混凝土ITZ性能及其对混凝土性能影响研究

界面过渡区(ITZ)是指硬化水泥浆(水泥基相)和骨料(分散基相)之间的约50μm的薄层部分。基于当前国内外学者对混凝土界面过渡区性能的大量研究成果,发现材料组分和环境作用对ITZ的力学性能和微观结构影响较大;ITZ微观结构变化影响混凝土材料宏观性能;对于ITZ的改性,目前通用的处理方式是掺合料和外加剂的掺入、对骨料进行预处理以及改善制作工艺。本文在分析混凝土界面过渡区的各项研究现状基础上提出相应的建议和展望。     

水泥基复合材料界面对材料宏观性能的影响

从力学性能、传输性能和收缩性能3个角度阐述了界面过渡区(ITZ)对混凝土宏观性能的影响．其中力学性能主要从强度、刚度以及断裂力学性能3个方面,传输性能主要从扩散性能与渗透性能2个方面进行考虑．探讨了在多因素交互作用下,有关界面研究方面存在的不足．     

界面过渡区对混凝土性能的影响及其改善措施

本文从混凝土界面过渡区的微观结构和形成机理出发,较全面地分析了影响界面过渡区强度的诸因素和过渡区对混凝土力学性能的影响,并在此基础上提出了改善过渡区结构和性能的有效措施。     

细观层次混凝土动态性能的影响因素研究综述

混凝土是三相复合材料,其宏观力学特性与界面过渡区(ITZ)有关。本文总结了ITZ力学性能的试验与数值模拟研究现状,并就ITZ影响混凝土宏观动态力学性能的参数进行了归纳。结果表明,由于缺乏ITZ动态力学性能的试验数据,目前基于细观数值模拟技术研究混凝土试样动态力学性能的成果均是在一定假设条件下开展的。然而,这些假设条件的可靠性有待相应试验数据的验证。经过对ITZ的几何和力学影响因素的总结,指出针对ITZ影响混凝土宏观动态力学性能问题中尚待深入研究的内容。     

绿色高性能充填材料界面过渡区研究

界面过渡区（Interracial Transition Zone，ITZ）是混凝土中最薄弱的环节，其结构和牯结性能，直接影响到混凝土整体的强度、刚度和耐久性。而改善界面过渡区比较有效的方法就是掺加矿物掺合料，本文以大量掺加粉煤灰、煤矸石等工业废渣为技术手段，制备了一种绿色高性能充填材料，以强度、坍落度、收缩值为指标，对其工作性能和耐久性能进行试验与评价，并运用SEM、EDS对充填材料界面过渡区微观结构进行了研究。     

碳化再生粗骨料环保型超高性能混凝土的制备

提出了一种再生建筑废弃物的高效利用方法,并以此制备了生态型超高性能混凝土（UHPC）.基于改进的颗粒堆积模型（MAA模型）,开发了最大粒径为4.75 mm的碳化再生粗骨料（CRCA）超高性能混凝土（CRCA-UHPC）,评估了CRCA对UHPC 宏观性能及纳微观结构的影响.结果表明：将CRCA掺入 UHPC中可以改善UHPC的力学性能和耐久性能,降低UHPC的自收缩,优化骨料与基体间的界面过渡区（ITZ）.     

冻融作用下岩石-混凝土界面损伤研究进展

由于冻融作用,寒区混凝土支护工程的安全性和稳定性越来越受到重视,而岩石-混凝土界面的强度性能是支护结构发挥功能的关键。文中主要对岩石-混凝土界面冻融损伤演化规律、界面冻融损伤影响因素、界面过渡区（ITZ）强度弱化机理这3个方面进行了综述,分析了目前研究的不足,并提出了改进措施和未来展望,为此方向的相关研究提供一定的参考价值。     

混凝土三维细观分析中界面过渡区的网格划分方法

界面过渡区(ITZ)网格划分是混凝土三维细观分析研究中的关键问题。通常只考虑砂浆和骨料两相结构;少数研究用格构模型或背景网格法确定ITZ单元,所得的ITZ单元尺寸与实际不符。提出一种基于已有的砂浆和骨料两相网格生成约50μm厚的五面体ITZ单元的方法,使得建立的混凝土三相细观结构更接近实际。所得的三维细观结构为模拟混凝土的力学性能打下了基础。     

粉煤灰对玻化炉渣路面混凝土界面微观结构改善影响研究

探究粉煤灰对玻化炉渣混凝土工作性能与力学性能的影响,采用显微硬度、扫描电镜(SEM)和X射线能谱仪(EDS)等微观手段对玻化炉渣混凝土界面展开研究,分析粉煤灰对玻化炉渣骨料-水泥石的界面过渡区作用机理。研究表明:玻化炉渣混凝土中粉煤灰最佳掺量为10～20 kg/m3。掺入粉煤灰能有效改善玻化炉渣混凝土界面过渡区结构,降低界面区钙硅比,提高界面区显微硬度,降低界面过渡区CH晶体与AFt晶体的富集,促进C-S-H凝胶的生成,降低孔隙率,提高界面过渡区密实程度,进一步提高玻化炉渣混凝土的力学性能和工作性能。     

粉煤灰特性及其在绿色高性能混凝土中的试验研究

主要分析了粉煤灰的组成、结构与作用机理,介绍了各国有关粉煤灰的标准,研究了粉煤灰高性能混凝土的力学性能、抗渗性能及其微观形貌。结果表明,绿色高性能混凝土中掺入粉煤灰,在满足和易性和力学性能的基础上,可以提高其耐久性;掺入粉煤灰可以显著改善混凝土中骨料与浆体的界面过渡区,有利于提高其抗渗性能和力学性能。     

Fire performance assessment of HPLWC hollow core slabs through full-scale furnace testing

High-Performance Light-Weight Concrete (HPLWC) is used for many structural applications when superior strength and low self-weight of the structural components are required. Among these applications there are thin floor structures, like hollow core slabs, that require characteristics of lightness, relatively high resistance and superior durability. Although the fire performance of normal strength concrete hollow core slabs has been extensively studied, the behavior of HPLWC hollow core slabs has not been suitably investigated.The paper reports the results of two full-scale furnace tests on HPLWC hollow core slabs. Each of them involved one panel with an applied load and one without load. The evolution of temperature inside the slabs was measured along with the load bearing capacity under fire conditions. During the first test severe spalling occurred in the loaded slab while during the second one, performed on slabs cured for some months under dry conditions, spalling did not occur. Finite elements simulations were also carried out in order to support the interpretation of the experimental results. Experimental and numerical investigations gave insight into the fire performance of HPLWC hollow core slabs and highlighted the influence of dry curing conditions in reducing the spalling and increasing the fire resistance.     

Predicting performance of impact hammers from rock quality designation and compressive strength properties in various rock masses

Predicting the performance of the impact hammers is one of the major subjects in determining the economics of the underground excavation projects in which they are utilized. Therefore, researchers have been attracted to developing performance prediction models for these machines. Physical and mechanical properties of rocks have been used to estimate the performance of impact hammers over the last few decades. In this study, the instantaneous breaking rate (IBR, m³/h) of an impact hammer used in construction of Levent-Hisarüstü metro tunnel (Istanbul) is recorded in detail. Sixty rock samples are obtained from tunnel route during the excavation of which the machine is employed. Physical and mechanical property tests are performed on the obtained samples. A data set including uniaxial compressive strength (UCS), rock quality designation index (RQD), Brazilian tensile strength (BTS), density (ρ), Schmidt hammer hardness (SHH), Shore scleroscope hardness (SSH), Cerchar abrasivity index (CAI), and IBR is formed. Regression analysis techniques are applied to the created data set in order to develop a performance prediction model. The investigation results in a model that can predict IBR based on UCS, RQD, and the output power of the impact hammer. The proposed model passes both F-test and t-test at 0.95 confidence level. The soundness of the model is successfully tested against two formerly developed models. Covering a wide range of application and requiring only two of the most common and versatile rock properties as input parameters are the other advantages of the suggested model.     

Compression tests of welded section columns undergoing buckling interaction

This paper describes a series of compression tests performed on welded H-section and channel section columns fabricated from a mild steel plate of thickness 6.0 mm with nominal yield stress of 240 MPa. The ultimate strength and performance of the compression members undergoing nonlinear interaction between local and overall buckling were investigated experimentally and theoretically. The compression tests indicated that the interaction between local and overall buckling had a significant negative effect on the ultimate strength of the thin-walled welded steel section columns. The Direct Strength Method (DSM), which was newly developed and adopted as an alternative to the effective width method for the design of cold-formed steel sections recently by NAS (AISI, 2004), was calibrated by using the test results for application to welded steel sections. This paper confirms that the Direct Strength Method can properly predict the ultimate strength of welded section columns when local buckling and flexural buckling occur simultaneously or nearly simultaneously.     

屈曲交互作用下焊接截面柱的抗压试验

对焊接H形和槽形截面的柱进行了一系列压力试验,这些柱采用厚度为6·0 mm,名义屈服应力为240 MPa的软钢板制成。从理论上和试验中对这些受压构件在非线性局部和整体屈曲交互作用下的极限强度和性能进行了研究。压力试验表明,局部和整体屈曲交互面对薄壁焊接钢柱截面有较大的负面影响。近期发展起来的DSM方法,对冷加工钢截面的设计,可作为有效宽度法的备选方法,最近已由NAS( AISI ,2004)提出,并由焊接钢截面的试验结果进行了校验。证明了当局部屈曲和弯曲同时或者近乎同时发生时,可采用直接强度法预测焊接截面的极限强度。     

Performance assessment of water supply and wastewater systems

This paper addresses the issue of performance assessment in water and wastewater systems by reviewing two of the tools that are available to the companies operating in this field: systems of performance indicators and technical performance assessment through simulation. The paper focuses on a technical performance evaluation framework and its application to wastewater systems. The assessment is carried out through the application of utility functions to the network's elements, and the production of performance-oriented graphs that yield concise and informative views about the system's behaviour. Two case studies involving a combined sewer system and a separate domestic system are presented in order to illustrate the method.     

绿色高性能混凝土—混凝土的发展方向

本文从合理利用资源，保护人类赖于生存的自然环境不遭破坏并实现可持续发展的战略高度出发，论述了混凝土目前及今后的发展方向，提出了发展“绿色高性能混凝土（ＧＨＰＣ）的观点。     

一种砂浆外加剂的研究

在设计基础砂浆配合比的基础上,通过调节A、B、C3种外加剂的用量,大大改善了砂浆的性能,从而研究出一种适用于普通砂浆的复合砂浆外加剂。此种外加剂可以大大改善砂浆的操作性、保水性,并能大大提高砂浆强度。     

Prediction of roadheader performance by artificial neural network

Performance prediction of the roadheaders is one of the main subjects in determining the economics of the underground excavation projects. During the last decades, researchers have focused on developing performance prediction models for roadheaders. In the first stage of this study, the performance of a roadheader used in Kucuksu sewage tunnel (Istanbul) was recorded in detail and the instantaneous cutting rate (ICR) of the machine was determined. The uniaxial compressive strength (UCS) and rock quality designation (RQD) are used as input parameters in previously developed empirical models in order to point out the efficiency of these models, and the relationships between measured and predicted ICR for different encountered formations. In the second stage of the study, Artificial Neural Network (ANN) technique is used for predicting of the ICR of the roadheader. A data set including UCS, RQD, and measured ICR are established. It is traced that a neural network with two inputs (RQD and UCS) and one hidden layer can be sufficient for the estimation of ICR. In addition, it is determined that increase in number of neurons in hidden layer has positive optimizing on the performance of the ANN and a hidden layer larger than 10 neurons does not have a significant effect on optimizing the performance of the neural network. Furthermore, probability of memorizing is being recognized in this situation. Based on this study, it is concluded that the prediction capacity of ANN is better than the empirical models developed previously.     

铜管在建筑冷热水系统中的应用

介绍了铜管的应用情况、优点、施工安装方法及经济性能 ,说明了铜管在建筑冷热水系统中应用的竞争力。     

Early-warning performance monitoring system (EPMS) using the business information of a project

An early-warning performance monitoring system (EPMS) is proposed to objectively measure and monitor the performance of a project for early detection of inherent poor performance problems. The EPMS is built based on project progress data and consists of a database of business information, an optimized theoretical model used as a performance measurement baseline, and an index for monitoring and forecasting the performance. By monitoring the performance through an application of the EPMS to the Korean construction project, the quarterly variation of index was found to differ by project type. These results could explain the environmental changes in the project execution. Therefore, the EPMS is expected to be an alternative for objective performance monitoring and forecasting while applying the existing methods is difficult because of the limited available data on performance indicators. The development procedures may also be useful to researchers interested in approaches to quantitatively analyze trends in various industries.