微波辐照下铁尾矿水泥混凝土的损伤规律

程道华¹，赵之仲^1*，康宪章²，成娜¹

1.山东交通学院交通土建工程学院，山东 济南  250357；2.山东工壹建设工程有限公司，山东 济南  250306

摘要：为充分发挥铁尾矿的吸波发热特性，实现矿山固废资源高值化利用，将铁尾矿以粗骨料形式掺入水泥混凝土中，分析微波辐照作用下铁尾矿水泥混凝土的损伤规律，对铁尾矿石粒料进行X射线衍射物相分析，研究铁尾矿吸波升温机理，分析微波辐照下铁尾矿石粒料和铁尾矿水泥混凝土的温度变化，以及铁尾矿水泥混凝土在微波辐照前后下的超声波声速变化规律；采用扫描电子显微镜观察微波辐照前后铁尾矿混凝土试块的表面形貌及微观结构，研究内部微观损伤。研究结果表明：铁尾矿石中的含铁氧化物吸波能力较好，铁尾矿石和石灰石的温度均随微波辐照时间的增加而升高，升温速率随辐照时间的增加而减小，铁尾矿石的温度增幅比石灰石大；微波辐照时间相同时，铁尾矿水泥混凝土试块的温度随辐照功率的增大而升高，辐照功率为6 kW时吸波效率最高，试块辐照前后的温差随辐照时间的增加先线性升高后增速放缓；铁尾矿水泥混凝土试块的超声波声速均随辐照时间和辐照功率的增大而减小，辐照功率相同时，试块的超声波声速衰减率随辐照时间的增加先快速增大后增速放缓，辐照功率为0、2、4、6、8 kW、辐照0~5 min时，超声波声速衰减率最高可达35.29%；经微波辐照处理后，试块铁尾矿与砂浆界面过渡区产生1~3 μm的热应力裂纹并沿界面扩展。

关键词：微波辐照；铁尾矿石；超声波声速；水泥混凝土

Damage patterns of cement concrete with iron tailing undermicrowave radiation

CHENG Daohua¹, ZHAO Zhizhong^1*, KANG Xianzhang², CHENG Na¹

1.School of Civil Engineering, Shandong Jiaotong University, Jinan 250357, China；

2.Shandong Gongyi Construction Engineering Co., Ltd., Jinan 250306, China

Abstract: To fully leverage the wave-absorbing and heating properties of iron ore tailings and achieve high-value utilization of mining solid waste, this study incorporates iron ore tailings into cement concrete as coarse aggregates to investigate the damage patterns of iron ore tailing concrete under microwave irradiation. X-ray diffraction (XRD) phase analysis is performed on iron ore tailing particles to study the microwave heating mechanism. The temperature changes of iron ore tailing particles and concrete, as well as the ultrasonic pulse velocity (UPV) variations of iron ore tailing concrete before and after microwave irradiation, are analyzed. Scanning electron microscopy (SEM) is employed to observe the surface morphology and microstructure of the concrete before and after irradiation to investigate internal micro-damage. The results indicate that the iron-containing oxides in iron ore tailings possess superior wave-absorbing capabilities. The temperatures of both iron ore tailings and limestone increase with irradiation time, while the heating rate decreases; however, the temperature rise of iron ore tailings is larger than that of limestone. At the same irradiation time, the temperature of iron ore tailing concrete increases with increasing power. The wave-absorbing efficiency is highest at 6 kW. The temperature difference of the specimens before and after irradiation increases linearly at first and then slows down with increasing irradiation time. The UPV of the concrete decreases with increasing irradiation time and power. At the same power, the UPV attenuation rate increases rapidly initially and then slows down with increasing time. Under 0、2、4、6，8 kW power and 0~5 min irradiation, the UPV attenuation rate can reach up to 35.29%. After microwave irradiation, 1~3 μm thermal stress cracks are generated in the interfacial transition zone between iron ore tailings and mortar and propagate along the interface.

Keywords: microwave irradiation; iron tailing; ultrasonic wave sound speed; cement concrete