Air-void characteristics and freeze-thaw cycling resistance of air-entrained concrete under low atmospheric pressure of highland regions

Under strict control of raw materials and mix proportions, field performance tests and specimen preparations for air-entrained concrete were conducted in Harbin and Lhasa, which are two regions with different atmospheric pressures. The air-void characteristics, compressive strength, and freeze-thaw cycling resistance of concrete under different atmospheric pressures were systematically investigated. Results indicated that, compared to normal atmospheric pressure, the air content of fresh concrete prepared under low atmospheric pressure decreased by 0.1 %–0.5 % (absolute value), with an air-void spacing factor of hardened concrete increase of 14–23 μm. Under the low atmospheric pressure, the compressive strength of concrete was more significantly influenced by air content, while the freeze-thaw cycling resistance was worse. These macroscopic performance differences were attributed to the impact of low atmospheric pressure on the air-void characteristics of concrete. This research provided valuable insights and guidance for enhancing the performance of air-entrained concrete in highland regions.