高钙粉煤灰颗粒群分布与其活性关系研究

将纯硅酸盐水泥、高钙灰按不同的粉磨时间和球配处理成若干个不同颗粒群分布的试样 ,高钙灰和水泥以各种颗粒群匹配 (高钙灰掺量均为 5 0 %)制成一系列粉煤灰硅酸盐水泥 ,进行胶砂强度检验。采用灰色关联分析方法研究了粉煤灰各粒径范围颗粒与粉煤灰水泥强度的相互关系。结果表明 :( 1 )高钙灰粒径在 1 0 μm以下的颗粒体积百分数与粉煤灰水泥的强度均为正关联 ,而大于 1 0 μm的颗粒与粉煤灰水泥的强度均为负关联 ,说明小于 1 0 μm的颗粒对强度增长有积极贡献 ,而大于 1 0 μm的颗粒对强度增长不利 ;( 2 )R -R分布表明 :在粉煤灰达到一定细度的条件下 ,宽分布试样可以有较多的小于 1 0 μm颗粒 ,从而对强度增长更为有利。     

粉煤灰粒度分布及其活性的灰色关联分析

用激光粒度仪测定不同细度粉煤灰的粒度分布,以灰色关联方法分析了粉煤灰粒度分布与其活性之间的相关性.研究表明:粉煤灰粒度分布明显影响其活性;0～19.953 μm范围内的颗粒体积分数与粉煤灰活性指数的关联极性均为正,说明这些颗粒对粉煤灰的活性有积极贡献;其中以5.012～19.953 μm的关联度为最大,说明该粒径范围内...     

煤矸石颗粒群分布与煤矸石水泥活性的关系研究

本文将纯硅酸盐水泥、煤矸石按不同的粉磨时间序列处理成若干个不同颗粒群分布的试样,配制成一系列煤矸石硅酸盐水泥(煤矸石掺量均为30％),进行胶砂强度检验。采用灰色关联分析方法研究了煤矸石各粒径范围颗粒含量与煤矸石水泥强度的相互关系。结果表明:(1)煤矸石粒径在10μm以下的颗粒体积百分数与煤矸石水泥的强度均为正关联,而大于10μm的颗粒与煤矸石水泥的强度均为负关联,说明小于10μm的颗粒对强度增长有积极贡献;而大于10μm的颗粒对强度增长不利。(2)R-R分布表明:在煤矸石达到一定细度的条件下,宽分布试样有较多的小于10μm颗粒。     

矿渣粒径范围与活性关系的研究及粒径分布的优化

通过图像分析仪结合相应的IPP软件测定了不同粒径区间中的矿粉颗粒的百分数;采用了灰色关联分析和建立GM灰色模型分析了粒径区间和矿渣水泥的活性指数的关系以及做了相应的动态分析.结果表明:矿粉在0-10μm粒径范围中,＜5μm粒径颗粒与活性的关联度最大,粒径增大则它与活性的关联度明显下降,颗粒粒径分布对矿渣早期强度的影响大于后期且对抗压强度影响略高于抗折强度;根据GM模型分析,＜3μm和5μm～8μm粒径的颗粒对矿渣水泥影响最大,尤其是在早期;当＜5μm粒径颗粒大于35％时候,矿渣的不同龄期的活性指数均有较大的提高.     

石灰石水泥颗粒分布与其强度的灰色关联分析

将石灰石和水泥熟料按不同比例混合共同粉磨,运用灰色关联分析方法,研究了石灰石水泥颗粒分布对强度的影响,并建立了28d抗压强度与0~40μm颗粒含量的GM(1,2)灰色模型。研究结果表明:石灰石水泥粉体中10~20μm的颗粒含量与3d强度的关联度最大,20~30μm对28d强度影响最大。     

浅谈试验小磨级配对熟料强度的影响

1问题的提出 JC/T853-1999<硅酸盐水泥熟料>中规定,对硅酸盐水泥熟料的物理性能检验,是通过将水泥熟料在φ500mm×500mm标准小磨中与二水石膏一起磨细至比表面积(350±10)m2/kg,80μm筛余不大于4%制成P·Ⅰ型硅酸盐水泥后来进行的.制成的水泥中SO3含量应在2.0%～2.5%范围内(也可按双方约定).标准中并没有规定标准小磨的钢球级配,只是对粉磨后熟料的比表面积和筛余进行了规定,但是标准规定的筛余范围较宽.我们知道,影响粉磨后水泥强度的因素主要是水泥的颗粒级配,现普遍共识是3～30μm的水泥颗粒对强度起主要贡献.我们通过近5年的生产实践发现,通过不同的级配方案,可在规定的范围内,粉磨出不同颗粒级配的水泥熟料,由此进行的熟料物理性能检测结果相差也较大,直接影响各企业之间熟料质量的相互比较.     

助磨剂对矿渣硅酸盐水泥性能影响的研究

实验采用有机化合物复配无机盐的方式,制成三种液体复合助磨剂,通过测定矿渣硅酸盐水泥细度、标准稠度、凝结时间、安定性和胶砂强度,研究不同助磨剂及助磨剂不同掺量对矿渣硅酸盐水泥物理性能的影响,并利用激光粒度仪和扫描电镜测试与分析了水泥的粒度分布和颗粒形貌.结果表明:三种助磨剂均能不同程度降低水泥筛余,提高水泥比表面积,提高幅度为2.9％～18.3％;掺入助磨剂后,水泥的颗粒形貌趋向于圆球形,水泥粒度分布发生变化,3～32 μm颗粒含量显著增加,中位粒径降低,其中B3水泥试样中位粒径为18.94 μm,降低了5.21μm;水泥凝结时间缩短,标准稠度变化不大,安定性符合国家标准;助磨剂能显著提高水泥各龄期胶砂强度.B3试样3d抗折强度为4.3 MPa,3d抗压强度为15.1 MPa,符合P·S 32.5R级标准要求.     

低品质粉煤灰作为水泥混合材的试验研究

采用超细粉磨技术对低品质粉煤灰进行改性,通过正交试验优化设计,结合 horsfield 紧密堆积理论与强度、经济性能分析,得到不同比表面积的粉煤灰最优复配比例与掺量,并确定超细粉煤灰复合水泥的最佳制备工艺.结果表明,当采用混磨制备工艺,三种不同细度的粉煤灰以1:2:3复配,掺量为30%时,制备的复合水泥能满足42.5 R强度等级要求,超细粉煤灰的掺入能改善复合水泥体系的粒径分布,使体系结构更为密实.     

颗粒分布对立磨水泥强度的影响--兼论灰色系统理论的应用

在实验室用试验立磨对同一批熟料进行粉磨,制备出不同比表面积的水泥.采用激光粒度仪精确测定各水泥试样的颗粒分布.以灰色系统理论分析水泥颗粒分布对水泥强度的影响.通过分析发现在对原始试验数据进行适当取舍后,所得关联度结论更符合水泥水化理论.     

熟料粒度分布与矿物组成对硅酸盐水泥抗裂性的影响

为系统探究熟料粒度分布和矿物组成对硅酸盐水泥抗裂性的影响,研究了熟料粒度分布和矿物组成对水泥基材料工作性能、水化性能、力学性能、干燥收缩性能和抗裂性能的影响。结果表明：随着水泥熟料细颗粒含量的提高,水泥标准稠度用水量增大,凝结时间缩短,失水率减少,干燥收缩增大,开裂风险增大;随着水泥熟料中C₃S含量的减少,C₂S含量的增加,水泥标准稠度用水量变化不明显,凝结时间延长,早期水化活性和强度降低,后期强度能稳定增长,失水率增大,干燥收缩减小;制备抗裂硅酸盐水泥时,建议水泥熟料粒度分布特征粒径D₁₀控制在5～7μm之间,D₉₀在45μm左右,C₃S含量在40%～60%,C₂S含量在10%～30%。     

Packing effect and pozzolanic reaction of fly ash in mortar

This research is to study the effect of particle size of fly ash on packing effect and pozzolanic reaction of mortar when 20% of fly ash is used to replace Portland cement type I. Both effects can be determined by using fly ash and insoluble material which have almost the same particle size to replace Portland cement type I. Normally, the compressive strength of fly ash mortar is contributed from hydration reaction, packing effect, and pozzolanic reaction. For mortar mixed with insoluble material, the compressive strength is due to hydration reaction and packing effect. Thus, compressive strength due to pozzolanic reaction can be determined from the difference in compressive strength between fly ash mortar and insoluble material mortar. The results show that the strength activity index of fly ash mortar depends on the median particle size of fly ash and curing ages of mortar samples. At early ages, the strength activity index of fly ash mortar due to packing effect is higher than that due to pozzolanic reaction. At the ages of 3 to 90 days, the difference in strength activity index due to packing effect of fly ashes with median particle size of 2.7 and 160 μm is almost constant about 22% of the strength of standard mortar (STD). The differences in strength activity index due to pozzolanic reaction of fly ashes with median particle size of 2.7 and 160 μm are 3%, 20%, and 27%, respectively, at the ages of 3, 28, and 90 days.     

Mechanical behaviour of various mortars made by combined fly ash and limestone in Moroccan Portland cement

Physico-chemical properties and mechanical behaviour of ternary cements made by Portland cement, fly ash and limestone are studied. The mixtures at various compositions of clinker, gypsum fly ash and limestone are intimately ground and compared to other compositions without fly ash. Blended fly ash cements are also studied. The results show that fly ash acts as grinding agent by reducing the required time to obtain the same percentage of particles retained on a 80-μm sieve as the standard cement. Fly ash cements lead to an important extension of setting time than limestone cements. The replacement of clinker by limestone gives better mechanical strengths than the mixtures containing fly ash at early days; after 28 days, the cements prepared by incorporation of fly ash gain an important strength. From mechanical point of view, an optima dosage was obtained at 77% clinker, 2% gypsum, 7.5% fly ash and 13% limestone composition.     

Properties of fly ash-modified cement mortar-aggregate interfaces

This paper investigates the effect of fly ash on strength and fracture properties of the interfaces between the cement mortar and aggregates. The mortars were prepared at a water-to-binder ratio of 0.3, with fly ash replacements from 15 to 55%. Notched mortar beams were tested to determine the flexural strength, fracture toughness, and fracture energy of the plain cement and fly-ash modified cement mortars. Another set of notched beams with mortar-aggregate interface above the notch was tested to determine the flexural strength, fracture toughness, and fracture energy of the interface. Mortar-aggregate interface cubes were tested to determine the splitting strength of the interface. It was found that a 15% fly ash replacement increased the interfacial bond strength and fracture toughness. Fly ash replacements at the levels of 45 and 55% reduced the interfacial bond strength and fracture toughness at 28 days, but recovered almost all the reduction at 90 days. Fly ash replacement at all levels studied increased the interfacial fracture energy. Fly ash contributed to the interfacial properties mainly through the pozzolanic effect. For higher percentages of replacement, the development of interfacial bond strength initially fell behind the development of compressive strength. But at later ages, the former surpassed the latter. Strengthening of the interfaces leads to higher long-term strength increases and excellent durability for high-volume fly ash concrete.     

玻璃粉粒度对复合胶凝材料性能的影响

用激光粒度分析仪测定不同细度的玻璃粉粒度分布,以灰色关联方法( GIA)和扫描电子显微镜( SEM)研究了玻璃粉粒度对复合胶凝材料性能的影响。研究结果表明,玻璃粉中10μm以下的颗粒关联性均为正,说明这些颗粒对复合胶凝材料强度发展有积极贡献,其中以5~10μm的关联度为最大;而?45μm的颗粒呈负关联,其火山灰活性没有得到充分发挥;玻璃粉经适当物理磨细(35 min)后,能更有效地分散到复合胶凝材料的孔隙中,使复合胶凝材料的结构更加密实,从而提高了复合胶凝材料的抗压强度。     

分选与磨细粉煤灰对水泥胶砂性能的影响

研究了分选与磨细粉煤灰的颗粒分布与形貌的差异及对水泥胶砂性能的影响。研究结果表明:当勃氏比表面积相近,磨细粉煤灰的中位粒径大于分选细粉煤灰,其圆珠状颗粒较少,表面较为粗糙。在相同水胶比的条件下,掺分选粗粉煤灰的水泥胶砂流动度及强度均低;分选粗粉煤灰磨细后,不仅减少了颗粒的粘连,增加了比表面积,而且提高了粉煤灰的反应活性和水泥胶砂流动度及强度,虽其水泥胶砂流动度仍小于掺分选细粉煤灰的水泥,3d水泥胶砂强度也略低,但其28d水泥胶砂强度略高于掺分选细粉煤灰的水泥;在相同水泥胶砂流动度的条件下,掺磨细粉煤灰配制的水泥胶砂3d强度低于掺分选细粉煤灰的水泥,但随着水化龄期的增长,其差距逐步缩小,至60d时可超过后者。     

公路粉煤灰水泥的研制（一）

文中研究了熟料掺量、复合激发剂、石膏掺量、水泥颗粒粒度对公路粉煤灰水泥的影响.获得了公路粉煤灰水泥的最佳配料方案和工艺参数.与粉煤灰硅酸盐水泥性能相比,公路粉煤灰水泥早期强度略低于粉煤灰硅酸盐水泥,凝结时间较长,但其7d～28d水化龄期内的强度增长率较高,28d强度已赶上或超过粉煤灰硅酸盐水泥,胶砂流动度好.     

生物质灰对水泥硬化浆体抗压强度影响的试验研究

对比研究了生物质灰与普通粉煤灰在粒度分布、颗粒形态、化学组成、活性指数等方面的不同,并开展了不同掺量生物质灰对水泥硬化浆体抗压强度的影响研究.结果表明:生物质灰颗粒形状不规则、平均粒径及粒径分布范围较大,具有特有的细长纤维状颗粒,且其活性组分Al2O3不足普通粉煤灰的三分之一;生物质灰的火山灰活性小于普通粉煤灰;相同掺量下,生物质灰-水泥复合胶砂各龄期的抗压强度均小于普通粉煤灰-水泥复合胶砂,生物质灰掺量越大,复合胶砂的强度相比纯水泥组下降程度越大;与普通粉煤灰相比,掺加生物质灰的硬化水泥浆体微观结构更为疏松多孔,特别是其特有的细长纤维状颗粒的存在.     

熟料细度对粉煤灰水泥浆体强度和自收缩的影响

通过实验室球磨机制备出比表面积分别为280m2/kg、370m2/kg和670m2/kg的3种水泥熟料,与不同掺量的粉煤灰配制成不同颗粒级配的粉煤灰水泥,并测试了粉煤灰水泥浆体的抗压强度、自收缩、孔隙率和显微结构。结果表明：提高熟料细度能在很大程度上降低粉煤灰水泥浆体的孔隙率并提高复合水泥浆体早期抗压强度;粉煤灰的掺入降低了水泥体系的自收缩,提高了粉煤灰水泥浆体的体积稳定性;粉煤灰水泥浆体背散射图像表明,提高熟料细度可显著减少粉煤灰水泥浆体中未水化的水泥颗粒含量,并在一定程度上减少未水化粉煤灰颗粒含量。     

粉煤灰渣替代细骨料对砂浆混凝土强度及抗冻性影响

通过筛分和破碎两种方式分别获得粒径区间为0.6~1.18 mm、0.3~0.6 mm的粉煤灰渣,并用其等体积替代对应粒径区间的细骨料,分析粉煤灰渣对砂浆工作性和强度的影响,探究粉煤灰渣的最优替代粒径区间。结合扫描电镜(SEM)、能谱分析(EDS)等方法分析了粉煤灰渣替代细骨料后砂浆试件的强度变化机理。基于砂浆最优替代粒径区间结果,验证了砂浆混凝土试件的强度和抗冻性。研究结果表明:分别以筛分方式和破碎方式得到的0.3~0.6 mm粒径区间粉煤灰渣替代对应区间细骨料后,其砂浆试件强度均与基准组(未替代)基本一致;而以筛分方式得到的0.3~0.6 mm粒径区间粉煤灰渣替代对应区间细骨料后,其混凝土试件强度和抗冻性与基准组基本一致。在水泥提供的氢氧化钙环境下粉煤灰渣表面生成水化硅酸钙,从而增加了水泥和粉煤灰渣界面胶结强度,强化水泥与粉煤灰渣界面区域,凹凸不平的粉煤灰渣表面与水泥浆咬合嵌锁,保证了试件的强度。     

The influence of air content by assessing the pozzolanic activity of fly ash by strength testing

The pozzolanic activity of fly ash and natural pozzolans are generally assessed by a compressive strength test with Portland cement in a mortar. A test mix in which part of the Portland cement is replaced by fly ash is compared with a control mix with pure Portland cement. When testing cement according to such procedures the influence of varying air contents in the test mortars can be comparable to that of other factors, hence complicating the interpretation of results. Fly ash seems to affect the air void content in mortar in two ways: By a direct contribution from hollow or porous particles in the fly ash and by reducing the amount of entrained air, an effect which is apparently caused by the residual carbon present in the fly ash.These aspects are elucidated by examples from laboratory experiments with fly ash.