Comparative analysis of air permeability between UHPC and epoxy-coated normal concrete for hyperloop tube structures

This study evaluates the air permeability of epoxy-coated normal concrete and ultra-high performance concrete (UHPC) for use in Hyperloop tube structures, where maintaining ultra-low air permeability is crucial to preserving the vacuum environment. While UHPC is recognized for its exceptionally low permeability due to its dense microstructure, this research explores epoxy-coated conventional concrete as a cost-effective alternative. Using a vacuum-based permeability test simulating Hyperloop's near-vacuum conditions, the study found that epoxy-coated concrete significantly reduced air permeability compared to uncoated concrete, with specimens coated on both sides approaching near-zero permeability. Although UHPC exhibited superior performance, the epoxy-coated concrete demonstrated air-tightness and was suitable for Hyperloop applications, offering a viable and economical alternative. These findings provide important insights for material selection, suggesting that epoxy-coated conventional concrete can effectively meet the stringent requirements for Hyperloop tube construction while balancing performance with cost-efficiency.