Durability deterioration mechanism of aeolian sand concrete under carbonization & freeze-thaw conditions

Aeolian sand affects the durability of concrete, and it is of great significance to reveal the durability deterioration mechanism of aeolian sand concrete under freeze-thaw (F-T) and carbonization & freeze-thaw (C&F-T) conditions. The deterioration of aeolian sand concrete under F-T and C&F-T conditions was studied according to the fast indoor test and mechanical characteristic test on the basis of evaluating its mechanical properties, the damage model was established, and the deterioration mechanism was revealed combining with the damage mechanics theory and characterization techniques such as scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). The results show that the aeolian sand affects the F-T resistance and C&F-T resistance of concrete. The greater the amount of aeolian sand, the better the durability of concrete, and the carbonation accelerates the F-T damage of concrete. The damage model established is in good agreement with the experimental results, and the fatigue life of aeolian sand concrete under C&F-T conditions is 4.76 % shorter than that of under F-T conditions. The mechanism of aeolian sand improving concrete durability is that it changes the internal porosity and pore structure of concrete. The fundamental reason for the F-T damage of concrete accelerated by carbonation is that the expansion products formed by carbonation cause the concrete surface to crumble and crack, which provides a favorable channel for external water intrusion.