Ultrasonic Coda Wave Monitoring of Alkali-Silica Reactivity in Concrete Laboratory Prisms

Alkali-silica reaction (ASR) is a deleterious reaction in concrete that leads to the expansion and cracking of concrete. Laboratory approaches to monitor concrete for ASR activity are often lengthy and depend on an operator for regular measurements. The aim of this research is to develop an automated and reliable monitoring approach based on ultrasonic coda (or diffuse) wavefields, which are highly sensitive to minute and slowly occurring changes in a material—ideal for ASR. In this paper, the proposed approachis introduced along with an experimental study that compares ultrasonic coda wave monitoring data with traditional expansion measurements following ASTM C1293. A simple, fast, and robust algorithm to track a selected coda wave feature is proposed and evaluated and was applied to the recorded data. The monitored concrete prisms were designed to have three different levels of ASR activity by varying the lithium admixture dosage. The proposed approach was found to be promising. The process is automated and the monitoring of the specimens using coda wavefields was able to clearly differentiate the mixtures with varying ASR expansions.