The Electrical Resistivity Characteristics of Cement-Soil and Flyash-Lime-Soil

The electrical resistivity characteristics of cement soil and flyash lime soil are investigated in the laboratory and the field. It is shown that the electrical resistivities of the cement soil and flyash lime soil are sensitive to water content, degree of saturation and unconfined strength. The cement soil and flyash lime soil with higher water content, greater degree of saturation, lower unconfined strength has lower electrical resistivity. Electrical resistivity is also correlated with additives. Based on the tests, it is concluded that the electrical resistivity method is available for checking the effectiveness of the soil improvement by the cement soil and flyash lime soil mixing pile in terms of engineering practice.

Mechanism and Optimal Application of Chemical Additives for Accelerating Early Strength of Lime-flyash Stabilized Soils

To accelerate the early strength of lime-flyush stabilized soil for extending its further uses in highway and shortening highway constraction time, five kinds of chemical odditives were chosen on the basis of mechanism analysis of accelerating early strength in highway as a semi-rigid base materhd, and a series of experiments about the effect of differeat kinds of additives and quantity on the early strength of the stabilized soll were tested. The results show that chemical additives can efftciently improve the early strength of lime-flyush stabilized soil both the 7 d and 28d, and the optimum quantity for above chemical additive is 1.5%-2.5% approximately. Some suggestions for the practical construction were also proposed.

Flyash properties and analysis of flyash dam stability under seismic load

This article discusses the flyash mechanical properties and analyzes stability of two flyash dams under earthquake by finite element methods. It is studied whether the mixture of flyash and clay can be used as the fill for a dam located in an earthquake region.

Relation between Fluidability of Flyash Cement and Properties of Flyash Particles

A large amount of waste is produced by preparation plants. The properties of the waste vary depending on the mineralogical contents of the mother rock in which the coal is embedded. The waste quality depends on the method of mining and cleaning. The waste mainly consists of clays, quartz, carbonaceous materials, mica, pyrites, and so on. About 80% of coal-ash is now utilized and the remainder is disposed of at disposal sites. However, the life span of disposal sites is limited, and it is difficult to find new disposal sites. It is therefore requested that the percentage of utilized flyash be increased in all applicable fields in Japan. Thus, it is very desirable that cement supplemented with flyash be used as injection material for natural/artificial openings. With this perspective in mind, we attempt to clarify how much the size and shape of the flyash affects the properties of the injection mixture by way of an injection test.

Mechanical,Electrical and Thermal Properties of Nylon-66/Flyash Composites:Effect of Flyash

In the current study,the effect of flyash(FA)on the physic-mechanical,electrical,thermal and morphological behavior of nylon-66(PA)was inves-tigated.PA/FA composites were prepared by melt mixing via twin screw ex-truder,with varying weight percent(5 wt%,10 wt%,15 wt%and 20 wt%)of flyash.The results of composites were optimized and compared with vir-gin nylon-66.Mechanical and electrical properties of composites improved up to 10 wt%of FA loading without compromising the properties.The fly-ash filled nylon-66 composites showed a low abrasive wear rate.Increase the heat distortion temperature of composites with an increase in weight percent of flyash while opposing the melt flow rate.Flyash filler enhances the stiffness of plastics but significantly reduces the impact properties.Dis-persion of flyash was examined by impact fracture surface of composites using a scanning electron microscope.

COMPARATIVE RESEARCH ON THE CHARACTERISTICS OF THE FLYASH FROM COAL REFUSE-FIRED AND COAL-FIRED POWER PLANTS

The physical,chemical and mineral facies properties of the flyash from Xiezhuang Coal Refuse Fired Power Plant have been studied by means of naked eyes,microscope,chemical composition analysis and XRD analysis,and compared with that of the flyash from Taian Coal Fired Power Plant.The result shows that the flyash from coal refuse fired power plant is of better quality in making construction items,for being brighter in color,fine and high activity.Some ways of comprehensive utilization of the ash have been suggested in this paper.

Properties of flyash based wood geopolymer composite

Geopolymers are inorganic adhesive synthesized from industrial waste such as fly ash thus the development of wood geopolymer composite would be a low carbon footprint material.Geopolymers,being a non-formaldehyde adhesive can be used as an alternative binder for wood based composites where environmentally friendly and sustainability of product is important.In this study flyash as precursor is been used in the development of wood geopolymer composite product.Flyash is activated with a combination of sodium hydroxide and sodium silicate solutions at a weight ratio of 1:2.5 for geopolymer formation.The study investigated the properties of wood geopolymer composite made with ratios of wood particle to flyash percentage(23/77),(37/62),(44/55),(50/50)and(57/43).Geopolymer formation was observed by X-ray Diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR).Influence of wood particles in wood geopolymer composite were observed by Scanning electron microscope.The study shows that the water absorption and thickness selling properties of all the formulations of wood geopolymer composites are comparable with the medium density particle board and cement-bonded particleboard according to the IS:3087-2005 standard and IS:12406:respectively.Highest mechanical properties and good bond strength was obtained by the composite containing 23%wood particle ratio with 77%percent flyash.However,still improvement in mechanical properties is needed to achieve the mechanical properties comparable to cement bonded particle board.

冻结二灰固化碳酸盐渍土及损伤模型研究

在寒区工程中,盐-冻耦合效应往往会放大盐渍土体的强度损失。因此,考虑探究冻结作用下二灰固化碳酸盐渍土抗压性能的变化规律,以固化剂掺量、温度和加载速率作为影响因素,对二灰固化盐渍土进行了无侧限抗压试验,并提出一种考虑温度和加载速率的二灰固化盐渍土损伤本构模型。结果表明:石灰和粉煤灰能明显提高碳酸盐渍土的抗压强度,且使得改良土的应力-应变曲线由应变弱软化变为应变明显软化,当掺入3%石灰和12%粉煤灰时对碳酸盐渍土的固化效果最显著;温度和加载速率显著影响二灰固化土的抗压强度和弹性模量,三者之间关系可用非线性函数表达;二灰固化土抗压强度的影响因素按照重要性排序为温度>固化剂掺量>加载速率,且温度对改良土的影响远大于固化剂掺量和加载速率;所构建的二灰固化土损伤模型能较好地反映土体的应力应变关系和损伤变量的变化趋势。

硫酸铵焙烧活化—硫酸浸出粉煤灰提铝熟料的动力学研究

研究了以粉煤灰为原料,采用(NH_(4))_(2)SO_(4)焙烧活化—硫酸浸出法提铝,考察了液固体积质量比、反应温度、反应时间及硫酸浓度对铝浸出率的影响,探究了熟料酸浸过程动力学。结果表明:在液固体积质量比8/1、反应温度90℃、反应时间120 min、硫酸浓度20%优化条件下,铝浸出率为84.64%;浸出动力学公式为1-(1-x)13=6.03393e-22.0454/RT_(t),反应活化能为22.0454 kJ/mol。

水压-氯盐侵蚀耦合作用下膏体充填材料力学性能实验研究

在膏体充填开采中,煤矸石-粉煤灰胶结充填材料(CGFB)可有效控制地表沉降。CGFB在被注入采空区后会受到水压影响和氯离子侵蚀。因此,研究水压和氯离子侵蚀对CGFB性能的影响对于实现有效的绿色开采至关重要。将CGFB试样在0、0.5、1.5或3.0 MPa的氯化钠溶液中浸泡15天,通过单轴压缩试验、声发射信号监测、数字散斑应变测量、扫描电子显微镜和X射线衍射研究了试样的力学性能和劣化机理。结果表明,随着浸泡压力的增加,试样单轴抗压强度先增大后减小。当浸泡压力从0 MPa增加到1.5 MPa时,平均单轴抗压强度增加了43.5%。当浸泡压力从1.5 MPa增加到3.0 MPa时,平均单轴抗压强度下降18.9%。此外,水压会促进氯离子进入CGFB内部并产生弗里德尔盐。较高的水压-氯盐耦合作用增加了CGFB的孔隙率,与0 MPa样品相比,3.0 MPa样品的孔隙率增加8.2%。高水压作用下,膏体充填体内部孔隙裂纹发育贯通,力学性能劣化,其密实度与抗压强度下降。

粉煤灰中氧化钙含量对多孔陶瓷性能的影响

以工业废弃物粉煤灰为主料,制备多孔陶瓷具有来源广、成本低的优点,但粉煤灰的化学成分因煤的产地、燃烧方式有很大差异。笔者以粉煤灰为主原料,添加少量Al_(2)O_(3)和粘结剂干压成形后,在较低温度下烧制成多孔陶瓷,研究粉体粒径以及氧化钙含量对多孔陶瓷性能的影响。其结果表明:在相同烧成温度下,原料粒径对制品性能有较大影响;与常规粉煤灰相比,高钙粉煤灰具有优良的烧结活性,高的抗折强度和纯水渗透率。在1150℃保温2 h,烧成时性能最优,抗折强度为72 MPa、纯水渗透率为10783 L·m^(-2)·h^(-1)·bar^(-1)。

Change of structure and properties of chemically modified flyash

Flyash is a kind of waste solid in large amounts and with a sharp increase. In 1989,discharge capacity of flyash in China was 65 million tons. It is estimated that theamount will be more than 100 million tons per annum at the turn of the 21st century.Since the utilization ratio of flyash is no more than 30％ at present, treatment and

粉煤灰对低胶材自密实混凝土强度及孔结构的影响

【目的】为了研究粉煤灰替代率影响低胶凝材料用量的自密实混凝土抗压强度以及孔结构的机理,【方法】基于可压缩堆积模型(CPM),通过正交试验测试得到不同粉煤灰替代率和胶凝材料用量情况下的自密实混凝土流动性及28 d抗压强度,并基于X射线计算机断层扫描技术(X-CT)对自密实混凝土的内部孔结构特征进行了分析。【结果】研究结果显示:提高粉煤灰替代率和胶凝材料用量可以提高自密实混凝土流动性和28 d抗压强度,粉煤灰替代率达到20%左右时28 d抗压强度达到峰值,大于20%后有所回落。此外,提高粉煤灰替代率和胶凝材料用量可以降低自密实混凝土孔隙率,改善孔隙分布均匀性,减少孔隙数量,细化孔隙,提高孔隙球形度,优化自密实混凝土内部结构。【结论】研究成果可为水利水电工程中实现低胶凝材料用量自密实混凝土的低成本、高性能、绿色环保提供理论支持。

双掺粉煤灰-陶粒泵送混凝土力学性能研究

为提高粉煤灰和陶粒的利用率,达到节约资源、保护环境的目的,本文通过控制粉煤灰和陶粒的掺量,以密度、坍落度、混凝土抗压强度等参数作对比设计正交试验,对粉煤灰-陶粒双掺混凝土的力学性能进行研究。通过对试验结果进行极差分析,找出影响双掺混凝土的主次因素,作为BP神经网络的输入,预测混凝土的抗压强度,与实际值进行对比分析。结果表明:当粉煤灰掺量为12%,陶粒掺量在36%时,混凝土力学性能最佳,满足泵送要求;实测值和预测值的误差不超过2%,有很高的预测精度。上述结论可作为开发利用粉煤灰-陶粒混凝土的依据。

矿物聚合材料固化过程中的聚合反应机理研究

以粉煤灰、高岭石等为原料,制备出具有良好力学性能和耐酸性的矿物聚合材料制品,可代替部分硅酸盐水泥制品。根据矿物聚合材料制品在3 d、7 d、14 d、28 d的X射线衍射(XRD)、红外光谱(IR)、扫描电镜(SEM)、核磁共振(NMR)等测试分析结果,研究了该材料固化过程中的聚合反应机理。研究结果表明,矿物聚合材料在固化过程中的反应如下:(1)粉煤灰中的玻璃相在强碱的作用下首先发生溶解,其中部分Si—O、A l—O键发生断裂;(2)断裂之后的Si、A l组分在碱金属离子Na+、OH-等作用下形成Si、A l低聚体(—Si—O—Na、—Si—O—Ca—OH、A l(OH)4-、A l(OH)52-、A l(OH)63-),而后随着溶液组成和各种离子浓度的变化,这些低聚体形成凝胶状的类沸石前驱体;(3)前驱体脱水形成非晶相物质。核磁共振分析结果表明,28 d制品中,S i的存在方式以Q4为主。研究结果为进一步揭示矿物聚合材料的形成机理、改善制品的性能奠定了良好的基础。

利用粉煤灰制备高强矿物聚合材料的实验研究

以粉煤灰和内蒙古白云鄂博的富钾板岩提钾后的硅铝质滤渣为粉体原料,标准砂为骨料,采用振动成型方法,在90℃下养护24 h,制备了矿物聚合材料。实验结果显示:制品的7 d饱水抗压强度达78.5 MPa,28 d饱水抗压强度可达89.0 MPa;制品的含水率和吸水率分别为5.3%和15.0%;在20℃下,制品在浓度为1.0 mol/L的硫酸溶液中浸泡24 h,其质量损失率为2.1%。以制品的抗压强度为指标,研究了主要因素(提钾滤渣比例、固液质量比、硅酸钠含量和标准砂含量)对制品性能的影响。结果表明:干燥的提钾滤渣在粉体物料中的比例对制品的力学性能影响最大;硅酸钠水玻璃在液相中的比例约为70%,且标准砂占固相的比例为70%左右时,可制得力学性能良好的矿物聚合材料。矿物聚合材料的固结过程为:硅铝质原料在碱硅酸盐溶液中先分解为铝硅酸盐低聚体,低聚体再通过脱羟基聚合反应生成铝硅酸盐胶体相,进一步形成由[S iO4]4-和[A lO4]5-四面体相互连接的具有三维网络结构的矿物聚合材料基体相,从而赋予制品良好的力学性能。

氯化钙焙烧法提取粉煤灰中的氧化铝

研究了以CaCl2为配料对粉煤灰进行焙烧活化,焙烧熟料水洗后,用硫酸溶液浸取以回收粉煤灰中氧化铝的方法,并考察了焙烧温度和时间、CaCl2加量、硫酸浓度和浸取时间等因素对氧化铝回收率的影响.采用添加CaCl2焙烧的方法,可高效率破坏粉煤灰中的刚玉和莫来石,生成能被无机酸分解的物相,如钙铝黄长石、硅铝酸钙等.结果表明,按CaCl2:粉煤灰=0.8的比例加入CaCl2,于900℃焙烧30min,熟料经水洗涤后,按照每g粉煤灰～30mmol硫酸的量加入1～4mol/L的硫酸溶液,常温浸取30min,氧化铝浸出率可达95%以上.

粉煤灰改性及其在水处理中的应用进展

阐述了粉煤灰应用在水处理中的作用机理,回顾了粉煤灰在染料废水、含酚废水、重金属离子废水以及脱氮除磷中的应用进展。从酸改性、碱改性、盐改性、表面活性剂改性、混合改性以及合成沸石几个方面,介绍了近几年粉煤灰的改性方法,并对粉煤灰未来的研究方向提出了展望。

粉煤灰改性膨胀土水稳定性试验研究

针对典型中膨胀土及其粉煤灰改性土,进行了击实特性试验,并且在最优含水率、不同压实度状态下,进行了饱水后干密度、压实度变化特征试验,以及不同吸水时间、不同干湿循环次数下的无侧限抗压强度、压缩模量变化规律试验,以此探讨中膨胀土、粉煤灰改性膨胀土的水稳定性特征。试验结果表明:粉煤灰改性土可击实含水率范围较之未改性土宽,这给粉煤灰改性土路堤的施工带来了很大的方便。饱水之后,改性土的干密度和压实度比素土变化小,饱水能力不大,强度变化较小。改性土经过不同吸水时间和干湿循环次数之后,其强度最初发生急剧衰减,但最终趋于稳定。其衰减程度较之未改性土来说,有较大改善,水稳定性良好。

ICP-AES在分析飞灰中重金属化学形态上的应用

采用ICP-AES法对垃圾焚烧飞灰中七种重金属不同化学形态的含量进行了测定。该方法快速、准确，具有较好的精密度和准确度，除个别重金属浓度接近检出限时RSD相对较大外，其余测定结果RSD〈3％，加标回收率为85.7％～100.63％。分析结果表明：飞灰中重金属zn，Pb含量较高；Cd，Cu，Mn，Pb和Zn以碳酸盐结合态为主要形态，易进入环境；而Cr和Ni的Fe-Mn氧化物结合态最多，相对比较稳定。