1、A1 15页 原始调整 标记版 土木专业外文翻译 英文原文Volume 16, Issue 2, 2009, Pages 7381 P.S.Mangat, J.M.Khatib, B.T.Molloy Department of Engineering, University of Aberdeen, Kings College, Aberdeen, UKconcrete construction crack controlAbstract： This paper presents some results from a wide-ranging investigation of stress
2、 within the concrete, explain to concrete crack reason , concrete crack control and measure , prevention of crack of temperature that crack produce. Keyword: construction crack ; concrete;1. IntroductionThe concrete occupies the important position in modern engineering construction. But Today, The c
3、rack of the concrete is comparatively general, the cracks are nearly omnipresent in the science of bridge building. Though we take various kinds of measures in constructing, careful, but the crack still occurs now and then. Tracing it to its cause, it is one of them incompletely that our change to c
4、oncrete temperature stress pays attention to. In the large volume concrete, temperature stress and temperature control are significant. This is mainly because of the reason of two respects. First of all, concrete often appear the temperature crack in not constructing, influence the globality and dur
5、ability of the structure. Secondly, in the course of operating, the temperature change has remarkable influence that cant be ignored on the stress state of the structure. We meet to construct temperature crack in mainly, so only to origin cause of formation and treatment measure, concrete of crack m
6、ake a discussion in constructing this text. 2.How a crack happen Reason of a crackHave many kinds of reasons to produce the crack in the concrete, It is mainly the changes of temperature and humidity, fragility and disparity of the concrete, and the structure is unreasonable, the raw materials is no
7、t up to standard (if the alkali aggregate react), the template is out of shape, the foundation does not subside etc. evenly . The cement emits a large amount of heat of hydration when the concrete is hardenned, inside temperature is rising constantly, cause the stress of drawing on the surface. In t
8、he course of lowering the temperature , is it congeal foundation pay restrain to mix always later stage, will present the stress of drawing within the concrete . Reducing of temperature can surface cause heavy stress of drawing very in concrete too. When these draw the stress and go beyond resisting
9、 the ability of splitting of concrete , namely will present the crack . A lot of inside humidity of concrete change very light or change relatively slow, surface humidity might change heavy the violent change takes placing. Such as maintaining thoroughly, when getting wetter when not doing,contract
10、surface there arent deformation doing, often cause the crack too. The concrete is a kind of fragility material , tensile strength is about 1/10 of the compression strength, is it carry on ones shoulder or back limit when draw out of shape to have *104 only , is it carry on ones shoulder or back limi
11、t location when stretch out of shape to there is *104 to add for a long time to add a short time. Because raw materials even, water dust than unstable, transport and build phenomenon of emanating of course, its tensile strength is not even in the same concrete, a lot of resist the ability of drawing
12、 very low, it is apt to present the weak position of the crack. Among armored concrete , draw stress to undertake by reinforcing bar mainly , concrete bear stress of keeping just. Or reinforcing bar mix if edge position gone to to congeal present the stress of drawing in the structure in plain concr
13、ete, must rely on the concrete oneself to bear . Require to avoid the stress of drawing or only very small stress of drawing appears of the the general design. But the concrete is cooled from maximum temperature to the steady temperature of operating period in constructing, often cause sizable to dr
14、aw the stress within the concrete. The temperature stress can exceed other outsides and load the stresses caused sometimes, know change law , temperature of stress for carry on reasonable structural design and construct extremely important. 1.2 The reason to the temperature stress: Analysis of 2 tem
15、perature stressesCan be divided into following three stages according to the forming process of the temperature stress: (1)It is early stage: Build concrete is it is it over basically to send out heat to cement to begin , generally one one day by oneself. Two characteristics at this early stage, fir
16、st, the cement emits a large amount of heat of hydration, second , mix and congeal the changing sharply of elastic model quantity. Because of the change of elastic model quantity , form the remaining stress in the concrete in this period. (2)middle stage period: Up till the concrete is cooled until
17、stability temperature from cement send out heat function basically when expiring, In the middle stage , the temperature stress is mainly because the cooling of the concrete and external temperature change cause, these stresses and remnants stresses that is formed in early days are superposed , mix a
18、nd congeal the elastic mould amount that goes to and does not change much during this period. (3)Later period: Operation period after the complete cooling of concrete.Temperature stress at the later stage whether external temperature change cause mainly, these stresses and first two kinds of remnant
19、s stresseses are changed and added . Can be divided into two kinds according to the reason why the temperature stress causes: (1)Spontaneous stress: There are not any restraint or totally static structure at the border, if inside temperature is non-linear distribution, temperature stress appearing b
20、ecause structure restrains from each other. For example, the body of mound of the bridge, the physical dimension is relatively large, surface temperature is low when the concrete is cooled, inside temperature is high, present the stress of drawing on the surface, present the stress of pressing in th
21、e middle. (2)Restrain the stress: All of the structure ones or it restrain external one some border,cant out of shape and stress not cause not free. Such as case roof beam roof concrete and guardrail concrete. This two kinds of temperature stresses draw back stresses caused to act on with the doing
22、of concrete together frequently. It is a more complicated job to want to analyse the distribution , size of the temperature stress accurately according to known temperature. In case of great majority , need to rely on the model test or the number value to calculate. To is it make temperature stress
23、have sizable limp to creep concrete, at the stress accounting temperature, must consider the influence that creep , calculate concretly that no longer states thinly here. 1.3 The measure to prevent crack Control and preventingFor prevent crack , lighten temperature stress can from control temperatur
24、e and is it is it set about to restrain terms from two to improve. The measure of controlling temperature is as follows: (1)Is it improve aggregate grade mix , is it do rigid concrete to spend , mix mixture to adopt, is it guide angry pharmaceutical or plastification pharmaceutical ,etc. measure in
25、order to reduce cement consumption of concrete to add; (2)Add water or the water to cool the broken stone in order to reduce the temperature of building of the concrete while mixing and shutting the concrete; (3)Reduce the thickness of building while building the concrete on hot day, utilize and bui
26、ld the aspect to dispel the heat; (4)Bury the water pipe underground in the concrete, enter the cold water to lower the temperature openly; (5)Stipulate rational form removal time, the temperature keeps warm the surface while lowering suddenly, in case that the rapid temperature gradient takes place
27、 in the concrete surface; (6)The concrete with medium and long-term and exposed construction builds a piece of surface or thin wall structure, take the measure of keeping warm in cold season; The measure of improving condition of restraining is: (1)Divide and sew and divide one rationally ; (2)Preve
28、nt the foundation from rising and falling too big; (3)Rational arrangement construction process, prevent the too big discrepancy in elevation and side from exposing for a long time; In addition, improve the performance of the concrete and Improve and resist the ability of splitting, strengthen maint
29、enance , prevent the surface from being done and contracted , especially guarantee the quality of the concrete is very important to preventing the crack, should pay special attention to avoiding producing and running through the crack , the globality resumed its structure after appearing is very dif
30、ficult, so should rely mainly on preventing the emergence of the running through crack while constructing. In construction of concrete , for raise turnover rate of template , demand concrete form removal as soon as possible that build newly often. Should consider form removal time properly when conc
31、rete temperature is higher than the temperature, so as not to cause the superficial early crack of concrete. Building the early form removal newly, cause very large stress of drawing on the surface, the phenomenon that temperature is assaulted appears. Build initial stage in concrete, because heat o
32、f hydration is sent out, the surface causes sizable to draw the stress, surface temperature is also higher than temperature at this moment, remove the template at this moment , surface temperature is lowered suddenly, must cause temperature gradient , thus add and draw the stress on the surface , ch
33、ange and add with the heat of hydration stress, in addition, the concrete dries and contracts , the superficial stress of drawing reaches very great number value, have danger of causing the crack, but cover a light-duty heat insulator with on the surface in time after removing the template , for ins
