Articles

Durability of the Initially Cracked Ultra High Performance Concrete Subjected to Coupled Chloride and Freeze-Thaw Attacks

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Abstract

The durability of ultra high performance concrete (UHPC) with initial cracking subjected to the coupled chloride and freeze-thaw attacks was investigated. The initial cracking was introduced under the controlled condition in the laboratory by applying direct tension to the UHPC specimens and terminating at the strain of approximately 0.15%. The initially cracked UHPC specimens were then submerged in the 4% concentration NaCl solution and subjected to 100, 200, and 300 freeze-thaw (F-T) cycles. The results showed that the tensile properties (tensile strength, initial cracking strength, strain capacity, energy absorption capacity, and elastic modulus) and compressive strength of the initially cracked UHPCs were generally improved up to 200 F-T cycles compared with those of the control and then decreased with the further increase of the F-T cycles to 300. The UHPC specimens with initial damage exhibited excellent chloride penetration resistance at the end of the tests as indicated by the low chloride ion concentration (less than 0.5% overall) and very limited penetration depth (not more than 10 mm) after undergoing the coupled chloride and F-T attacks. The improvement in the mechanical properties up to 200 F-T cycles can be attributed to the self-healing effect due to the large amount of unhydrated cement. This is supported by the higher degree of hydration as quantified by the thermogravimetric analysis. However, the damaging effect due to the chloride penetration and F-T attack exceeded the self-healing effect at the 300 F-T cycles.

Keywords: chloride penetration, freeze-thaw attack, initially damaged UHPC

How to Cite:

Ai, X., Pan, M., Zhong, R. & Wang, J., (2023) “Durability of the Initially Cracked Ultra High Performance Concrete Subjected to Coupled Chloride and Freeze-Thaw Attacks”, International Interactive Symposium on Ultra-High Performance Concrete 3(1): 80. doi: https://doi.org/10.21838/uhpc.16693

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