Abstract
Abstract Correlations between the air permeability coefficient and various pore structure indicators in cementitious materials were examined to determine the pore structure indicator that best evaluated air permeability using data from previous studies. In this study, the air permeability data from sufficiently dried specimens were selected and the effect of pressure on the air permeability was ignored. Among five pore structure indicators, the median and new threshold pore diameters obtained by percolation theory showed higher determination coefficients. The regression equation using the new threshold pore diameter better estimated the air permeability coefficient than the Katz–Thompson equation.
Highlights
The air permeability coefficient of concrete is important in evaluating the durability of concrete structures because the permeation of carbon dioxide and oxygen into concrete causes deterioration by carbonation and corrosion of reinforcement bars
The reported and calculated air permeability coefficients; total pore volumes; and median, critical, and threshold pore diameters are shown in Figs. 4–8 with approximation curves
Mercury is intruded to the pore size of 3 nm, but Mizuno et al [15] intruded mercury to that of 10 nm the actual total pore volume may be somewhat larger
Summary
The air permeability coefficient of concrete is important in evaluating the durability of concrete structures because the permeation of carbon dioxide and oxygen into concrete causes deterioration by carbonation and corrosion of reinforcement bars. Researchers have studied the relationship between the air permeability coefficient and the pore structures of concrete to understand the transportation mechanism of air and establish models that predict the air permeability of concrete; various characteristic indicators of the pore structure have been proposed. Among indicators characterising pore structure, the relationship between the total pore volume and air permeability has been reported the most extensively. The total pore volume is generally measured in one of three ways: calculation using the difference between the water-saturated and oven-dried weights [1,2,3], the maximum volume of cumulative intruded mercury in mercury intrusion porosimetry (MIP) [4,5,6], and image analysis of the area fraction of pores [7,8]. Some researchers set maximum and minimum pore sizes in calculating the total pore volume [9,10] without clear theoretical reason. As Diamond [11] noted, the pore size distribution obtained by MIP is not a true pore size distribution because of ink-bottle effects; the validity of using a total porosity with certain maximum and minimum pore sizes is unclear
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