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聚羧酸系减水剂的构性关系及其作用机理研究 总被引:2,自引:0,他引:2
聚羧酸系减水剂作为一种高性能减水剂,目前已成为国内外研究与发展的热点。概述了近几年国内外高效减水剂的研究与发展现状,阐述了聚羧酸系高效减水剂的分子结构、性能特点及作用机理,分子主链上阴离子基团越多及聚氧乙烯长侧链越长,聚羧酸系减水剂的分散性能和流动保持性能越好。聚羧酸系减水剂主要依靠聚氧乙烯长侧链的位阻效应和羧基及磺酸基的静电斥力来分散水泥颗粒。最后,提出了减水剂在应用中存在的问题并展望了其发展趋势。 相似文献
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京沪高速铁路Ⅵ标段主要为桥梁工程,采用高性能混凝土结构,设计寿命100年。本文主要介绍了聚羧酸系减水剂在该工程中的应用,重点探讨了原材料选择、生产过程质量控制、高性能混凝土配合比设计及聚羧酸系减水剂在高性能混凝土施工中应注意问题,并指出高性能混凝土与普通混凝土的异同。 相似文献
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聚羧酸减水剂因具有低掺量、高减水及绿色环保等优点备受青睐,但在实际应用中也常伴有因混凝土骨料泥含量过高而导致的相容性差、减水率低及坍落度损失大等问题,抗泥敏感性差已成为制约聚羧酸减水剂向更广层面应用的重要现实问题之一。文中从聚羧酸减水剂发展现状与面临的泥敏感性入手,阐述了聚羧酸减水剂对水泥、黏土和水泥/黏土分散体系的作用机理,在此基础上总结概括了改善和提高聚羧酸减水剂抗泥敏感性的应对措施,并对抗泥敏感性聚羧酸减水剂未来发展与应用进行了预测和展望。 相似文献
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以甲氧基聚乙二醇、马来酸酐、甲基丙烯磺酸钠等为原料,合成一种聚羧酸系高效减水剂,并与聚乙烯醇和超细SiO2粉体进行搅拌配制成喷雾干燥料液,在离心式喷雾干燥塔中对料液进行干燥,制备一种粉末状聚羧酸系减水剂,探讨干燥温度对粉末状聚羧酸系减水剂性能的影响。结果表明:在雾化盘转速为14 000 r/min,进料速率为80 g/min的条件下,随着干燥温度的升高,粉末状聚羧酸系减水剂的含水率下降,而滤渣率和休止角先下降后升高;干燥温度对粉末状聚羧酸结构没有很大的影响;最佳干燥温度为160~200℃。 相似文献
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分析了在低水泥浇注料中,由于微粉粒子在水中产生电离、吸附和晶格取代等现象导致其表面荷电形成双电层结构、微粉粒子产生絮凝的现象;阐述了化学外加剂对微粉粒子的分散作用机理,即DLVO理论和HVO理论;分别介绍了萘系(FDN)、脂肪族、氨基磺酸盐系、聚羧酸系高效减水剂的具体作用机理;分析了在低水泥浇注料中三聚磷酸钠、六偏磷酸钠、柠檬酸钠、密胺树脂、聚丙烯酸钠、氨基磺酸盐、聚羧酸系高效减水剂等化学外加剂的应用现状。认为聚羧酸系高效减水剂具有较好的减水效果,其生产与应用研究将越来越广泛和深入。 相似文献
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活性掺合料对脱硫基粉刷石膏制品性能的影响 总被引:1,自引:0,他引:1
利用脱硫石膏生产建筑石膏已经成为当前解决固体排放物问题的有效途径。粉刷石膏在耐水性和力学性能等方面的弱点影响其使用范围。本文研究复合掺加不同含量的活性掺合料对石膏制品耐水性和力学性能的影响。研究表明,掺加水泥和矿渣的效果最好,其耐水性可以提高40%,力学性能提高48%。 相似文献
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The water desorption behaviour of three different zinc oxide dental cements (two polycarboxylates, one phosphate) has been
studied in detail. Disc-shaped specimens of each material were prepared and allowed to lose water by being subjected to a
low humidity desiccating atmosphere over concentrated sulfuric acid. In all three cements, water loss was found to follow
Fick’s second law for at least 6 h (until Mt/M∞ values were around 0.5), with diffusion coefficients ranging from 6.03 × 10−8 cm2 s−1 (for the zinc phosphate) to 2.056 × 10−7 cm2 s−1 (for one of the zinc polycarboxylates, Poly F Plus). Equilibration times for desorption were of the order of 8 weeks, and
equilibrium water losses ranged from 7.1% for zinc phosphate to 16.9% and 17.4% for the two zinc polycarboxylates. 相似文献
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建筑石膏外加剂研究进展 总被引:13,自引:0,他引:13
石膏是国际上推崇使用的绿色建材.我国是石膏资源大国,具备发展石膏建材的资源和政策优势.使用外加剂是提升石膏基材料技术经济水平,推动石膏行业科技进步的最有效途径,也是高性能石膏基材料的核心技术.本文综述了国内外建筑石膏减水剂、缓凝剂、保水剂研究的现状,并对国内石膏外加剂研究与应用中存在的问题进行了分析. 相似文献
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为揭示梳形减水剂对水泥早期水化的影响规律,指导工程应用,通过SEM分析,研究了掺用3种典型结构的梳形减水剂的水泥浆体早期水化产物形貌及其电子特征数据。结果表明,梳形减水剂加速了水泥早期水化反应,且丙烯酸类、马来酸类共聚物分别促进了AFt、AFm的形成。因此,梳形减水剂品种对水泥早期水化和混凝土工程性能具有较大影响,应根据使用要求合理选用,必要时与缓凝剂、引气剂或消泡剂复合使用。 相似文献
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Zoi S. Metaxa Jung-Woo T. Seo Maria S. Konsta-Gdoutos Mark C. Hersam Surendra P. Shah 《Cement and Concrete Composites》2012,34(5):612-617
The use of effectively dispersed multiwalled carbon nanotube (MWCNT)/aqueous/surfactant suspensions in cement based materials have been shown to substantially improve their mechanical properties. The produced MWCNT suspensions have a high aqueous content, which corresponds to the mixing water. In the present work, a method for preparing highly concentrated MWCNT suspensions is presented, thus reducing the volume of the resulting admixture that is required in cement based materials. A centrifugal process, that uses two different ultracentrifuge rotors, was employed to reduce the quantity of water in the suspensions. Optical absorbance spectroscopy shows that the ultracentrifugation process increases the concentration of the MWCNT suspensions by a factor of 5. Using the highly concentrated MWCNT suspensions following dilution results in nanocomposites with mechanical properties that are comparable to the performance of samples prepared using the non-concentrated suspensions. These results verify that the ultracentrifugation concentration method successfully preserves the solubility of the MWCNT suspensions without affecting the reinforcing properties of the admixture. In this manner, the ultracentrifugation concentration method may constitute an effective preparation step for large-scale implementation of MWCNT admixtures. 相似文献
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S. A. Markestad 《Materials and Structures》1986,19(1):39-47
In recent years condensed silica fume has been acknowledged as one of the most effective pozzolans ever added to concrete. Properly used in adequate amounts and combined with a water reducing admixture, many important qualities of concrete are achieved or secured. The principle of dosage of water reducing admixture adopted in this combination has been to dose a quantity proportional to the amount of silicate fume. The positive effect on concrete strength from this combination of admixtures has been described as an “efficiency factor” for 1 kg silica fume between two to five when the efficiency of 1 kg cement is the unit. This study shows first that the dosing principle used until now is contradicted by experimental evidence and secondly that the water reducing admixture (lignosulfonate) used in the experimental series studied is responsible for 60% or more of the strength gain at 28 days, whereas the silica fume has to be credited for less than 40%. A more correct “efficiency factor” can then be calculated. 相似文献
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Ruzica Roskovic Irina Stipanovic Oslakovic Jure Radic Marijana Serdar 《Cement and Concrete Composites》2011,33(10):1020-1025
During the production of cement it is necessary to add a reducing agent that converts soluble hexavalent chromium into trivalent chromium. This paper explores effects of iron(II) sulphate reducing agents, namely monosulphate and heptahydrate, as cement admixtures, on corrosion of concrete reinforcement. Accelerated corrosion tests of reinforcing steel have been performed in pore solutions simulating concrete prepared using either CEM I or CEM II type cement, with addition of various concentrations of iron(II) sulphate reducing agent. All of the test results indicate corresponding tendencies and point towards the potential for iron(II) sulphate to foster or accelerate corrosion of the reinforcement. The results of this study indicate an immediate need for a more detailed research, especially in concrete as a more realistic corrosion environment, of the application of iron(II) sulphate as a reducing agent in cement. 相似文献