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1、外文翻译Discuss the construction temperature and crack of the concrete lightlyThe summary ：In order to prevent the owners of the concrete work of claims, we must doa good job in the construction process in the temperature and crack control,thr-ough observation live for many years, through consulting the
2、 mono-graph 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.Keyword ： Concrete Temperature stress Crack Control1. The concrete occupies the important position in modern enginee
3、ring constr-uction. But today, the crack of the concrete is comparatively general, the cracks are nearly omnipre-sent in the science of bridge building. Though we take various kinds of measures in cons-tructing, careful, but the crack still occurs now and then. Tracing it to its cause, it is one of
4、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 because of the rea-son of two respects. First of all, concrete often appear the temperature crack in not constru
5、cting, influence the globality and durability of the stru-cture. Secondly, in the course of operating, the temperature change has remarkable infl-uence that cant be ignored on the stress state of the structure. We meet to construct tem-perature crack in mainly, so only to origin cause of formation a
6、nd treatment mea-sure, concrete of crack make a discussion in constructing this text.1.1 Reason of a crackHave many kinds of reasons to produce the crack in the concrete, it is mainly thechanges of temperature and humidity, fragility and disparity of the concrete, and the st-ructure is unreasonable,
7、 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 ce-ment emits a large amount of heat of hydration when the con-crete is hardened, inside te-mperature is rising constantly, cause the stress of dr
8、-awing on the surface. In the course of lowering the temperature , is it congeal fo-undation pay restrain to mix always later st-age,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 st
9、ress andgo beyond resis-ting 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, sur-face humidity might change heavy the violent change takes placing. Such as maintaining thoroughly, when getting we
10、tter when not doing,contract surface th-ere arent deforma-tion 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 li-mit when draw out of shape to have *104 only , is it car
11、ry 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 phenol-menon of emanating of course, its tensile strength is not even in the same concrete, a lo
12、t of resist the ab-ility of drawing very low, it is apt to present the weak position of the cr-ack. Among armored concrete , draw stress to undertake by reinforcing bar mainly, Con-crete bear stress of keeping just. Or reinforcing bar mix if edge position gone to to con-geal present the stress of dr
13、awing in the structure in plain concrete, must rely on the con-crete 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 con-crete is cooled from maximum te-mperature to the steady temperature of operating period in
14、 constructing, often cause siza-ble to draw the stress within the concr-ete. The temperature stress can exceed other outs-ides and load the stresses ca-used so-metimes, know change law , temperature of stress f-or carry on reasonable struc-tural design and construct extremely important.1.2 Analysis
15、of temperature stressesCan be divided into following three stages according to the forming process of thetemperature stress:(1) It is early: 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 stage, first, the
16、 cement emits a large amount of heat of hydration, second , mix and congeal the changing sharply of el-astic model quantity. Because of the change of elastic model quantity , form the remain-ing stress in the concrete in this period.(2) Middle period: Up till the concrete is cooled until stability t
17、emperature from cement send out heat function basically when expiring, in this period, the temp-erature stress is mainly because the cooling of the concrete and external temp-erature change cause, these stresses and remnants stresses that is formed in early days are superposed , mix and cong-eal the
18、 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 whether external temperature change cause mainly, these stresses and first two kinds of remnants stresses are changed and added
19、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 t-he border, if inside temperature is non-linear distribution, temperature stress ap-pearing because str-ucture restrains from ea
20、ch other. For example, the body of mound of the bridge,the phy-sical dimension is relatively large, surface tempera-ture is low when the concrete is cool-ed, inside temperature is high, present the stress of drawing on the surface, present the st-ress of pressing in the middle.(2) Restrain the stres
21、s: All of the structure ones or it restrain external one some borde-r,cant out of shape and stress not cause not free. Such as case roof beam roof conc-rete and guardrail concrete.This two kinds of temperature stresses draw back stresses caused to act on with the doing of concrete together frequentl
22、y. It is a more complicated job to want to analyse the distribution , size of the tempe-rature stress accurately according to known temperature. In case of great maj-ority , need to rely on the model test or the num-ber value to calculate. To it make temperature stress have sizable limp to creep con
23、crete, at the stress accounting temperature, must consider the influence that creep , calculate co-ncretly that no longer states thinly here.1.3 Control and preventing the measure of the crack of temperatureFor prevent crack , lighten temperature stress can from control temperature and is it set a-b
24、out 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 ad-opt, is it guide angry pharmaceutical or plastification pharmacy-eutical ,etc. measure in o-rder to reduce cemen
25、t consumption of concrete to add;(2) Add water or the water to cool the broken stone in order to reduce tempera-ture of b-uilding of the concrete while mixing and shutting the concrete;(3) Reduce the thickness of building while building the concrete on hot day, utilize and build the aspect to dispel
26、 the heat;(4) Bury the water pipe underground in the concrete, enter the cold water to lower the te-mperature openly;(5) Stipulate rational form removal time, the temperature keeps warm the surface while l-owering suddenly, in case that the rapid temperature gradient takes place in the concrete surf
27、ace;(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 me-asure of improving condition of restraining is:(1) Divide and sew and divide one rationally ;(2) Prevent the foundation fro
28、m rising and falling too big;(3) Rational arrangement construction process, prevent the too big discrepancy in elev-ation and side from exposing for a long time; In addition, improve the per-formance of the concrete and improve and resist the ability of splitting, strengthen maintenance , pre-vent t
29、he 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 avoi-ding producing and running through the crack , the globality resumed its structure after appearing is very difficult, so should
30、 rely mainly on preventing the emergence of the run-ning through crack while constru-cting. In construction of concrete , for raise turnover ra-te of template , demand concrete form removal as soon as possible that build newly often. Should cons-ider form removal time properly when concrete temperat
31、ure 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 phenol-menon that temperature is assaulted appears. Build initial stage in concrete, because heat of hydration
32、 is sent out, the surface causes sizable to dr-aw the stress, surface tempe-rature is also higher than temperature at this mome-nt, remove the template at this mom-ent , surface temperature is lowered sudde-nly, must cause temperature gradient , thus ad-d and draw the stress on the sur-face , change
33、 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 insul-ator with on the surface in time after removing the template , for instan
34、ce foam sponge- ,etc, for prevent concrete surface from produce the too big stress of drawing, have rem-arkable results.Add muscle influence to large volume temperature stress of concrete very light ,because large volume concrete include muscle to be rate very much low. Just have influence on the ge
35、neral armored concrete. On terms that temperature is not very high and the stress is less than limit of surrendering, every performance of the steel is steady, and have nothing to do with stress state , time and temper-ature. Line bloated coefficient of steel and conc-rete line bloated coefficient d
36、iffer-rence very light, take place little internal stress very o-nly between the two while changing in temperature. Because elastic mould amount of steel concrete elastic mould 715 of quantity, reach as interior concrete stress tensile st-rength and wh-en fracturing, the stress of the reinforcing ba
37、r will not exceed 10000kg-/cm2. So is it is it prevent tiny appearance difficulty very much of crack from to make use of reinforcing bar to want among concrete. But the crack in the structure generally becomes numerous, the interval is little, the width and depth are smaller after adding the muscle.
38、 And if diameter of reinforcing bar detailed and when interval dense, to improve concrete resist result of person who split better. Concrete and surface , armored concrete of structure can take place detailed and shallow crack often, among them the great majo-rity belong to and do and draw back the
39、crack. Though this kind of crack is generally all relatively light, it stills have certain infl-uence on the intensity and durability of the struc-ture.In order to guarantee concrete project quality , prevent fracturing , improve the durability of the concrete, use the admixture to reduce one of the
40、 measures that fractures correctly. Whether is it reduce water is it split pharmaceutical to defend , I summarize his main fun-ction in practice to use.(1) There is pore Dao of a large number of mao in the concrete , produce cap-illary tens-ion in the capillary after water is evaporated, make concre
41、te is it con-tract out of shape to do. Increasing the thin aperture of hair can reduce the cap-illary surface tension , but will make the intensity of concrete reduce . This sur-face tension theory has already been con-firmed in the world as far back as the sixties.(2) Water dust than influence impo
42、rtant factor that concrete shrink, is it reduce water is it split pharmaceutical can make concrete water consumption reduce by 25% to defend to u-se.(3) Cement consumption important factor, concrete of person who shrink too, is it add an-d subtract water is it split concrete reducible 15% of the cem
43、ent consump-tion on terms t-hat keep the intensity of concrete of pharmaceutical to defend to mix, its volume is suppl-emented by increasing aggregate consumption.(4) Reduce water is it split pharmaceutical can improve consistency of grout , re-duce co-ncrete secrete ink to defend, reduce and sink a
44、nd draw back deforming.(5) Improve glueing the strength of forming of the grout and aggregate, the con-crete im-proved resists the performance of splitting.(6) Concrete is it produce stress of drawing to restrain from while shrinking, crack when drawing the stress and is greater than concrete tensil
45、e strength can produ-ce. Reduce wat-er is it split pharmaceutical effective concrete tensile strength of improvement very to de-fend , improve resisting the performance of splitting of concrete by a wide margin.(7) It can make the concrete density good to add the admixture to mix , can impr-ove resi
46、-sting carbonization of concrete effectively , reduce carbonization to shrink.(8) Is it reduce water is it split slow coagulation time proper concrete under Pharmaceut-ical to defend , on the basis of preventing the fast water of cement from sending out heat effectively to mix, prevent the plasticit
47、y shrink that brings because the cement is not con-gealed for a long time from increasing.(9) Mix admixture concrete and getting easy and kind , surface easy to feel fla t , form little membrane, reduce the moisture to evaporate, reduce drily and shrink. A lot of adm-ixture all have the functions of
48、 slow coagulation , increasing and apt , improvement plas-ticity, the experiment that we should carry on in this respect more in the project practice is compared with and studied, than lean against not improving terms more simple,may g-etting simple and more direct, economy.1.4 Early maintenance of
49、concretePractice has proved , the common crack of concrete , most is the surface crack of differ-ent depth, main reason its whether temperature gradient cause cold tem-perature of area lower too easy to form crack suddenly. So say the warm keeping of the concrete is espe-cially important to preventing the early crack of surface. From the viewpoint of temper-ature stress, should reach and require to keep warm followingly:1) Prevent concrete internal and external temperature poor and concrete surfa