水泥基材料早期水化特性与体积稳定性的关系

采用五路裂缝测定仪和非接触式电阻率测定仪，分别测试了水泥砂浆在干燥条件下约束收缩开裂的初裂时间与相应水泥浆体早期水化24h内的电阻率变化，分析研究了水泥浆体在非常早期水化中的电阻率极小值与相应砂浆的初裂时间的关系，结果发现二者之间具有较好的线性相关性（相关系数〉0．90）。机理研究表明在水泥类型和骨料确定的条件下，胶凝材料体系初始水化的液相特征是影响早期收缩开裂的关键；不同化学与矿物外加剂及微量组分（可溶碱）的添加将通过改变水化的液相特征而影响水化物的初始形成速率、形貌、分散性及其生长能力等，最终影响材料的体积稳定性。     

电阻率法研究早期水泥净浆孔结构的演变过程

采用无电极电阻率法原位连续监测3种水灰比（0.23、0.35和0.53）水泥净浆早期水化过程中电阻率的变化全过程,同时结合等温量热仪测试的水化程度,建立水泥净浆随时间发展过程中浆体电阻率与孔结构发展的定量关系。结果表明：根据电阻率及其微分曲线的变化规律可以把水泥水化过程分为4个阶段：溶解期、诱导期、加速期和减速期。水灰比越低,毛细孔隙率和收缩因子变小,曲折因子变大,致使浆体电阻率升高,而孔溶液电阻率却下降。     

高温煅烧石膏硅酸盐水泥早期水化产物的研究

利用DTA、XRD、IR、化学结合水和Ca（OH）2生成量测定等方法,研究了煅烧石膏、二水石膏对硅酸盐水泥早期水化过程的影响。结果表明：在水化龄期相同时,掺煅烧石膏水泥浆体中水化产物同掺二水石膏相比,Ca（OH）2生成量大;在一天前无AFt生成;结合水量在一天前前者高于后者,而一天后则相反。指出了煅烧石膏提高水泥强度的机理在于：由于煅烧石膏的溶解速度较低,在水泥水化初期（1d前）,存在于水泥中的铝酸盐相不能形成AFt,从而减缓了AFt对水泥水化的延缓作用,加速了整个熟料矿物相的水化,提高了水泥的强度。     

掺P2O5水泥基材料水化动力学研究

基于水化动力学模型,采用SEM、XRD和C-80Ⅱ型导热式微量热仪研究了硅酸盐水泥和掺P2O5硅酸盐水泥胶凝体系的水化特性和水化动力学,分析了P2O5对硅酸盐水泥水化机制的影响规律。研究结果表明,掺入P2O5后硅酸盐水泥的水化产物数量和尺寸显著减小。P2O5掺量为3．5％时,硅酸盐水泥熟料水化热总量降低32．6%,硅酸盐水泥的初凝和终凝分别被延缓1．10h和12．54h。掺入P2O5复合体系的水化机制与硅酸盐水泥类似,加速期由自动催化反应控制,减速期由自动催化和扩散反应双重反应控制,稳定期扩散反应占据主导。P2O5会增加硅酸盐水泥在加速期和减速期的水化反应阻力,减小稳定期的水化反应阻力。掺入P2O5后,水泥在加速期和减速期的表观活化能增加,稳定期表观活化能略有降低P2O5溶液环境有利于水泥熟料C3A的水化,延缓C3S和C2S的水化。     

单环芳烃型高效减水剂对水泥水化浆体微观影响

从水化热、水化产物、水泥浆体孔隙结构、微观结构变化4个方面,研究了单环芳烃型高效减水剂对水泥水化反应的影响.使用TAM Ai进行水化热测定表明,掺加单环芳烃型高效减水剂可延缓水泥初期水化和明显降低水化热,MRI分析表明同龄期的掺单环芳烃型高效减水剂水泥浆体与空白样相比孔隙总体积与总孔隙率都有增加的趋势,水泥浆体孔径分布变化不大.XRD、TG-DTA、SEM分析表明掺加单环芳烃型高效减水剂抑制水泥水化过程中水化产物Ca(OH)<,2>和水化硅酸钙产生,不影响水化产物与水化过程最终结果,掺加单环芳烃型高效减水剂使氢氧化钙、钙矾石与C-S-H等水泥水化产物细化.     

纤维水镁石对水泥硬化浆体力学性能的影响

采用SEM,XRD和电阻率测定仪研究了纤维水镁石对硅酸盐水泥硬化浆体的力学增强机理。结果表明,由于添加具有高拉伸强度和高杨氏模量的纤维水镁石,在水泥硬化浆体原有网络结构的基础上又建立了一个新的网络结构,改进了基体材料的界面结构,同时,纤维水镁石和水泥基体材料同属极性物质,在水化开始后水镁石纤维表面被水化产物C-S-H凝胶所覆盖,表明其具有良好的物理相溶性,这种双重作用提高了水泥硬化浆体的物理力学性能。     

海工水泥抗硫酸盐侵蚀机理

采用浸泡抗蚀性能试验方法 （K法）,对比研究了海工水泥和普通硅酸盐水泥的抗硫酸盐侵蚀性能。使用X射线衍射（XRD）、热重分析（TGA）、电子扫描（SEM）和电子计算机断层扫描（Computed tomography, CT）分析了两种水泥硫酸盐侵蚀前后矿物成分和微观结构的变化,进行了机理分析。结果表明：海工水泥抗硫酸盐侵蚀性能优于普通硅酸盐水泥,海工水泥在3%硫酸钠溶液中浸泡11个月后侵蚀系数为1.03,而普通硅酸盐水泥为0.22。海工水泥主要水化产物为水化硅酸钙、钙矾石和较少的氢氧化钙,其在3%硫酸钠溶液中浸泡后生成微量二水石膏,不会对基体产生破坏。除水化硅酸钙和钙矾石外,普通硅酸盐水泥的水化产物中有较多的氢氧化钙和单硫型水化硫铝酸钙,其在3%硫酸钠溶液中会生成大量的二水石膏和钙矾石,两者的结晶膨胀会引起基体开裂。     

水泥强度诱导提高方法研究

利用物理性能检测、水化放热测定和孔结构测定方法研究了通过掺加微细矿渣、高铝组分和水化硬化浆体诱导提高硅酸盐水泥强度的方法，并对其作用机理进行了探讨，试验表明，适量的微细高铝组分、矿渣组分及水化硬化浆体能够明显提高硅酸盐水泥强度。     

矿渣高钙灰复合水泥的水化程度研究

根据水化热、化学收缩、CH生成量和强度等实验结果，分析了由30％矿渣＋25％改性高钙灰＋45％52．5PⅡ水泥制备的42．5矿渣高钙灰复合水泥在不同龄期的水化程度。与普通硅酸盐水泥相比，由于高掺量的矿渣及改性高钙灰大幅度减少了熟料量，同时其火山灰反应消耗熟料的水化产物CH，水化产物组成和结构改变，水化热显著降低，早期化学收缩降低而后期化学收缩基本一致，不同龄期的CH生成量均显著降低，7d和28d的龄期强度接近，该复合水泥能够有效控制集中放热期的水化程度和优化水化产物组成，有利于改善耐久性。降低水胶比减少水化热、化学收缩和CH生成量，使水化度降低，但有利于水泥石结构的优化。     

混凝土水化热瞬态温度场数值计算过程中的水化放热规律及水化速率问题

在混凝土的施工中,为考虑水化热对施工和设计所造成的影响,根据有关规范、参考文献的实测数据及大体积混凝土空间有限元分析程序ＭＡＳＳＩＶＥ,研究了建筑工程中的混凝土水化热瞬态温度场计算过程中的水泥水化放热规律及水化速度,为数值计算分析提供了可靠的数学模型,可避免结构产生有害裂缝。     

Model Analysis of Initial Hydration and Strueture Forming of Portland Cement

The auto efficiently hydration heat arrangement and the non-contacting electrical resistivity device were used to test the thermology effect and the resistivity variation of Portland cement hydration. The structure forming model of Portland cement initial hydration was established through the systematical experiments with different cements,the amount of mixing water and the chemical admixture.The experimental results show that,the structure forming model of cement could be divided into three stages,i e,solution-solution equilibrium period,structure forming period and structure stabilizing period.Along with the increase of mixing water,the time of inflexion appeared is in advance for thermal process of cement hydration and worsened for the structure forming process.Comparison with the control specimen,adding Na_2SO_4 makes the minimum critical point lower,the flattening period shorter and the growing slope after stage one steeper.So the hydration and structure forming process of Portland cement could be described more exactly by applying thc thermal model and the structure-forming model.     

Model Analysis of Initial Hydration and Structure Forming of Portland Cement

The auto efficiently hydration heat arrangement and the non-contacting electrical resistivity device were used to test the therrnology effect and the resistivity variation of Portland cement hydration. The structure forming model of Portland cement initial hydration was established through the systematical experiments with different cements, the amount of mixing water and the chemical admixture. The experimental results show that, the structure forming model of cement could be divided into three stages, i e, solution-solution equilibrium period, structure forming period and structure stabilizing period. Along with the increase of mixing water, the time of inflexion appeared is in advance for thermal process of cement hydration and worsened for the structure forming process. Comparison with the control specimen, adding Na2SO4 makes the minimum critical point lower, the flattening period shorter and the growing slope after stage one steeper. So the hydration and structure forming process of Portland cement could be described more exactly by applying the thermal model and the structure-forming model.     

Influence of Calcium Sulfate State and Fineness of Cement on Hydration of Portland Cements Using Electrical Measurement

1 IntroductionThe calcium sulfate state includes gypsum, hemi-hydrate and anhydrite .Inthe modern Portland cement in-dustry,the gypsumis used as a setting retarder for reac-tion with C3A[1]. With the presence of gypsumin theformof CaSO4·2H2O,the gypsum dissolves and reactsprimarily with C3A and C4AF to form ettringite . Thisettringite isinitiallyformed with a veryfine-needle crystalstructure ,whichforms a diffusion barrier onthe surface ofthe cement . This coating avoids the unwanted fl…     

电阻率法研究磷及石灰对水泥凝结硬化的影响

用非接触式电阻率测试仪研究了不同含量的可溶磷及石灰对水泥早期水化过程中电阻率的影响。结果表明:可溶磷使得水泥早期的电阻率降低,水化进程推迟,且随着可溶磷含量的增加,电阻率呈逐步降低趋势;单独添加石灰对水泥早期水化影响较小;石灰中和可溶磷后可补偿可溶磷的对水化的延期危害,其电导率随时间变化规律与未添加磷、石灰的水泥基本一致。     

Effect of Fine Steel Slag Powder on the Early Hydration Process of Portland Cement

1 IntroductionSteel slag is the waste residue of fluxing mineralsused in the process of steel producing. Its dischargeamount is about 10 % of the production of steel . Steelslag hasn’t been utilized widely and effectively in a longperiod of time[1]. Hundreds of million tons of steel slagare deposited,andthe amount is still increasing withtensof milliontons every year .The deposited steel slag occu-pies great amounts of farmlands and induces serious en-vironment problems . The main chemical c…     

钢渣-矿渣-水泥复合胶凝材料的水化性能和微观形貌

通过测定矿渣和钢渣部分取代水泥构成的钢渣-矿渣-水泥复合胶凝材料(SBC-CCM)的物相组成和80h内的水化热,研究了SBC-CCM试样的微观形貌和水化性能,并用正交试验结果分析了SBC-CCM中钢渣-矿渣的最佳掺量和比例。结果表明:SBC-CCM的水化过程和水化产物的物相组成与硅酸盐水泥的相似,矿渣在水化早期参与反应,钢渣在水化早期呈惰性;SBC-CCM的80h水化放热量和放热速率均低于水泥相应的数值;正交试验结果表明水胶比对SBC-CCM强度的影响最显著,矿渣-钢渣的最佳质量比为2∶1。     

减缩剂对水泥基材料早期水化及收缩变形性能的影响

采用非接触式电阻率测定仪和半绝热实验方法分别研究了减缩剂对常温和半绝热条件下的水泥浆体早期水化的电阻率和温升的影响,对比研究了减缩剂对水泥砂浆在干燥条件和常温水中养护时的线性长度变化与强度发展情况的影响,应用五路裂缝测定仪研究了减缩剂在水泥砂浆中的抗裂效果.结果表明:在常温条件下减缩剂会延缓水泥早期水化,而在半绝热条件下则会加速水泥早期水化;减缩剂主要提高干燥环境下的水泥砂浆的抗裂性能,降低其线性收缩值与强度增长,推迟其约束收缩初始开裂时间,而对水中养护的砂浆无补偿收缩效应,因此不利于控制热裂缝.分析表明,减缩剂在水泥基材料中应用时不仅具有物理作用,而且具有化学作用.     

Hydration Characteristics of Sodium Sulfate Slag Cement System

The hydration characteristics by thermal analysis ( DTA ) were determined, and an isothermal calorimeter (IC) was used to study the pastes . The experimental results indicate: (1) The main hydration products of SSC are C-S-H( I ) gel with a low Ca/Si ratio, crystalline Thomsonite-type and AFt-type phases containing certain alkali cations; (2) No phases of the AFm-type and high alkaline Ca( OH)2 in SSC system could benefit the hydrated cements to improve its strength and durability; (3) Crystalline Thomsonite-type and AFt-type phases containing Na will greatly reduce free alkali and alleviate the harmness of alkali aggregate reaction ( AAR) in SSC system; (4) Similar to ordinary Portland cement( OPC), the hydration process of SSC could be classified into five stages : initial, induction, acceleration, deceleration and decay; (5) Regardless of the activator used, the apparent activation energy is higher with the increased slag in cement system, and the rising temperature could promote the hydration of SSC.