete strength. Both metakaolins exhibit very high k-values (close to 3.0 at 28 days) and are characterised as highly reactive pozzolanic materials that can lead to concrete production with an excellent performance.     

偏高岭土对高流动性钢纤维混凝土早期力学性能和细观结构的影响

为了提高泵送混凝土流动性及早期力学性能,降低水泥用量,本文研究了高流动性偏高岭土和钢纤维复合混凝土的流动性、抗压和抗拉强度、弹性模量、破坏形态和微观结构,并在此基础上评价了偏高岭土和钢纤维对混凝土性能的影响。结果表明,随着钢纤维和偏高岭土含量的增加,浆体的流动性降低,偏高岭土影响更加显著。偏高岭土提高了钢纤维混凝土养护7 d后的抗压强度、抗拉强度和弹性模量,钢纤维对残余拉伸强度和裂纹扩展有明显的影响。通过扫描电镜(SEM)观察与X射线衍射(XRD)分析,偏高岭土的添加使试样内部产生了更稳定的水化硅酸钙(CSH)凝胶、单硫型水化硫铝酸钙(AFm)和高硫型水化硫铝酸钙(AFt)等物质。这些产物减少了孔隙和缺陷的产生,增强了界面过渡区的粘结力。由于偏高岭土和钢纤维对和易性的影响机制分别为增加黏度和提升浆体的抗剪切能力,本质上都为阻碍各组分的相对运动,所以二者在降低混凝土流动性方面具有耦合作用。偏高岭土与钢纤维影响混凝土力学性能的阶段不同,前者在未开裂阶段,后者在开裂阶段。     

Effect of metakaolin dispersion on the fresh and hardened state properties of concrete

The use of pozzolanic materials such as metakaolin in mortars and concretes is growing. Their use is usually related to the promotion of hydraulic binder reactions or to the mitigation of expansive reactions that can occur in concrete. Introduction of fine particles such as metakaolins, can have a strong effect on fresh and hardened state properties. This paper aims to study the effect of metakaolin in concrete formulations with a preset workability and to assess the system rheology but also its hardened state properties such as mechanical strength. The effect that the dispersion of metakaolin particles induces on concrete microstructure, particularly in porosity, is discussed. Formulations were prepared with several metakaolin amounts and workability was controlled either with water or a high range water reducer admixture (HRWRA). The use of HRWRA can cause deflocculation of metakaolin particles, allowing workability control in concrete and leading to better efficiency and improved performance.     

Efficiency of mineral admixtures in concrete: Microstructure,compressive strength and stability of hydrate phases

The use of mineral additives in concrete such as fly ash, silica fume, natural pozzolan, metakaolin and calcined clay has become widespread due to their pozzolanic reaction and environmental friendliness. The microstructure characteristics of concrete including pore structure and interfacial transition zone (ITZ) with addition of metakaolin, silica fume and slag were investigated in this study. The experimental results show that the addition of mineral admixtures results in the denser ITZ, optimized pore structure and reasonable pore size distribution especially at later curing stages. Metakaolin presents the most distinct improvement effects on microstructure of concrete. The development of the compressive strength is quantificationally related to the total porosity and average microhardness of the ITZ. Importantly, the influence of metakaolin, silica fume and slag on concrete was analyzed from thermodynamic stability of hydrate phase aspects.     

辅助胶凝材料对预应力高强混凝土管桩强度及工艺的影响

为优化混凝土管桩生产工艺,以硅灰(SF)和偏高岭土(MK)作为辅助胶凝材料,研究硅灰和偏高岭土对不同蒸养时间下混凝土抗压强度的影响,并使用X射线衍射(XRD)和扫描式电子显微镜结合能量色散谱(SEM-EDS)分析其水化产物及微观结构。通过Design-Expert8.0软件设计Box-Behnken试验,以硅灰掺量、偏高岭土掺量和蒸养时间三个因素为自变量,蒸养混凝土抗压强度为响应值,构建多因素回归方程模型。结果表明:硅灰掺量为胶凝材料质量分数8%时,对抗压强度略有提高,提高幅度为6.2%,达到83.6 MPa;5%、8%和10%(质量分数)掺量的偏高岭土均可提高蒸养混凝土的抗压强度,蒸养4 h、8 h、12 h时,10%掺量的偏高岭土对混凝土抗压强度的提升幅度依次为15.6%、13.2%和13.6%,蒸养4 h、8 h和12 h对混凝土抗压强度影响不大。XRD和SEM-EDS结果表明,硅灰和偏高岭土均消耗了Ca(OH)₂,提升了水泥早期水化程度,可以改善内部孔结构。通过响应面法建立模型可以预测,当硅灰质量分数为6.6%、偏高岭土质量分数为10%、蒸养时间为8.6 h时,混凝土抗压强度最高,达到104.8 MPa,且具有较高置信度。     

偏高岭土及其在高性能混凝土中的应用

介绍了偏高岭石结构、火山灰性及其在高性能混凝土中应用研究现状。有关研究结果表明：偏高岭土可有效提高水泥砂浆和混凝土的强度，改善混凝土的抗渗性和耐蚀性，有效地抑制碱集料反应等，是一种很有开发应用价值的混凝土功能性掺合料。     

新型混凝土掺合料——高活性偏高岭土的研究进展

综述了偏高岭土在混凝土领域国内外的应用现状、研究进展。阐述了具有火山灰特性的偏高岭土在混凝土中的应用机理及其对混凝土微观和宏观性能的影响。     

偏高岭土对预制混凝土路面材料耐久性能影响的微观分析*

预制装配式混凝土路面因其养护时间短、维修方便、性能优异而发展迅速,但高温导致的膨胀应力造成混凝土内部裂纹的发生扩展,有害孔含量增加,造成预制混凝土耐久性能降低。而以偏高岭土作为辅助胶凝材料可显著改善预制混凝土路面材料的耐久性能。本文通过XRD和扫描电子显微镜研究了不同掺量（0%、9%）偏高岭土的净浆和混凝土的物相组成和微观形貌差异,对其改性机理进行了探讨。研究表明,偏高岭土在水化过程中能发挥火山灰活性和填充作用,提高水化产物的密实度,消除高温导致的微裂纹,改善界面过渡区结构,降低混凝土孔隙率。     

偏高岭土-水泥基材料力学性能研究进展

在配制水泥基材料过程中,利用活性材料替代部分水泥,可提高基体的力学和耐久性能,同时还可减少水泥用量,对节能减排有重大帮助.近年来偏高岭土(MK)活性材料开始受到广泛关注和研究,其对水泥基材料性能的影响研究也有重大进展.主要综述了MK对水泥基材料力学性能的影响研究进展,主要包括含杂质煅烧高龄粘土以及纯MK对砂浆和混凝土的早期和后期力学性能影响,MK与石灰石粉(LF)复掺对水泥基材料力学性能以及MK对超高性能混凝土(UHPC)的力学性能影响,最后对MK-水泥基材料的未来研究方向进行了展望.     

Assessment of binary and ternary blends of metakaolin and Class C fly ash for alkali-silica reaction mitigation in concrete

The potential for binary and ternary blends of metakaolin, with two differing particle size distributions, and Class C fly ash to mitigate alkali-silica reactions (ASR) with a highly reactive fine aggregate were evaluated using accelerated mortar bar test (AMBT) and concrete prism test (CPT) methods. Binary blends of metakaolin or Class C fly ash reduced expansion by 55–90% and 25–37% compared to the control, respectively. When incorporating metakaolin with a lower mean particle size, binary blends showed a greater reduction in expansion compared with Class C fly ash. Ternary blends of metakaolin and Class C fly ash resulted in a marginally higher expansion than binary blends incorporating the same amount of metakaolin. Correlation between AMBT and CPT results was good at high levels of expansion but poor for those compositions producing expansions near the acceptable limits corresponding to increased addition rates of metakaolin and/or Class C fly ash.