新老混凝土粘结面的抗冻融劈拉性能试验研究

采用新老混凝土粘结复合立方体试件,通过快速冻融试验,对先冻融后粘结和先粘结后冻融两种情况的新老混凝土粘结试件在水饱和状态下的冻融劈裂性能进行了试验研究,探讨了冻融循环次数、粘结面粗糙度和界面剂类型对粘结面劈裂抗拉强度的影响。界面的粗糙度为0.23￣6.9 mm,界面剂选用水泥净浆、水泥砂浆和掺加10%UEA膨胀剂的水泥净浆。试验结果表明,无论是先冻融后粘结还是先粘结后冻融的新老混凝土粘结试件,其粘结面的劈裂抗拉强度均随冻融循环次数的增加而降低,表现为冻融初始阶段的缓降和冻融循环一定次数后的陡降,特别是先粘结后冻融试件,其下降程度更加显著。根据试验,适当的粗糙度和水泥砂浆界面剂对粘结质量有较好的改善作用。在试验的基础上,对粘结面的冻融损伤机理进行了初步分析。

An experimental study on the bond splitting behavior of the interface between new-old cocretes under freeze-and-thaw cycles

Using composite cubic specimens of new-old concrete,the bond splitting behaviors of the interface of water-saturated new-old concrete under freeze-and-thaw cycles is studied,for two different situations: bonding after freeze-and-thaw,and bonding prior to freeze-and-thaw.The effects of freeze-and-thaw,roughness(0.23~6.9 mm) and adhesion agent(including cement paste,cement mortar and cement paste with 10 per cent UEA expanding agent) are investigated.The test results indicate that the bond splitting tensile strength decreases significantly with increasing number of freeze-and-thaw cycles,that the rate of decrease is greater for those specimens bonded prior to freeze-and thaw,and that appropriate roughness and cement mortar may improve the bonding strength.Based on the test results,a preliminary analysis is conducted on the mechanisms of bonding.