Acoustic Emission Technique for Monitoring Healing Induced Recovery of Mechanical Properties (HIRMP)

Abstract

AbstractDue to bridging effect of fibers, the crack widths in strain hardening cementitious composites (SHCCs) are restricted to a small value <100 μ. Crack widths of this small size promotes autogenous healing in SHCCs. Ideally, autogenous healing should lead to noticeable reduction of crack width as well as recovery of strength and stiffness. The former leads to recovery of ‘transport properties’ and latter lead to recovery of ‘mechanical properties’ of damaged material. If we want to rely on healing-induced recovery of mechanical properties (HIRMP) are relied upon in built environment, it is important that this should be assess HIRMP in a practical scenario. Most reliable method for assessment of HIRMP is by comparing stress-strain curves of healed specimen with that of is the pristine condition. Load/stress can not be directly measured in practical scenario which render these methods impractical. Healing induced recovery stems from bonding of damages in materials, which if broken produces acoustic emission (AE) signals. Exploiting this fact, in this work potential of AE technique for assessment of HIRMP was studied. In this study, AE testing was performed during loading of ‘pristine’ SHCCs, which were healed and again during re-loading of these self-healed specimen. AE results were changed to power spectral entropy (PSE) to minimize adverse effect of computational parameters. PSE of healed specimen was compared with that of the ‘pristine’ state to assess HIRMP. The major observations of the study are 1. With increasing HIRMP the healing induced ‘bonding’ increases as a result cumulative PSE increases 2. With increasing HIRMP the density of PSE becomes less skewed (to the right) this is because with increasing average stiffness, lower strain is needed to reach ‘hardening’. With these observations novel damage parameters are developed for practical monitoring of HIRMP.KeywordsAutogenous healingAcoustic emissionHealing induced mechanical recoveryStrain hardening cementitious composites