活性粉末混凝土高温后性能劣化及微观结构

Performance Degradation and Microscopic Structure of Reactive Powder Concrete after Exposure to High Temperature

摘要:

研究了活性粉末混凝土（RPC）从常温升温到800 ℃后的外观变化、质量损失、抗压强度损失等劣化过程.采用超声检测评估了RPC高温后的损伤，建立了超声参数与目标温度、抗压强度损失率的关系，并用扫描电镜（SEM）观察了不同温度后RPC的微观结构变化.结果表明：随着温度的升高，试件的颜色由深变浅，质量损失率增大，抗压强度损失率增大；采用相对波速和损伤度来评估RPC高温后的性能劣化是可行的，回归公式拟合度较高，而相对主频和相对幅值表征试件的性能变化不显著；基体的微观形貌在300 ℃后随温度升高而不断恶化，宏观体现为抗压强度损失，800 ℃后抗压强度损失率超过80%，RPC微观结构的劣化是其宏观力学性能劣化的根本原因.

Abstract:

Reactive powder concrete（RPC） was made for studying the process of performance degradation from ordinary temperature to 800 ℃， which including appearance change， mass loss， and compressive strength loss. Ultrasonic test was used to evaluate the damage of RPC after high temperature. Besides， the relationship between the ultrasonic parameters and target temperature as well as cubic compressive strength loss rate were analyzed. The microstructure of RPC after high temperature was also observed by scanning electron microscopy（SEM）. The results show that with the increase of target temperature， the color of specimen changes from dark to light， while the mass loss rate and the cubic compressive strength loss rate gradually increases. It is feasible to use relative wave velocity and damage degree to evaluate the damage of RPC after high temperature. The regression formula has a great fitting degree. On the contrary， the relative dominant frequency and relative amplitude have little correlation with the change of specimen properties. The microstructure of RPC deteriorates continuously with the increase of temperature after 300 ℃， and the macroscopic reflection is the loss of strength， which exceeds 80% after exposure to 800 ℃. The deterioration of the RPC microstructure is the root cause of the macromechanical property recession.