利用白糖生产缓凝水泥的生产实践

缓凝剂主要起抑制水泥水化、延长混凝土凝结时间、减少混凝土坍落度经时损失的作用;我公司经过精心组织,多次试验,由最先使用缓凝剂生产缓凝水泥,到现在利用白糖代替缓凝剂成功生产缓凝水泥,取得了较好的成功。     

立窑水泥与回转窑水泥对混凝土减水剂适应性的研究

研究了立窑水泥和回转水泥与混凝土减水剂的相容性。实验结果表明,与回转窑水泥相比,优质立窑水泥配制混凝土的减水率与回转窑水泥相近,但凝结时间大幅度延长。适当细磨可以缩短含氟立窑水泥配制混凝土的凝结时间,但无法消除立窑水泥配制混凝土凝结时间偏长的缺点。     

水泥和缓凝剂对混凝土凝结时间的影响--兼论预拌混凝土的超缓凝及其预防

讨论了水泥和缓凝剂(或缓凝减水剂)对混凝土凝结时间的影响。水泥凝结时间长则混凝土的凝结时间长，掺缓凝剂(或缓凝减水剂)后凝结时间更长，掺量越大凝结时问越长。预拌混凝土产生超缓凝的主要原因在于水泥的凝结时间过长和(或)缓凝剂(或缓凝减水剂)掺量过大。环境温度低也可能使混凝土超缓凝。     

影响水泥凝结时间和强度检验的主要因素

<正>1前言水泥性能检测是对水泥产品质量的综合鉴定方法。水泥检验人员不但要具备专业的水泥检验理论知识,还要熟悉各标号水泥的性能与强度属性等基本常识。目前,国内很多建筑施工单位、混凝土生产企业普遍缺乏专业的水泥试验技术人员与检测设备,在水泥检测中,经常遇到水泥凝结时间、强度方面的问题。因此,本文主要阐述在水泥检验中,影响水泥凝结时间、强度的主要因素。2影响水泥凝结时间检验的主要因素2.1水泥温度对水泥凝结时间检验的影响     

水泥凝结时间的确定与调控

水泥凝结时间是水泥的重要技术指标，国家标准对每一种水泥的凝结时间都有规定。这种规定一是基于水泥使用时水泥凝结时间过早导致来不及施工和水泥凝结时间过迟导致施工周期长而影响施工进度。二是基于不同地域的水泥生产企业和水泥用户需要有一个根据生产和使用情况选择水泥凝结时间的范围。因此，研究对水泥凝结时间的影响因素并确定适宜的凝结时间，是水泥生产过程中一项重要的技术性工作。     

高强碱矿渣水泥与混凝土缓凝问题研究

本文论述了碱矿渣水泥与混凝土凝结问题及缓凝措施,针对高强碱矿渣水泥及混凝土迅速凝结的特点。作者研制成功了新型高效缓凝剂——YP-3复合缓凝剂。该缓凝剂可任意调节和控制高强碱矿渣水泥与混凝土的凝结时间。     

混凝土凝结时间偏长问题的分析及解决措施

从水泥质量、混凝土用料以及配比等方面分析了某混凝土搅拌站混凝土凝结时间偏长的原因,最终发现凝结时间偏长是由于混凝土用砂受到了醇类物质污染所致.采取相应措施后,混凝土凝结时间恢复正常.     

矿物掺合料对硫铝酸盐水泥混凝土性能的影响

通过试验研究不同掺量的矿渣和硅灰对硫铝酸盐水泥混凝土凝结时间、力学性能、体积收缩和早期抗裂性的影响。研究结果表明，在硫铝酸盐水泥混凝土中，掺入矿渣会延长混凝土的凝结时间，抑制收缩变化和早期开裂，但会显著降低力学性能；掺入2.5%的硅灰可以缩短硫铝酸盐水泥混凝土的凝结时间，提高力学性能、抑制收缩变化和早期开裂，但硅灰过量则会降低混凝土的力学性能。综合考虑硫铝酸盐水泥混凝土在工程中的实际应用，确定胶凝材料的最佳配比为硫铝酸盐水泥:矿渣∶硅灰=87.5∶10∶2.5，在此配比下混凝土的初凝和终凝时间分别为72min和114min,8h抗压、抗折强度分别为28.2MPa和4.1MPa。     

水泥质量波动对预拌混凝土性能的影响

通过分析广州市3家水泥厂1年时间里的水泥胶砂强度，标准稠度用水量和凝结时间等指标的质量波动情况，探讨了水泥质量波动对预拌混凝土性能的影响，分析结果表明，水泥强度，需求性和凝结时间波动对混凝土性能的影响较大，而且对不同等级混凝土的影响幅度不大。     

碱对水泥水化及性能的影响（三）——碱对水泥及混凝土性能的影响

综述了碱对水泥及混凝土性能的影响,包括：水泥凝结时间,水泥中适宜SO3含量,水泥及混凝土强度,水泥及混凝土开裂敏感性,水泥的流变性能及水泥与减水剂相容性,水泥石的孔隙率和孔结构,混凝土碳化、徐变和弹性模量,混凝土的耐久性。     

论大型水泥企业开发经营商品混凝土

针对我国水泥生产、商品混凝土拌制与混凝土施工三者相互分离的现象，提出了大型水泥企业开发经营商品混凝土．实现水泥生产-商品混凝土拦制-混凝土施工一体化经营的思路并分析了其优越性。     

YJ—2型减水剂在吴淞矿渣水泥中的使用效果

通过化学和红外光谱分析,由SO_4~(2-)溶出量和掺不同量F~-的水泥凝结时间表明,F~-是影响吴凇矿渣水泥掺木质素磺酸钙异常凝结的重要因素。对水泥、混凝土一系列性能的测定表明,YJ-2型减水剂对吴淞矿渣水泥有很好的适应性,用其配制的泵送混凝土的各项技术指标均满足工程要求,并可达到既节约水泥又保证工程质量的目的。     

水泥厂常见质量投诉的原因分析与调查处理

顾客质量投诉的原因分析与调查，是困扰许多水泥厂的一个难题。作者结合自己多年处理顾客质量投诉的经验，简单介绍了处理顾客质量投诉的调查原则和内容；重点对水泥厂最常见的质量投诉内容包括混凝土强度不足，凝结时间异常：混凝土坍落度偏小，经时损失大；水泥与外加荆相容性不好；水泥颜色变化、混凝土地面起砂及水泥结块等等投诉，分别进行了现象描述，原因分析和调查方法介绍。     

白糖和葡萄糖酸钠二元复合对长螺旋咬合桩用超缓凝混凝土性能的影响

为解决咬合桩施工现场超缓凝混凝土的制备问题,探究缓凝剂的作用机理,采用白糖和葡萄糖酸钠按质量比7∶3配制复合缓凝剂,对比一次搅拌和二次搅拌工艺,制备超缓凝混凝土。采用抗压抗折一体化试验机、环境扫描电子显微镜(ESEM)、总有机碳分析仪和等温量热仪测试分析超缓凝混凝土的力学性能、微观形貌、吸附量和水化性能。结果表明,混凝土的凝结时间随着缓凝剂掺量的增加而延长。当缓凝剂掺量为0.38%(质量分数)时,一次搅拌组初、终凝时间分别为31 h和46 h,二次搅拌组初、终凝时间分别为34 h和50 h;当缓凝剂掺量为0.50%(质量分数)时,一次搅拌组初、终凝时间分别为61 h和78 h,二次搅拌组初、终凝时间分别为65 h和84 h。两种掺量下,混凝土56 d抗压强度均达到40 MPa以上,满足两种工况的施工要求。采用二次搅拌工艺制备超缓凝混凝土有助于进一步延长混凝土的凝结时间,改善混凝土拌合物的流动性,但会略微降低混凝土的抗压强度。不同缓凝剂在水泥颗粒表面的吸附能力强弱顺序为:葡萄糖酸钠>白糖-葡萄糖酸钠>白糖>白糖-葡萄糖酸钠后掺。缓凝剂的掺入起到降低水化放热,抑制水泥水化的作用,从而延长混凝土的凝结时间。     

A case history: Effect of moisture on the setting behaviour of a Portland cement reacting with an alkali-free accelerator

Flash setting accelerators are a class of admixtures commonly used for sprayed concrete during tunnel excavation. They allow an immediate set of concrete which can bind to the substrate without dangerous collapses. Such a coating layer prevents the section convergence that is its tendency to squeeze. The early strength development (till 1 h) of the sprayed concrete can be connected to the final set time of cement pastes admixed with the accelerator. The lower is the final set time, the higher should be the early strength. Two main methods are used to project concrete: wet and dry. Today, for safety reasons and to obtain more homogeneous concrete layers, the wet method is becoming more diffused. This technique requires the use of liquid flash setting accelerators which are pumped to a nozzle and immediately projected onto the rock wall. In the European market, two kinds of setting accelerators are mainly available: alkali-rich and alkali-free. Recently, for several reasons, the demand of alkali-free accelerators is growing very rapidly. They are water solutions of aluminium sulphate with a total alkali metal content (expressed as equivalent of Na₂O) lower than 1%. In order to develop new and more performing accelerators, several studies are in progress to elucidate their action mechanism and the factors affecting the setting of accelerated concretes.During an experimental study on the setting behaviour of several cement pastes reacting with an alkali-free accelerator, we found a cement showing, as time proceeded, a persistent setting time reduction. We discovered that the effect was connected to the cement exposure to the moisture. A mineralogical investigation performed on this particular cement revealed the presence of hemihydrate as setting regulator. In order to study the interaction between the alkali-free accelerator and this moist aged cement, some morphological (ESEM-FEG), crystal-chemical (XRD), physical-chemical (hydration temperature profile) and chemical (ICP) analyses on cement paste samples were carried out.This study showed a significant setting time reduction of cement paste samples admixed with an alkali-free accelerator when they are composed of a Portland cement containing β-hemihydrate that was previously exposed to moisture. Such an effect seems to be related to the reduction of the β-hemihydrate dissolution rate.     

二水石膏对海工高性能复合胶凝材料性能的影响

为满足海洋工程混凝土结构的耐久性和施工等方面的需求，需采用复合胶凝材料配制海工高性能混凝土。采用硅酸盐水泥＋粒化高炉矿渣粉＋硅灰制成复合胶凝材料，与普通硅酸盐水泥进行性能比较研究，并重点研究了二水石膏（即三氧化硫含量）对复合胶凝材料性能的影响。研究结果表明，三氧化硫含量对复合胶凝材料的工作性和凝结时间的影响不大，但对其强度和反应抗氯离子渗透性的电量产生显著影响，三氧化硫含量高的复合胶凝材料具有较高的早期强度和良好的抗氯离子渗透性能。     

Monitoring the setting of concrete containing blast-furnace slag by measuring the ultrasonic p-wave velocity

Ultrasonic transmission measurements allow the continuous monitoring of the setting of both mortar and concrete samples, which is important to determine for instance the formwork removal time. However, aspects such as the cause of the low initial velocity, the relation between the velocity and the setting times and the effect of cement type or cement replacing additives are still under discussion. Therefore, different concrete compositions with blast-furnace slag were tested by traditional as well as ultrasonic measurements.The ultrasonic method gives a more complete picture of the setting. The change of ultrasonic velocity in time is sensitive to the differences in setting behaviour of the tested mixtures. The initial setting seems to correspond with the inflection point of the velocity-vs.-time graphs and the final setting with the point at which the velocity increase levels off.     

Moderne Verfahren zur Beschichtung zementgebundener Untergründe

Modern Procedures for Coating of Cement Bound Grounds Still up to the middle of the sixties freshly prepared cement bound rough-casts and concrete surfaces were thought to be very critical grounds for painting. The effect of the high alcality of these grounds in connection with the residual humidity of the building and the influence of the weather was especially feared, which could cause saponification of the binding agent and destruction of inorganic colour pigments. Especially at concrete surfaces difficulties with adhesion of the paints on concrete were added, since at that time in building practice again and again pollution of the concrete surfaces by lagging oils and waxes occured. Defects by flaking off were the outcomes. Only when concrete pushed forward quickly in housing construction, where prefabricated building with prefabricated elements played a decisive role, special painting and coating systems were developed which allowed not only a durable protection of concrete, but moreover a colour fashioning. In the same measure as security in concrete painting was achieved, the difficulties in painting of cement containing rough-casts were solved. According to the state of the technic of today tested and well proved painting systems for coating of cement bound rough-casts and concrete are available.