Investigation on size effects of ultra-high-performance concrete: experimental and numerical study

Test specimens with smaller sizes seem to be preferable because using standard specimen sizes for ultra-high-performance concrete (UHPC) can lead to issues owing to the current testing equipment's capacity limitations. Therefore, the size effect investigation of the UHPC specimens is necessary. In this paper, the UHPC mix was used to explore the size effect on the compression and flexural response of the cylinder and beam specimens, respectively. The UHPC mix was cast into various-sized cylinders and beams with diameters ranging from 50 to 150 mm and heights/widths from 50 to 150 mm, respectively. A nonlinear 3D finite element (FE) model has been created in ABAQUS software for all UHPC specimens. Additionally, validation was done using the experimental findings of this study. The findings clearly revealed that the compressive and flexural strength decreases with increasing the size of the specimen. The larger specimens revealed a slight reduction in compressive strength between 1.4% and 9.5%, while a considerable reduction was recorded in flexural strength, where the larger specimens showed reduction ratios between 19.1% and 35.6%. Furthermore, the experimental and FE findings were in satisfactory agreement and exhibited virtually identical overall trends.