【正文】 urface from produce the too big stress of drawing, have remarkable 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 general 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 temperature. Line bloated coefficient of steel and concrete line bloated coefficient difference very light, take place little internal stress very only between the two while changing in temperature. Because elastic mould amount of steel concrete elastic mould 7~15 of quantity, reach as interior concrete stress tensile strength and when fracturing, the stress of the reinforcing bar 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 bees numerous, the interval is little, the width and depth are smaller after adding the muscle. 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 majority belong to and do and draw back the crack. Though this kind of crack is generally all relatively light, it stills have certain influence on the intensity and durability of the structure. In order to guarantee concrete project quality , prevent fracturing , improve the durability of the concrete, use the admixture to reduce one of the measures that fractures correctly. Whether is it reduce water is it split pharmaceutical to defend , I summarize his main function in practice to use. (1)There is pore Dao of a large number of mao in the concrete , produce capillary tension in the capillary after water is evaporated, make concrete is it contract out of shape to do. Increasing the thin aperture of hair can reduce the capillary surface tension , but will make the intensity of concrete reduce . This surface tension theory has already been confirmed in the world as far back as the sixties. (2)Water dust than influence important factor that concrete shrink, is it reduce water is it split pharmaceutical can make concrete water consumption reduce by 25% to defend to use. (3)Cement consumption important factor, concrete of person who shrink too, is it add and subtract water is it split concrete reducible 15% of the cement consumption on terms that keep the intensity of concrete of pharmaceutical to defend to mix, its volume is supplemented by increasing aggregate consumption. (4)Reduce water is it split pharmaceutical can improve consistency of grout , reduce concrete secrete ink to defend, reduce and sink and draw back deforming. (5)Improve glueing the strength of forming of the grout and aggregate, the concrete improved 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 tensile strength can produce. Reduce water is it split pharmaceutical effective concrete tensile strength of improvement very to defend , 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 improve resisting carbonization of concrete effectively , reduce carbonization to shrink. (8)Is it reduce water is it split slow coagulation time proper concrete under pharmaceutical to defend , on the basis of preventing the fast water of cement from sending out heat effectively to mix, prevent the plasticity shrink that brings because the cement is not congealed for a long time from increasing. (9)Mix admixture concrete and getting easy and kind , surface easy to feel flat , form little membrane, reduce the moisture to evaporate, reduce drily and shrink. A lot of admixture all have the functions of slow coagulation , increasing and apt , improvement plasticity, the experiment that we should carry on in this respect more in the project practice is pared with and studied, than lean against not improving terms more simple,may getting simple and more direct, economy. Early maintenance of 4 concrete Practice has proved , the mon crack of concrete , most is the surface crack of different depth, main reason its whether temperature gradient cause cold temperature of area lower too easy to form crack suddenly. So say the warm keeping of the concrete is especially important to preventing the early crack of surface. From the viewpoint of temperature stress, should reach and require to keep warm followingly: 1)Prevent concrete internal and external temperature poor and concrete surface gradient from , prevent the surface crack. 2)Prevent concrete from to be ultra and cold , should is it is it make the minimum temperature is not lower than the steady temperature of concrete service time construction time in concrete to try to try one39。 (2)Prevent the foundation from rising and falling too big。 (6)The concrete with medium and longterm and exposed construction builds a piece of surface or thin wall structure, take the measure of keeping warm in cold season。 (4)Bury the water pipe underground in the concrete, enter the cold water to lower the temperature openly。 (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。s 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 phenomenon of emanating of course, its tensile strength is not even in the same concrete, a lot of resist the ab