Improving radon mitigation in uranium mill tailings red clay cover layer using alkali-activated biochar combined with...

To address the poor stability of radon mitigation performance of red clay cover layers on uranium mill tailings (UMTs), alkali-activated biochar was prepared from garden waste using a high-temperature oxygen-limited method. The biochar was then combined with enzyme-induced carbonate precipitation (EICP) to improve the radon mitigation performance of the UMTs red clay cover layer. The specimens were tested for unconfined compressive strength, ultrasonic wave velocity, calcium carbonate content, wetting disintegration, water absorption, and radon diffusion coefficient. The results were compared with those of a sand-mixed EICP treated group and an untreated soil group. The optimal mixing ratio was determined using a normalization method. The results show that the optimal biochar content is 3%. At this mixing ratio, the unconfined compressive strength (UCS) and ultrasonic wave velocity (UWV) of the specimens are 1594 kPa and 1.48 km/s, respectively. Compared with the untreated soil, the radon mitigation performance is improved by 3.5 times, and the disintegration resistance rate is increased by 5.4 times.