纳米改性再生骨料混凝土破坏机理研究

Investigation on Failure Mechanism of Nanomodified Recycled Aggregate Concrete

关键词:  再生骨料混凝土  纳米材料  破坏机理  裂纹演变  界面过渡区

Key words:  recycled aggregate concrete（RAC）  nanomaterial  failure mechanism  crack propagation  interfacial transition zone(ITZ)

摘要:

对再生骨料混凝土(RAC)进行了裂纹演变规律和不同掺量的纳米硅溶胶、纳米碳酸钙改性试验研究.采用高速摄像仪实时观测了不同水灰比(mW/mC=04,05和06)和不同再生骨料替代率下再生骨料混凝土试块单轴受压加载过程中的裂纹开展信息，对不同纳米材料改性的RAC进行了扫描电镜和压汞测试，并对其界面过渡区的微观形貌和孔结构进行了对比分析.结果表明：RAC的受压破坏大多为新老界面过渡区破坏，裂纹往往最先由此处开展，具体开裂位置取决于新老砂浆的相对强度；裂纹围绕再生骨料周边逐步向四周扩展和贯通，最终导致试块纵向劈裂破坏；纳米硅溶胶能够很好地改善RAC界面过渡区微观结构，提高RAC抗压强度，而纳米碳酸钙难以进入RAC的界面过渡区，很难有效改善界面孔结构，因此未能明显提高RAC抗压强度.

Abstract:

The crack evolution of recycled aggregate concrete(RAC) and the performance of RAC after incorporation of different amount of nanoparticles(nanosilica sol and nanolimestone) were studied. Under uniaxial compression, the crack development of RAC specimens with different water cement ratios(04, 05 and 06) and aggregate replacement ratios were observed by high speed camera. Scanning electron microscopy(SEM) observation and mercury injection test were conducted for studying the microscopic morphology and pore structure of the interfacial transition zone(ITZ) of nanomodified RAC and the influences of different mass fraction of nanoparticles and different treatment processes on it were analyzed. The results indicate that the crack of RAC is usually derived from new ITZ or old ITZ(determined by the weaker one) and then it gradually extends to the surrounding area. The evolution of crack eventually leads to the longitudinal splitting failure of the RAC. Nanosilica sol could improve the microstructure of ITZ. Therefore, the strength of nanosilica sol modified RAC was enhanced. But the improvement by nanolimestone is not very significant for it cant enter the interface transition zone to fill the pore in it.