Efficiency of mineral admixtures in mortars: Quantification of the physical and chemical effects of fine admixtures in relation with compressive strength

This work is the fourth part of an overall project the aim of which was the development of general mix design rules for concrete containing different kinds of mineral admixtures. The two first parts presented the separation and quantification, by means of an empirical model based on semi-adiabatic calorimetry measurements, of the different physical effects responsible for changes in cement hydration (short terms) when chemically inert quartz powders were used in mortars. Part three dealt with an intensive experimental program, presenting and commenting more than 2000 compressive strength measurements. This program concerned 1 day to 6 months old mortars containing up to 75% of inert and pozzolanic admixtures. All these compressive strength results are analyzed in this fourth part and the influence of three effects, namely dilution, heterogeneous nucleation and the pozzolanic effect, are discriminated and quantitatively evaluated. An efficiency concept is proposed in order to take into account the effect of mineral admixture in mortars from both the physical and chemical points of view. It uses an efficiency function ξ(p) that has notable properties: it is independent of time, independent of fineness and independent of the type of mineral admixture.     

确定S_(BOS)对称序列左右界顶点子集的一个通项公式

根据本文作者之一(1991)提出的S_(BOS)相邻逻辑对称序列的性质,给出确定S_(BOS)对称序列左右界两顶点子集的一个通项公式。这对于利用“对跳定界搜索”法快速实现S_(BOS)对称序列,提供了一个选择定界范围和实用算法的依据。     

人工辅助生殖与法律调控

国内外人工辅助生殖技术主要应用于人工授精,体授精无性生殖等领域。人工辅助技术应用的结果产生了伦理、道德和法律问题,冲击了现有的道德规范和法律规范。文章就人工辅助对道德,法律产生的影响做出剖析,并提出积极的法律调控的建议。     

基于MATLAB的辅助变量法参数辨识与仿真

本文介绍了参数辨识中辅助交量法的基本原理以及Matlab系统辨识工具箱中参数辨识主要功能函数，并通过实例分析该工具箱在参数辨识、系统仿真中的应用。     

Monitoring and modelling the early age and hardening behaviour of eco-concrete through continuous non-destructive measurements: Part I. Hydration and apparent activation energy

A recent scientific and industrial interest has been brought to combine multiple supplementary cementitious materials (SCM) in large quantities in concrete binders. The growing use of binary, ternary or quaternary cement binders calls for the development of simple, efficient and accurate experimental means to characterise and predict the behaviour of such concretes. Continuous non-destructive testing constitutes a major opportunity since it generally consists in simple test setup requiring low human interaction. In this study, isothermal calorimetry and ultrasonic pulse velocity (compression and shear waves) are performed on various concrete compositions with massive incorporation of limestone filler and blast-furnace slag. Indeed, these two additions present interesting complementary effects and positive synergies in terms of fresh properties, mechanical behaviour and durability potential. The hydration process of these concretes is investigated, and a new model is presented for representing the hydration degree of SCM-based binders. Then, the apparent activation energy is studied through tests at various temperature. Ultrasonic measurements are shown to provide a good alternative to isothermal calorimetry for the monitoring of the apparent activation energy of concrete during the first days of hydration.     

Model for practical prediction of natural carbonation in reinforced concrete: Part 1-formulation

A model is proposed for prediction of natural carbonation in reinforced concrete (RC) structures, and is potentially applicable to existing and new RC structures. The major components of the model comprise mathematical functions applied to predict the influence of concrete composition, and environmental factors on natural carbonation.This paper introduces the model concept and explains its structure including derivation, optimization and calibration. Over 163 data sets taken from a 10-year carbonation study were used in the model development and calibration. Only the experimental data that were based on outdoor natural exposure environment were employed in this research. Also in this study, the proposed model is compared with fib-Model Code 2010 using carbonation predictions generated from 346 data sets involving real world, highway structures. It is shown that the proposed model is comparably accurate and involves mainly basic tests with no major anticipated costs.     

Analysis for a two-dissimilar-component cold standby repairable system with repair priority

In this paper, a cold standby repairable system consisting of two dissimilar components and one repairman is studied. Assume that working time distributions and repair time distributions of the two components are both exponential, and Component 1 has repair priority when both components are broken down. After repair, Component 1 follows a geometric process repair while Component 2 obeys a perfect repair. Under these assumptions, using the perfect repair model, the geometric process repair model and the supplementary variable technique, we not only study some important reliability indices, but also consider a replacement policy T, under which the system is replaced when the working age of Component 1 reaches T. Our problem is to determine an optimal policy T^? such that the long-run average loss per unit time (i.e. average loss rate) of the system is minimized. The explicit expression for the average loss rate of the system is derived, and the corresponding optimal replacement policy T^? can be found numerically. Finally, a numerical example for replacement policy T is given to illustrate some theoretical results and the model's applicability.     

A single chart with supplementary runs rules for monitoring the mean vector and the covariance matrix of multivariate processes

The MRMAX chart is a single chart based on the standardized sample means and sample ranges for monitoring the mean vector and the covariance matrix of multivariate processes. User’s familiarity with the computation of these statistics is a point in favor of the MRMAX chart. As a single chart, the recently proposed MRMAX chart is very appropriate for supplementary runs rules. In this article, we compare the supplemented MRMAX chart and the synthetic MRMAX chart with the standard MRMAX chart. The supplementary and the synthetic runs rules enhance the performance of the MRMAX chart.     

Supplementary cementitious materials

The use of silica rich SCMs influences the amount and kind of hydrates formed and thus the volume, the porosity and finally the durability of these materials. At the levels of substitution normally used, major changes are the lower Ca/Si ratio in the C–S–H phase and consumption of portlandite. Alumina-rich SCMs increase the Al-uptake in C–S–H and the amounts of aluminate containing hydrates. In general the changes in phase assemblages are well captured by thermodynamic modelling, although better knowledge of the C–S–H is needed.At early ages, “filler” effects lead to an increased reaction of the clinker phases. Reaction of SCMs starts later and is enhanced with pH and temperature. Composition, fineness and the amount of glassy phase play also an important role. Due to the diverse range of SCM used, generic relations between composition, particle size, exposure conditions as temperature or relative humidity become increasingly crucial.     

循环水场补充水量异常的分析和处理方法

以中国石油吉林石化公司电石厂441C循环水场补水量异常问题处理过程为例，通过对循环水运行过程中各种损失因素和计量检测系统的排查，找到了441C循环水场补水量异常的原因并进行了相应的处理，为今后该类问题的解决，提供了行之有效的分析和处理方法。