Microstructure of Cement Paste and Mass Transfer of Gas through Concrete

Abstract

ABSTRACTGas flow through concrete may be modelled by a relationship:where D* is the specific permeability, N* is the number of unit pores per m2, and α, β and γ are experimental constants.A unit pore is defined by the hydraulic mean radius a* equal to the total porosity divided by the BET surface area. The value of a* is estimated from porosity and hydration parameters to lie between 1.6 and 2.8 nm for water-cement ratios from 0.42 to 0.77 and initial porosities from 0.292 to 0.150. Estimation of pore radius a from gas flow yielded values of a/a* varying from 72 to 6. There appears to be fair correlation between N* and D*, but it appears that flow passes through microcracks rather than the natural pore system.