共查询到20条相似文献,搜索用时 78 毫秒
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GB/T12959—1991《水泥水化热测定方法(溶解法)》规定了水泥的水化温度(20±1)℃,以便于测定水泥的恒温水化速度、水化热量尤其是长龄期水泥水化热量。其原理是:依据热化学的盖斯定律,即化学反应 相似文献
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我公司在2010年进行了中热水泥生产,水化热试验采用直接法。通过研究摸索,我们将试验过程与结果的复杂计算,利用Microsoft Office Excel办公软件,实现对水泥水化热试验全过程上机计算,形成了基于Excel的水泥水化热计算的软件系统。特别是在温度曲线总面积计算上,我们根据“温度曲线作图法”计算总面积的原理,在Excel里通过先分解再求和的办法来完成,速度快,结果准确度高,可避免作图法人为的误差。计算出每只热量计的常数后,保存在“热量计数据库”中,需用时按编号调用。建立“试验温度数据库”、“热量计数据库”和“水化热试验数据库”,可随时进行数据的查询与对数据库的管理。交互界面上,尽量让操作员感觉直观方便,设置按钮,添加“宏”代码,各功能界面间通过点动按钮切换,复杂的计算过程通过填加公式和编制“宏”代码完成。 相似文献
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GB/T 12959—2008《水泥水化热测定方法》中两种方法的联合应用 总被引:1,自引:0,他引:1
<正>1两种测定方法比较水泥水化热的测定GB/T 12959—2008中有两种试验方法:直接法(代用法,由GB/T2022—1980修编而成)与溶解热法(基准法,由GB/T12959—1991修编而成)。 相似文献
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以硅灰为对比,利用微量热仪研究了纳米SiO2对硅酸盐水泥24 h内水化历程、水化放热特性的影响.研究结果表明:掺入纳米SiO2的水泥试样24 h内水化历程也可划分为类似于纯硅酸盐水泥水化的5个阶段;纳米SiO2的掺入,促使诱导期、加速期和减速期的出现提前,缩短了诱导期持续的时间;提高了水化开始时的放热速率,使第二放热峰的出现提前,增大了水化放热量. 相似文献
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Toufik Boubekeur Karim Ezziane El-Hadj Kadri 《Journal of Adhesion Science and Technology》2013,27(24):2741-2756
The study of the hydration kinetics appears as a prerequisite for understanding the physical and mechanical phenomena that control the behavior of cementitious materials. This research is based on monitoring the evolution of the degree of hydration for ordinary cement and those containing 10% of limestone powder, 20% of natural pozzolana or 30% of the blast furnace slag under high temperatures. The results provide a better understanding the effect of cure temperature on the hydration kinetics and understand the contribution of mineral additions on improving the cement properties. A new model proposed gives the satisfaction results for predicting in later age the heat of hydration of cements blended kept under constant temperatures. The latter has a wider appreciation of the results, where it gives correlation coefficients very close of unity. This justifies the reliability of this new model proposed. 相似文献
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硅酸盐水泥水化热的研究及其进展 总被引:1,自引:0,他引:1
硅酸盐水泥水化硬化过程中会释放大量的水化热,由此而产生的温度应力是导致混凝土出现裂缝的一个主要原因,对大体积混凝土的影响更为显著。因此,水泥混凝土水化热的研究长期以来受到国内外水泥和混凝土科学家及建筑工程界的重视。本文在总结前人关于水泥水化热研究方面提出的一些理论计算公式的基础上,综合分析了影响水泥水化热的因素,介绍了国内外关于水泥水化放热模型的最新研究进展以及水泥生产中降低水化热的技术措施。 相似文献
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研究了复掺粉煤灰、矿渣、硅灰的多组分水泥基材料的水化放热行为。研究结果表明,与纯P·O42.5水泥水化放热行为不同的是,多组分水泥基水化体系的诱导期延长,加速期和减速期的出现推迟,并且明显降低各水化阶段的水化放热速率,第2放热峰的出现发生了明显的推迟;温度为303K时,多组分体系的第2放热峰可细化成2个小峰,分别对应于熟料和掺合料的水化;323K下由于温度作用,矿物掺合料和水泥熟料的水化速率差距减小,第2放热峰基本没有明显分化现象;矿物掺合料的种类和掺量对多组分体系水化放热行为有较大影响,尤其是掺加硅灰时,早期水化速率明显增加。 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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为研究水浸泡养护对铝酸钙水泥水化行为的影响,以纯铝酸钙水泥Secar71为研究对象,试验温度为20℃,按水灰质量比0.3将水与铝酸钙水泥混合搅拌均匀,采用TG-DSC、XRD、SEM等方法对比研究了铝酸钙水泥在自然养护与水浸泡养护两种条件下分别养护1、7和15 d的水化行为。结果表明:铝酸钙水泥与水混合后,自然养护条件下,在最初的几分钟内有少量的放热,经过诱导期后有大量的放热,形成了一个"一次水化峰",之后进入稳定期;注水浸泡养护后试样内未水化水泥产生一个较"一次水化峰"低的"二次水化峰",之后水化缓慢;浸泡养护结束后试样内水化产物量与自然养护的相比明显增多,生长发育良好的片状CAH10相和絮状或粒状的三水铝石沿试样孔隙分布,填充气孔,试样结构更加致密。 相似文献
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Rachel Cook Hongyan Ma Monday Okoronkwo Gaurav Sant Aditya Kumar 《Journal of the American Ceramic Society》2021,104(4):1831-1840
The hydration of the two most reactive phases of ordinary Portland cement (OPC), tricalcium silicate (C3S), and tricalcium aluminate (C3A) is successfully halted when the activity of water () falls below critical thresholds of 0.70 and 0.45, respectively. It has been established that the reduction in relative humidity (RH) and suppresses the hydration of all anhydrous phases in OPC, including less explored phases like dicalcium silicate, that is, belite (β-C2S). However, the degree of suppression, that is, the critical threshold, for β-C2S, standalone has yet to be established. This study utilizes isothermal microcalorimetry and X-ray diffraction techniques to elucidate the influence of on the hydration of -C2S suspensions via incremental replacements of water with isopropanol (IPA). Experimentally, this study shows that with increasing IPA replacements, hydration is increasingly suppressed until eventually brought to a halt at a critical threshold of approximately 27.7% IPA on a weight basis (wt.%IPA). From thermodynamic estimations, the exact critical threshold and solubility product constant of -C2S () are established as 0.913 and 10−12.68, respectively. This study enables enhanced understanding of β-C2S reactivity and provides thermodynamic parameters during the hydration of β-C2S-containing cementitious systems such as OPC-based and calcium aluminate-based systems. 相似文献
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In earlier work, we have observed discrepancies relating to the early hydration of calcium aluminate cement (CAC) when comparing data from heat flow calorimetry of CAC paste with results from mortar strength tests using the crushing method. Here, we investigated on this phenomenon and found that the sand which is used as a filler exerts a major influence on CAC hydration resulting in acceleration. Furthermore, in particular fine filler materials such as, for example, microsilica, fine limestone powder, and especially α- and γ-Al2O3 also produced a strong hydration accelerating effect which is dependent on their specific surface area. The mechanism underlying the acceleration is that under alkaline conditions their negative surface charge attracts calcium ions as was confirmed via inductively coupled plasma atomic emission measurements. Such a layer generates favourable conditions for the nucleation of CAC hydration products (C-A-H phases). The resulting crystalline hydrates which form on the surface of the filler particles submerged in CAC cement pore solution were visualized via SEM imaging. This way, specifically selected fillers can significantly accelerate CAC hydration and save precious lithium salts which are commonly used to boost the early strength of CAC. 相似文献