Slow dynamics in concrete: Effects of temperature, strength variation, and microcracking damage

Abstract

In this study, we investigated the slow dynamic behavior of concrete with varying compressive strengths ($f'_c = 32\sim56$ MPa) and alkali-silica reaction (ASR) damage. Concrete prisms were conditioned by compressive loading and recovery was monitored by coda wave interferometry (CWI). A self-referencing temperature correction technique was used to minimize the effect of ambient temperature changes, demonstrating the importance of careful temperature control and correction. For intact specimens, both the recovery rate, $m_v$, and velocity drop magnitude, $|c|$, generally increased with compressive strength. Recovery times were calculated from the fit parameters, and higher strength specimens were found to recover faster (9.9 h for $f'_c = 32$ MPa, 6.6 h for $f'_c = 56$ MPa). When the same stress was applied, ASR-damaged specimens had increased softening and faster recovery rates, but longer recovery times (up to 458 h). These findings demonstrate the potential of slow dynamics in concrete characterization, through its ability to evaluate the strength of intact samples and its sensitivity to microcracking in damaged samples.