回收轮胎聚合物纤维混凝土高温损伤超声特性研究

Study on Ultrasonic Characteristics of High Temperature Damage of Recycled Tyre Polymer Fiber Reinforced Concrete

为了研究回收轮胎聚合物纤维(RTPF)和高温作用对混凝土损伤超声特性的影响,对不同温度(20℃、105℃、250℃、400℃、600℃)作用后不同掺量(0 kg/m^(3)、0.6 kg/m^(3)、1.2 kg/m^(3)、2.4 kg/m^(3)、4.8 kg/m^(3))的RTPF混凝土试件进行超声检测,分析超声波通过混凝土试件的声速、波形、频谱及其能量分布的变化规律。结果表明:高温作用后混凝土中超声波声速降低,波形发生畸变,主频幅值降低,超声波能量向低频段聚集;RTPF混凝土抗压强度的变化趋势和超声特性反映的混凝土损伤演化趋势相同;温度达到RTPF熔点后,掺量为1.2 kg/m^(3)的RTPF混凝土的抗压强度最大,声速最大,低频段的超声波能量占比最小;SEM测试表明高温后RTPF发生软化和熔化,提高了混凝土的透气能力,减小了孔隙蒸气压力,减小了混凝土高温爆裂损伤。研究成果可为RTPF混凝土高温损伤机理研究提供参考。

In order to study the influences of recycled tyre polymer fibers(RTPF)and high temperature treatment on the ultrasonic characteristics of concrete da-mage,this work applied the ultrasonic method to test the concrete specimen with various fiber dosages(0 kg/m^(3),0.6 kg/m^(3),1.2 kg/m^(3),2.4 kg/m^(3),4.8 kg/m^(3))under different temperature(20℃,105℃,250℃,400℃,600℃),and then analyzed the change rules of acoustic velocity,waveform,spectrogram and energy distribution when the ultrasonic wave passed through the concrete specimen.The experimental results indicate that after high temperature,there has been a decrease in the acoustic velocity and the amplitude of main frequency of concrete with different fiber dosages;meanwhile,the waveform is distorted and the energy of ultrasonic is concentrated in the low-frequency stage.The change trend of compressive strength of RTPF reinforced concrete is the same as the damage trend reflected by ultrasonic characteristics.After the temperature reaches the melting point of RTPF,the compressive strength and the acoustic velocity of RTPF concrete with 1.2 kg/m^(3) fiber dosages get the largest,and the proportion of ultrasonic energy in low frequency band gets the smallest;SEM test shows that RTPF softens and melts after high temperature treatment,which can improve the air permeability of concrete,reduce the pore steam pressure,and then make the high-temperature burst damage of concrete reduced.The research results can provide a reference for the study of high-temperature damage mechanism of RTPF reinforced concrete.