425R型白色硅酸盐水泥的研制

本文介绍了保定地区白水泥厂关于425R型白色硅酸盐水泥的研制、试生产情况、工艺技术措施以及经济效益分析。     

白色硅酸盐水泥新、老标准检测"比对"统计分析体会和建议

10多年来，我国白色硅酸盐水泥（以下简称白水泥）的质量检验，一直执行GB／T2015—91的老标准。2005年1月19日国家质量监督检验总局和国家标准化管理委员会联合发布的GB／T2015—2005白水泥新标准，于2005年8月1日开始实施，但新老标准之间过渡期为半年，所以原老标准将于2006年2月1日作废。新、老标准的本质差别，除了检测所用的标准砂不同外，新标准的水泥用量减少，即灰砂比从1：2．5增大至1：3，用水量也相应增大，即水灰比从原来的0．44增大到0．5，所以水泥强度标号大体降低一个等级，如老标准425#标号对应的新标准为32．5MPa强度等级，执行新标准后四川两地三厂的白水泥3天和28天强度之间的关系如何。     

我厂改善水泥颜色及提高早期强度的措施

1前言我厂主要生产”425普通硅酸盐水泥，1994年前生产的水泥早期强度较低，色泽偏黄，市场竞争力较差。为扭转这一被动局面，我们从调整配料方案和改变混合材这两方面着手，通过一段时间的摸索，找到了解决上述问题的措施，现将有关情况作一介绍。2调空配料方案原配料方案为：     

天然沸石与矿渣生产复合硅酸盐水泥质量及效益分析

本文以实际生产数据分析了利用天然沸石和粒化高炉矿渣生产复合硅酸盐水泥的质量和效益，探讨了降低水泥生产成本和提高掺沸石水泥物理力学性能的方法和途径。     

425R型粉煤灰硅酸盐水泥的试验研究

江苏省扬中市长旺热电厂锅炉年排放粉煤灰和煤渣25000t以上,为解决灰、渣的出路,市热电建材厂自筹资金1400多万元,于1996年8月底新建成一条年生产能力可达10万t的粉煤灰水泥粉磨站生产线,生产425粉煤灰水泥一次成功。但早期强度低,凝结时间长,为了解决这一问题,从1997年     

白色硅酸盐水泥熟料及结球料的矿物组成分析

白色硅酸盐水泥(简称白水泥)是装饰用的特种水泥。白水泥熟料的石灰饱和系数和通用硅酸盐水泥熟料相差不大,但硅率较高(一般在3.5~5.0),铝率很高。这种低铁、高硅、高饱和比的熟料,要求煅烧温度达　1 500℃以上,为降低烧结温度,在生料中必须加入少量矿化剂,最常用的矿化剂是萤石,其掺量控制在0.5%之内。白水泥熟料矿物组成范围为：C3S (55%~60%),C2S (20%~30%),C3A (12%~14%),C4AF(<1%)。     

以普通石膏作缓凝剂磨制白色硅酸盐水泥

以普通石膏作缓凝剂磨制白色硅酸盐水泥申龙章，王光哲山西省黎城振华白水泥厂（０４７６００）山西省黎城振华白水泥厂是一个年产６．５万ｔ白色硅酸盐水泥的生产企业，自１９８７年投产以来，一直使用河南三门峡的白色纤维状石膏。为了降低生产成本，通过考察试验，从１...     

探寻提高我厂ISO水泥强度的途径

我厂是年产 30万 t普通水泥的机立窑企业,主要产品有 425R、 525号普通硅酸盐水泥两种。根据有关文献介绍,按目前情况,我厂很难稳定生产 52. 5级普通水泥。为了探寻适合我厂提高水泥强度的有效途径, 2000年下半年我厂利用 2号生产线在实际生产中进行了一系列试验项目,并获得了大量有助于我厂尽快适应 ISO标准的有效措施。 1原燃材料、主要设备及生产工艺 1. 1原燃材料化学成分 　　原燃材料化学成分及煤的工业分析结果分别见表 1、表 2。 表 1原燃材料化学成分％ 名称LossSiO2Al2O3Fe2O3CaOMgOCaF2单质SΣ石灰石42.341.200.97…     

白色硅酸盐水泥净浆结粒现象浅析

我厂是生产白色硅酸盐水泥的企业,经过几年的生产实践,产品质量已达到国标各项理化指标。但是,白水泥净浆结粒问题一直是我厂的技术障碍,影响了我厂水泥在市场的声誉,给用户带来不必要的经济损失,为此,我厂技术人员进行了一系列的试验研究,找出结粒原因,并提出解决办法和措施。一、概况我厂煅烧的熟料加入适量的石膏,经过MPS160C辊式立磨磨制的白水泥,经水化后的水泥净浆中有许多直径为0.5～3毫米左右的小颗粒。在环境温度高、湿度低的情况下更为严重。严重时,水泥水化后看不到水泥     

优质水泥的评价

1对水泥品质的认识水泥胶砂强度的高低一直以来是评价水泥质量的重要标准,实施ISO方法后,水泥的检测性能与国际接轨,但与其在现代混凝土中的作用相差还较远。水泥胶砂强度高是水泥实物质量一方面的体现,却不是混凝土质量的唯一保证。水泥生产技术人员普遍认为水泥的富余强度越高,产品质量越好,产品质量的改善往往只体现在胶砂强度的提高方面;施工单位则普遍认为水泥的早期强度越高,混凝土强度发展得越快,其质量越有保证。而且水泥早期强度越高,施工速度可以加快,成本可大幅度下降。在市场竞争日益激烈的情况下,水泥生产企业为了迎合施工单位的需要,对水泥胶砂强度的追求已远超出国标的要求,     

Monitoring Portland cement hydration: Comparison of methods

Various experimental methods of monitoring Portland cement hydration are compared. The methods are quantitative X-ray diffraction analysis (QXRD), measurement of non-evaporable water as loss on ignition and by thermogravimetry, conduction calorimetry and measurement of chemical shrinkage. Correlations between these different measures of hydration are obtained using samples of paste for three different Portland cements. The correlation between non-evaporable water and QXRD data was dependent on the chemical composition of the cement and shows that less water was chemically bound at early ages, for a given amount of cement reacted. A near-linear relationship was found between chemical shrinkage and QXRD data. The correlation between heat of hydration and QXRD data was approximately linear and not greatly affected by cement type.     

Early hydration of white Portland cement in the presence of bismuth oxide

Abstract

Abstract

Mineral trioxide aggregate (MTA) is a clinical product comprising a mixture of 80 wt-% Portland cement and 20 wt-% bismuth oxide, which is used as a root-filling material in dentistry. The influence of bismuth oxide on the hydration reactions of Portland cements is not well understood. In this study, the impact of 20 wt-% replacement of bismuth oxide on the hydration of white Portland cement was monitored by powder X-ray diffraction (XRD), ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) and transmission electron microscopy (TEM). The findings of this research have confirmed that bismuth oxide is an inert additive in white Portland cement, which does not participate in the hydration reactions.     

三峡工程用中热硅酸盐水泥品质指标控制的意义及方法

为确保用于大坝工程中水泥的质量, 1998年中国长江三峡工程开发总公司 (以下简称"总公司" )委托国家水泥质量监督检验中心对供应三峡大坝水泥的生产厂进行驻厂监督三峡工程用中热硅酸盐水泥 R2O和 MgO指标,并根据各厂的实际情况订出具体监控办法。笔者作为国家水泥质量监督检     

Sulfate ingress in Portland cement

The interaction of mortar with sulfate solutions leads to a reaction front within the porous material and to expansion. Thermodynamic modelling coupled with transport codes was used to predict sulfate ingress. Alternatively, “pure” thermodynamic models - without consideration of transport - were used as a fast alternative to coupled models: they are more flexible and allow easy parameter variations but the results relate neither to distance nor to time. Both transport and pure thermodynamic modelling gave comparable results and were able to reproduce the changes observed in experiments. The calculated total volume of the solids did not exceed the initial volume of the paste indicating that not the overall volume restriction leads to the observed expansion but rather the formation of ettringite within the matrix and the development of crystallisation pressure in small pores. The calculations indicate that periodic changing of the Na₂SO₄ solution results in more intense degradation.     

A preliminary investigation of the in vitro bioactivity of white Portland cement

Freshly-mixed and partially-cured ordinary Portland cement (OPC) pastes have been shown to exhibit good biological compatibility with a range of cells and tissue-types; particularly those associated with bone formation. Formulations based on OPC have been used as dental restoratives and are now being investigated for their potential use in orthopaedic repair. Despite the current clinical interest in OPCs, very little is known about their chemistry in the physiological environment. In this respect, research to investigate aspects of the interactions between a white Portland cement (WPC) paste and simulated body fluid (SBF) has been carried out in vitro. Exposure to SBF has been found to promote the precipitation of a layer of ‘bone-like’ hydroxyapatite on the surface of WPC paste which underpins its ability to integrate with living tissue. The dissolution of portlandite and formation of calcite were also observed on contact with SBF.     

The AFm phase in Portland cement

The AFm phase of Portland cements refers to a family of hydrated calcium aluminates based on the hydrocalumite-like structure of 4CaO·Al₂O₃·13-19 H₂O. However OH⁻ may be replaced by SO₄²⁻ and CO₃²⁻. Except for limited replacement (50 mol%, maximum) of sulfate by hydroxide, these compositions do not form solid solutions and, from the mineralogical standpoint, behave as separate phases. Therefore many hydrated cements will contain mixtures of AFm phases. AFm phases have been made from precursors and experimentally-determined phase relationships are depicted at 25 °C. Solubility data are reported and thermodynamic data are derived. The 25 °C stability of AFm phases is much affected by the nature of the anion: carbonate stabilises AFm and displaces OH and SO₄ at species activities commonly encountered in cement systems. However in the presence of portlandite, and as carbonate displaces sulfate in AFm, the reaction results in changes in the amount of both portlandite and ettringite: specimen calculations are presented to quantify these changes. The scheme of phase balances enables calculation of the mineralogical balances of a hydrated cement paste with greater accuracy than hitherto practicable.     

白水泥质量控制要点分析

白水泥作为常用的彩色硅酸盐水泥,其特点在于较高的白度,色泽明亮;但生产白水泥与通用硅酸盐水泥的差异在于白水泥烧成温度高,熟料液相量少、液相粘度高,并且其白度受着色元素的影响明显。本文介绍了生产白色硅酸盐水泥的质量控制要点,包括原材料的选择、过程质量控制要求、熟料的烧成和冷却以及白水泥粉磨的注意事项。     

Thin-foil studies of hydrated Portland cement

Ion-beam milling has been used to produce thin-foils of hardened cement paste for examination in an analytical scanning transmission electron microscope (STEM). Resin impregnation has been usefully employed to support delicate microstructure, especially that of young pastes, so that cross-sections of hydrating cement grains can be examined. The morphologies observed in STEM are similar to those observed in conventional scanning electron microscope (SEM) studies.