缓凝剂对掺UNF-5高C3S水泥水化的调控

采用流动度、电阻率和水化热等实验方法,研究了缓凝剂对掺定量UNF-5高C3S水泥浆初始水化历程的调控,着重研究了3种缓凝剂与UNF-5的叠加效应在高C3S水泥浆初始水化历程中产生的主要现象,以及这些现象对改善UNF-5与高C3S水泥的相容性的影响.实验表明:在浆体流动性方面,葡萄糖酸钠和多聚磷酸钠与UNF-5叠加时存在一个最佳掺量,柠檬酸出现负效应.在一定的温度范围内,叠加前后水泥浆体的流动度均随温度的增加而增大.缓凝剂对早期C3A水化的作用效应显著影响含UNF-5水泥浆体的流动度与早期电阻率之间的关系.缓凝剂的参与延缓水泥浆体结构的形成,放热峰削弱且得以宽化,有效解决放热集中的问题.对水泥浆体结构形成的延缓能力,葡萄糖酸钠最强,多聚磷酸钠次之,而柠檬酸相对最弱.     

钙矾石的长期稳定性

本文通过对一组在 2 0℃水中养护了 15年的矿渣硅酸盐水泥净浆进行XRD分析 ,对水泥浆体中钙矾石的长期稳定性及其机制进行了探讨。结果表明 :在水泥浆体中 ,钙矾石向单硫型水化硫铝酸钙转变的速度十分缓慢 ;水泥中含铝 (铁 )相含量 ,尤其是C3 A含量 ,是影响钙矾石长期稳定性的重要因素 ,C3 A含量增加 ,其稳定性明显下降 ;钙矾石长期稳定性并不仅仅取决于体系中含铝 (铁 )相与SO3 摩尔比 ,还取决于动力学因素     

掺杂TiO2对C4A3(-S)形成及水化性能的影响

研究了掺杂TiO2对C4A3(S)矿物的形成及水化性能的影响在1300℃保温1 h,TiO2稳定过渡产物CA的作用使C4A3(S)的形成速度降低;在1300℃保温3 h,适量的TiO2增加C4A3(S)的形成量;TiO2的含量过高,使C4A3(S)的形成量减少并出现CT(CaTiO3).掺杂TiO2使C4A3(S)以四方晶系的结构存在.掺杂提高了C4A3(S)的水化反应活性,其原因是晶体结构的畸变.     

焙烧Mg-Al水滑石水泥浆涂层对钢筋氯离子腐蚀的缓蚀性能

本工作研究了焙烧Mg-Al水滑石(LDO)水泥浆涂层对钢筋氯离子腐蚀的缓蚀性能。将焙烧Mg-Al水滑石材料添加到水泥浆中制备了复合水泥浆涂层,并涂覆在钢筋表面。由等温吸附实验、线性极化测试(LP)、电化学阻抗谱测试(EIS)研究了在混凝土模拟孔溶液中复合水泥浆涂层对钢筋氯离子腐蚀的缓蚀性能;此外,采用X射线衍射仪(XRD)和傅里叶变换红外光谱(FT-IR)检测了吸附实验前后水泥浆的物相变化,探讨了焙烧Mg-Al水滑石水泥浆涂层对钢筋氯离子腐蚀的缓蚀机理。结果表明,LDO的掺入能显著提高水泥浆体对氯离子的饱和吸附量,且随着LDO掺量的增加,复合水泥浆涂层的综合阻锈效果增强。复合LDO涂层缓释机理归因于层状结构的复原使其能有效地吸附氯离子并释放氢氧根离子,从而能有效阻止氯离子的侵蚀。     

固井水泥石孔隙结构演变及力学强度发展规律

本研究以水泥水化数值模拟模型HYMOSTRUC3D为基础,建立了固井水泥浆水化模型,获取了固井水泥石的CH含量和抗压强度,并分别与实验所得固井水泥石的CH含量和抗压强度进行对比,模拟结果与实验结果的偏差分别为0.7％～8.7％和0.5％～10.7％,结果吻合较好,验证了所建模型的准确性.然后,基于所建模型探究了水泥矿物成分(C3S、C2S、C3A和C4AF)、水化产物(C-S-H和CH)、孔隙率、孔径分布等随水灰比和水化龄期的变化关系,并在Para View中重建了水泥石三维微结构.此外,分别采用Ryshkewitch方程、Schiller方程和二次线性方程探讨了水泥石的抗压强度与总孔隙率、毛细孔隙率的变化关系.研究结果表明:(1)水泥水化过程中,固井水泥石的孔隙率逐渐减小,孔径分布逐渐变窄,抗压强度逐渐增大;随水灰比的增大,孔隙率相应增大,孔径分布范围变宽,抗压强度减小.(2)水泥石的抗压强度与总孔隙率、毛细孔隙率呈负相关,采用Ryshkewitch方程、Schiller方程和二次线性方程分别拟合水泥石的抗压强度与总孔隙率、毛细孔隙率的关系,拟合决定性系数R2分别为0.92、0.85、0.91和0.97、0.95、0.97.(3)相比于Schiller方程和二次线性方程,Ryshkewitch方程在研究水泥石抗压强度与总孔隙率、毛细孔隙率的关系时更具普适性,毛细孔隙率是决定抗压强度的主要因素.(4)可采用y=191.5e-0.074x开展固井水泥浆抗压强度发展和毛细孔隙率变化规律的预测和研究.     

弯曲荷载对硬化水泥浆体和砂浆碳化过程的影响

研究了弯曲荷载对硬化水泥净浆和砂浆试体碳化过程的影响.结果表明:弯曲荷载会加速水泥浆体和砂浆的碳化过程,在弯曲荷载作用下水泥浆体和砂浆的碳化动力学过程可用式x=C0eaηtb描述,其中b值均接近1/2;碳化时间对砂浆碳化深度的影响略小于对水泥浆体的影响,而应力水平对水泥浆体和砂浆碳化的影响大致相同.     

普鲁兰多糖对水泥净浆性能的影响

主要研究一种新型微生物多糖——普鲁兰多糖(Pullulan)对新拌水泥浆体性能的影响,对比分析了不同掺量的普鲁兰多糖对水泥净浆标准稠度用水量、凝结时间、流动度和Zeta电位的影响,以及对硬化水泥浆体力学性能的影响.研究表明:普鲁兰多糖增大了水泥浆体标准稠度用水量,延长了水泥的凝结时间;随着普鲁兰多糖掺量的增加,新拌水泥浆体的初始流动度降低,但随着时间的延长,流动度不降反升;普鲁兰多糖的掺入降低了水泥浆体的Zeta电位,0～13 min内,Zeta电位值极度不稳定,然后趋于平稳状态;普鲁兰多糖与减水剂(PC)复掺后,随着普鲁兰多糖掺量的增加,水泥浆Zeta电位发生了复杂的变化过程;普鲁兰多糖对硬化水泥浆体的抗压强度无明显不利影响.     

复合盐类侵蚀对硅酸盐水泥固化氯离子影响研究

研究了硫酸盐、碳酸盐和硝酸盐与氯盐复合侵蚀下硅酸盐水泥固化氯离子性能,采用水溶法测定了水泥净浆中自由氯离子含量并计算得出其氯离子固化率,对试样进行了XRD物相分析以及其水溶液的pH值测定。结果表明,水泥浆体的氯离子固化率随水化龄期的增长而增加;随氯离子浓度增大,水泥浆体中F盐的生成量增加,其氯离子固化率先增大后减小。随硫酸盐和碳酸盐浓度增大,水泥浆体的氯离子固化率均降低,硫酸盐的降低程度稍微比碳酸盐大。硫酸盐和碳酸盐通过结合AFm分别生成钙矾石(3CaO·Al_2O_3·3CaSO_4·31H_2O)和单碳硫铝酸钙(3CaO·Al_2O_3·CaCO_3·12H_2O)提高了水泥浆体的pH值,减少了F盐的生成量。硝酸盐对水泥浆体的氯离子固化率和F盐的生成没有影响。     

Fe—C—Cr—V—B系高铬堆焊合金的显微组织及耐磨性

采用药芯焊丝埋弧堆焊方法制备含有C 1 2%～1 8%(质量分数,下同),Cr 15%～20%,V 2 0%～3 0%,B 0%～1 0%的高铬堆焊合金.借助光学显微镜、扫描电镜和X射线衍射等分析手段,研究其显微组织及碳化物分布形貌,结果表明:其显微组织由α-Fe+γ-Fe+(Fe, Cr)7C3+ (Fe, Cr)3C+Fe3(C, B)+B4C等组成,加入B4C可显著细化该堆焊合金晶粒,降低α-Fe,γ-Fe基体组织的Cr,V等合金元素的固溶量,使碳化物(Fe, Cr)7C3数量增加且呈弥散分布.另外,考察了B4C含量对高铬堆焊合金硬度及耐磨性的影响,耐磨粒磨损实验结果表明其相对磨损系数是H25Cr3Mo2MnV堆焊合金的6～17倍,其中碳化物颗粒四周均匀分布的α-Fe等基体组织使其可承受较大的磨粒冲击而不脱落.     

基于Rietveld/XRD(内标法)水泥浆体物相演变定量表征与非晶定量公式修正

基于Rietveld/XRD精修方法,借助GSAS-EXPGUI软件,研究既定水化龄期普通硅酸盐水泥浆体物相组成的定量表征,并结合Ca(OH)2的热分析定量结果以及熟料矿物与自由水的量化匹配关系研究Rietveld定量结果的可靠性。研究结果表明,干燥水化样品中Ca(OH)2的Rietveld定量结果与热分析定量结果具有较好的一致性,当水化1 d、3 d、7 d和28 d龄期时,其绝对误差分别为1. 2%、0. 7%、0. 3%和0. 8%,且随着水化龄期的延长,样品的相对误差显著降低。结合水泥浆体物相演变的Rietveld定量表征发现,熟料矿物的消耗程度与自由水的消耗程度存在较好的线性相关性(相关系数R2=0. 996),反映了其Rietveld定量表征具有较高的可靠性。在此过程中,提出了基于内标法改进型的非晶相定量公式,并建立了水泥浆体自由水与相应干燥样品化学结合水的数学关系。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。