Divergent deterioration pathways of normal-and high-strength concrete under sequential multi-factor deterioration of freeze-thaw, chloride, and carbonation attacks

초록

This study aims to clarify the sequential multi-factor deterioration behavior of concrete under multiple environmental stressors by investigating the synergistic effects of freeze-thaw cycles, chloride ingress, and carbonation. Normal-strength concrete (NSC) and high-strength concrete (HSC) specimens were subjected to freeze-thaw cycles first, followed by alternating chloride ingress and accelerated carbonation under controlled conditions. Deterioration was evaluated through mechanical tests and, including thermogravimetric analysis (TG), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). The results show that HSC exhibits greater resistance to coupled degradation due to its denser microstructure, which limits crack propagation and ion transport. In contrast, NSC experienced more severe deterioration, including pore coarsening, accelerated chloride penetration, and enhanced carbonation triggered by freezethaw-induced microcracking. TG and XRD confirmed significant phase transformation, with increased consumption of Ca(OH)2 and formation of CaCO3 under combined exposure. Mechanical performance decreased with increasing exposure severity, and NSC showed up to a 43.5% reduction in compressive strength. These findings emphasize the critical role of initial matrix density in resisting multi-factor deterioration and provide guidance for designing durable concrete in cold and marine environments.

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