外文翻译--高性能混凝土的耐久性特点:一综述-其他专业.doc
《外文翻译--高性能混凝土的耐久性特点:一综述-其他专业.doc》由会员分享,可在线阅读,更多相关《外文翻译--高性能混凝土的耐久性特点:一综述-其他专业.doc(16页珍藏版)》请在得力文库 - 分享文档赚钱的网站上搜索。
1、本科毕业设计英 文 翻 译院系部 土木工程学院 专业名称 土木工程专业 年级班级 道桥07-4班 学生姓名 周 鹏 指导老师 程 朝 霞 河南理工大学土木工程学院二一一年六月十日The durability characteristics of high performance concrete: a reviewAbstractDurability problems of ordinary concrete can be associated with the severity of the environment and the use of inappropriate high wate
2、r/binder ratios. High-performance concrete that have a water/binder ratio between 0.30 and 0.40 are usually more durable than ordinary concrete not only because they are less porous, but also because their capillary and pore networks are somewhat disconnected due to the development of self-desiccati
3、on. In high-performance concrete (HPC), the penetration of aggressive agents is quite difficult and only superficial. However, self-desiccation can be very harmful if it is not controlled during the early phase of the development of hydration reaction, therefore, HPC must be cured quite differently
4、from ordinary concrete. Field experience in the North Sea and in Canada has shown that HPCs, when they are properly designed and cured, perform satisfactorily in very harsh environments. However, the fire resistance of HPC is not as good as that of ordinary concrete but not as bad as is sometimes wr
5、itten in a few pessimistic reports. Concrete, whatever its type, remains a safe material, from a fire resistance point of view, when compared to other building materials.Author Keywords:Curing; Durability; Fire-resistance; Freezing and thawing; High performance concrete Article Outline1. Introductio
6、n2. Volumetric changes3. Curing concrete4. Durability4.1. General matters4.2. Durability in a marine environment4.2.1. Nature of the aggressive action4.2.2. Chemical attack on concrete4.2.3. Abrasion resistance4.3. Freezethaw resistance5. Fire resistance of HPC5.1. The channel tunnel fire5.2. The Ds
7、seldorf airport fire5.3. Spalling of concrete under fire conditions5.4. The BriteEuram HITECO BE-1158 research project6. Concluding remarksReferences1. IntroductionThe recent developments in the field of high-performance concrete (HPC) represent a giant step toward making concrete a high-tech materi
8、al with enhanced characteristics and durability. These developments have even led to it being a more ecological material in the sense that the componentsadmixtures, aggregates, and waterare used to their full potential to produce a material with a longer life cycle. Be that as it may, we know that c
9、oncrete will never be an eternal material when measured against a geological time frame. Any concrete, if we look far enough into the future, will end its life cycle as limestone, clay, and silica sand, which are the most stable mineral forms of calcium, silica, iron, and aluminum in the earths envi
10、ronment. Therefore, all we can do as engineers or scientists is to extend the life cycle of this artificial rock as much as possible.The concrete that was known as high-strength concrete in the late 1970s is now referred to as HPC because it has been found to be much more than just stronger: it disp
11、lays enhanced performances in such areas as durability and abrasion resistance. Although widely used, the expression “HPC is very often criticized as being too vague, even as having no meaning at all. Since there is no single best definition for the material known as HPC, it is preferable to define
12、it as a low water/binder concrete which receives an adequate water curing.HPC can be made with cement alone or any combination of cement and mineral components, such as, blast furnace slag, fly ash, silica fume, metakaolin, rice husk ash, and fillers, such as limestone powder. Ternary systems are in
13、creasingly used to take advantage of the synergy of some mineral components to improve concrete properties in the fresh and hardened states, and to make high performance concrete more economical and ecological. Fig. 1W/CW/CW/CW/Cratio cement paste is very compact and essentially composed of inner hy
14、dration products resembling a gel developed through a diffusion process.Fig. 2andFig. 3illustrate the major difference existing between the microstructure of a high and lowW/Cratio cement paste. This essential microstructural difference results in a major difference in the mechanical and durability
15、behavior of both the cement paste and the transition zone between the paste and the aggregates.Full-size image(13K)Fig. 1. Schematical representation of the microstructure of two cement pastes havingW/Cratios of 0.65 and 0.25.Full-size image(71K)Fig. 2. Microstructure of high water/cement ratio conc
16、rete: (a) high porosity and heterogeneity of the matrix, (b) orientated crystal of Ca(OH)2on aggregate (AG), (c) CH crystals.Full-size image(52K)Fig. 3. Microstructure of a HPC: low porosity and homogeneity of the matrix: (a) absence of transition zone between the aggregate and cement paste; (b) den
17、se cement paste in an air entrained high performance concrete.In particular, in HPC, the coarse aggregate can be the weakest link in concrete when the strength of the hydrated cement paste is drastically increased by lowering its water/binder ratio. In such cases, concrete failure can start to devel
18、op within the coarse aggregate. As a consequence, there can be exceptions to the water/binder ratio law when dealing with HPC. In some areas, decreasing the water/binder ratio below a certain level is not practical from a mechanical point of view because the strength of the HPC will not significantl
19、y exceed the compressive strength of the aggregate. When the compressive strength is limited by the coarse aggregate, the only way to get higher strength is to use a stronger aggregate. But although the compressive strength is not increased when decreasing theW/Bratio, the compactness of the matrix
20、is increased and the durability of HPC is improved.2. Volumetric changesAs with any other material, the volume of concrete changes as its temperature changes. Like any other material concrete creeps. But it is not the only volumetric variations exerting itself on concrete. Depending on its curing co
21、ndition, concrete presents volumetric variations, it usually shrinks but sometimes it swells. In this paper, swelling of chemical origin, such as sulfate or thaumasite attack or alkali aggregate reaction will not be considered, the only volumetric variation taken into account will be plastic shrinka
22、ge, autogenous or isothermal shrinkage, and drying shrinkage 2. Carbonation shrinkage will not be considered because it is a very slow process that takes place much later.In all cases that will be considered in this paper, the origin of the volumetric variation is the same, the appearance of tensile
23、 stresses in the menisci created in the fresh concrete as it is drying (plastic shrinkage) or in the hardened concrete due to self-desiccation (autogenous shrinkage) and due to dying (drying shrinkage).Autogenous shrinkage is a consequence of the chemical contraction occurring in the cement paste wh
24、en water hydrates cement particles. In fact, the absolute volume of the hydrates formed is smaller than the sum of the absolute volume of the cement particles and the water that have reacted. Hydration creates some 8% voids, as found by Le Chatelier and Powers 3. This very fine porosity drains water
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 外文 翻译 性能 混凝土 耐久性 特点 综述 其他 专业
限制150内