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Concrete structures, such as armories, military bunkers, and petrochemical facilities, are susceptible to explosive loads during service. The superior mechanical properties of ultrahigh-performance concrete enable structures built with it to endure explosive loads. This study aims to characterize the behavior of ultrahigh-performance concrete at different ages, namely, 1, 3, 7, 14, and 28 days, at different strain rates. The compressive stress–strain response of ultrahigh-performance concrete is studied at static and high-strain-rate loading. The high-strain-rate response is characterized using a split-Hopkinson pressure bar of 100-mm diameter. The influence of age on strength, dynamic increase factor strain rate, elastic modulus, peak strain, and energy absorption are discussed. When tested at the same striker velocity, the dynamic increase factor and strain rate of ultrahigh-performance concrete of similar specimen size decrease with age. The elastic modulus and energy absorption increase from 1 to 14 days. There is no significant change in these quantities between 14 and 28 days. The strength, elastic modulus, and energy absorption increase with increasing strain rate for all ages. Experimental data are validated using the Tedesco model and current standards for stress, strain, and elastic modulus. The model from the standards overestimates strength, whereas the Tedesco model predicts strength conservatively. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is widely used in reinforced concrete buildings, owing to its ability to consolidate by weight and its lack of requirement for external vibration. Reinforced concrete buildings can be subjected to high strain rate loading during the early days of construction or in their service life. Thus, it is critical to understand the behaviour of concrete under high strain rate loadings at different ages. Minimal studies have previously focused on the early-age behaviour of concrete under high strain rates. This study tries to fill this gap. It focuses on the behaviour of M40 grade SCC under three levels of strain rate loading at ages of 1, 3, 7, 14 and 28 d. The split-Hopkinson pressure bar (SHPB) was used to test 45 SCC specimens of diameter 100 m and thickness 50 mm at high strain rates, ranging from 30 s−1 to 110 s−1, and the determined compressive strength, peak strain and elastic modulus results are compared with quasistatic test results of SCC specimens. The dynamic increase factor (DIF) determined in the SHPB experiment is compared with the CEB-fib code model. The results indicate that the DIF reduces as the concrete's strength and age increase. [ABSTRACT FROM AUTHOR]