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Prestressed concrete beam \

. Steam curing prestressed concrete girder often occur when the steam-cured \Green Bank is the Qingdao-Yinchuan Highway viaduct across State Road 107, a key project. single-span 35 meters,[link widoczny dla zalogowanych], 3O Kong Daliang prefabricated began in November, in order to shorten the maintenance cycle to ensure quality,[link widoczny dla zalogowanych], speed up the construction progress on the beams of a steam raising. When the beam after resting, warming, thermostat, cooling and other maintenance process, opened tarps, found that many beam appears at the top of the crack,[link widoczny dla zalogowanych], crack ranging from 1 to 4, the crack width of 0.1 ~ 0.2mm, the basic distribution across the beam in the , 1 / 4 across and 3/4o concrete due to temperature difference between inside and outside. In the winter the construction process, because the outside temperature is lower, while the beam due to hydration heat of concrete reasons have a great heat, when the linoleum lifted, the concrete case of the cold surface of the contraction occurred within the concrete due to hydration heat has not completely disappeared and there is a greater temperature difference between inside and outside,[link widoczny dla zalogowanych], creating a phenomenon of the expansion outside the shrink, causing cracks in the concrete surface. o roof beam is inconsistent with the web contraction, thinner when the tarpaulin roof opened, the roof of the cooling will be faster than the web, the contraction will be greater than, faster than the web,[link widoczny dla zalogowanych], resulting in a top of the cracks. 0 when the temperature gradient of excessive maintenance. According to the construction at the time records and supervision Check. part of the beam temperature gradient in the text / border Mingchang 10 ~ 5 ~ C. According to the \the beam surface engineering factor of 8, so more than the specification. precautionary measures to strengthen the conservation management of concrete beams. in the beam concrete temperature cooled to close when the outside temperature before removal of the template and the insulation layer; when the concrete and the outside temperature but the difference is greater than 1O ℃ to remove the template. concrete surface should be covered, and slowly cooling it. tarpaulin prohibited opened ahead of schedule. strictly control the heating and cooling gradient. strictly in accordance with regulatory control of heating and cooling gradient. to avoid the expansion of cracks in the heating process and shrinkage cracks in the cooling process. Conclusion of the above facts show that the preventive measures adopted after the Green Bank beam construction of the viaduct in the later does not appear in the cracks and then, effectively solve the prestress beam crack winter issue of steam curing. Author: Seven Bridge Group Co., Ltd. Hebei Branch
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