Cemented paste backfill (CPB) is broadly used for underground backfilling, improving the mechanical performance through the modification of its composition and, therefore, its microstructure and characteristics. In order to assess the applicability of ultrasonic waves to better comprehend relations among composition-microstructure-characteristics; an experimental program was realized using the magnitude and frequency spectrum of ultrasonic P-wave which is considered as an effective system for characterizing the hardening processes of cementitious materials. In this study, different binder contents (3, 5 and 7 wt%) and curing temperatures (20 and 35 °C) were tested for investigating CPB’s hardening processes. Silica fume (0, 5 and 20 wt% of binder) was used as an additive in replace of binder to determine its effect on behavior of ultrasonic waves. Component (TG and DTG) and microanalysis (SEM) were adopted to improve the understanding of ultrasonic behavior. Results show that there is a positive relationship between the strength and magnitude of ultrasonic P-wave in CPB, except for the sample with 3 wt% binder. The magnitude and frequency spectrum of ultrasonic P-wave is more sensitive than P-wave velocity to reflect the variation in the backfill strength. Higher binder content can densify the microstructure of CPB with longer curing time and reduce the energy attenuation of ultrasonic P-wave, resulting higher magnitude obtained. The addition of silica fume makes CPB having a finer pore structure enhanced, thereby improving in the strength, P-wave velocity and magnitude. The energy attenuation of ultrasonic P-wave can be notably weakened at a curing temperature of 35 °C due to a dense network formed by both hydration products and tailings. The magnitude and frequency spectrum of ultrasonic P-wave can be capable of reflecting and characterizing the pore structure, hydration processes and water content in CPB comprehensively. Consequently, the proposed technique can be well used to illustrate the hardening processes of CPB and hence improve the understanding of its early-age behavior.

水泥浆回填（CPB）广泛用于地下回填，通过改变其成分以及微观结构和特性来改善机械性能。为了评估超声波的适用性，以更好地理解成分-微结构-特征之间的关系；利用超声波P波的幅度和频谱实现了一个实验程序，该程序被认为是表征胶凝材料硬化过程的有效系统。在这项研究中，测试了不同的粘合剂含量（3、5和7 wt％）和固化温度（20和35°C）以研究CPB的硬化过程。硅粉（0、5和20 wt％的粘结剂）用作添加剂来代替粘结剂，以确定其对超声波行为的影响。成分（TG和DTG）和微量分析（SEM）被用来增进对超声行为的理解。结果表明，除了粘合剂含量为3 wt％的样品外，CPB中超声波P波的强度与强度之间存在正相关关系。超声波P波的幅度和频谱比P波速度更敏感，以反映回填强度的变化。较高的粘合剂含量可以使CPB的微观结构致密，固化时间更长，并减少超声P波的能量衰减，从而获得更高的强度。硅粉的添加使具有更细孔结构的CPB得到增强，从而提高了强度，P波速度和幅度。由于水合产物和尾矿形成的致密网络，在35°C的固化温度下，超声波P波的能量衰减会明显减弱。超声波P波的幅值和频谱能够全面反映和表征CPB中的孔隙结构，水化过程和含水量。因此，所提出的技术可以很好地用于说明CPB的硬化过程，从而改善对CPB早期行为的理解。