Re: How much radon gets through a concrete slab?

[Dan Richards <richards@radonseal.com>]

Radsafers,



Thank you for the great guidance! Particularly to Steve Hand, Tom English,

Craig Reed, Matt Williamson, and Dave Lovett.



Water seepage through concrete is visible, but many people think that

concrete is a barrier to air and radon. But, unlike water, radon moves

through microscopic pores unhindered by surface tension and its atoms are

smaller than water molecules (50% ?). In addition, water drawn in by

capillary action carries dissolved radon.



In case others are interested in this subject:

----------------------------------------------



Craig Reed has advised

> Cinderblocks are often used for  basement walls and they are actually very

> porous.  Of course, anyone that has a wet cinderblock basement can attest to

> the fact that cinderblocks are porous because they can see water or water

> stains as ground water  moves through cinderblock.  What isn't obvious is

> how gas moves through the cinderblocks.  The fact is, one square foot of

> cinderblock has the equivalent air resistance of a hole the size of a

> quarter. 

What an illustrative comparison!



In addition to the list from Tom English, I was able to identify the

following relevant articles and abstracts on PubMed:



Health Phys 1994 Jul;67(1):53-9

Partitioning of 222Rn entry into a structure surrounded by soil.

Gadd MS, Borak TB.

"25% of the radon entered through the floor-wall joint and 75% through the

floor and walls. About 30% of the radon originated in the concrete."



Health Phys 1993 Jul;65(1):1-11

Characterization of 222Rn entry into a basement structure surrounded by

low-permeability soil.

Ward DC, Borak TB, Gadd MS.

"diffusion through the concrete walls and floor plus the floor-wall joint

accounted for more than 80% of the total 222Rn entry."



Health Phys 1993 Oct;65(4):375-85

Radon diffusion coefficients for residential concretes.

Rogers VC, Nielson KK, Holt RB, Snoddy R.

"Radon gas diffusion through concrete can be a significant mechanism for

radon entry into dwellings. Measurements of radon diffusion coefficients in

the pores of residential concretes ranged from 2.1 x 10(-8) m2 s-1 to 5.2 x

10(-7) m2 s-1."



Health Phys 1997 Oct;73(4):668-78    Related Articles, Books, LinkOut

Radon penetration of concrete slab cracks, joints, pipe penetrations, and

sealants.

Nielson KK, Rogers VC, Holt RB, Pugh TD, Grondzik WA, de Meijer RJ.

"Diffusion coefficients ... increased due to drying ... to an average of 2.0

x 10(-7) m2 s(-1)

Advective transport was negligible for the slabs (10(-16) m2 permeability)"



Health Phys 1995 Jun;68(6):832-4

Radon diffusion coefficients for aged residential concretes.

Rogers VC, Nielson KK, Holt RB.

"radon gas pore diffusion coefficient measurements ... ranged from 1.5 x

10(-7) m2 s-1 to 5.5 x 10(-7) m2 s-1 "



Health Phys 1982 Jul;43(1):65-71

Diffusion of radon through cracks in a concrete slab.

Landman KA.

"The rate of exhalation through a portion of a cracked slab is determined

and compared to the rate of exhalation from the same surface area of bare

soil. In a typical case, this ratio is approx. 0.25. This is about a 20-fold

increase to the ratio found when the concrete slab has no cracks. "



Rgds,

--------------

Dan Richards

RadonSeal

richards@radonseal.com

203 225-0366



> From: "Tom English" <englishtoma@HOTMAIL.COM>



> You may want to start with these articles.



> Health Phys 1997 Jan;72(1):153-5 Porosity trends in radon transport through

> concrete and consistency in defining diffusion coefficients. Rogers VC,

> Nielson KK.

> 

> Health Phys 1995 Jun;68(6):800-8  Laboratory measurements of the transport

> of radon gas through concrete samples.

> Renken KJ, Rosenberg T. Mechanical Engineering Department, University of

> Wisconsin-Milwaukee 53201-0784, USA.

> 

> Health Phys 1995 Jun;68(6):817-22 In-situ determination of the diffusion

> coefficient of 222Rn in concrete.

> Gadd MS, Borak TB. Department of Radiological Health Sciences, Colorado

> State University, Fort Collins 80523, USA.

> 

> Health Phys 1983 Aug;45(2):377-83 A time-dependent method for characterizing

> the diffusion of 222Rn in concrete.

> Zapalac GH.

> 

> Appl Radiat Isot 2001 Mar;54(3):467-73 Determination of 222Rn emanation

> fraction and diffusion coefficient in concrete using accumulation chambers

> and the influence of humidity and radium distribution. Cosma C, Dancea F,

> Jurcut T, Ristoiu D.

> 

> Health Phys 2001 Feb;80(2):151-6 Thermodiffusion in concrete slab as a

> driving force of indoor radon entry.

> Minkin L. Portland Community College, Physics Department, OR 97219, USA.

> lminkin@pcc.edu



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