超细粉煤灰水泥基复合胶凝材料的水化性能及应用

通过水泥胶砂流动性、强度及化学结合水量试验,研究了超细粉煤灰(UFA)水泥基复合胶凝材料的水化性能.结果表明,UFA有减水增强和密实填充效果;以25%的UFA等量取代水泥,成功配制了铁路预应力钢筋混凝土试验梁工程的高性能混凝土.     

不同细度超细粉煤灰对砂浆及混凝土性能影响的研究

研究了经超细粉磨制备的三种不同细度的超细粉煤灰的基本性能,以及掺入这三种不同细度超细粉煤灰的水泥胶砂和混凝土试样的力学性能和混凝土拌合物的工作性能。结果表明,超细粉煤灰的活性随其细度的增加而提高。掺入超细粉煤灰可以有效改善混凝土拌合物的工作性能、胶砂试件和混凝土试件的力学性能,且超细粉煤灰的细度越细改善作用越明显。不使用硅灰,仅用超细粉煤灰和减水剂也可以配制出C80的高强混凝土。微观孔结构分析表明,掺入平均粒径为4μm的超细粉煤灰的混凝土小于20 nm的无害孔的孔体积明显大于掺入其他两种超细粉煤灰（2μm、6μm）的混凝土,这与CUFA4试样力学性能最佳的宏观试验结果一致。     

粉煤灰微波改性及其对含铬废水的吸附性能

将取自于西安市西郊热电厂的原粉煤灰(FA)球磨5h得到超细粉煤灰(UFA),再经过微波辐照处理得到微波辐照改性超细粉煤灰(MFA),并研究其对含铬废水的吸附性能.动力学研究结果表明,改性粉煤灰对Cr(VI)的吸附符合二级吸附动力学模型,通过模型计算出的FA,UFA和MFA的二级吸附速率常数(k2)分别为2.45×10-2 ,3.88×10-2 和5.14×10-2g·mg-1·min-1; 热力学研究结果表明,吸附过程可以用Langmuir方程描述.     

超细粉煤灰高性能混凝土耐久性试验研究

研究了由电收尘气流分选工艺收集的超细粉煤灰(UFA)对高性能混凝土耐久性能的影响。结果表明:超细粉煤灰提高了高性能混凝土的抗冻性和抗渗性,掺UFAI(适用于C50～C70的高温性能混凝土工程的超细粉煤灰)的高性能混凝土其单位面积磨损量均有不同程度的降低并具有优良的护筋性,掺粉煤灰可以改善高性能混凝土的抗硫酸盐侵蚀性,尤其是对混凝土的早期强度和干缩性能具有显著的改善效果。     

多元凝胶紧密堆积对活性粉末混凝土的影响

讨论了C(水泥)+UPFA(超细粉煤灰)、C+SF(硅灰)二元和C+UPFA+SF三元胶凝材料体系中,新拌浆体的黏度、流动度与浆体的相对密实度的关系,以及相对密实度和流动度对活性粉末混凝土RPC强度的影响.实验结果表明:(1)双掺硅灰和超细粉煤灰,随活性粉末掺量的增加,新拌浆体的黏度增加,流动性下降,相对密实度提高;(2)双掺硅灰和超细粉煤灰的RPC强度远高于单掺硅灰时的强度;(3)RPC强度与体系中胶凝材料的相对密实度和流动度有关,复掺硅灰和超细粉煤灰,当密实度为0.669,流动度为182mm时,其RPC的7d抗压强度高迭150.4MPa.     

磨细粉煤灰与起细粉煤灰的性能对比试验研究

比较了在同等细度下,用普通球磨机粉磨的磨细粉煤灰与电收尘气流分选工艺收集的超细粉煤灰的物理、化学性质,以及力学性能。试验结果表明,磨细粉煤灰的性能优于超细粉煤灰,进而确定了激发剂的最佳掺量。     

粉煤灰基成型吸附剂的制备及其对亚甲基蓝的吸附性能

为了增加粉煤灰的反应活性,将原料粉煤灰(raw fly ash,RFA)进行超细球磨得到超细粉煤灰(ultra-fine fly ash,UFA),将超细粉煤灰与NaOH溶液反应后挤出成型烘干,得到超细粉煤灰基成型吸附剂(ulWa-finc forming fly ash.based adsorbent,UFFA),通过X射线衍射和扫描电子显微镜对其进行表征.研究了RFA,UFA和UFFA对亚甲基蓝(methylene blue,MB)的吸附性能.结果表明:UFFA的吸附性能最好,其次为UFA,RFA最差.UFFA对MB的吸附过程符合二级吸附动力学模型,UFFA对MB的吸附过程由颗粒内扩散过程控制.热力学研究表明:UFFA对MB的吸附符合Fromdlich吸附等温式;UFFA对MB吸附热力学参数△G小于0,表明吸附过程是白发进行的;△H为-13.84kJ/mol,表明吸附是放热过程.     

大掺量超细粉煤灰高强混凝土研究

本论文研究了不同掺量和不同平均粒径粉煤灰掺入对高强混凝土工作性能和力学性能的影响,并借助SEM、XRD,探讨了超细粉煤灰的掺入对混凝土微观结构及水化产物的影响.结果表明:粉煤灰细度和掺量对高强混凝土力学性能有显著的影响.将粉煤灰超细粉磨至足够细度,可在释放粉煤灰微珠内部包裹更细小球形微珠的同时,减弱非球形颗粒的形貌影响,改善混凝土拌合物的和易性.超细粉磨作用使粉煤灰比表面积大大增加,有助于粉煤灰在早期更好地发挥微集料效应,后期更好地发挥火山灰效应,从而使混凝土在早期和后期的抗压强度都显著增强.     

超细粉煤灰改性再生骨料混凝土力学及抗冻性能研究

为研究不同掺量超细粉煤灰改性再生混凝土的性能,借助室内试验的手段测试了不同掺量超细粉煤灰对再生混凝土的力学及抗冻性能的影响.研究结果表明:超细粉煤灰的掺入能提高再生混凝土的后期抗压强度,当超细粉煤灰掺量为15％时,试件在28 d和56 d时,其再生混凝土抗压强度比基准混凝土分别提高了10.08％和8.26％;适量的超细...     

粉煤灰超细改性及对Cr6+的吸附热力学

将3个不同电厂的粉煤灰球磨后得到超细粉煤灰,选择HCI、H2SO4、NaOH、Ca(OH)2和Na2CO3等对超细粉煤灰进行化学改性.结果表明,采用Ca(OH)2改性效果最好,经过Ca(OH)2改性的3种超细粉黻对Cr6 的去除率提高2.01~2.44倍.Ca(OH)2改性超细粉煤灰对Cr6 的吸附热力学研究表明,3种改性超细粉煤灰在25℃、35℃和45℃对cr6 的吸附符合Langmuir吸附等温式,吸附过程为自发、放热过程.同时,分析了Ca(OH)2改,性超细粉煤灰的机理,研究了吸附饱和改性超细粉煤灰的脱附再生方法.     

Influence of steam curing on the compressive strength of concrete containing supplementary cementing materials

Heat treatment is widely used to accelerate the strength-gaining rate of concrete. In general, the ultimate strengths of the heated-treated concrete are lower than those of the standard cured specimens. When ultrafine fly ash (UFA) is included in concrete, the pozzolanic reaction is accelerated through the heat treatment. Sometimes, various chemical activators were used to activate the reactivity of fly ash. In the current study, UFA and slag were used as a replacement for cement, steam curing and chemical activators were used to accelerate hydration of cement and fly ash, and then compared with moist curing. This paper presents the influence of steam curing on the compressive strength of concrete containing UFA with or without slag. The experimental results indicated that the concrete containing UFA has low early strength after 13-h steam curing and that the difference between the 28-day compressive strength of concrete through 13-h steam curing and that of moist-cured concrete is large, but the concrete with UFA and CaSO₄ or Ca(OH)₂ has a high early strength, thus, the reactivity of fly ash must be accelerated. Concrete containing UFA and ground slag was prepared, whose compressive strengths were improved.     

Ultrafine fly ash as a reinforcing filler in poly(lactic acid) matrix

Fly ash, inexpensive and not eco‐friendly material, is the residue from the coal burning in thermal power stations. If ways can be found to use it, it will facilitate applications for the ash materials and simultaneously reduce the pollution. In this study, silane‐grafted ultrafine fly ash (S‐UFA) was used as a reinforcing filler in poly(lactic acid) (PLA) to prepare a series of PLA/S‐UFA composites. The tensile strength of PLA/S‐UFA composites increases with the increase of S‐UFA content when less than 20 wt %; after a loading fraction greater than 30 wt %, the tensile strength of the composites decreases with the increasing S‐UFA weight fraction. The morphology of PLA/S‐UFA composites was observed by scanning electron microscope (SEM). X‐ray diffraction (XRD) analysis was applied to investigate the crystal structure of S‐UFA and the composites. The thermal properties of these composites were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TGA results showed that the thermal stability of PLA/S‐UFA composites slightly decreased with the increasing S‐UFA loading fraction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43716.     

低水胶比下超细粉煤灰对不同细度硅酸盐水泥水化历程的影响

从强度、结合水、粉煤灰反应程度、SEM分析及孔隙溶液碱度等方面,研究了低水胶比下超细Ⅱ级粉煤灰对不同细度硅酸盐水泥水化历程的影响。研究结果表明,水泥细度从4500cm2/g提高到5500cm2/g,对纯水泥水化过程影响不大。但当该高细度水泥与超细II级粉煤灰复合时,则对水泥及粉煤灰的水化程度、水化产物特性、孔隙溶液碱度以及力学性能均影响较大;随粉煤灰掺量的增加,其影响程度呈由小变大再变小的趋势,粉煤灰掺量存在阈值,本试验中,阈值为30%。     

Influence of fly ash fineness on strength, drying shrinkage and sulfate resistance of blended cement mortar

In this paper, the influence of fineness of fly ash on water demand and some of the properties of hardened mortar are examined. In addition to the original fly ash (OFA), five different fineness values of fly ash were obtained by sieving and by using an air separator. Two sieves, Nos. 200 and 325, were used to obtain two lots of graded fine fly ash. For the classification using air separator, the OFA was separated into fine, medium and coarse portions. The fly ash dosage of 40% by weight of binder was used throughout the experiment. From the tests, it was found that the compressive strength of mortar depended on the fineness of fly ash. The strength of mortar containing fine fly ash was better than that of OFA mortar at all ages with the very fine fly ash giving the highest strength. The use of all fly ashes resulted in significant improvement in drying shrinkage with the coarse fly ash showing the least improvement owing primarily to the high water to binder ratio (W/B) of the mix. Significant improvement of resistance to sulfate expansion was obtained for all fineness values except for the coarse fly ash where greater expansion was observed. The resistance to sulfuric acid attack was also improved with the incorporation of all fly ashes. In this case the coarse fly ash gave the best performance with the lowest rate of the weight loss owing probably to the better bonding of the coarse fly ash particles to the cement matrix and less hydration products. It is suggested that the fine fly ash is more reactive and its use resulted in a denser cement matrix and better mechanical properties of mortar.     

大掺量粉煤灰对混凝土渗透性的影响

以粉煤灰代替３０％的水泥，在水胶比为０．３０、０．３３、０．３６及０．３９的情况下，分别试验了用水量及胶凝材料用量变化下混凝土的强度和渗透性。试验结果表明，与不掺粉煤灰的混凝土比较，掺粉煤灰混凝土的渗透性都明显降低，３０天龄期时最大可降低至５０．７％，７０天时可降低至２２．３％；为了获得较低的渗透性而采取较低的水胶比时，不掺粉煤灰的混凝土应用降低用水量的办法有利，掺粉煤灰的混凝土用提高总胶凝材料用量的办法更好     

粉煤灰水泥石碳化性能的化学分析

开发了一种自制测量装置。利用该装置,沿碳化深度方向,分层测定了碳化粉煤灰水泥石中CaCO3的含量。绘制了＂CaCO3含量–深度＂曲线。根据曲线特点,定义了完全碳化区、部分碳化区、未碳化区等概念和碳化程度、碳化速度等特征指标。研究了粉煤灰掺量、水胶比、龄期、养护条件、碳化前烘干处理、碳化时间、碳化湿度等对粉煤灰水泥石碳化性能的影响。结果表明：粉煤灰掺量越大,水胶比越高,龄期越短,养护环境越干燥,碳化前试件越干燥,粉煤灰水泥石的抗碳化性能越差;碳化时间越长,碳化湿度越低,粉煤灰水泥石的碳化程度越高;但碳化速度随碳化时间的增长而减慢。这些结论与文献报道的用其他方法得到的公认的结论一致。本方法还得到了更加深入的研究结果,即：粉煤灰掺量越大、粉煤灰水泥石中可碳化物质的相对含量越低;水胶比、龄期、养护条件、碳化时间、碳化湿度基本不改变粉煤灰水泥石中可碳化物质的相对含量;龄期、养护条件可改变未碳化粉煤灰水泥石中碳酸盐的相对含量。     

Properties of flash hydrated and agglomerated particles of CFB fly ashes

The fly ash (high carbon content and high unreacted CaO) recirculation in CFB is a typical method to improve the carbon burnout efficiency and the calcium utilization ratio. While the effectiveness of it is limited by the resident time and the reactivity of the re-injected fly ash particles. In the present research, an improved fly ash recirculation method is suggested in which the CFB fly ash is mixed with water or the mixtures of additives (such as waste water of paper mill, cement, sodium silicate, and carbide slag) and water in a blender. Then, this mixture is re-injected into the combustion chamber of CFB by a sludge pump. Because the temperature in CFB is higher, the fly ash was flash hydrated. At the same time, it was dehydrated and agglomerated. The size of agglomerates is bigger than that of original particle and their attrition rate is lower. Therefore the resident time of agglomerates is much longer than that of fine fly ash particles. The absorption of SO₂ is higher than that of original particles, too. This results in high carbon burnout efficiency. The hydrated lime also improves the calcium utilization.     

矿物掺合料对机制砂砂浆性能的影响

研究了在相同水灰比与流动度情况下,单掺或复掺硅灰及不同地区粉煤灰等矿物掺合料对机制砂砂浆流动性、强度的影响,并与标准砂砂浆进行了比较。结果表明、与标准砂相比,机制砂砂浆需水量大、保水性差、易泌水,但具有增强作用;硅灰引起机制砂砂浆流动性减小、减少泌水、增进强度。水灰比相同时,随掺量灰增大,机制砂砂浆流动性增大,不同龄期下砂浆抗压强度均下降。复掺硅灰与粉煤灰可提高机制砂的强度。上海与贵州两地的粉煤灰品质基本相同,对砂浆性能的影响也基本相同。     

矿物掺合料与水胶比对混凝土耐久性的影响研究

为研究矿物掺合料与水胶比对混凝土耐久性的影响,测试了不同混凝土的抗氯离子渗透性、抗冻性、耐磨性和抗硫酸盐侵蚀性能,采用灰色关联分析的方法,分析了矿物掺合料掺量、水胶比和混凝土耐久性之间的关联程度和关联极性。研究结果表明:粉煤灰和矿渣粉掺入会提高混凝土的抗氯离子渗透性,并存在最佳掺量,本文水胶比为0.38的混凝土,粉煤灰和矿渣粉掺量为15%时,混凝土的抗氯离子渗透性最高。矿物掺合料掺量与混凝土相对动弹性模量、耐磨度和抗硫酸盐侵蚀系数为正关联;水胶比增大会导致混凝土的抗氯离子渗透性降低,与混凝土相对动弹性模量、耐磨度和抗硫酸盐腐蚀系数为负关联。