Open Access
ARTICLE
Investigation of Early-Age Freeze-Thaw-Induced Damage Evolution in UHPC and the Structural Strengthening Efficacy of CFRP Systems
Yongbing Sun1, Dewen Liu1,2,*, Qian Wang1,*, Yuexia Yang3, Canhuan Pan3
1 College of Civil Engineering, Southwest Forestry University, Kunming, China
2 International College, Krirk University, Bangkok, Thailand
3 Yunnan Chutian Engineering Inspection Co., Ltd., Kunming, China
* Corresponding Author: Dewen Liu. Email: 
; Qian Wang. Email: 
(This article belongs to the Special Issue: Durability of Cement-based Materials Composites)
Structural Durability & Health Monitoring https://doi.org/10.32604/sdhm.2026.083733
Received 09 April 2026; Accepted 08 June 2026; Published online 29 July 2026
Abstract
During winter construction in cold regions, ultra-high performance concrete (UHPC) is susceptible to early-age freeze-thaw cycles caused by improper curing or sudden cold waves. This study investigates the damage evolution of UHPC under freeze-thaw cycles and the subsequent strengthening effect of carbon fiber reinforced polymer (CFRP). Early-age (7-day cured) UHPC specimens were subjected to coupled freeze-thaw and chloride salt (5% NaCl) exposure. Damage was characterized by ultrasonic wave velocity, compressive strength, and SEM-EDS analysis. Results show that as the number of freeze-thaw cycles increases, mass loss reaches 1.35% at 150 cycles, while wave velocity decreases by 1.14%. Control specimens (without freeze-thaw) exhibited a 24.6% increase in compressive strength with age (corresponding to 150 cycles), whereas the strength of specimens subjected to 150 cycles decreased by 19.9%. After CFRP strengthening, the ratio η (strength of strengthened specimens to that of unstrengthened control specimens of the same age) declines with increasing cycles. The ratio α (strength of strengthened damaged specimens to that of unstrengthened damaged specimens of the same age) reaches 113.1% at 150 cycles, a 3.60% decrease from its initial value, indicating that more severe freeze-thaw damage leads to lower reinforcement efficiency. Microscopic analysis reveals that after 150 cycles, the chloride ion content reaches 0.3 wt%, steel fibers corrode, and the number of pores and microcracks increases. Meanwhile, the Ca/Si atomic ratio decreases due to calcium ion leaching and secondary hydration of silica fume. This study elucidates the evolution mechanism of early-age freeze-thaw damage in UHPC and validates the effectiveness of CFRP strengthening, providing a practical basis for the protection and retrofitting of UHPC structures in cold regions.
Keywords
UHPC; early-age freeze-thaw cycling; carbon fiber–reinforced polymer (CFRP) strengthening; microstructural evolution
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