UHPC与普通混凝土试件界面黏结抗冻性能试验研究

超高性能混凝土(UHPC)因为其较高的强度和优良的耐久性被认为是极具潜力的结构修补用材料之一。同时,UHPC与普通混凝土(NC)之间的界面黏结性能,是影响UHPC在混凝土加固修复工程中应用可靠性的关键因素。针对严寒环境,本试验对超高性能混凝土与普通混凝土(以下简称UHPC-NC)黏结试件开展－60 ℃的冻融循环试验,分析冻融循环后试件的宏观形态变化、质量变化率。通过黏结强度试验,获得界面的黏结强度以及相应的界面破坏模式。试验主要分析－60 ℃冻融循环对UHPC-NC试件界面黏结性能的影响,以及界面的不同处理方式(钢丝刷刷毛、高压水射流冲毛及劈裂)对抗－60 ℃冻融循环作用的影响,同时,对冻融作用下UHPC-NC试件的界面损伤机理进行初步探索。试验结果表明:－60 ℃冻融循环对UHPC-NC试件黏结强度有较大影响,劈裂组试件的界面黏结强度在经历10次、15次、20次冻融循环后分别下降为界面黏结基准强度的72.94%、55.62%及44.33%,界面黏结强度呈现先急速下降再缓慢下降的趋势;界面粗糙度越高,界面的剩余黏结强度越大,经历20次冻融循环后,劈裂组试件的剩余黏结强度为高压水射流冲毛试件的2.03倍。

Experimental Study on Interfacial Antifreeze Performance of UHPC and Normal Concrete

Ultra high performance concrete (UHPC) is considered to be the most promising material for structural repair due to its high strength and excellent durability. At the same time, the interfacial bonding performance between UHPC and normal concrete (NC) is the key to the reliability of applying UHPC in concrete reinforcement and repair engineering. To achieve the interfacial behavior of UHPC-NC under serve cold environment, freeze-thaw cycle tests were carried out on UHPC-NC bonding specimens at －60 ℃. The macroscopic morphological changes and mass change rates of the specimens after the freeze-thaw cycles were obtained. Meanwhile, based on the tensile bonding test, the bonding strength and failure mode were analyzed. Moreover, the interface damage mechanism of UHPC-NC specimen under freeze-thaw action was also preliminarily explored. The influence of －60 ℃ freeze-thaw cycles on the interface bonding performance of UHPC-NC specimens, and the influence of different treatment methods of the interface (brush, water jet and splitting) against the －60 ℃ freeze-thaw cycles were presented. The test results show that the －60 ℃ freeze-thaw environment has a great influence on the bonding strength of UHPC-NC specimens. The interface bonding strength decreases rapidly first and then slowly. After 10 freeze-thaw cycles, 15 freeze-thaw cycles and 20 freeze-thaw cycles, the interface bond strength of the splitting group decrease to 72.94%, 55.62% and 44.33% of the benchmark interface bond strength, respectively. The higher the interface roughness, the greater the residual bond strength of the interface. After 20 freeze-thaw cycles, the bond strength of the splitting group is 2.03 times than that of the water jet sample.