Quantifying the self-healing phenomenon in cement-based materials: Insights from ultrasound tests and optical microscopy

The self-healing phenomenon is gaining significant attention in the scientific community, both for its potential to reduce high maintenance costs over a structure's lifespan and to gradually decrease the resources required for concrete production. The performance evaluation of various agents influencing the self-healing behavior of cementitious matrices can be conducted through direct or indirect methods. This study assessed three-day cracked concretes containing silica fume, crystalline admixture, or superabsorbent polymer using optical microscopy and ultrasound tests. Image analysis was performed at magnifications of 80x and 160x, processed and quantified by three distinct methodologies. In determining Ultrasonic Pulse Velocity (UPV), the variables included reading position, transducer frequency, and moisture content. Key parameters identified in the image analysis were lighting conditions, sample saturation, magnification, and the automation of cracked area quantification. The 54 kHz exponential transducers statistically distinguished themselves from the other frequencies analyzed, as did the influence of moisture on UPV. • An automated image processing method to measure cracked area in self-healing samples. • The Influence of transducer geometry and frequency on UPV measurements in uncracked and cracked concrete. • Moisture-dependent response in UPV readings of cracked and uncracked concrete samples.