共查询到19条相似文献,搜索用时 762 毫秒
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为研究硅灰及粉煤灰对不同养护龄期的水泥浆体强度及收缩性能的影响,以水胶比为0.29的水泥浆体为基体,设计制备了五种硅灰及粉煤灰掺量的复合水泥浆体,借助量热仪和压汞仪测试表征了不同复合水泥浆体的水化放热特性以及孔结构组成,分析了水化放热量、孔隙率等参数随硅灰和粉煤灰掺量增加的变化规律,建立了复合浆体抗压强度与孔结构以及水化特性与收缩应变之间的量化关系。结果表明,掺入粉煤灰会大幅降低水泥净浆早期抗压强度,但对减小自收缩应变和干缩应变极为有利。掺入硅灰能明显提高净浆3 d抗压强度,但当硅灰掺量超过10%(质量分数)后,净浆3 d自收缩应变及28 d干缩应变增加极为明显。掺入硅灰会使水泥水化诱导期开始和结束的时间提前,还会增加水化反应级数和各阶段的反应速率常数值,导致水泥-硅灰复合浆体的水化放热总量和放热速率相较于水泥-粉煤灰体系大幅增加。粉煤灰和硅灰的掺入均能有效细化水泥浆体内部孔结构,提高凝胶孔比例,大幅降低大孔比例。复合浆体的72 h水化放热总量和3 d自收缩应变呈现正相关关系,而孔隙率和抗压强度呈现明显的负相关关系。 相似文献
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本文研究了不同拌和水以及海水拌和时粉煤灰和硅灰掺量对硫铝酸盐水泥(SAC)砂浆力学性能和表观孔隙率以及净浆凝结时间、化学收缩、孔溶液pH值和氯离子结合能力等的影响,并通过XRD、SEM和EDS分析水泥水化产物和微观结构。结果表明,海水能加快SAC早期水化并提高其早期强度,但后期强度和淡水拌和时无明显差别。粉煤灰和硅灰均会延长SAC凝结时间,对早期抗压强度不利,而掺加质量分数为5.0%和7.5%的硅灰能提高SAC砂浆28 d抗压强度。硅灰掺量增加时会提高用水量和表观孔隙率,降低流动性,使水泥化学收缩增大,降低净浆pH值且减少氯离子结合量;粉煤灰能够提高砂浆流动性,减少水泥化学收缩,但掺量越大对SAC砂浆抗压强度和抗折强度越不利,掺质量分数为10%的粉煤灰可小幅提高氯离子结合量且减小表观孔隙率。 相似文献
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硅粉在普通硅酸盐水泥中合理掺量的试验研究 总被引:1,自引:0,他引:1
《应用化工》2015,(11):2011-2013
研究了硅粉对普通硅酸盐水泥性能的影响,结果表明,水泥净浆的用水量会随着硅粉的掺量呈现规律性增长趋势,掺入适量粉煤灰可有效改善缺陷。从水泥净浆的强度测试结果,结合水泥净浆粘度随硅粉掺量大小的变化情况,综合选定硅粉在普通硅酸盐水泥中的合理掺量范围为5%~10%,为进一步进行硅粉高性能水泥的研制提供了试验依据。 相似文献
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采用选择性溶解法和非蒸发水法分别测量了粉煤灰-硅灰和水泥的反应程度;通过复合浆体中有效水胶比的计算和非线性拟合的方法,得出复合浆体中水泥的反应程度,研究了粉煤灰-硅灰-水泥三元体系中矿物掺合料对水泥水化程度的影响.根据矿物掺合料和水泥的反应程度数据,并结合强度数据分析了复合水泥浆体干燥收缩的规律.研究发现:在相同龄期,随着硅灰的逐渐增多,粉煤灰的逐渐减少,复合浆体的干燥收缩逐渐增大;在不同龄期,复合浆体的干燥收缩值随着龄期的延长,干燥收缩曲线由陡逐渐变得平缓;当粉煤灰和硅灰总掺量为50%,而其中的硅灰为5%时,可以得到干燥收缩较小,抗压强度较高的三元复合水泥浆体. 相似文献
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本文研究了普通硅酸盐水泥掺量及不同种类和掺量的矿物掺合料对硫铝酸盐水泥性能的影响.结果表明普通硅酸盐水泥掺量小于60%时,普硅水泥-硫铝酸盐水泥体系(OPC-SAC体系)的胶砂强度随着普通硅酸水泥掺量的增加而降低,普通硅酸盐水泥掺量大于60%时,OPC-SAC体系的胶砂强度随着普通硅酸水泥掺量的增加而增大.并且对早期强度的影响较大.在硫铝酸盐水泥体系中掺入矿渣、粉煤灰和硅灰时,其胶砂强度随着掺量的增加而降低,在相同掺量下,矿物掺合料对强度的贡献率为:硅灰>矿粉>粉煤灰,对凝结时间的影响强弱为:硅灰>矿粉>粉煤灰. 相似文献
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普通混凝土高性能化研究与施工应用(下) 总被引:1,自引:1,他引:1
2000年3月至4月份,我们以普硅525号水泥掺入水泥量1.8%的FDN-5R减水剂,配制出流动度为300mm的水泥浆作为基准组,以相同数量的FNF减水剂和不同品种的矿物粉料、不同比例取代水泥、配制对比组,进行不同外加剂和矿物粉细掺合料对净浆流动度影响的试验结果(见表2)。表2的数据表明,掺入Ⅱ级粉煤灰、磨细粉煤灰、磨细矿渣粉对净浆流动度基本没有影响,掺入硅灰或沸石粉,使净浆流动度减小,而且随着掺量的增加,减小的幅度更加明显,是由于硅灰颗粒极细、沸石粉为多孔结构,都有较强的吸附能力,从而减小了净浆流动度,而在矿物超细粉相同取代比例的情… 相似文献
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半刚性基层极易发生开裂,严重影响道路质量.采用正交试验方法,以工作性、力学性能和体积稳定性等作为评价因素,设计了一种高性能聚合物水泥基灌浆材料,并研究了各原材料对灌浆材料性能的影响.结果表明:水灰比对水泥净浆的流动性、强度和干缩性起主要影响因素;粉煤灰和聚合物掺量主要影响净浆的流动性和强度;减水剂掺量主要对净浆的干缩性影响较大;确定了用于半刚性基层裂缝修补的聚合物水泥净浆的最佳配比:水灰比0.57,粉煤灰掺量10%,减水剂掺量0.03%和聚合物掺量6%.最后验证了高性能聚合物水泥基灌浆材料其他方面的优异性能. 相似文献
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研究了海水环境下掺入硅灰、粉煤灰、矿渣对硫铝酸盐水泥抗压强度、化学收缩和水化产物的影响规律.结果表明:当硅灰的掺量为2.5%时,水泥浆体的抗压强度比空白组高.矿渣掺量为10%的水泥浆体28 d抗压强度明显超过掺入硅灰和粉煤灰时的强度,60 d强度高于空白组.掺入2.5%硅灰后,水泥浆体的化学收缩增大;在水化早期,粉煤灰和矿渣的火山灰活性很低,导致水泥浆体的化学收缩降低.掺入10%硅灰加快了硫铝酸盐水泥3 d水化反应,钙矾石生成量增多,水泥浆体早期强度比掺其它掺合料有所提高,但体积过快膨胀会破坏其内部结构,对水泥浆体的强度发展不利. 相似文献
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矿物外加剂及测试方法对硬化水泥浆体自收缩值的影响 总被引:1,自引:0,他引:1
分别采用两种不同试验方法对比研究了单掺粉煤灰、硅灰和矿渣微粉这三种常用的矿物外加剂(即水泥混合材)对水泥浆体早期自收缩的影响。研究结果表明,单掺粉煤灰、硅灰和矿渣微粉后,硬化水泥浆体的自收缩值分别随其掺量的增加而减小、增大和增大。本文分析研究了这三种常用的矿物外加剂对硬化水泥浆体自收缩产生影响的原因,并对比分析了本试验采用的两种试验方法,发现波纹管法更能准确地测量水泥浆体的早期自收缩,参照现行行业标准JC/T313-1982测试无法正确地反映硬化水泥浆体更早期的收缩现象。 相似文献
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M Isabel Sánchez de Rojas Julián Rivera Moisés Frías Félix Marín 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(3):209-217
Copper slag is a by‐product generated during smelting to extract copper metal from the ore. The copper slag obtained may exhibit pozzolanic activity and may therefore be used in the manufacture of addition‐containing cements. In this paper the effect of the incorporation of the copper slag in cement is measured. Blends of copper slag with Portland cement generally possess properties equivalent to Portland cement containing fly ash, but very different to the silica fume incorporation. Copper slag and fly ash reduce the heat of hydration more effectively than silica fume in mortars. The replacement of 30% cement by copper slag reduces the flexural and compressive strength in a similar way to fly ash; however, after 28 days, the reduction is less than the percentage of substitution. Hydrated calcium aluminate phases were analysed using scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques. The pozzolanic activity of copper slag is similar to that of fly ash and higher than silica fume. In the presence of low water/cement ratios, certain pozzolanic materials produce a very compact cement paste that limits the space available for hydration products, a determining factor in the formation of hydrated calcium aluminates. SEM was found to be a useful analytical technique when aluminates are formed and can be clearly detected by XRD. Copyright © 2008 Society of Chemical Industry 相似文献
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Results of calorimeter tests on Portland cement-silica fume-fly ash mixtures are presented. Data indicate that silica fume accelerates cement hydration at high water/cementitious ratios and retards hydration at low water/cementitious ratios. On the other hand, fly ash retards cement hydration more significantly at high water/cementitious ratios. When silica fume and fly ash are added together with cement, the reactivity of the silica fume is hampered and the hydration of the cementitious system is significantly retarded. 相似文献
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The curing requirements of silica fume and fly ash mortars were investigated in this study. Silica fume and fly ash mortar specimens were moist cured for periods of 0, 3, 7, 14 and 28 days. After each of the five periods, the moist curing was interrupted by oven-drying the specimens at a temperature of 110°C for 3 days. The specimens were later tested for compressive strength and absorptivity. In this study, it was also determined whether the losses in strength and impermeability of silica fume and fly ash mortars due to an interruption in curing could be regained by recuring. The test results clearly indicate that the curing requirement of silica fume mortar is less than that of plain cement mortar, while in the case of fly ash mortar it is hogher than that of plain cement mortar. 相似文献
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本文用3种不同的试样制备方法和3种测孔方法分别测定了加矿渣、粉煤灰和硅灰等掺合料的硬化水泥浆体孔隙率。结果表明,试样制备方法和孔隙率测定方法一样,都会影响孔隙率的测定结果,掺加掺合料以后,这种影响更为显著。 相似文献
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Utilization of fly ash with silica fume and properties of Portland cement-fly ash-silica fume concrete 总被引:2,自引:0,他引:2
Thanongsak Nochaiya 《Fuel》2010,89(3):768-774
This paper reports the normal consistency, setting time, workability and compressive strength results of Portland cement-fly ash-silica fume systems. The results show that water requirement for normal consistency was found to increase with increasing SF content while a decrease in initial setting time was found. Workability, measured in term of slump, was found to decrease with silica fume content (compared to blends without silica fume). However, it must be noted that despite the reduction in the slump values, the workability of Portland cement-fly ash-silica fume concrete in most cases remained higher than that of the Portland cement control concrete. Furthermore, the utilization of silica fume with fly ash was found to increase the compressive strength of concrete at early ages (pre 28 days) up to 145% with the highest strength obtained when silica fume was used at 10 wt%. Moreover, scanning electron micrographs show that utilization of fly ash with silica fume resulted in a much denser microstructure, thereby leading to an increase in compressive strength. 相似文献