外文翻译--高性能混凝土的耐久性特点：一综述

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1、 PDF外文：http:/  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 &nb

2、sp;     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 review Abstract Durability problems of ordinary concrete can be associated with the severity of the environment and the use of inappropriate high water/binder ratios. High-perfo

3、rmance 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-desiccation. In high-performance con

4、crete (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 from ordinary concrete. Fie

5、ld 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 written in a few pessimistic

6、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 Outline 1. Introduction 2. Volumetric ch

7、anges 3. Curing concrete 4. Durability 4.1. General matters 4.2. Durability in a marine environment 4.2.1. Nature of the aggressive action 4.2.2. Chemical attack on concrete 4.2.3. Abrasion resistance 4.3. Freezethaw resistance 5. Fire resistance of HPC 5.1. The channel tunnel fire 5.2. The Dsseldor

8、f airport fire 5.3. Spalling of concrete under fire conditions 5.4. The BriteEuram HITECO BE-1158 research project 6. Concluding remarks References 1. Introduction  The recent developments in the field of high-performance concrete (HPC) represent a giant step toward making concrete a high-tech

9、material 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

10、that concrete 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 earth

11、s environment. 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:

12、it displays 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

13、 define 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 syste

14、ms are increasingly 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. 1 represents schematically the fundamental microstructural difference

15、 between cement pastes having a 0.65 and 0.25 water/cement ratio. In a 0.25 W/Cratio cement paste, there are more cement grains and consequently less water per unit volume so that cement grains are much closer to each other than in a 0.65 W/C cement paste. This major difference results in a complete

16、ly different type of hydrated cement paste. A 0.65 W/C ratio cement paste is very porous and rich in crystallized outer hydration products formed through a solutionprecipitation process, while a 0.25 W/C ratio cement paste is very compact and essentially composed of inner hydration products resembli

17、ng a gel developed through a diffusion process. Fig. 2 and Fig. 3 illustrate the major difference existing between the microstructure of a high and low W/C ratio cement paste. This essential microstructural difference results in a major difference in the mechanical and durability behavior of both the cement paste and the transition zone between the paste and the aggregates.     Full-size image (13K)