水泥凝结时间测定的影响因素及对策

本文介绍了试验条件、仪器设备、操作手法等几方面对水泥凝结时间测定的影响.只有在正确理解标准方法的前提下,将试验条件、仪器设备调整到良好的检测状态,统一操作手法,不断提高操作人员的检测水平,检测结果才会更准确,具有可比性.     

水泥凝结时间测定的影响因素及对策

本文介绍了试验条件、仪器设备、操作手法等几方面对水泥凝结时间测定的影响。只有在正确理解标准方法的前提下,将试验条件、仪器设备调整到良好的检测状态,统一操作手法,不断提高操作人员的检测水平,检测结果才会更准确,具有可比性。     

浅析水泥凝结时间检验中的影响因素

本文通过对当前水泥凝结时间检验过程中存在的操作差异进行比较,发现人员成型试模操作差异是造成水泥凝结时间检验结果离散的主要原因。另外在标准稠度用水量试验中,发现量水法相比称水法,标准稠度用水量稍稍偏大,但未影响水泥标准稠度试验结果,对水泥凝结时间检验结果影响不大。     

MSWI飞灰制CSA水泥的组成优化及性能研究

以垃圾焚烧（MSWI）飞灰为主要原料,在实验室成功烧制了硫铝酸钙（CSA）水泥熟料,继而着重研究了不同种类和不同掺量的石膏对CSA水泥的抗压强度、水化性能、标准稠度用水量和凝结时间的影响;研究了细度对CSA水泥性能的影响。结果表明：无水石膏和二水石膏均促进C4A3S^-水化,提高CSA水泥的早期强度;无水石膏的最佳掺量是5％,二水石膏可根据实际情况进行调整;掺加无水石膏的CSA水泥其标准稠度用水量较对照水泥C—II低,比对照水泥C—I有所增加;掺加5％无水石膏后水泥的凝结时间与对照水泥C-II接近,当掺量增至10％后出现急凝。本试验中,CSA水泥比表面积在288—580m^2／kg范围时均表现出良好的力学性能。     

通用水泥实施ISO标准后的效果和需解决的问题

我国通用水泥实施GB／T１７６７１－１９９９〈水泥胶砂强度检验方法（ISO法）〉已经１年多了。作为起草单位，我们和水泥界的同行们一样，非常关心它的实施效果和存在的问题。２００２年６月份，我们协助中国建材协会对通用水泥标准实施情况进行了一次问卷调查，调查对象包括各省行业管理办公室和协会、省水泥质检站、施工单位以及水泥企业等４个方面。通过这项工作，使我们对ISO强度检验方法的实施效果有了了解，现就此做一总结归纳，并提出需进一步研究和解决的问题。１对我国通用水泥基本性能的影响１．１抗压强度和产品标号（等级…     

浅析水泥凝结时间检验中的影响因素

<正>1课题背景水泥凝结时间是水泥性能检验中的重要项目之一,长久以来已经有很多文章探讨过有关水泥凝结时间的影响因素[1-3],然而如何才能够做好水泥凝结时间检验,至今仍旧是一个难题。在日常实验室水泥物理性能比对活动中,凝结时间检验结果往往是比对指标中数据离散最大的参数之一[4]。现行水泥凝结时间检验标准GB/T 1346—2011[5]中,其水泥凝结时间检验大致可以分解为四个主要过程:一是标准稠度用水量试验;二是成型试模样;     

醇胺类化合物对硅酸盐水泥性能的影响

试验选用三乙醇胺、二乙烯三胺,三异丙醇胺,氨基乙基乙醇胺,聚乙烯醇磷酸铵作为早强剂,研究其在微小掺量下对硅酸盐水泥标准稠度用水量、凝结时间、与外加剂的适应性、胶砂强度等方面的影响。试验结果表明,醇胺类化合物的掺加对水泥标准稠度用水量产生了增大的趋势;三乙醇胺与N-(2-羟乙基)乙二胺明显的缩短了水泥的初凝时间与终凝时间,三异丙醇胺、二乙烯三胺延长了水泥的初凝时间,缩短了水泥的终凝时间;三异丙醇胺与N-(2-羟乙基)乙二胺在0.2‰掺量时对水泥的流动度无影响,N-(2-羟乙基)乙二胺在0.1‰掺量时,使水泥的流动度得到增加,其它组均对水泥与外加剂的适应性造成不良影响;除了三异丙醇胺在掺量为0.20‰与0.50‰时的早期强度低于空白水泥之外,其他各组都有不同程度的增加,后期强度,三异丙醇胺在任何掺量下,明显强于三乙醇胺。     

关于水泥标准稠度用水量检验方法的探讨

通过对多家同品种水泥的净浆试验比对,对现行国家标准GB／T1346—2001中关于代用法测定水泥标准稠度用水量的部分条款存有歧意。试验研究表明,当试锥下沉深度在26口2mm范围内,不同拌和水量下的凝结时间极差较小,超出此范围会有显著增大。     

干法脱硫渣对水泥性能的影响

研究干法脱硫渣对水泥标准稠度、凝结时间、强度的影响,实验结果表明,干法脱硫渣对水泥标准稠度需水量有降低的作用,对水泥凝结时间有缩短的作用,对水泥3d抗压强度有提高作用,对水泥28d强度有降低作用。     

不同标准稠度用水量检验方法对凝结时间检验结果的影响

试杆法比试锥法对水泥标准稠度用水量的反映更为敏感,在检验工作中应尽量采用试杆法测定水泥的标准稠度用水量。用试锥法测定的具有标准稠度的水泥净浆,用来测定水泥凝结时间时,普遍比用试杆法的测定结果略短一些。在实际工作中,如果采用试锥法测定水泥的标准稠度用水量时,应选用试锥下沉深度在（29±1）mm的范围,具有这样标准稠度的水泥净浆用来测定水泥的凝结时间,才能够使其和用试杆法检测所得的水泥标准稠度用水量相对接近,才更加合理,减少实验误差,从而保征水泥凝结时间检验结果的准确性。     

高镁水泥制备及其膨胀性能

制备MgO质量分数分别为6%、9%、12%和15%的高镁水泥,通过扫描电镜（SEM）、扫描电镜/能谱联合仪（SEM/EDS）、X射线衍射（XRD）等检测方法和膨胀性试验分析MgO质量分数对熟料煅烧和净浆膨胀性能的影响.结果表明：随着MgO质量分数增加,熟料煅烧时液相量增加,熟料密实度提高.当熟料中MgO质量分数为12%时,养护温度由20℃增加到38℃,试件90d龄期膨胀率由0.120%增加到0.244%;38℃养护时,掺入35%粉煤灰的试件90d龄期膨胀率由0.244%降至0.070%.当MgO质量分数高于12%时,尽管存在粉煤灰的抑制作用,但高镁水泥依然能产生一定膨胀,可以有效地补偿混凝土的温降收缩.     

减水剂对铝酸盐水泥施工性能的影响

研究了木质磺酸盐、磺化三聚氰胺甲醛和萘磺酸盐甲醛缩合物3种(类)减水剂对铝酸盐水泥(CA50)胶砂的减水率、初凝时间、终凝时间、耐压强度和抗折强度的影响。结果表明:上述减水剂对同一牌号的铝酸盐水泥的减水作用无差异;木质磺酸盐类减水剂对铝酸盐水泥的缓凝作用较强,磺化三聚氰胺甲醛的减水率最高,有促凝作用;3种(类)减水剂均使铝酸盐水泥胶砂的早期强度有所下降,其中萘磺酸盐甲醛缩合物的下降幅度最大。     

耐火水泥改性研究

采用水化－煅烧－细磨方法对高铝水泥和纯铝酸钙水泥进行活化处理。测量了改性水泥的粒度、比表面积、凝结时间。试验结果表明，改性处理使以上耐火水泥的颗粒尺寸大大降低，比表面积增加；改性水泥中无大颗粒存在，其凝结时间满足施工要求．用改性水泥结合的浇注料的强度明显高于用原水泥结合的浇注料的强度。     

The effect of temperature upon the setting behaviour of refractory calcium aluminate cements

A setting time parameter has been determined from the heat evolution versus time curve measured by means of a thermocouple embedded in the cement paste as well as by the Gillmore needle. The setting time increases with increasing temperature, until it reaches a maximum between 26 and 30°C, for four out of the five refractory calcium aluminate cements studied. This anomalous retardation is not, therefore, restricted to ciment fondu, as reported elsewhere. The rate of consumption of CA during the first 24 hours of hydration as determined by X-ray diffraction also indicated a retardation at 30°C compared with 20°C for Secar 51 and Secar 71. The cause of the anomaly cannot be the presence of C₂S, which is virtually absent in most of the cements studied. An alternative explanation must be found, which should also explain why Secar 80 behaves differently from the other cements investigated.     

聚乳酸切片及纤维的性能探讨

利用解偏振法测定了1#-4# PLA切片的等温结晶动力学,求解了PLA切片的Avrami指数n;用X射线衍射法测定了等温结晶后PLA切片样品及纤维的结晶度,测试了PLA纤维的力学性能。结果表明：PLA切片等温结晶动力学参数Avrami指数n在1.29～2.16之间,且4#〉3#〉2#〉1#;各批PLA切片等温结晶后的结晶度顺序与各批PLA纤维结晶度的顺序相一致;PLA纤维的强力随结晶度的增加而增加。     

In situ synchrotron powder diffraction study of the setting reaction kinetics of magnesium-potassium phosphate cements

This work reports a kinetic study of the formation of magnesium-potassium phosphate cements accomplished using in-situ synchrotron powder diffraction. The reaction: MgO + KH₂PO₄ + 5H₂O → MgKPO₄ · 6H₂O was followed in situ in the attempt of contributing to explain the overall mechanism and assess the influence of periclase (MgO) grain size and calcination temperature (1400-1600 °C) on the reaction kinetics. Numerical kinetic parameters for the setting reaction have been provided for the first time. The best fit to the kinetic data was obtained using a weighted nonlinear model fitting method with two kinetic equations, representing two consecutive, partially overlapping processes. MgO decomposition could be described by a first order (F1) model followed by a Jander diffusion (D3) controlled model. Crystallization of the product of reaction was modelled using an Avrami model (A_n) followed by a first order (F1) chemical reaction. A reaction mechanism accounting for such results has been proposed.     

Bond strength and chemical interaction of self-adhesive resin cements according to the dentin region

The aim of the study is to evaluate the effectiveness and level of chemical interaction of self-adhesive resin cements (SRCs) according to the dentin region. One hundred eight sound human third molars and three SRCs were selected: Bifix SE (Voco), Maxcem Elite (Kerr), and RelyX U200 (3M ESPE). Ninety human molars were used for the bond strength test and 18 teeth for the X-ray diffraction (XRD) characterization. A flat surface of superficial, deep, or axial dentin was exposed. For bond strength evaluation, 90 indirect composite resin restorations (10 mm in diameter, 2.0 mm-thick) were built and cemented with one of the SRCs according to the manufacturer's instructions. The restored teeth were then cut into sticks with cross-sectional areas of 0.8 mm² and tested in tensile at a speed of 0.5 mm/min (n=10). The results of bond strength were statistically analyzed by two-way ANOVA and Tukey's test (α=0.05). The fractured specimens were classified under SEM. The remaining teeth were further sectioned in order to build dentin fragments with 2.0 mm² of area and 0.2 mm in thickness for XRD analysis. In general, significantly higher bond strength was found when bonding to axial and deep dentin compared to superficial dentin. Comparing the bonding effectiveness of the SRCs, taking into account the mean bond strength obtained in the 3 dentin regions, the study found no significant difference (p>0.05). Although RelyX U200 showed similar bond strength irrespective of the dentin region (p>0.05), the bonding results of the other 2 SRCs varied significantly (p<0.05). There was a higher incidence of cohesive failure in the SRCs for all groups. The XRD analysis detected different perceptual reductions of hydroxyapatite crystallinity for all SRCs, indicating a particular chemical interaction in each experimental condition. Thus, it can be concluded that the bond strength and chemical interaction of the SRCs can vary significantly according to the dentin region.     

浅谈水泥窑协同处置废弃物分解炉投加口设置

水泥窑烧成系统是极其复杂的热工设备,燃烧和工艺都错综复杂。工作机理也是极度非线性的,研究起来非常困难。本文根据水泥工艺、悬浮预热、气固学原理、水泥窑协同相关工艺设备等理论,对分解炉开口位置原则和优化设置等方面进行总结和整理。     

维生素E脂质体的制备与性能研究

采用薄膜蒸发-高压均质法制备维生素E（VE）脂质体,研究了VE脂质体配方中不同成分的比例及水合介质对脂质体包封率的影响。结果表明,VE脂质体载药量越大,包封率越低。胆固醇含量在体系中要适当。最佳的水合介质是磷酸盐缓冲液。采用薄膜蒸发结合高压均质处理法制备的VE脂质体粒径达到120nm,而且比较稳定。