Influence of Stress on High Frequency Wave Propagation in Heterogeneous Cementitious Composite Medium

Stress-state in material system is the primary indicator for determining the safety of structures. The main challenge is posed when the structure is subjected to low level of stress (about 30% of strength) and the stress variation does not cause any visible intimation (like crack formation) from the member. The present study is aimed to investigate the acousto-elastic behavior of concrete structural member subjected to uniaxial compressive load. Here, step-wise referencing based Coda Wave Interferometry (CWI) is performed for the entire time signal in frequency domain (using Magnitude Squared Coherence) and time domain (using Doublet and the Taylor series method). Stepwise-Taylor based CWI is found to be highly sensitive for bringing out the nonlinear impact on the acousto-elastic behavior under different levels of compressive stress in the large concrete member. The Taylor series-CWI can effectively monitor the stress variations in three directions, i.e. along the loading direction (one path), orthogonal to loading direction (two paths). The present study focuses on, i) the application of efficient CWI methods to evaluation of stress in laboratory scaled realistic concrete member, and ii) to explain the nonlinear characteristics within the acousto-elastic regime from the aspect of stress based microstructural phenomenon.