Design and application of a piezoelectric stimulation model for the mixture of concrete specimens with varying aggregate sizes

In this study, a piezoelectric excitation system operating at 40 kHz was developed. Using this system, the effects of aggregates with varying particle sizes on the mechanical and physical properties of concrete were comparatively investigated through both destructive and non-destructive testing methods. Four different aggregate sizes (fine, medium, medium-coarse, and coarse) were used, and a total of 16 concrete specimens—four for each aggregate type—were prepared. The water-to-cement ratio was kept constant for all mixtures. During casting, conventional concrete compaction methods such as rodding and tamping were applied. Additionally, piezoelectric transducers operating at a fixed low power and 40 kHz frequency were mounted on different mold surfaces to assess their influence on the internal concrete mixture. After curing, the internal homogeneity of the concrete was evaluated using image processing techniques and Ultrasonic Pulse Velocity (UPV) testing, while the mechanical properties were assessed through compressive strength tests. The dry weights of the specimens were also measured for comparison of physical characteristics. According to the experimental results, the medium aggregate specimen compacted by traditional methods exhibited the highest dry weight (7.125 kg). The specimen with coarse aggregate subjected to 3 minutes of ultrasonic vibration achieved the highest UPV value (4143 m/s). The highest compressive strength (22.73 MPa) was recorded for the untreated specimen with medium aggregate. In conclusion, it was determined that high-frequency, low-power ultrasonic vibrations applied via the developed piezoelectric transducer system contributed to the overall homogeneity of the concrete's internal structure. However, regions located very close to the direction of ultrasonic excitation exhibited a slight loss of homogeneity.