Influence of aggregate size on the compressive size effect according to different concrete types

• This study provides understanding of the compressive size effect according to concrete type.
• We also examine the influence of aggregate size on the size effect.
• We ascertain the reliability of the existing equations for different concretes.
• We find that the influence of aggregate size on size effect is negligible for lightweight concrete.
• It is observed that the size effect become stronger with the decrease of concrete unit weight.

The present tests prepared 9 ready-mixed concrete batches to examine the influences of the concrete type and the maximum aggregate size (da) on the size effect in compression. For each concrete mixing, the aspect ratios of specimens with circular or square sections were 1.0 and 2.0, while the lateral dimensions of specimens varied from 50 mm to 400 mm. A comprehensive database including the 1492 normal-weight concrete (NWC) and 363 lightweight concrete (LWC) specimens was also established in order to trace the size-effect trend in LWC through the comparisons with the modern prediction models proposed by Bažant, Neville, Kim and Eo, and Sim et al. The present study clearly showed that the size effect and the slope of the size effect became stronger with the decrease of the unit weight of concrete. The influence of da on the size effect observed in the current NWC specimens was smaller than the predictions obtained from the models of Bažant and Kim and Eo; while it was found to be negligible for LWC. Further, the refined model of Sim et al. confirms that the gain of the compressive strength of concrete due to the increase of da is insignificant, especially for LWC.