Acoustic Emission-Guided Damage Delineation and Machine Learning Prediction of Flexural Strength in Lightweight Mortar under Thermal Exposure
摘要
Lightweight expanded vermiculite (EV) mortars based on calcium sulfoaluminate (CSA) cement are promising for high temperature applications. However, predicting their residual strength after moderate thermal exposure (70–100℃) remains challenging. This study employs advanced acoustic emission (AE) monitoring and machine learning (ML) to address this. The key contributions are twofold: First, a novel Radial Basis Function (RBF) kernel-based approach has been introduced to dynamically classify failure modes in RA-AF analysis, overcoming the limitations of fixed threshold approaches. Second, a newly developed grouped Gaussian noise (GGN) technique has been used to augment the dataset, which has improved the performance of the LightGBM (LGBM) regression model. Experimental results indicate that while EV content reduces flexural strength, heating at 100℃ restores it by up to 48%, likely due to the formation of crack-filling hydration products. The RBF-refined AE analysis reveals a distinct transition from tensile to shear-dominated failure with accumulating damage. The optimized LGBM model, trained on GGN-augmented data, achieved high prediction accuracy (R2 = 0.99, MAE = 0.18, MSE = 0.06), outperforming other mainstream models. This work proposes a combined diagnostic-predictive framework for assessing lightweight EV mortars under moderate thermal stress.