共查询到18条相似文献,搜索用时 78 毫秒
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超高性能水泥基复合材料组分复杂,高温养护会使水泥基材料水化过程发生显著变化,其早期水化、硬化及微结构形成机理仍存在众多疑惑.本文利用等温量热仪对不同水灰比、不同养护温度、不同矿物掺合料下的超高性能水泥基复合材料的水化放热过程进行研究.试验结果表明,减小水灰比、提高养护温度都将促进超高性能水泥基复合材料的水化放热进程;此外,硅灰的掺入能明显促进水化,但粉煤灰却有着延缓的作用. 相似文献
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水泥基材料的水化动力学模型 总被引:20,自引:0,他引:20
介绍了水泥基材料的水化动力学模型.根据实验测定的水化放热数据,采用模型给出的积分和微分方程,对水泥基材料的水化反应中的3个基本过程即结晶成核与晶体生长(NG)、相边界反应(I)和扩散(D)进行了表征,得到反应速率常数K、反应级数n和表观活化能Ea等动力学参数以及各反应阶段的反应速率与反应度的关系.计算得到的各阶段的反应速率曲线能较好地分段模拟由量热实验得到的胶凝材料实际水化速率dα/dt曲线.观察3个阶段的相互关系,可对水泥基材料复杂的水化机理进行解释.水泥基材料的水化反应存在两种不同的历程:NG-I-D或NG-D.在水化初期NG是控制因素,随着水化程度提高,逐渐转由I或D控制反应. 相似文献
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本文以水泥水化过程中所体现的基本动力学方式和原理为基础,以建立能够与水泥水化养护时间和水化程度曲线直接对应的动力学模型为目标,开展了水泥水化动力学机理及模型建立的研究。 相似文献
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矿渣是由高炉炼铁熔融的矿渣骤冷时形成的细粒状玻璃态物质,它是一种活性掺和料.将矿渣粉作为掺合料掺入水泥基材料中,其活性可以得到充分的发挥,使得水化反应充分,进而改善水泥基材料的力学性能.本文分析了矿渣和水泥的水化动力学影响因素,建立了矿渣-水泥胶凝体系的水化动力学方程,主要从水胶比、温度以及比表面积这三个因素来分析矿渣掺量对矿渣-水泥胶凝体系水化过程的影响.结果表明,增大水胶比、升高温度及增大水泥颗粒的比表面积均能够不同程度的加速矿渣-水泥胶凝体系的水化进程. 相似文献
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针对多年冻土地区工程施工时混凝土养护的问题,采用10%、20%、30%的矿粉和粉煤灰替代量等量替代水泥,测试了-3 ℃恒温养护条件下0.38水胶比水泥浆体在各个龄期的水泥水化热,计算了水泥水化程度;分析了龄期及矿物掺合料对水泥水化程度的影响规律,建立了综合考虑龄期和矿物掺合料替代量的水泥水化程度计算模型.结果表明:-3 ℃恒温养护下,矿物掺合料等量替代水泥,水泥浆体的水化程度会降低,粉煤灰降低水化程度的值要比矿粉高;在相同矿物掺合料替代量下,随着龄期的增长,矿物掺合料对水泥水化程度的影响逐渐减弱;同一龄期时,随着矿物掺合料的增加,矿物掺合料对水泥水化程度的影响逐渐增强;利用建立的模型计算了分别掺入15%矿粉和粉煤灰的水泥水化程度,与实测值相比,计算值偏离值较少,预测精度较高. 相似文献
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The mechanism for the slow rate of reaction between portland cement and water during the early stage is not well understood, but it probably is controlled by either the rate that the reactants diffuse through a barrier that surrounds the unreacted cement grains or by the rate that nuclei of the stable product form and grow or by both rates. New evidence using environmental scanning electron microscopy is presented about the structure of a layer that forms around the particles of cement. Preliminary observations that relate mixing to the structure of the layer are also presented. 相似文献
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Young-Min Kim Seong-Hyeon Hong Hwan Kim 《Journal of the American Ceramic Society》2002,85(8):1941-1946
A chlorine-bearing alinite cement was synthesized using reagent-grade chemicals, and the phase evolution and hydration behavior of the alinite clinker were examined. The effects of the MgO content on alinite formation and hydration also were investigated. Alinite began to appear at 1000°C from β-C2 S, C11 A7 CaCl2 , and unreacted raw materials, and an almost single-phase alinite was obtained at 1300°C. The alinite phase also was produced without MgO addition. However, CaO, β-C2 S, and C11 A7 CaCl2 phases were present. Alinite cements hydrated rapidly after a short incubation period, and the hydration products were C-S-H gels, Ca(OH)2 , and a Fridel's saltlike phase. The local environmental changes of silicon and aluminum during the formation and hydration of alinite were determined using magic-angle-spinning nuclear magnetic resonance spectroscopy. The Cl− -ion exsolution from the alinite paste during hydration was measured using ion chromatography. 相似文献
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通过进行水化热测试、非蒸发水含量测试、X射线衍射分析、扫描电镜分析、压汞测试及强度试验,研究了钴铁镁铝水滑石-碳纳米管复合材料(CoFeMgAl-LDHs/CNTs)对水泥水化过程、硬化水泥净浆孔结构及强度的影响。结果表明,CoFeMgAl- LDHs/CNTs复合材料通过成核作用显著提升了水泥3 d内的水化程度,从而显著提高了水泥净浆3 d内的抗压强度,3 d后强度提高效果逐渐减小,7 d后复合材料对硬化水泥浆体强度没有明显的提高作用。掺入CoFeMgAl-LDHs/CNTs复合材料的水泥净浆与空白净浆相比,胶凝孔和毛细孔含量明显增多,大孔含量有所降低,同时复合材料的桥联作用进一步优化了水泥净浆的微观结构,从而提高了水泥基体薄弱部位的应力承载能力。因此在同一龄期,复合材料掺入后硬化水泥净浆的强度有所增大。由于复合材料掺量的变化对孔径分布没有明显的影响,改变复合材料的掺量对同龄期硬化水泥净浆强度提升影响较小。 相似文献
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The degree of hydration of the four major anhydrous cement phases in three U.K. portland cement mortars has been observed during the period of water storage at room temperature after an initial short-term heat cure. Such a heat cure at 85° or 100°C for 12 h generally accelerated the initial hydration of the four major anhydrous minerals in portland cement. Subsequent retardation of the degree of hydration of the alite, tricalcium aluminate, and ferrite phases was observed when these heat-cured mortars were stored at ambient temperature. General similarity but some differences in hydration behavior were observed between the three cements. The hydration of belite in the heat-cured mortars during storage at room temperature produced porous inner products that favored deposition of ettringite and reduced the risk of expansive ettringite formation. The substantial retardation in hydration of the aluminate-bearing phases, especially the ferrite phase, during the storage at room temperature raised the overall SO3 /Al2 O3 ratio of the cement hydrates formed, bringing about a potential for ettringite formation and hence the risk of expansion through delayed ettringite formation. 相似文献
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