基于超声检测的废弃纤维再生混凝土弹性模量试验研究

为研究长期持荷损伤后再生骨料取代率和废弃纤维掺入对再生混凝土弹性模量的影响规律,制备了再生骨料取代率为0、50%、100%,废弃纤维体积掺入量为0.08%的废弃纤维再生混凝土试件,进行了混凝土标准弹性模量试验和超声波无损检测试验。结果表明：弹性模量与超声波速呈线性正相关,在宏观尺度上表现为抵抗弹性变形的能力减小,在细观尺度上表现为混凝土和再生混凝土中界面强度降低。纤维的桥接作用可以阻断微裂缝的开展抑制废弃纤维再生混凝土内部损伤的演化,从而提高了再生混凝土的弹性模量。超声波速随着应力水平和时间的增加而减小。采用中国、美国、欧洲规范计算废弃纤维再生混凝土弹性模量,中国规范《混凝土结构设计规范》(GB 50010—2010)和欧洲规范《混凝土结构设计》(BS EN 1992-1-1—2004)计算值与超声检测值相差0.9%～8.4%和0.3%～12%,超声波无损检测法可进行长期损伤后的再生混凝土和废弃纤维再生混凝土弹性模量的定量分析。

Experimental study on elastic modulus of waste fiber recycled concrete based on ultrasonic testing

In order to study the effects of recycled aggregate replacement rate and waste fiber addition on the elastic modulus of recycled concrete after long-term load-bearing damage, waste fiber recycled concrete specimens with recycled aggregate replacement rate of 0, 50% and 100% and waste fiber volume addition of 0.08% were prepared, and the elastic modulus and ultrasonic nondestructive tests of concrete were carried out. The results showed that the elastic modulus has a linear positive correlation with the ultrasonic velocity, which shows that the resistance to elastic deformation decreases in the macro scale, and the interfacial bond strength between concrete and recycled concrete decreases in the meso-scale. The bridging effect of fibers can block the development of micro-cracks and inhibit the evolution of internal damage of waste fiber recycled concrete, thereby increases the elastic modulus of recycled concrete. Ultrasonic velocity decreases with the increase of stress level and time. The ultrasonic velocity decreases with time. The elastic moduli of waste fiber recycled concrete were calculated by GB 50010-2010, ACI 308-05 and BS EN 1992-1-1-2004. The difference between Chinese and European code and ultrasonic testing value is 0.9%~8.4% and 0.3% ~12%, respectively. Ultrasonic nondestructive testing method can provide quantitative analysis for long-term detection of elastic modulus after damage.