Moving from laboratory to real‐world exposure – Observations from ultrasonic testing of concrete exposed to simulated rain

Abstract

The intended use of low‐carbon cements, for which experience on long‐term behavior under real exposure conditions is lacking, necessitate advanced material testing and monitoring methods. While material performance tests are carried out in controlled laboratory experiments, monitoring of real structures is subject to inconsistent boundary conditions. Transferability from the laboratory to practical application hence requires testing procedures to move towards greater realism. Nondestructive ultrasound‐based Coda Wave Interferometry (CWI) is currently investigated for continuous monitoring of reinforced concrete structures. The separation of material changes and their causes remain the main challenge in CWI application. Previous research has studied the effect of homogeneous ambient temperature and humidity changes, which is diverging from real exposure. Here, two concrete specimens equipped with embedded ultrasonic transducers were exposed to repeated simulated rain events of 1 min every 8 hours while ultrasonic signals were collected continuously and evaluated using CWI. The maximized correlation coefficient was found to be more sensitive to general moisture changes, whereas an immediate drop in the relative velocity change and subsequent recovery was observed following rain events.