Multi-scale study on the durability degradation mechanism of aeolian sand concrete under freeze

Multi-scale study on the durability degradation mechanism of aeolian sand concrete under freeze–thaw conditions

Li, Yugen / Zhang, Huimei / Chen, Shaojie / Wang, Hairen / Liu, Guangxiu

Highlights • The F-T fatigue life of concrete increases with increasing aeolian sand content. • Multi-scale influence of aeolian sand on concrete's frost resistance is revealed. • F-T damage of ASC is mainly caused by physical effect and weakly by chemical effect. • Aeolian sand changes concrete pore structure thereby affects its frost resistance.

Abstract A comprehensive understanding of the freeze–thaw (F-T) degradation of aeolian sand concrete (ASC) and associated damage mechanism is important for its popularization and application. In this study, river sand was partially replaced by aeolian sand from the Mu Us Desert in Northwest China to produce ASC. Scanning electron microscopy, X-ray single crystal diffraction, nuclear magnetic resonance, and damage mechanics theory were applied to determine the damage mechanism caused by F-T cycling, and the multi-scale influence of aeolian sand on the frost resistance of concrete was constrained based on rapid F-T cycle tests. The results show that the F-T fatigue life of concrete increases with increasing aeolian sand content. The optimal frost resistance is achieved with 100% aeolian sand replacement despite its low strength, which is 19.49% higher than that of ordinary concrete. A quadratic parabolic relationship exists between the loss rates of mass, dynamic elastic modulus, compressive strength, and number of F-T cycles. The F-T damage of ASC is mainly dominated by physical effects and weakly by chemical effects. Concrete subjected to F-T cycling undergoes damage that progresses from the outside surface inward. The main drivers of the macroscopic property degradation of concrete are (1) scaling and debonding of the aggregate slurry in the interfacial transition zone and (2) cracking and expansion of the mortar matrix. The influence mechanism of aeolian sand on the frost resistance of concrete involves a change of porosity and concrete pore structure, which alters the moisture transmission path and thus affects the pore saturation and saturation rate.