A modified approach for measuring the air permeability of ultra-high performance concrete (UHPC) under vacuum conditions

Abstract

This study proposes a novel test method of the air permeability measurement under extreme vacuum condition to examine the performance of materials for Hyperloop tubes. Tests on cement-based materials demonstrated that the developed test setup was effective in measuring air permeability in extreme vacuum conditions. The results show that ultra-high performance concrete (UHPC) has significantly lower air permeability (10–18 m2) in vacuum conditions than other cement-based materials (10–16 m2) due to its dense microstructure and reduced pore size, which were within the range of previous results (10-18-10-16 m2). The measured porosity results had a strong correlation with air permeability (R2 > 0.97), validating the suitability of the proposed method for measuring the air permeability of cement-based materials in vacuum conditions. These findings provide fundamental material properties for the design of Hyperloop tube structures.