陶瓷纤维增强混凝土高温损伤的超声特性

Ultrasonic properties of fire damage of ceramic fiber reinforced concrete

通过超声波检测和抗压强度试验对高温后陶瓷纤维增强混凝土(CFRC)的损伤特性进行了研究,分析了加热温度和冷却方式对抗压强度、纵波波速和主频带来的影响。分析表明,随着温度的升高,CFRC性能不断劣化,抗压强度、纵波波速及主频总体呈下降趋势;400℃为CFRC性能突变的临界温度,400℃之前,其劣化程度较小,且抗压强度与主频在400℃时有所回升,400℃之后,劣化速率明显增大,结构性能急剧下降;同自然冷却情况相比,浇水冷却后CFRC各项性能指标下降更为严重;纵波波速在1.0～3.5km/s内与抗压强度具有正相关性,在3.5～4.5km/s内两者相关性不确定。利用纵波波速定义的损伤变量能较好地反映高温后CFRC内部损伤的演化规律。

The damaged characteristics of ceramic fiber reinforced concrete （CFRC） after elevated tempera- ture were studied by ultrasonic testing and compressive strength testing. The influences of the tempera- ture and the cooling methoda on the compressive strength, longitudinal wave velocity and main frequency were analyzed. The results indicate that the properties of CFRC deteriorate, and that the compressive strength, the longitudinal wave velocity, and the main frequency decrease with the rising of temperature. The critical temperature of CFRC is 400 ＂C. The degree of deterioration of CFRC is relatively lower before 400 ＂C, the longitudinal wave velocity and the main frequency increase in 400 ＂C, and the rate of deteriora- tion and the properties of CFRC decrease sharply above 400 ＂C. The properties of specimens cooled by spraying water are worse than those of specimens cooled naturally. When the longitudinal wave velocity ranges from 1.0 to 3.5 km/s, there is a positive correlation between it and the compressive strength, and this relationship becomes uncertain when it is in 3.5--4. 5 km/s. The damage factor defined by the longitudinal wave velocity can well reflect the regularity of the damage evolution of CFRC after elevated temperature.