共查询到20条相似文献,搜索用时 828 毫秒
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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。 相似文献
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利用磷石膏生产水泥缓凝剂 总被引:1,自引:0,他引:1
我国工业副产品磷石膏每年约1500万t,大量堆存,利用率低,作为水泥缓凝剂,需除去磷石膏中有害杂质,根据磷石膏水洗加石灰处理后,其煅烧产物具有胶凝性的特点,将其加工,制成球状(5~25mm)水泥缓凝剂,实现了50%替代天然石膏生产出合格水泥。 相似文献
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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. 相似文献
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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. 相似文献
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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。 相似文献
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以改良黄土的水力学性质优化分析为核心,研究了改良黄土的渗透性能和渗透过程中渗透系数的变化。通过对黄土添加水泥、石灰和粉煤灰作为改良材料,进行了改良黄土渗透性试验。试验结果表明,在击实试验控制干密度情况下且改良材料含量较低情况下,随着改良材料含量的增大,改良黄土的渗透系数呈增大趋势,黄土的结构性明显得到了改善;渗透过程持续,随着改良黄土中石灰、水泥和粉煤灰-水泥混合物水化作用的进行,改良黄土的渗透系数呈减小趋势。因此,根据工程需要,可以通过进一步优化改良材料添加配比方案,在改良渗透性能的基础上增加强度,满足黄土地区施工安全要求。 相似文献
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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。 相似文献
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利用高钙粉煤灰生产膨胀水泥的初步研究 总被引:10,自引:2,他引:8
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。 相似文献
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Gengying Li 《Cement and Concrete Research》2004,34(6):1043-1049
This paper presents a laboratory study on the properties of high-volume fly ash high-strength concrete incorporating nano-SiO2 (SHFAC). The results were compared with those of control Portland cement concrete (PCC) and of high-volume fly ash high-strength concrete (HFAC). Assessments of these concrete mixes were based on short- and long-term performance. These included compressive strength and pore size distribution. Significant strength increases of SHFAC compared to the high-volume fly ash high-strength were observed as early as after 3 days curing, and improvements in the pore size distribution of SHFAC were also observed. In this work, the hydration heat of nano-SiO2 fly ash cement systems was also studied in comparison to the fly ash-cement systems and to the pure cement systems. In addition, the weight change of fly ash incorporating nano-SiO2, fly ash, and nano-SiO2 alone after immersed in saturated lime solution was also studied. 相似文献
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Taisir Khedaywi Asim Yeginobali Mohammad Smadi
J. Cabrera
《Cement and Concrete Research》1990,20(6):843-852The ash of the retort residue of the oil shale from central Jordan has been further tested to evaluate its pozzolanic activity. According to the preliminary experiments the ash had cementive properties. Thermogravimetric analyses were performed on ash, cement, ash blended cement and ash-lime pastes. In the blended pastes, addition of ash seemed to decrease the amount of lime generated. In the ash-lime paste the lime consumption by ash with time followed a similar trend to the reactions of trass and silica fume with lime. The ash-lime reaction was mainly a diffusion controlled process obeying the Ginstling-Brounshtein equation. The pozzolanic activity of the ash, as indicated by its lime activity and rate constant, was not as high as the other pozzolans compared, mainly due to its lower fineness. Tests on compressive strengths of cement and lime mortars blended with ash confirmed the findings, indicating that up to 20% of cement could be replaced by ash used as an admixture. Ash-lime mortars could gain moderate strengths under accelerated curing, suitable for some building units. 相似文献