再生骨料混凝土梁的阻尼性能及其机理分析

混凝土构件的阻尼性能与其混凝土骨料组分的特性密切相关.以不同再生骨料取代天然砂石,采用悬挂梁自由振动衰减法测试再生骨料混凝土梁弹性阶段一阶阻尼比,并探讨其与混凝土强度、弹性模量间的关系;通过氮气吸附法和扫描电镜测试再生骨料混凝土的孔隙结构与界面特征,分析其阻尼机理.结合文献数据的对比分析表明:相比于天然骨料混凝土梁,再生骨料混凝土梁的阻尼比显著增大,阻尼比随混凝土强度、弹性模量的减小而增大,骨料特性尤其是骨料表面改性对混凝土阻尼性能影响显著.再生骨料取代天然砂石,增大了混凝土的总孔体积、平均孔径,增加了薄弱界面过渡区,界面过渡区的滑移摩擦及孔隙的柔性缓冲作用,是再生骨料混凝土梁阻尼增加的主要因素.

Damping Property and Mechanism of Recycled Aggregate Concrete Beams

The damping properties of concrete members are closely related to concrete aggregate characteristics. Replacing natural sand and crushed stone with different recycled aggregates (RA), the first damping ratio of suspension beam of recycled aggregate concrete (RAC) in elastic stage was tested by using the free vibration attenuation method, and the relationship between damping ratio and concrete strength/elastic modulus was analyzed. Moreover, the RAC pore structure and interfacial transition zone (ITZ) characteristics were investigated by using the nitrogen adsorption method and scanning electron microscopy (SEM), and the damping mechanism was discussed. The results show that the damping ratio of RAC beams increases significantly, when compared with that of natural aggregate concrete (NAC) beams, and the damping ratio increases with the decrease of concrete strength and elastic modulus. The effect of aggregate property, especially the aggregate surface modification, on the concrete damping property is noteworthy. The total pore volume and average pore diameter of RAC are larger than those of NAC, and the ITZs in RAC are weaker. Therefore, the sliding and friction in ITZs and the flexible cushion action of pores result in more energy dissipation in RAC beams.