Assessing the effect of different compaction mechanisms on the internal structure of roller compacted concrete

•Compaction mechanisms dominantly affect the internal structural arrangement of RCC.•VH compacted specimen exhibited a denser and uniform aggregate skeleton.•Except for VH, all other compaction methods manifested a localized segregation.•In spite of segregation, MP could mimic the field density and compressive strength.•Two segregation indices were proposed for quality control. Compaction plays a pivotal role in the formation of the aggregate skeleton of concrete mixtures, especially for stiff mixes such as Roller Compacted Concrete (RCC). RCC is compacted in the field with combinations of different energies (kneading/shear, impact, static & vibratory pressure), whereas various compactors are used, viz. modified Proctor (MP), vibratory hammer (VH), vibratory table (VT), and gyratory compactor (GY) in the laboratory to mimic the field compaction. Since the compaction mechanism is different in these compactors compared to field rollers, the behaviour of RCC is also distinct and warrants a fundamental study. In this study, the dominating parameters affecting the mesostructural arrangement of aggregates within the concrete skeleton when compacted with different mechanisms are comprehensively studied and compared with the field compacted specimens using several image processing techniques. The mesostructural parameters considered are interparticle spacing & distribution, aggregates segregation, orientation, morphology & breakage post-compaction, and crack length. The results indicate a higher possibility of getting better aggregate distribution and strength while a lower segregation potential when compacted with VH, followed by MP. However, the use of MP could alter the aggregates’ morphological characteristics due to the breakage of particles during the compaction process. On the other hand, VT and GY could exhibit similar interparticle distances to the field specimens but could not demonstrate similar performance in terms of strength and durability. The dominating parameters affecting aggregates’ spatial distribution are found to be aggregate-to-mortar ratio, interparticle distance, and the mechanism associated with each compaction technique.