Investigation of the compressive behaviour of restrained concrete with DEF and ASR-DEF deteriorations

Chemical pathologies such as the alkali-silica reaction (ASR) and delayed ettringite formation (DEF) degrade the mechanical properties of concrete. Although most studies have focused on the mechanical property reduction of plain concrete affected by ASR and DEF, it is crucial to investigate this degradation under restrained conditions, because concrete in structural members is subjected to both external and internal restraints owing to supports, prestressing forces, and internal reinforcement. This study examined the effect of restraints on the compressive strength and dynamic moduli of concrete affected by combined ASR-DEF and DEF alone. Cylindrical and cubic specimens were cast to measure these properties under externally and internally restrained conditions at three expansion levels. Two restraint levels were applied to counteract the expansion of both deterioration types under each restraint condition. The reductions in the compressive strength and dynamic moduli of the externally restrained specimens were lower than those of the free specimens without restraint in both deterioration scenarios. The compressive strength of the internally restrained specimens was influenced by the triaxial confinement of the concrete core, which resulted from the chemical prestressing of the reinforcement during deterioration. These findings indicate the critical importance of accounting for restraint effects when assessing the structural performance of reinforced concrete systems. Evaluations relying solely on plain concrete core samples or similar indicators may fail to accurately represent the performance of structures under restraints in actual configurations.