A Study of the deterioration law and mechanism of aeolian-sand powder concrete in the coupling environments of freeze-thaw and carbonization

Abstract

In this study, aeolian-sand powder was used for replacing cement-based gelling material in order to prepare aeolian-sand powder concrete in C25 and C35 strength grades. Through relative dynamic elastic modulus and carbonization depth changes, the deterioration laws of the aeolian-sand powder concrete under the coupling effects of freeze-thaw + carbonization and carbonization + freeze-thaw were studied. Then, field emission scanning electron microscopy, X-ray diffraction, and nuclear magnetic resonance porosity measurement technology were applied to analyze the microstructure, hydration products, and porosity changes. The results show that the Carbonation Mechanism of aeolian sand powder concrete is different from that of ordinary concrete. The carbonation of ordinary concrete results in calcium carbonate, and the carbonation of aeolian sand powder concrete results in calcium sulfate and calcium carbonate; The decrease of relative dynamic elastic modulus of aeolian sand powder concrete under freeze-thaw and carbonation environment is lower than that of ordinary concrete, and the results indicated that the relative dynamic elastic modulus of the aeolian-sand powder concrete under the freeze-thaw + carbonization effects was higher than that under the carbonization + freeze-thaw effects by 1.5 times. Also, the carbonization depth was less than that under the carbonization + freeze-thaw effects by 5.0%. Under the freeze-thaw + carbonization effects, the internal harmless pores of the aeolian-sand powder concrete were higher than carbonation + freeze-thaw by 16.85%, higher than those of the ordinary concrete by 15.35%, the multi-harm pores were observed to be less than that of carbonization + freeze-thaw by 22.5%, which is lower than that of ordinary concrete by 22.25%. At the same time, the irreducible fluid saturation and permeability of aeolian sand powder concrete are 0.34 and 1.5% higher than those of ordinary concrete under the action of carbonization and freeze-thaw, thus the deterioration of aeolian sand powder concrete is significantly lower than that of ordinary concrete, while that of aeolian sand powder concrete under the action of carbonization and freeze-thaw is significantly higher.