纤维对再生砖混ECC力学性能及微观结构的影响

Effect of Fiber on Mechanical Properties and Microstructure of Recycled Brick Concrete ECC

为促进不同粒径再生砖混骨料的多元化利用,本试验采用再生砖混细骨料完全代替石英砂,采用不同掺量聚丙烯纤维制备再生砖混工程水泥基复合材料(ECC),研究其受力破坏特征、强度影响机理及微观结构对力学性能的影响。结果表明:未掺纤维的再生砖混ECC的失效模式为脆性破坏,而掺纤维的再生砖混ECC受拉时具有明显的应变硬化特征,随着纤维掺量的增加,其抗折强度、极限抗拉强度和极限拉应变持续增大,抗压强度呈先增大后减小趋势,表现出良好的延性和韧性破坏特征;再生砖混ECC的孔隙率在11.28%~13.68%,通过SEM观察,发现纤维与再生砖混ECC黏结性能较好,纤维破坏模式主要为拔出和拉断破坏,开裂后应变硬化拉伸幅度和拉伸强度低于普通ECC混凝土;新旧浆体界面黏结性能相对薄弱,破坏时微裂缝容易在界面过渡区产生和发展。

In order to promote the diversified utilization of recycled brick concrete aggregate with different particle sizes,recycled brick concrete fine aggregate was used to completely replace quartz sand,and mixed with different content of polypropylene fiber to prepare recycled brick concrete engineering cementitious composites(ECC).The effects of failure characteristics,strength influence mechanism and microstructure on mechanical properties were studied.The results show that the failure mode of specimens without fiber is brittle failure,and recycled brick concrete ECC with fiber has obvious strain hardening characteristics during tensile stress.With the increase of fiber content,the flexural strength,ultimate tensile strength and ultimate tensile strain of recycled brick concrete ECC continue to increase,and the compressive strength increases first and then decreases,which shows good ductility and ductile failure characteristics.The porosity of recycled brick concrete ECC is 11.28%~13.68%.Fiber has good bonding property with recycled brick concrete ECC observed by SEM,the fiber failure modes are mainly pull-out and tensile failure,and the strain hardening tensile amplitude and tensile strength after cracking are lower than that of ordinary ECC concrete.The interface bonding property of old and new mortar is relatively weak,and micro-cracks are easy to occur and develop in the interface transition zone during failure.