Monitoring Damage Evolution of Concrete Prisms under Cyclic Incremental Loading by Acoustic Emission

This study aims to monitor the damage growth of plain and fly ash concrete prisms with different curing periods under cyclic incremental loading using acoustic emission (AE) parameters. Higher flexural strength was observed for 28 days cured plain and fly ash concrete prisms as compared to 7 days cured. AE results for 7 days cured plain and fly ash concrete prisms have shown that, Kaiser effect exist in first two loading cycles and from third cycle onwards significant AE activity occurs prior to the previous cycle's maximum load. This is an indication of the start of damage almost at the same load in both the concretes. For 28 days cured fly ash concrete, AE activity during cyclic loading is observed only at 20 kN load as compared to plain concrete in which it occurs at 12 kN load. This shows that cyclic load flexural resistance of fly ash concrete for damage accumulation is higher than that of plain concrete. Load ratio of both types of concrete has been determined during each cycle. Decrease in trend of load ratio with loading cycle is an indication of damage growth. Higher load ratio in 28 days cured fly ash concrete shows addition of fly ash with extended curing which resists damage accumulation. An attempt has been made to classify damage levels during each cycles using NDIS 2421 standard and compared the types of damage in both plain and fly ash concretes.