Abstract
Four common specimen types were tested in uniaxial compression under the influence of two distinct loading surfaces to analyze concrete’s shape effect, strength performance, and crack propagation. Inferential data analysis using analysis of variance (ANOVA) was applied, proving a main effect for specimen shape. Pairwise comparison revealed a geometric effect between all but two sample types. Decreased surface friction showed a significant strength reduction, ranging between 9.5 and 31.5%. The influence of surface friction, combined with geometric properties, was assessed, with one shape to be mutually different from all other shapes. The development of rupture was captured by high-speed video technology with 2000 frames per second. Clear differences in crack initiation and propagation were observed for different surface treatments, regardless of specimen type. While cracks under conventional confinement formed inclined failure facets (45 to 60 degrees), cracks were free to develop vertically under reduced friction, forming slender concrete shards that failed in buckling.
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