混凝土内部气泡对其强度和耐久性影响的试验研究

An Experimental Study of the Effects of Internal Bubbles on the Strength and Durability of Concrete

研究了混凝土内部气泡对混凝土物理、力学性能以及耐久性的影响，并探讨了其影响规律及作用机理。结果表明随着引气剂掺量的增加，气泡数量随之增加，新拌混凝土的坍落度不断增大，硬化混凝土的含气量也相应提高，抗冻性能、抗渗性能得以改善，但抗压强度呈下降趋势。在本试验条件下，当水灰比为0．40、引气剂掺量为0．7／万、坍落度在50～70mm时，引气剂对混凝土强度造成的负面影响较小，28d抗压强度损失率较低；引气剂掺量为1．2／万、小坍落度时，引气剂显著改善混凝土抗冻性能；当引气剂掺量为1．0／万时，由于混凝土中细小气泡分布均匀且独立而不相通，因而具有较好的抗渗性。

In the light of the construction method for the casting-in-place of the 170 m-span steel-tube-concrete arch bridge of the south loop of Chengde City,the ANSYS software is used to analyze the effects of four different sequences of removing sup- ports on the forces loaded on and the deformation of the arch ribs of the steel-tube-concrete arch bridge. According to the result of the analysis, adopted is the first scheme,which means that the removal of the supports should start with the posts at the top of the arch,and should be performed gradually and symmetrically to the feet of the arch in the normal order,in which case the deformation of each controlled cross-section is uniform and minimum.