碱集料反应与冻融循环协同作用对混凝土破坏的影响

研究了碱集料反应与冻融循环协同作用下的混凝土的破坏行为，结果表明，当混凝土先进行碱集料反应试验而随后再冻融时，碱集料反应对冻融循环有促进作用，随着碱集料反应程度的提高，混凝土开裂愈严重，随后表现的混凝土抗冻性愈差；然而当混凝土先冻融，而后再进行碱集料反应时，冻融循环对碱集料反应的促进作用则不大，随着冻融次数的增加，混凝土破坏程度增大，在继续进行的碱集料反应结束时，混凝土最终膨胀值增大，相对动弹模量损失增大，但是混凝土劣化速度则相差不大。     

机立窑试制低碱普通硅酸盐水泥

一．引言碱集料反应是造成混凝土破坏的重要因素。碱集料反应是指混凝土中水泥和外加剂中的碱与集料中的某些成份现水发生反应,产生新生物引起体积膨胀造成混凝土剥落、裂缝、甚至崩溃,从而影响混凝土结构的使用和寿命。碱集料反应通常进行的很慢,所引起的破坏往往经过若干年甚至几十年以后才会明显出现。发生碱集料反应的混凝土寿命只有正常混凝土寿命的四分之一,甚至更短,它引起的破坏要花费大量的人力、物力、财力来修补甚至重建,在工程界被称为是混凝土的“癌症”。基于碱集料反应对混凝土建筑物的危害,降低水泥中的碱含量,使用…     

某工程混凝土含碱量的控制

混凝土原材料中的碱含量过高时,可能发生碱集料反应,引起混凝土结构的破坏。工程中应从混凝土的原材料选择开始仔细考虑碱集料反应,严格预防碱集料反应的发生。混凝土内部发生碱集料反应破坏与否,除了与水泥碱含量有关外,更重要的是与混凝土中的总碱含量有关。以混凝土原材料中的总碱含量作为控制标准是切实可行和更为可靠的。     

碱集料反应(AAR)研究评述

本文论述了碱集料反应的分类及其破坏机理、集料碱活性检测方法、预防碱集料反应的几种方法、以及碱集料反应破坏事例的识别方法,探讨了碱集料反应研究中存在的一些问题,并以此提出了解决这些问题的途径。     

混凝土碱集料反应的鉴定方法及预防措施探讨

1，碱集料反应（AAR）的危害性互．五国外简况众所周句1，1940年美国T．E．Stant。n首次发现混凝土中的碱集料反应（Alkali－aggregatereaction）。以后又陆续在其它各国发现碱集料反应引起的混凝土裂缝和破坏，因此AAR问题受到世界各国的普遍重视。从1974年以来，已召开了九次国际学术会议。对AAR的实验研究工作也随之日益深入和更加广泛。早在40年代，美国发现加利福尼亚等地的公路、桥梁和大坝混凝土建筑物出现了裂缝。通过对派克坝裂缝的分析，认为是采用了安山岩染料和部分水泥含碱量较高（1.13％，1.25％，1．42％）发生了碱染…     

防水砂浆

在法国采用一种防水砂浆来抑制混凝土结构工程碱集料反应的危害,具有实际效果。将该砂浆用于遭受碱集料反应破坏后的混凝土桥梁上,经4年的连续监测,其防水砂浆的涂层基本完好无损,未发现有碱集料反应的膨胀现象,目前这种监测工作还在继续进行中。 法国的巴大区A-4公路桥于1976年建成交付使用,10年后桥面出现呈网络状裂缝的碱集料反应,其中有2个部件损坏严重,重新进行了更     

浅谈如何预防桥梁工程混凝土的碱集料反应

阐述了水泥混凝土桥梁碱集料反应的形成过程及对桥梁工程的危害,提出了预防桥梁工程碱集料反应的措施.     

碱集料反应最新研究进展

本文综述了目前国内外在碱集料反应方面的最新研究进展,并着重就碱集料反应的破坏机理、检测方法存在的问题和避免检测误差的方法、抑制碱集料反应发生的方法及对碱集料反应能否发生的重要判据--有效碱的含量的测定方法进行了综合阐述.     

碱集料反应对混凝土工程的损坏及预防

介绍了碱集料反应的机理和分类，以及特征与判别，论述了预防混凝土碱集料反应损坏的措施，分析了国内外碱集料反应对混凝土工程损坏及其预防的现状，并对我国预防碱集料反应提出了几点思考和建议。     

碱集料反应对混凝土工程的损坏及其预防

本文介绍了碱集料反应的机理和分类，以及特征与判别。论述了预防混凝土工程碱集料反应损坏的措施，分析了国内外碱集料反应对混凝土工程损坏及其预防的现状，并对我国预防碱集料反应提出了几点思考和建议。     

China's Climate Change Response in the Context of Global Change: from Domain Response to Mitigation and Adaptation then to Scientific and Technological Progress

Climate change has become one of the key issues affecting global society and economic development,and it is related to the sustainable development of mankind and the earth’s ecological system.Firstly,this research begins with the important international conferences and agreements on Global Climate Governance,and analyzes the recent progress of the Paris Agreement,the Marrakech climate conference and the major progress of China & US climate cooperation and China’s contribution.Secondly,from the perspective of China’s adaptation and response to climate change,the main progress of climate change in China is reviewed from a multi-level perspective.The main scientific and technological progress and achievements in China’s response to climate change have been tracked.Finally,from the environmental risk areas,the future risks of climate change are predicted from six aspects,to contribute to the scientific and technological support program for climate change governance.     

A Letter to My Grandparents

<正>Dear grandparents,How’s it going?I hope you both are healthy.I haven’t seen you for two years,and I miss you very much.Let me tell you something different about England and China.In England,I used to chat with you.In China,however,my parents are too busy to chat with me,so I feel lonely     

从DC到CD——DC国际的设计价值观思考

文章重新审视了DC国际设计价值观的发展,体现出设计价值观形成到输出的转变过程。＂从DC到CD＂,从字面上可以看作为文字游戏,但是潜在地暗示了设计重心的转移——从设计在中国到中国式设计。这一设计核心价值观的确立对于DC国际来说关乎集体愿景、发展战略和设计导向。     

数字技术对南京民国建筑修复的研究与实践

本文从分析南京现存民国建筑的状况和存在的问题入手,结合工程实例,研究了运用数字技术对南京民国建筑进行数字化系统构建的手段,以及对民国建筑进行修复的步骤,并对民国建筑的保护提出了对策。     

Spatiotemporal Evolution of Waterlogging Events in Eastern China from 1961 to 2016

In this study, based on the data on the frequency of waterlogging events and the number of waterlogging days of 1,638 stations from 1961 to 2016, a variety of mathematical statistics methods were used to analyze the spatiotemporal evolution of waterlogging events in eastern China. The results showed that:(1) In terms of time, the annual frequency of waterlogging events and the number of waterlogging days in eastern China in 1961–2016 showed an increasing trend despite of fluctuations. In the interdecadal changes, the highest frequency of waterlogging events and the greatest number of waterlogging days occurred in the 1990 s, and from the 1960 s to the 1980 s, the frequency of waterlogging events and the number of waterlogging days in eastern China showed a decreasing trend. There were 6-year and 30-year periodic variations in the frequency of waterlogging events and the number of waterlogging days in eastern China, and mutations occurred in 1991.(2) In terms of space, from 1961 to 2016, the areas with high frequency of waterlogging events in various years in eastern China were mainly South China, western and southern Yunnan, northern Jiangsu, southern Zhejiang, northern Fujian, junction areas between Hunan and Chongqing, northern Sichuan, and eastern Liaoning.(3) In the spatial distribution of change trends and fluctuation characteristics, the frequency of waterlogging events and the number of waterlogging days in eastern China increased significantly in the southeastern coastal areas from 1961 to 2016, and the fluctuations of the frequency of waterlogging events and the number of waterlogging days in eastern China from 1961 to 2016 presented a spatial variation pattern of low in the southwest and high in the northwest.     

浅谈如何加强我国工程造价管理

叙述了目前我国工程造价管理已经取得的改革成果,同时结合当今我国工程造价管理的现状,提出了我国工程造价管理所存在的问题以及我国工程造价管理的发展对策和建议,从而提高我国工程造价管理水平。     

开发地热供热产业

城镇集中供暖和生活热水需求的快速增长,为利用我国丰富的低温地热资源,投资创共热产业提供了良好的机会。依据地热利用工程的实践经验,分析了在我国开发低温地热影响投资决策的因素;介绍了工艺流程、产业化指标、资金和风险,评估了地热供的经济效益。认为不论是否在地热异常区、北方或南方、都有许多机会创办地热产业;为获取经济和社会效益,起决定作用的是于热供热市场的开拓。     

中国绿道规划建设实践——从提级统筹到制度并轨

绿道在中国经过多年实践发展,在理论内涵、规划选线、综合效益等各方面都已有许多成果支撑.基于可公开获取的一系列文献资料,立足于绿道在中国各省市近20年的具体实践过程,梳理绿道在规划体系中的角色转变、在指标设置中的逐步细化和在管控上的落实方式,总结绿道实践在中国从提级统筹、常态认同到制度并轨3个阶段的发展变化,在展望绿道后...     

走向绿色景观

本文从我国当前面临的生态环境危机入手,指出树立绿色景观设计理念的重要意义,进而阐述绿色景观的内涵及走向绿色景观的途径。     

Biogenic emissions of isoprenoids and NO in China and comparison to anthropogenic emissions

In this study, a regional dynamical model (WRF) is used to drive biogenic emission models to calculate high resolution (10x10 km) biogenic emissions of isoprene (C(5)H(8)), monoterpenes (C(10)H(16)), and nitric oxide (NO) in China. This high resolution biogenic inventory will be available for the community to study the effect of biogenic emissions on photochemical oxidants in China. The biogenic emissions are compared to anthropogenic emissions to gain insight on the potential impact of the biogenic emissions on tropospheric chemistry, especially ozone production in this region. The results show that the biogenic emissions in China exhibit strongly diurnal, seasonal, and spatial variations. The isoprenoid (including both isoprene and monoterpenes) emissions are closely correlated to tree density and strongly vary with season and local time. During winter (January), the biogenic isoprenoid emissions are the lowest, resulting from lower temperature and solar radiation, and highest in summer (July) due to higher temperature and solar radiation. The biogenic NO emissions are also higher during summer and lower during winter, but the magnitude of the seasonal variation is smaller than the emissions of isoprene and monoterpenes. The biogenic emissions of NO are widely spread out in the northern, eastern, and southern China regions, where high-density agricultural soil lands are located. Both biogenic NO and isoprenoid emissions are very small in western China. The calculated total biogenic emission budget is smaller than the total anthropogenic VOC emission budget in China. The biogenic isoprenoid and anthropogenic VOC emissions are 10.9 and 15.1 Tg year(-1), respectively. The total biogenic and anthropogenic emissions of NO are 5.9 and 11.5 Tg(NO) year(-1), respectively. The study shows that in central eastern China, the estimated biogenic emissions of isoprenoids are very small, and the anthropogenic emissions of VOCs are dominant in this region. However, in northeastern and southern China, there are relatively large biogenic emissions of isoprenoids, leading to an important impact on the ozone production in these regions. Furthermore, the emissions of isoprenoids are highest during summer and noontime, which correlates to the peak of ozone production period. For example, the ratio between summer and winter for the emissions of isoprenoids is about 15 in China. As a result, the biogenic emissions of isoprenoids are significantly larger than the anthropogenic emissions of VOCs in China during daytime in summer. Biogenic NO emissions are mostly produced by agricultural soils which co-exist with large populations and human activity. As a result, the biogenic emissions of NO are mostly overlapped with the anthropogenic emissions of NO, leading to the enhancement in NO concentrations in the high anthropogenic NO emission regions. Finally, the future emissions of isoprene and monoterpenes over China are estimated. The results show that the future biogenic emissions may increase significantly due to land cover changes in central eastern China, which could have a very important impact on ozone formation in this region. However, these estimates are highly uncertain and are presented as a potential scenario to show the importance of possible changes of biogenic emissions in China.