Investigation on the evolution of concrete pore structure under freeze-thaw and fatigue loads

• Published in: Journal of Building Engineering Vol. 97; p. 110914
• Main Authors: Gan, Lei, Zou, Zongyi, Zhang, Zongliang, Zhang, Hongwei, Gu, Hao, Jin, Hongjie
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-11-2024
• Subjects: Concrete; Fatigue load; Fractal dimension; Freeze-thaw cycle; Pore structure; Freeze-thaw cycle; Concrete; Fatigue load; Fractal dimension; Pore structure
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2024.110914

Hydraulic concrete structures in seasonal frozen regions serve under freeze-thaw cycles and cyclic loading conditions which cause notable alterations in the concrete pore structure and a significant reduction in the mechanical properties and durability of concrete. To understand the macroscopic and mesoscopic damage processes and mechanism of concrete subjected to freeze-thaw cycles and cyclic loading lead, the compressive experiment and computed tomography test of concrete after freeze-thaw and fatigue loading tests were conducted. And the influences of freeze-thaw cycle damage and cyclic loading damage on the pore structure of concrete were analyzed. The relationships between concrete pore fractal dimension, compressive strength, and elastic modulus were revealed. The concrete average pore size can be regarded to grows linearly under freeze-thaw and cyclic loading. The porosity, pore volume, and pore surface area increase with the increase in freeze-thaw cycles, and their relationship can be represented by a quadratic function. However, they first decrease and then increase with the increase of loading cycles after a specific freeze-thaw cycles number. Under the combined action of freeze-thaw cycles and cyclic loading, the non-uniformity degree of concrete pore distribution decreases, and the overall structure is more regular. The distribution of single pore morphology tends to be spherical and banded, respectively. The cyclic loading promotes the extension of the internal pores and cracks of freeze-thaw-damaged concrete which aggravates damage of concrete. Under freeze-thaw cyclic loading, the concrete compressive strength and elasticity modulus is linearly and positively correlated with fractal dimension. With the increase of loading cycles number after freezing and thawing, the fractal dimension and compressive strength decrease, and the elasticity modulus has a larger dispersion. The relationship model between concrete compressive strength and fractal dimension can well describe the macroscopic and mesoscopic evolution of concrete under freeze-thaw and cyclic loading. The results can provide a scientific basis for improving the design and maintenance of concrete and benefit extending the long-term service life of hydraulic concrete structures in cold climates.
•Design of the freeze-thaw cycles and fatigue loading experimental schemes on concrete.•Investigation of pore structure properties of concrete under different freeze-thaw and fatigue loads.•Concrete average pore size grows gradually under freeze-thaw and cyclic loading.•Fractal dimension of concrete linearly and positively correlated with compressive strength.