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1、Discuss the construction temperature and crack of the concrete lightlyBy G. K. Kululanga, W. Kuotcha, R. McCaffer, Member, ASCE, and F. Edum-Fotwe ,The American Society of Civil EngineersThe summary , In order to prevent the owners of the concrete work of claims, we must do a good job in the constru
2、ction process in the temperature and crack control,through observation live for many years, through consulting the monograph about stress within the concrete, explain to concrete temperature reason , on-the-spot concrete control and measure , prevention of crack of temperature that crack produce. Ke
3、yword Concrete Temperature stress Crack Control 1. The concrete occupies the important position in modern engineering construction. But today, the crack of the concrete is comparatively general, the cracks are nearly omnipresent in the science of bridge building. Though we take various kinds of meas
4、ures 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 concrete temperature stress pays attention to. In the large volume concrete, temperature stress and temperature control are significant. This is mainly b
5、ecause of the reason of two respects. First of all, concrete often appear the temperature crack in not constructing, influence the globality and durability of the structure. Secondly, in the course of operating, the temperature change has remarkable influence that cant be ignored on the stress state
6、 of the structure. We meet to construct temperature crack in mainly, so only to origin cause of formation and treatment measure, concrete of crack make a discussion in constructing this text. Reason of a crack Have many kinds of reasons to produce the crack in the concrete, it is mainly the changes
7、of temperature and humidity, fragility and disparity of the concrete, and the structure is unreasonable, the raw materials is not 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 hyd
8、ration when the concrete is hardenned, inside temperature is rising constantly, cause the stress of drawing on the surface. In the 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 o
9、f temperature can surface cause heavy stress of drawing very in concrete too. When these draw the stress and go beyond resisting 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 m
10、ight change heavy the violent change takes placing. Such as maintaining thoroughly, when getting wetter when not doing,contract 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,
11、 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 limit 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
12、phenomenon of emanating of course, its tensile strength is not even in the same concrete, a lot of resist the ability of drawing 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 keepin
13、g just. Or reinforcing bar mix if edge position gone to to congeal present the stress of drawing in the structure in plain concrete, 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 conc
14、rete is cooled from maximum temperature to the steady temperature of operating period in constructing, often cause sizable to draw 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 carr
15、y on reasonable structural design and construct extremely important. Analysis of 2 temperature stresses Can be divided into following three stages according to the forming process of the temperature stress: (1)It is early: Build concrete is it is it over basically to send out heat to cement to begin
16、 , generally one one day by oneself. Two characteristics at this stage, first, 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 period: Up till the concrete is cooled until stability temperature from cement send out heat function basically when expiring, in this per
