蒸养再生骨料混凝土断裂声发射特征*

为研究蒸汽养护对再生骨料混凝土断裂过程损伤特征的影响,开展了再生骨料混凝土三点弯断裂试验,并采用声发射技术对损伤过程进行了监测分析。结果表明,蒸养降低了再生骨料混凝土断裂峰值荷载,断裂过程中声发射信号强度低于标准养护试件。声发射振铃计数、撞击数、b值等参数能够准确反映再生骨料混凝土断裂过程损伤演变规律。加载上升阶段,声发射信号活动性很低,试件内以微裂纹的形成为主,加载至荷载峰值,声发射振铃计数累计值增长呈现平缓阶段,混凝土内微裂缝的聚合会持续一段时间。峰值后荷载迅速降低阶段声发射信号最活跃,为裂缝迅速发展的过程。峰后荷载缓慢降低的过程,声发射信号活跃性降低,裂缝扩展至试件顶部区域,主要是宏观裂缝的开展,不再产生新的裂缝。

Acoustic emission characteristics of fracture of steam cured recycled aggregate concrete

In order to study the influence of steam curing on the damage characteristics of recycled aggregate concrete in the fracture process, the three-point bending fracture test was carried out, and the fracture process was monitored and analyzed by acoustic emission technology. The results show that steam curing reduces the fracture peak load of recycled aggregate concrete, and the AE signal intensity of steam cured recycled aggregate concrete during fracture is lower than that of standard curing specimenss. Acoustic emission ring count, impact number and other parameters can reflect the damage evolution law of recycled aggregate concrete in the fracture process. In the loading rising stage, the activity of AE signal is very low, and the formation of microcracks in the specimen is dominated. When the load reaches the peak value, the growth of the cumulative value of AE ringing count presents a gentle stage, and the aggregation of microcracks in concrete will last for a period of time. The AE signal is the most active in the stage of rapid load reduction after the peak value, which is the process of rapid crack development. The activity of AE signal decreases in the process of slow reduction of post peak load. This process is mainly the development of macro cracks, which extend to the top area of the specimen, and no new cracks are generated.