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对幼龄期遭受负温的预应力箱梁段进行现场试验,包括外观、120d龄期碳化深度及回弹值。结果表明,幼龄期受冻的箱梁腹板有氢氧化钙渗出,顶面局部有凸起且伴有辐射状冰晶,混凝土碳化深度超过10mm,回弹值低于50,局部甚至低于35,回弹值方差甚至超过30。与其他部位的混凝土相比,腹板底部的回弹值最低且离散性最大,同一横断面的阴面和阳面,混凝土品质相差较大,这将加剧预应力箱梁的不匀质性,使其受力更加复杂和不确定。为了保证冬期施工的混凝土质量,务必采取措施来避免其幼龄期受冻。
Field tests on prestressed box girders subjected to negative temperature in their young age, including appearance, depth of carbonation at 120 days and rebound value, were carried out. The results show that the young girders of the box girder, which have been frozen in the juvenile age, have exudation of calcium hydroxide. The top surface is convex with radial ice crystals. The carbonation depth of concrete exceeds 10 mm and the rebound value is lower than 50, 35, the rebound value of variance even more than 30. Compared with other parts of the concrete, the lowest rebound value at the bottom of the web is the highest and the dispersibility is the largest. The quality of the concrete differs greatly between the shaded and the sun-shaded surfaces of the same cross-section, which will exacerbate the inhomogeneity of the prestressed box girder Force more complicated and uncertain. In order to ensure the quality of the concrete in winter construction, measures must be taken to prevent its age from freezing.