 Wysłany: Pon 8:25, 10 Sty 2011 Temat postu: ghd stijltang Winter Bridge concrete construction |
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| Winter Bridge concrete construction method
Process quality has been seriously affected. If the condensation of concrete before (after pouring 3 ~ 6h) were frozen, then the intensity of at least 50%,ghd stijltang, severe coagulation allow 4 - were damaged. If the concrete after the condensation of 2 ~ 3d were frozen, then the strength to lower than normal 15% to 20%. When the coagulation 4 - strength of the design strength of 50% or more and not less than 5.0MPa (at normal temperature curing 5 ~ 7d), to continue its strength when cold is not much affected, but the intensity increased slowly frozen to be opened, the intensity will still be able to continue to rise to the same strength and not cold. Hardened concrete in the process of condensation, such as cold and repeated twice great impact than a cold. Condensation and freezing of the concrete transformation of the conditions of this contradiction is the temperature, the measures taken by construction in winter is to try to maintain the concrete has a certain temperature, so condensation hardening process can proceed smoothly. 2 Winter Concrete Construction Methods 2.1 Regenerative heat storage method is a method with a certain temperature in the pouring of concrete forming immediately after the insulation material to be covered with insulation to delay the concrete cooling rate, the thermal insulation of concrete hardening at normal temperature, condensation, to achieve the desired strength, the heat from the raw materials of concrete and cement hydration heat of the heat. Heating temperature of the raw materials required to calculate the thermal method, the same time to limit the heating temperature. Raw materials, heating, water heating is most simple and most easily controlled. In water heated to the required temperature, mixing concrete can not achieve the required temperature, the heating should be considered sand, and cement can not be heated. When the first heated mixing water and aggregate mix, then add cement, the cement produced in order to avoid \Sand and gravel heating, steam can be directly leads to the sand and gravel can be. This method is quick heating, but will increase the water content of sand and gravel, and the moisture content is uneven and difficult to control the amount of water when mixing. Another method is indirect heating, that is set in the sand steam coil to heat,UGG Boots Outlet, this method is heated slowly, but the water is relatively stable. But can also fire 66 * Direct baking heat, this method is relatively simple equipment, but the heat loss of large, uneven heating, so that part of the sand temperature is too high. Insulation material covering concrete usually used straw bags, sawdust, slag and so on. Regenerative construction method is relatively simple and low cost. Construction should be given priority in the winter to cover the main regenerative heat conservation method, and only in the heat storage method can not only use other methods to meet the requirements, or used in conjunction with other methods. 2.2 Cattle Cattle law method is to use insulation materials corrugated into greenhouses, around the entire structure is heated greenhouses. Insulation shed a certain temperature,oakley sunglasses, its operation, maintenance, like temperature and normal temperature. This method is suitable for colder weather, structure is not the case. Cattle within the heat source can be steam, pipe, or directly with fireplaces. 2.3 The heating steam heating steam heating not only can be concrete, but also the proper humidity to promote their hydration, so that faster hardening concrete setting, this method widely. Steam heating steam in addition to the conservation using a specialized outdoor ventilation within the structure can also be by reservation through the channels of steam to heat coagulation 4 -, when the intended strength of concrete and then fill the pores in mortar reality. There is also method and vapor steam jacket capillary method, the shape and structure are based on the actual situation. Construction of the heating steam temperature should not exceed 80 ℃, uniform heating of concrete to eliminate water and to have the equipment. 2.4 The heating method heating method is embedded in the concrete structure of the electrode,uggs boots cheap, low-voltage current of the concrete by the heat, this method requires more stringent security measures, power consumption, small components used in the heat conservation. 2.5 Cold Cold Concrete in concrete method is in the coagulation 4 - mixed with a calcium chloride, sodium chloride or mixture to accelerate the coagulation 4 - Setting and Hardening speed. This method can reduce the coagulation 4 - in the freezing point of water, played the role of antifreeze,asics australia, and increase the early strength. When the cold concrete pouring, the temperature not lower than a 15 ℃. The corrosive effect of calcium chloride on steel, so far with regular use of sodium sulfite triethanol ammonium compound early strength agent. 2.6 low early strength concrete method of the method is based on regenerative method of heating sand and gravel and other raw materials, and mixed with small amounts of calcium chloride and sodium chloride, the new concrete to maintain a positive short-term temperature and then allowed some of the negative temperature conditions continue to harden, you can get an early frost intensity. This construction method is regenerative method and the cold concrete of synthetic measures. As concrete mixed with small amount of calcium chloride, in the early short-term positive temperature conditions, the calcium chloride accelerates the hydration of cement, so that the slow development of early strength of concrete. Received :2006 -06-04 More articles related to topics： abercrombie outlet Lime and cement stabilized aggr north face outlet Translation Studies and Translat christian louboutin pas cher Carbonation of concre |
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