界面剂对新旧混凝土界面粘结性能影响的试验研究
Effect test of interface agent on bonding of old and new concrete

为研究界面剂对新旧混凝土界面粘结强度的影响及其粘结机理，进行未涂刷界面剂与涂刷水泥净浆、掺10%粉煤灰水泥浆、掺10%U型膨胀剂水泥浆、掺10%丁苯乳液水泥浆等5组Z形试件的直剪试验，测定各试件新旧混凝土界面的剪切强度；同时，采用显微硬度仪与扫描电子显微镜，分析界面过渡区的显微硬度值分布规律、微观结构形貌以及水化产物种类与分布特征. 试验结果表明，新旧混凝土界面为薄弱区域，涂刷合适的界面剂可优化孔结构，改善界面密实度，增大新旧混凝土在微观层面上的机械咬合作用. 此外，常用的4种界面剂中，水泥净浆和掺U型膨胀剂水泥浆的性价比相对较高.
Direct shear experiments of 5 groups of Z-shape adhesive specimens without and with interface agent (including cement paste，cement paste with 10% fly ash，cement paste with 10% U-type expansion agent and cement paste with 10% styrene butadiene rubber emulsion) were carried out to test the bonding strength between old and new concrete. In addition，micro hardness，microstructure and hydration products of interfacial transition zone (ITZ) were analyzed by micro hardness test and SEM observation. The results show that old and new concrete interface is a weak area，interface agent can increase the bonding strength of the interface by optimizing pore structure，increasing mechanical bite action at the microscopic level and improving the interface compactness. The cost-performance ratios of cement paste and cement paste with UEA are relatively high among four typical interface agents