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磷石膏作为缓凝剂应用的问题 总被引:2,自引:0,他引:2
磷石膏是工业副产物,化学成分与天然二水石膏相近,如弃之不用则为工业废渣,不仅占用大片土地,且污染环境。因此,把磷石膏作为资源开发利用,这对于资源、环境的良性循环、协调发展具有重要意义。现仅就磷石膏作为缓凝剂的应用问题作简要论述,供同业参考。 1水泥用石膏的现状 目前,我国水泥工业使用的石膏,几乎全部是天然石膏,而副产化学石膏的应用则不多。早在50~60年代,东北一些水泥厂由于天然石膏供应短缺,曾先后利用过多种副产石膏,如磷石膏、氟石膏、盐石膏以及废模石膏等。后来由于天然石膏的大量供应,以及副产石膏在使用上存在一些问题,都先后停止了使用。 相似文献
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研究了一种缓凝微膨胀型的路面基层稳定专用水泥中石膏掺量、粉煤灰掺量对水泥强度和凝结时间的影响,并研究了这种水泥的涨缩性能以及稳定粒料的强度。研究表明:(1)这种专用水泥具有凝结时间长的特点,终凝时间大于6h,随着石膏掺量的增加,水泥的凝结时间和强度在侧(S03)在4.0%-4.5%有最大值;(2)粉煤灰掺量增加,该水泥的凝结时间延长,强度逐渐降低。当掺量大于50%后水泥的水化过程明显延缓;(3)这种水泥具有明显的微膨胀性并且干缩率较低,但采用这种水泥配制的路基稳定粒料的强度比采用通用水泥稳定粒料的强度有明显提高,达到相同的设计强度可以节省水泥用量15%左右。 相似文献
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研究了两种预处理方式的磷石膏作缓凝剂时对水泥物理性能的影响,并与以天然石膏作缓凝剂的水泥性能进行比较。结果表明:煅烧磷石膏作缓凝剂时,水泥凝结时间及3 d和28 d强度接近或好于掺天然二水石膏的水泥,可对其进行资源化利用。 相似文献
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The present work describes a study of setting and hardening of blends of borogypsum, fly ash, and Portland cement clinker (PC). The possibility of using borogypsum instead of natural gypsum in fly ash-cement matrix has been investigated through several tests. In addition, the effects of molasses on the setting times of cement and strength of the mortar were also studied. The setting times of the cement were retarded when the natural gypsum was replaced by borogypsum. Molasses exhibited a rather significant retarding effect when used in combination with borogypsum in cement. The inclusion of molasses to the system at a level of 0.1% resulted in a reduction in early strength of the mortar. However, it significantly enhanced the strength of the mortar after 7 days of curing age. In general, the cement prepared with borogypsum was found to have similar strength properties to those obtained with natural gypsum, and inclusion of molasses into the system significantly increased the strength of the sample after 7 days of curing age. 相似文献
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介绍了采用氯甲基环氧丙烷和三甲胺盐酸盐水相合成阳离子醚化剂(CHPTA)的工艺。考察了升温反应时间、反应温度、原料配比对产品结晶点的影响。结果表明:在低温(10±1℃)滴加氯甲基环氧丙烷,25℃反应2 h,35℃反应3 h;原料配比n(三甲胺盐酸盐)∶n(氯甲基环氧丙烷)=0.95∶1.00的条件下合成的产品结晶点可达到-18℃以下。 相似文献
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Investigations on the use of electric-arc furnace dust (EAFD) in Pozzolan-modified Portland cement I (MP) pastes 总被引:1,自引:0,他引:1
The use of electric-arc furnace dust (EAFD) in civil construction is not common. In countries where this waste is collected, it is used in the recovery process of heavy metals, such as Zn, Cd, Pb, and Cr. In Brazil, these processes are still not used, because the percentages of heavy metals of commercial value are not economically feasible (e.g. zinc with only 13% of mass). Thus, more studies are necessary aimed at making EAFD a subproduct for civil construction. For this reason, the waste behavior was evaluated in Pozzolan-modified Portland cement I (MP) pastes. Setting time and hydration heat were determined, as well as mineralogical and microstructural characterization, in order to better understand the residue's effect upon cement paste's properties, both in fresh and hardened states. The results showed that EAFD slows down the Portland cement's hydration reactions. This behavior is better verified using hydration heat curves as compared to the Vicat equipment. As of the mechanical performance, it was verified that even though the EAFD retards the hydration reaction of the cement in its initial ages, in more advanced ages the trend is having significant gain of resistance in pastes containing EAFD. 相似文献
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聚丙烯成核剂--二(3,4-二甲基二苄叉)山梨糖醇(DMDBS)合成的研究 总被引:3,自引:0,他引:3
以D-山梨糖醇和3,4-二甲基苯甲醛为原料,在固体酸催化剂下进行醇醛缩合反应,合成了二(3,4-二甲基二苄叉)山梨糖醇(DMDBS),并对影响产品熔点和收率的因素进行了考察。介绍了DMDBS的合成路线和作用机理以及最优化条件:在3,4-二甲基苯甲醛和D-山梨糖醇投料摩尔比为2.0~2.1:1,催化剂、反应用溶剂用量分别为反应基础物的4.0%、580%(质量分数),促进剂的用量以维持体系反应温度恒定为基准,反应时间6小时下,DMDBS的产品收率大于70%,熔点高于250℃,并用红外光谱仪对其结构进行了分析测试。 相似文献