Journal
CEMENT & CONCRETE COMPOSITES
Volume 119, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.cemconcomp.2021.103995
Keywords
Gas permeability; Steady-state flow; Inner gas-pressure; Various gas; Concrete
Funding
- National Key Research and Development Program of China [2019YFC1904904]
- Natural Science Foundation of China [51878153, 51808189]
- Postgraduate Research & Practice Innovation Program of Jiangsu Province [KYCX19_0072]
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The apparent gas permeability of concrete is highly dependent on pore structure and gas medium. The effects of gas absorption from CO2 and O-2 on permeability are minimal, with O-2 having higher permeability than CO2. Significant differences in Knudson diffusion near the outlet-gas side of concrete contribute to deviations in permeability.
Apparent gas-permeability (k(a)) of concrete highly depends on pore-structure and medium. However, the effects of gas-medium on permeability have yet been investigated in depth. In this work, concrete with various water-to cement ratios and fly-ash/slag dosages is prepared for k(a) testing. Various gas-mediums (CO2 and O-2) are applied for analyzing their effects on the k(a). Meanwhile, pore-structure characteristic, inner gas-pressure, and gas absorption in concrete are observed for exploring permeation mechanism. The results illustrate that the narrowing pore-scale effect and surface-diffusion contribution derived from gas-absorption of CO2 and O-2 both have minor impacts on the k(a). The k(a) of O-2 (k(O2)) is higher than that of CO2 (k(CO2)) and their relative permeability (k(O2)/k(CO2)) ranges from 1.18 to 2.29. These deviations are mainly caused by significantly different Knudson diffusion occurring in the area near the concrete outlet-gas side (approximately 5%).
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