Combining with flexural-tensile tests of wet sieving and three-graded concrete in Xiaowan arch dam,feature parameters and waveforms of acoustic emission (AE) signals under action of third-point flexural-tensile were acquired using a full-digital acoustic emission system. The law of acoustic emission activities in each loading stages was analyzed, the statistical features of the peak frequencies and the frequency centroids calculated from the FFT power spectra of the acoustic emission waves were compared, the damage and fracture mechanisms were identified based on the acoustic emission parameters, and the localized failure zones of microcracks were also located using the commercial software AEwin. It was found in a three-graded concrete comparing with a wet sieving concrete that acoustic emission in the former is easier to induce damage, and lower b value of acoustic emission is observed in each loading stages; the peak frequencies of the acoustic emission in the former appear in frequency bands of 100 kHz ～125 kHz and 225 kHz ～250 kHz, and the frequency centroids are lower than those of the latter; two specific mechanisms are identified in the former but within the same time duration one is identified in the latter; the localized zone of microcrack in the former is larger than that in the latter.%结合小湾拱坝湿筛和三级配混凝土静态弯拉试验,采用全数字化声发射系统采集了两种混凝土在三点弯曲荷载作用下从加载至最终破坏的声发射特征参数和波形.对比分析了各加载阶段的声发射活动发展规律及声发射波形FFT功率谱峰值频率和频率质心的统计特征,识别了两种混凝土以声发射特征参数为基础的损伤断裂机制,采用商业声发射软件对微裂缝局部化区域进行了定位.结果表明,三级配混凝土与湿筛混凝土相比,具有以下声发射特征:①更易诱发损伤,在各个加载阶段具有较小的声发射b值;②声发射撞击峰值频率在100 kHz-125 kHz频段及225 kHz-250kHz频段也有分布,同时频率质心比湿筛混凝土低;③在湿筛混凝土的一个特定机制的持续时间范围内,三级配混凝土识别为两个机制;④微裂缝的局部化区域范围大于湿筛混凝土.
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