Effect of compaction mechanisms and segregation behaviour on the distribution of internal-curing expanded clay aggregates in roller-compacted concrete mixtures

Despite the potential of expanded clay aggregates (ECAs) as internal curing agents in roller-compacted concrete (RCC) pavements, the influence of compaction on their integrity and spatial distribution remains insufficiently understood. Laboratory and field compaction may alter ECA morphology, cause particle breakage or segregation, and affect internal-curing effectiveness. This study investigates how modified Proctor, vibratory hammer, and vibratory table compaction affect ECA degradation and spatial distribution in RCC mixtures. Aggregate breakage was quantified using a breakage index. The Aggregate Image Measurement System (AIMS) assessed aggregate characteristics, while an image-based segregation index, spacing factor, and protected ratio characterised ECA distribution and spatial effectiveness. The results demonstrate that compaction method influences aggregate stability and distribution within the RCC matrix. Vibratory methods produced more uniform ECA distributions and favourable spatial characteristics for internal curing, whereas impact-based compaction caused greater aggregate degradation and localised variations. Among the methods investigated, vibratory table compaction provided the best balance between aggregate integrity, distribution uniformity, and internal-curing effectiveness. These findings highlight the importance of considering compaction-induced changes when selecting laboratory procedures and field construction practices for ECA-incorporated RCC pavements. The findings provide guidance for selecting compaction protocols that preserve ECA integrity and ensure consistent internal-curing performance in pavement applications.