Utilization of fly ash coming from a CFBC boiler co-firing coal and petroleum coke in Portland cement

Fly ash coming from a circulating fluidized bed combustion (CFBC) boiler co-firing coal and petroleum coke (CFBC fly ash) is very different from coal ash from traditional pulverized fuel firing due to many differences in their combustion processes, and thus they have different effects on the properties of Portland cement. The influences of CFBC fly ash on the strength, setting time, volume stability, water requirement for normal consistency, and hydration products of Portland cement were investigated. The results showed that CFBC fly ash had a little effect on the strength of the Portland cement when its content was below 20%, but the strength decreased significantly if the ash content was over 20%. The water requirement for normal consistency of cement increased from 1.8% to 3.2% (absolute increment value) with an addition of 10% CFBC fly ash; and the free lime (f-CaO) content of CFBC fly ash affected the value of increasing. The setting time decreased with an increase of CFBC fly ash content. The volume stability of the cement was qualified even when the content of SO₃ and f-CaO reached 4.48% and 3.0% in cement, respectively. The main hydration productions of cement with CFBC fly ash were C-S-H (hydrated calcium silicate), AFt (ettringite), and portlandite.     

石灰-水泥-粉煤灰改性磷石膏对水泥物理性能的影响研究

采用石灰、水泥、粉煤灰对磷石膏进行改性处理,测定了改性磷石膏中硫酸根的溶解性能,对比了原状磷石膏与改性磷石膏对水泥物理性能的影响,并结合X射线衍射（XRD）和扫描电镜（SEM）分析了改性前后磷石膏对水泥不同龄期水化产物的影响。结果表明：随着石灰掺量的增加改性磷石膏的pH逐渐增大,当石灰掺量为4%（质量分数）时磷石膏的pH达到12.22,此时磷石膏中的可溶性磷、氟转化成难溶性的磷酸盐、氟化钙;随着水泥和粉煤灰掺量的增加,改性磷石膏的溶解性能呈现降低趋势。当石灰掺量为4%、水泥掺量为10%（质量分数）、粉煤灰掺量为10%（质量分数）时,改性磷石膏经过7 d养护在水中浸泡8 h所得滤液中硫酸根的质量浓度为0.30 g/L,比未改性磷石膏在水中浸泡8 h所得滤液中硫酸根的质量浓度降低了81.8%。与掺加未改性磷石膏的水泥浆体相比,掺加改性磷石膏的水泥浆体的水灰质量比由0.41降低到0.38、初凝时间和终凝时间分别缩短34.6%和27.2%、28 d抗压强度提高21.1%。石灰、水泥、粉煤灰改性处理磷石膏后,生成的水化硅酸钙和钙矾石等水硬性产物包裹在石膏颗粒表面,使硫酸根在水中的溶出速率降低,减少了对水泥中铝酸三钙的影响,使得硬化体内部结构变得致密、力学性能显著提高。     

Influence of fly ash and its mean particle size on certain engineering properties of cement composite mortars

An experimental investigation on the effects of incorporating large volumes of fly ash on the early engineering properties and long-term strength of masonry mortars is reported. The effect of fly ash and its mean particle size (PD) on the variation of workability and strength has been studied. It was found that fly ash and its mean particle size play a very significant role on the strength of masonry mortars. It has been observed that the early-term strength, except the mortars incorporating coarse fly ash (CFA), was slightly influenced by the replacement with fly ash. The long-term strength (both the bond strength and the compressive strength) will significantly increase, especially for the bond strength of mortars incorporating coarse fly ash. It was also found that the bond strength significantly increased as the mean particle size of fly ash decreases after 28 days curing. However, the 7-day strength was little influenced by fly ash particle size. The fluidity of composite mortar enhanced due to replace cement and lime with fly ash, and the mean PD of fly ash significantly influenced the workability.     

粉煤灰的激发形式及其对混凝土性能的影响

采用硫酸盐单掺、硫酸盐和熟石灰复掺,磨细、非磨细等低等级粉煤灰的活性激发手段,取水胶比为0.25和0.30,分别对不同掺量粉煤灰的混凝土进行对比试验,研究激发方式、粉煤灰掺量与高性能混凝土强度的关系。研究表明:硫酸盐和熟石灰与粉煤灰共同磨细的激发方式,对粉煤灰火山灰活性激发效果最明显,能配制得到粉煤灰掺量达50%～70%,强度为80MPa的高强混凝土;不磨细处理时,单掺和复掺激发剂对混凝土强度影响效果相差不大。     

Fire resistance of fired clay bricks-fly ash composite cement pastes

This work aims to study the effect of substitution of fly ash for homra on the hydration properties of composite cement pastes. The composite cements are composed of constant proportion of OPC (80%) with variable amounts of fly ash and homra. The addition of fly ash accelerates the initial and final sitting time, whereas the free lime and combined water contents decrease with fly ash content. The fly ash acts as nucleation sites which may accelerate the rate of formation of hydration products which fill some of the pores of the cement pastes. The fire resistance of composite cement pastes was evaluated after firing at 250, 450, 600, 800 °C with rate of firing 5 °C/min with soaking time for 2 h. The physico-mechanical properties such as bulk density and compressive strength were determined at each firing temperature. Moreover, the phase composition, free lime and microstructure for some selected samples were investigated. It can be concluded that the pozzolanic cement with 20 wt% fly ash can be used as fire resisting cement.     

固化废弃软黏土的强度特性及水稳定性研究

为了提高水泥和粉煤灰固化高含水率废弃软黏土的固化效果,选取水玻璃作为外加剂,吸水性强的生石灰作为分散剂,采用无侧限抗压强度试验、X 射线衍射、扫描电镜试验研究掺量与龄期对固化软黏土水稳定性和强度特性的影响。试验结果表明,3%(质量分数)的水泥、7%(质量分数)的粉煤灰、2%(质量分数)的生石灰与2%(质量分数)的水玻璃复合时能较好提高高含水率软黏土固化后的强度和水稳定性,其强度能达到水泥粉煤灰类基底层最低强度(1 MPa)。在水泥、粉煤灰和水玻璃质量掺量相同情况下,生石灰质量掺入比由0%增加至2%,其强度增大约375 kPa,且有利于后续固化剂的均匀搅拌,说明生石灰的减水和分散效应在固化土中起主导作用。此外,扫描电镜结果显示加入复合固化剂后大集聚体消失,产生大量的片状结构,大孔隙被填充,土体的强度也随之提高。     

外加剂对二灰稳定尾矿料混合料早期强度增长的影响与机理分析

对二灰 (石灰与粉煤灰 )稳定尾矿料混合料在不同外加剂掺量下的早期强度增长规律进行系统研究 ,对其早期强度增长机理进行分析探讨。研究表明 ,二灰稳定尾矿料混合料主要是通过Ca(OH) 2 与粉煤灰中的活性组分反应生成胶凝成分把尾矿料胶结起来形成强度 ,在石灰 -粉煤灰 -尾矿料反应体系中 ,掺入外加剂的主要目的在于激发粉煤灰的早期活性并促进混合料早期强度增长 ,同时外加剂也参与反应生成具有胶凝性的成分 ,并起到胶结作用 ,进一步密实混合料结构     

无机盐类早强剂对水泥性能影响的研究

以熟石灰和硫酸钠为主要原料,经配料、均化制备出早强剂。在粉煤灰水泥和普通水泥中分别加入等量早强剂制成试样,测试其不同龄期的抗压和抗折强度,并进行热重分析和红外光谱分析。通过宏观与微观分析比较了早强剂对粉煤灰水泥和普通水泥性能的影响。实验结果表明,相同早强剂掺量情况下,普通水泥的早期强度明显高于粉煤灰水泥。早强剂促进了粉煤灰水泥中熟料矿物的水化,对粉煤灰组分没有明显作用。     

Activation of fly ash cementitious systems in the presence of quicklime: Part I. Compressive strength and pozzolanic reaction rate

In the first part of this study, the effect of industrially produced quicklime on the strength development and pozzolanic reaction rates of different fly ash/cement (FC) systems was investigated. Two high calcium fly ashes, diversified on their active silica and calcium oxide contents, and one with moderate calcium content were used. Strength development, hydration evolution, and pozzolanic reaction rates of the quicklime-fly ash-cement (QFC) systems were monitored and presented. Moreover, new efficiency factors were calculated for the activated systems in an attempt to optimize the quicklime addition in each case, whilst correlations were attempted between the nonevaporable water contents (W_n) and the cementitious efficiency factor (k values) of the activated systems. The addition of quicklime increased both the early and later strengths of the high-calcium fly ash specimens. For the two high-lime ashes tested, a 3% addition of quicklime was found to be the optimum dosage both for short and longer curing periods. It is possible that such an offer of lime fully employed the available silica from the ashes to form additional cementitious compounds, principally pozzolanic C-S-H. In the case of lower-lime fly ash, a small quantity of added lime (5%) was found to be effective only during the initial stages of the hardening process. When quicklime additions increased, no accelerating effect was detected, as a result of the diminished proportion of soluble silica in the pore solution. Identification of the generated hydration products, porosity of the activated mixtures and examination of their microstructure will be presented in Part II of the study.     

软测量技术在电站锅炉优化燃烧上的应用

针对阜新电厂200 MW机组燃煤锅炉进行了多工况热态测试,获得了飞灰含碳量的现场数据样本,运用Back Propagation(BP)神经网络和Levenberg Marquardt(LM)算法建立了电站锅炉飞灰含碳量的软测量模型,并构造了飞灰含碳量的测量系统. 在此基础上开发了电站锅炉燃烧优化系统,实现了阜新电厂200 MW机组锅炉燃烧优化控制.     

Ash content for optimum strength of foamed concrete

A study has been undertaken into the properties of foamed concrete in which large volumes of cement (up to 75 wt.%) have been replaced with both classified and unclassified fly ash. This fourth paper in the series examines the effects of increasing the levels of ash on the compressive strength of the concrete. Twenty-seven different mixtures were cast with varying ash contents and densities, and the results used to develop models that have been used to predict the compressive strength of the foamed concrete. The output from the models predicts an optimum ash content for maximum strength at a given porosity and age and shows that the optimum value increases with increasing age.     

利用高钙粉煤灰生产膨胀水泥的初步研究

通过对掺加游离氧化钙含量不同的高钙粉煤灰水泥的研究,表明掺入合适的添加物不仅可提高该水泥的强度,而且可调节水泥硬化浆体的膨胀值,使掺高钙粉煤灰水泥的基本性能满足一些膨胀水泥的技术指标,可利用高钙粉煤灰生产膨胀水泥。     

粉煤灰制备多孔水处理材料的试验研究

针对粉煤灰粒度细小带来的分离困难等问题,研究了一种粉煤灰制备多孔水处理材料的方法。对成型过程中石灰添加量、铝粉添加量、粉煤灰粒度以及搅拌速度等影响因素进行了研究。分别考察了成型试件的吸水率、COD去除率、氨氮去除率、抗压强度、干体积密度以及抗冻性能。结果表明最佳制备条件为：粉煤灰：石灰：石膏：水泥：铝粉：水：十二烷基苯磺酸钠为34．5：10．5：2：4：0．056：35：0．15,粉煤灰、石灰、石膏、水泥粒度为O．075mm,搅拌速度为400r／min。制得的多孔试件各项指标为：于体积密度约为540-590kg／m^3,抗压强度为0．7～0．9MPa,吸水率为70％-80％,COD去除率为22％左右,氨氮去除率为38％左右,冻融后质量损失为2．5％左右,冻后抗压强度为0．5MPa,均达到较优水平,是一种很好的水处理材料。     

偏高岭土高性能混凝土抗压强度预测研究

以水胶比、用水量、砂率、水泥强度、水泥用量以及偏高岭土、矿粉和粉煤灰用量为输入向量,采用SPSS回归方程分析和基于Levenberg-Marquart算法的BP神经元网络预测模型对偏高岭土高性能混凝土的抗压强度进行了预测研究,并与试验值进行了对比.结果表明:与SPSS回归方程分析预测结果相比,BP神经元网络预测值与实测值线性拟合度高,拟合值为0.997,两者之比的平均值和标准差分别为0.999和0.010,网络预测最大相对误差不超过2.1%,模型预测精度高,结果可靠,为偏高岭土高性能混凝土的抗压强度预测提供了指导依据.     

季冻区粉煤灰加固路基土力学性能试验研究

为探究冻融循环作用对粉煤灰加固路基土力学性能影响,对冻融循环次数、含水率、粉煤灰掺量不同的盐渍土开展无侧限抗压试验和三轴剪切试验,研究冻融循环后土体的应力-应变曲线、无侧限抗压强度、黏聚力和内摩擦角的变化情况。使用Design-Expert 8.0软件,研究冻融循环次数、粉煤灰掺量、含水率及各因素交互作用对盐渍土力学性质影响的显著性程度。结果表明:多次冻融循环后,盐渍土无侧限抗压强度、黏聚力和内摩擦角均有下降,经历1~7次冻融循环时,土体各力学参数下降速率较快;随着粉煤灰掺量的增加,盐渍土的内摩擦角、黏聚力、无侧限抗压强度和抗剪强度呈现出先升高后下降的变化趋势。基于显著性分析理论,冻融循环次数与含水率的交互作用对盐渍土无侧限抗压强度和黏聚力的影响较为显著,粉煤灰掺量与冻融循环次数的交互作用仅对无侧限抗压强度影响较为显著。为提高路基土强度及抗冻融的能力,加快粉煤灰综合利用进度,根据软件和公式模拟结果,推荐在路基土中依据质量比掺加15%粉煤灰,并将经历7次冻融循环后压实盐渍土的力学指标作为工程设计参考值。     

粉煤灰对脱硫石膏-矿渣-粉煤灰复合胶凝材料力学性能的影响

通过研究粉煤灰自身在硫酸盐和石灰双重激发下产生的活性、粉煤灰的碱性以及颗粒Zeta（电位）等,分析不同粉煤灰对脱硫石膏-矿渣-粉煤灰复合胶凝材料力学性能的影响。结果表明,粉煤灰的种类对复合胶凝材料的力学性能影响很大,粉煤灰本身活性的差异不是造成这种影响的主要原因,其主要原因是粉煤灰对矿渣粉的激发程度。粉煤灰的碱性对矿渣粉的激发影响很大,对于普通含钙粉煤灰,碱性越强,激发越好,复合胶凝材料力学性能越好。矿渣粉颗粒的Zeta电位为负,因此粉煤灰颗粒表面的正电荷密度过高,不利于矿渣粉活性的激发。     

粉煤灰混凝土抗硫酸盐侵蚀性能(英文)

为了探究掺粉煤灰混凝土的抗硫酸盐侵蚀性能,固定水灰比,用不同种类的粉煤灰在20℃条件下制备混凝土试样。在8℃或20℃的条件下分别水养14、28 d和90 d后,试样在20℃和8℃的条件下被置于SO24-浓度为16 g/L的硫酸钠溶液中。试样的抗硫酸盐侵蚀性能通过目视观察和长度变化来评价。研究了粉煤灰种类、先期养护时间和温度对粉煤灰混凝土的抗硫酸盐侵蚀性能的影响。结果表明：石灰含量,硫酸盐浓度和玻璃相中的碱含量是影响粉煤灰混凝土抗硫酸盐侵蚀性能的主要因素,并且提出了粉煤灰的组成影响粉煤灰混凝土抗硫酸盐侵蚀性的机理。     

利用金陵热电厂脱硫灰制备双免砖的研究

以金陵热电厂所排脱硫灰为主要原料,进行了免烧免蒸砖的研究。采用正交试验方法,设计了脱硫灰、水泥、集料、石膏、石灰的不同配比。试验结果表明,在配比为水泥8％、集料25％、石灰10％、石膏5％、粉煤灰52％时,生产的免烧砖强度最高。同时还研究了不同原材料对免烧砖强度的影响。     

利用多种工业废渣复配制备胶凝材料的实验研究

选择煤矸石、镁渣、粉煤灰等工业废渣作为主体原料,对原料进行粉磨筛分等处理;利用荧光分析仪和X 衍射仪检测原料的组成;设计了3组共计9个配方：煤矸石底渣+镁渣+熟料+石膏组3个、煤矸石底渣+粉煤灰+生石灰+石膏组3个、煤矸石底渣+粉煤灰+生石灰组3个;测定9个配方胶凝材料的强度、凝结时间、标准稠度、安定性等物理性能,结果表明：在生石灰、石膏双激发作用下,煤矸石灰渣、粉煤灰的水化硬化程度较高,制得的胶凝材料强度最高、28 d抗折强度可达8.2 MPa、抗压强度可达42.4 MPa。实验得到此方案的最佳配比：m（煤矸石灰渣）∶m（粉煤灰）∶m（生石灰）∶m（石膏）=15∶30∶45∶10。     

Effects of fly ash in composites fabricated by injection molding

In this study, the effects of fly ash in composites fabricated by injection molding are examined. Taguchi design of experiment was first utilized to estimate the effects different injection molding conditions and content ratios of fly ash have on a linear low‐density polyethylene (LLDPE)‐fly ash composite. The results reveal that the content of fly ash is highly significant and contributive to the shrinkage ratio and bending strength. For these reasons, LLDPE and polypropylene (PP) composites with different size particles of fly ash were fabricated and the mechanical properties were investigated. The particle size was changed by grinding fly ash with a planetarium ball mill. The shrinkage ratio, bending strength and flexural modulus of LLDPE composites containing raw fly ash were found to improve. The shrinkage ratio and flexural modulus of PP composites containing ground fly ash were also found to improve. Homogenization analysis using the finite element method was then used to calculate the Von Mises stress distributions and homogenized elastic matrix of PP composites containing ground fly ash. The homogenized elastic matrix was used to validate the experimental flexural modulus. The results show that the homogenized elastic matrix is in good agreement with the experimental flexural modulus. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers