钢渣-矿渣复合水泥基材料3D打印性能

为了提高固体废弃物的资源化利用，探究利用钢渣制备3D打印水泥基材料的可行性，研究了钢渣、矿渣的质量比对复合水泥基材料流变特性、可打印性和力学性能的影响规律。结果表明，随着钢渣质量的增加，浆体的流动度和静态屈服应力增大，塑性粘度减小，可挤出性增强，变形率降低，同时抗压强度显著降低。通过Zeta电位测试发现，随着钢渣掺量的增加，Zeta电位绝对值变小，胶体颗粒间引力增大，导致静态屈服应力增大。而随着矿渣掺量的增加，浆体固含量增多，固体颗粒间摩擦加剧，产生了更多絮凝结构和网状结构，提高了浆体的塑性粘度。     

钢渣矿渣基全固废胶凝材料的水化反应机理

以钢渣、矿渣和脱硫石膏为主要原料制备胶凝材料,使用XRD、IR、TG-DTA和SEM等手段探究胶凝材料的水化反应机理,研究了钢渣掺量对全固废混凝土强度的影响,以及胶凝材料浆体的p H值和代表性离子浓度的变化规律。结果表明,当原料质量比为m(钢渣):m(矿渣):m(石膏)=30:58:12时,全固废混凝土3 d、7 d和28 d可以获得较优的强度。随着反应龄期的增加胶凝材料水化溶液的pH值先减小后增大,Ca2+浓度和硅(铝)溶解物的早期浓度较低,后期浓度有所提高。在脱硫石膏的激发下钢渣和矿渣相互促进水化,水化产物以钙矾石(AFt)和水化硅酸钙(C-S-H)凝胶为主。在反应的后期,水化产物的数量迅速增加。针棒状的AFt晶体穿插在C-S-H凝胶内,使硬化浆体的结构更加致密。     

碳化水泥-钢渣复合胶凝材料的强度和微观结构

研究了不同碳化方式、钢渣掺量和促进剂对水泥-钢渣微粉复合胶凝材料力学性能和微观结构的影响。结果表明:碳化对试样的早期强度提高有明显的促进作用,但对后期强度作用较小;碳化反应发生在试样早期水化完成之前,碳化越早,试样强度越高。采用促进剂的试样强度提高明显,碳化处理3d抗压强度较不加促进剂的空白样提高了12.0%,处理28d抗压强度提高了29.0%。促进剂对水泥-钢渣微粉复合胶凝材料碳化产物CaCO_3的形貌具有一定的影响。     

膨润土对泡沫膏体充填材料孔结构及强度的影响

通过添加膨润土成功制备了孔径分布均匀的泡沫膏体充填材料,利用X射线衍射仪和扫描电镜分析了膨润土掺加前后泡沫膏体充填材料的水化产物及孔隙结构,研究了膨润土掺量对泡沫膏体充填材料28 d抗压强度的影响。结果表明,膨润土的掺加提高了气泡稳定性,有利于泡沫的引入,易于制备较低干密度的泡沫膏体充填材料,但膨润土对泡沫膏体充填材料水化产物的生成有一定抑制作用;在水料比为0.7~0.8时,掺加2.0%~4.0%(质量分数)膨润土可使微细孔含量明显增多,气孔孔径分布集中,比较均匀的孔隙结构改善了泡沫膏体充填材料的强度,28 d抗压强度可达0.50~0.73 MPa,满足煤矿充填使用要求。     

大掺量钢渣微粉-水泥碱激发特性

为解决钢渣微粉在水泥基复合材料中掺配比例较低的问题，采用力学性能测试、 XRD、 SEM、 FTIR等方法研究激发剂种类、掺量等对钢渣微粉-水泥胶凝材料力学强度和微观结构的影响。结果表明：碱性激发剂可提高钢渣微粉水化速度、增大复合胶凝材料抗压强度，但激发剂种类对胶凝材料激发效果具有差异性；碳酸钠与三乙醇胺复合激发后效果显著，3、 7、 28 d龄期的最佳强度与未掺加激发剂实验组的相比分别提高47%、 72%、 69%;激发剂对复合胶凝材料浆体水化产物种类没有影响；三乙醇胺具有悬浮稳定效应以及降低溶液表面张力的能力，与碳酸钠的强腐蚀效应作用在钢渣微粉水泥体系中协同强化水化反应，使复合胶凝体系中生成更多的水化产物并且相互交织成复杂密实的空间结构。     

化学激发对煤气化渣-水泥体系抗压强度影响机理研究

针对煤气化渣大量堆存造成的环境污染和固废资源浪费的问题,本工作采用化学激发方法来激发煤气化渣活性,探究不同激发剂对煤气化渣?水泥体系抗压强度的影响.试验选取硫酸盐类、碱类和聚合盐类激发剂,确定最优激发剂种类和掺量;通过扫描电镜(SEM)、X射线衍射(XRD)和热重分析(TG)等微观手段,研究不同激发剂对煤气化渣?水泥体系水化产物的影响.结果表明,硫酸盐类最优激发剂为硫酸钠,最佳掺量为2.5％,试样3 d、28 d抗压强度增长率分别达14.3％、3.4％;碱类最优激发剂为氢氧化钙,最佳掺量为0.5％,试样3 d、28 d抗压强度增长率分别达18.4％、1.8％;聚合铝最佳掺量为2.0％,试样3 d、28 d抗压强度增长率分别达24.0％、3.3％.加入激发剂后试样早期抗压强度均得到提高,微观特征表明试样水化程度加深,且有助于钙矾石和凝胶体等水化产物的生成,提高试样强度,为煤气化渣在水泥基材料中的应用提供了理论依据.     

粉煤灰基固废胶凝材料流变特性机理研究

为研究适用于高浓度废弃尾矿砂浆充填体的胶凝材料，通过扩展度等试验检测不同粉煤灰掺量下砂浆流变特性，并分析试验方法的适用性；通过检测砂浆微观性质探究粉煤灰基胶凝材料作用机理。结果表明：扩展度与L管模型试验的相关性为0.985,说明扩展度可作为L管的预试验，协同表征砂浆流变性能；掺入10%粉煤灰的砂浆屈服应力降低了13.06%～24.74%,3 d强度提升了40%,7 d强度提升了9.9%,使固废综效得以充分发挥；随粉煤灰含量逐渐增加，浆液离子浓度逐渐降低，导致胶凝颗粒间斥力增加，颗粒更为分散；同时10%掺量粉煤灰的浆液3 d水化放热累计量261.696 J/g,提升了2.9%,孔隙率15.15%降低了4.02%,即粉煤灰的“滚珠”特性一定程度上改善了流动性并提升了硬化体强度。     

微胶囊在修补砂浆中延迟释放早强剂的应用及性能分析

为使修补砂浆具备合适的凝结时间和较高的早期强度,将无水硫酸钠经微胶囊包覆后掺入到修补砂浆中,进而研究微胶囊对修补砂浆凝结时间、抗压强度、水化进程、水化产物以及水化早期钙矾石生长速率的影响。结果表明,微胶囊的掺入显著延长了浆体的凝结时间,缩短了其初凝、终凝的时间间隔,且对砂浆的早期强度无明显影响;使浆体的水化速度在开始的3 h内处于一个较低的水平,随后其水化速度增大,并最终与掺等量无水硫酸钠浆体的水化程度达到相当水平。另外,掺微胶囊的浆体早期钙矾石的生长速率处在一个较高的水平,且水化4 h后能达到与掺等量无水硫酸钠体水化产物相当的致密度。     

速凝剂对低水胶比浆体早期水化与微观结构的影响

低水胶比、高胶凝材料掺量的超高性能混凝土(UHPC)在常温养护条件下易产生凝结硬化不及时的问题。为促进UHPC在隧道初支、工程结构快速修复中的推广应用,拟采用有碱速凝剂(NA)和无碱速凝剂(AS)提升低水胶比浆体的早期凝结硬化速率。本工作通过水化热、水化溶出离子浓度、凝结时间和抗压强度试验研究速凝剂作用下低水胶比浆体的早期水化行为及凝结硬化规律,采用X射线衍射、SEM形貌观察和EDS能谱等手段对水化产物物相组成及微观结构演变规律进行了分析。结果表明,速凝剂的掺入加快了低水胶比复合胶凝材料浆体的早期水化速率,同时也促进了浆体的凝结硬化;NA对UHPC的促凝效果优于AS,其中NA-2%的1 d抗压强度为53.3 MPa, 28 d强度比为94.9%,而AS-4%的1 d抗压强度为38.9 MPa, 28 d强度比为92.3%;速凝剂促使低水胶比浆体快速生成大量水化产物,进而提高了浆体早期微观结构的致密性,且水化产物物相组成受速凝剂类型的影响较为显著。     

碳酸化钢渣和矿渣作硅酸盐水泥混合材水化性能研究

通过对钢渣碳酸化前后的硅酸盐相提取及水化放热性能和将碳酸化钢渣和矿渣作为混合材的硅酸盐水泥的胶砂强度和水化产物种类的测定,以及对它们微观形貌的观察,研究了碳酸化钢渣对胶凝体系水化性能的影响.结果表明,碳酸化使钢渣中硅酸盐相的含量由47.06％下降至14.38％;碳酸化促进了钢渣的早期水化,抑制其后期水化;在配比相同的条件下,碳酸化钢渣-矿渣-硅酸盐熟料体系试样的3、28d抗压强度较未碳酸化钢渣-矿渣-硅酸盐熟料体系试样的高;碳酸化生成的CaCO3促进了熟料的水化;碳酸化钢渣促进了胶凝体系中AFt的生成,且生成水合碳铝酸钙.     

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.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

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.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

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.