冻融作用对自密实轻骨料混凝土声发射特性影响EI北大核心CSCD

为研究冻融后自密实轻骨料混凝土单轴压缩下的声发射(AE)特性,对未掺引气剂的自密实轻骨料混凝土试件进行0次、50次、100次快速冻融试验。结果表明:随着冻融次数增加,试件轴压应力-应变曲线趋于完整,峰值应力有明显降低;声发射峰值频率主要位于15 kHz~45 kHz,85 kHz~105 kHz,235 kHz~255 kHz和285 kHz~320 kHz这4个“优势频段”区间,对应于混凝土内部预存裂纹或孔隙压密,骨料/砂浆界面增强层的开裂,粗骨料断裂破坏以及砂浆的开裂。受冻后的试件在轴压作用经历拉伸裂缝与剪切裂缝之间的交替转化,最终形成主裂缝导致破坏。冻融作用以及应力水平变化对AE信号源分布有较大影响,随着应力水平的增加,AE信号源趋于活跃,且在试样断裂面有聚集趋势。

EFFECT OF FREEZE-THAW ACTION ON ACOUSTIC EMISSION CHARACTERISTICS OF SELF-COMPACTING LIGHTWEIGHT AGGREGATE CONCRETE

To study the acoustic emission (AE) characteristics of self-compacting lightweight aggregate concrete (SCLC) under uniaxial compression after freeze-thaw action, 0, 50 and 100 rapid freeze-thaw tests are carried out on self-compacting lightweight aggregate concrete specimens without air entraining agent. The results show that: with the increase of freeze-thaw cycles, the uniaxial compressive stress-strain curves of the specimen tend to be complete, and the peak stress decreases significantly. The peak frequency of AE is mainly located in the four 'dominant frequency bands' of 15 kHz-45 kHz, of 85 kHz-105 kHz, of 235 kHz-255 kHz and of 285 kHz-320 kHz, corresponding to the compression of pre-existing cracks or pore in concrete, the cracking of aggregate/paste interface reinforcement layer, the penetration fracture of coarse aggregate and the cracking of mortar, respectively. Under the action of uniaxial compression, the freeze-thawed specimens undergo the alternating transformation between tensile cracks and shear cracks, and finally form the main crack which leads to failure. Freeze-thaw action and the variation of stress level have a great influence on the distribution of AE signal source. With the increase of stress level, AE signal tends to be active and gathers on the fracture surface of the sample.