Dynamic increase factor(DIF) of concrete with SHPB tests: Review and systematic analysis

This study presents a comprehensive review and systematic analysis of 116 publications focusing on the dynamic increase factor (DIF) in concrete, a critical parameter for evaluating strain-rate effects on strength development. Over 1500 DIF data points from 49 models were examined to assess the impact of various factors on DIF. The results indicate that static strength has the most significant effect on DIF, followed by specimen diameter, silica fume content, fiber content, GGBS content, and fly ash content. The study establishes two mathematical models to demonstrate the relationship between specimen size or static strength and dynamic strength of concrete. More-over, the influence of fibers and cement type on DIF is investigated, revealing that steel fibers decrease DIF with increasing content, while organic fibers exhibit higher DIFs. Geopolymer concrete with GGBS and fly ash demonstrates higher DIF and strain rate sensitivity, whereas fly ash reduces DIF at lower strain rates by mitigating brittleness.