Concrete strength evaluation in an early-age curing process using SVM with ultrasonic harmonic waves

Previous studies have not advanced a method for measuring the strength of concrete at an early age. In this study, an embedded piezoelectric sensor module has been developed for early-age strength testing, along with a new algorithm for estimating the strength of concrete using the harmonic response signals obtained from the embedded piezoelectric sensor. The actuators can be made from piezoelectric materials to launch ultrasonic waves, which propagate in the concrete structures. In addition, the piezoelectric materials can be used as sensors to detect the ultrasonic waves. The results of a study carried out to investigate the relationship between the signal change and concrete strength are presented in this paper. The experimental results show that the harmonic response amplitude decreases as the strength of the concrete increases. The strength of the concrete increased rapidly during the early-age stage. At the same time, the harmonic response amplitudes from the piezoelectric sensors dropped rapidly during this stage and continued to drop slowly as the curing process continued. In addition, a support vector machine (SVM) was used to classify the concrete strength and the results show good accuracy. The overall results show that the proposed method can be reliably used to estimate changes in concrete material strength during the early stages of the curing process. In addition, this method enhances the process of structural health monitoring using a piezoelectric sensor with a rapid response speed, high resolution and good reliability.