再生混凝土技术研究是当今时代重要的课题之一。影响再生混凝土广泛推广的因素有很多，首先是再生骨料周围往往附着着砂浆，使其产生弱面，影响了再生混凝土的质量；其次，传统的剔选方法会使骨料内部微裂纹增多。同时，剔选工艺还不成熟，通常伴随着噪音、粉尘污染。因此，再生骨料剔选技术的改进显得尤为重要。本文将提出一种微波辅助剔选骨料的新方法。 本文首先在理论上对混凝土的破坏机理进行分析，阐述微波照射下混凝土骨料和砂浆界面（A-M界面）的损伤机理；在此基础上采用试验和数值模拟的方法分析了微波照射混凝土骨料界面的损伤规律及影响因素。具体研究内容及结论如下： （1）天然骨料混凝土和经微波照射不同时间后的再生骨料重新拌合的再生混凝土的抗压强度对比分析，说明微波辅助剔选的方法能够显著改善再生混凝土的质量。 （2）对微波照射后的混凝土A-M界面进行细观电镜扫描试验。可以看出未经微波照射的界面本身就存在一定的裂隙， 微波照射5min后界面裂隙扩展，随着照射时间的增长，裂隙数量也有所增加，因此，微波照射对界面产生很大程度的损伤。 （3）微波照射后混凝土吸水率试验分析发现，照射0~5min这段时间之间，吸水率曲线呈增长趋势，随着照射时间增加，混凝土的吸水率曲线基本平稳。 （4）通过COMSOL有限元软件模拟分析，照射时间是影响剔选效果的重要因素。在一定范围内，A-M界面的损伤程度会随着微波照射时间的增长而增大；骨料形状对剔选效果具有一定的影响，主要是因为方形骨料的最高温度和最大应力值均出现在尖端处，使骨料尖端处产生较大的压应力，出现初始裂纹引起损伤，随着微波照射时间的增长，尖端处裂纹逐渐扩展至界面处，并与界面处裂纹贯通，有利于砂浆的剥落；砂浆厚度对剔选效果具有一定的影响，砂浆厚度较大的骨料界面在相同的微波照射条件下产生的热应力较小，即发生破坏所需吸收的微波能量较大。

The research on the technology of recycled concrete is one of the important issues in modern times. There are many reasons result in that recycled concrete cannot be promoted in a large scale, on the one hand, the old mortar is still adhering on the surface of the recycled aggregate, which will produce weakness plane, and affect the quality of recycled concrete; on the other hand, the traditional selecting technology will increase the quantity of cracks. At the same time, the selecting technology of concrete is not mature yet, which accompanied with noises and dust pollution usually. Therefore, it is particularly important to improve selecting technology of recycled aggregate. A new method of microwave-assisted selecting aggregate will be submitted in this paper. Firstly, the failure mechanism of concrete is analyzed according to theories in this paper, and the damage mechanism of concrete aggregate and mortar surface(A-M surface) under microwave irradiation; on this basis, the damage laws and influence factors of concrete aggregate and mortar under microwave irradiation are analyzed by the means of tests and numerical simulation. The concrete research contents and results are as follows: (1)The strength comparsion of ordinary concrete and recycled concrete shows that microwave-assisted selecting technology can improve the quality of recycled concrete significantly. (2)The SEM test of concrete A-M surface under microwave irradiation is carried out. There are certain cracks in the surface without microwave irradiation, after 5 minutes, the cracks is going to extend, with the increase of microwave irradiation time, the quantity of cracks is increased, therefore, microwave irradiation can result much damage to the surface. (3)The changes of concrete water absorption under microwave irradiation show that the curve of water absorption is showed an increasing trend after 5 minutes, with the increase of microwave irradiation time, the curve of water absorption is showed smoothly basically. (4)Through COMSOL finite element analysis, microwave irradiation time is the important factor which affects the selecting effect. In a certain scope, the damage degree is increasing with the increase of irradiation time; the shape of aggregate has a certain influence to selecting effect, the main reason is that the highest temperature and maximum stress of square aggregate appear in sharp point, which will induce the greater compressional stress, and the appearance of initial cracks will induce the damage, with the increase of irradiation, the cracks in sharp point expand to the surface gradually, and they will form the coalescence with the cracks in the inter face, which will be beneficial to the peeling of mortar; the thickness of mortar has a certain influence to selecting effects, the aggregate with greater mortar thickness will produce the smaller thermal stress under the same microwave irradiation and the more energy is needed to failure.