Investigation of Fracturing in Concrete Made of Mine Tailing-Based Lightweight Aggregates by Ultrasonic Imaging and Digital Image Correlation

Mine tailings (MTs) pose significant environmental challenges, including the occupation of large areas of land and toxic leaching of harmful substances such as heavy metals. The development of sustainable lightweight concrete (LWC), incorporating lightweight aggregates (LWAs) derived from MTs, offers a potential solution to mitigate these issues while reducing the demand for natural resources. Understanding the fracture behavior of LWCs is crucial for their application as construction materials. This study aims to provide insight into the mechanical properties of LWC by investigating their fracture behavior through three-point bending tests (3PBT) on beam samples. By utilizing ultrasonic imaging, different fracturing processes (aseismic and seismic) associated with the initiation and growth of fractures are identified. An active ultrasonic monitoring method was employed during the 3PBT of LWC by continuously monitoring the actively propagating waves at different imaging areas at the side of the specimen (near and far from the existing notch). Simultaneously, a two-dimensional digital image correlation (2-D DIC) technique was used in sync with the ultrasonic monitoring technique to measure the full-field strains on the surface of the beam specimens. Waveform attributes such as amplitude and energy of the transmitted waves were monitored at different stages of the test, and the findings were correlated with the strain-based observations by the DIC technique. A relative correlation was observed between the accumulated strain obtained by 2-D DIC and the ultrasonic signal features