Wave propagation based monitoring of concrete curing using piezoelectric materials: Review and path forward

The in-situ strength of concrete is often evaluated by destructive compressive strength tests conducted on cylinders or cube specimens cast alongside the main structure. Various non-destructive testing (NDT) techniques are also available in the industry. In the past decade, the use of piezoelectric based wave propagation (WP) techniques for monitoring the curing process of concrete has attracted considerable interest from researchers in the civil engineering discipline and hence there is a need to summarize the state of knowledge in order for future research efforts to be focused and relevant. This paper therefore presents a review of recent research and development of the abovementioned research area. Existing NDT techniques and piezoelectric based techniques for the monitoring of concrete curing are initially reviewed. Developments associated with the WP technique employing both embedded and surface bonded piezoelectric transducers are then presented. Finally, successful applications of the WP technique are provided. A wide range of parameters adopted by different researchers as concrete strength indicators are also summarized. Theoretical and numerical models available are reviewed, followed by a summary of practical issues related to the application of this technique. Several studies to date have proven the capability of the WP technique in monitoring the curing process of concrete. More rigorous studies are, however, required before a mature technique is developed that can entice commercial interest. Thus, future areas of investigation are identified in the final section. This article is expected to serve as an introduction for researchers interested in venturing into this area and as a valuable summary to inspire existing researchers for further improving the technique.