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Microstructure of Cement Paste and Mass Transfer of Gas through Concrete

Published online by Cambridge University Press:  25 February 2011

R. H. Mills*
Affiliation:
Department of Civil Engineering, University of Toronto, 35 St. George St., Toronto, Canada M5S 1A4
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Abstract

Gas 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.

Type
Research Article
Copyright
Copyright © Materials Research Society 1987

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References

REFERENCES

1. Mills, R.H., Gas and Water Permeability for Reactor Buildings, Report INFO 0188 (Atomic Energy Control Board, Ottawa, 1986).Google Scholar
2. Hilsdorf, H., Private communication.Google Scholar
3. Powers, T.C., in The Chemistry of Cement, edited by Taylor, H. (Academic Press, London 1972) p. 402.Google Scholar
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6. Mills, R.H., The permeability of Concrete for Reactor Containment Vessels, INFO 0111 (Atomic Energy Control Board, Ottawa 1983).Google Scholar