土木工程外文翻译混凝土施工裂缝原因及防治.docx

1、土木工程外文翻译混凝土施工裂缝原因及防治Construction cracks in concrete, causes and preventionConstruction cracks of concrete reason for the external and internal. The initial mainly refers to the internal defects of concrete in early concrete, its internal hardening process will exist numerous micro-pores, air-pocket

2、and micro cracks, External refers to the load reason: temperature crack, dry shrinkage effect etc. In these, can produce various forms of concrete cracks. To grasp the construction process of raw materials, in pouring process configuration of progress and thickness, grasp timely maintenance work wel

3、l, which can avoid concrete cracks.A, The cause of the tear1.The initial defects of concreteConcrete is composed of cement, sand aggregate, mixed with water and other materials and formation of heterogeneity brittle materials. In the beginning, because hardened concrete construction and deformation,

4、 a series of problems, such as constraint in the concrete shape sclerosis will exist numerous micro-pores, air-pocket and micro cracks of concrete that usually called initial defects. Micro cracks is usually a cracks in the concrete, bearing, and some other function not harm. But under load, tempera

5、ture of concrete, shrinkage and function, micro cracks will be expanded and connectivity, and finally form the visible cracks of concrete, macroscopic crack, said it was the use of concrete structure, properties and durability of adverse effects.2.The load factorDue to the tensile strength of concre

6、te structure or structures, small as a part of the external effects of stress than concrete tensile strength, will crack. Therefore, the concrete in the load and the load, can produce a crack. To load the crack, can produce by reasonable design and construction to prevent. For the load of crack, due

7、 to reasons, it is hard to handle and prevent. The more common than load factors have temperature, dry shrinkage, settling contraction deformation, plastic shrinkage deformation, etc, in these function, can make concrete inside tensile stress.3.Big volume concrete crack formation reasonsMassive conc

8、rete cracking reasons can be divided into two types: one is the structural cracks, is caused by external load, 2 it is material of crack is not caused by the changes of deformation and temperature stress and is mainly composed of concretes shrinkage. This article mainly discussed type materials. One

9、 specific reasons are as follows:The temperature stress caused by fracture (temperature crack) temperature cracks in the main reason is caused by temperature difference. Temperature can be divided into three types: early concrete pouring, produce large amounts of the hydration heat, due to the concr

10、ete is a poor conductor of heat accumulation in concrete, the hydration heat to send out, often make internal temperatures rise, concrete and reinforced concrete surface temperature for outdoor environment temperature, it is formed, the temperature and temperature inside of condensate in early concr

11、ete tensile stress when more than concrete compressive strength, will cause cracking in concrete, In addition, in the dismantling formwork, surface temperature and reduce the temperature caused by fast, and will cause cracking. When the concrete temperature, maximum heat radiates to the minimum temp

12、erature, temperature, or use them with the highest temperature difference is the internal temperature, These three temperature will produce temperature crack. In these three temperature, is mainly caused by hydration heat and the temperature.Shrinkage crack contraction there are many causes, includi

13、ng drying shrinkage, plastic shrinkage, shrinkage, carbonation contraction, etc. Here mainly introduces drying shrinkage and plastic shrinkage.After drying shrinkage of concrete sclerosis, in dry environment, the water concrete to the loss caused by inside extroversion, concrete the shrinkage deform

14、ation cracks.The plastic shrinkage of cement and concrete in the activity of higher temperature, or in low water-cement condition exacerbate cause craze. When the concrete surface water obviously decreased, lactation evaporation of water cannot get the timely supplements, then concrete is still in a

15、 state of plastic, by a concrete surface tension, uneven distribution will appear the cracks of concrete cracks, and further intensify the moisture inside body, and further expansion crackSecond, the measures to prevent cracksFrom the above analysis, the crack is mainly caused by temperature differe

16、nce and contraction, so in order to prevent the cracks of, will maximize reduce temperature and reduce the shrinkage of concrete, specific measures as follows.1. Optimizing raw materials(1)Cement. The cement should be chosen according to the engineering properties, construction condition, climate an

17、d other technical requirements, comprehensive consideration, to meet the strength and durability of concrete design requirements. When the choice should be labeled with cement concrete design match the label. For full strength of cement, cement, cement save from the label for concrete label 1.5 to 2

18、 times as appropriate.(2) aggregate. (a) coarse aggregate. The coarse aggregate concrete rubble is close-grained, must have the enough strength, hard to expand the coarse aggregate size. To ensure the concrete pouring dao close-grained, coarse aggregate maximum diameter less than the minimum size of

19、 the structural sections 1/4, also not greater than the minimum distance between steel net for thickness 3/4, in 10 centimeters and concrete, allowing adopts maximum diameter 1 1/2 of the aggregate number, but it shall not exceed 25%. (b) fine aggregate. Sand particle gradation of technical properti

20、es of concrete influence, requests the porosity and total surface area small, small need total surface on the surface of the gravel package will reduce quantity of cement slurry, can reduce the dosage of cement hydration heat, reduce to prevent cracks. On the other hand is to control the hydraulic s

21、and, the content of 5% in concrete, the contraction deformation, the hydraulic and larger crack, fine aggregate to use clean in the sand.(3) admixtures. (a) water-reducing agent. Jianshuiji belongs to the surface active substances, is a kind of cement dispersant. Its main function of improving concr

22、ete workability, reduce the consumption of concrete mixture, reduce water-cement ratio increases, and improve the liquidity of concrete strength of concrete or keep in concrete cement strength must decrease, while the water-cement ratio, the dosage of cement to prevent cracking is reduced. (b) retar

23、der. Retarder is delaying the role of concrete exothermic peak time, 2 it is to improve workability, and reduce the loss of collapsbillity. (c) air-entraining agent. In the application of concrete air-entraining agent for improving the concrete workability, can pump, improving the concrete durabilit

24、y is very favorable. In a certain extent increase anti-cracking performance of concrete.(4) mass concrete chooses raw materials should pay attention to the following: The coarse aggregate gradation, appropriate USES continuous fine aggregate ZhongSha should be adopted. Admixtures appropriate USES re

25、tarder, water-reducer, Admixtures appropriate USES fly ash, slag powder etc. In mass concrete strength of concrete and the slump and the requirements of the premise, should improve mixing and aggregate content, in order to reduce the dosage of cement concrete alone. Should try to choose cement hydra

26、tion heat low, setting time is long, the cement, low thermal Portland cement slag silicate cement, cement, slag dam Portland cement, coal ash Portland cement, volcanic gray Portland cement, etc.However, the slag cement hydration heat low water cement ratio of chromatography in other large, casting l

27、ots of water surface layer. This phenomenon is not only affect lactation water, also influence the construction speed and quality of construction. Because the water gathered in separation between the two casting concrete surface layer, change, and water-cement ratio in the water and took out some of

28、 the mortar, thus forming a layer of interlining content, destroyed the cohesive force of concrete and holistic. The size of the water concrete lactation with water water, water, lactation; And with the temperature, water separation of time with temperature completely and shortening, In addition, al

29、so with the composition and fineness of cement. Therefore, in selecting slag cement should be chosen when the varieties, and lactation shall be adding water-reducing agent in concrete, to reduce the consumption. During construction, should be in water or mixing some tomography uniform rolling cement

30、 casting in water, with 3-degrees vibration compaction, continue again after a concrete casting.2.the reasonable construction method(1) The concrete mixing and transportation. (a) white, accurate grasp of concrete proportion, especially the strict control of water consumption, the determination of s

31、and. Records of every block water cement, sand and gravel, specific quantity, the application must be accurate to scale, by mixing. Good control of concrete slump and general shoulds not be too big, in 120 20 mm. To minimize the mouth 3 concrete temperature. (b) concrete mixing in a storehouse after

32、 good transport process, to prevent to produce separation, lactation water, mortar loss should shorten transportation time, concrete loading not too full.(2)Concrete pouring and open mode. Pouring process may be close-grained, vibration to vibration time should be uniform in surface functional plasm

33、a advisable, uniform spacing, vibrating force scope affected overlap 1/2 advisable, after casting, compaction, surface must, in order to prevent the surface crack. Try to avoid in the solar radiation, high time due to the needs of the project if pouring in summer construction, avoid noon pouring temperature period, try to arrange at n