Changes in air permeability of restrained expansive concrete under drying condition: contribution of expansive strain

Restraining the expansion of expansive concrete with embedded rebars can exert chemical prestressing, which may affect the durability of concrete structures. This study aims to investigate the durability performance of expansive concrete by understanding the mechanism of air permeability changes while considering the variations in reinforcement arrangements and concrete dimensions. The Torrent's air permeability test was used to non-destructively evaluate the disparity in air permeability changes of expansive and normal concrete during the drying processes from 28 to 182 days. Additionally, expansive strain changes were continuously monitored to investigate chemical prestress. The experimental test results suggest the immense effect of the change in expansive strain on the air permeability of concrete. This study proposes that the change in microstructure owing to the loss of expansive strain may cause an increase in air permeability. The loss of expansive strain is a distinguished feature that differentiates the mechanism of air permeability changes in expansive and normal concrete. These findings suggest the possible improvement in the durability performance of expansive concrete in cases where the loss of its expansive strain can be controlled.