Concrete cores extracted from mass concrete dams are typically larger in diameter relative to the nominal maximum aggregate size than cores taken from conventional structures. As a result, individual coarse aggregates within a core specimen may span a substantial fraction of the cross-section. This geometric mismatch complicates mechanical characterisation and the interpretation of fracture behaviour under compressive loading, both of which are governed by the internal aggregate structure. Acoustic emission (AE) monitoring offers a non-destructive method to track damage evolution in real time, as the AE energy released during loading reflects the progressive initiation and coalescence of cracks. Fitting a logistic curve to the cumulative AE energy trend allows the loading history to be decomposed into distinct crack-progression stages. Where aggregate gradation is broad and heterogeneous, a model accommodating multiple successive stages may be required, and the Akaike Information Criterion (AIC) provides a quantitative basis for selecting the appropriate model complexity. X-ray computed tomography independently enables the internal aggregate structure to be visualised and quantified in terms of geometric indices such as size, area, and shape, without mechanical intervention. Comparing these geometric indices against the fitted logistic parameters then offers a means of understanding how aggregate geometry affects crack initiation and propagation.
This study applied both two-stage and three-stage logistic models to the cumulative AE energy curves of concrete cores taken from a concrete dam, selected the better-fitting model for each specimen using the AIC, and examined correlations between X-ray CT-derived coarse aggregate geometric indices and the resulting logistic parameters. Aggregate size indices were significantly and positively correlated with the relative contribution of the final crack-progression stage, while specimens containing vertically elongated aggregates tended to show an earlier onset of intermediate cracking, consistent with strain concentration along the loading direction at aggregate–mortar interfaces.
