Application of recycled coarse aggregate concrete (RAC) will generate considerable environmental benefits. However, the properties of RAC must be studied before being adopted in structures. In this research, the failure process and damage assessment of RAC under compression were investigated by applying acoustic emission (AE) technology. The variables include loading rates, maximum coarse aggregate sizes, and water–cement ratios (w/c). Meanwhile, an innovative approach called stage cumulative proportion (SCP) analysis of AE result was put forward. Subsequently, the damage of RAC under compression was evaluated based on the rate process theory. The results demonstrated that void compaction and original crack expansion occurred first in the test and then the stable microcracking in interfacial transition zone (ITZ) and unstable cracking in mortar, and finally, there is the macrocrack expansion followed by the fracture. It was found that AE counts and energy were mainly produced before the peak stress was reached. The increase in loading rate caused the AE counts and energy to increase in stable microcracking of ITZ but decreased in unstable cracking of mortar. Increasing the w/c would also affect the AE results in these stages, but the effect was the opposite to the loading rate. Besides, an increase in coarse aggregate sizes would increase the AE counts and energy in unstable cracking of mortar and decrease in macrocrack expansion. In addition, a polynomial expression of the relationship between AE parameters and stress level was established. Then, an evaluation criterion was proposed based on the expressions and the rate process theory.

中文翻译：

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压缩状态下再生骨料混凝土的声发射行为及损伤评估

再生粗骨料混凝土（RAC）的应用将产生可观的环境效益。但是，在结构中采用RAC之前，必须对其进行研究。在这项研究中，通过应用声发射（AE）技术研究了RAC在压缩状态下的失效过程和损伤评估。这些变量包括加载速率，最大粗骨料尺寸和水-水泥比（w / c）。同时，一种称为阶段累计比例的创新方法提出了AE结果的（SCP）分析方法。随后，基于速率过程理论评估了压缩状态下RAC的损伤。结果表明，首先在试验中发生空隙压实和原始裂纹扩展，然后在界面过渡区（ITZ）产生稳定的微裂纹，然后在砂浆中产生不稳定的裂纹，最后出现宏观裂纹，随后出现断裂。发现AE计数和能量主要在达到峰值应力之前产生。加载速率的增加导致AE计数和能量在ITZ稳定的微裂纹中增加，但在灰浆的不稳定裂纹中降低。增加w / c也会影响这些阶段的AE结果，但效果与加载速率相反。此外，粗骨料尺寸的增加会增加砂浆不稳定开裂的AE数量和能量，并降低大裂纹的扩展。此外，建立了声发射参数与应力水平之间关系的多项式表达式。然后，基于表达式和速率过程理论，提出了一种评价标准。