【正文】 rinkle proper before building concrete in the Ji rock and old concrete top build a 5 mm or so sand mat a layer or usage asphalt etc. material Tu2 is to strengthen concrete to protect, the concrete after sprinkle build use moist grass Lian in time, hemp slice39。t be too early, and want to notice to dismantle a mold order of is at jelly soil top take to establish template to notice to adopt certain of prevention measure. crack and prevention Temperature crack much the occurrence is in big surface or difference in temperature variety of the physical volume concrete pare the earth area of the concrete after sprinkling to build, in the hardening the process, cement water turn a creation a great deal of of water turn hot, .(be the cement dosage is in the 350550 kg/m 3, each sign square the rice concrete will release a calories of 1750027500 kJ and make concrete internal thus the temperature rise to reach to 70 ℃ or so even higher)Because the physical volume of concrete be more big, a great deal of of water turn hot accumulate at the concrete inner part but not easy send forth, cause inner part the temperature hoick, but the concrete surface spread hot more quick, so formation inside outside of bigger difference in temperature, the bigger difference in temperature result in inner part and exterior hot the degree of the bulge cold Suo dissimilarity, make concrete surface creation certain of pull should pull should dint exceed the anti of concrete pull strength extreme limit, concrete surface meeting creation crack, this kind of crack much occurrence after the concrete under construction the concrete of under construction be difference in temperature variety more big, perhaps is a concrete to be subjected to assault of cold wave etc., will cause concrete surface the temperature sharply descend, but creation constringency, surface constringency of the concrete be subjected to inner part concrete of control, creation very big of pull should dint but creation crack, this kind of crack usually just in more shallow scope of the concrete surface creation. The alignment of the temperature crack usually none settle regulation, big area structure the crack often maneuver interleave。s45 176。t resist its constringency, therefore creation influence concrete Su constringency open the main factor of crack to have water ash ratio, concrete of condense time, environment temperature, wind velocity, relative humidity...etc.. Main prevention measure:One is choose to use stem the Suo value smaller higher Huo sour salt of the earlier period strength or mon the Huo sour brine is strict the control water ash ratio, the Chan add to efficiently reduce water to increment the collapse of concrete fall a degree and with easy, decrease cement and water of is to sprinkle before building concrete, water basic level and template even to soak is in time to overlay the perhaps damp grass mat of the plastics thin film, hemp slice etc., keep concrete eventually before the Ning surface is moist, perhaps spray to protect etc. to carry on protect in the concrete is in the heat and strong wind the weather to want to establish to hide sun and block breeze facilities, protect in time. to sink crack and prevention The creation which sink to sink crack is because of the structure foundation soil quality not and evenly, loose soft or return to fill soil dishonest or soak in water but result in the asymmetry sink to decline with the result that。t big in match ratio design give settle of use water is the earlier period which strengthen concrete to protect, and appropriate extension protect of concrete construction want to be appropriate extension concrete heat preservation to overlay time, and Tu2 Shua protect to is a constitution the acmodation is in the concrete structure of the constringency sew. Su constringency crack and prevention Su constringency is the concrete is before condense, surface because of lose water quicker but creation of Su constringency crack is gene