Pore Structure Characters and Oxygen Permeability Interpreted by Katz–Thompson Model of Fly Ash Concrete

The relationship between the characteristics of concrete pore structures and intrinsic permeability was investigated. The concrete pore structure incorporating fly ash was characterized by parameters including total porosity, pore size distribution (PSD), tortuosity, and characteristic pore sizes. The results indicate that: (1) there is a weak correlation between total porosity and critical pore size concerning oxygen permeability as interpreted by the Katz–Thompson model; (2) pores with diameters exceeding 100 nm serve as the primary tunnel for oxygen percolation in fly ash concrete; and (3) the porosity of pores larger than 100 nm and the average pore diameter exhibit the strongest correlation with oxygen permeability in fly ash concrete, as interpreted by the Katz–Thompson model.