再生混凝土材料阻尼性能研究

Damping capacity of recycled concrete

针对再生混凝土阻尼性能,通过三点弯曲梁大尺寸材料阻尼测试装置,试验研究再生粗骨料(RecycledCoarse Aggregate,RCA)的取代率、RCA粒径、改性掺合料、激振力频率及幅值等因素对再生混凝土弹性阶段损耗因子影响。结果表明,再生混凝土损耗因子分别随RCA取代率的增加及RCA平均粒径的减小而增加;随激振频率的增加及激振力幅值的减小而减小;与普通混凝土相比,再生混凝土的损耗因子增加3%～10%;复掺钢纤维+橡胶粉、粉煤灰+矿粉改性后的再生混凝土损耗因子较改性前分别增加45.8%及30.3%,阻尼增强效果显著。RCA与新硬化水泥砂浆间薄弱界面层的粘滞滑移变形、界面层应力集中所致微裂缝的产生与发展及内部裂隙间的摩擦作用增加了再生混凝土的阻尼耗能。因此,当再生混凝土用于大宗结构性材料时,综合考虑其强度及阻尼性能,RCA取代率不宜超过50%,并可复掺粉煤灰+矿粉进行综合改性。

The method of 3-point bending beam damping measurement was used in experiments to study the influence of replacement ratio and grain size of recycled coarse aggregate (RCA), modified admixtures, frequency and amplitude of exciting force on the loss tangent of recycled concrete in elastic stage. The experimental results show that the loss tangent of recycled concrete is increased by increasing replacement ratio and decreasing grain size of RCA, and is decreased by increasing frequency and decreasing amplitude of exciting force. The loss tangent of recycled concrete is increased by 3%~10% compared with ordinary concrete, in addition, the loss tangent of recycled concrete is further increased by 45.8% and 30.3% respectively due to admixtures of steel fiber plus rubber powder and fly ash plus modified mineral powder. This increase may be attributed to the viscous deformation among the weak interfaces of RCA and new hardened cement, as well as the frictional damping energy consumption of micro cracks induced by the non-uniform stress distribution. It is indicated that, if comprehensively considering the optimization of strength and damping ability, the replacement ratio of RCA should be less than 50% and fly ash plus, mineral powder could be taken as admixtures to further modify the strength and damping ability.