Dynamic Properties of Foam Concrete Subjected to Different Confining Pressures, Curing Ages, and Numbers of Dry–Wet Cycles

A thorough investigation into the dynamic characteristics of foam concrete (FC) is essential to fully exploit its engineering application potential. The dynamic behaviors of FC were evaluated through staged cyclic loading tests, emphasizing the effects of confining pressure, curing age, and dry–wet cycles on the backbone curves, dynamic elastic modulus (Ed), and damping ratio (D). The findings reveal that the backbone curves of FC demonstrate typical elastoplastic deformation. With increasing dynamic axial strain, Ed initially increases and then decreases gradually, while D initially decreases and subsequently increases gradually. The dynamic deformation characteristics of FC depend on confining pressure and curing age. Increased confining pressure and longer curing age substantially enhance FC’s resistance to dynamic loading, resulting in higher dynamic strength and Ed. During dry–wet cycles, the temperature effect and capillary pressure combine to induce vulnerable pore fracture and microcrack development in FC, leading to a degradation of dynamic strength and Ed. The cumulative damage to the maximum dynamic elastic modulus (Edmax) increases approximately linearly with the number of dry–wet cycles, but it is less affected by confining pressure. After 10 dry–wet cycles, the cumulative damage of Edmax is approximately 11.3%, highlighting the exceptional durability and dynamic performance of FC. Beyond the transitional strain, D gradually decreases with higher confining pressure and curing age, while it increases with additional dry–wet cycles. This research contributes to the evaluation of FC’s application in civil engineering, such as vibration isolation structures and road subbase materials.